JPH07203153A - Picture reader - Google Patents

Abstract

PURPOSE:To provide the picture read unit in which the reduction optical system is made small by forming an optical path from an original picture to a photoelectric conversion element to be folded in multiple. CONSTITUTION:An original 3 placed on an original stage 2 is lighted by a line light source 7. A reflected light from the original 3 is reflected on a mirror 4 and reflected in two mirrors 5, 6 whose opposite faces are arranged nearly in parallel and a lens unit 8 forms an image in a line sensor 9 with reduction. A picture read unit provided with the mirrors 4, 5, 6, the lens unit 8 and the line sensor 9 is moved in a direction at a right angle to the main scanning direction of the line sensor 8 to apply subscanning to an original mechanically.

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 for converting two-dimensional image information of an original into a series of time-series electric signals, and is particularly suitable for facsimiles, digital copying machines, color image scanners and the like. It is something.

[0002]

2. Description of the Related Art A reduction image pickup system for reducing and forming an original image on a photoelectric conversion element of a one-dimensional electric scanning type (hereinafter, this scanning is abbreviated as main scanning) such as a line CCD, and a direction perpendicular to the main scanning direction. , A reduction imaging system or mechanical scanning for moving a document (hereinafter, this scanning is abbreviated as sub-scanning),
Image reading devices for converting two-dimensional image information into time-series electric signals are widely used in facsimiles, digital copying machines, image scanners and the like. Then, the image reading apparatus is classified into a fixed original type (reduced imaging system scanning type) and an original feeding type according to the sub-scanning type.

FIG. 10 shows an example of a conventional scanning image reading apparatus of the reduced image pickup system. In this conventional example, a light emitting diode array for illuminating a reading target area of a document, a fluorescent lamp,
Alternatively, a first unit 18 including a line light source 7 such as a line halogen lamp and a mirror 20, and a second unit 19 including two mirrors 21 and 22 having opposing reflecting surfaces arranged at right angles are provided. The document 3 is scanned in conjunction with it. At this time, the second unit is moved by half the distance traveled by the first unit 18.
By moving the unit 19 in the same direction, the optical path distance between the reading area of the original and the licensor 9 is kept constant.

Explaining the optical system, the light emitted from the line light source 7 illuminates the reading area of the original 3, the original image is reflected by the mirror 20, the mirror 21 and the mirror 22 in this order and guided to the lens unit 8. The lens unit 8 forms a reduced image on the line sensor 9.

Further, there is also a method in which a photoelectric conversion element having a film semiconductor formed on a glass substrate is used, and a document is sub-scanned by moving a contact image sensor which forms an image of the document on the photoelectric conversion element at an equal magnification. Widely used as well.

FIG. 11 shows a conventional example of an image reading apparatus using a contact image sensor. In the same example, the line light source 7, the photoelectric conversion element 26 of the film semiconductor, and the equal-magnification lens array 2
The image reading unit 23 provided with 4 moves and scans the document. The original image is formed on the photoelectric conversion element 26 in a one-to-one manner by the equal-magnification lens array 24. An image reading device that uses a contact image sensor does not require a long optical path unlike a reduction optical system.
Suitable for downsizing. Further, since the illumination system and the light receiving unit are housed and moved in one unit, no complicated mechanism is required.

FIG. 12 shows a conventional example of an image reading apparatus which performs sub-scanning by feeding a document. In this example, the original 3 sandwiched between the original glass stage 2 and the original feeding roller 30.
However, by the rotation of the document feed roller 30, the document is fed in the direction of the arrow and the sub-scan is performed. The reflected light from the document 3 emitted by the line light source 7 enters the lens unit 8 via the mirrors 4, 5, and 6 and is reduced and imaged on the line sensor 9. In this conventional example, in order to downsize the apparatus, the optical path on the object field side of the reduced imaging system is folded into a Z shape by the three mirrors 4, 5, and 6.

[0008]

However, in the above-mentioned conventional document fixed type reduced image pickup system scanning type image reading apparatus, the mirror for folding the optical system is separately moved to the first unit and the second unit. Therefore, rattling when moving each unit distorts the position of the light ray reaching the photoelectric conversion element, which leads to a reduction in resolution. Therefore, high mechanical precision is required in spite of the complicated mechanism, and the reduction optical system requires a relatively long optical path length, which causes a problem that the image reading apparatus tends to be large. .

