JP2000332967A - Image reading device - Google Patents

Abstract

(57) [Problem] To provide an image reading device which can achieve low cost, high performance and drastic thinning without deteriorating illumination efficiency and without adding new components. An illumination system for illuminating a document and an illumination system.
The first traveling body 3 has a first mirror 3a for reflecting the light beam illuminated by the first traveling body 3 and scans at a constant speed V in the sub-scanning direction, and the second traveling body 3 has a second mirror 4a and a third mirror 4b. A second traveling body 4 that scans at a speed of V / 2, and a first traveling body 3
And an imaging lens 5 for reducing and forming an image of the reflected light of the original 2 via a mirror provided on the second traveling body 4;
In the image reading optical system having the line sensor 6 for photoelectrically converting the original image formed in the step (a), the central portion in the longitudinal direction of the first mirror 3a is cut off on the side where the imaging lens is disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a scanner, for example,
The present invention relates to an image reading device used for a copying machine, a facsimile, and the like.

[0002]

2. Description of the Related Art In an image reading apparatus such as a scanner, a copying machine, a facsimile, etc., a reduced reading optical system in which reflected light of a document illuminated by an illumination system is reflected by a mirror and reduced and formed on a line sensor via an imaging lens. The system is known.
An example of an image reading apparatus using a conventional reduced reading optical system will be described with reference to FIG. 1 showing an embodiment of the present invention. As shown in FIG. 1, the original 2 is placed on the contact glass 1, and the original is illuminated by an illumination optical system 7 arranged below the contact glass 1. The illumination light reflected on the document surface is reflected by a first mirror 3a obliquely provided on the first traveling body 3.
After being reflected in the horizontal direction, the light is reflected by the second mirror 4a and the third mirror 4b provided on the second traveling body 4 and is folded back in the horizontal direction.
The image is reduced and imaged upward. When reading the longitudinal direction of the document 2, the illumination optical system 7 and the first traveling
At a speed parallel to the contact glass 1 from the standby position to the position indicated by the reference numeral 3 '.
Moves parallel to the contact glass 1 from the standby position to the position indicated by reference numeral 4 'at half the speed V / 2 of the first traveling body 3, and reads the entire original.

In recent years, demands for miniaturization of scanners, copiers, facsimile machines and the like having the above-described image reading apparatus have increased, and accordingly, the image reading apparatus itself has to be made thinner. In order to reduce the thickness of the optical system shown in FIG. 1, the space between the first traveling body 3 and the contact glass 1 is reduced, or the second traveling body 4
It is necessary to narrow the space between the second mirror 4a and the third mirror 4b provided in the first mirror.

When the space between the first traveling body 3 and the contact glass 1 is reduced, it is necessary to make the illumination optical system 7 disposed between the first traveling body 3 and the contact glass 1 thin. However, if the illumination optical system 7 is made too thin,
Since the illumination light must be applied to the surface of the contact glass 1 with a large inclination, the illumination light may be totally reflected by the contact glass 1 or the illumination efficiency may be significantly deteriorated. It is difficult to achieve thinning.

When the space between the second mirror 4a and the second mirror 4b provided on the second traveling body 4 is reduced to bring the second mirror 4a closer to the third mirror 4b, the third mirror 4b also approaches the first traveling body 3, and accordingly, the imaging lens 5 also approaches the first traveling body 3. Since the first traveling body 3 passes over the reading lens 5, if the second mirror 4a is brought too close to the third mirror 4b, the first traveling body 3 interferes with the imaging lens 5 and scans the entire original. And the thickness of the optical system is limited.

Also, in a so-called analog copying machine optical system for forming an image of an original on a photoreceptor surface at a magnification of about the same magnification, a first traveling body having a first mirror 3 and second and third moving bodies are also provided.
The second traveling body having a mirror is configured in the same manner as the reduction optical system as shown in FIG. 1 and operates in the same manner. Therefore, in order to reduce the thickness, the line sensor 6 as shown in FIG.
Had the same problems as those using.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a low cost, a high performance and no deterioration in lighting efficiency, without adding new components. It is an object of the present invention to provide an image reading apparatus which can achieve a large thickness reduction.

[0008]

According to a first aspect of the present invention, there is provided an illumination system for illuminating an original, and a first mirror for reflecting a light beam illuminated by the illumination system. A first traveling body that scans at a constant speed V in the scanning direction;
A mirror and a third mirror having a V /
2, a second traveling body that scans at a speed of 2, an imaging lens that reduces and forms an image of the reflected light of the original via mirrors provided on the first traveling body and the second traveling body, and an imaging lens that is formed by the imaging lens. In an image reading optical system having a line sensor for photoelectrically converting the formed original image, a central portion in a longitudinal direction of the first mirror is cut out on a side where the imaging lens is disposed. I do.

