JPH09130542A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the image reader in which blooming and uneven filament are prevented. SOLUTION: The device is provided with an original lighting device 20 having reflectors 3, 4 reflecting an emitted light from a light source 5 (in which plural luminescent segments are arranged on a line at an interval) to emit the reflected light onto an original face and has an optical system to form an image on the original face to a CCD 8. In this case, the read device is provided with a means limiting a luminous quantity reaching the CCD face to prevent blooming and with a means limiting emission from a specific part 10 of the reflectors onto the original so as to prevent uneven filament. The means to limit the luminous multi-value processing reaching the CCD face may be a filter 6 to reduce the transmission luminous quantity, may be the reflectors 3, 4 whose reflectance on the reflecting faces is decreased, or may be the reflectors 3, 4 whose reflecting faces are approximated planes to decrease the light collection rate.

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, particularly a digital reading optical system, and is applicable to a copying machine, an image scanner and the like.

[0002]

2. Description of the Related Art In a digital reading device, a CCD (charge coupled device) is used as a photoelectric conversion element, but blooming is a phenomenon peculiar to CCD. Blooming is a phenomenon in which, when a light amount equal to or greater than the saturated light amount is incident on the CCD, not only the incident pixels are saturated, but also the adjacent pixels that are not incident are affected by the saturated light amount and are saturated. When blooming occurs in a copying machine, a metallic glossy portion appears as an abnormal image with a white tail in the main scanning direction when a decorative article or a watch having metallic glossy is copied. Black and white copiers are instructing users not to copy metallic glossy surfaces, but with the spread of color copiers in recent years, three-dimensional objects with metallic glossy surfaces become more likely to become documents, and blooming opportunities also increase. ing.

The output voltage of the CCD is proportional to the storage time, and when the same amount of light is incident on the CCD, the shorter the storage time is, that is, the faster the copying speed of the copying machine is, the lower the output voltage is. . Conversely, it can be said that blooming is more likely to occur in a copying machine with a slower copying speed. In order to prevent blooming in a copying machine with a slow copy speed, basically, the light amount should be reduced. The easiest way to reduce the light intensity is to reduce the lamp power. However, in a color copying machine, a halogen lamp is used in order to obtain good spectral characteristics, and the power of the lamp cannot be easily reduced. That is, when the power of the lamp is reduced, the filament becomes thin and the life of the lamp is shortened.

Further, in recent years, in the field of various devices including a copying machine, the common use of the unit has been promoted among a plurality of models, and the cost and the development period have been shortened.
In the field of copying machines and the like, an efficient illumination system is designed for high-speed models that require a larger amount of light, and it is applied to low-speed models as well. Therefore, in order to prevent blooming in a low-speed copying machine, it is necessary to use a method of reducing the light amount while sharing the illumination unit with that of a high-speed copying machine.

Next, as a problem due to the use of the rod-shaped halogen lamp, there is light amount ripple due to the filament. A rod-shaped halogen lamp is usually made by arranging 7 or 8 filaments on a straight line at a certain interval and enclosing them in a glass tube together with a halogen gas. The surface of the glass tube is frosted into a frosted glass to irradiate uniform illumination light. However, since this frosting process is not sufficient to obtain uniform illumination light, the light amount of the filament portion is higher than that of others, and many illumination systems have so-called light amount ripples. In an analog copying machine, the light amount ripple causes image unevenness, and several patents have been applied for a technique for preventing this. JP 5
JP-A-8-222663, JP-A-2-135607, JP-A-2-224458, and JP-A-2-285.
Examples are those described in JP-A No. 338, JP-A-2-287529, JP-A-3-28839, JP-A-5-14617, and the like.

On the other hand, in a digital copying machine, a shading plate arranged in the main scanning direction is read in advance by a CCD and stored, and the light amount ripple is corrected by dividing the read data of the image by so-called shading correction. It is carried out. Therefore, in the digital copying machine, the influence of the light amount ripple due to the plurality of filaments (light emitting segments) of the light source being arranged at regular intervals is less likely to occur.

When the original diffuses most of the illumination light, the shading correction can correct the light amount ripple due to the filament. However, when the original partially reflects specularly, the correction may not be successful. Generally, when the original is a glossy surface parallel to the contact glass, the emitted light is totally reflected by the original surface, and the copied image becomes black. However, if the original has a glossy surface that is not parallel, some of it may be reflected and jump directly into the optical path. In this case, the light amount of the portion where the filament is present is higher than that of other portions, and the copy image becomes whitish only in the portion where the filament is present. This is a phenomenon called filament unevenness. In other words, the correction data for shading correction is data for the diffused reference plate,
Since the light amount distribution is different for the reflected light, such filament unevenness occurs.

