JP5202267B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that optically reads an object to be imaged and generates an image signal.

  In general, an image reading apparatus applied to a copy machine, an image scanner, a facsimile, and the like includes a one-dimensional image sensor (line sensor) configured by arranging a plurality of image sensors (photoelectric conversion elements) in the main scanning direction. ing. At the time of image reading, reading in the main scanning direction by the one-dimensional imaging device and movement of the reading position in the sub-scanning direction (movement of the document or the optical system) are executed (for example, see Patent Documents 1 to 3).

  Patent Document 1 discloses an image reading device that forms an image of a whole document in the main scanning direction on a line sensor by a monocular reduction imaging lens. In this apparatus, the line sensor and the reduction imaging lens are fixed, and the entire original is scanned by moving a plurality of mirrors in the sub-scanning direction.

  Patent Document 2 discloses a contact-type image reading apparatus that forms an entire image in the main scanning direction of an original on a photoelectric conversion element through a rod lens array at an equal magnification.

  In Patent Document 3, scanners are respectively arranged corresponding to two platens (document tables) arranged at a predetermined angle, a book is set in an open state, and two spread pages are simultaneously or alternately arranged. An image reading apparatus is disclosed which can be read by the user.

Japanese Patent Laid-Open No. 10-308852 (FIG. 1, paragraphs 0006 and 0007) Japanese Patent Application Laid-Open No. 8-204899 (FIG. 1, summary) JP 2000-165608 A (FIG. 1, FIG. 2, paragraph 0009)

  The device described in Patent Document 1 is a device having a large depth of field, but employs an optical system that moves a plurality of mirrors so as not to change the optical path length from the original to the reduction imaging lens. There is a problem that the configuration becomes large and complicated, and the apparatus becomes expensive.

  Although the apparatus described in Patent Document 2 has the advantage of being small and low-cost, there are problems that the depth of field is small and chromatic aberration is large.

  In the apparatus described in Patent Document 3, since the document table has a shape corresponding to the double-page spread shape of the book, a document that cannot be matched with the shape of the document table cannot be read. There is a problem that a troublesome work to bend and adhere to fit to the need.

  In addition, the apparatuses described in Patent Documents 1 to 3 have a problem that a generated image is distorted when the position of the object to be imaged in the depth direction is not constant.

  Therefore, the present invention has been made to solve the above-described problems of the prior art, and the object thereof is to simplify and miniaturize the configuration of the optical system, and images are captured by a plurality of image sensor sections by image signal processing. It is possible to appropriately synthesize images of a plurality of imaged areas, and to correct a distorted synthesized image generated when the position of the imaged area of the object to be imaged in the depth direction is not constant to a synthesized image without distortion. An object of the present invention is to provide an image reading apparatus.

The image reading apparatus according to the present invention determines the position of an object to be imaged in a depth direction perpendicular to both the main scanning direction and the sub-scanning direction, and moves the object to be imaged from a predetermined in-focus position or the in-focus position to the depth. A plurality of first images are formed by condensing a plurality of first lights from a plurality of first imaging regions on the imaging object and a positioning unit placed at a position shifted in the direction A plurality of first imaging optical units to be arranged, and a plurality of second imaging regions arranged alternately with the plurality of first imaging regions in the main scanning direction on the imaging object, From the plurality of second image pickup areas in which the first image pickup area and the second image pickup area that match each other partially overlap in the main scanning direction, the plurality of first lights in the sub scanning direction By collecting a plurality of second lights traveling in different directions, a plurality of second lights are collected. A plurality of second imaging optical units that form images, and a plurality of first imaging elements that are arranged corresponding to the plurality of first imaging optical units and that capture the plurality of first images. A plurality of second imaging element units that are arranged corresponding to the plurality of second imaging optical units and that capture the plurality of second images, and the plurality of first imaging element units, A storage unit that temporarily stores image information acquired by the plurality of second image sensor units, and an image processing unit that generates a composite image by combining the stored image information, each of the plurality of first imaging optical unit, configured to focus images of the placed focus position the object to be imaged, Ru is formed on the imaging surface of the corresponding first image sensor unit It is formed, if the each of the plurality of second imaging optical unit, the object to be imaged placed in the focus position An image, a configuration in which Ru is formed on the imaging surface of the corresponding second image pickup device unit, the image processing unit, the first image sensor portion of the plurality of first image sensor unit wherein a plurality of second second image sensor portion of the image pickup device unit and, adjacent said first of said plurality of first imaged region and the plurality of second imaged region for said set of each of said second image pickup device unit and the first image sensor unit for each image the second imaged region and the imaged region, the first image sensor portion is imaged 1 An image matching region in which the image of the first region of interest in the second image and the image of the second region of interest in the second image captured by the second image sensor unit are detected, and Based on the position of the image matching area in one image and the position of the image matching area in the second image. And combining position detecting means for determining a combining position for combining the first image and the second image, and combining the first image and the second image at the combining position. An image composition means for generating an image, and an image that is a difference between a position in the sub-scanning direction of the image matching area in the first image and a position in the sub-scanning direction of the image matching area in the second image A distance calculation unit that calculates a distance in the depth direction of an area where the first image pickup area and the second image pickup area overlap from the in-focus position using the shift amount, and the distance calculation means Image correction means for estimating the shape of the object to be imaged from the measured distance and correcting distortion of the composite image based on the shape estimation result.

  According to the present invention, it is possible to obtain an effect that simplification and downsizing of the configuration of the optical system of the image reading apparatus can be realized. Further, according to the present invention, it is possible to appropriately combine images of a plurality of imaging regions imaged by a plurality of imaging element units by image signal processing, and the position of the imaging region of the imaging object in the depth direction is not constant Thus, it is possible to obtain an effect that the generated composite image with distortion can be corrected to a composite image without distortion generated when the position of the imaging region of the imaging target in the depth direction is constant. .

Embodiment 1 FIG.
FIG. 1 is a diagram schematically showing a configuration of an image reading apparatus 100 according to Embodiment 1 of the present invention. FIG. 1 includes a perspective view (left side) schematically showing the configuration of the optical system of the image reading apparatus 100 and a block diagram (right side) schematically showing the configuration of the image signal processing system. In the following description, an XYZ orthogonal coordinate system is used. Place the X-axis in the main scanning direction D _X in the reading of the image, place the Y-axis in the sub-scanning direction D _Y perpendicular to the main scanning direction D _X, perpendicular to both the main scanning direction D _X and the subscanning direction D _Y placing the Z-axis in the depth direction _{D Z.} Therefore, the main scanning direction D _X is also referred to as “X-axis direction”, the sub-scanning direction D _Y is also referred to as “Y-axis direction”, and the depth direction D _Z is also referred to as “Z-axis direction”. In the following description, the Z-axis direction is the thickness direction of the image reading apparatus.

  As shown in FIG. 1, the image reading apparatus 100 according to the first embodiment includes an imaging optical system 101, an illumination light source 102, a top plate 103, and a plurality of imaging element units 141 arranged on a substrate 104. , 142,..., 148, a memory 105, and an image processing unit 106.

The top plate 103 is a transparent document placing member, for example, a glass plate, on which a document (not shown in FIG. 1), which is an example of an object to be imaged (object), is placed. The top plate 103, the position in the depth direction D _Z of the document (i.e., the distance from the imaging optical system 101 to the imaged area of the document) serves as a positioning portion that can be determined. The top plate 103, the document is placed at a position shifted in the depth direction _{D Z} from the position or the upper surface 103a of the upper surface 103a of the top plate 103. In the first embodiment, the top surface 103a of the top plate 103 is set as a focus position (also referred to as “just focus position”), and the imaged areas 31, 32,. When the image is in the position, the image formed on the image sensor elements 141, 142,..., 148 from the imaged areas 31, 32,. Is also called.) The top plate 103 functions as a positioning unit for the object to be imaged and is not limited to the glass plate as long as it can capture the imaged areas 31, 32,. It may be a means. In addition to the manuscript on which text, a document, a photograph, and the like are displayed, the object to be imaged includes everything that can be a target for reading an image, such as a banknote or a human finger. The image reading apparatus 100 can be applied to, for example, a copying machine, a printer, a bill authenticity determination device, an image scanner for converting a document into an electronic file, a facsimile, and the like.

The illumination light source 102 is composed of, for example, a fluorescent lamp or LED. The illumination light source 102 is disposed, for example, at a position below the top plate 103 so as not to interfere with reading of the imaged areas 31, 32,. The illumination light source 102 irradiates the imaged areas 31, 32,. The shape of the illumination light source 102 is not limited to the long shape as shown in FIG. 1, and may be another shape. Further, in FIG. 1, the illumination light source 102, a case which is arranged only on one side of the sub-scanning direction D _Y of the imaging optical system 101, the sub-scan of the imaging optical system 101 to the illumination light source it may be disposed on both sides of the direction D _Y. Furthermore, when the imaged areas 31, 32,..., 38 of the document can be illuminated sufficiently brightly by external light or the like, the illumination light source 102 may not be turned on. A configuration without it is also possible.

The imaging optical system 101 includes a plurality of imaging optical units 111, 112,..., 118 corresponding to the plurality of imaging element units 141, 142,. Each of the imaging optical units 111, 112,..., 118 is a functionally independent optical means. In the first embodiment, the plurality of imaging optical units 111, 112,..., 118 are configured by cylindrical optical cells arranged in a staggered manner on a plane parallel to the XY plane. In the first embodiment, a plurality of image forming optical unit 111, 112 ..., of 118, the odd-numbered row of the imaging optical section 111 and 113 arranged in the main scanning direction _{D X,} ..., 117 the first group (first _column) image-forming optical unit belonging to _{G 11} (first imaging optical section) and said even-numbered row of the imaging optical section 112, 114 arranged in the main scanning direction _{D X,} ..., and 118, referred to as a second group forming optical unit belonging to the (second _{column) G 12} (second imaging optical unit). The first imaging optical units 111, 113,..., 117 belonging to the first group G ₁₁ are the first imaging optical units 111, 113,. The chief rays of the first light traveling toward are parallel to each other. That is, the first imaging optical section 111 and 113 belonging to the first group _{G 11,} ..., 117 have their optical axes 111a, 113a, ..., 117a are configured so as to be parallel to each other. The second imaging optical unit 112, 114 belonging to the second group _{G 12,} ..., 118 are imaged regions 32 and 34 of the document, ..., and 38 second imaging optical unit 112, ... , 118 are configured such that the chief rays of the second light directed to 118 are parallel to each other. That is, the second imaging optical unit 112, 114 belonging to the second group _{G 12,} ..., 118, their optical axes 112a, 114a, ..., 118a are configured so as to be parallel to each other. However, the present invention includes a first imaging optical section 111 and 113 belonging to the first group _{G 11,} ..., 117 of the optical axis 111a, 113a, ..., if 117a is not parallel to each other, or the second group _{G 12} .., 118 of the second imaging optical units 112, 114,..., 118 belonging to the above can be applied even when the optical axes 112a, 114a,. For example, if the direction is a known optical axes of the imaging optical section, the first imaging optical section 111 and 113 belonging to the first group _{G 11,} ..., 117 of the optical axis 111a, 113a, ..., 117a are parallel without necessarily, the second imaging optical unit 112, 114 belonging to the second group _{G 12,} ..., 118 of the optical axis 112a, 114a, ..., 118a need not be parallel.

.., 148 are arranged on the substrate 104 so as to correspond to the imaging optical units 111, 112,. The imaging element unit 141, 143, ..., 147, the first imaging optical section 111 and 113 belonging to the first group _{G 11,} ..., are arranged so as to correspond to the 117, the image pickup device 142, 144, ..., 148, the second imaging optical unit 112, 114 belonging to the second group _{G 12,} ..., are arranged so as to correspond to 118. The imaging elements 141, 142, ..., 148, for example, constituted by double rows arranged light receiving element made of CCD in the main scanning direction _{D X} and the subscanning direction _{D Y.} .., 148 are incident on the image sensor units 141, 142,..., 148 from the original 70 through the imaging optical units 111, 112,.

In FIG. 1, the imaging optical system 101, the first imaging optical section 111 and 113 belonging to the first group _{G 11,} ..., 117 and second imaging optical section belonging to the second group _{G 12} 112, ..., a case has been described consisting of 118, the present invention is not limited to such embodiment, the imaging optical system 101, to a device which is arranged three rows above in the sub-scanning direction D _Y Applicable.

  FIG. 1 shows a case where the plurality of imaging optical units 111, 112,..., 118 are arranged in a staggered pattern on a plane parallel to the XY plane. The arrangement of the plurality of imaging optical units is not limited, and may be an arrangement other than a staggered pattern as long as adjacent imaging areas have an overlapping area.

Furthermore, in FIG. 1, the imaging optical system 101 includes four first imaging optical units 111, 113,..., 117 and four second imaging optical units 112, 114,. a case has been described including, the invention is not limited to such embodiment, the imaging optical system 101, unlike the position and position in the sub-scanning direction D _Y in the main scanning direction D _X, one of the imaging region The present invention is applicable to an apparatus including at least one first imaging optical unit and at least one second imaging optical unit that overlap each other. Further, the arrangement and the number of the imaging element units can be changed according to the arrangement and the number of the imaging optical units.

  The first imaging optical units 111, 113,..., 117 capture the focused image of the object to be imaged placed at the in-focus position, and the imaging surfaces of the corresponding first imaging element units 141, 143,. It is configured to form an image on top. The second imaging optical units 112, 114,..., 118 display the in-focus image of the object to be imaged placed at the in-focus position and the imaging surfaces of the corresponding second image sensor units 142, 144,. It is configured to form an image on top.

In FIG. 1, imaged regions 31, 32,..., 38 are surfaces (view range) read by the image sensor units 141, 142,. a plurality of areas arranged in the scanning direction D _X. The image reading apparatus 100 in the main scanning direction _{D X} imaged regions 31 and 32 of the document on the top plate 103 along the, ..., reads the 38 images, each main scanning direction _{D X} of the read is completed, the sub the reading position is relatively moved in the scanning direction D _Y. Moving the reading position of the sub-scanning direction D _Y can be carried out either by moving the optical system including the mobile or the imaging optical system 101 of the document. In FIG. 1, the imaged regions 31 and 32, ..., 38 have been shown when arranged in a row in the main scanning direction D _X, the present invention is not limited to such embodiments, adjacent the imaged regions 31 and 32 to, ..., as long as embodiments comprising a region 38 between overlaps in the main scanning direction D _X, as aspects which position in the sub-scanning direction D _Y between the imaged area adjacent are shifted It can be applied to other embodiments. In addition, the number of the imaged regions 31, 32,..., 38 is not limited to eight, and the number of the imaging optical units 111, 112, ..., 118 and the number of the imaging element units 141, 142,. It can be changed accordingly.