According to a second aspect of the present invention, there is provided a first traveling body having an illumination system for illuminating a document and a first mirror for reflecting a light beam illuminated by the illumination system, and scanning at a constant speed V in the sub-scanning direction. A second traveling body having a second mirror and a third mirror and scanning at a speed of V / 2 with respect to the first traveling body;
An imaging lens for imaging reflected light of the original via mirrors provided on the traveling body and the second traveling body, and emitting at least one or more odd-numbered mirrors of light emitted from the imaging lens. In an optical system for a copying machine for forming an image on a photoreceptor surface at a magnification of approximately the same magnification through a first mirror, a central portion in a longitudinal direction of the first mirror is cut off on the imaging lens disposition side. I do.

According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, one side edge in the longitudinal direction of the first mirror is cut away from an end to a center of the first mirror. It is characterized in that a decrease in the amount of light in the peripheral portion is corrected, and the illuminance distribution on the image plane becomes substantially uniform.

According to a fourth aspect of the present invention, in the image reading apparatus of the first, second or third aspect, at least an upper portion of the imaging lens is cut.

According to a fifth aspect of the present invention, in the image reading apparatus of the first, third or fourth aspect, the line sensor is a three-line CCD.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image reading apparatus according to the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the image reading apparatus has a contact glass 1 on which a document 2 is placed, and a first traveling body 3, a second traveling body 4, and an imaging lens 5 below the contact glass 1. , A line sensor 6. In the first traveling body 3,
An illumination optical system 7 for illuminating the original 2 is attached, and the first mirror 3a that reflects the light reflected from the original 2 to the side is formed so that its reflection surface forms an angle of 45 ° with the original surface. It is inclined. The illumination optical system 7 has an appropriate light source, for example, a fluorescent lamp. A second mirror 4a and a third mirror 4b are obliquely provided on the second traveling body 4. Second
The mirror 4a and the third mirror 4b are inclined such that their reflection surfaces are at an angle of 45 ° with respect to the document surface, but their respective reflection surfaces are at right angles to each other. With the third mirror 4b, the first mirror 3a
The reflected light from is folded back.

The imaging lens 6 and the line sensor 6 are on the optical path reflected from the third mirror 4b, and the imaging lens 6 converges the reflected light from the original on the light receiving surface of the line sensor 6 to image the original. Is formed on the light receiving surface of the line sensor 6. The first traveling body 3 and the second traveling body 4 are synchronously movable in a direction parallel to the line sensor 6 and in the horizontal direction in FIG.

Document 2 placed on contact glass 1
The original 2 is illuminated by the light source of the illumination optical system 7 attached to the traveling body 3 in order to read the image information. The illumination light reflected by the document 2 is reflected by a first mirror 3 a provided on the first traveling body 3 in a direction parallel to the contact glass 1 in a horizontal direction. The reflected light from the first mirror 3a is reflected vertically downward by the second mirror 4a provided on the second traveling body 4 and further horizontally by the third mirror 4b. As a result, the second traveling body 4 At the horizontal direction. The reflected light from the third mirror 4b is guided to the image forming lens 5, and the image of the document 2 is formed on the line sensor 6 by the image forming lens 5.

The line sensor 6 comprises photoelectric conversion elements such as CCDs arranged on many lines.
The light from the document surface formed on the light source conversion element by the imaging lens 5 is converted into an electric signal for each line.

In order to read the original in the longitudinal direction (the left-right direction in FIG. 1), the illumination optical system 7 and the first traveling body 3 are integrated with each other at the speed of V from the standby position to the position indicated by the broken line 3 '. At the same time, the second traveling body 4 moves from the standby position to the position indicated by the broken line 4 'at half the speed V / 2 of the first traveling body 3 and scans the entire original, thereby scanning the entire original 2. Reads images. Thus manuscript 2
Line sensor 6 obtained by reading the image of
The electric signal from can be reproduced as an electrostatic latent image on the photoreceptor by inputting it to a laser scanner, for example, and a visible image can be reproduced on a sheet by executing an electrophotographic process. it can.

Since the image forming lens 5 is disposed substantially below the central portion of the image reading device, the first traveling body 3 having the first mirror 3a is used to read the image forming lens when reading the longitudinal direction of the document. Pass the top of 5.