As an original document which causes such a phenomenon, there is a product catalog using a paper with fine wrinkles, and particularly a glossy and blackish one 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 the patterns running in parallel in a certain direction is also easily affected. Both of them are likely to be originals in a color copying machine, and there are many opportunities to cause filament unevenness.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and can prevent blooming phenomenon and filament unevenness.
An object is to provide an image reading device such as a copying machine.

[0010]

In order to achieve the above object, the invention according to claim 1 is a light source in which a plurality of light emitting segments are linearly arranged at intervals, and the emitted light of the light source is reflected. A document illuminating device having a reflector for illuminating the document surface, and a CCD as a photoelectric conversion element for an image on the document surface
An image reading apparatus having an optical system for forming an image on the image pickup device is provided with means for limiting the amount of light reaching the CCD surface and means for limiting the irradiation of the document from a specific portion of the reflector.

The means for limiting the amount of light reaching the CCD surface may be a filter arranged between the document surface and the CCD surface to reduce the amount of transmitted light, as in the second aspect of the invention. The reflection surface of the reflector for reflecting the radiated light of the light source and irradiating the original surface may be lowered as in the invention according to claim 3, and the reflection of the reflector according to the invention according to claim 4 may be adopted. The surface may be configured by plane approximation to reduce the light collection rate.

The specific portion of the reflector may be a portion where the distance of the illumination light from the light emitting segment through the reflector to the document is the shortest, as in the fifth aspect of the invention. Further, the means for limiting the irradiation of the document from the specific portion of the reflector may be formed by making a part of the reflector surface a non-reflecting surface as in the invention according to claim 6. As in the invention described in the seventh aspect, it may be formed by not arranging a reflector surface for illuminating the original surface on the specific portion.

[0013]

Various embodiments of an image reading apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of an image reading apparatus according to the present invention. In FIG. 1, reference numeral 2 indicates a contact glass.
A document is placed on the upper surface of the. Below the contact glass 2, a plurality of light emitting segments are arranged in a straight line at intervals, reflectors 3 and 4 for reflecting light emitted from the light source 5 and irradiating a document surface, and an image of the document are formed. A lens 7 for forming an image and a CCD 8 for reading an image are arranged. The light source 5 is a rod-shaped halogen lamp, for example, and a partially cylindrical reflector 3 is arranged so as to surround the light source 5 and with its opening directed obliquely upward. The reflector 3 irradiates the original on the contact glass 2 with the illumination light from the light source 5 for the specific portion 1
0 (the edge portion on the diagonally lower side in FIG. 1) and the illumination light from the light source 5 other than the specific portion 10 are reflected by the other reflector 4.
And a reflecting surface that reflects toward. The other reflector 4 is formed in a partially cylindrical shape having an opening angle smaller than that of the one reflector 3, and illuminates the original 1 with the illumination light reflected by the one reflector 3. ing. The light source 5 and the reflectors 3 and 4 form a document illumination device 20.

The lens 7 guides the reflected light from the original 1 illuminated through the contact glass 2 to the CCD 8 as a photoelectric conversion element, and forms an image of the surface of the original 1 in a line on the light receiving surface of the CCD 8. Constitutes the optical system of. The light source 5, the reflectors 3, 4, the lens 7, and the CCD 8 described above are integrally attached to one moving body,
The light source 5 moves in a direction orthogonal to the longitudinal direction. CCD8
Reads the image of the document 1 line by line at regular intervals and outputs a signal corresponding to the image. By inputting a signal from the CCD 8 to, for example, a semiconductor laser forming an optical scanning device, an image of the original 1 can be formed on a photosensitive drum or the like, and the image of the original 1 can be formed by executing a well-known electrophotographic process. It can be formed on transfer paper.

In the image reading apparatus, it is assumed that the original 1 such as a decorative article having a metallic luster is placed on the contact glass 2. The light emitted from the light source 5 is reflected by the reflector 3,
It is reflected by 4 and irradiated on the original on the contact glass 2, but the glossy surface of the original 1 is not parallel to the contact glass 2 and is the same as the angle formed by the optical axis of the lens 7 and the irradiation angle of the illumination light. If it is inclined only, the light reflected by the glossy surface of the original 1 jumps straight into the CCD 8 in the same direction as the optical axis, that is, through the optical path. Therefore, in the above-described conventional example, the CCD 8 is saturated because the light is too intense, and the adjacent pixels are also affected by the blooming phenomenon, resulting in an abnormal image with a white tail.

