JPH09200442A - Iamge reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image reader which prevents the unevenness of image data from generated owing to a filament unevenness. SOLUTION: A light quantity control plate 9 is provided on a partial reflecting surface 10 of a reflector 3 to form a nonreflection surface which does not reflect light. This light quantity control plate 9 limits reflection more from the center part to both the end parts in a horizontal scanning direction. The light quantity control plate 9 having the characteristics limits the irradiation of a document from the reflection surface 10 by the light source 5 to make an uneven ripple uniform. Consequently, the filament unevenness which is caused can be eliminated. The nonreflection surface 9 can be constituted by being coated with paint, scattered, or provided with nonreflection holes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device, and more particularly to an image reading device having a digital reading optical system and applied to a copying machine, an image scanner or the like.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus generally uses a rod-shaped halogen lamp as a light source of an optical system. This rod-shaped halogen lamp usually has 7 to 8 filaments,
It is arranged in a straight line with a certain space and is enclosed in a glass tube together with a halogen gas. Further, the surface of the glass tube is frosted in the form of frosted glass in order to irradiate uniform illumination light.

However, as a problem due to the use of the rod-shaped halogen lamp, there is light amount ripple due to the filament. The amount of light in the filament portion is higher than that in other portions, and the above frost processing cannot make the light source uniform and sufficiently eliminate the light amount ripple. Therefore, many illumination systems have so-called light amount ripples. In an analog copying machine, light amount ripples cause image unevenness, and some proposals have been made to prevent this.

Japanese Patent Laid-Open No. 3-31839 "Image reading device"
Argues that by arranging the diffusing member in the predetermined optical path so that it can be inserted and removed, the image information can be read with high accuracy regardless of the image information.

In Japanese Utility Model Laid-Open No. 4-135070, "image reading device", a plurality of filaments are arranged in a long tube at predetermined intervals so as to face each other between the filament positions of other halogen lamps. Is characterized by.

In a digital copying machine, a shading plate arranged in the main scanning direction is read by a CCD in advance and stored therein, and data obtained by reading an image is divided by this to correct a light amount ripple, so-called shading correction is performed. . For this reason, it is said that a digital copying machine is unlikely to be affected by light amount ripple due to a filament. In fact, when the document almost diffuses the irradiation light, the shading correction described above can correct the light amount ripple due to the filament.

[0007]

However, when a part of the original document is specularly reflected, the above shading correction may not be sufficient. Generally, when the original has a glossy surface parallel to the contact glass, the emitted light is totally reflected and the copied image becomes black. However, in the case of a glossy surface that is not parallel, it may be reflected and jump directly into the optical path. In this case, the amount of light in the portion where the filament exists is higher than that in the other portions, and the copy image becomes whitish only in the portion where the filament exists. This phenomenon is called filament unevenness. This phenomenon is data for the reference plate in which the correction data of the shading correction is diffused, and is caused by the different light amount distribution for the reflected light.

In recent years, the common use of units by a plurality of models has been promoted, and the cost and the development period have been shortened. Therefore, an efficient lighting system is designed for high-speed models that require a larger amount of light, and it is applied horizontally to low-speed models. In such a case, in order to realize an efficient illumination system, the light path reflected by the lamp light source and the reflector and reaching the document tends to be short,
Due to that reason, the unevenness due to the filament is further increased.

Further, the 7-point or 8-point filament of the rod-shaped halogen lamp does not have a uniform light quantity. Since a reduction type reading device such as a copying machine uses a lens, the amount of light at both end portions is lower than that at the central portion. This is called the cosine fourth law, and is a characteristic peculiar to a lens in which the amount of light decreases with the coefficient of the cosine fourth power according to the incident angle toward both ends. Weight is applied to the filament of the rod-shaped halogen lamp so as to reduce this and flatten the light intensity. That is, the light intensity distribution of the halogen lamp is higher toward the periphery than in the center. However, due to the above-mentioned cosine fourth law, it is flat when it reaches the CCD surface through the lens. Even in the case of diffused light, there is an influence of the filament, and the light amount distribution of the halogen lamp has ripples, but it is corrected by shading correction.

