JPH04306055A - Picture reader - Google Patents

Abstract

PURPOSE:To prevent a black stripe caused by a flaw 20 of an original 4 in the picture reader. CONSTITUTION:A flaw erase light 25 radiates to an original 4 obliquely upward. The flaw erase light 25 striking on a part without a flaw 20 is reflected obliquely onto an original 4 and is not in radiation to the optical system 14. Thus, the light quantity of the part reduced by the flaw 20 is compensated by the flaw erase light 25 and a black stripe caused by a read picture is eliminated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to a technique for preventing deterioration in the quality of read images due to scratches on a document.

0002

2. Description of the Related Art FIG. 6 shows a schematic configuration diagram of a general image reading device. A document 4 is placed on a document table 2, and a document holder 6 is further placed on top of the document 4. The document table 2 and the document holder 6 are transparent. A linear light source 26 irradiates reading light from above the document 4 . The reading light transmitted through the original 4 is reflected by the reflecting mirrors 8, 10, 12.
and CCDs 1 arranged in a row through a lens 14.
given to 6. CCD 16 converts this light into an electrical signal. As a result, an electrical signal corresponding to one scanning line of the original 4 is obtained.

When one scanning line has been read, the motor 18 moves the document table 2 in the direction of arrow A, and the next scanning line is read in the same manner. This is repeated to read the entire document 4.

0004

However, in the conventional image reading device as described above, there is a problem in that when there is a scratch on the document 4, the read image becomes black at the scratched part. Ta. The reason for this is thought to be as follows.

FIG. 7 shows a case where there is a scratch 20 on the original 4.
The reading state is schematically shown. Reading light 22a, 22
b, 22c, 22d, and 22e are assumed to be incident perpendicularly to the original 4. The reading light that has passed through the original 4 enters the lens 14,
An image is formed on the light receiving surface 24 of the CCD 16. It is assumed that the lens 14 is focused on the lower surface 4a of the original 4. Therefore, the lower surface 4a of the original 4 is imaged on the light receiving surface 24 of the CCD 16. Further, in this figure, it is assumed that the CCDs 16 are arranged in a row perpendicular to the plane of the paper, and the linear light sources 26 are arranged in a direction perpendicular to the plane of the paper. Furthermore, in reality, the linear light source 26 and the CCD 16 are stopped and the document 4 moves, but for convenience of explanation, the relative positions of the linear light source 26 and the CCD 16 are shown with respect to the document 4. Indicated.

As is clear from the figure, the reading light is refracted by the scratch 20, and the scanning light is refracted by the scratch 20, and the scanning light is
On the light receiving surface 24) of D16, regions 30b to 30c and 30d to 30e are formed which are brighter than the original brightness of the document. Further, regions 30c to 30d that are darker than originally are also formed. Therefore, this document 4 can be read on the CCD 16.
If the image is read by , unnecessary shading will occur. That is, as shown in the figure, 16b to 16c and 16d
When the position is from 16e to 16e, an image that is brighter than the original is output, and when it is from 16c to 16d, an image that is darker than the original is output. For this reason, black streaks that do not exist in the original 4 appear in the read image, degrading the image quality. Particularly in the highlighted portion of the document 4, the black streaks were noticeable and significantly degraded the image quality.

Furthermore, if a telecentric optical system such as the lens 14 is used, an image that is darker than the original image will be output over the range 16b to 16e. This means that when a telecentric optical system is used, only the perpendicularly incident reading light is transmitted to the CCD 16.
This is because it is given to Therefore, similar black streaks occur even when a telecentric optical system is used.

[0008] It is an object of the present invention to solve the above-mentioned problems and provide an image reading device that prevents black streaks caused by scratches or the like on the document 4 and provides high quality read images. .

[0009]

[Means for Solving the Problems] The present invention provides a transparent document table on which a document is placed;
In an image reading device that is equipped with a light source that emits reading light that is almost perpendicular to the original, and a photoelectric conversion element that receives the reading light that has passed through the original and converts it into an electrical signal, the image reading device is configured such that the image reading device is It is characterized by emitting scratch-erasing light in the direction.

0010

[Operation] The scratch erasing light that is obliquely irradiated onto the original is refracted at the scratched part of the original, and is directed toward a partially dark area (see sections 30c to 30d in FIG. 7). As a result, the amount of received light in the dark area is corrected to increase.

On the other hand, in areas where there are no scratches, the scratch erasing light passes obliquely through the document and does not enter the optical system. Therefore, in areas where there are no scratches, the scratch erasing light does not enter the photoelectric conversion element and does not affect the read image.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the effect of the scratch erasing light in the image reading apparatus of the present invention. Reading light 22b, 22c, 22
d is refracted by the scratch 20 on the document 4, forming dark areas 30c to 30d as described above. At this time, the original 4 is irradiated with the scratch erasing light 25a that is incident obliquely. The scratch erasing light 25a is refracted at the scratch 20 and darkens the area 30.
c to 30d. As a result, the areas 30c to 30
The amount of light at d is corrected in the direction of increasing. here,
Regarding the optical system 14, the lower surface 4a of the original 4 is in a conjugate relationship with the light receiving surface 24 of the CCD 16, that is, the lower surface 4a is imaged on the light receiving surface 24. Therefore, when the CCD 16, which is a photoelectric conversion element, is between 16c and 16d (corresponding to 30c to 30d of the focus plane 4a), the amount of light received is corrected, and the black streaks in the read image are corrected.

Note that the scratch erasing light 25c that has passed through the part without scratches 20 does not enter the optical system 14, so it does not affect the read image of the normal part (portion without scratches).

By the way, the telecentric optical system transmits only the light incident perpendicularly to the system and supplies it to the CCD 16. Therefore, if a telecentric optical system is used, there is no possibility that the scratch erasing light 25c will affect normal parts.

An embodiment for obtaining scratch-eliminating light is shown in FIG. The linear light source 26 includes a white light source 26a, and a cover 26b is provided around the outer periphery of the white light source 26a. cover 2
An opening 26c is provided at the bottom of 6b. Further, a rod-shaped lens 40 is provided between the linear light source 26 and the original 4. As shown in the figure, this rod-shaped lens 40 has a semicylindrical cross section.

The light from the white light source 26a is transmitted through the opening 26c.
The light is radiated downward from the Of the light emitted in this manner, the light directed directly below travels straight through the rod-shaped lens 40 and reaches the document 4 as the reading light 22. On the other hand, the light 25 irradiated obliquely from the linear light source 26 is transmitted to the rod-shaped lens 4.
0 and is obliquely irradiated onto the original 4 as scratch erasing light 25. In this way, the scratch erasing light 25 is obtained.

[0017] In order to change the irradiation angle θ of the scratch erasing light 25 with respect to the original 4, the rod-shaped lens 40 may be moved up and down (in the direction of arrow A). By changing the irradiation angle θ, an effective scratch erasing effect corresponding to various scratches on the document 4 can be obtained.

Another embodiment for obtaining scratch-eliminating light is shown in FIG. In this embodiment, the scratch erasing light 25 is obtained by bringing the linear light source 26 close to the original 4.

Still other embodiments are shown in FIGS. 4 and 5. In the embodiment of FIG. 4, light from linear light source 26 is focused at end 42 of the fiber array. The focused light is transmitted through three fibers 44a, 44 in each row.
b, 44c. The light passing through the fiber 44b is irradiated perpendicularly to the original 4 and becomes the reading light 22.
becomes. On the other hand, the light that has passed through the fibers 44a and 44c is obliquely irradiated onto the original 4 and becomes scratch erasing light 25.

In the embodiment shown in FIG. 5, a reflective mirror is used to obtain the scratch erasing light 25. Light directed directly downward from the linear light source 26 reaches the document 4 as reading light 22. On the other hand, the light emitted obliquely from the linear light source 26 is reflected by the reflecting mirror 50.
The light is reflected by the light and becomes a scratch erasing light 25 that irradiates the original 4 obliquely.

In each of the embodiments described above, the reading light 22 and the scratch erasing light 25 are obtained by one linear light source 26. However, a light source for the scratch erasing light 25 may be provided separately from the light source for the reading light 22.

[0022]

The image reading apparatus according to the present invention is characterized in that a scratch erasing light is irradiated obliquely onto a document from the light source side. As a result, the amount of light received in areas darkened by scratches on the document is corrected to increase.
Black streaks in read images can be eliminated.

In other words, it is possible to provide an image reading device that prevents black streaks caused by scratches or the like on a document and provides high quality read images.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the effect of scratch erasing light in an image reading device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a case where a rod-shaped lens is used as an example for obtaining scratch-eliminating light.

FIG. 3 is a diagram showing a case where a light source is brought close to a document as an example for obtaining scratch-eliminating light.

FIG. 4 is a diagram showing a case where a fiber array is used as an example for obtaining scratch-eliminating light.

FIG. 5 is a diagram showing a case where a reflecting mirror is used as an example for obtaining scratch-eliminating light.

FIG. 6 is a diagram for explaining the reading operation of the image reading device.

FIG. 7 is a diagram for explaining that black streaks occur in a read image due to scratches on a document in a conventional image reading device.

[Explanation of symbols]

4... Originals 22b, 22c, 22d... Reading lights 25a, 25
c... Scratch extinguisher 26... Linear light source 40... Rod-shaped lens 50... Reflector

Claims (1)

[Claims] Claim 1: A transparent document table on which a document is placed, a light source that emits reading light almost perpendicular to the document toward the document placed on the document table, and a light source that receives the reading light that has passed through the document. What is claimed is: 1. An image reading device comprising a photoelectric conversion element that converts into an electrical signal, the image reading device being characterized in that the document is irradiated with scratch erasing light in an oblique direction from the light source side.