Therefore, in the embodiment shown in FIG. 1, the CCD 8 is provided between the contact glass 2 and the lens 7.
As a means for limiting the amount of light reaching the surface of, the filter 6 for reducing the amount of transmitted light is arranged. In order to prevent blooming, it is necessary to reduce the light intensity, and in color copiers, halogen lamps are used as the light source in order to obtain good spectral characteristics. It cannot be lowered. FIG.
If the filter 6 is placed in the optical path as a means for limiting the amount of light reaching the surface of the CCD 8 as in the embodiment shown in FIG. 1, the power of the halogen lamp as the light source is not lowered, and therefore good spectral characteristics are obtained. Blooming can be prevented while keeping the life of the light source long.

FIG. 2 shows a second embodiment for preventing blooming. In FIG. 2, reference numeral 2 is a contact glass on which an original is placed, and 5 is a plurality of light emitting segments arranged in a straight line at intervals. Reflected light sources 3, 4 reflect light emitted from the light sources and illuminate the surface of the original, 20
Indicates an original illuminating device including the light source 5 and the reflectors 3 and 4. In the second embodiment, as a means for limiting the amount of light reaching the surface of the CCD 8, the reflectance of the reflecting surfaces of the reflectors 3 and 4 that reflect the emitted light of the light source 5 and illuminate the document surface is lowered. There is. Therefore, also in this embodiment, blooming can be prevented without lowering the power of the halogen lamp as the light source.

FIG. 3 shows a third embodiment for preventing blooming. In FIG. 3, reference numeral 2 is a contact glass on which a document is placed, 5 is a light source in which a plurality of light emitting segments are arranged at intervals on a straight line, and 3 and 4 are reflectors that reflect the emitted light of the light source and illuminate the document surface. , 20 designates a document illuminating device including the light source 5 and the reflectors 3 and 4. In the third embodiment, the reflectors 3, 4 are provided as means for limiting the amount of light reaching the surface of the CCD 8.
The polygonal cross section is used to configure the reflecting surfaces of the reflectors 3 and 4 in a plane approximation to reduce the light collection rate. Therefore,
Also in this embodiment, blooming can be prevented without reducing the power of the halogen lamp as the light source.

Next, the filament unevenness which becomes a problem when a product catalog or the like using fine wrinkled paper is used as an original and its image is read will be described. The filament unevenness is remarkable especially in the case of a dark-colored original document. FIG. 4 shows an example in which the document 1 having fine wrinkles as described above is read by a conventional general optical system. In FIG. 4, reference numeral 2 is a contact glass on which a document 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 and illuminate the document surface. , 6 are means for avoiding direct light from the light source 5 to the document.

Consider two optical paths in FIG. One is an optical path that is emitted from the light source 5 and is reflected by the reflecting surface of the specific portion 10 of a part of the reflector 3 to illuminate the original 1.
That is, the light path from the light emitting segment of the light source 5 to the document 1 via the reflector 3 is the shortest distance (hereinafter, this light path is referred to as “first light path”), and the other is once reflected by the reflector 3. This is an optical path (hereinafter, this optical path is referred to as a “second optical path”) that is reflected by the rear reflector 4 again and illuminates the original 1. What can be seen by comparing these two optical paths is that the first optical path has a shorter distance to reach the original 1 than the second optical path. Therefore, let us compare the illuminance distributions in the main scanning direction on the document surface by these two optical paths. FIG. 5A shows an illuminance distribution in the main scanning direction on the original surface by the first optical path, and FIG. 5B shows an illuminance distribution in the main scanning direction on the original surface by the second optical path. As is clear from a comparison between (a) and (b) of FIG. 5, the illuminance distribution by the first optical path has a larger ripple due to the filament than the illuminance distribution by the second optical path. The reason is that the shorter the distance from the filament, the more susceptible it is to the filament.

In view of the above points, FIG. 6 shows an embodiment in which measures for preventing filament unevenness are taken. In FIG. 6, a light non-reflecting member 9 is attached to the reflecting surface of the specific portion 10 of the reflector 3. The non-reflective member 9 constitutes means for limiting the irradiation of the original 1 from the specific portion 10 of the reflector 3. According to the embodiment shown in FIG. 6, the illumination light reflected by the specific portion 10 of the reflector 3 and reaching the surface of the original 1 through the shortest distance is limited by the non-reflection member 9. Therefore, the light flux having a large ripple light amount distribution as shown in FIG. 5A is cut,
It is possible to prevent filament unevenness caused thereby.

