JP2018100974A - Imaging unit, colorimetric device, and picture formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high-precision imaging in a constantly stable positional relationship between a subject and a color reference chart.SOLUTION: An imaging unit 30 is equipped with a low surface part 32a opposing a subject; a frame body 32 in which an aperture part 32b for picking up an image of the subject and a reference chart KC, which is another subject imaged through the aperture part 32b, are simultaneously imaged side by side; an illumination light source 37 that illuminates the subject and the reference chart KC with illuminating light of substantially the same luminous intensity; an image sensor part 34 that receives reflected light from the subject opposing the aperture part 32b and reflected light from the reference chart KC and simultaneously images the subject and the reference chart KC; a light path length altering member 41 that is arranged on the light path from the subject to the image sensor part 34; and another light path length altering member 42 that is arranged on the light path from the reference chart KC to the image sensor part 34 and whose light path length altering extent is different from that of the light path length altering member 41.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an imaging apparatus, a colorimetric apparatus, a colorimetric system, and an image forming apparatus, and more particularly to an imaging apparatus, a colorimetric apparatus, a colorimetric system, and an image forming apparatus that stably image a subject and a reference chart.

  Image forming apparatuses such as color ink jet type image forming apparatuses and color electrophotographic image forming apparatuses are offset by advertising media and pamphlets that require a high image but a relatively small number of copies as the image quality improves. It is also used for printing.

  In offset printing that requires high image quality, the color of the printed matter requested by the customer may differ from the color of the print output result that is actually printed out by the image forming apparatus.

  Usually, the customer confirms the color of the printed matter on the display and places an order for printing. However, each image forming apparatus has a color reproduction characteristic specific to each model, which is different from the color confirmed on the display. May result in printing.

  Therefore, conventionally, a technique for performing color reproduction using a color space that does not depend on a device such as a display or an image forming apparatus, such as a Lab color space or an xyz color space, has been used.

  The image forming apparatus controls the amount of color material and the like in order to output a specified color. For example, in an ink jet image forming apparatus, the output color is controlled by controlling the amount of ink discharged from the ink head by calculating and controlling the amount of ink discharged and the print pattern. In the image forming apparatus, the output color is controlled by controlling the amount of toner adhering to the photosensitive member, the amount of laser beam, and the like.

  However, the amount of the color material, for example, the ink discharge amount of the ink jet image forming apparatus varies depending on the state of the nozzle of the head, the viscosity of the ink, the variation of the discharge drive elements (piezo elements, etc.), Variation in color reproducibility occurs. Further, the ink ejection amount of the ink jet type image forming apparatus changes with time in one image forming apparatus or varies for each image forming apparatus. In other words, variations in the color reproduction of the image occur.

  Therefore, conventionally, in an image forming apparatus, color adjustment processing is performed in order to suppress output variations due to characteristics unique to the device and to improve output reproducibility with respect to input. In this color adjustment processing, for example, first, an image of a reference color patch (reference color patch image) is actually output by the image forming apparatus, and the reference color patch image is measured by the color measurement device. Then, a color conversion parameter is generated based on the difference between the colorimetric value of the reference color patch image measured by the colorimetry device and the colorimetric value of the corresponding reference color in the standard color space, and the color conversion parameter is Set in the image forming apparatus. After that, when outputting an image according to the input image data, the image forming apparatus performs color conversion on the input image data based on the set color conversion parameter, and after color conversion is performed. By recording and outputting an image based on the image data, an output of an image with high color reproducibility can be achieved by suppressing output variations due to characteristics unique to the device.

  In this conventional color adjustment processing, a spectral colorimeter is widely used as a color measuring device for measuring a reference color patch image, and the spectral colorimeter can obtain a spectral reflectance for each wavelength. Therefore, highly accurate colorimetry can be performed. However, since the spectrocolorimeter is an expensive device equipped with a large number of sensors, it is desired to perform highly accurate color measurement using a cheaper device.

  Conventionally, reference colorimetric means for measuring a reference color chart in advance in order to obtain color reference values as RGB data, and an object including the reference color chart and a color-measurement object are imaged simultaneously or separately. Color image input means for obtaining data, image extraction means for extracting RGB data of the reference color chart and RGB data of the color to be measured from RGB data obtained by the color image input means, and the image extraction means The difference between the RGB data of the reference color chart obtained in step 1 and the RGB data of the reference color chart obtained by the reference color measurement means is obtained, and at least the RGB data of the color to be measured is corrected using this difference. There has been proposed a colorimetric device characterized by comprising a calculation means (see Patent Document 1). In this conventional technique, a reference color chart to be compared with the subject is placed near the subject to be colorimetric, and the subject and the reference color chart are simultaneously imaged by a color video camera as a color image input means. In addition, it is disclosed that the RGB data of the subject is corrected using the RGB data of the reference color chart obtained by imaging, and the RGB data of the subject is converted into color values in the standard color space.

  However, in the prior art described in the above publication, it is difficult to keep the positional relationship between the reference color chart to be imaged as a subject to be compared and the color image input means constant for each imaging, and the imaging conditions for each imaging Fluctuates and there is a problem that it is difficult to perform stable imaging.

  Accordingly, an object of the present invention is to always capture an image of a subject and a reference chart with a stable positional relationship.

  In order to achieve the above object, an imaging unit according to claim 1 includes a two-dimensional sensor that images a subject through an opening, the two-dimensional sensor together with the subject, and the center of the two-dimensional sensor. A reference chart disposed on a side different from the opening, and a first light transmission member disposed in an optical path connecting at least the two-dimensional sensor and the reference chart.

  According to the present invention, the subject and the reference chart can always be imaged with a stable positional relationship.

1 is a schematic perspective view of an image forming apparatus to which an embodiment of the present invention is applied. The top view of a carriage part. FIG. The top view of an imaging part. AA arrow sectional drawing of the imaging part of FIG. BB arrow sectional drawing of the imaging part of FIG. The top view of a reference | standard chart. FIG. 3 is a block diagram of a main part of the image forming apparatus. The block block diagram of an imaging part and a colorimetry control part. Explanatory drawing of the acquisition process of the reference | standard colorimetry value and imaging reference RGB value from a reference | standard sheet, and a reference value linear transformation matrix acquisition process. The figure which shows an example of the image data which imaged the reference | standard chart and the imaging target simultaneously. The figure which shows an example of an initial reference RGB value. Explanatory drawing of a colorimetry process. Explanatory drawing of a reference | standard RGB substitution linear transformation matrix production | generation process. The figure which shows the relationship between an initial reference | standard RGB value and the reference | standard RGB value at the time of colorimetry. Explanatory drawing of a basic colorimetry process. FIG. 17 is a diagram showing basic colorimetry processing continued from FIG. 16. The top view of another imaging part. AA arrow sectional drawing of the imaging part of FIG. BB arrow sectional drawing of the imaging part of FIG. Furthermore, front sectional drawing of another imaging part. AA arrow sectional drawing of FIG. FIG. 2 is a block diagram of a main part of an image forming system to which a color measurement system is applied.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 21 are diagrams illustrating an embodiment of an imaging apparatus, a color measurement apparatus, a color measurement system, and an image forming apparatus according to the present invention. FIG. 1 illustrates an imaging apparatus, a color measurement apparatus, and a color measurement according to the present invention. 1 is a schematic perspective view of an image forming apparatus 1 to which an embodiment of a system and an image forming apparatus is applied.

  In FIG. 1, an image forming apparatus 1 has a main body housing 2 disposed on a main body frame 3, and a main guide rod in the main scanning direction indicated by a double arrow A in FIG. 4 and the auxiliary guide rod 5 are stretched over. The main guide rod 4 movably supports the carriage 6, and the carriage 6 is provided with a connecting piece 6 a that engages with the sub guide rod 5 to stabilize the posture of the carriage 6.

  In the image forming apparatus 1, an endless belt-like timing belt 7 is disposed along a main guide rod 4, and the timing belt 7 is stretched between a driving pulley 8 and a driven pulley 9. The driving pulley 8 is rotationally driven by the main scanning motor 10, and the driven pulley 8 is disposed in a state in which a predetermined tension is applied to the timing belt 7. The driving pulley 8 is rotationally driven by the main scanning motor 10 to rotate and move the timing belt 7 in the main scanning direction according to the rotation direction.