Further, the image reading apparatus using the contact type image sensor has a drawback that the depth of focus is shallower than that of the reduction optical system, and it is not enough to read an original such as a book which has a portion that cannot be in close contact with the original stage. It wasn't suitable. Further, a film-semiconductor photoelectric conversion element generally used in a contact image sensor has disadvantages in response speed and price as compared with a crystalline semiconductor represented by a CCD sensor used in a reduction optical type. Therefore, the reduction optical type is advantageous in order to cope with the increase in reading speed.

Further, in the conventional document feeding type image reading apparatus, the optical path of the reduction optical system is folded by using three mirrors in order to downsize the apparatus. For the purpose of illustration, the second mirror 5 and the third mirror 6
When the number of turns back and forth between and is increased and the incident / emitted angle at each reflection position is decreased, there is a problem that an image other than the predetermined optical path is formed on the photoelectric conversion element and a ghost is likely to occur.

In view of the above problems, the first object of the present invention is to sub-scan an original by integrally moving the entire image reading unit in which the reduction optical system is downsized by folding back the optical path of the original image. Then, the present invention is to provide an image reading device which is small in size, inexpensive, simple in mechanism, suitable for reading originals of a book, and capable of high-speed reading by reading a fixed original. A second object of the present invention is to further reduce the size of the document reading unit by reflecting the document image a plurality of times by two mirrors and folding it back in multiple layers.

A third object of the present invention is to improve the utilization efficiency of light from a light source by adopting a light guide in the illumination system, and to use an image reading apparatus which can use a light source which is smaller or consumes less power than before. Is to provide. A fourth object of the present invention is to reduce the size of the sub-scanning moving unit by separating the moving image reading unit and the light source, to save the power required for moving, to reduce the size of the drive motor, and the like. Another object of the present invention is to provide an image reading device that can use a large light source.

A fifth object of the present invention is to prevent the occurrence of a ghost in which an image other than a predetermined optical path is formed on a photoelectric conversion element in a document feeding type image reading apparatus, while preventing the occurrence of a ghost. It is an object of the present invention to provide an image reading apparatus in which the optical system is downsized by increasing the number of turns back and forth between the optical scanning unit and the optical scanning unit.

[0014]

In order to solve the above problems, the present invention has the following constitution. That is, according to the present invention, a translucent flat plate on which an original is placed, an illuminating means for illuminating the original, and two mirrors in which the reflection surfaces of the original reflected from the original are arranged substantially parallel to each other are folded back. Then, a reduction image pickup means for reducing and forming an image on a photoelectric conversion element that is electrically linearly scanned, and a mechanical device for moving the reduction image pickup means as a unit in a direction perpendicular to the scanning direction of the photoelectric conversion element to scan the document. An image reading apparatus comprising: a scanning unit.

In the present invention, the optical path passing through the two mirrors can be reflected a plurality of times on the reflecting surfaces of the respective mirrors.

Further, according to the present invention, an illuminating means for illuminating a document, a reduction image pickup means for reducing and forming a reflected light from the document on a photoelectric conversion element which is electrically linearly scanned, and a reduction image pickup means for the document. In the image reading apparatus including at least two mirrors inserted in the optical path up to the above, and a mechanical scanning unit that moves the document in a direction perpendicular to the scanning direction of the photoelectric conversion element, The image reading apparatus is characterized in that reflected light is reflected a plurality of times by the respective reflecting surfaces of two mirrors arranged such that the reflecting surfaces facing each other are substantially parallel and is incident on the reduced image pickup means.

Further, in the present invention, the optical path passing through the two mirrors is incident from a side having a wide mirror gap, reaches a side having a narrow mirror gap by a plurality of reflections, and is again reflected by a plurality of reflections. The above 2
The mirrors can be arranged with a narrow included angle.

Further, in the present invention, the reduced image pickup means may include a flat-shaped imaging lens long in the scanning direction of the photoelectric conversion element and short in the direction perpendicular to the scanning direction.

Further, in the present invention, a light guide body made of a transparent medium can be provided on at least a part of an optical path from the light source of the illumination means to the reduced image pickup means.