Document 1 from specific portion 10 of reflector 3
The means for limiting the irradiation to the specific portion 10 is not limited to sticking the non-reflective member 9 on the specific portion 10, and other appropriate means, for example, applying paint or the reflector surface itself of the specific portion 10 may be used. The same effect can be obtained by eliminating it.

The blooming measures and filament unevenness prevention measures described above do not compete with each other and can be implemented simultaneously. The embodiment shown in FIGS. 1, 2 and 3 is an example in which both of them are implemented. That is, in FIG. 1, FIG. 2, and FIG. 3, reference numeral 9 indicates a non-reflection member similar to the non-reflection member 9 described in FIG.

[0025]

According to the first aspect of the invention, in an image reading apparatus having an original illuminating device and an optical system for forming an image of the original surface on a CCD, the amount of light reaching the CCD surface is adjusted. By providing the limiting means, it is possible to prevent the blooming phenomenon without lowering the power of the light source, and thus while maintaining good light source characteristics and long life of the light source, and to prevent the blooming phenomenon from a specific portion of the reflector. By providing a means to limit the irradiation of the original,
It is possible to prevent filament unevenness.

According to the invention of claim 2, the amount of light is limited by inserting a filter for reducing the amount of transmitted light in the optical path, and according to the invention of claim 3, the reflectance of the reflecting surface of the reflector is low. According to the invention as set forth in claim 4, since the reflecting surface of the reflector is configured in a plane approximation and the light collecting rate is reduced to limit the light amount, the power of the light source is not reduced. The blooming phenomenon can be prevented while obtaining good spectral characteristics and keeping the life of the light source long.

According to the fifth aspect of the invention, since the specific portion of the reflector that limits the irradiation of the original is the portion where the distance from the light emitting segment to the original is reflected by the reflector and reaches the original, the filament unevenness is the largest. Irradiation to the original is limited in the optical path that tends to occur, and filament unevenness can be effectively prevented.

According to the invention described in claim 6, as means for limiting the irradiation of the document from the specific portion of the reflector,
According to the invention of claim 7, the specific portion is a non-reflecting surface, and by not disposing a reflector surface for irradiating the reflecting surface in the specific portion, the specific portion is easily affected by filament unevenness. Since the irradiation of the original from the original is limited, filament unevenness can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of an image reading apparatus according to the present invention.

FIG. 2 is a perspective view showing another embodiment of the image reading apparatus according to the present invention.

FIG. 3 is a perspective view showing still another embodiment of the image reading apparatus according to the present invention.

FIG. 4 is a front view showing a general example of an image reading apparatus.

FIG. 5 shows an illuminance distribution in the main scanning direction on a document surface,
(A) is a characteristic diagram showing a case where the illumination light path is short, and (b) is a characteristic diagram showing a case where the illumination light path is long.

FIG. 6 is a perspective view showing still another embodiment of the image reading apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 3 Reflector 4 Reflector 5 Light source 6 Light quantity limiting means 8 CCD 9 Means for limiting irradiation to original 10 Specific portion of reflector 20 Original illumination device

Claims (7)

[Claims] 1. An original illuminating device having 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 original surface, and an image on the original surface is photoelectrically converted. In an image reading apparatus having an optical system for forming an image on a CCD as a conversion element, a means for limiting the amount of light reaching the CCD surface and a means for limiting irradiation of a document from a specific portion of the reflector are provided. An image reading device having. 2. The image reading apparatus according to claim 1, wherein the means for limiting the amount of light reaching the CCD surface is a filter arranged between the document surface and the CCD surface to reduce the amount of transmitted light. 3. The image reading apparatus according to claim 1, wherein the means for limiting the amount of light reaching the CCD surface is that the reflectance of the reflecting surface of the reflector that reflects the emitted light of the light source and illuminates the original surface is low. . 4. The means for limiting the amount of light reaching the CCD surface is that the reflecting surface of the reflector that reflects the radiated light of the light source and illuminates the original surface is formed by a plane approximation and the light collection rate is low. The image reading device according to item 1. 5. The image reading apparatus according to claim 1, wherein the specific portion of the reflector is a portion where the distance of the illumination light from the light emitting segment through the reflector to the document is the shortest. 6. The means for limiting the irradiation of a document from a specific portion of the reflector is formed by forming a part of the reflector surface as a non-reflecting surface. Image reading device. 7. The means for limiting the irradiation of a document from a specific portion of the reflector is formed by not arranging a reflector surface for illuminating the surface of the document in the specific portion. 1. The image reading device described in 1.