  The carriage 6 is connected to a timing belt 7, and is reciprocated in the main scanning direction along the main guide rod 4 when the timing belt 7 is rotationally moved in the main scanning direction by the drive pulley 8.

  The image forming apparatus 1 houses a cartridge unit 11 and a maintenance mechanism unit 12 at both end positions in the main scanning direction in the main body housing 2, and the cartridge unit 11 includes yellow (Y), magenta (M), and cyan. (C) and the cartridge which each accommodates each ink of black (K) is accommodated so that replacement | exchange is possible. Each cartridge of the cartridge unit 11 is connected to recording heads 20y, 20m, 20c, and 20k (see FIG. 2) of the corresponding color of the recording head 20 mounted on the carriage 6 by pipes (not shown), and from the cartridges through the pipes. Ink is supplied to the recording heads 20y, 20m, 20c, and 20k. In the following description, the recording heads 20y, 20m, 20c, and 20k are collectively referred to as the recording head 20.

  As will be described later, the image forming apparatus 1 moves on the platen 14 (see FIG. 2) in the sub-scanning direction (arrow B direction in FIG. 1) perpendicular to the main scanning direction while moving the carriage 6 in the main scanning direction. By ejecting ink onto the recording medium P that is intermittently conveyed, an image is recorded on the recording medium P.

  That is, the image forming apparatus 1 of the present embodiment intermittently conveys the recording medium P in the sub-scanning direction, and moves the carriage 6 in the main scanning direction while the conveyance of the recording medium P in the sub-scanning direction is stopped. While moving, ink is ejected from the nozzle array of the recording head 20 mounted on the carriage 6 onto the recording medium P on the platen 14 to form an image on the recording medium P.

  The maintenance mechanism unit 11 performs cleaning of the ejection surface of the recording head 20, capping, ejection of unnecessary ink, and the like to discharge unnecessary ink from the recording head 20 and maintain the reliability of the recording head 20. Yes.

  The image forming apparatus 1 is provided with a cover 13 that can open and close the conveyance part of the recording medium P. When the image forming apparatus 1 is maintained or when a jam occurs, the cover 13 is opened so that the inside of the main body housing 2 can be opened. Maintenance work, removal of the jam recording medium P, and the like can be performed.

  As shown in FIG. 2, the carriage 6 is mounted with recording heads 20y, 20m, 20c, and 20k. The recording heads 20y, 20m, 20c, and 20k are piped to the cartridges of the corresponding colors of the cartridge unit 11, respectively. Are connected to each other, and inks of corresponding colors are ejected onto the opposing recording medium P. That is, the recording head 20y is yellow (Y) ink, the recording head 20m is magenta (M) ink, the recording head 20c is cyan (C) ink, and the recording head 20k is black (K) ink. Discharge each.

  The recording head 20 is mounted on the carriage 6 so that its discharge surface (nozzle surface) faces downward (recording medium P side) in FIG. 1, and discharges ink onto the recording medium P.

  In the image forming apparatus 1, an encoder sheet 15 is disposed in parallel with the timing belt 7, that is, the main guide rod 5, over at least the movement range of the carriage 6. The encoder 6 reads the encoder sheet 15 on the carriage 6. A sensor 21 is attached. The image forming apparatus 1 controls the movement of the carriage 6 in the main scanning direction by controlling the driving of the main scanning motor 10 based on the reading result of the encoder sheet 15 by the encoder sensor 21.

  As shown in FIG. 3, the recording head 20 mounted on the carriage 6 includes recording nozzles 20 y, 20 m, 20 c, and 20 k configured by a plurality of nozzle rows, and is recorded on the platen 14. An image is formed on the recording medium P by ejecting ink from the nozzle rows onto the medium P. In the image forming apparatus 1, the upstream recording head 20 and the downstream recording head 20 are mounted on the carriage 6 in order to ensure a wide width of an image that can be formed on the recording medium P by one scan of the carriage 6. ing. In addition, the recording head 20k that discharges black ink has twice the number of recording heads 20y, 6m, and 6c that discharge color ink mounted on the carriage 6 in order to improve the black printing speed. Further, the recording heads 20y and 6m are arranged adjacent to each other in the main scanning direction so that the colors overlap in the reciprocating operation of the carriage 6 and the color does not change between the forward path and the backward path. Therefore, the arrangement of the recording heads 20y, 20m, 20c, and 20k of the recording head 20 is not limited to the arrangement shown in FIG.

  As shown in FIG. 2, an imaging unit (imaging device) 30 is attached to the carriage 6, and the imaging unit 30 performs colorimetry on a subject (colorimetric object) during color adjustment processing described later. Shoot the subject.

  As shown in FIG. 4 which is a plan view, FIG. 5 which is a cross-sectional view taken along the line AA in FIG. 4 and FIG. 6 which is a cross-sectional view taken along the line BB in FIG. A rectangular box-shaped frame 32 having an open surface on the side of the substrate 31 is fixed by a fastening member 33, and the substrate 31 is fixed to the carriage 6 shown in FIG. The frame body 32 is not limited to a rectangular box shape, and may be, for example, a cylindrical box shape having a bottom surface portion 32a in which openings 32b and 32c are formed, an elliptical cylinder box shape, or the like. .

  The imaging unit 30 is a surface of the substrate 31 on the frame 32 side, and an image sensor unit 34 is disposed at the center thereof. The image sensor unit (sensor means) 34 is a CCD (Charge Coupled Device) sensor. And a two-dimensional image sensor 35 such as a CMOS (Complementary Metal Oxide Semiconductor) sensor and a lens 36.

  In the imaging unit 30, the frame 32 has a lower surface of a surface portion (hereinafter referred to as a bottom surface portion) 32 a opposite to the substrate 31 facing the recording medium P on the platen 14 with a predetermined distance d. In the state, it is attached to the carriage 6, and the bottom surface portion (opposing surface) 32a is formed with a substantially rectangular opening portion 32b and an opening portion 32c in the main scanning direction centered on the center line Lo. . As will be described later, the gap d is preferably smaller in consideration of the focal length with respect to the two-dimensional image sensor 35. However, due to the flatness of the recording medium P, the lower surface of the frame 32 and the recording medium P are separated from each other. The size which does not contact, for example, is set to about 1 mm to 2 mm.

  As will be described later, the opening 32b includes a reference color patch KP (see FIG. 10) and a colorimetric adjustment sheet CS of the reference sheet KS (see FIG. 10) that is an imaging target (subject) formed on the recording medium P. This is used to image the colorimetric adjustment color patch CP (see FIG. 5) of (see FIG. 5). The opening 32b may be at least large enough to capture all images to be imaged. However, since there is a gap d between the frame 32 and the object to be imaged, a shadow generated around the opening 32b is generated. Considering this, it is formed in an opening state that is slightly larger than the size of the imaging region to be imaged.

  In the opening 32c, a concave portion 32d having a predetermined width is formed on the surface of the recording medium P along the periphery of the opening 32c, and the reference chart KC is detachably set in the concave portion 32d. A holding plate 32e that covers the surface of the reference chart KC on the recording medium P side and is held by the reference chart KC is provided in the recess 32d of the opening 32c of the frame 32 in a detachable manner. 32c is in a state of being blocked by the reference chart KC and the holding plate 32e. The holding plate 32e has a smooth flat surface on the recording medium P side.

  The reference chart KC is compared with the reference color patch KP of the reference sheet KS and the imaged colorimetric value of the colorimetric adjustment color patch CP of the colorimetric adjustment sheet CS which is the image pickup object in the color adjustment process. Photographed at the same time as the reference color patch KP and the colorimetric adjustment color patch CP. That is, the imaging unit 30 includes the reference color patch KP of the reference sheet KS and the colorimetric adjustment color patch of the colorimetry adjustment sheet CS that are located outside the frame 32 through the opening 32b provided in the bottom surface part 32a of the frame 32. Simultaneously with the imaging of the CP, the color patch on the reference chart KC attached to the recess 32d formed around the opening 32c of the bottom surface portion 32a of the frame 32 is imaged as a comparison target.

  Note that the imaging unit 30 scans pixels sequentially and reads an image, so strictly speaking, the reference color patch KP of the reference sheet KS and the colorimetric adjustment patch CP of the colorimetric adjustment sheet CS and the reference are strictly speaking. Although the chart KC is not read at the same time, the image of the reference color patch KP, the colorimetric adjustment patch CP, and the reference chart KC can be acquired within one frame.

  As shown in FIG. 7, the reference chart KC has a plurality of reference color patch rows Pa to Pd and dots for color measurement on the inner surface (upper surface) of the frame 32, as shown in FIG. A diameter measurement pattern row Pe, a distance measurement line lk, and a chart position specifying marker mk are formed.

  The color measurement patch rows Pa to Pd include a patch row Pa in which YMC primary color patches are arranged in gradation order, a patch row Pa in which RGB secondary color patches are arranged in gradation order, and a gray color. There are a patch array (achromatic gradation pattern) Pc in which patches of a scale are arranged in order of gradation, and a patch array Pd in which patches of a tertiary color are arranged, and the dot diameter measurement pattern array Pe has a size. It is a pattern sequence for measuring a geometric shape in which different circular patterns are arranged in order of size.

  The distance measurement line lk is formed as a rectangular frame surrounding the color measurement patch rows Pa to Pd and the dot diameter measurement pattern row Pe. The chart position specifying markers mk are provided at the positions of the four corners of the distance measuring line lk, and are markers for specifying each patch position.

  The color measurement control unit 106 (see FIGS. 8 and 9) described later specifies the distance measurement line lk and the chart position specifying markers mk at the four corners from the image data of the reference chart KC acquired from the imaging unit 30. The position of the reference chart KC and the position of each pattern are specified.

  Each patch constituting the reference color patch rows Pa to Pd for colorimetry is a Lab color that is a standard color space using a spectroscope BS (see FIG. 10), similarly to a reference patch KP of a reference chart KC described later. A colorimetric value (Lab value) in the space is measured in advance, and becomes a reference value when measuring a colorimetric adjustment color patch CP of a colorimetric adjustment sheet CS described later.

  The configuration of the colorimetric patch rows Pa to Pd arranged in the reference chart KC is not limited to the arrangement example shown in FIG. 7, and any patch row can be used. As long as possible, a patch capable of specifying a wide color range may be used, and the YMCK primary color patch row Pa and the gray scale patch row Pc may be used for the ink used in the image forming apparatus 1. It may be composed of patches of colorimetric values. Further, the RGB secondary color patch row Pa of the reference chart KC may be composed of patches of colorimetric values that can be developed with ink used in the image forming apparatus 1, and further, colorimetric values such as JapanColor. May be used.

  Since the reference chart KC is disposed in the concave portion 32d formed on the outer periphery of the surface on the recording medium P side of the opening 32c formed in the bottom surface portion 32a of the frame 32, the reference chart KC such as the recording medium P or the like. Images can be taken by the two-dimensional image sensor 35 of the image sensor unit 34 at the same focal length as that of the imaging target.

  Further, the reference chart KC is detachably set in the recess 32d formed on the outer periphery of the surface on the recording medium P side of the opening 32c formed in the bottom surface portion 32a of the frame 32, and the recording medium P Since the side surface is detachably held by the holding plate 32e that is detachably attached to the recess 32d, even if dust or the like entering the frame 32 adheres to the surface of the reference chart KC After the plate 32e and the reference chart KC are removed and the reference chart KC is cleaned cleanly, it can be attached again, and the measurement accuracy of the reference chart KC can be improved.

  4 to 6 again, the imaging unit 30 is on a center line Lo in the sub-scanning direction passing through the center of the image sensor unit 34, and is a predetermined amount in the direction from the image sensor unit 34 to the bottom surface part 32a. A pair of illumination light sources 37 are disposed at positions separated from each other by a predetermined amount in the sub-scanning direction from the center of the image sensor unit 34, and each of the illumination light sources 37 is an image. By being attached to the surface of the light source support member 38 that is fixed to the frame body 32 or as a part of the frame body 32 at a position that is a predetermined amount away from the sensor section 34 in the direction of the bottom surface section 32a, It is supported by the light source support member 38. As the illumination light source 37, an LED (Light Emitting Diode) or the like is used.

  The imaging unit 30 is provided with an optical path length changing member (subject optical path length changing member) 41 in the optical path between the recording medium P and the two-dimensional image sensor 35 through the opening 32b. An optical path length changing member (reference chart optical path length changing member) 42 is disposed in the optical path between the KC and the two-dimensional image sensor 35. The optical path length changing member 41 and the optical path length changing member 42 are fixed to the frame body 32 or formed as a part of the frame body 32 at a position where the upper surface of the light source support member 38 that supports the illumination light source 37 substantially coincides with the upper surface. It is hold | maintained by attaching to the holding member 43 and the holding member 44 which were made, respectively. That is, the optical path length changing member 41 and the optical path length changing member 42 are substantially intermediate positions between the image sensor portion 34 and the bottom surface portion 32a, and the recording medium P and the two-dimensional image sensor 35 that pass through the opening portion 32b. And the optical path between the reference chart KC and the two-dimensional image sensor 35, respectively.

  Further, as shown in FIG. 5, the optical path length changing member 41 and the optical path length changing member 42 are formed by the holding member 43 and the holding member 44 in a state where the bottom surface 32a side surface which is the lower surface thereof is located on the same plane. Is retained.

  As shown in FIG. 5, the optical path length changing member 41 and the optical path length changing member 42 have a refractive index n1 and a refractive index n2, respectively, and have a length in the light transmission direction (hereinafter referred to as the length of the optical path length changing member). .) Light transmission members having Lp1 and Lp2 are used, and the optical path lengths determined by the following expressions (1) and (2) based on the refractive indexes n1 and n2 and the lengths Lp1 and Lp2 in the light transmission direction, respectively. The amount of change (the amount of rising of the image) C1 and C2 is included. That is, the optical path length changing unit 41 and the optical path length changing unit 42 have different optical path length changing amounts.

C1 = Lp1 (1-1 / n1) (1)
C2 = Lp2 (1-1 / n2) (2)
The optical path length (focal length) L1 from the imaging surface of the recording medium P to the image sensor unit 34 and the optical path length (focal length) L2 from the reference chart KC to the image sensor unit 3 are expressed by the following equations (3) and (4). ).

L1 = Lt + Lp1 (1-1 / n1) (3)
L2 = Lc + Lp2 (1-1 / n2) (4)
Here, Lt is the distance between the top on the imaging target side of the lens 36 and the imaging surface of the recording medium P, and Lc is the distance between the top on the imaging target side of the lens 36 and the reference chart KC.

  The imaging unit 30 then matches the optical path length (focal length) L1 from the imaging surface of the recording medium P to the image sensor unit 34 with the optical path length (focal length) L2 from the reference chart KC to the image sensor unit 3. The refractive index n1 and length Lp1 of the optical path length changing member 41 and the refractive index n2 and length Lp2 of the optical path length changing member 42 are set. By setting in this way, the focal position of the reference chart KC with respect to the image sensor unit 34 and the focal position of the subject (imaging surface) can be matched.

  Further, the imaging unit 30 uses the same illumination for the illumination light that irradiates the imaging surface of the recording medium P through the optical path length changing member 41 and the opening 32b and the illumination light that irradiates the reference chart KC through the optical path length changing member 42. Illumination light from the light source 37, and the reference chart KC and the imaging surface of the recording medium P can be imaged simultaneously under the same illumination conditions. In addition, the illumination light source 37 is disposed on the center line Lo which is a substantially intermediate position between the reference chart KC and the recording medium P, and two illumination light sources 37 are disposed on the center line Lo with respect to the lens 36. The imaging area of the reference chart KC and the recording medium P can be illuminated uniformly under substantially the same illumination conditions.

  Furthermore, since the imaging unit 30 is arranged substantially symmetrically with respect to the center line Lo connecting the center of the lens 36 and the illumination light source 37, the arrangement condition of the aperture 32b of the imaging region and the reference chart KC is two-dimensional. The imaging conditions of the image sensor 35 can be made line symmetrical and the same, and the accuracy of color adjustment processing and color measurement processing of the two-dimensional image sensor 35 using the reference chart KC can be improved.