[0020]

In the image reading apparatus according to the present invention configured as described above, since the optical path of the reduction optical system requiring a length is folded using two mirrors, the image reading unit is small and lightweight. Can be provided. Further, by providing a sub-scanning mechanism that integrally slides the unit for scanning the document, a complicated mechanism for interlocking individual optical elements or a plurality of optical element groups forming a reduction optical system as in the past can be provided. It is possible to provide a fixed document type image reading apparatus without using it. This contributes to downsizing of the device, simplification of the mechanism, improvement of reliability, and cost reduction. Further, the reduction optical system image reading device can use a crystal semiconductor typified by a CCD sensor for a photoelectric conversion element, and thus is suitable for high speed operation.
It is a low price. Further, since the reduction optical system has a depth of focus deeper than that of the contact type, it is suitable for reading an original that easily floats from an original stage such as a book.

Further, by using an optical system in which an original image is reflected a plurality of times between two mirrors and is folded back multiple times, the optical path of the reduction optical system can be further folded, so that the size can be further reduced. Also, by adopting a light guide in the illumination system, the light confining effect of the light guide suppresses the divergence of light from the light source, and it becomes possible to use the light effectively, so A power-saving light source can be used. As a result, the image reading device can be downsized, or the cost of the light source used can be reduced. In addition, by fixing the light source separately from the image reading unit and providing the sliding image reading unit with a reflection mirror, the light radiated toward the document image reading unit is reflected and condensed by the reflection mirror, and the reading area of the document is Illuminate. Therefore, a large light source that is unsuitable for moving, for example, three line light sources of RGB three primary colors can be used for illuminating the original.

Further, in the image reading apparatus having the above structure, two mirrors are provided in the reduced image pickup optical system in parallel with the main scanning direction of the photoelectric conversion element, and the reflection surfaces of the two mirrors are included at a small angle θ (θ ≠ 0). It is possible to fold the optical path by arranging so as to be opposed to each other with the sheet sandwiched therebetween and alternately reflecting the reflected light from the original document by the two reflecting surfaces a plurality of times. For example, as shown in FIG. 7, the folding of the optical path is performed such that the first reflected light travels from the side where the two mirrors are wide to the side where the two mirrors are narrow.
Incident angle ψ for either one of the two mirrors
It is incident at _in (ψ _in ≠ m · θ, m = 0,1,2,3, ...). The light from the original reflected by one of the mirrors has an exit angle (=
Incident angle) ψ _in toward the other mirror, but since the two mirrors are arranged so as to have an included angle θ, the next incident angle becomes ψ _in −θ, and the output angle ψ _in from the other mirror −θ
After being reflected by, the light is again incident on one mirror at the incident angle ψ _in −2θ by the same principle.

In this way, the reflected light from the original is repeatedly reflected between the two mirrors facing each other, and the optical path is folded. In this process, the reflection position on the reflection surface moves in the direction in which the distance between the two mirrors becomes narrower as the number of reflections increases, but the incident angle (= reflection angle) ψ _n in the _nth reflection is ψ _n = ψ _in − (n−1) θ,
When ψ _n <0, the reflection direction is reversed, and the subsequent reflection position moves in the direction in which the distance between the two mirrors increases, and finally the light is emitted from the side where the distance between the two mirrors is wide.

In this optical system configuration, at the final reflection position immediately before the light is emitted from the two mirror systems, the difference in the light emission angle from the adjacent reflection position is the largest, so that the ghost is generated on the photoelectric conversion element. Is greatly suppressed.

Further, by using a flat-shaped image forming lens in which a part of the outer shape is cut in parallel with the main scanning direction of the photoelectric conversion element in the lens unit, without reducing the angle of view in the main scanning direction, The lens diameter in the direction perpendicular to the main scanning direction can be reduced, and the optical system can be made thinner.

[0026]

Embodiments of the present invention will now be described in detail with reference to the drawings. (First Embodiment) FIG. 1 shows a sectional view of the essential parts of a first embodiment of the document reading apparatus according to the present invention. In FIG. 1, manuscript 3
Is placed and fixed on the original stage 2 made of a transparent flat plate. The image reading unit 1, which is a reduction image pickup unit, includes a line light source 7 that illuminates an original, a first mirror 4, and a second mirror 5 that is a pair of mirrors having opposing reflecting surfaces arranged substantially parallel to each other. The third mirror 6, the lens unit 8 and the line sensor 9 are integrated and can be reciprocated in the direction of the arrow by a sub-scanning mechanism which is a mechanical scanning means (not shown).

Then, the reflected light from the reading area of the document illuminated by the line light source 7 is converted into a one-dimensional intensity distribution of the light by the lens unit 8 via the mirrors 4, 5 and 6 which turn the imaging optical system back. Image is reduced and imaged on the line sensor 9 which is mainly scanned and converted into an electric signal. Here, as the line light source 7, an LED array, a fluorescent lamp, a linear halogen lamp, or the like is used.