In the image forming apparatus having such a configuration,
For example, while trying to realize light beam reading of image information, if the light amount of the light source is not increased in order to save power and suppress a rise in the temperature inside the apparatus, the light receiving amount in the line sensor 6 due to the speeding up is insufficient. In order to compensate for this, it is necessary to make the imaging lens 5 large in diameter. If the diameter of the imaging lens 5 is large, the outer diameter of the lens becomes large and the light beam incident on the lens spreads, so that the width of the mirror in the lateral direction needs to be widened. For this reason, if the image forming apparatus is to be made compact or the size thereof is to be suppressed while satisfying the above-mentioned requirements, it is necessary to reduce the distance between the first to third mirrors and between these mirrors and the imaging lens 5. Since the distance between them cannot be increased, there arises a problem that when the first mirror 3a moves above the imaging lens 5, the first mirror 3a and the imaging lens 5 interfere with each other.

Therefore, the above-mentioned image is formed at a portion where the imaging lens 5 and the first mirror 3a are in contact with each other, that is, at a lower portion of the longitudinal center of the first mirror 3a, in other words, at the longitudinal center of the first mirror 3a. The arrangement side of the lens 5 was cut.
In this case, even when the first mirror 3a and the imaging lens 5 are arranged close to each other in the vertical direction, they do not interfere with each other, and the image reading apparatus main body can be made thin.

FIG. 2 shows a first example which can be used in the present invention.
FIG. 4 shows an example of the shape of the mirror 3a, and shows a first mirror 3a.
The mirror is cut in various shapes below the central portion in the longitudinal direction of the mirror so as not to interfere with the imaging lens 5. As long as the cut shape does not interfere with the first mirror and the imaging lens, the cut shape may be rectangular as shown in FIG. 2A or triangular as shown in FIG. 2B. Well, Figure 2
The cross section may be elliptical as in (c), and the shape is not particularly limited.

Next, another embodiment of the present invention will be described. In the embodiment shown in FIG. 3, in the optical path reflected from the original 2 of the image reading apparatus shown in FIG. 1, the configuration after the imaging lens 5 is changed from a line sensor to a folding mirror and a photosensitive member. 1 are given the same reference numerals. As shown in FIG. 3, the document 2 is placed on the contact glass 1, and the document 2 is illuminated by the illumination optical system 7 arranged below the contact glass 1. The illumination light reflected by the original 2 is reflected by the first mirror 3a of the first traveling body 3, and then is reflected by the second mirror 4a of the second traveling body 4 and the third mirror 3a.
The light is reflected by the mirror 4b and guided to the imaging lens 5,
The reflected light from the original 2 passing through the imaging lens 5 is reflected by a mirror 8
And an image of the original 2 is formed on the surface of the photoconductor 9 at a magnification of approximately the same magnification. The illustrated photoconductor 9 has a drum shape, and is synchronized with the traveling of the first and second traveling bodies.
Is rotated, so that the original 2 is placed on the surface of the photoconductor 9.
Is formed as an electrostatic latent image. The formation of the electrostatic latent image is a part of a well-known electrophotographic process. By performing a predetermined electrophotographic process, a copy image of the document 2 can be obtained on a transfer sheet.

The number of folding mirrors 8 for guiding the reflected light from the original 2 passing through the imaging lens 5 to the photosensitive member 9 may be any number as long as it is an odd number. Three folding mirrors 8a, 8b, 8c
FIG. 4 shows an example in which is provided. The relationship between the first traveling body 3 having the first mirror 3a and the imaging lens 5 is the same as the example shown in FIG. Therefore, the first mirror 3a
The first mirror 3a and the imaging lens 5 are cut by cutting the lower part of the central portion in the longitudinal direction, that is, the side where the imaging lens 5 is disposed.
, And even if the diameter of the imaging lens 5 is increased, interference between the first mirror 3a and the imaging lens 5 can be avoided, and the thickness of the image reading apparatus main body can be reduced. it can.

FIG. 5 is a graph showing the relationship between the light flux incident on the imaging lens and the intensity ratio of the light with respect to the aperture efficiency, the cosine fourth law, and the image plane illuminance. As shown in FIG. 5, in the imaging lens, in any of the aperture efficiency, the cosine fourth law, and the image plane intensity, the light intensity ratio decreases as the incident angle increases. That is, it can be seen that there is a property that the illuminance at the peripheral portion is lower than that at the central portion of the lens.
In an image reading device, since it is necessary to obtain an image with uniform illuminance on the image plane, the illuminance distribution of the light source is conventionally made higher at the peripheral portion with respect to the central portion, or the luminous flux at the central portion is provided near the lens. A so-called shading plate for cutting is arranged to make the image plane illuminance uniform. However, if a method is adopted in which the illuminance distribution of the light source is set higher in the peripheral portion than in the central portion, in the case of a halogen lamp, the illuminance unevenness occurs on the image plane unless the number of filaments is increased significantly. There was a problem.