On the other hand, the light amount distribution for the reflected light is more affected by the filament than the light amount distribution for the diffused light.
This is because diffused light is formed by condensing the entire reflector, while reflected light is affected by light from a specific angle. That is, in the case of diffused light, the light from the adjacent filament also has an effect, but in the case of reflected light, the effect of the directly radiating filament is the strongest. In addition, since the peripheral filaments have a higher light intensity than the central filaments, the influence is large.

For the reasons described above, the filament unevenness in the glossy original or the like has a greater effect toward both ends as compared with the center of the main scanning. That is, the light amount distribution for the reflected light rises toward the surroundings, which is different from the light amount distribution for the diffused light. Therefore, it is difficult to perform shading correction.

As an original document which causes such a phenomenon, a product catalog using fine wrinkled paper, etc., which is particularly glossy and blackish, is easily affected. In addition, a pattern, such as a printed circuit board, having a raised pattern and having gloss due to resist processing, and having patterns running in parallel in a certain direction is also susceptible to the problem. Both are likely to be originals in color copiers.

The mechanism of occurrence of image data unevenness due to filament unevenness in the above conventional image reading apparatus will be considered in detail. FIG. 6 is a diagram showing a configuration of a conventional optical system. The above-mentioned filament unevenness becomes a problem in a product catalog or the like using paper with fine wrinkles, and is particularly noticeable in a glossy and blackish document. In FIG. 6, 2 is a contact glass on which the original 1 is placed, 5 is a light source in which a plurality of light emitting segments are arranged in a straight line at intervals, and 3 and 4 are reflectors that reflect the emitted light of the light source 5 and irradiate the original surface. , 6 are shield plates for avoiding direct light from the light source 5 to the document 1.

In the optical system shown in FIG. 6, two optical paths can be considered. One is radiated from the light source 5 and the reflector 3
Is an optical path for irradiating the original 1 by being reflected by a part of the reflecting surface 10, and the other is an optical path for irradiating the original 1 by being reflected once by the reflector 3 and then again by the reflector 4.
Comparing these, the first optical path has a shorter distance to reach the original 1 than the second optical path.

FIG. 7 shows an example of a light source in which a plurality of light emitting segments are arranged on a straight line at intervals. The light source 5 is composed of a plurality of filaments 11. Filament 11
As described above, in order to correct the cosine fourth law of the lens, the surrounding light amount is stronger than that in the center.

FIG. 8 shows the illuminance distribution in the main scanning direction of the original surface by the first optical path, and FIG. 9 shows the illuminance distribution in the main scanning direction of the original surface by the next optical path. As can be seen from FIGS. 8 and 9, the shorter the distance from the filament 11, the more susceptible it is to the filament.

FIG. 10 shows the light quantity distribution of the diffused light of the light source 5 of FIG. In the case of the example of FIG. 7, since there are eight filaments 11, the number of ripples is also eight.
Moreover, the size of the ripple is larger toward the periphery than in the center. This non-uniform distribution of ripples is an obstacle to ripple compensation.

It is an object of the present invention to provide an image reading apparatus which prevents the occurrence of image data unevenness due to filament unevenness.

[0019]

In order to achieve such an object, an image reading apparatus of the present invention comprises a light source in which a plurality of light emitting segments are linearly arranged at intervals, and a light emitted from the light source is reflected. It has an original illuminating device equipped with a reflector for illuminating the surface of the original, and an optical system for forming an image of the original on a CCD. The reflector limits the irradiation of the original from a specific portion, and this limitation is in the main scanning direction. It is characterized in that both ends are configured with a larger amount of restriction than the central part.

Further, it is preferable that the above-mentioned specific portion is a portion where the distance from the light emitting segment to the document is the shortest by being reflected by the reflector.