  The image forming apparatus 1 of the present embodiment is configured as a block as shown in FIG. 8, and includes a central processing unit (CPU) 101, a read only memory (ROM) 102, a random access memory (RAM) 103, and main scanning. A driver 104, a recording head driver 105, a colorimetric control unit 106, a paper conveying unit 107, a sub-scanning driver 108, and the like are provided, and the recording head 20, the encoder sensor 21, and the imaging device mounted on the carriage 6 as described above. Part 30 and the like.

  The ROM 102 stores programs such as a basic program and a color adjustment processing program as the image forming apparatus 1 and necessary system data. The CPU 101 uses the RAM 103 as a work memory based on the program in the ROM 102, and performs image processing. The respective units of the forming apparatus 1 are controlled to execute basic processing as the image forming apparatus 1 and, at the same time, the colorimetric processing obtained by the colorimetric processing by the colorimetric control unit 106 based on the RGB values captured by the imaging unit 30. Based on the color value, color adjustment processing at the time of image formation is executed.

  In the control of the carriage 6 and the paper transport unit 107, the CPU 101 controls the driving of the main scanning driver 104 based on the encoder value from the encoder sensor 21, and controls the movement of the carriage 6 in the main scanning direction. The CPU 101 controls driving of a paper transport unit 107 such as a sub-scan motor and a transport roller (not shown) via a sub-scan driver 108. Further, the CPU 101 controls the ink ejection timing and the ink ejection amount by the recording head 20 via the recording head driver 105. In addition, the CPU 101 controls the lighting drive of the illumination light source 37 of the imaging unit 30 via the color measurement control unit 106.

  As described above, the imaging unit 30 generates a colorimetric value for color adjustment that accurately reproduces the color of image data when recording and outputting an image to a color intended by the user, as will be described later. The color measurement adjustment patch CP formed by the recording head 20 on the recording medium P is imaged at the time of color measurement, and the captured RGB values are output to the CPU 101.

  The imaging unit 30 and the colorimetric control unit 106 are configured as a block as shown in FIG. The imaging unit 30 includes the illumination light source 37 and the image sensor unit 34, and also includes an image processing unit 110, an interface unit 111, and the like. The image processing unit 110 includes an A / D conversion unit 112, a shading correction unit, and the like. 113, a white balance correction unit 114, a γ correction unit 115, and an image format conversion unit 116.

  The imaging unit 30 outputs analog RGB image data obtained by the image sensor unit 34 simultaneously capturing the subject and the reference chart KC to the image processing unit 110, and the image processing unit 110 receives the analog RGB image data sent from the image sensor unit 34. Necessary image processing is performed on the RGB image data and output to the colorimetric control unit 106.

  The A / D conversion unit 112 of the image processing unit 110 digitally converts analog RGB image data input from the image sensor unit 34 and outputs the converted data to the shading correction unit 113.

  The shading correction unit 113 corrects the error of the image data caused by the illuminance unevenness of the illumination light from the illumination light source 37 with respect to the imaging range of the image sensor unit 34 with respect to the RGB image data input from the A / D conversion unit 112. And output to the white balance correction unit 114.

  The white balance correction unit 114 corrects the white balance of the RGB image data after the shading correction, and outputs the corrected data to the γ correction unit 115.

  The γ correction unit 115 corrects the image data input from the white balance correction unit 114 so as to compensate for the linearity of the sensitivity of the image sensor unit 34 and outputs the corrected data to the image format conversion unit 116.

  The image format conversion unit 116 converts the image data after γ correction into an arbitrary format, and outputs it to the colorimetry control unit 106 via the interface unit 111.

  The interface unit 111 is used for the imaging unit 30 to acquire various setting signals, timing signals, and light source drive signals sent from the colorimetry control unit 106, and to send image data from the imaging unit 30 to the colorimetry control unit 106. Interface.

  The color measurement control unit 106 includes a frame memory 121, a timing signal generation unit 122, a light source drive control unit 123, a calculation unit 124, and a nonvolatile memory 125. The calculation unit 124 includes a color measurement value calculation unit 126. Yes.

  The frame memory 121 is a memory that temporarily stores the image data sent from the imaging unit 30, and outputs the stored image data to the calculation unit 124.

  As shown in FIG. 10, the non-volatile memory 125 includes Lab values that are colorimetric values of colorimetric results of a plurality of reference color patches KP arrayed on the reference sheet KS by the spectroscope (colorimetry device) BS. And at least one of the XYZ values (both Lab and XYZ values in FIG. 10) are stored as reference colorimetric values in the memory table Tb1 of the nonvolatile memory 125 in correspondence with the patch numbers.

  Further, the image forming apparatus 1 stores the reference sheet KS of the image forming apparatus 1 in a state where the reference colorimetric values are stored in the nonvolatile memory 125 in the memory table Tb1 and in the initial state of the image forming apparatus 1. An imaging reference RGB value obtained by reading the same reference patch KP as that read by the spectroscope BS of the reference sheet KS by the imaging unit 30 by controlling the movement of the carriage 6 by being set on the platen 14 is stored in the nonvolatile memory 125. Is stored in the memory table Tb1 in correspondence with the patch number, that is, in correspondence with the reference colorimetric value, and each patch of the reference chart KC of the imaging unit 30 is imaged to obtain the RGB value. The RGB value of each patch in the chart KC is set as the initial reference RGB value RdGdBd, and the memory table of the nonvolatile memory 125 is controlled under the control of the calculation unit 124. It is stored in Le Tb1.

  When the image forming apparatus 1 stores the reference colorimetric value, the imaging reference RGB value, and the initial reference RGB value RdGdBd in the nonvolatile memory 125, the colorimetric value calculation unit 126 stores the reference colorimetry stored in the nonvolatile memory 125. A reference value linear conversion matrix for mutual conversion is calculated for a pair of XYZ values and imaging reference RGB values, that is, a pair of XYZ values and imaging reference RGB values of the same patch number, and the calculated reference value linear The conversion matrix is stored in the nonvolatile memory 125.

  In the image forming apparatus 1, the above processing is executed in the initial state of the image forming apparatus 1, and the reference colorimetric values, imaging reference RGB values, and initial reference RGB values RdGdBd as execution results are stored in the memory table Tb 1 of the nonvolatile memory 125. Then, a reference value linear transformation matrix is calculated and stored in the nonvolatile memory 125.

  Further, as will be described later, the image forming apparatus 1 according to the present exemplary embodiment includes a color measurement adjustment color patch CP and a frame as a subject formed on the recording medium P by the recording head 20 that changes with time during color adjustment processing. The reference chart KC disposed inside the body 32 is simultaneously imaged by the image sensor unit 34, and image data including the colorimetric adjustment color patch CP and the reference chart KC is output to the colorimetry control unit 106. The color measurement control unit 106 uses the color measurement adjustment color patch CP captured by the image sensor unit 34 during the color adjustment processing acquired from the imaging unit 30 as a reference color patch (hereinafter referred to as an initial reference color patch) of the reference sheet KS. When the image is read by the imaging unit 30, after being converted into the initial reference RGB values RdGdBd of the patches Pa to Pe of the reference chart KC read and stored at the same time, the colorimetric adjustment patch CP of the initial reference RGB values RdGdBd A portion having linearity is taken out and subjected to linear conversion to perform colorimetric processing for obtaining a colorimetric value.

  That is, the arithmetic unit 124 controls the operation of the colorimetric control unit 106, and the colorimetric value calculation unit 126 executes the colorimetric processing and outputs the colorimetric values that are the results of the colorimetric processing to the CPU 101. Then, the CPU 101 performs color adjustment processing on the image data using the colorimetric value, and controls the recording head 20 based on the color adjustment processed image data, thereby forming an image with improved color reproducibility. To do.

  The image forming apparatus 1 of this embodiment includes a ROM, an EEPROM (Electrically Erasable and Programmable Read Only Memory), an EPROM, a flash memory, a flexible disk, a CD-ROM (Compact Disc Read Only Memory), and a CD-RW (Compact Disc Rewritable). A color measurement program for executing the color measurement method of this embodiment recorded on a computer-readable recording medium such as a DVD (Digital Versatile Disk), an SD (Secure Digital) card, or an MO (Magneto-Optical Disc). It is constructed as an image forming apparatus 1 equipped with a color measuring device that executes a color measuring method that realizes color reproducibility described later at low cost and stably by reading and introducing it into the ROM 102 or the nonvolatile memory 125 or the like. . This color measurement program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark) or an object-oriented programming language, and is stored in the recording medium. Can be distributed.