In addition, if the number of filaments is greatly increased in order to make the illuminance uniform, the cost will increase. For xenon lamps and fluorescent lamps,
It is very difficult to obtain an illuminance distribution that makes the light source peripheral part higher than the central part. Further, the method of using a shading plate to make the illuminance distribution on the image plane uniform requires a new component called a shading plate, which causes an increase in cost.

Here, when a shading plate is used,
Ideally, if only the light flux near the center of the imaging lens can be cut, the illuminance distribution on the image plane can be made most efficient.
For that purpose, it is necessary to dispose the shading plate at a position where the optical path between the central part in the longitudinal direction and the peripheral part is separated.

As shown in FIG. 6, the optical path separates as the distance from the imaging lens 5 increases, but if a shading plate is disposed far away from the imaging lens 5,
It interferes with the first traveling body 3 or the second traveling body 4 and cannot be arranged. For this reason, at present, a shading plate is arranged near the imaging lens 5 while allowing the light flux around the lens to be cut to some extent.

Therefore, as shown in FIG. 7 and FIG.
The shape of the mirror 3a depends on the aperture efficiency of the lens and the cosine 4
The lower part of the central part, that is, the side where the imaging lens is disposed, is cut so as to correct a decrease in the peripheral part of the image plane illuminance due to the power law, so that the first mirror 3a has the same effect as when the shading plate is disposed. As a result, the first mirror 3a having the same effect as the shading plate is always at the same position from the imaging lens even when scanning the original surface, and is far from the lens where the luminous fluxes at the central portion and the peripheral portion are largely separated. Since it is arranged at the position, it is possible to perform excellent illuminance correction on the image plane without cutting the light flux in the peripheral portion.

Further, the light source does not need to make the illuminance distribution in the peripheral portion higher than that in the central portion, and it is possible to make the image plane illuminance uniform with any light source. It goes without saying that the cut amount of the mirror can be arbitrarily changed depending on the aperture efficiency of the imaging lens and the characteristics of the cosine fourth law.

As shown in FIGS. 9A and 9B, the imaging lens may have a shape in which a part of the cylindrical surface of the cylindrical lens is cut to form a flat surface. . FIG.
FIG. 9A is a view in which the upper portion, that is, the first mirror arrangement side is cut, and FIG. 9B is a view in which the upper and lower portions are cut. As described above, by cutting at least the upper part of the cylindrical lens and also cutting the image forming lens arrangement side at the central part in the longitudinal direction of the first mirror 3a, compared with the case of using the cylindrical image forming lens Thus, the first traveling body and the second traveling body can be brought closer to each other, and the thickness of the image reading apparatus can be further reduced. It goes without saying that the cut amount of the imaging lens can be set arbitrarily. The cut portion of the imaging lens is desirably a portion that does not affect the imaging performance.

As shown in FIG. 10, a full-color original reading optical system in which the line sensor 6 is a so-called three-line CCD composed of, for example, three line sensors R6a, G6b, and B6c also has a first mirror 3a having a first mirror 3a. The relationship between the one traveling body 3 and the imaging lens 5 is the same as that of each of the embodiments described so far, and the first mirror 3a
By cutting the imaging lens arrangement side of the central part in the longitudinal direction of the first mirror 3a to reduce the width of the central part in the longitudinal direction of the first mirror 3a,
The thickness of the image reading device main body can be reduced.

[0032]

According to the first aspect of the present invention, there is provided an illumination system for illuminating a document, and a first mirror for reflecting a light beam illuminated by the illumination system, and scans at a constant speed V in the sub-scanning direction. A first traveling body, a second mirror, and a third mirror;
A second traveling body that scans the traveling body at a speed of V / 2;
An image forming lens for reducing and forming an image of the reflected light of the original through mirrors provided on the first and second traveling bodies; and a line sensor for photoelectrically converting the original image formed by the image forming lens. In the image reading optical system, since the notch is provided at the center of the first mirror in the longitudinal direction on the side where the imaging lens is arranged, the first mirror and the imaging lens do not interfere with each other, and the space in the image reading apparatus can be reduced. Can be effectively utilized. In addition, it is possible to obtain an image reading device that is low-cost, high-performance, and can be made significantly thin without causing deterioration of illumination efficiency and without adding new components.