Further, as a limitation, a part of the reflecting surface of the reflector is formed as a non-reflecting surface, a diffusing surface, a hole or the like, and the area for forming these is larger at both end portions than in the central portion in the main scanning direction. Good to do.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an image reading apparatus according to the present invention; FIG.
5 to FIG. 5, there is shown one embodiment of the image reading apparatus of the present invention.

<Principle of Uniformizing Light Amount of Filament by Reflected Light> FIG. 1 is a diagram showing a configuration of a peripheral portion of a light source of an optical system of this embodiment. In other words, this is an embodiment for preventing the conventional filament unevenness shown in FIG. In FIG. 1, reference numeral 9 is a light amount control plate that does not reflect light, which is attached to a part of the reflecting surface 10 of the reflector 3. By limiting the irradiation of the document from the reflecting surface 10, the light flux having the light quantity distribution shown in FIG. 10 is cut, so that the filament unevenness caused by it can be prevented.

The light quantity control plate 9 shown in FIG. 1 is one example of the structure, and the same effect can be obtained by applying paint or removing the reflector itself in this portion. This configuration will be described in detail below.

The mechanism of occurrence of filament unevenness will be examined again below. A waveform C in FIG. 2 is a light amount distribution when the light amount distribution of the waveform A in FIG. 10 passes through the lens and is subjected to shading correction. The light amount distribution is flat due to the influence of the cosine fourth law and the shading correction. That is, the waveform A in FIG. 10, which is the light amount distribution due to the diffused light, is nothing but shading data when the shading reference plate is read. Since the data when reading the original is determined by this shading data, if the read data is due to diffused light, it will be completely corrected, and there will be no effect of rising surroundings or ripples and it will be flat. Become.

Waveform B in FIG. 10 shows the light quantity distribution of the reflected light from the light source 5 in FIG. In the case of the example of FIG. 7, since there are eight filaments 11, the number of ripples is also eight. However, the difference from the waveform A in FIG. 10 is that the amount of ripple is large. This is because, as described above, in the case of diffused light, the light from the adjacent filament also influences, but in the case of reflected light, the influence of the directly radiating filament is the strongest.

A waveform D in FIG. 2 is a light amount distribution when the light amount distribution of the waveform B in FIG. 10 passes through the lens and is subjected to shading correction. Due to the influence of the cosine fourth law and shading correction, the light amount distribution is somewhat flat, but ripples cannot be removed and remain. That is, even if the read data by the reflected light is divided by the shading data by the diffused light, the shape is not completely flat because the shape of the light quantity distribution is different. For product catalogs that use paper with such fine wrinkles, especially for glossy and blackish manuscripts,
Shading correction cannot be completed, and white streaky unevenness occurs at the filament position. Further, as described above, the white streak-like unevenness has a larger effect on both ends than on the center. Therefore, it becomes necessary to weaken the light amount of the filament due to the reflected light so as to be uniform.

<First Embodiment> FIG. 3 shows a first embodiment for equalizing the light amount of the filament due to the reflected light. In FIG. 3, 9 is the reflector 3 of the embodiment of FIG.
It is a specific example of the light amount control plate stuck to the 10 parts of. The light quantity control plate 9 is entirely made of a glossy surface, and only the shaded portion in FIG. 3 is painted black, for example, to form a non-reflective surface. The area of the non-reflective surface is proportional to the light amount of the filament 11 of the light source 5 in FIG. Since the amount of diffused light is determined by the entire reflector, the amount of diffused light is not much affected by the light amount control plate 9. Some effects are corrected by shading correction. On the other hand, the light quantity control plate 9 attached to the most affected area weakens the light quantity in proportion to the light quantity of the filament, and the reflected light becomes uniform. In this case, it is necessary to approximate the light amount distribution of diffused light. Of course, the light quantity control plate 9 need not be attached, and the reflector 3 may be directly painted black.

<Second Embodiment> FIG. 4 shows a second embodiment in which the light quantity of the filament due to the reflected light is made uniform. In FIG. 4, 12 is the reflector 3 of the embodiment of FIG.
It is a diffusion control plate attached to the reflective surface 10 of the. The diffusion control plate 12 is entirely made of a glossy surface, and only the vertical line portion in FIG. 4 is, for example, subjected to hairline processing to be a diffusion surface. The area of the diffusing surface is proportional to the light amount of the filament 11 of the light source 5 shown in FIG. The effect of the diffusion control plate 12 is almost the same as the effect of the light amount control plate 9 in FIG. However, in the light amount control plate 9 of FIG. 3, the shaded portion is formed as a non-reflective surface to reduce the total light amount, whereas the diffusion control plate 12 of FIG.
The vertical line portion is configured as a diffusing surface, and the decrease in light amount is small.

<Third Embodiment> FIG. 5 shows a third embodiment for equalizing the light amount of the filament due to the reflected light. In FIG. 5, 13 is the reflector 3 of the embodiment of FIG.
This is a light amount control hole provided in the portion of the reflection surface 10 of the above. The effect of the light quantity control hole 13 is almost the same as the effect of the light quantity control plate 9 of FIG.

In each of the above embodiments, the light quantity control plate 9 requires paint in the first embodiment of FIG.
In the second embodiment, the diffusion control plate 12 requires hairline treatment.

On the other hand, in the third embodiment shown in FIG. 5, since the light quantity control hole 13 can be processed by the same die as the reflector, there is an effect of cost reduction.

As described above, according to each of the above-described embodiments, it is possible to uniformly prevent filament unevenness of a document which is particularly glossy and dark in a product catalog using fine wrinkled paper.

[0034]

As is clear from the above description, in the image reading apparatus of the present invention, the irradiation of the document from the specific portion of the reflector is limited, and this limitation is that both end portions in the main scanning direction are compared with the central portion. A large amount is configured. Therefore, the filament unevenness is made uniform, and it is possible to prevent the occurrence of the unevenness due to the correction process.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a light source peripheral portion of an embodiment of an optical system of an image reading apparatus of the present invention.

FIG. 2 is a light amount distribution diagram of diffused light from a light source.

FIG. 3 is a diagram showing a first embodiment of “restriction”.

FIG. 4 is a diagram showing a second embodiment of “restriction”.

FIG. 5 is a diagram showing a third embodiment of “restriction”.

FIG. 6 is a diagram showing a configuration of a conventional optical system.

FIG. 7 is a diagram showing a configuration example of a conventional light source.

FIG. 8 is an illuminance distribution diagram in the main scanning direction on a document surface when the optical path length is short.

FIG. 9 is an illuminance distribution diagram in the main scanning direction on a document surface when the optical path length is long.

FIG. 10 is a light quantity distribution diagram of diffused light from the light source of FIG.

[Explanation of symbols]

 1 Original 2 Contact Glass 3, 4 Reflector 5 Light Source 9 Light Quantity Control Plate 10 Reflection Surface 11 Filament 12 Diffusion Control Plate 13 Light Quantity Control Hole

Claims (5)

[Claims] 1. A document illuminating device comprising a light source in which a plurality of light-emitting segments are linearly arranged at intervals, a reflector for reflecting the emitted light of the light source and illuminating the surface of the document, and a CCD for the document. The reflector limits the irradiation of the document from a specific portion, and the limitation is such that both end portions in the main scanning direction have a larger limiting amount than the central portion. An image reading device characterized by. 2. The image reading apparatus according to claim 1, wherein the specific portion is a portion that is reflected from the light emitting segment by the reflector and has a shortest distance to the document. 3. The limitation is that a part of the reflecting surface of the reflector is formed as a non-reflecting surface, and the area of the non-reflecting surface is configured such that both end portions are larger than the central portion in the main scanning direction. The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus. 4. The limitation is that a part of the reflecting surface of the reflector is formed as a diffusing surface, and the area of the diffusing surface is configured such that both end portions are larger than the central portion in the main scanning direction. The image reading apparatus according to claim 1 or 2. 5. The limitation is that a part of the reflecting surface of the reflector is formed as a hole, and the area of the hole is larger at both end portions than in the central portion in the main scanning direction. The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.