  The memory 105 is a storage unit that temporarily stores image information acquired by the first image sensor units 141, 143, ..., 147 and the second image sensor units 142, 144, ..., 148. The image processing unit 106 is, for example, an arithmetic processing circuit that operates in accordance with software. The image processing unit 106 combines image information stored in the memory 105 (that is, combines images captured by the image sensor units). (Also referred to as “combined image”). In FIG. 1, the memory 105 and the image processing unit 106 are shown as separate configurations, but these may be integrated on the same circuit board, for example.

The image processing unit 106 includes a combined position detection unit 106a that performs arithmetic processing for detecting a combined position of images captured by the image sensor units 141, 142,..., 148, and a combined position of the captured images. From the image synthesizing means 106b for performing arithmetic processing for combining (synthesizing) the images picked up by the image pickup device portions 141, 142,... a distance calculation unit 106c for performing arithmetic processing for calculating the distance in the depth direction D _Z to a document, and an image correcting unit 106d for performing arithmetic processing for correcting the distortion of the synthesized image using the calculated distance Have. The image correcting unit 106d performs arithmetic processing for reducing blur as necessary. In the present application, “... Means” may be either a means for executing a certain function by an electric circuit or a means for executing a certain function by software.

The combined position detection unit 106a includes a plurality of first imaging element units 111, 113,..., 117 and a plurality of second imaging element units 112, 114,. And a second imaged area (for example, the first imaged area 31 and the second imaged area 32, the second imaged area 32 and the first imaged area 33, and the first imaged area) 33 and the second imaged area 34), for example, a set of the first image sensor unit and the second image sensor unit (for example, a set of the first image sensor unit 141 and the second image sensor unit 142) , The coupling position is determined for each of the second imaging element unit 142 and the first imaging element unit 143, and the first imaging element unit 143 and the second imaging element unit 144). Specifically, the coupling position detection unit 106a includes an image of the first region of interest R _A (shown in FIG. 10 described later) and the second imaging in the first image captured by the first imaging element unit. An image matching region that matches an image of a second region of interest R _B (shown in FIG. 10 described later) in the second image captured by the element unit is detected, and the position of the image matching region in the first image is detected. And a coupling position for coupling the first image and the second image is determined based on the position of the image matching region in the second image.

  The image synthesizing unit 106b combines the first image and the second image at the coupling position determined by the coupling position detection unit 106a to generate a synthesized image.

Distance calculating unit 106c from the image shift amount is the difference between the position in the sub-scanning direction D _Y of the image matching area in the sub-scanning direction D _Y position and a second image of the image matching area in the first image, if (in the embodiment 1, the upper surface 103a of the top plate 103) focus position to calculate the distance in the depth direction D _Z from to the first of the imaging area or the second of the imaging region.

  The image correcting unit 106d estimates the shape of the object to be imaged using the distance calculated by the distance calculating unit 106c, and performs processing for correcting the distortion of the composite image based on the shape estimation result. That is, the image correcting unit 106d uses a distortion-generated composite image generated when the position in the depth direction of the imaged area of the object to be imaged is not constant, and the position in the depth direction of the imaged area of the object to be imaged is constant. It can be corrected to a composite image without distortion generated in some cases.

  In addition to the process of correcting the distortion, the image correcting unit 106d can also perform a process of reducing the blur of the synthesized image synthesized by the image synthesizing unit 106b. The process for reducing the blur of the composite image is, for example, a process for sharpening the composite image.

When it is desired to correct the composite image with high accuracy, it is desirable to calculate the distance by the distance calculation means 106c at many points. Further, in order to reduce the load of signal processing by the image processing unit 106, the distance calculation by the distance calculation unit 106c may be performed at a small point. The distance calculating unit 106c is holding an image shift amount at the time when the position of the first of the imaging region adjacent and depth direction D _Z of the second imaged region coincides with the focus position as a reference value for image deviation And a means for calculating the distance ΔZ based on the difference between the image shift amount and the held reference value. Furthermore, the distance calculation means 106c stores the difference between the image deviation amount and the stored reference value in advance by the means for storing the change amount of the distance ΔZ when the image deviation amount is changed by a certain amount. Means for calculating a distance conversion coefficient which is a value divided by the amount of change, and the image correction means 106d corrects the distortion of the composite image using the calculated distance conversion coefficient (and blurs the image as necessary). It is also possible to configure to perform image processing that reduces the image quality.

2A and 2B are a schematic cross-sectional view of the optical system of the image reading apparatus 100 according to Embodiment 1 as viewed in the direction of line S _2a -S _{2a in} FIG. 1, and S _2b -S in FIG. It is a schematic sectional view seen in the _2b line direction. 2A and 2B, the main scanning direction D _X (X axis) is the horizontal direction, the depth direction D _Z (Z axis) is the vertical direction, and the sub scanning direction (Y axis) is from the front of the page. The direction is perpendicular to the page. In FIG. 2 (a), the first imaging optical section 111 and 113 belonging to the first group _{G 11,} ..., the main optical path of the first light passing through the 117 is shown. Further, in FIG. 2 (b), the main optical path of the second light passing through the second imaging optical unit 112, 114, 116 belonging to the second group _{G 12} is shown.

3 and 4 are schematic cross-sectional views of the optical system of the image reading apparatus 100 according to Embodiment 1 as viewed in the direction of the line S ₃ -S ₃ in FIG. 3 and 4, the sub-scanning direction D _Y (Y-axis) is the horizontal direction, the depth direction D _Z (Z-axis) is the vertical direction, and the main scanning direction (X-axis) is perpendicular to the front from the page. The direction. In FIG. 3, the document 70 is in close contact with the upper surface 103 a (the in-focus position in the first embodiment) of the top plate 103, and is focused on a point on the imaging surface of the imaging element unit 143 belonging to the first group G _11. The main optical path when the image is formed is shown. Further, in FIG. 4, in a first document position 71 where the document 70 is separated by a distance ΔZ from the upper surface 103a of the top plate 103, if a point on the imaging surface of the imaging element 144 belonging to the second group _{G 12} The main optical path when no focal image is formed is shown.

As shown in FIG. 3, in the first embodiment, the optical axis AX ₁ of the first imaging optical unit 113 is inclined with respect to the normal 103 b of the upper surface 103 a of the top plate 103, and the top plate 103 Passes through the position F _a1 on the upper surface 103a. The other first imaging optical units 111, 115, and 117 are arranged in the same manner as the first imaging optical unit 113. Further, as shown in FIG. 3, the optical axis AX ₂ of the second imaging optical unit 114 with respect to the perpendicular 103b, are inclined to the side opposite to the optical axis AX _1, the upper surface 103a of the top plate 103 It passes through the upper position F _a2 . The other second imaging optical units 112, 116, and 118 are arranged in the same manner as the second imaging optical unit 114.

  As can be understood from FIGS. 2A and 2B, each of the imaging optical units 111, 112,..., 118 (imaging optical unit 118 is not shown in FIG. 2B) has the same configuration. doing. Each of the imaging optical units 111, 112,..., 118 includes a first condenser lens 152 as a first optical element, an aperture 153 as a stop, and a holding member 155 that holds them.

First condenser lens 152, an imaging optical unit 111, ..., 118 of the optical axis AX ₁ or AX ₂ imaging optical portions 111 and 112 in the direction (shown in FIGS. 3 and 4), ..., 118 It is arrange | positioned in the approximate center part. The 1st condensing lens 152 is comprised by the convex lens, for example. Aperture 153, an imaging optical unit 111, ..., a first condensing lens 152 on either side of the first condenser lens 152 is supported in a direction perpendicular to the optical axis AX ₁ or AX ₂ in 118, the first current An opening is provided in a region corresponding to the central portion of the optical lens 152. Therefore, the light from the imaging regions 31, 32,..., 38 enters the first condenser lens 152 through the opening of the aperture 153, is emitted from the first condenser lens 152, and is image sensor elements 141, 142. ,..., 148 converge on the imaging surface or in the vicinity thereof.

  As shown in FIGS. 2A and 2B, in the first embodiment, document images passing through the imaging optical units 111, 112,. ,..., 148 is formed as a reverse image. The imaging magnification at this time may be larger than 1 (that is, enlarged), smaller than 1 (that is, reduced), or 1 (that is, equal magnification). By setting the magnification to the same magnification or in the vicinity thereof, an image sensor having a resolution that is generally distributed as the imaging element units 141, 142,.

Hereinafter, the operation of the image reading apparatus 100 when the document 70 is a book will be described with reference to FIGS. 2A and 2B, FIG. 3, and FIG. 4. 2 (a) and (b) the distance from the upper surface 103a of the top plate 103 to the imaged area of the document 70 is when the shown to vary depending on the position in the main scanning direction D _X . For example, as shown in FIGS. 3 and 4, the upper surface 103 a of the top plate 103 in a region where the reading ranges (imaged regions) of the first imaging optical unit 113 and the second imaging optical unit 114 overlap. The distance from the document 70 to the document 70 is ΔZ, and the position of the document 70 is a first document position 71. In the first embodiment, a case will be described in which each of the imaging optical units 111, 112,.

  When the image blur correction process by the image processing unit 106 is not performed, the depth of field of the image reading apparatus 100 is almost determined by the depth of field of the imaging optical units 111, 112,. . The depth of field of the imaging optical units 111, 112,..., 118 is determined by the design of the internal optical system. The depth of field is substantially determined by the F value of the optical system. In order to increase the field of view of one imaging optical unit, it is necessary to sufficiently reduce the aberration by making the lens included in the imaging optical unit an aspherical shape or using a plurality of lenses. . Usually, when a resolution of 600 dpi is required, a depth of field of about ± 1 mm is obtained when the F value is 10, and a depth of field of about ± 2 mm is obtained when the F value is 20. Note that the depth of field refers to the width (depth) of an area that can be seen as if the image of the object imaged by the imaging optical system is in focus (that is, there is no blur). That is. In a strict sense, the position of the image of the object imaged by the imaging optical system is in focus (that is, there is no blur), but is the in-focus position, but within the range of the depth of field. When there is an imaged object, the blurred image is within the allowable range.

2A and 2B and FIG. 3 illustrate a case where a focused image is formed on the imaging element portion when the document 70 is positioned on the upper surface 103a of the top plate 103. FIG. However, the present invention is not limited to such an embodiment. For example, in an optical system having an F value of 10, the top plate 103 can be arranged so that a predetermined position shifted from the top surface 103a of the top plate 103, for example, a position 1 mm above the top surface 103a, is an in-focus position. . According to this structure, it is possible to effectively utilize the depth of field of ± 1mm around the focus position in the depth direction D _Z.

In the following, the imaging optical units 111, 112,..., 118 have an F value of 10, the imaging optical units 111, 112,. A case where the in-focus position is on 103a will be described. In this case, the depth of field by only the optical system is a top 103a position from the depth direction _D imaged _Z optical portions 111 and 112 of the top plate 103, ..., range up to the position of 1mm distant direction from 118.

As shown in FIG. 3, when the top surface 103 a of the top plate 103 is in the in-focus position, the imaged area of the document 70 that is in close contact with the top surface 103 a of the top plate 103 (also referred to as “document surface”). Is condensed on the imaging surface of the imaging element unit 143, and the image is not blurred (that is, a focused image is formed). As shown in FIG. 4, when the upper surface 103 a of the top plate 103 is the in-focus position, the imaged region of the original 70 is at the first original position 71 that is shifted from the upper surface 103 a of the top plate 103 by a distance ΔZ. The light incident on the imaging optical unit 113 from the imaging region of the original 70 is not condensed on the light incident surface of the imaging element unit 143, and the image is blurred (that is, the focused image is not imaged). If the distance ΔZ is within 1mm in depth direction _{D Z} between the upper surface 103a and the first original position 71 of the top plate 103, the blur of the image is within the allowable range. Here, being within the permissible range means that the radius of the point image from the first document position 71 is within the radius of the permissible circle of confusion.

  On the other hand, if the distance ΔZ exceeds 1 mm, the spread of the point image (point image distribution function) exceeds the radius of the allowable circle of confusion, and the target resolution cannot be achieved. An image formed on the original 70 placed at a position where the distance ΔZ exceeds 1 mm is a blurred image, but an image (original image) without blur is generated (restored) from the blurred image by image processing. An image processing technique for correcting image blur is a known technique. When performing image processing for image blur correction, if the point spread function of blur is known in advance, image blur can be reduced more appropriately than when it is unknown.

Point spread function is determined uniquely by the position in the depth direction D _Z of the document 70. The point spread function can be actually measured or can be obtained by calculation using a ray tracing simulation. If the distance ΔZ from the upper surface 103a of the top plate 103 to the document 70 (that is, the distance from the in-focus position to the document) is known, the point spread function is known, and the image blur correction process is facilitated. If the resolution of the image after image processing is improved by the image blur correction process, the image blur may occur even when the object to be imaged is arranged at a position exceeding the depth of field of 1 mm determined by the optical system. It is possible to obtain an image that does not exist (to be precise, it feels like there is no blurring of the image). In other words, if the resolution of the image after image processing is improved by the image blur correction process, the substantial depth of field of the image reading apparatus 100 can be increased.

In the image reading apparatus 100 according to the first embodiment, the imaging optical section belonging to the first group G ₁₁ and an image-forming optical unit belonging to the second group G _12, an imaging optical unit adjacent to each other, for example, when restoring the image obtained by the imaging optical unit 111 and the imaging optical section 112, the shift amount when combining the two images in the sub-scanning direction D _Y, from the upper surface 103a of the top plate 103 first it is possible to calculate the distance in the depth direction D _Z to the original position 71.

FIG. 5 is an enlarged view showing the vicinity of the top plate 103 of the image reading apparatus 100 according to the first embodiment. In FIG. 5, the sub-scanning direction D _Y (Y-axis) is the horizontal direction, the depth direction D _Z (Z-axis) is the vertical direction, and the main scanning direction (X-axis) is the direction heading vertically from the page to the front. . The optical axis AX ₁ is an optical axis of the first imaging optical unit 113 belonging to the first group _{G 11,} the optical axis AX _2, the light of the second imaging optical unit 114 belonging to the second group _{G 12} Is the axis. As shown in FIG. 5, the two optical axes AX ₁ and AX ₂ intersect at the upper surface 103 a of the top plate 103. However, the two optical axes AX ₁ and AX ₂ do not necessarily need to intersect at the upper surface 103 a of the top plate 103. The imaging optical system 101 may be configured such that the two optical axes AX ₁ and AX ₂ intersect at a position that is a predetermined distance upward from the upper surface 103 a of the top plate 103. Further, the imaging optical system 101 may be configured such that the two optical axes AX ₁ and AX ₂ intersect below the upper surface 103a of the top plate 103. The optical axes AX ₁ and AX ₂ are inclined in the opposite direction with respect to the vertical line 103b of the upper surface 103a of the top plate 103 with the vertical line 103b interposed therebetween, and have a predetermined angle with respect to the vertical line 103b of the upper surface 103a of the top plate 103. ± θ tilted. However, if the tilt angles of the optical axes AX ₁ and AX ₂ are known, the tilt angle of the optical axis AX _{1 and} the tilt angle of the optical axis AX ₂ can be different.

In the case of Figure 5, the upper surface 103a of the top plate 103, but the two intervals in the sub-scanning direction _{D Y} of the optical axis _AX 1, AX ₂ is zero, in the depth direction _{D Z} from the upper surface 103a by a distance [Delta] Z ₁ distance [Delta] Y ₁ in the sub-scanning direction _{D Y} of the two light at the first document position 71 spaced axes _AX 1, AX ₂ can be calculated by the following equation.
ΔY ₁ = 2 × ΔZ ₁ × tan θ
When the imaged area of the original 70 on the upper surface 103a of the top plate 103 is located, the position deviation in the sub-scanning direction D _Y of each image captured by the image sensor unit 143 and the image sensor unit 144 is zero , when the imaged region of the document 70 is present in the first document position 71, position deviation [Delta] Y ₁ in the sub-scanning direction D _Y of each image captured by the image sensor unit 143 and the image pickup device 144 , Value greater than zero. The interval [Delta] Y ₂ in the sub-scanning direction _{D Y} depth document 70 from the upper surface 103a of the top plate 103 the direction _{D Z} to a distance [Delta] Z ₂ of the two in the second original position 72 at a distance of the optical axis _AX 1, AX ₂ is Can be calculated by the following equation.
ΔY ₂ = 2 × ΔZ ₂ × tan θ

In the first embodiment, the image processing unit 106, when restoring an image, includes the shift amount ΔY ₁ (or the above-described interval) for each cell boundary in the main scanning direction and for each arbitrary line in the sub-scanning direction. ΔY ₂ ) is calculated, and a distance ΔZ ₁ from the top surface 103 a of the top plate 103 to the first document position 71 (or a distance ΔZ _{2 to} the second document position 72) is calculated. Further, the image processing unit 106 performs correction processing on the combined image that is shifted and connected according to the deviation amount based on the document shape estimated from the calculated distance ΔZ ₁ (or ΔZ ₂ or the like). . Thereby, the image reading apparatus 100 according to the first embodiment has an effect that image distortion can be corrected without adding a special mechanism. In the first embodiment, the image processing unit 106 can also perform image blur correction processing based on the calculated distance ΔZ ₁ (or ΔZ ₂ or the like). It has an effect that a substantially large depth of field can be realized exceeding the depth of field (for example, 1 mm) of the.

FIG. 6 is a diagram illustrating a simplified configuration of the image processing apparatus 100 according to the first embodiment. 6, the device having two first imaging optical section C0, C2 belonging to the first group _{G 11,} two second imaging optical unit C1, C3 belonging to the second group _{G 12} It is shown. Although not shown in FIG. 6, an imaging element unit is provided on the substrate 104 at a position corresponding to the first imaging optical units C0 and C2, and the second imaging optical units C1 and C3. Is provided at a position corresponding to.

FIG. 7 is a flowchart showing processing by the image processing apparatus 100 according to the first embodiment. As shown in FIG. 7, in the image processing apparatus 100 according to the first embodiment, the imaging optical unit C0, ..., and reading in the main scanning direction D _X of the image by the imaging device unit through C3, an imaging optical unit C0, ..., C3 and movement in the sub-scanning direction _{D Y} of the image pickup device unit and the (scan) is performed, the image of the document 70 is read (step ST1). The read original image is stored in a memory (for example, a frame memory) 105 after finishing black correction and white correction by a processing circuit (not shown) (step ST2). In the image processing unit 106, each image read by the imaging element unit through the imaging optical units C0,..., C3 is a reverse image, so the image processing unit 106 uses the read image as the original 70. The rearrangement process is performed so as to be oriented (step ST3).

  Next, the coupling position detection unit 106a of the image processing unit 106 forms an image by the adjacent imaging optical unit and combines two images from each image read by the imaging element unit corresponding to the adjacent imaging optical unit. A process for detecting a coupling position, which is an imaged position, is performed for each fixed line interval or every line, and the coupling position is detected (step ST4). Next, the image composition unit 106b of the image processing unit 106 combines the images at the detected combining position (step ST5). At that time, it is desirable to perform a smoothing process so that the joints are not conspicuous in the joint positions (joints) of the images.

  Next, the distance calculation unit 106c of the image processing unit 106 detects the object 70 of the document 70 from the in-focus position based on the information regarding the coupling position between the images imaged by the detected adjacent imaging optical unit and read by the imaging element unit. A distance ΔZ to the imaging region is calculated (step ST6). Next, the shape of the imaged region of the object to be imaged is estimated from the distance calculated by the distance calculating unit 106c, and a process of correcting the distortion of the composite image based on the shape estimation result is performed (step ST7). The document image processed in this way is output as a reading result.

  In the above description, the case where the image processing unit 106 performs the rearrangement process (step ST3) on the data stored in the memory 105 has been described. However, the address for reading data from the memory 105 is changed. The rearrangement process may be performed by changing the data order. The rearrangement process (step ST3) stores data for one line in the line memory when reading data from the image sensor unit, and outputs the data with a one-line delay in order from the last stored data. It is also possible to change the data order. Thus, it is possible not to perform data rearrangement processing in the memory 105. Further, the rearrangement process (step ST3) may output the restored image sequentially using a memory having the minimum number of lines necessary for the rearrangement process. Therefore, the memory 105 is not limited to a frame memory.

FIG. 8 is a diagram illustrating a case where the imaged region of the document 70 exists at the in-focus position in the image reading apparatus 100 according to the first embodiment. FIG. 9 is a diagram showing images 80,..., 83 and a composite image 84 obtained from the corresponding imaging element units through the imaging optical units C0,. The image combining process (the processes of steps ST4 and ST5 in FIG. 7) will be described with reference to FIGS. An imaging optical unit C0, ..., the image pickup device section corresponding to C3 and it is arranged such that their field of view (the imaged region to be read by the image pickup device unit) partially overlap each other in the main scanning direction D _X ing. For this reason, the same image is duplicated and included in the edge part of the image acquired by the adjacent image sensor part among the images 80, 81, 82, 83 imaged by the respective image sensor parts. The image processing unit 106 determines a position where the images match from the overlappingly read regions, for example, the region 80b and the region 81a, the region 81b and the region 82a, the region 82b and the region 83a, and the region 83b and the region 84a. To detect. Then, based on the detection result, the image processing unit 106 determines a coupling position for joining the images acquired by the images formed by the adjacent imaging optical units, and the images 80, 81, 82 at the coupling position. , 83 are combined to generate (restore) a composite image 84. Detection of the position of the image are matched, for example, the degree of coincidence of the image in the sub-scanning direction D _Y every predetermined line intervals (e.g., inconsistency d, i.e., the difference) is performed by detecting the. In the following description, a case will be described in which the mismatch degree d for detecting the position where the images match is detected for each line.

FIG. 10 is a diagram for explaining how to obtain the image matching area in the image reading apparatus 100 according to the first embodiment. First, as shown in FIG. 10, the image processing unit 106 selects the pixel data of the line L ₀ from the image obtained by the imaging device section through an imaging optical section C0. The region of pixels _{N A} row × _{M A} sequence around the selected line _{L 0} on the pixel _(x 0, _{y 0)} and the region of interest _{R A.} The image processing unit 106 creates vector data A = {a ₀ , a ₁ ,..., A _n } from the luminance values of the images included in the region of interest _RA . Similarly, the image processing unit 106 selects an arbitrary pixel (x ₁ , y ₁ ) from the image obtained by the imaging element unit through the imaging optical unit C1 adjacent to the imaging optical unit C0. The region of the pixel of the _{N B} rows × _{M B} columns to a central pixel _(x 1, _{y 1)} and region of interest _{R B.} The image processing unit 106, vector data _B from the luminance value of the image contained in the region of interest _{R B = {b 0, b} 1, ..., b n} to create.

Next, the image processing unit 106, an indicator with two vector data A, B created, whether the region of interest R _A and region of interest R _B are similar degree (or extent or different) For example, the mismatch degree d (x ₁ , y ₁ ) is calculated. The mismatch degree d (x ₁ , y ₁ ) becomes smaller, for example, as the values of the components of the two vector data are closer (the two vector data are similar), and the values of the components of the two vector data are farther away. (The two vector data are not similar). That is, the smaller the mismatch degree d (x ₁ , y ₁ ), the higher the degree of matching between the images of the attention area R _A and the attention area R _B. The mismatch degree d (x ₁ , y ₁ ) can be obtained by the following equation 1, for example.

Further, the inconsistency d (x ₁ , y ₁ ) may be calculated by other arithmetic processing. As another arithmetic process, for example, there is an arithmetic process of the following formula 2, and in this case, the arithmetic processing amount can be reduced.

The image processing unit 106 calculates the inconsistency d while changing the position of the region of interest R _B on the image of the image-forming optical unit C1 in the main scanning direction D _X and the subscanning direction D _Y, inconsistency d is minimum By detecting the position, the position that most closely matches the attention area _RA is detected. However, the imaging optical system 101 shown in FIG. 2, the image pickup element 141, 142 when the document position is changed in the depth direction _{D Z,} ..., the imaging magnification of the image changes for 148. In this case, not only the position of the region of interest R _B, it is necessary to calculate the dissimilarity d while also changing the size of the region of interest R _B.

Moreover, the vector data used for calculating the inconsistency d is to the luminance values of the pixels in the region of interest R _A and region of interest R _B may be used as it is, it may be used an averaging process or sampled brightness values. For example, the image matching area may be detected by a two-stage process as described below. In the first stage, to create the vector data A and B using an averaging process or sampled brightness values is most consistent with the region of interest R _A by calculating the inconsistency d while changing greatly the position of the region of interest R _B performing rough refine process the position of the region of interest R _B. In the second stage, the vector data A and B are recreated using the luminance values of the pixels in the attention areas R _A and R _{B as they} are, and the position of the attention area R _B is changed pixel by pixel around the previously narrowed position. by performing the process of calculating the inconsistency d, it detects the position of the region of interest R _B that best matches the region of interest R _a.

Incidentally, attention when there is no feature in the region R _A, inconsistency d be changing the position of the region of interest R _B hardly changes. In this case, there is a possibility that the region of interest R _A and region of interest R _B is erroneously detected most matched position. To avoid such a situation, initially, when the region of interest R _A or region of interest to assess whether R _B is characterized in images included in, there is no feature either one of the region of interest , without the detection of the position of the region of interest R _a and region of interest R _B are identical, it may be estimated binding position from the detection result of the peripheral region of interest. For evaluating whether or not the attention area _RA has a feature, for example, any one of the standard deviation, variance, and difference between the maximum value and the minimum value of each component included in the vector data A can be used. . If these values are equal to or greater than a certain value, it may be determined that the image included in the attention area _RA has some characteristics.

The center pixel of the region of interest _{R B} mismatch degree d is minimized _{(x 1 _min, y 1 _min} ) when that pixel of the image taken by the image pickup element section through an imaging optical section C0 _{(x 0, y} 0) That is, the pixel (x ₁ —min, y ₁ —min) of the image picked up by the image pickup device portion through the imaging optical portion C1 reads the same portion of the document 70. Therefore, the image of the imaged line L ₁ to the image pickup element section through an imaging optical unit C1 in which the image of the line L ₀ which is captured in the image sensor section are matched through an imaging optical section C0, L ₁ is the formula 3 Can be calculated.
L ₁ = L ₀ + (y ₀ −y ₁ —min) Equation 3

Similarly, the line L ₂ is imaged on the image sensor portion through an imaging optical unit C2 matching through an imaging optical section C1 and the image of the image pickup device unit line L ₁ imaged in _the imaging device section through an imaging optical unit C2 seek line L ₃ which is captured in the imaging device section through an imaging optical section C3 for matching the captured line L ₂ of the image to restore the original image of one line by combining together the respective line data.

FIG. 11 is a diagram for explaining a smoothing process at the time of image combination in the image reading apparatus 100 according to the first embodiment. Smoothing the case in FIG. 11, which couples the line L ₁ of the image 81 taken by the image pickup element unit through line L ₀ and the imaging optical section C1 of the image 80 taken by the image pickup element section through an imaging optical section C0 An example of a digitization process is shown. When connecting the line data of the line L _{0 and} the line data of the line L ₁ , the image is formed by the adjacent imaging optical units with the central pixel of each of the attention area R _A and the attention area R _B as a boundary. It is also possible to adopt a method of joining together images. For example, the pixel data a38 of the line _{L 0} in Fig. 11, ..., to a44, the pixel data b4 of the line _{L 1,} ..., is a method of joining the a11. However, in this case, there is a possibility that conspicuous (between the line L pixel data a44 and the line L ₁ of the pixel data b4 ₀₎ joint portions. For this reason, it is desirable to perform a smoothing process in which a predetermined weight is added to the luminance value of a corresponding pixel of an image formed by an adjacent imaging optical unit.

In Figure 11, the pixel on the line L ₀ of the image 80 taken by the image pickup element section through an imaging optical section C0 a41, ..., a49 is the line of the image 81 taken by the image pickup element section through an imaging optical unit C1 L ₁ on the pixel b0, ..., respectively correspond to b8. At this time, by adding the value obtained by multiplying the weighting coefficient K ₁ in each pixel value of the value and the line L ₁ multiplied by a weighting coefficient K ₀ to each pixel value of the line L _0, the joint portion is smoothed The combined result can be obtained. Weighting coefficient K ₀ and the weighting coefficient K ₁ is a coefficient for performing the weighting are set so as respectively to 1.0 adding coefficient values of the corresponding pixel position. Weighting coefficient K ₀ is approached as becomes smaller coefficient to the image 81 taken by the image pickup element section through an imaging optical section C1 (coefficient in the range of 0 to 1), for example, from left to right in FIG. 11 In order, 1, 4/5, 3/5, 2/5, 1/5, 0. Weighting coefficient K ₁ is a coefficient becomes smaller as closer to the image 80 taken by the image pickup element section through an imaging optical section C0 (coefficient in the range of 0 to 1), for example, toward the left from the right of FIG. 11 In order, 1, 4/5, 3/5, 2/5, 1/5, 0.

The image processing unit 106 includes a smoothing processing unit to the image synthesizing means in 106b, in the smoothing processing means, the smoothing of the line L ₀ of the image 80 taken by the image pickup element section through an imaging optical section C0 pixel values of the image regions is weighted by the weight coefficient K _0, the pixel values of the image of the smoothed region of the line L ₁ of the image 81 taken by the image pickup element section through an imaging optical unit C1 in weighting coefficient K ₁ weighted by adding weighted pixel values of the image of the smoothed region of the line L ₀ of the image 80 and the smoothed region of the line L ₁ of the image 81 image weighted with the pixel values respectively, the composite image Pixel values in the smoothing region are obtained.

After the combination of one line (one line) of the picked-up image from the image picked up by the image pickup device unit through the image forming optical unit C0 to the image picked up by the image pickup device unit through the image forming optical unit C3 is selected last time select the next line is the line of the line L ₀ (L _{0 +1),} it performs the same process as before. At this time, when the image of one image forming optical unit is enlarged or reduced, the image is picked up through the image line (L ₀ +1) of the image picked up by the image pickup device unit through the image forming optical unit C0 and the image forming optical unit C1. In some cases, the line (L ₁ +1) of the image captured by the element unit may not be the best match. For example, the result is that the line (L ₀ +1) of the image captured by the imaging element unit through the imaging optical unit C0 is the best match with the line L _{1 of} the image captured by the imaging element unit through the imaging optical unit C1. May be obtained. At this time, a method of combining the line (L ₀ +1) of the image captured by the image sensor unit through the imaging optical unit C0 and the line L _{1 of} the image captured by the image sensor unit through the imaging optical unit C1. can also be employed, in this case, since the line L ₁ is repeated, the sub-scanning direction D _Y to as the line L ₁ is extended image. Therefore, in such a case, new line data is created from the line L ₁ and the line (L ₁ +1) of the image picked up by the image sensor unit through the imaging optical unit 1 and connected to the created line. It is preferable to combine the line (L ₀ +1) of the image captured by the image sensor unit through the image optical unit C0.

Further, the line (L ₀ +1) of the image captured by the image sensor unit through the imaging optical unit C0 and the line (L ₁ +2) of the image captured by the image sensor unit through the imaging optical unit C1 are the best match. Results may be obtained. At this time, a process of combining the line (L ₀ +1) of the image picked up by the image pickup device unit through the imaging optical unit C0 and the line (L ₁ +2) of the image picked up by the image pickup device unit through the image forming optical unit C1. it is also possible to employ a method of performing, but becomes discontinuous visible image in the sub-scanning direction D _Y line (L 1 ₊₁₎ is deleted. Therefore, in such a case, new line data is generated by interpolation processing or the like from the line (L ₁ +1) and the line (L ₁ +2) of the image captured by the image sensor unit through the imaging optical unit C1, It is preferable to combine the created line and the line (L ₀ +1) of the image captured by the image sensor unit through the imaging optical unit C0. The above processing is repeated until the last line, and an image for one frame is restored.

Next, a process for correcting the distortion and blur of an image by estimating the document shape from the shift amount of the image combining position will be described. First, the principle of distance information calculation will be described. When the imaging optical system is configured so that the optical axes of the imaging optical units of the first group G ₁₁ and the second group G ₁₂ shown in FIG. in almost the same timing to the same location of the image pickup device unit is a document 70 corresponding to through the first group G ₁₁ each imaging optical unit of the second group G ₁₂ when the imaged area of the original 70 to an in-focus position exists read. That is, the lines L ₀ , L ₁ , L ₂ , and L ₃ (shown in FIG. 9) are substantially the same row as counted from the top of the read image (the upper ends of the images 80,..., 83 in FIG. 9).

On the other hand, as shown in FIG. 12, the distance from the imaging area focus position of the document 70 [Delta] Z, for example, when in 1mm away, each imaging optical unit C0 belonging to the first group G _11, a position for reading the image pickup device unit is a document 70 through C2, deviation occurs in the position where the imaging device unit reads the original 70 through the imaging optical unit C1, C3 belonging to the second group G _12. For example, if the image forming optical system C0 reads the position 70a of the document 70 while moving in the sub-scanning direction D _Y, first position 70a of the image pickup device unit is a document 70 corresponding through an imaging optical section belonging to the first group G ₁₁ read, then, the image pickup device unit corresponding through an imaging optical unit that belongs after the elapse of a certain time in the second group G ₁₂ reads the position 70a of the document 70. Therefore, as shown in FIG. 13, the image captured in the image sensor unit through an imaging optical section belonging to the second group G ₁₂ is captured in the imaging device section through an imaging optical section belonging to the first group G ₁₁ It shifts compared to the image (shifts downward in FIG. 13). That is, the difference of position in the sub-scanning direction D _Y appearing images match between the adjacent images taken by the image pickup element section through an imaging optical unit that adjacent, corresponding to the distance ΔZ from the focus position to the original surface To do. The document surface is a portion where the imaged areas 31, 32,.

The relationship between the distance ΔZ from the in-focus position to the document surface and the image shift amount of the image formed on the imaging surface of the imaging element unit by the adjacent imaging optical unit, as already described with reference to FIG. If the distance from the in-focus position to the original surface is ΔZ ₁ and the image shift amount of the image formed by the adjacent imaging optical unit is ΔY, it can be obtained by the following equation.
ΔY = 2 × ΔZ ₁ × tan θ
Therefore, the distance [Delta] Z ₁ from the focusing position to the document surface can be obtained by the following equation.
ΔZ ₁ = ΔY ÷ 2 ÷ tanθ

  However, depending on the mounting position of each imaging optical unit or imaging element unit, the read image of each imaging optical unit has a fixed shift that occurs regardless of the position of the document surface. The amount of this fixed shift is equal to the amount of image shift between the image forming optical units obtained from an image obtained by reading a test pattern such as an oblique lattice placed at the in-focus position. This image shift amount is acquired in advance as an offset value and stored in a storage device (not shown) in the image processing unit 106. Then, by subtracting this offset value from the image shift amount of the image formed by the adjacent imaging optical unit, the distance ΔZ from the in-focus position to the document surface can be obtained accurately.

  FIG. 14 is a diagram illustrating a case where a spread page of a book (original) 70 as an object to be imaged is read by the image reading apparatus according to the first embodiment. In FIG. 14, 70 b indicates the binding of the book 70. FIG. 15 is a diagram illustrating a case where it is assumed that the facing page of the book 70 on which the plurality of straight lines illustrated in FIG. FIG. 16 is a diagram schematically illustrating an image obtained by actually reading the spread page of the book 70 illustrated in FIG. 14 with the imaging device. FIG. 17 is a diagram in which distortion in the main scanning direction of the read image of the imaging apparatus shown in FIG. 16 is corrected. FIG. 18 is a diagram in which distortion in the sub-scanning direction of the read image of the imaging apparatus shown in FIG. 17 is corrected.

  According to the first embodiment, when the position of the imaging region of the imaging object (original) in the depth direction changes, the transfer magnification of the image also changes. For this reason, the read image is reduced as the original 70 moves away from the top plate 103. When the document 70 is read in an oblique direction from a position inclined with respect to a direction perpendicular to the document surface, the document is reduced and read. For this reason, a plurality of straight lines (for example, 70c and 70d) having the same length (the same length in the main scanning direction) drawn on the facing page (book-type document) 70 of the book shown in FIGS. When the originals lined up at the interval d1 (lined up in the sub-scanning direction) are read, a distorted read image 170 is obtained as shown in FIG. For example, straight lines 70 c and 70 d drawn on the original 70 with a distance d 1 are read as straight lines 170 c and 170 d with a distance d 0 of the read image 170. Further, the straight line closest to the stitch 70b of the original (book) 70 of the read image 170 is read with a reduced length d10 in the read image 170 as shown in FIG.

  In the first embodiment, the angle at which the document surface is read is different for each imaging optical unit, but reading is performed by the process at the time of composite image generation (process at the time of joining) described with reference to FIG. Since the difference in angle can be corrected, the reading angle is shown as 90 degrees in FIG. Further, as shown in FIG. 16, the distortion that reduces the length of the straight line in the main scanning direction to d10 can be corrected if the distance to the document surface and the shape of the document surface are known. First, an image transfer magnification is obtained from the distance to the original surface, and an enlargement process is performed to return the straight line length d10 to the original straight line length based on the shrinkage of the image due to the change in the transfer magnification. The result of this processing is an image 171 and straight lines 171c and 171d in FIG.

Next, as shown in FIG. 14, the distance information at arbitrary points p1 and p2 on the image obtained by joining the cell images acquired through the adjacent imaging optical units is expressed as z (p1) and z (p2), respectively. ), The distance between the points p1 and p2 is changed by Δz1 (= z (p2) −z (p1)). Therefore, the distance d0 between the points p1 and p2 on the read image. Is a distance d1 expressed by the following expression 4 on the actual document 70.

  By multiplying the distance between the points p1 and p2 of the read image (for example, the distance d0) by d1 / d0, the original that has been reduced because the original surface is inclined at the time of reading is restored to the original shape (for example, the distance d1). ) Can be restored.

  Since the distance from the in-focus position to the document surface can be obtained by performing the detection process of the combined position, theoretically, the distance of the imaging optical unit in the main scanning direction is set for each scanning line in the sub-scanning direction. The distance from the in-focus position to the document surface can be obtained for each boundary position (joint of optical cells). As such distance information is acquired at finer intervals, the shape of the original surface can be estimated with higher accuracy, so that the restoration accuracy is also improved.

  Through the above processing, the image correcting unit 106d calculates the inclination of the imaging surface of the imaging object (for example, the inclination Δz1 / d0 in FIG. 14) from the difference in distance obtained at positions spaced apart from each other on the composite image. Then, the actual length of the imaged surface corresponding to a certain interval can be calculated from the inclination of the imaged surface, and the composite image can be expanded and contracted to be equal to the actual length of the imaged surface. In addition, the image correction unit 106d calculates the inclination of the imaging surface of the imaging object in the sub-scanning direction from the difference in distance obtained at a position separated by a certain line in the sub-scanning direction on the composite image, and From the inclination in the sub-scanning direction, the length of the actual imaged surface corresponding to the certain line on the composite image is obtained, and the composite image is expanded and contracted in the subscanning direction so as to be equal to the length of the actual imaged surface. Can do.

FIG. 19 is a diagram schematically illustrating a blurred image obtained when a point image is captured by an imaging apparatus (camera) and a point image distribution function obtained from the blurred image. The image correcting unit 106d can also perform blur correction processing. In the blur correction process, the blur characteristics of an image can be grasped by a point spread function that represents the extent of spread of an image obtained when a point is imaged. If the blurring method of the image is known, the image before blurring can be restored from the blurry image by performing reverse conversion on the blurry image when the image blurs. For example, when the image F becomes a blurred image G by the function H, that is, when F × H = G, the original image F can be restored from the blurred image G by the inverse transformation shown in Equation 5. is there.
F = G × H- ¹ Formula 5

  For example, the image blur occurs because the luminance values of the peripheral pixels of the image before blurring are mixed with the luminance values of the image before blurry. Considering image blurring as an integral operation, an image before blurring can be obtained from a blurry image by performing a differential operation, which is the reverse operation. The point spread function changes depending on how the image is blurred, that is, how much the subject is displaced from the in-focus position. Therefore, the point image distribution function that changes in accordance with the distance from the in-focus position to the document surface is measured in advance using the optical imaging optical unit used for image capture, and from the in-focus position to the document surface. The inverse function to be applied may be selected according to the distance (the distance calculated in step ST6 in FIG. 7).

Since the distance from the in-focus position to the original surface can be obtained by using the result of the detection process of the combined position, each line in the sub-scanning direction _DY and the connection of the imaging optical unit in the main scanning direction D _X Information regarding the distance from the in-focus position to the document surface can be obtained for each eye. According to the image reading apparatus 100 according to the first embodiment, since the blur amount of the image can be estimated from the distance information obtained in this way, the document surface is not flat and the undulations are continuous. However, highly accurate blur correction processing can be performed.

  FIG. 20 is a diagram for explaining another example of the image combining process of the image reading apparatus 100 according to the first embodiment. In the above description, an example has been described in which processing such as detection of a coupling position, image coupling, and calculation of distance information is sequentially performed for each line. However, the detection of the combination position, the combination of the images, and the calculation of the distance information may not be performed in order for each line, but may be performed at regular line intervals. FIG. 20 illustrates a case where the coupling position is detected at an interval of K lines with reference to an image 80 picked up by the imaging element unit through the imaging optical unit C0.