According to the second aspect of the present invention, there is provided an illumination system for illuminating an original, and a first mirror for reflecting a light beam illuminated by the illumination system and scanning at a constant speed V in the sub-scanning direction. A traveling body, a second traveling body having a second mirror and a third mirror, and scanning the first traveling body at a speed of V / 2, and provided on the first traveling body and the second traveling body. An image forming lens for forming an image of the reflected light of the original through a mirror, and a light emitting surface of the image forming lens at a magnification of approximately the same magnification through at least one or more odd number of mirrors. In the copier optical system for forming an image on the upper side, the notch is provided on the side where the image forming lens is disposed in the center portion of the first mirror in the longitudinal direction, so that the space in the image reading device is also effective in the analog optical system. It can be used for Moreover,
It is possible to obtain an image reading device that is low-cost, high-performance, and can be made significantly thin without causing deterioration in illumination efficiency and without adding new components.

According to the third aspect of the present invention, in the image reading apparatus according to the first or second aspect, one side surface of the first mirror in the longitudinal direction is cut out from an end to a center thereof,
Corrects the decrease in the amount of light at the periphery of the imaging lens, and the illuminance distribution on the image plane is almost uniform, so that the illuminance on the image plane is excellent without cutting the light flux around the imaging lens. Corrections can be made.

According to the invention described in claim 4, claim 1,
In the image reading device according to Item 2 or 3, since at least the upper part of the imaging lens is cut, the first traveling body and the second traveling body can be brought closer to each other, and the thickness of the image reading device can be further reduced. It can be.

According to the invention set forth in claim 5, claim 1 is
In the image reading device described in 3 or 4, since the line sensor is a 3-line CCD, a small and thin full-color image reading device can be obtained at low cost.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of a reduction reading system that can be used in an image reading apparatus according to the present invention.

FIG. 2 is a plan view showing an example of a cut portion of a mirror that can be used in the present invention.

FIG. 3 is a side view showing another example of a reading system that can be used in the image reading apparatus according to the present invention.

FIG. 4 is a side view showing still another example of a reading system that can be used in the image reading apparatus according to the present invention.

FIG. 5 is a graph showing a relationship between an incident angle of light and an intensity ratio in the aperture efficiency of the imaging lens, the cosine fourth law, and the image plane illuminance.

FIG. 6 is a plan view showing an example of an optical path near an imaging lens that can be used in the present invention.

FIG. 7 is a graph illustrating a relationship between an incident angle of light and an intensity ratio in an image plane illuminance of an imaging lens and a mirror cut amount.

FIG. 8 is a plan view showing another example of a mirror cut portion that can be used in the present invention.

FIG. 9 is a perspective view showing an example of an imaging lens shape that can be used in the present invention.

FIG. 10 is a side view showing still another example of the reduction reading system of the image reading apparatus according to the present invention.

[Explanation of symbols]

 2 Document 3 First running body 3a First mirror 4 Second running body 4a Second mirror 4b Third mirror 5 Imaging lens 6 Line sensor 7 Illumination system

Claims (5)

[Claims] An illumination system for illuminating a document, a first traveling body having a first mirror for reflecting a light beam illuminated by the illumination system and scanning at a constant speed V in a sub-scanning direction, and a second mirror A second traveling body that has a third mirror and scans the first traveling body at a speed of V / 2, and reflected light of a document via mirrors provided on the first traveling body and the second traveling body. In an image reading optical system having an image forming lens for reducing and forming an image and a line sensor for photoelectrically converting the original image formed by the image forming lens, a central portion in a longitudinal direction of the first mirror is An image forming apparatus characterized in that the image forming apparatus is notched on the side where the imaging lens is arranged. 2. An illumination system for illuminating a document, a first traveling body having a first mirror for reflecting a light beam illuminated by the illumination system and scanning at a constant speed V in a sub-scanning direction, and a second mirror. A second traveling body that has a third mirror and scans the first traveling body at a speed of V / 2, and reflected light of a document via mirrors provided on the first traveling body and the second traveling body. And an image forming lens for forming an image on the surface of the photoreceptor at approximately a same magnification through at least one or more odd number of mirrors. In the optical system, an image forming apparatus is characterized in that a central portion in a longitudinal direction of the first mirror is cut off on a side where the imaging lens is disposed. 3. A first side edge portion of the first mirror in a longitudinal direction is cut out from an end portion to a center portion,
3. The method according to claim 1, wherein a reduction in the amount of light at the peripheral portion of the imaging lens is corrected, and the illuminance distribution on the image plane becomes substantially uniform.
The image reading device according to claim 1. 4. The image reading apparatus according to claim 1, wherein at least an upper part of the imaging lens is cut. 5. The image reading apparatus according to claim 1, wherein said line sensor is a three-line CCD.