  Next, the operation of this embodiment will be described. The image forming apparatus 1 of the present embodiment executes a color measurement method that realizes color reproducibility inexpensively and stably.

  As shown in FIG. 10, the image forming apparatus 1 according to the present embodiment uses the spectroscope BS to calculate the color measurement results of a plurality of reference color patches arranged and formed on the reference sheet KS, among Lab values and XYZ values. , At least one of them is stored as a reference colorimetric value corresponding to the patch number in the memory table Tb1 of the nonvolatile memory 125.

  Further, when the image forming apparatus 1 is in a state where the reference colorimetric values are stored in the nonvolatile memory 125 in the memory table Tb1 and the image forming apparatus 1 is in an initial state due to manufacture, overfall, or the like, The reference sheet KS is set on the platen 14 of the image forming apparatus 1, the movement of the carriage 6 is controlled, and the same reference patch as read by the spectroscope BS of the reference sheet KS is read by the imaging unit 30, and at the same time As shown in FIG. 11, each patch (initial reference color patch) of the reference chart KC arranged inside the frame 32 is imaged.

  When the image forming apparatus 1 captures the reference patch of the reference sheet KS and each patch of the reference chart KC by the imaging unit 30, the image forming apparatus 1 has RGB values obtained by processing the image data obtained by capturing the reference patch of the reference sheet KS by the image processing unit 110. As shown in FIG. 10, the calculation unit 124 of the color measurement control unit 106 associates the imaging reference RGB values, that is, device-dependent signals, with the patch numbers in the memory table Tb1 of the nonvolatile memory 125. That is, the initial reference RGB value RdGdBd, which is the RGB value obtained by reading the initial reference color patch of the reference chart KC and processing it by the image processing unit 110 while storing it in correspondence with the reference colorimetric value, is shown in FIG. As shown in FIG.

  The calculation unit 124 calculates an average value for each predetermined region, for example, a region (color measurement target region) indicated by a broken line in FIG. 11 among the image data of the initial reference color batch of the reference chart KC read by the imaging unit 30. The initial reference RGB value RdGdBd is calculated. When the initial reference RGB value RdGdBd is calculated by averaging a large number of pixels in the colorimetric object region in this way, the influence of noise can be reduced and the bit resolution can be improved. FIG. 12B is a scatter diagram in which the initial reference RGB value RdGdBd is plotted. FIG. 12A is a reference Lab value Lddbdd and XYZ values obtained by converting the initial reference RGB value RdGdBd into Lab values. The reference XYZ value xdydzd also indicates a state registered in the nonvolatile memory 125.

  When the image forming apparatus 1 stores the reference colorimetric value, the imaging reference RGB value, and the initial reference RGB value RdGdBd in the nonvolatile memory 125, the colorimetric value calculation unit 126 of the calculation unit 124 is stored in the nonvolatile memory 125. Calculate a reference value linear conversion matrix for mutual conversion with respect to a pair of XYZ value and imaging reference RGB value of the reference colorimetric value, that is, a pair of XYZ value and imaging reference RGB value of the same patch number The reference value linear transformation matrix is stored in the nonvolatile memory 125.

  In this state, in the image forming apparatus 1, the CPU 101 controls the main scanning movement of the carriage 6, the conveyance control of the recording medium P by the paper conveyance unit 48, and the recording head based on image data input from the outside, print settings, and the like. 20, by controlling the ink ejection from the recording heads 20 y, 20 m, 20 c, and 20 k of the recording head 20 while intermittently transporting the recording medium P by controlling the drive of the recording medium 20, the image is recorded on the recording medium P To do.

  At this time, the amount of ink discharged from the recording heads 20y, 20m, 20c, and 20k may change depending on the characteristics unique to the device, changes with time, and the like. An image is formed with a color different from the color, and the color reproducibility deteriorates.

  Therefore, the image forming apparatus 1 executes color adjustment processing for obtaining a colorimetric value and performing color adjustment based on the colorimetric value at a predetermined color adjustment processing timing.

  That is, at the timing of color adjustment processing, the image forming apparatus 1 forms a plurality of color patches (color measurement adjustment color patches) CP on the recording medium P by the recording head 20 as shown in FIG. Recorded and output as a sheet CS. In this color measurement adjustment sheet CS, a plurality of color measurement adjustment color patches CP, which are color patches for color measurement adjustment, are formed and output by the recording head 20, and output at the color adjustment processing timing of the image forming apparatus 1. A colorimetric adjustment color patch CP reflecting the characteristics, particularly the output characteristics of the recording head 20 is formed. Note that the color patch data of the color measurement adjustment color patch CP is stored in advance in the nonvolatile memory 125 or the like.

  Then, as will be described later, the image forming apparatus 1 uses the RGB values obtained by imaging the plurality of color measurement adjustment color patches CP of the color measurement adjustment sheet CS as color measurement target RGB values (color measurement RGB values). A color object RGB value is converted into an initial reference RGB value RdGdBd, and among the reference colorimetric values registered in the memory table Tb1 of the nonvolatile memory 125, the initial reference RGB value RdGdBd is converted. A reference colorimetric value close to the distance (neighboring reference colorimetry value) is selected, and a colorimetric value for converting the colorimetric target RGB value into the selected neighborhood reference colorimetric value is obtained. Based on the colorimetric value Based on the image data after the color conversion, the recording head 20 outputs an image, thereby improving the color reproducibility of the image formed by the image forming apparatus 1.

  Therefore, as shown in FIG. 13, the image forming apparatus 1 sets the colorimetric adjustment sheet CS on the platen 14 or does not eject the colorimetric adjustment sheet CS when it is recorded. As the held state, the plurality of color measurement adjustment color patches CP of the color measurement adjustment sheet CS on the platen 14 are imaged by the imaging unit 30 while controlling the movement of the carriage 6 and at the same time, the imaging unit 30 captures the reference chart KC. Capture the patch. When the image forming apparatus 1 simultaneously captures the color measurement adjustment color patch CP of the color measurement adjustment sheet CS and the patch of the reference chart KC by the imaging unit 30, the image processing unit 110 of the imaging unit 30 performs the measurement of the color measurement adjustment sheet CS. After the necessary image processing is performed on the image data of the color adjustment color patch CP and the image data of the reference chart KC, the image data (RGB values) of the color measurement adjustment color patch CP of the color measurement adjustment sheet CS is obtained. The colorimetric target RGB values, that is, device-dependent signals depending on the device, and the image data (RGB values) of the patches of the reference chart KC are sent to the colorimetry control unit 106 as the colorimetric reference RGB values RdsGdsBds. As shown in FIG. 13, the color control unit 106 temporarily stores it in the frame memory 121 (step S11).

  The colorimetric control unit 106 uses the colorimetric value RGB value stored in the frame memory 121 by the colorimetric value calculation unit 126 of the calculation unit 124 to initialize the colorimetric object to be initialized using a reference RGB linear conversion matrix to be described later. Conversion into RGB values RsGsBs (steps S12 and S13).

  The calculation unit 124 of the colorimetry control unit 120 uses the converted initialization colorimetry target RGB value RsGsBs as the colorimetry target RGB value (step S14), executes basic colorimetry processing described later, and converts the Lab colorimetry values. Obtain (step S15).

  In the image forming apparatus 1 according to the present exemplary embodiment, the colorimetric value calculation unit 126 of the calculation unit 124 obtains the reference RGB linear conversion matrix as illustrated in FIGS. 14 and 15.

  That is, as shown in FIG. 14, the colorimetric value calculation unit 126 of the calculation unit 124 captures the patch of the reference chart KC at the same time when the imaging unit 30 images the reference color patch KP of the reference sheet KS at the initial stage. When the initial reference RGB value RdGdBd stored in the nonvolatile memory 125 and the color measurement adjustment color patch CP of the color measurement adjustment sheet CS are imaged by the imaging unit 30 during color measurement, the patch of the reference chart KC is simultaneously captured. Then, the colorimetric reference RGB value RdsGdsBds stored in the nonvolatile memory 125 is read from the nonvolatile memory 125, and the colorimetric reference RGB value RdsGdsBds is converted into the initial reference RGB value RdGdBd. , And the obtained reference RGB linear conversion matrix is stored in the nonvolatile memory 125.