FIG. 2 shows a conceptual diagram of a sub-scanning mechanism for sub-scanning the image reading unit 1. Guide rails 10 are provided at both ends of the image reading unit 1 so as to reciprocate in a fixed direction. The moving means is generally a method in which a wire is attached to the image reading unit and the movement is controlled by a motor.

(Modification of First Embodiment) FIG. 3 is a sectional view showing the principal part of an image reading unit which is a modification of the first embodiment. The difference from the first embodiment is that the optical path of the original image is the mirror 5
And the mirror 6 is multiply folded. In this way, by repeatedly folding the optical path of the reduction optical system, a long optical path length required for the reduction optical system can be taken in spite of the small image reading unit.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
1 illustrates an image reading device including a light guide 11. In order to read the document 3 placed on the document stage 2, the line sensor 9, the lens unit 8, the mirrors 5 and 6, and the light guide 1 are arranged.
A document reading unit 1 including 1 and a line light source 7 slides in a direction indicated by an arrow in the figure to sub-scan the document 3. The light emitted from the light source 7, including the light reflected by the reflection plate 12, is introduced into the light guide 11.

The light thus guided to the light guide 11 reaches the original 3 as illumination light from the end face 13 of the light guide 11. On the other hand, the original image is input from the end surface 13 of the light guide 11,
The light reaches the mirror 5 by reflection inside the light guide 11, and is folded back between the mirror 5 and the mirror 6. The light emitted from the light source 7 is suppressed by the light confining effect of the light guide 11 so that the divergence of the light is suppressed and the loss of the original 3 is relatively small.
Can be supplied with light. Further, since the illumination light is output and the original image is input on the same end face 13 of the light guide 11,
The end surface 13 can be brought close to the original 3.

In the case of a relatively large light source such as a fluorescent lamp, if the light source and the original are brought close to each other to increase the illuminance, the optical path of the image of the original is blocked, so the distance between the light source and the original must be increased. However, when the original 3 is illuminated with the light from the light source 7 through the light guide 11 of the present invention, the light source 7 does not block the optical path of the original image, and the light from the light source 7 can be effectively used. . From the viewpoint of effective use of light, a light source that is smaller and consumes less power than conventional light sources can be used, so that the device can be downsized and the power consumption can be reduced.

FIG. 5 shows a perspective view of an illumination system using the light guide 11. A reflector 12 is provided between the line light source 7 and the light guide 11.
Of the light emitted from the light source 7 to directly guide the light guide 11
Light emitted in a direction not input to the light guide 11 can be guided to the light guide 11 by being reflected by the reflector 12. Therefore, the light source 7
It is possible to effectively use the light from the source 3 to illuminate the original 3.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
1 shows an image reading device in which a light source and an image reading unit are separated. The image reading unit 1 has a line sensor 9
The lens unit 8, the mirrors 4, 5, 6 and the reflection mirror 17 for guiding the light from the light source 15 to the reading line area of the original 3. Further, the light source 15 is arranged on the extension line of the traveling direction with respect to the image reading unit 1 moving on the document stage 2, and the light emitted from the light source 15 by the collimating lens 16 is aligned to some extent to make the image reading unit 1. Light rays are output in parallel to the traveling direction of 1. The light beam is received by the reflection mirror 17 in the image reading unit 1, reflected and condensed to illuminate the reading area of the original 3.

In this system, since it is not necessary to move the light source, it is possible to use a light source that is not suitable for movement. For example, three RGB light sources for reading a color image,
A light source or the like which requires a heat radiating means can also be used in the fixed document type image reading apparatus. A color image can also be obtained by using a light source equipped with a means for separating the RGB three primary colors by a wavelength selection means such as a dichroic mirror or an optical filter from a white light source in the image reading apparatus of this example.

(Fourth Embodiment) FIG. 8 is a sectional view showing the main part of a document feeding type image reading unit according to the fourth embodiment. In the figure, the image reading unit of the present embodiment has a plurality of LED lamps 42 at the bottom inside a light-shielding housing 41.
A light guide substrate 43 whose upper end is the original stage surface 2 on which the original 3 is placed, a first mirror 4, and two mirrors whose opposing reflecting surfaces are arranged substantially parallel to each other. 2 mirror 5, 3rd mirror 6, and lens unit 8
And a line sensor 9 are provided. Also, the housing 4
An upper part of the document 1 is provided with a document feed roller 30 that faces the document stage surface 2 and feeds the document 3 with the document 3 sandwiched therebetween to perform mechanical sub-scanning.

The first mirror 4 and the third mirror 6 are integrally formed by directly vapor-depositing a metal having a high reflectance such as aluminum on the end surface of the light guide substrate. The second mirror 5 is a plane mirror formed by vapor-depositing a high-reflectance metal on a normal plane glass substrate, and faces the third mirror 6 formed on the surface of the light guide substrate 43 in the Y direction. It is arranged with an inclination of 4 degrees. That is, the included angle between the second mirror 5 and the third mirror 6 is 4 degrees. It is desirable that the surface of each mirror be coated to increase the reflectance.

The lens unit 8 displays the image of the original 3 on the original stage 2 on the light receiving surface of the line sensor 9 by 0.112.
It is arranged so as to form a double reduced image, and is composed of a flat lens set whose appearance is shown in FIG. According to FIG. 9, each of the lenses 8-1 and 8-2 forming the lens unit 8 is linearly cut in parallel with the X direction which is the main scanning direction of the photoelectric conversion element. Therefore, the height (Y direction) of the lens barrel is smaller than that in the main scanning direction (X direction), and the lens barrel is of a flat type.

Next, the operation of the fourth embodiment having the above construction will be described. A plurality of LEs provided on the bottom of the light guide substrate 43
Most of the light emitted from the D lamp 42 enters the light guide substrate 43 at an angle equal to or greater than the critical angle, is confined inside with almost no loss due to the total reflection effect, and is emitted from the document stage surface 2 to cause the original document to exit. Illuminate 3.

The light reflected from the original 3 is reflected by the light guide substrate 43.
After passing through the inside of the sheet, is reflected by the first mirror 4, and the optical path is bent in a direction substantially parallel to the document surface 3, the lower part of the surface of the light guide substrate 43 where the third mirror 6 is provided is transparent. The light is emitted from the portion 44 to the outside of the light guide substrate 43.

The light emitted from the light guide substrate 43 enters the second mirror 5 at an incident angle of 10 degrees with respect to the Y direction, and is reflected in a direction in which the distance between the second mirror 5 and the third mirror 6 is narrowed. (Hereinafter, when the light travels in the direction in which the distance between the second mirror 5 and the third mirror 6 is narrowed, the incident and outgoing angles are indicated by +, and the opposite is indicated by-)

The light reflected by the second mirror 5 reaches the third mirror 6, but since the second mirror 5 and the third mirror 6 are installed at an included angle of 4 degrees as described above, As shown in FIG. 7, the incident angle on the third mirror 6 is 10 degrees −4.
Degree = 6 degrees. (In this embodiment, θ = 4 degrees, ψ _in = 1
0 degree)

Light incident at an incident angle of 6 degrees is reflected by the third mirror 6
After being reflected by, the light is again incident on the second mirror 5 at an incident angle of 6 ° −4 ° = 2 °, and is reflected at the same angle. In this way, the light reflected from the original is alternately reflected by the second mirror 5 and the third mirror 6 whose reflecting surfaces facing each other are arranged at an included angle of 4 degrees. In the process, the third mirror 6 After the second reflection in, the incident angle becomes negative, the reflected light travels in the direction in which the distance between the second mirror 5 and the third mirror 6 widens, and finally enters the lens unit 8 and the line sensor 9 The original image is reduced and imaged on.

Although the preferred embodiments have been described above, these embodiments are not intended to limit the present invention, and various modifications and changes can be made within the scope of the present invention described in the claims. It is possible.

[0045]

As described above, the present invention has the following effects. (1) In a fixed document type image reading apparatus in which a reduction imaging type image reading unit performs sub-scanning while a document is fixed, an optical path of a reduction optical system that requires a relatively long optical path is folded using two mirrors. Therefore, it is possible to provide a small and lightweight image reading unit.
Further, by providing a mechanism for integrally sliding the unit to scan the document, a conventional individual optical element or a complicated mechanism for interlocking a plurality of optical element groups constituting the reduction optical system is used. It is possible to provide a fixed document type image reading apparatus without using the image reading apparatus. This contributes to downsizing of the device, simplification of the mechanism, improvement of reliability, and cost reduction. Further, since the image pickup means using the reduction optical system uses a crystal semiconductor such as CCD, it has advantages of high-speed response and low price, and the image reading apparatus equipped with the means is suitable for high reading speed or low price. . Further, since the reduction optical system has a depth of focus deeper than that of the contact type, it is suitable for reading an original that easily floats from an original stage such as a book.

(2) If an image reading unit that employs an optical system in which an original image is reflected a plurality of times between two mirrors and is folded back in multiples is used, the optical path of the reduction optical system can be further folded, so that the size can be further reduced. can do. (3) By adopting a light guide for the illumination system, the light confining effect of the light guide enables effective use of the light from the light source. Can be used. As a result, the image reading device can be downsized, or the cost of the light source used can be reduced. (4) To move the image reading unit that slides on the document stage by using an image reading unit equipped with a means for inputting light from an external light source and guiding it to the document without placing the light source on the image reading unit. An inappropriately large light source, for example, three line light sources of RGB three primary colors can be used for illuminating the original. In addition, since the image reading unit can be further downsized by using the separate light source, the device can be downsized, or the load on the drive motor can be reduced, and downsizing or power saving can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an image reading apparatus according to a first embodiment.

FIG. 2 is a conceptual diagram of a sub-scanning mechanism of the image reading unit.

FIG. 3 is a cross-sectional view of the main parts of an image reading unit that is a modification of the first embodiment.

FIG. 4 is a cross-sectional view of a main part of an image reading device according to a second embodiment.

FIG. 5 is an exploded perspective view of an illumination optical system using a light guide.

FIG. 6 is a cross-sectional view of essential parts of an image reading device according to a third embodiment.

FIG. 7 is an explanatory diagram of optical path multiple folding in the present invention.

FIG. 8 is a cross-sectional view of essential parts of an image reading device according to a fourth embodiment.

FIG. 9 is a structural diagram of a lens unit according to a fourth example.

FIG. 10 is a cross-sectional view of a main part of a document fixed / reduced image pickup type image reading apparatus of a conventional example.

FIG. 11 is a cross-sectional view of a main part of a conventional fixed document contact type image reading apparatus.

FIG. 12 is a cross-sectional view of essential parts of a document feeding type image reading apparatus of a conventional example.

[Explanation of symbols]

 1 Image reading unit 2 Original stage 3 Originals 4, 5, 6 Mirror 8 Lens unit 9 Line sensor 10 Guide rail

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hitoshi Ikeda 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Inventor Shochika Kato 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside the company

Claims (6)

[Claims] 1. A translucent flat plate on which an original is placed, an illuminating unit for illuminating the original, and two mirrors whose reflection surfaces facing each other reflect reflected light from the original are substantially parallel to each other. And a reduction image pickup means for reducing and forming an image on the photoelectric conversion element which is electrically linearly scanned, and a mechanical device for moving the reduction image pickup means as a unit in a direction perpendicular to the scanning direction of the photoelectric conversion element to scan the document. An image reading apparatus comprising: a scanning unit. 2. The image reading device according to claim 1, wherein an optical path passing through the two mirrors is reflected a plurality of times on a reflecting surface of each mirror. 3. An illumination unit for illuminating an original document, a reduction image pickup unit for forming a reduced image of reflected light from the original document on a photoelectric conversion element that is electrically linearly scanned, and from the original document to the reduction image pickup unit. An image reading apparatus including at least two mirrors inserted in the optical path and a mechanical scanning unit that moves the document in a direction perpendicular to the scanning direction of the photoelectric conversion element, the reflected light from the document is An image reading apparatus characterized in that reflecting surfaces facing each other are reflected a plurality of times on respective reflecting surfaces of two mirrors arranged substantially in parallel and are incident on the reduced image pickup means. 4. The optical path according to claim 2 or 3, wherein the optical path passing through the two mirrors is incident from a side having a wide mirror gap, reaches a side having a narrow mirror gap by a plurality of reflections, and is again reflected. An image reading apparatus, characterized in that the two mirrors are arranged so as to have a narrow included angle so that the two mirrors emit light from a side with a wider interval by reflection. 5. The reduction image pickup device according to claim 1, further comprising a flat imaging lens that is long in a scanning direction of the photoelectric conversion element and short in a direction perpendicular to the scanning direction. Characteristic image reading device. 6. The light guide body made of a transparent medium according to claim 1, wherein a light guide body made of a transparent medium is provided in at least a part of an optical path from a light source of the illumination means to the reduced image pickup means. Characteristic image reading device.