In FIG. 20, the result obtained by the i-th (i is a positive integer) coupling position detection process is represented by a solid line as the i-th coupling position. In the next detection of the (i + 1) -th coupling position, image data at a position separated from the i-th coupling position of the image 80 captured by the imaging device unit through the imaging optical unit C0 by K lines (K is a positive integer). Is detected from the image 81 picked up by the image pickup device section through the imaging optical section C1. In the same manner, a coupling position between adjacent images (images 81 and 82, images 82 and 83) captured by the imaging element unit through the adjacent imaging optical unit is detected. An example of the obtained result is represented by a broken line in FIG. 20 as the (i + 1) th coupling position. At this time, if the document surface is not flat, the number of lines between the i-th coupling position and the (i + 1) -th coupling position of the image picked up by the imaging element unit through each imaging optical unit is not the same. There is a case. In order to combine the images picked up by the imaging element unit through the imaging optical units to generate a continuous image, first, the number of lines between the i-th combined position and the (i + 1) -th combined position However, it is necessary to correct so that each image picked up by the image pickup device section through each imaging optical section is the same. This correction method includes a method of deleting and / or inserting line data from each image picked up by the image sensor unit through the imaging optical unit, and an enlargement of each image picked up by the image sensor unit through the image forming optical unit. And / or a reduction method. However, deleting line data, the image data of one line from the image read continuously is lost, there is a case where the discontinuous portions in the sub-scanning direction D _Y occurs, becomes conspicuous that part. When deleting the line data, it is distributed and deleted over a plurality of lines including the surrounding lines (for example, Q (including the line to be deleted by interpolation processing or the like so that the deleted line is not conspicuous). (Q is an integer of 3 or more) It is desirable to generate new (Q-1) line image data from line image data). In addition, when inserting line data, a process of repeating the same line data as the preceding and following line data may be adopted, but the line generated by generating interpolation data from the surrounding line data Inserting data is desirable because the insertion line is not noticeable.

As described above, according to the image reading apparatus 100 according to the first embodiment, the main scanning direction D _X, for each border of the image forming optical unit, in a fine pitch corresponding to the number of the imaging optical section The distance between the top plate 103 and the imaged area of the original 70 can be measured. Therefore, since the distance to the document surface can be estimated, even when the read image is distorted due to the float or tilt of the document, the distortion can be corrected. Further, by providing a plurality of imaging optical units in the main scanning direction, the image reading apparatus 100 can be reduced in size. Even when the original 70 is a wrinkled sheet or near the binding of a book, it is possible to correct image distortion due to defocus for each fine area in the image.

Further, as described above, according to the image reading apparatus 100 according to the first embodiment, in the main scanning direction D _X , fine details corresponding to the number of imaging optical units are provided for each boundary of the imaging optical units. The distance between the top plate 103 and the imaged area of the original 70 can be measured with the pitch. Therefore, even when the original 70 is a wrinkled sheet or near the binding of a book, it is possible to correct image blur due to defocus for each fine region in the image. As described above, according to the image reading apparatus 100 according to the first embodiment, even when an image is formed at a position deviating from the depth of focus of the imaging element unit, the image is within the depth of focus. In addition, an image close to the focused state can be generated. For this reason, the image reading apparatus 100 according to Embodiment 1 can have a substantially large depth of field.

According to the image reading apparatus 100 according to the first embodiment, the main scanning direction D _X in by providing the plurality of imaging optical unit, it is possible to reduce the size of the image reading apparatus 100.

Embodiment 2. FIG.
FIG. 21 is a diagram schematically showing the configuration of the image reading apparatus 200 according to Embodiment 2 of the present invention. FIG. 21 includes a perspective view (left side) schematically showing the configuration of the optical system of the image reading apparatus 200 and a block diagram (right side) schematically showing the configuration of the image signal processing system. As shown in FIG. 21, the image reading apparatus 200 includes an imaging optical system 201, an illumination light source 202, a top plate 203, and a plurality of image sensor units 241, 242,. A memory 205 and an image processing unit 206. In the image reading apparatus 200 according to the second embodiment, the configuration of the imaging optical system 201 is different from that of the imaging optical system 101 in the first embodiment. The illumination light source 202, the top plate 203, the plurality of image sensor units 241, 242,..., 248, the memory 205, and the image processing unit 206 arranged on the substrate 204 are the illumination light source in the first embodiment. 102, the top plate 103, the plurality of image sensor units 141, 142,.

22A and 22B are a schematic cross-sectional view of the optical system of the image reading apparatus 200 according to Embodiment 2 as viewed in the direction of the line S _22a -S _{22a in} FIG. 21, and S _22b -S in FIG. It is a schematic sectional drawing seen in a _22b line direction. In FIG. 22 (a), the first imaging optical unit 211, 213 belonging to the first group _{G 21,} ..., the main optical path of the first light passing through the 217 is shown. Further, in FIG. 22 (b) primary optical path of the second light passing through the second imaging optical unit 212, 214 and 216 belonging to the second group _{G 22} is shown.

FIG. 23 is a schematic cross-sectional view of the optical system of the image reading apparatus 200 according to Embodiment 2 as viewed in the direction of the line S ₂₃ -S ₂₃ in FIG. In FIG. 23, a document 70 as an example of an object to be imaged is in close contact with the upper surface 203a of the top plate 203 (in Embodiment 2, the upper surface 203a is the in-focus position). The main optical paths when the focused image converges on a point on the imaging surface (in-focus state) are shown.

  In the second embodiment, each of the imaging optical units 211, 212,..., 218 constituting the imaging optical system 201 is an optical system telecentric on the document 70 side. As can be understood from FIGS. 22A and 22B, the imaging optical units 211, 212,..., 218 (the imaging optical unit 218 is not shown in FIG. 22B) have the same configuration. In the second embodiment, each of the imaging optical units 211, 212,..., 218 includes a first lens 252 as a first optical element, an aperture 253 as a stop, and a second lens as a second optical element. 254 and a holding member 255 that holds these, and an optical cell having an independent function.

  In each of the imaging optical units 211, 212,..., 218, the first condenser lens 252 is disposed at the end on the document 70 side, and the second condenser lens 254 is disposed on the end on the imaging element unit 241 side. The aperture (aperture) 253 is disposed between the first condenser lens 252 and the second condenser lens 254 at a focal position behind the first condenser lens 252 (downstream in the light traveling direction). With such a configuration, each of the imaging optical units 211, 212,..., 218 can be a telecentric optical system on the document 70 side.

  In addition, the imaging optical units 211, 212,..., 218 in the second embodiment are arranged in the same manner as the imaging optical units 111, 112,.

The image processing unit 206 includes a combined position detection unit 206a that performs arithmetic processing for detecting a combined position of images captured by the image sensor units 241, 242,..., 248, and a combined position of the captured images. From the image synthesizing means 206b for performing arithmetic processing for combining (synthesizing) the images picked up by the image pickup device portions 241, 242,..., 248, and the in-focus position on the object to be picked up (the upper surface 203a of the top plate 203). a distance calculation unit 206c for performing arithmetic processing for calculating the distance in the depth direction D _Z to a document 70, by using the calculated distance to correct the distortion of the composite image (and, the blurring of the image as needed Image correcting means 206d for performing arithmetic processing for reducing the image. The combined position detecting unit 206a, the image combining unit 206b, the distance calculating unit 206c, and the image correcting unit 206d are the combined position detecting unit 106a, the image combining unit 106b, the distance calculating unit 106c, and the image correcting unit 106d in the first embodiment. It has the same function. Therefore, the image reading apparatus 200 according to the second embodiment has the same effect as the image reading apparatus 100 according to the first embodiment.

  In addition, since the imaging optical units 211, 212,..., 218 of the image reading apparatus 200 are telecentric optical systems on the side of the original 70, the distance ΔZ from the focusing position (the upper surface 203a of the top plate 203) to the original 70 is small. Even if it fluctuates, the imaging magnification of the image formed on the image sensor units 241, 242,. Since the imaging magnification of the image does not change depending on the distance ΔZ, when detecting the image matching area, enlargement or reduction conversion to make the size of the selected images the same is unnecessary, and high-speed signal processing is possible. It becomes. Therefore, according to the image reading apparatus 200 according to the second embodiment, the load of image processing for combining the images read by the imaging element units 241, 242,..., 248 through the imaging optical units 211, 212,. Can be greatly reduced.

Further, when the imaging optical units 211, 212, ..., 218 are configured and arranged so that the optical axes of the imaging optical units 211, 212, ..., 218 are perpendicular to the main scanning direction D _X , focus position imaging optical section 211 and 212 also distance ΔZ is varied to manuscript 70 from (upper surface 203a of the top plate 203), ..., the image captured by the image sensor unit through 218, in the main scanning direction _{D X} It does not vary with respect to position, but only moved in the sub-scanning direction D _Y. Further, the imaging magnification does not change even if the distance ΔZ from the in-focus position (the upper surface 203a of the top plate 203) to the document 70 varies. Therefore, in the second embodiment, the image processing in the main scanning direction D _X is not required, the image shift amount of the position of the two images that are adjacent in the subscanning direction D _Y during image synthesis only, the shift in the sub-scanning direction D _Y The correction to be performed may be performed. Therefore, according to the image reading apparatus 200 according to the second embodiment, it is possible to reduce the load of the image processing by the image processing unit 206 and complete the signal processing at a higher speed than in the case of the first embodiment. Become. Further, in the image reading apparatus 200 according to the second embodiment, the image processing unit 206 is not required to have a high processing capability, and thus can be realized with a low-cost processing apparatus.

  Similarly, in the image distortion correction process, the process can be reduced. Further, since the transfer magnification does not change even if the distance to the document surface changes, when a document having the shape shown in FIG. 14 and lines of the same length arranged at equal intervals is read, the document as shown in FIG. An image shortened only in the tilt direction (main scanning direction) is obtained. Therefore, in the distortion correction process according to the second embodiment, a process for correcting a change in transfer magnification according to the document surface distance (that is, a process for expanding and contracting an image as shown in FIG. 16 to an image as shown in FIG. 17) is necessary. is not.

  In the second embodiment, points other than those described above are the same as those in the first embodiment.

Embodiment 3 FIG.
FIG. 24 is a diagram schematically showing the configuration of the optical system of the image reading apparatus 300 according to Embodiment 3 of the present invention. In FIG. 24, the Y axis (sub-scanning direction D _Y ) is in the horizontal direction, the Z axis (depth direction D _Z ) is in the vertical direction, and the X axis (main scanning direction D _X ) is on the drawing surface. It is drawn in a vertical direction toward the front of the page.

The image reading apparatus 300 according to the third embodiment, the imaging optical system 301, an illumination light source (not shown), a top plate 303, disposed on the substrate 304a (imaging belonging to the first group _{G 31} corresponding) plurality of first image sensor unit to the optical unit (e.g., an imaging element unit 343) corresponding to the image-forming optical unit belonging to that disposed on the substrate 304b (the second group G ₃₂₎ a plurality of second 2 imaging device units (for example, imaging device unit 344), a memory (not shown), and an image processing unit (not shown). The imaging optical system 301 includes a plurality of imaging optical unit 313 belonging to the first group _{G 31,} and a plurality of imaging optical unit 314 belonging to the second group _{G 32.} An illumination light source (not shown), a top plate 303, a plurality of image sensor portions (343, 344, etc.) arranged on the substrates 304a and 304b, a memory (not shown), and an image processing unit (not shown) in the third embodiment. (Not shown) are the same as the illumination light source 202, the top plate 203, the plurality of image sensor sections 241, 242,..., 248, the memory 205, and the image processing section 206 arranged on the substrate 204 in the second embodiment. It has the structure and function. In addition, a plurality of imaging element units and a second group G ₃₂ corresponding to a plurality of imaging optical units (for example, the imaging optical unit 313) belonging to the first group G ₃₁ of the image reading apparatus 300 according to the third embodiment. A plurality of imaging element units corresponding to a plurality of imaging optical units belonging to (for example, the imaging optical unit 314) are a plurality of imaging element units 211, 213, ..., of the image reading apparatus 200 according to the second embodiment. 217 and a plurality of image sensor sections 212, 214,..., 218, and have similar functions.

In the image reading apparatus 300 according to the third embodiment, the configuration of the imaging optical system 301 is different from the configuration of the imaging optical system 201 in the second embodiment. In the imaging optical system 301 according to the third embodiment, the optical path of light from the first imaged region (for example, the imaged regions 31, 33,..., 37 in FIG. 21) of the document 70 is substantially parallel to the top plate 303. The first optical path of light from the first folding mirror 351a that bends in the horizontal direction and the second imaged area (for example, the imaged areas 32, 34,... And a second folding mirror 351b that bends in the opposite direction to the light reflected by the folding mirror 351a. In the imaging optical system 301 of the third embodiment, the first imaging optical section belonging to the first group _{G 31} (e.g., image-forming optical unit 313) includes a first fold mirror 351a, optical It consists cell 363 Metropolitan, second imaging optical section belonging to the second group _{G 32} (e.g., image-forming optical unit 314) includes a second fold mirror 351b, comprised of the optical cell 364 Prefecture. In the third embodiment, the first imaging optical unit (e.g., image-forming optical unit 313) second imaging optical unit belonging to and the second group G ₃₂ belonging to the first group G ₃₁ (e.g., imaging Each optical axis of the optical unit 314) is a horizontal direction parallel to the top plate 303, but may be a direction inclined with respect to the horizontal direction. Each of the first folding mirror 351a and the second folding mirror 351b is a mirror that is divided into a plurality of parts corresponding to each imaging optical unit, even if it is one long mirror. Also good. Furthermore, the first bending mirror 351a and the second bending mirror 351b may be optical elements other than the mirror as long as they have a function of changing the direction of light. The structures of the optical cells 363 and 364 may be other structures such as the structure of the optical cell of the first embodiment.

As described above, the image reading apparatus 300 according to the third embodiment can achieve the same effects as the image reading apparatus 200 according to the second embodiment. Specifically, in the main scanning direction D _X , between the top plate 103 and the imaged area of the document 70 at a fine pitch corresponding to the number of imaging optical units for each boundary of the imaging optical units. Distance can be measured. Therefore, since the distance to the document surface can be estimated, even when the read image is distorted due to the float or tilt of the document, for example, image data with corrected distortion as shown in FIG. 18 can be generated. it can.

Further, since the image reading apparatus 300 according to the third embodiment is provided with the first folding mirror 351a and the second folding mirror 351b to bend the optical path, the image reading apparatus 300 in the depth direction D _Z (Z-axis direction). The thickness of the device can be reduced, and the device can be miniaturized.

  The third embodiment is the same as the second embodiment except for the points described above.

Embodiment 4 FIG.
FIG. 25 is a diagram schematically showing a configuration of an image reading apparatus 400 according to Embodiment 4 of the present invention. FIG. 25 includes a perspective view (upper side) schematically showing the configuration of the optical system of the image reading apparatus 400 and a block diagram (lower side) schematically showing the configuration of the image signal processing system. FIG. 26 is a schematic perspective view showing a configuration of one imaging optical unit 411 of the image reading apparatus 400 according to Embodiment 4, and a diagram showing main light beams. FIG. 27 is a diagram showing a schematic cross section and main light rays when the optical system of the image reading apparatus 400 according to Embodiment 4 is viewed in the direction of line S ₂₇ -S ₂₇ in FIG. In the figure, place the X-axis in the main scanning direction D _X in the reading of the image, place the Y-axis in the sub-scanning direction D _Y perpendicular to the main scanning direction D _X, both in the main scanning direction D _X and the subscanning direction D _Y placing the Z-axis in the depth direction D _Z perpendicular to.

  As illustrated, the image reading apparatus 400 according to the fourth embodiment includes an imaging optical system 401, an illumination light source (not shown), a top plate 403 (not shown in FIG. 25), and a substrate 404. .., A memory 405, and an image processing unit 406. In the fourth embodiment, an imaging optical system 401, an illumination light source (not shown), a top plate 403, a plurality of image sensor units 441, 442,... Arranged on a substrate 404, a memory 405, and an image processing unit 406 Are the same as the imaging optical system 201, the illumination light source 202, the top plate 203, the plurality of image sensor units 241, 242,... Arranged on the substrate 204, the memory 205, and the image processing unit 206 in the second embodiment. It has the function of.

In the image reading apparatus 400 according to the fourth embodiment, the configuration of the imaging optical system 401 is different from the configuration of the imaging optical system 201 in the second embodiment. The imaging optical system 401 according to the fourth embodiment employs a configuration including a mirror that bends light from the imaging region of the document 70. In the image forming optical system 401 of the fourth embodiment, the first imaging optical section belonging to the first group G ₄₁ (e.g., image-forming optical unit 411) includes a fold mirror 451a, the reflection-type light-converging element A first concave mirror 452a (for example, a condensing mirror), an aperture 453a that functions as a diaphragm, a second concave mirror 454a that is a reflective condensing element (for example, a condensing mirror), and a bending mirror 455a. Composed. The second imaging optical section belonging to the second group _{G 42} (e.g., image-forming optical unit 412) includes a fold mirror 451 b, a first concave mirror 452b is a reflective light-converging element, functions as a throttle Aperture 453b, a second concave mirror 454b which is a reflective condensing element, and a bending mirror 455b.

  The first concave mirrors 452a and 452b in the fourth embodiment each have a condensing function corresponding to the first condensing lens 252 in the second embodiment. Apertures 453a and 453b in the fourth embodiment each have a diaphragm function corresponding to aperture 253 in the second embodiment. Second concave mirrors 454a and 454b in the fourth embodiment each have a condensing function corresponding to second condensing lens 254 in the second embodiment. Therefore, the imaging optical system 401 in the fourth embodiment has the same function as the imaging optical system 201 in the second embodiment. For this reason, the image reading apparatus 400 according to the fourth embodiment can achieve the same effects as the image reading apparatus 200 according to the second embodiment.

  In the above description, each imaging optical unit has two concave mirrors, ie, the first concave mirror 452a (or 452b) and the second concave mirror 454a (or 454b). Direction) and the width direction of the apparatus (Y-axis direction), the image reading apparatus can be reduced in size.

  In addition, this invention is not limited to the said aspect, It is also possible to make the 1st concave mirror 452a, 452b or the 2nd concave mirror 454a, 454b into a reflective mirror which does not have a condensing function. In the present invention, the first concave mirrors 452a and 452b or the second concave mirrors 454a and 454b can be formed of lenses. Furthermore, the number of concave mirrors included in each imaging optical unit can be three or more.

Next, the image reading apparatus 400 according to the fourth embodiment will be described more specifically. The length of the main scanning direction D _X of the imaging area imaged by the imaging element unit corresponding to one imaging optical unit and which is, for example, 10 mm. The inclination angle θ in the sub-scanning direction D _Y of the optical axis of the imaging optical section relative to the normal of the upper surface 403a of the top plate 403, for example, 5 °. That is, the inclination angle in the sub-scanning direction _{D Y} from the document 70, i.e., light having a main light beam traveling in the direction of 5 ° relative to the normal of the upper surface 403a of the top plate 403, bend the optical path by the fold mirror 451a or 452a It is done. The light whose optical path is bent by the bending mirror 451a or 452a proceeds in a gentle oblique downward direction in which the principal ray direction forms an angle of 8 ° with respect to the sub-scanning direction D _Y (Y axis). The light enters the concave mirror 452a or 452b.

The focal length f ₄₅₂ of the first concave mirrors 452a and 452b is, for example, 20 mm. The distance from the document 70 to the first concave mirror 452a or 452b is designed to be approximately 20 mm, and the light reflected by the first concave mirror 452a or 452b is collimated. The aperture 453a or 453b is provided, for example, at a position of 20 mm from the first concave mirror 452a or 452b along the optical axis. Since the distance of 20 mm is equal to the focal length of the first concave mirror 452a or 452b, the imaging optical unit (for example, the imaging optical units 411 and 412 in FIG. 25) is an optical system telecentric on the document 70 side.

The aperture diameter of the aperture 453a or 453b determines the brightness and depth of field of each imaging optical unit. Here, the case where the aperture diameter φ of the apertures 453a and 453b is 1 mm will be described. At this time, the F value of the optical system is 20. Optimum arrangement of optical components of the entire imaging optical unit (for example, imaging optical unit 411 or 412 in FIG. 25), and the first concave mirrors 452a and 452b and the second concave mirrors 454a and 454b are optimally used by using an aspherical shape or the like. by designing of at least ± 2 mm in the depth direction D _Z focus position as a reference, i.e., it is possible to obtain a depth of field of 4mm in the depth direction D _Z.

The light that has passed through the apertures 453a or 453b is collected by the second concave mirror 454a or 454b, bent by the bending mirror 455a or 455b, and then coupled onto the image sensor portions 441, 443,. Image. Here, if the focal length f ₄₅₄ of the second concave mirror 454a or 454b is 20 mm, an inverted image with an imaging magnification of 1 is formed. A process for generating (restoring) a composite image from inverted images captured by a plurality of image sensor units is the same as the process performed by the image processing unit 106 described in Embodiment 1, for example.

  An example of the image reading apparatus 400 according to Embodiment 4 includes an optical path length from the aperture 453a or 453b to the second concave mirror 454a or 454b, and an imaging element unit 441, 443,. Since the distances to 444,... Are both set to 20 mm, a telecentric optical system is formed not only on the original 70 side but also on the image side. In this way, by constructing a telecentric optical system on the image side as well, the installation positions of the image sensor elements 441, 443,... Or 442, 444,. There is an effect that the imaging magnification becomes constant regardless of the position.

  As described above, in the image reading apparatus 400 according to the fourth embodiment, the first concave mirrors 452a and 452b and the second concave mirrors 454a and 454b are used as the condensing means, so that chromatic aberration does not occur. There are also advantages. In particular, in an optical system having a large depth of field, chromatic aberration tends to be noticeable. However, in the image reading apparatus 400 according to Embodiment 4, chromatic aberration can be avoided by using a reflective optical system.

  In the image reading apparatus 400 according to the fourth embodiment, since the optical element is configured by a reflecting mirror, the optical path is folded back, and the apparatus thickness direction (Z-axis direction) and apparatus width direction (Y-axis direction). ) Is advantageous in that the entire optical system can be reduced in size.

  In the above description, the optical path length from the document 70 to the image sensor elements 441, 443,... 442, 444,. Therefore, if the first and second bending mirrors 451a and 452b are not provided, and the same imaging optical unit is used by using a lens having the same function as the first concave mirrors 452a and 452b and the second concave mirrors 454a and 454b. Is formed, the imaging optical part has a thickness in the Z-axis direction of about 80 mm. On the other hand, in the image reading apparatus 400 according to the fourth embodiment, the optical path is folded by the folding mirrors 451a and 452b, the first concave mirrors 452a and 452b, and the second concave mirrors 454a and 454b. The thickness in the Z-axis direction can be reduced to about 23 mm.

  Further, in the image reading apparatus 400 according to the fourth embodiment, since the imaging magnification of the imaging optical unit can be set to 1, an existing imaging sensor can be used as the imaging element unit, and the apparatus can be reduced. There is an advantage that it can be priced. In other words, if the optical system is a reduction system, the resolution of the image obtained by the resolution of the image sensor unit itself deteriorates unless one pixel unit of the image sensor unit is reduced in accordance with the reduction magnification. In the image reading apparatus 400 according to the fourth embodiment, since the imaging magnification of the imaging optical unit can be set to 1, the resolution of the existing contact image sensor that captures an existing erecting equal-magnification image is set to 600 dpi. As a result, a resolution of 600 dpi can be achieved.

  Further, in the image reading apparatus 400 according to Embodiment 4, when the imaging magnification of each imaging optical unit is set to 1, the first concave mirrors 452a and 452b and the second concave mirrors 454a and 454b of each imaging optical unit are provided. It can comprise with the same member. In particular, as in the image reading device 400 according to the fourth embodiment, if the optical system is telecentric on both the document 70 side and the image side, the first concave mirrors 452a and 452b and the second concave mirror 454a of each imaging optical unit. Even if the shapes of 454b and 454b are the same, an optical system having an imaging condition with sufficient resolution can be designed. Thus, since the same member can be used for each concave mirror, there is an effect that the cost of the apparatus can be reduced.

Next, an example in which a plurality of imaging optical units are combined will be described. An imaging optical unit (rays are indicated by broken lines) belonging to the first group G ₄₁ has an optical axis with an inclination angle of 5 ° with respect to a perpendicular line from the original 70 to the upper surface 403 a of the top plate 403. Further, the imaging optical unit belonging to the second group G ₄₂ (indicating the light by a solid line), relative to the normal of the upper surface 403a of the top plate 403 from the document 70, the inclination angle of the imaging optical section belonging to the first group has an optical axis inclined angle of 5 ° on the opposite side in the sub-scanning direction D _Y. The interval between adjacent imaging optical units (for example, imaging optical units 411 and 412 in FIG. 25) is 9 mm. The distance between the imaging optical units in the same row (same group G ₄₁ or G ₄₂ ) is 18 mm. Since one imaging read width of the imaging area imaged by the imaging element unit through an optical portion (length in the main scanning direction D _Z) is a 10 mm, the imaging area (read between the adjacent image-forming optical unit The width of the overlapping region (region) is 1 mm. 1mm The captured image in the main scanning direction _{D X,} in the case of 600dpi is included about 24 pixels. This number of pixels is large enough for processing by the image processing unit to combine images captured by the imaging element unit through the adjacent imaging optical unit.

As shown in FIG. 27, the originals in the imaging optical unit (rays are indicated by broken lines) belonging to the first group G ₄₁ and the imaging optical unit (light rays are indicated by solid lines) belonging to the second group G ₄₂ the optical path from 70 to aperture 453a or 453b is intersect, it shifted in the main scanning direction _{D X} (do not cross) has advanced the space. That is, the respective optical paths in the imaging optical unit (rays are indicated by broken lines) belonging to the first group G ₄₁ and the imaging optical unit (rays are indicated by solid lines) belonging to the second group G ₄₂ are three-dimensional. Does not interfere with each other, that is, does not overlap. According to the image reading apparatus 400 according to the fourth embodiment, it is possible to reduce the size of the optical system in which the optical paths do not interfere with each other.

Moreover, the focus position of the document 70 side, the image reading apparatus 400 according to the fourth embodiment, designed from the upper surface 403a of the top plate 403b to the third document position 73 of 1 mm, furthermore, the first group _{G 41} a line of the imaging area to be read through an imaging optical section (indicating the light by the dashed line) that belongs, and the line of the imaging area to be read through an imaging optical section belonging to the second group G ₄₂ (indicating the light by the solid line) The third document position 73 is designed to intersect. As described above, since the optical system itself has a depth of field of ± 2 mm, a sufficiently good resolution can be obtained from the upper surface of the top plate 403 to the fourth original position 75 of 3 mm. In other words, the depth of field of the image reading apparatus 400 according to Embodiment 4 is 3 mm from the upper surface 403 a of the top plate 403. If the document 70 is placed within the range of the depth of field, the image formed by the imaging optical system and picked up by the imaging element unit has a good resolution, but the imaged region of the document 70 is focused as much as possible. It is preferable to be placed at a position close to the position. Therefore, when importance is attached to the quality of the captured image, it is desirable to adopt a design in which the in-focus position matches the upper surface 403a of the top plate 403. However, in order to avoid an image blur as much as possible, an in-focus position exists, for example, at a position of 2 mm above the top surface 403a of the top plate 403 in order to obtain a device having a greater depth of field. Thus, it is also possible to adopt a design that lowers the position of the top plate 403. In this case, the depth of field can be increased to a range from the upper surface 403a of the top plate 403 to a position 4 mm above it.

As the position of the document 70 moves away from the third original position 73 (focus position in the fourth embodiment), of the imaging area to be read through an imaging optical section belonging to the first group G ₄₁ (indicating the light by a broken line) and line, and the line to be read through an imaging optical section belonging to the second group G ₄₂ (indicating the light by the solid line), leaving the sub-scanning direction D _Y. This is due to the following reason. The first reason is that, as described in the second embodiment, the optical system is telecentric on the original 70 side, and the position of the original 70 is moved away from the third original position 73 (the in-focus position in the fourth embodiment). even, because image magnification does not change with the main scanning direction D _X and the subscanning direction D _Y. The second reason is that since the optical axis of the imaging optical unit is perpendicular to the main scanning direction D _X , the object to be read is read through the imaging optical unit belonging to the first group G ₄₁ (rays are indicated by broken lines). a line of the imaging region, the line to be read through an imaging optical section belonging to the second group G ₄₂ (indicating the light by a solid line) is not moved in the main scanning direction D _X, moves only in the sub-scanning direction D _Y Because. Therefore, in the image reading apparatus 400 according to the fourth embodiment, the position in the depth direction D _Z of the document 70, even if the varied according to the position of the main scanning direction D _X of the document, the first Combining and correcting images taking into account the deviation in the sub-scanning direction between the line of the imaged region read through the imaging optical unit belonging to the group G ₄₁ and the line read through the imaging optical unit belonging to the second group G ₄₂ The processing can be performed by a method similar to the processing method by the image processing unit described in the first embodiment.

  FIG. 28 is a schematic perspective view of the configuration including the light shielding member of the image reading apparatus 400 according to the fourth embodiment, viewed from the document 70 side. FIG. 29 is a schematic perspective view of the configuration including the light-shielding member of the image reading apparatus 400 according to Embodiment 4 as viewed from the imaging element unit side. As shown in FIG. 28 or FIG. 29, the image reading apparatus 400 preferably includes light shielding members 462 and 463 and light shielding slit members 461 provided with slits (holes) 461a and 461b. The image reading apparatus 400 according to Embodiment 4 is an optical system in which the F value is set to 20 in order to increase the depth of field, the amount of light taken into the imaging optical system 401 is small, and there is much light that is not used. For this reason, much of the light scattered from the document 70 becomes unnecessary light that does not enter the imaging optical system. Therefore, it is necessary to appropriately shield unnecessary light.

  For this purpose, in the example shown in FIG. 28, the light-shielding slit member 461 has slits (holes) 461a and 461b arranged in a staggered pattern corresponding to the arrangement of the imaging optical units. In addition, the light shielding members 462 and 463 are more resistant to stray light by shielding the downstream optical path from the outside in the light traveling direction than the apertures 453a and 453b. Furthermore, by installing the light-shielding slit member 470 having the openings 470a and 470b in the optical path portion on the downstream side of the bending mirrors 455a and 455b, the resistance to stray light can be further increased. The openings 470a and 470b are provided corresponding to the imaging element portions 441, 442, 443,.

Further, as shown in FIG. 25, an aperture 453a is a transmission type, the light shielding wall 471 between the imaging optical unit adjacent in the same group _{G 41} or _{G 42} is provided, the traveling direction of the light than the aperture 453a and 453b Since the downstream optical system has an independent configuration that makes it difficult for stray light to enter, the captured image is not deteriorated by stray light, and the quality of the captured image can be improved. In addition, by setting the inner wall surfaces of the light shielding wall 471 and the light shielding members 462 and 463 to black, it is possible to reduce deterioration of the captured image due to stray light entering from the small openings of the apertures 453a and 453b.

Further, as a method of realizing the imaging optical system 401, the following method can be employed. For example, as can be understood from FIG. 25, the main scanning direction D plurality arranged similar optical elements in _X (e.g., main scanning direction D _X plurality arranged first concave mirror, a second aligned plurality in the main scanning direction D _X concave mirror, or an aperture) arranged plurality may be arranged on the elongate support member in the main scanning direction D _X. For example, the imaging optical system 401 includes a first concave mirror array in which a plurality of first concave mirrors are arranged in a row on a support member at an interval of 18 mm, and an aperture array in which slits (holes) are opened at an interval of 18 mm in a row. A second concave mirror array in which a plurality of second concave mirrors are arranged in a row at intervals of 18 mm on the support member can be used. Further, the bending mirrors 451a and 451b and the bending mirrors 455a and 455b can be manufactured by vapor-depositing a reflective material such as aluminum on a single thin plate. Further, since the folding mirrors 451a and 451b are disposed adjacent to each other, for example, the reflecting mirror may be formed by vapor-depositing a reflective material on both slopes of a member having a triangular (or L-shaped) cross-sectional shape.

As described above, the image reading apparatus 400 according to the fourth embodiment can achieve the same effects as the image reading apparatus 300 according to the third embodiment. Specifically, in the main scanning direction D _X , the distance between the top plate and the imaged area of the document is set at a fine pitch corresponding to the number of imaging optical units for each boundary of the imaging optical units. It can be measured. Therefore, since the distance to the document surface can be estimated, even when the read image is distorted due to the float or tilt of the document, for example, image data with corrected distortion as shown in FIG. 18 can be generated. it can.

  Further, if image blur correction processing based on the distance from the in-focus position to the document surface is performed, the depth of field (range from the top surface 403a of the top 403 to 3 mm) determined by the optical system can be further increased. become. For example, when the distance ΔZ from the in-focus position to the document surface is 3 mm or less, the image blur correction process by the image processing unit 406 is not performed, and the image blur correction process is performed only when the distance ΔZ exceeds 3 mm. May be performed. In addition, even if the depth of field determined by the optical system is in the range from the top plate 103 to 3 mm, the applicant can use the image blur correction process by the image processing unit 406 to reduce the distance ΔZ to 6 mm. It has been confirmed that an image with sufficiently good resolution can be acquired.

  Further, according to the image reading apparatus 400 according to the fourth embodiment, the optical path is folded using the folding mirrors 451a and 451b, the first concave mirrors 452a and 452b, the second concave mirrors 453a and 453b, and the folding mirrors 455a and 455b. Therefore, simplification and downsizing of the configuration of the optical system can be realized. In addition, since image processing that reduces image blurring is performed by the processing of the image processing unit 406, a substantial depth of field can be increased.

  In the above description, the imaging optical system 401 of the fourth embodiment corresponds to the first condenser lens 252, the aperture 253, and the second condenser lens 254 of the imaging optical system 201 in the second embodiment. The first concave mirrors 452a and 452b, the apertures 453a and 453b, and the second concave mirrors 454a and 454b can be used, but other configurations can be adopted as the imaging optical system 401 of the fourth embodiment. For example, the imaging optical system 401 includes first concave mirrors 452a and 452b and apertures 453a and 453b corresponding to the first condenser lens 152 and the aperture 153 (FIG. 2) of the imaging optical system 101 in the first embodiment. The imaging optical system 401 may be configured to have

  In the fourth embodiment, points other than those described above are the same as those in the first to third embodiments.

Embodiment 5 FIG.
FIG. 30 is a perspective view schematically showing the configuration of the optical system of the image reading apparatus 500 according to Embodiment 5 of the present invention. FIG. 31 is a schematic cross-sectional view of the optical system of the image reading apparatus 500 according to the fifth embodiment in the direction of the line S ₃₁ -S ₃₁ in FIG. 30 and main light rays (when the document is at the in-focus position). FIG. Further, FIG. 32, see the optical system of the image reading apparatus 500 according to the fifth embodiment in S ₃₁ -S ₃₁ along the line of FIG. 30 schematic cross-sectional and major rays (document is deviated from the in-focus position position FIG. FIG. 33 is a perspective view schematically showing a configuration including a light shielding member of the image reading apparatus 500 according to the fifth embodiment.

  The image reading apparatus 500 according to the fifth embodiment includes an imaging optical system 501, an illumination light source (not shown), a top plate 503, and a plurality of image sensor units 541 arranged on a substrate (not shown). , 542,..., A memory (not shown), and an image processing unit (not shown). An imaging optical system 501, an illumination light source (not shown), a top plate 503, a plurality of image sensor units 541, 542,..., A memory 505, and an image processing unit 506 in Embodiment 5 are: The imaging optical system 401, the illumination light source (not shown), the top plate 403, the plurality of image sensor units 441, 442,... Arranged on the substrate 404, the memory 405, and the image processing unit 406 in the fourth embodiment. Has the same function.

The imaging optical system 501 according to Embodiment 5 includes a plurality of imaging optical units belonging to the first group G ₅₁ and a plurality of imaging optical units belonging to the second group G ₅₂ . In FIGS. 30 to 33, the imaging optical unit showing a main light beam by a broken line (for example, image-forming optical unit 511) is an image-forming optical unit belonging to the first group G _51, showing the main light beam by a solid line an imaging optical unit (e.g., image-forming optical unit 512) is an image-forming optical unit belonging to the second group _{G 52.}

The imaging optical unit belonging to the first group G ₅₁ is reflected by a folding mirror 551a for folding light from the document 70, a first concave mirror 552a for reflecting the folded light, and the first concave mirror 552a. It includes a reflection mirror 553a that reflects light, a second concave mirror 554a that reflects light reflected by the reflection mirror 553a, and a bending mirror 555a. The light reflected by the bending mirror 551a is collimated by the first concave mirror 552a and reaches the reflection mirror 553a. For example, the reflection mirror 553a includes a reflection area having a diameter φ of 1 mm and a black area (not shown) for light absorption outside the reflection area. The light beam reflected by the reflection region of the reflection mirror 553a reaches the second concave mirror 554a, is condensed here, and reaches the bending mirror 555a. The light reflected by the bending mirror 555a forms an image on the image sensor sections 541, 543,.

Similarly, the imaging optical unit belonging to the second group _{G 52} includes a fold mirror 551b bending the light from the document 70, a first concave mirror 552b for reflecting the folded light, the first concave mirror 552b A reflection mirror 553b that reflects the light reflected by the reflection mirror 553, a second concave mirror 554b that reflects the light reflected by the reflection mirror 553b, and a bending mirror 555b. The light reflected by the bending mirror 551b is collimated by the first concave mirror 552b and reaches the reflection mirror 553b. The reflection mirror 553b includes, for example, a reflection region having a diameter φ of 1 mm and a black region (not shown) for light absorption outside the reflection region. The light reflected by the reflection region of the reflection mirror 553b reaches the second concave mirror 554b, is condensed here, and reaches the bending mirror 555b. The light reflected by the bending mirror 555b forms an image on the image sensor sections 542, 544,.

  The entire optical system includes a light shielding slit member 561 having a plurality of slits (holes) 561a and 561b and a light shielding member 562, as shown in FIG. 33, in order to block stray light from the outside.

  In the image reading apparatus 500 according to the fifth embodiment, instead of the apertures 453a and 453b (transmission-type openings) in the image reading apparatus 400 according to the fourth embodiment, reflection mirrors 553a and 553b having a diameter smaller than the light beam diameter are provided. Used. The reflection mirrors 553a and 553b have the same aperture function as the apertures 453a and 453b in the image reading apparatus 400 of the fourth embodiment.

The image reading apparatus 500 according to the fifth embodiment also has the same configuration as that of the image reading apparatus 400 according to the fourth embodiment, except for differences described below. Further, since the image reading apparatus 500 has the same configuration as that of the image reading apparatus 400, the image reading apparatus 500 can basically exhibit the same effects as the image reading apparatus 400. Specifically, in the main scanning direction D _X , the distance between the top plate 103 and the imaged region of the document at a fine pitch corresponding to the number of imaging optical units for each boundary of the imaging optical units. Can be measured. Therefore, since the distance to the document surface can be estimated, even when the read image is distorted due to the float or tilt of the document, for example, image data with corrected distortion as shown in FIG. 18 can be generated. it can.

Further, according to the image reading apparatus 500 according to the fifth embodiment, the aperture function is realized by the reflecting mirrors 553a and 553b instead of being realized by the aperture, so that the sub-scanning direction D _Y (Y The size of the imaging optical system in the axial direction can be reduced. Specifically, in the fourth embodiment, the distance between the first concave mirror and the second concave mirror facing in the sub-scanning direction D _Y is about 60 mm, in the fifth embodiment, the sub-scanning direction D _Y The distance between the first concave mirror and the second concave mirror facing each other is about 20 mm, and can be about one third.

Furthermore, since the imaging magnification of the imaging optical system of the image reading apparatus 500 according to Embodiment 5 can be 1, as shown in FIG. 31, the imaging optical unit belonging to the first group G ₅₁ a first concave mirror 552a and the second concave mirror 554a included, and a reflection mirror 553b included in the image-forming optical unit belonging to the second group _{G 52,} can be placed on the same plane (plane parallel to the XZ plane). Similarly, the first concave mirror 552b included in the optical system in the second group _{G 52,} a second concave mirror 554b, parallel to the reflecting mirror 553a included in the image-forming optical unit belonging to the second group _{G 52} in the same plane (XZ plane It can be installed on the surface.

  The imaging optical system 501 of the image reading apparatus 500 according to Embodiment 5 can be manufactured using a concave mirror array in which a plurality of first concave mirrors 552a and a plurality of second concave mirrors 554a are arranged on the same support member. It is. Since such a concave mirror array having a plurality of first concave mirrors 552a and a plurality of second concave mirrors 554a can be formed by resin molding, for example, the image reading apparatus 500 according to the fifth embodiment has According to this, an effect that the assembly of the optical system can be easily performed with high accuracy is obtained.

  In addition, the image reading apparatus 500 according to Embodiment 5 attaches a reflective member having a mirror finish to a plurality of openings, produces a portion other than the plurality of openings with a black member, and arranges a plurality of reflection mirrors 553a. It is possible to manufacture using a reflecting mirror array arranged in a shape. If such a reflection mirror array is used, an effect that the assembly of the optical system can be easily performed with high accuracy can be obtained.

  The fifth embodiment is the same as the first to fourth embodiments except for the points described above.

  Note that the image reading apparatus according to the present invention may employ a configuration in which two or more embodiments selected from the first to fifth embodiments are appropriately combined.

1 is a diagram schematically showing a configuration of an image reading apparatus according to Embodiment 1 of the present invention. (A) is a diagram showing a schematic cross-section and main beam view optical system of the image reading apparatus according to Embodiment 1 S _2a -S _2a line direction of FIG. 1, (b) is carried out FIG. 2 is a diagram illustrating a schematic cross section and main light rays when the optical system of the image reading apparatus according to the first embodiment is viewed in the direction of the line S _2b -S _2b in FIG. 1. It is a diagram illustrating a S ₃ -S _3-wire seen in the direction schematic cross-sectional and major rays Figure 1 the optical system of the image reading apparatus according to the first embodiment (when the original is in the focus position). FIG. ₃ is a schematic cross-sectional view of the optical system of the image reading apparatus according to the first embodiment in the direction of lines S ₃ -S _{3 in} FIG. It is. 2 is an enlarged view showing the vicinity of a top plate of the image reading apparatus according to Embodiment 1. FIG. 1 is a diagram showing a simplified configuration of an image processing apparatus according to Embodiment 1. FIG. 3 is a flowchart illustrating processing executed by the image reading apparatus according to the first embodiment. 4 is a diagram illustrating a case where an imaged region of a document exists at a focus position in the image reading apparatus according to Embodiment 1. FIG. In the image reading apparatus according to the first embodiment, when an imaged region of a document is present at the in-focus position, images obtained from four image sensor units and a composite image generated by combining them are shown. is there. FIG. 6 is a diagram for explaining how to obtain an image matching area by an image processing unit of the image reading apparatus according to the first embodiment. 6 is a diagram for explaining a smoothing process of an image combination portion by an image processing unit of the image reading apparatus according to Embodiment 1. FIG. 6 is a diagram illustrating a case where an imaged region of a document exists at a position shifted from a focus position in the image reading apparatus according to Embodiment 1. FIG. In the image reading apparatus according to the first embodiment, when the imaged region of the document exists at a position shifted from the in-focus position, the images obtained from the four image sensor units and the composite image generated by combining them are generated. FIG. 3 is a diagram illustrating a case where a spread page of a book (original) as an object to be read is read by the image reading apparatus according to Embodiment 1. FIG. It is a figure which shows the case where it assumes that the facing page of the book in which the some straight line of FIG. 14 was drawn was strongly pressed on the top plate, and was made into the substantially plane. It is a figure which shows the image which read the facing page of the book shown by FIG. 14 with the imaging device. It is the figure which correct | amended distortion of the main scanning direction of the read image of the imaging device shown by FIG. It is the figure which correct | amended the distortion of the subscanning direction of the read image of the imaging device shown by FIG. 6 is a diagram for explaining blur correction processing of the image reading apparatus according to Embodiment 1. FIG. FIG. 6 is a diagram for explaining image combining processing of the image reading apparatus according to the first embodiment. It is a perspective view which shows schematically the structure of the image reading apparatus which concerns on Embodiment 2 of this invention. (A) is a diagram showing a schematic cross-section and main beam view optical system of the image reading apparatus according to the second embodiment to S _22a -S _22a line direction of FIG. 21, (b) is carried out FIG. ₂₂ is a diagram illustrating a schematic cross section and main light rays when the optical system of the image reading apparatus according to the second embodiment is viewed in the direction of the line S _22b -S _22b of FIG. FIG. 22 is a diagram showing a schematic cross section and main light rays when the optical system of the image reading apparatus according to the second embodiment is viewed in the direction of the line S ₂₃ -S ₂₃ in FIG. 21. It is a figure which shows the structure of the optical system of the image reading apparatus which concerns on Embodiment 3 of this invention, and main light rays. It is a perspective view which shows roughly the structure of the optical system in the image reading apparatus which concerns on Embodiment 4 of this invention. FIG. 6 is a schematic perspective view illustrating a configuration of one imaging optical unit of an image reading apparatus according to Embodiment 4, and a diagram illustrating main light beams. It is a diagram showing a schematic cross section and major ray view optical system of the image reading apparatus according to the fourth embodiment in S ₂₇ -S ₂₇ along the line of FIG. 25. FIG. 10 is a schematic perspective view of a configuration including a light shielding member of an image reading apparatus according to Embodiment 4 as viewed from the document side. FIG. 10 is a schematic perspective view of a configuration including a light shielding member of an image reading apparatus according to Embodiment 4 as viewed from the image sensor unit side. It is a perspective view which shows roughly the structure of the optical system in the image reading apparatus which concerns on Embodiment 5 of this invention. FIG. 32 is a diagram showing a schematic cross section and main light rays (when a document is in a focus position) when the optical system of the image reading apparatus according to the fifth embodiment is viewed in the direction of line S ₃₁ -S ₃₁ in FIG. 30; 30 is a schematic cross-sectional view of the optical system of the image reading apparatus according to Embodiment 5 as viewed in the direction of the line S ₃₁ -S _{31 in} FIG. It is. FIG. 10 is a perspective view schematically showing a configuration including a light shielding member of an image reading apparatus according to a fifth embodiment.

Explanation of symbols

31-38 Imaged area, 70 Document (object to be imaged), 70b stitches, 70c, 70d straight line drawn, 71-75 Document position, 80-83, 90-93 Captured image, 84 , 94 composite image (combined image), 100, 200, 300, 400, 500 image reading device, 101, 201, 301, 401, 501 imaging optical system, 102, 202 illumination light source, 103, 203, 303, 403, 503 Top plate, 103a, 203a, 303a, 403a, 503a Top surface of the top plate, 104, 204, 304a, 304b, 404 Substrate, 105, 205, 405, 505 Memory, 106, 206, 406, 506 Image processing unit, 106a 206a, coupling position detection means, 106b, 206b image synthesis means, 106c, 206c distance calculation means, 06d, 206d Image correction means, 111-118, 211-218 Imaging optics (optical cell), 111a-118a optical axis, 141-148, 241-248, 343, 344, 441-444, 541-544 , 152 first condensing lens, 153 aperture (aperture), 155 holding member, 170,171 composite image, 170c, 170d, 171c, 171d straight line drawn image, 172 corrected composite image, 172c , 172d image after straight line correction, 252 first condenser lens, 253 aperture (aperture), 254 second condenser lens, 255 holding member, 313, 314 imaging optical unit, 363, 364 optics Cell, 411, 412, 511, 512 imaging optical unit, 451a, 451b bending mirror, 4 52a, 452b first concave mirror, 453a, 453b aperture (aperture), 454a, 454b second concave mirror, 455a, 455b folding mirror, 551a, 551b folding mirror, 552a, 552b first concave mirror, 553a, 553b reflecting mirror (aperture) ), 554a, 554b second concave mirror, 555a, 555b fold mirror, _AX 1, AX ₂ optical axis, C0 to C3 forming optical _{unit, G 11, G 21, G} 31, G 41, G 51 first group ( first _{column), G 12, G 22,} G 32, G 42, G 52 the second group (second column), _{D X} main scanning direction (X axis direction), _{D Y} sub-scanning direction (Y axis direction), D _Z depth direction (Z-axis direction), R _A first region of interest, R _B second region of interest.

Claims (17)

A positioning unit that determines the position of the object to be imaged in the depth direction perpendicular to both the main scanning direction and the sub-scanning direction, and places the imaged object at a predetermined in-focus position or a position shifted in the depth direction from the in-focus position When,
A plurality of first imaging optical units that form a plurality of first images by condensing a plurality of first lights from a plurality of first imaging regions on the imaging object; ,
A plurality of second image pickup areas arranged alternately with the plurality of first image pickup areas in the main scanning direction on the image pickup object, wherein the adjacent first image pickup areas and the second image pickup areas are arranged. A plurality of second lights traveling in a direction different from the plurality of first lights in the sub-scanning direction from the plurality of second imaging areas partially overlapping with the imaging area in the main scanning direction, respectively. A plurality of second imaging optical units that form a plurality of second images by condensing; and
A plurality of first imaging element units that are arranged corresponding to the plurality of first imaging optical units and that capture the plurality of first images;
A plurality of second imaging element units that are arranged corresponding to the plurality of second imaging optical units and that capture the plurality of second images;
A storage unit for temporarily storing image information acquired by the plurality of first image sensor units and the plurality of second image sensor units;
An image processing unit that generates a composite image by combining the stored image information,
Each of the plurality of first imaging optical unit, a focused image of the object to be imaged placed in the focus position, Ru is formed on the imaging surface of the corresponding first image sensor unit a configuration,
Each of the plurality of second imaging optical unit, a focused image of the object to be imaged placed in the focus position, Ru is formed on the imaging surface of the corresponding second image sensor unit a configuration,
The image processing unit
The first image sensor unit of the plurality of first image sensor units and the second image sensor unit of the plurality of second image sensor units, wherein the plurality of first imaged regions and the first and the second image pickup device unit and the first image sensor unit for each image the second imaged region and the imaging region adjacent of the plurality of second imaged region for each of the sets, the second in the second image by the image and the second image sensor portion of the first region of interest in the first image by the first image sensor portion is imaged by imaging An image matching region that matches the image of the region of interest is detected, and the first image is based on the position of the image matching region in the first image and the position of the image matching region in the second image. A coupling position detecting means for determining a coupling position for coupling the second image and the second image;
Image combining means for generating the composite image by combining the first image and the second image at the connection position;
The focusing is performed using an image shift amount that is a difference between the position of the image matching area in the first image in the sub-scanning direction and the position of the image matching area in the second image in the sub-scanning direction. Distance calculating means for calculating a distance in the depth direction of a region where the first imaged region and the second imaged region overlap from a position ;
An image reading apparatus comprising: an image correcting unit that estimates a shape of the object to be imaged from a distance calculated by the distance calculating unit and corrects distortion of the composite image based on the shape estimation result. The principal rays of the plurality of first lights traveling from the plurality of first imaging regions to the plurality of first imaging optical units are parallel to each other,
The image according to claim 1, wherein chief rays of the plurality of second lights traveling from the plurality of second imaging regions to the plurality of second imaging optical units are parallel to each other. Reader. The distance calculating means includes
Means for holding the image shift amount when the position in the depth direction of the adjacent first imaged region and the second imaged region coincides with the in-focus position as a reference value of image displacement;
The image reading apparatus according to claim 1, further comprising: a unit that calculates the distance based on a difference between the image shift amount and the held reference value. The distance calculating means includes
Means for preliminarily storing a change amount of the distance when the image shift amount is changed by a certain amount;
Means for calculating a distance conversion coefficient that is a value obtained by dividing the difference between the image shift amount and the held reference value by the amount of change in the distance;
The image reading apparatus according to claim 3, wherein the image correction unit performs the image processing to reduce distortion of the composite image using the distance conversion coefficient. The image correction means is configured to calculate a main distance from a difference in distance in the depth direction obtained for each joint between the first imaging optical unit and the second imaging optical unit in the main scanning direction on the composite image. Calculating the rate of change of the distance in the depth direction of the object to be imaged relative to the distance in the scanning direction ;
The actual length of the imaged region corresponding to the interval between the first imaging optical unit and the second imaging optical unit using the change rate of the distance in the depth direction with respect to the distance in the main scanning direction Calculate
The composite image is expanded or contracted in a main scanning direction so that a portion corresponding to the interval between joints of the imaging optical unit becomes equal to the calculated actual length of the imaged region. The image reading apparatus according to any one of 1 to 4. The image correction unit is configured to determine a change rate of a distance in the depth direction of the imaging target with respect to a distance in the sub-scanning direction from a difference in the distance in the depth direction obtained at a position separated by a certain line in the sub-scanning direction on the composite image. To calculate
Using the rate of change in the depth direction distance with respect to the sub-scanning direction distance , calculate the actual length of the imaged region corresponding to the constant line interval ,
The composite image is expanded or contracted in a sub-scanning direction so that a portion corresponding to the interval of the certain line in the composite image becomes equal to the calculated actual length of the imaged region. Item 6. The image reading apparatus according to any one of Items 1 to 5. The coupling position detecting means includes
The first image of the first image is within an overlapping region of the first image and the second image corresponding to a region where the first imaged region and the second imaged region overlap. Means for setting a region of interest and the second region of interest of the second image;
Means for calculating the difference between the image information of the first region of interest and the image information of the second region of interest while changing the positions of the first region of interest and the second image region of interest;
7. The apparatus according to claim 1, further comprising: a unit that determines the first attention area and the second attention area when the difference is minimum as the image matching area. Image reading apparatus. The means for calculating the difference is:
Wherein a first luminance value of the image included in the target region, the second of said first region of interest and the second region of interest from the difference between corresponding components of the luminance values of the image included in the target region The image reading apparatus according to claim 7, wherein the difference is calculated. The coupling position detecting means includes
For image information included in the first region of interest and / or image information included in the second region of interest, any one of standard deviation, variance, and difference between the maximum value and the minimum value of the image information is a constant value. If it is above, perform the process of determining the image matching area ,
For the image information included in the image information and / or the second region of interest contained in the first region of interest, the standard deviation of the image information, distributed, and none of the difference between the maximum value and the minimum value is a constant value the image reading apparatus according to claim 8, characterized in that it comprises a <br/> hand stage is not performed the process for determining the image matching area if not a more.   The calculation of the difference by the means for calculating the difference is performed by changing any one of the positions of the first region of interest and the second image region of interest one line at a time or a predetermined plurality of lines. The image reading apparatus according to any one of claims 7 to 9. The image composition means includes
Means for setting a smoothing region including the coupling position of the first image and the second image;
Multiplying each pixel value of a plurality of pixels in the smoothed area of the first image by a weighting factor that decreases as the second image side is approached, calculates a plurality of weighted first pixel values And multiplying each pixel value of the plurality of pixels in the smoothing region of the second image by a weighting factor that decreases as the first image side is approached, thereby weighting the plurality of second pixel values And calculating the pixel values in the smoothing region of the composite image by adding the weighted first pixel values and the weighted second pixel values, respectively. The image reading apparatus according to claim 1, further comprising: means. Each of the first and second imaging optical units has an optical cell;
The optical cell includes at least one condensing lens for condensing light from the object to be imaged;
The image reading apparatus according to claim 1, further comprising: a diaphragm that restricts a diameter of the light beam of the light.   The image reading apparatus according to claim 12, wherein each of the first and second imaging optical units includes a bending unit that bends light from the object to be read toward the optical cell. The first and second imaging optical units are respectively
Bending means for bending light from the object to be imaged;
At least one concave mirror for collecting the bent light;
The image reading apparatus according to claim 1, further comprising: a diaphragm that restricts a diameter of the light beam of the light.   The image reading apparatus according to claim 14, wherein the diaphragm includes a reflection mirror having a diameter smaller than a light beam diameter of the light traveling toward the diaphragm.   The image reading apparatus according to claim 1, wherein each of the first and second imaging optical units is an optical system that is telecentric on the side of the object to be imaged.   17. The image reading apparatus according to claim 1, wherein each of the first and second imaging optical units is an optical system telecentric on the imaged image side.

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