  That is, in FIG. 15, the points indicated by white dots in FIG. 15A are points where the initial reference RGB values RdGdBd are plotted in the rgb space, and the fill points are the colorimetric reference RGB values RdsGdsBds as rgb. This is a point plotted in space. As can be seen from FIG. 15A, the value of the colorimetric reference RGB value RdsGdsBds fluctuates from the value of the initial reference RGB value RdGdBd, and the fluctuation direction in the rgb space is shown in FIG. 15B. As indicated by the arrows, the directions are generally the same, but the direction of deviation differs depending on the hue. As described above, the reason why the RGB values fluctuate even when the patches of the same reference chart KC are imaged includes a change with time of the illumination light source 37 and a change with time of the two-dimensional image sensor 35.

  As described above, the colorimetric values are obtained using the colorimetric RGB values obtained when the colorimetric adjustment patch CP of the colorimetry adjustment sheet CS is imaged in a state where the patches of the same reference chart KC are fluctuated. If it is obtained, there is a risk that an error will occur in the colorimetric value by the amount of variation.

  In view of this, the image forming apparatus 1 according to the present exemplary embodiment uses the estimation method such as the least square method between the initial reference RGB value RdGdBd and the colorimetric reference RGB value RdsGdsBds to initially set the colorimetric reference RGB value RdsGdsBds. A reference RGB linear conversion matrix to be converted into the reference RGB value RdGdBd is obtained, and the colorimetric adjustment color patch CP of the colorimetric adjustment sheet CS is imaged by the imaging unit 30 using the reference RGB linear conversion matrix, and the nonvolatile memory is obtained. The colorimetric object RGB values stored in 125 are converted into initialization colorimetry object RGB values RsGsBs, and the converted initial colorimetry object RGB values RsGsBs are used as colorimetry object RGB values to be described later. To obtain Lab colorimetric values.

  This linear conversion matrix between RGB may be not only a first-order but also a higher-order nonlinear matrix. If the nonlinearity is high between the rgb space and the XYZ space, a higher-order matrix can be obtained. , Conversion accuracy can be improved.

  When the imaging unit 30 captures the reference color patch KP of the reference sheet KS as the subject and the color measurement adjustment color patch CP of the color measurement adjustment sheet CS through the opening 32b formed in the bottom surface part 32a. At the same time, by imaging the patch of the reference sheet KS disposed in the opening 32c of the bottom surface portion 32a of the frame 32, the patch of the reference sheet KS is always the subject of the reference sheet KS with the same positional relationship. The reference color patch KP and the color measurement adjustment color patch CP of the color measurement adjustment sheet CS can be imaged, and the image can be captured in a stable state.

  Further, the imaging unit 30 includes an optical path length in the optical path between the reference color patch KP of the reference sheet KS as the subject and the color measurement adjustment color patch CP of the color measurement adjustment sheet CS and the two-dimensional image sensor 35 through the opening 32b. A changing member 41 is provided, and an optical path length changing member 42 is provided in the optical path between the reference chart KC and the two-dimensional image sensor 35. The imaging unit 30 includes an optical path length (focal length) L1 from the reference color patch KP of the reference sheet KS that is the imaging surface and the colorimetric adjustment color patch CP of the colorimetry adjustment sheet CS that is the subject to the image sensor unit 34 and the reference chart. The refractive index n1 and the length Lp1 of the optical path length changing member 41 and the refractive index n2 and the length Lp2 of the optical path length changing member 42 are set so that the optical path length (focal length) L2 from the KC to the image sensor unit 3 matches. Thus, the focus position of the reference chart KC with respect to the image sensor unit 34 and the focus position of the subject (the reference color patch KP of the reference sheet KS and the color measurement adjustment color patch CP of the color measurement adjustment sheet CS) can be matched.

  Therefore, the reference color patch KP of the reference sheet KS, the colorimetric adjustment color patch CP of the colorimetry adjustment sheet CS, and the reference chart KC to be compared between them are always stably imaged with high accuracy and the same accuracy. Can do.

  Further, the imaging unit 30 uses the same illumination for the illumination light that irradiates the imaging surface of the recording medium P through the optical path length changing member 41 and the opening 32b and the illumination light that irradiates the reference chart KC through the optical path length changing member 42. Illumination light from the light source 37, and the reference chart KC and the imaging surface of the recording medium P can be imaged simultaneously under the same illumination conditions. In addition, the illumination light source 37 is disposed on the center line Lo which is a substantially intermediate position between the reference chart KC and the recording medium P, and two illumination light sources 37 are disposed on the center line Lo with respect to the lens 36. The imaging area of the reference chart KC and the recording medium P can be illuminated uniformly under substantially the same illumination conditions.

  Furthermore, since the imaging unit 30 is arranged substantially symmetrically with respect to the center line Lo connecting the center of the lens 36 and the illumination light source 37, the arrangement condition of the aperture 32b of the imaging region and the reference chart KC is two-dimensional. The imaging conditions of the image sensor 35 can be made line symmetrical and the same, and the accuracy of color adjustment processing and color measurement processing of the two-dimensional image sensor 35 using the reference chart KC can be improved.

  Then, when the image forming apparatus 1 obtains the initial colorimetric target RGB value RsGsBs as described above and sets it as the colorimetric target RGB value, the memory table Tb1 of the nonvolatile memory 125 as shown in FIGS. Of the colorimetric values registered in the colorimetric object RGB values, the reference colorimetric values (neighboring reference colorimetric values) that are close in distance to the colorimetric values converted into the colorimetric object RGB values are selected and measured. A basic colorimetry process for obtaining a colorimetric value for converting a color target RGB value to a selected neighborhood reference colorimetric value is executed, and recording is performed based on image data after color conversion is performed based on the colorimetric value. By outputting an image by the head 20, the color reproducibility of the image formed by the image forming apparatus 1 is improved.

  That is, as shown in FIG. 16, the image forming apparatus 1 captures the color measurement adjustment color patch CP of the color measurement adjustment sheet CS, obtains the initial color measurement target RGB value RsGsBs as described above, and determines the color measurement target RGB. When stored in the nonvolatile memory 125 as a value (step S21), the reference value linear conversion matrix is used (step S22), converted into a first XYZ value (step S23), and stored in the nonvolatile memory 125 (step S22). S24). For example, in FIG. 16, the colorimetric value calculation unit 126 converts the colorimetric target RGB values (3, 200, 5) of the imaging unit 30 into the first XYZ values (first colorimetric values) of (20, 80, 10). And stored in the nonvolatile memory 125.

  The colorimetric value calculation unit 126 converts the first XYZ value into a first Lab value (first colorimetric value) by referring to the memory table Tb1 of the nonvolatile memory 125 or using a known conversion formula. (Step S25), stored in the nonvolatile memory 125 (Step S26). For example, in FIG. 16, the colorimetric value calculation unit 126 converts the first XYZ value (20, 80, 10) into the first Lab value (75, −60, 8) that is the imaged colorimetric value.

  Next, the colorimetric value calculation unit 126 searches for the reference colorimetric values (Lab values) of the color patches of the plurality of colors in the memory table Tb1 stored in the nonvolatile memory 125, as indicated by the Lab space in FIG. Then, a set of color patches (neighboring color patches) that are close in distance to the first Lab value in the Lab space is selected from the reference colorimetric values (Lab values) (step S27). For example, the Lab space diagram of FIG. 16 shows a diagram in which 60 color patches are selected and plotted on the Lab space. For example, the first Lab can be selected as a method for selecting a patch having a short distance. The distance between the value and all points in the reference colorimetric values (Lab values) of the plurality of color patches is calculated, and the reference Lab value of the color patch that is close to the first Lab value that is the first colorimetric value (see FIG. 16, the hatched reference Lab value) is selected.

  Next, as shown in FIG. 17, the colorimetric value calculation unit 126 refers to the memory table Tb1, and sets the imaging reference RGB values paired with the first Lab value of the selected set, that is, the first Lab of the selected set. A combination of an imaging reference RGB value (selected RGB value) and a reference XYZ value having the same patch number as is selected (step S28), and a combination of the imaging reference RGB and reference XYZ of the selected combination (selected set) is converted. The selected RGB value linear transformation matrix is obtained using the least square method, and the obtained selected RGB value linear transformation matrix is stored in the nonvolatile memory 125 (step S29).

  The colorimetric value calculation unit 126 captures the colorimetry target RGB values obtained by imaging each colorimetry adjustment color patch CP of the colorimetry adjustment sheet CS, which is a colorimetry target, by the image capturing unit 30 and digitally converting it by the A / D converter 36. A second XYZ value, which is a second colorimetric value, is obtained using the selected RGB value linear conversion matrix (step S30), and the second XYZ value is converted into a second Lab value using a known conversion formula (step S31). Obtained as a final colorimetric value (step S32).

  The colorimetric value calculation unit 126 performs image adjustment based on the image data that has been color-converted using the obtained colorimetric value, and drives the recording head 20 based on the image data that has undergone image adjustment to form an image.

  In other words, the image forming apparatus 1 according to the present embodiment captures and acquires a plurality of color measurement adjustment color patches CP of the color measurement adjustment sheet CS reflecting the output characteristics of the recording head 20 at the color adjustment processing timing. The RGB values of the colorimetric object are obtained by obtaining a first Lab value when the reference sheet KS is imaged in the initial state using a reference value linear conversion matrix, and among the reference Labs of a plurality of color patches registered in the memory table Tb1 A pair of patches with a reference Lab value that is close to the first Lab value in the Lab space is selected, and the colorimetric RGB values corresponding to the selected reference Lab value are selected using the selected RGB value linear conversion matrix. Thus, the Lab colorimetric value is obtained by converting it into a Lab value. Then, the colorimetric value calculation unit 126 performs image adjustment based on the image data subjected to color conversion using the obtained colorimetric value, and drives the recording head 20 based on the image data subjected to image adjustment to form an image. To do.

  In the above description, the imaging unit 30 is in a state where the surface (lower surface) on the bottom surface portion 32a side of the long optical path length changing member 41 having the length Lp1 and the short optical path length changing member 42 having the length Lp2 match. While being held by the holding member 43 and the holding member 44 and arranged in the frame 32, the arrangement state of the optical path length changing member is not limited to the above arrangement state.

  For example, as shown in FIG. 18 to FIG. 20 as the imaging unit 50, the optical path length changing member 42 and the optical path length changing member 41 are in a state where the upper surfaces thereof coincide with each other and between the image sensor unit 34 and the bottom surface part 32 a. It may be arranged closer to the image sensor unit 34 than. 18 to 20, the same reference numerals are given to the same components as those in FIGS. 4 to 6.

  18 to 20, the long optical path length changing member 41 having a length Lp1 is held by the holding member 51 at the end position on the image sensor unit 34 side, and the short optical path length changing member 42 having a length Lp2. Is held by the holding member 52 at the end position on the image sensor unit 34 side. The optical path length changing member 41 and the optical path length changing member 42 are disposed in such a manner that the surfaces facing each other are in contact with each other at a position directly below the image sensor unit 34, and the end surfaces on the image sensor unit 34 side are in agreement. And it is arrange | positioned in the position near the image sensor part 34 rather than the intermediate position of the image sensor part 34 and the bottom face part 32a. The imaging unit 50 is the same as the imaging unit 30 in other configurations.

  Accordingly, as shown in FIG. 19, the imaging unit 50 has a colorimetric adjustment color that has passed through the opening 32b even when the light incident / exit surfaces of the optical path length changing member 41 and the optical path length changing member 42 are small in area. The reflected light from the subject such as the patch CP and the reflected light from the reference chart KC that has passed through the opening 32c can be incident on the image sensor unit 34 by changing the optical path length, and the optical path length is made to coincide with the imaging unit 50. Can be miniaturized.

  The arrangement configuration of the optical path length changing member of the imaging unit is not limited to the above arrangement configuration. For example, as shown in FIG. 21 and FIG. 22 as the imaging unit 60, the reference chart KC and the image sensor unit The optical path length changing member 61 may be provided on the optical path between the optical sensor 34 and the optical path length changing member 62 may be provided on the optical path between the subject passing through the opening 32c and the image sensor unit 34. 21 and 22, the same components as those in FIGS. 4 to 6 are denoted by the same reference numerals, and the description thereof is omitted. 21 and 22, FIGS. 4 to 6 are shown in a state where the reference chart KC and the openings 32b and 32c for imaging the subject are interchanged.

  Also in this case, the optical path length changing member 61 and the optical path length changing member 62 have a refractive index n1 and a refractive index n2, respectively, as shown in FIG. When the lengths Lp1 and Lp2 are provided, the optical path length change amounts (image floating amounts) C1 and C2 determined by the above formulas (1) and (2) are provided. That is, the optical path length changing unit 41 and the optical path length changing unit 42 have different optical path length changing amounts.

  The optical path length (focal length) L1 from the reference chart KC to the image sensor unit 3 and the optical path length (focal length) L2 from the imaging surface of the recording medium P to the image sensor unit 34 are expressed by the above equations (3) and (4). ).

  That is, the imaging unit 60 is configured such that the optical path length (focal length) L1 from the reference chart KC to the image sensor unit 3 and the optical path length (focal length) L2 from the imaging surface of the recording medium P to the image sensor unit 34 match. The refractive index n1 and length Lp1 of the optical path length changing member 61 and the refractive index n2 and length Lp2 of the optical path length changing member 62 are set. By setting in this way, the focal position of the reference chart KC with respect to the image sensor unit 34 and the focal position of the subject (imaging surface) can be matched.

  Accordingly, the optical path length changing members 61 and 62 are disposed so as to block the reference chart KC imaging opening 32b and the subject imaging opening 32c formed in the frame 32 from the inside of the frame 32, respectively. Then, the focal length L1 to the recording medium P and the focal length L2 to the reference chart KC can be made the same, and intrusion of dust or the like into the frame 32 can be prevented, so that more accurate measurement can be performed. Color can be done.

  As described above, in the image forming apparatus 1 according to the present exemplary embodiment, the imaging unit (imaging device) 30 has the opening 32b and the opening for imaging the subject on the lower surface (opposing surface) 32a facing the subject. A predetermined box-shaped frame 32 provided with a reference chart KC that is imaged at the same time as a subject imaged through the unit 32b and provides a predetermined color reference in a predetermined direction; the subject and the reference chart KC And receiving the reflected light from the subject facing the opening 32b and the reflected light from the reference chart KC to simultaneously image the subject and the reference chart KC. And an optical path length changing member (for the subject) disposed in the optical path from the subject to the image sensor unit 34 and having a predetermined optical path length change amount. Path length changing member) 41 and an optical path length change amount which is disposed in the optical path from the reference chart KC to the image sensor unit 34 and whose optical path length change amount is different from the optical path length change amount of the optical path length changing member 41. A member (reference chart optical path length changing member) 42.

  Therefore, the subject and the reference chart KC can be imaged simultaneously and stably, and the optical path lengths of the subject and the reference chart KC with respect to the image sensor unit 34 can be appropriately adjusted. Highly accurate imaging can be performed with a stable positional relationship.

  The optical path length changing member 41 and the optical path length changing member 42 of the imaging unit 30 are such that the optical path length changing amount is an optical path length from the subject to the image sensor unit 34 of light that has passed through the optical path length changing member 41, and This is the optical path length change amount that makes the optical path length from the reference chart KC to the image sensor unit 34 of the light that has passed through the optical path length changing member 42 the same.

  Therefore, the optical path lengths of the subject and the reference chart KC with respect to the image sensor unit 34 can be made the same, and the subject and the reference chart KC can always be imaged with higher accuracy with a stable positional relationship.

  Furthermore, the optical path length changing member 41 and the optical path length changing member 42 of the imaging unit 30 are respectively disposed at a substantially intermediate position between the subject and the image sensor unit 34 and a substantially intermediate position between the reference chart KC and the image sensor unit 34. Yes.

  Therefore, the optical path length changing member 41 and the optical path length changing member 42 can be made relatively small, and the imaging unit 30 can be downsized.

  In addition, the image forming apparatus 1 according to the present exemplary embodiment is based on the subject imaged by the imaging unit 30 that simultaneously images a plurality of colors of the reference chart KC and an arbitrary subject and the imaging data of the reference chart KC. A colorimetric device for calculating the colorimetric value of the colorimetric value by the colorimetric control unit 106 is installed.

  Therefore, even if the RGB values for colorimetry when the colorimetric adjustment patch CP is imaged due to a change with time of the imaging unit 30 or the like, the change can be corrected, and the linearity of the colorimetric adjustment patch CP can be corrected. A colorimetric value can be obtained by taking out a portion having a color and linearly converting it, and color reproduction with suppressed distortion can be realized at low cost and more stably.

  Furthermore, in the above description, the color measurement process is performed by the color measurement control unit 106 of the image forming apparatus 1, but the color measurement process does not need to be executed inside the image forming apparatus 1. For example, FIG. As shown, an image forming apparatus 210 is connected to an external apparatus 220 as an image forming system (colorimetry system) 200, and image data captured by the image forming apparatus 210 is output to the external apparatus 220. The external device 220 performs color adjustment processing that includes colorimetric processing, and outputs the color-adjusted image data to the image forming device 210. The image forming device 210 forms an image based on the image data from the external device 220. May be.

  That is, the image forming apparatus 210 includes an engine 211, an operation display unit 212, an I / F unit 213, other I / F units 214, and the like, and each unit is connected by a bus 215. In addition, the external device 220 can use, for example, a computer having a normal hardware configuration and software configuration, and includes a color adjustment program including a color measurement program that executes a color adjustment process accompanying the color measurement process of the present invention as software. The color adjustment process accompanied by the colorimetric process is executed by introducing. The external device 220 includes a CPU 221, a memory unit 222, an image processing unit 223, a communication I / F unit 224, an I / F unit 225, and the like, and each unit is connected by a bus 226. The memory unit 222 includes a ROM 227, a RAM 228, a hard disk (HDD) 229, and the like.

  The image forming apparatus 210 is connected to the external apparatus 220 via a line 230 by an I / F unit 213. The line 230 is a dedicated line, a network such as a LAN (Local Area Network), the Internet, and the like, and is wired. Or wireless.

  The image forming apparatus 210 forms and outputs an image on a recording medium with the engine 211 based on the image data sent from the external apparatus 220 under the control of the external apparatus 220. The engine 211 forms an image on a recording medium by an ink ejection method or the like, and the operation display unit 212 includes various operation keys and a display such as an LCD (Liquid Crystal Display), which are necessary for the operation of the image forming apparatus 210. Various operations are performed by the operation keys, and various information notified from the image forming apparatus 210 to the user is displayed on the display. The other I / F unit 214 is used for connecting an expansion unit.

  The engine 211 includes a carriage that moves in the main scanning direction similar to that described in the above-described embodiment, and the imaging unit 30 is attached to the carriage. The image forming apparatus 210 forms the color measurement adjustment patch CP on the recording medium based on the color patch data of the color measurement adjustment color patch CP sent from the external apparatus 220 under the control of the CPU 221 of the external apparatus 220. The color measurement adjustment sheet CS is generated, the color measurement adjustment patch CP of the generated color measurement adjustment sheet CS is read by the imaging unit (imaging unit), and transmitted to the external device 220 via the I / F unit 213.

  The external device (calculation means) 220 stores in the hard disk 229 or the ROM 227 an image formation control program for controlling the operation of the image forming apparatus 210, a color adjustment program for performing color adjustment processing involving colorimetric processing of the present invention, and necessary data. The CPU 221 controls the image forming apparatus 210 based on a program in the ROM 227 or the hard disk 229, thereby causing the basic processing as the image forming apparatus 210 to be executed, and color adjustment processing with colorimetric processing according to the present invention. Execute.

  The hard disk 229 stores the above program and various data necessary for executing the color adjustment processing, in particular, the colorimetry of the plurality of reference color patches KP arranged on the reference sheet KS described in the above embodiment. At least one of the resulting Lab value and XYZ value, imaging reference RGB value, reference value linear transformation matrix, and neighborhood point table when the reference patch KP of the reference sheet KS is read by the imaging unit of the image forming apparatus 210 And the selected RGB value linear conversion matrix, the initial reference RGB value RdGdBd of each color patch of the reference chart KC read simultaneously with the reference sheet KS, and the reference chart read simultaneously when the colorimetric adjustment color patch CP of the colorimetry adjustment sheet CS is read KC reference patch color measurement reference RGB value RdsGdsBds and color measurement reference RG Reference RGB between linear transformation matrix to convert the value RdsGdsBds the initial reference RGB value RdGdBd is stored.

  The communication I / F unit 224 is connected to an image processing apparatus such as a scanner apparatus, a composite apparatus, or another external apparatus via a line such as a network, and receives image data that causes the image forming apparatus 210 to output an image. The I / F unit 213, the I / F unit 224, and the line 230 function as a communication unit as a whole.

  The image processing unit 223 performs various image processes necessary for forming and outputting the image data with the engine 211 of the image forming apparatus 210.

  As described above, the CPU 221 controls the operation of the image forming apparatus 210 and also executes a colorimetric process executed by the calculation unit 124 of the colorimetry control unit 106, in particular, the colorimetric value calculation unit 126. , Color adjustment is performed on the image data based on the colorimetric value, and the image data is output to the image forming apparatus 210.

  In the image forming system 200 of FIG. 23, the operation of the image forming apparatus 210 is controlled by the external device 220. However, the image forming apparatus 210 itself includes a controller such as a CPU. The external device 220 may execute only the color measurement process for which the controller controls and obtains the color measurement value, or only the color adjustment process including the color measurement process.

  As described above, when color adjustment processing including color measurement processing or color measurement processing is executed at least by an external device of the image forming apparatus 210, the color reproducibility can be appropriately improved at low cost even in the inexpensive image forming apparatus 210. it can.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Main body case 3 Main body frame 4 Main guide rod 5 Sub guide rod 6 Carriage 6a Connection piece 7 Timing belt 8 Drive pulley 9 Driven pulley 10 Main scanning motor 11 Cartridge part 12 Maintenance mechanism part 13 Cover 14 Platen 20, 20y, 20m, 20c, 20k Recording head 21 Encoder sensor 30 Imaging unit 31 Substrate 32 Frame body 32a Bottom surface portion 32b Opening portion 32c Opening portion 32d Recessed portion 32e Holding plate 33 Fastening member 34 Image sensor portion 35 Two-dimensional image sensor 36 Lens 37 Illumination Light source 38 Light source support member 41, 42 Optical path length changing member 43, 44 Holding member 50 Imaging unit 51, 52 Holding member 60 Imaging unit 61, 62 Optical path length changing member 101 CPU
102 ROM
103 RAM
104 Main Scan Driver 105 Recording Head Driver 106 Colorimetry Control Unit 107 Paper Transport Unit 108 Sub Scan Driver 110 Image Processing Unit 111 Interface Unit 112 A / D Conversion Unit 113 Shading Correction Unit 114 White Balance Correction Unit 115 γ Correction Unit 116 Image Format Conversion unit 121 Frame memory 122 Timing signal generation unit 123 Light source drive control unit 124 Calculation unit 125 Non-volatile memory 126 Colorimetric value calculation unit 200 Image forming system 210 Image forming apparatus 211 Engine 212 Operation display unit 213 I / F unit 214 Others I / F unit 215 Bus 220 External device 221 CPU
222 Memory unit 223 Image processing unit 224 Communication I / F unit 225 I / F unit 226 Bus 227 ROM
228 RAM
229 Hard disk 230 line KS reference sheet KP reference color patch CS colorimetry adjustment sheet CP colorimetry adjustment patch KC reference chart Pa to Pd reference color patch row Pe dot diameter measurement pattern row lk distance measurement line mk chart position specifying marker

JP-A-5-223642

Claims (1)

A sensor unit for imaging a subject through an opening;
A lens provided in the sensor unit;
A reference chart that is disposed on a side different from the opening with respect to the center of the sensor unit when viewed in the optical axis direction of the lens, and is imaged by the sensor unit together with the subject;
A first light transmitting member disposed in an optical path connecting at least the sensor unit and the reference chart;
An imaging unit comprising: