JPH0290783A - Image reader - Google Patents

Abstract

PURPOSE:To reproduce an image with high accuracy by illuminating a transmission type original in a direction inclined with a prescribed angle against the normal of the original, and providing a light shielding means for flare light at a prescribed part between the original and a light source. CONSTITUTION:A light shielding mask 87 is arranged at the part which shields the flare light F of an aperture part 86 along the main scan direction of the transmission type original S. In such a case, the flare light F1 reflected on a hair-line mirror 96 is shielded satisfactorily by the light shielding mask 87, therefore, it does not arrive at the transmission type original S. Also, since illumination light L is made incident in a state where it is inclined against the transmission type original S, the flare light F1 is completely separated, thereby, the flare light F1 is shielded perfectly by the light shielding mask 87. In such a manner, no flare light F1 arrives at a CCD camera, thereby, it is possible to perform the reproduction of the image with extreme high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device;
In the case of reading image information from a transmissive original whose both sides are held by a transparent press, a light shielding means is provided at a predetermined portion between the illumination means for illuminating the transmissive original from a direction inclined at a predetermined angle and the transmissive original. and illuminating by blocking flare light among the light output from the illumination means with a light blocking means,
The present invention relates to an image reading device configured to irradiate only bright light onto a transmissive original, thereby making it possible to obtain image information with uniform reading density.

[Background of the Invention] For example, in the fields of printing and plate making, image scanning reading records are used to electrically process image information carried on a manuscript to create a film master plate for the purpose of streamlining work processes, improving image quality, etc. The system is widely used.

This image scanning reading/recording system basically consists of an image reading device and an image recording device. That is, in the image reading device, image information of a document that is conveyed in a sub-scan direction in an image reading section is main-scanned by a photoelectric conversion element and converted into an electrical signal. Next, the image information photoelectrically converted by the image reading device is subjected to arithmetic processing such as gradation correction and edge enhancement according to the plate-making conditions by the image recording device, and then converted to an optical signal. are recorded and reproduced on a record carrier consisting of. Note that this recording carrier is developed by a predetermined developing device and used as a film original for printing or the like.

By the way, in an image reading device that reads image information of a transmissive original, a light source is placed below the transmissive original, and illumination light is output vertically upward and guided to a camera, which is an image reading means, to read the original. There is a vertical reading method for reading image information.

However, it has been pointed out that in this vertical reading method, the camera is placed in a vertically upward position symmetrical to the light source, resulting in an increase in the size of the device, especially in the height direction. .

On the other hand, an oblique reading method has been proposed in which a transmission type original is read from an oblique direction as a method that can overcome these drawbacks. In other words, in an image reading device that employs this tilted reading method, a light source is disposed diagonally below the transmission type original sandwiched between two transparent pressure plates, and the illumination output from the light source diagonally upward. Image information is read by illuminating a transmissive original in the main scanning direction and guiding the transmitted light to a camera.

In this case, the edge part of the image information carried on the transmissive original, that is, the edge of the high-density part (part with a high degree of blackening) adjacent to the low-density part (part with a low degree of darkening) is reproduced. The problem arises that the image becomes unclear at times. The cause of this will be explained based on FIG. 1.

In FIG. 1a, an image reading device 2 that reads image information carried on a transmissive original S has a light source ( Line-shaped illumination light is emitted obliquely upward along the main scanning direction from a camera (not shown), and the transmitted light is made to enter the camera 8. Inside the camera 8 is a condensing lens 10
is provided, thereby condensing the illumination light that has passed through the transmissive original S, guiding it to the light receiving element 12 in which photoelectric conversion sections are arranged in the main scanning direction, and reading image information.

In this case, at the edge portion (edge portion S) of the high-density portion S1 in the sub-scanning direction (arrow direction) of the transmissive document S and adjacent to the low-density portion S2, the edge portion S. The illumination light passes through the low-density portion S2, is reflected at point A on the inner surface of the presser glass 4, and enters the camera 8 through a force interaction with the flare light F that enters the reading point 0 of the edge portion S0. (See Figure a).

Therefore, when the optical signals from the illumination light and flare light F guided to the light-receiving element 12 in this manner are subjected to predetermined processing and reproduced on a film or the like, the image 11 shown in FIG. 1 will be obtained. become. Here, the double diagonal line part 13 of the image 11 is a part that is not affected by the flare light F, and the single diagonal line part 18 in the sub-scanning direction (direction of the arrow) is a part that is not affected by the flare light F. This is the part where the concentration of No. 11 has decreased. This single diagonal line portion 18 becomes more noticeable as the density of the image 11 becomes higher. As a result, the outline of image 11 becomes unclear,
A problem arises in that highly accurate image reproduction cannot be expected.

[Object of the Invention] The present invention has been made in order to overcome the above-mentioned disadvantages. It is an object of the present invention to provide an image reading device that illuminates a document with illumination light that is not affected by the flare light by providing a light shielding means for flare light at a predetermined portion of the image reading device, thereby making it possible to reproduce an image with high precision.

[Means for Achieving the Object] In order to achieve the above-mentioned object, the present invention employs the method of irradiating illumination light from an oblique direction onto a light-transmissive document carrying image information, which is sandwiched on both sides by transparent pressure plates. An image reading device that reads image information, the illumination device illuminating the light-transmissive original from a direction inclined at a predetermined angle with respect to the normal to the original surface; an image reading means disposed in a direction in which the illumination light that has passed through the light transmission type original is incident; and a light shielding means disposed close to the optical path of the flare light for blocking flare light.

Further, the present invention is characterized in that the light shielding means is disposed in the optical path of the flare light that enters the reading point at an incident angle substantially equal to the exit angle of the illumination light that passes through the reading point of the light-transmissive original. do.

[Embodiments] Next, preferred embodiments of the image reading apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

2 and 3, reference numeral 20 indicates an image reading device according to this embodiment, and this image reading device 20 includes a document input section 22, an image reading section 24, and a document illumination section 26.
It basically consists of.

In this case, the manuscript manual section 22 and the image reading section 24
Further, the document illumination section 26 is arranged between the document manual section 22 and the image reading section 24 . Note that the document input section 22 and the image reading section 24 are communicated through a passage 32 defined in the second housing 30. Horizontal and mutually parallel guide bars 34a and 34b are arranged between the document manual section 22 and the image reading section 24, and both ends of these guide bars 34a and 34b are supported on the first housing 28. It is supported by pedestals 36 and 38. Further, ball screws 40 are disposed on the supports 36 and 38 in parallel with the guide bars 34a and 34b. In this case, the ball screw 40 is driven by a drive motor 42 provided inside the first housing 28.
Rotationally driven by.

A document table 52 holding a transmissive document S carrying image information is movably supported by the guide bars 34a and 34b. That is, as shown in FIG. 4, the document table 52 includes a base 54, a table glass 56 on which the transmission type document S is placed, and a presser lid 58. The base 54 defines a hollow portion 60 through which the original illumination unit 26 is inserted, and an opening 6 for guiding illumination light to the transmission type original S through the base glass 56.
1 is defined. Further, hinge members 66a and 66b are attached to the sides of the base 54 to support the presser lid 58 so as to be openable and closable in the directions of arrows E, , and E, and on the opposite side, the presser lid 58 and the base are attached. A locking member 68 is attached having a lever 76 that engages 54. On the other hand, the presser lid 58 has a frame 77 having a substantially U-shaped cross section and a presser glass 78 surrounded by the frame 77, and the lever 76 of the locking member 68 on the base 54 side is attached to the frame 77. A handle portion 82 having an engaging lock hole 80 is attached.

The document illumination section 26 is surrounded by a hollow prismatic body 85 whose both ends are supported on the first housing 28 by the support stands 34a and 84b. An opening 86 for guiding illumination light in the image reading unit 24 is defined in the prismatic body 85,
A light-shielding mask 87 made of an aluminum plate or the like is placed in this opening 86 in close proximity to the illumination light in the main scanning direction (
It is attached along the direction of arrow C). Inside the prismatic body 85 is a light source 88 consisting of a halogen lamp, a xenon lamp, etc.
An optical fiber bundle 92 that is configured by bundling a large number of optical fibers 90 whose ends are held by light-guiding holding members 39a and 89b and guides the illumination light output from the light source 88; A cylindrical rod lens 94 is arranged to condense the guided illumination light into a line. The rod lens 94
The illumination light focused by is guided to the transmission type original S via the hairline mirror 96. In this case, the hairline mirror 96 is set so that the illumination light is obliquely incident on the document surface of the transmission type document S at a predetermined angle. Note that the hairline mirror 96 has an illumination light and a base glass 56.
It is preferable that the angle θ with respect to the normal line is approximately 30° (see FIG. 5). On the other hand, the second housing 3
A CCD camera 104 as an image reading means is provided inside the image reading unit 24 for receiving illumination light that has passed through the image reading unit 24 in an oblique direction via a mirror 102 and converting it into an electrical signal.

The image reading device according to this embodiment is basically configured as described above, and its operation and effects will be explained next.

First, with the document table 52 positioned in the document input section 22, the lever 76 constituting the locking member 68 is pressed with a finger or the like to release the lock, and the presser cover 58 is moved in the direction of the arrow E1 via the handle portion 82. (See Figure 4). Next, in this state, the transmission original S is placed on the base glass 56, and then the presser lid 58 is pressed against the transmission original S. That is, by displacing the presser lid 58 in the direction of arrow E2 and engaging the tip of the lever 76 with the lock hole 80 of the handle portion 820, the transmission original S is moved between the base glass 56 and the presser glass 7.
8. Next, the document table 52 is conveyed in the direction of the arrow under the action of the drive motor 42, and the image reading unit 24
to the specified location.

When the original platen 52 holding the transparent original S reaches a predetermined portion of the image reading section 24, the reading operation of the image information carried by the transparent original S is started. That is, the light source 88
After passing through an optical fiber bundle 92 made up of a large number of optical fibers 90, the illumination light outputted from the optical fiber bundle 92 is condensed by a rod lens 94, and guided to the document table 52 through an opening 86 via a hairline mirror 96. Then, the illumination light passes through the base glass 56 and illuminates the transmissive original S in the main scanning direction (
irradiate in the direction of arrow C). In this case, the illumination light passes through the transmissive original S to extract image information as an optical signal. The image information in the form of an optical signal passes obliquely through the presser glass 78, is guided to the CCD camera 104 via the mirror 102, and is converted into an electrical signal. During this time, the document table 52 is being transported in the sub-scanning direction (direction D) under the action of the drive motor 42. Therefore, the transmission type original S is two-dimensionally scanned by the illumination light, and its image information is extracted.

Here, the light emitted from the end of the optical fiber bundle 92 reaches the rod lens 94 as diverging light. In this case, the light emitted close to the optical axis of the rod lens 94 is guided to the document table 52 as regular illumination light, but the light emitted apart from the optical axis of the rod lens 94 is flare light. This results in F1 and F2 (see Figure 5). Among these flare lights Fl and F2, the flare light F2 reflected by the bare line mirror 96 and emitted in the direction of the arrow than the illumination light enters the base glass 56 through the opening 86, and then
The light passes through the transmission type document S, undergoes internal reflection repeatedly on the presser glass 78, and is emitted toward the CCD camera 104. However, since this flare light F2 is separated from the illumination light emitted from the holding glass 78, it does not enter the CCD camera 104, and therefore there is no risk of deteriorating the image.

On the other hand, the flare light F emitted in the direction opposite to the direction of the arrow from the illumination light deteriorates the image when the light shielding mask 87 is not provided. That is, the flare light F1, which is incident on the base glass 56, passes through the transmissive original S, and is reflected by the inner surface A of the presser glass 78, has an exit angle of illumination light at which the flare light F1 passes through the transmissive original S with respect to the reading point 0. When the incident angle φ is equal to θ, flare light F1 is added to the illumination light.
will be incident on the CCD camera 104 in an overlapping state (see FIG. 6C).

In this case, when an image is rendered on a film or the like by subjecting the optical signal composed of the illumination light and flare light F1 to a predetermined process, a decrease in density occurs in the portion where the illumination light and flare light F1 overlap.

That is, if the high-density area Sl of the transmission original S is located in the direction opposite to the direction of the arrow from the reading point 0, and the low-density part S2 is located in the direction of the arrow from the reading point 0, the high-density part Sl
Because the flare light F1 is blocked by (Fig. 6 a, b)
(Reference) Image quality will not be degraded. Of course,
If the high-density area S1 of the transmissive original S is located in the direction of the arrow from the reading point O, and the low-density part S2 is in the opposite direction of the reading point O (see Figure 6C), flare occurs. light F,
passes through the low-density portion S2 and enters the reading point 0, so the quality of the image deteriorates, especially at the edge nSo.

In contrast, in this embodiment, as shown in FIG.
A light-shielding mask 87 is disposed along the main scanning direction of the transmissive original S at a portion of the opening 86 that shields the flare light F1. In this case, the flare light F1 reflected by the hairline mirror 96 is suitably blocked by the light blocking mask 87 and does not reach the transmission type original S. Note that since the illumination light is incident on the transmission type original S in an inclined state, the flare light F1 is completely separated, and therefore,
The flare light F1 is completely blocked by the light shielding mask 87. As a result, the flare light F does not reach the CCD camera 104, making it possible to reproduce images with extremely high precision.

Note that the light shielding mask 87 prevents other flare light F caused by diffused reflection and stray light F reflected on the surface of the rod lens 94.
4 can also be shielded from light, making it possible to reproduce high-quality images.

[Effects of the Invention] As described above, according to the present invention, the light output from the illumination means can be illuminated by irradiating illumination light from a direction inclined at a predetermined angle with respect to the normal to the document surface of a transmissive type document. While separating the light and flare light, a light shielding means is disposed between the transmission type document and the illumination means and close to the optical path of the illumination light to block the flare light and image reading means such as a CCD camera, etc. It is configured so that it will not be incident on the

Therefore, since the flare light is easily and reliably blocked by the light blocking means, a high quality image with particularly clear outlines can be obtained from the optical signal obtained by the illumination light.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
For example, it is possible to make various improvements and changes in the design without departing from the spirit of the present invention, such as by making the light blocking means movable back and forth so that its position can be adjusted.

[Brief explanation of the drawing]

FIG. 1a is an explanatory diagram of an image reading device using an inclined reading method;
FIG. 1 is an explanatory diagram of an image drawn based on the optical signal read by the image reading device shown in FIG. is a schematic perspective explanatory diagram of an image reading device according to the present invention, FIG. 4 is a perspective explanatory diagram of a document table in the image reading device according to the present invention, and FIG. 5 is an enlarged cross-sectional explanation of main parts of the image reading device according to the present invention FIGS. 6A to 6C are explanatory diagrams of main parts of an image reading device according to the present invention. 2.20... Image reading device 52... Original table 87
... Light-shielding mask 88 ... Light source 94 ...
Rod lens 96...Hairline mirror L...Illumination light Fl-
F3...Flare light S...Transmissive original L O□ ]6

Claims (2)

[Claims] (1) An image reading device that reads image information by irradiating illumination light from an oblique direction onto a light-transmissive original holding image information held on both sides by transparent pressure plates, an illumination means for illuminating from a direction inclined at a predetermined angle with respect to the normal line of the document surface; and illumination light that is arranged in a direction inclined at a predetermined angle with respect to the normal line of the document surface and passes through the light transmission type document is incident. a light shielding means disposed between the illumination means and the light-transmissive original at a position on the inclined side of the illumination light and close to the optical path of the illumination light and blocking flare light; An image reading device comprising: (2) In the apparatus according to claim 1, the light shielding means is disposed in the optical path of the flare light that enters the reading point at an incident angle substantially equal to the exit angle of the illumination light that passes through the reading point of the light-transmissive original. An image reading device comprising: