JP2000209400A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the conveyance time when both the surfaces of a document are read without increasing the device cost. SOLUTION: This device 1 has a conveyance path 2 which comprises conveyor rollers 5, 6, and 7 and inverts a document G once, an image pickup unit 13 which photodetects and photoelectrically converts reflected light from the document R1 at a position R1 before the document G is inverted once and a position R2 after the single inversion, an illumination lamp 9 which lights up the top surface of the original G at the position R1, and an illumination lamp 10 which lights up the rear surface of the document G at the position R2. To read the top surface of the document G, the image pickup unit 13 is set at the standard position P1, the illumination lamp 9 is turned on, and the illumination lamp 10 is turned off. To read the rear surface of the document G, the image pickup unit 13 is moved by the straight distance between the positions R1 and R2 along the optical axis, the illumination lamp 9 is turned off, and the illumination lamp 10 is turned on.

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 used for a copying machine, a scanner, and the like.
The present invention relates to an image reading apparatus capable of reading both sides of a document in a short time.

[0002]

2. Description of the Related Art As a conventional image reading apparatus, an original is automatically conveyed and an image of the original is read, such as a scanner having an automatic document feeder (ADF) or a reading section of a copying machine having an ADF. There are devices that read optically.

FIG. 7 is an explanatory diagram showing the configuration of a conventional image reading apparatus (reading section of a digital copying machine having an ADF). The image reading apparatus 200 includes an ADF 101 that automatically conveys a document and an image reading unit 1 that optically reads the document.
The ADF 101 includes a document tray 111 for placing a document, and a document tray 111.
The document feeding mechanism 112 and the transport belt 113 for transporting the document placed on the scanner to an image reading position (on a contact glass 102 described later), and the document at the image reading position is inverted and discharged or returned to the image reading position. It comprises a transport roller 114 for transport and a separation claw 115.

The image reading unit 100 includes an ADF 101
Glass 102 for holding the original conveyed by the scanner at the image reading position, and illumination lamp 1 for irradiating the original with light
03, a first mirror 104, a second mirror 105, a third mirror 106, and a lens 107 for guiding reflected light from a document.
A CCD sensor 108 for photoelectrically converting the reflected light image condensed by the lens 107 and outputting a digital signal;
Various kinds of image processing (for example, binarization, multi-level conversion, gradation processing, scaling processing,
And an image processing unit 109 that performs editing processing.

[0005] In the above configuration, the operation when reading both sides of a document will be described. When reading both sides of an original, the operator places the original on the original tray 1 on the ADF 101.
When the document is set at 11, the document is transported to the image reading position on the contact glass 102 by the document feeding mechanism 112 and the transport belt 113. The original conveyed to the image reading position on the contact glass 102 is
Is reflected by the lens 10 via the first mirror 104, the second mirror 105, and the third mirror 106.
7 forms an image on the CCD sensor 109. The CCD sensor 109 photoelectrically converts the reflected light image formed by the light from the lens 107, outputs a digital signal, outputs the digital signal to the image processing unit 109, and the image processing unit 109 performs various processing on the digital signal. Image processing is performed.

On the other hand, when the reading of one side of the original is completed, the original is conveyed to the conveying roller 114 by the conveying belt 113, reversed by the direction of the separation claw 115, and conveyed again to the image reading position on the contact glass 102. Here, the image on the back side of the document is read. Thereafter, the document is transported to transport rollers 114 by transport belt 113,
The sheet is discharged out of the apparatus depending on the direction of the separation claw 115.

[0007]

However, according to the conventional image reading apparatus, when reading both sides of a document, the conveying paths from the end of reading the front side of the document to the end of the reading after the reading of the back side are overlapped. For this reason, there is a problem that the conveyance time accounts for a large proportion of the total time for reading a double-sided document, and it takes time to read a double-sided image.

On the other hand, by arranging a CCD sensor for reading the front surface and a CCD sensor for reading the back surface, it is possible to shorten the transport time. However, since the cost of the CCD sensor itself is high, the cost of the entire apparatus is high. There was a problem that it would.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image reading apparatus capable of shortening the transport time when reading both sides of a document without increasing the cost of the apparatus. And

[0010]

To achieve the above object, an image reading apparatus according to a first aspect of the present invention conveys a document along a conveyance path having a reversing portion for reversing the front and back of the document. A document conveying means, a first light source for irradiating the document with light at a first reading position located on the upstream side with respect to the position of the reversing section on the conveyance path, A second light source that irradiates the document with light at a second reading position that is located on the downstream side with respect to the document, a reflected light of light that is radiated from the first light source to the document, and a light that irradiates the document from the second light source Photoelectric conversion means for receiving the reflected light of the converted light and converting the reflected light into an electric signal; and an optical path length of the reflected light from the first reading position to the photoelectric conversion means and the photoelectric conversion from the second reading position. So that the optical path length of the reflected light to the means is the same Moving means for moving the serial photoelectric converter along the optical axis of the reflected light, but with a.

That is, in the image reading apparatus of the first aspect,
When reading the front side of the document passing through the first reading position by the photoelectric conversion unit, inverting the document once by the reversing unit of the document conveying unit, and reading the back surface of the document passing through the second reading position by the photoelectric conversion unit The moving means may move the photoelectric conversion means so that the optical path length of the reflected light from the first reading position to the photoelectric conversion means is equal to the optical path length of the reflected light from the second reading position to the photoelectric conversion means. Move along the optical axis of the reflected light. As a result, both sides of the document can be read only by inverting the document once and phase-shifting the photoelectric conversion means, and the transport time is shortened by shortening the transport path.

According to a second aspect of the present invention, there is provided the image reading apparatus according to the first aspect, further comprising: a passage determining unit configured to determine whether the document has passed the first reading position; Light source switching means for performing lighting switching control of the first light source and the second light source based on the determination result of the passage determination means, and And moving the photoelectric conversion means along the optical axis of the reflected light.

That is, in the image reading apparatus of the second aspect,
The passage determining means determines whether or not the document has passed the first reading position.
The lighting switching control for turning off the light source and turning on the second light source is performed. When the light passes, the moving means moves the photoelectric conversion means along the optical axis of the reflected light. Therefore, lighting switching of the light source and movement of the photoelectric conversion unit can be performed at appropriate timing.

According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, further, the image reading apparatus has at least the same width as a document reading width read by the photoelectric conversion means; A transparency variable member disposed at the first reading position and having variable transparency; and transparency control means for controlling the transparency of the transparency variable member, wherein the transparency control means determines whether the position of the document is the first position. In the case of the reading position, the transparency of the variable transparency member is controlled to a low state, and when the position of the document is the second reading position, the transparency of the variable transparency member is controlled to a high state.

That is, in the image reading apparatus of the third aspect,
Since the transparency of the transparency changing member when reading the surface of the document is low, the light from the light source does not pass through the document or the transparency changing member, and it is possible to prevent the surface image from being darkened due to insufficient light intensity.

According to a fourth aspect of the present invention, in the image reading apparatus of the third aspect, the image reading apparatus further includes a maximum transparency of the variable transparency member with respect to the image read at the second reading position. It is provided with a density correcting means for performing image density correction based on transmittance.

That is, in the image reading apparatus of the fourth aspect,
When reading the back side of the document, the reflected light from the document is received by the photoelectric conversion means via the transparency variable member,
The light intensity decreases due to the transparency of the transparency variable member, and the rear image becomes slightly darker than the front image. However, by performing image density correction based on the maximum transmittance of the transparency variable member, this light intensity is reduced. , The front image and the back image can be read with the same image quality.

According to a fifth aspect of the present invention, there is provided an image reading apparatus comprising: a document conveying means for conveying a document along a conveyance path having a reversing portion for reversing the front and back of the document; A first light source for irradiating the document with light at a first reading position located on the upstream side, and a document at a second reading position located on the downstream side with respect to the position of the reversing unit on the transport path. A second light source for irradiating light;
The reflected light of the light emitted from the light source to the original and the second light
Photoelectric conversion means for receiving reflected light of light emitted from the light source to the original and converting the reflected light into an electrical signal; reflected light of light emitted from the first light source to the original and light from the second light source to the original A reflection mirror for guiding the reflected light of the light applied to the photoelectric conversion means, and the optical path length of the reflected light from the first reading position to the photoelectric conversion means, and from the second reading position to the photoelectric conversion means. Moving means for moving the reflection mirror along the optical axis of the reflected light so that the optical path length of the reflected light becomes the same.

That is, in the image reading apparatus of the fifth aspect,
When reading the front side of the document passing through the first reading position by the photoelectric conversion unit, inverting the document once by the reversing unit of the document conveying unit, and reading the back surface of the document passing through the second reading position by the photoelectric conversion unit The moving means reflects the reflection mirror so that the optical path length of the reflected light from the first reading position to the photoelectric conversion means is equal to the optical path length of the reflected light from the second reading position to the photoelectric conversion means. Move along the optical axis of light. As a result, both sides of the document can be read only by inverting the document once and phase-shifting the photoelectric conversion means, and the transport time is shortened by shortening the transport path.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image reading apparatus according to the present invention will be described in detail in the order of [Embodiment 1] to [Embodiment 3] with reference to the accompanying drawings. The present invention is not limited by the embodiments.

[Embodiment 1] FIG. 1 is a block diagram of an image reading apparatus according to Embodiment 1 of the present invention. In the image reading apparatus 1, the original G is inserted from the original insertion slot 3,
The sheet is transported along the transport path 2 including the transport rollers 5, 6, and 7, a front image is read at a position R1 (first reading position), and a back image is read at a position R2 (second reading position). The sheet is discharged to the discharge tray 4. The document is inverted once by the transport rollers 6 and 7. The arrow A in the figure
Indicates the transport direction of the document G.

The original position detecting sensor 11 detects the position of the leading end of the original G conveyed by the conveying rollers 6 and 7. The illumination lamp 9 illuminates the document G passing over the contact glass 12 at the position R1. Lighting lamp 10
Illuminates the original G at the position R2.

The reflected light from the original G is guided to the image pickup unit 13 by the mirror 14. Here, the imaging unit 13 includes a lens 15 for imaging reflected light from the original G, and a CCD sensor that photoelectrically converts the reflected light image formed by the light from the lens 15 and outputs a digital signal. 16 The image processing board 20 performs various image processing (for example, binarization, multi-value processing, gradation processing, scaling processing, editing processing, etc.) on the digital signal from the CCD sensor 16.

The image pickup unit 13 is set at the standard position P1 when reading the front side of the document G. As shown in FIG. 2, when reading the back surface of the document G, the imaging unit 13 is moved to the movement position P2. The distance D between the standard position P1 and the movement position P2 is equal to the linear distance between the position R1 and the position R2.

As shown in FIG. 3, the imaging unit 13
It is fixed to a substrate 23 having a gear formed on its surface, and is configured to be movable along the optical axis of the reflected light by a gear 22 and a motor 18 corresponding to the moving means of the present invention.

The components described above are accommodated in the outer case 21. Although not shown, the outer case 21 is provided with an operation panel having buttons for instructing the number of copies and one-sided / two-sided reading.

FIG. 4 is a block diagram of the image reading apparatus 1. As shown in FIG. As shown in FIG. 1, in the image reading apparatus 1, the image processing board 20 converts an analog signal received by the CCD sensor 16 into a digital signal and transfers the digital signal.
A BU (Sensor Board Unit) 40, a video signal control unit 41 for controlling a video signal, an image processing unit 42 for performing various image processing on the acquired image, and a RAM 43 for recording data such as image data. , A ROM 44 for recording programs, etc., the document position detection sensor 11,
A motor driver 45 for controlling the transport motor 51 and the unit motor 52; an illumination lamp control circuit 46 for controlling lighting and extinguishing of the illumination lamps 9 and 10;
The CPU 47 that controls the entire operation of the CPU 0 and an interface 48 are connected by a bus 49. Further, information from the operation panel 50 is supplied to the image processing board 20. Based on this information, the image processing board 20 performs various image processing on the image. When storing image data in the RAM 43, the data is compressed and stored.
When outputting image data from the RAM 43 to the interface 48, the storage capacity of the RAM 43 is reduced by expanding the data.

Next, the operation of the image reading apparatus 1 will be described with reference to FIGS. When reading both sides of the document, the operator operates the buttons on the operation panel 50 on the outer case 21 to instruct double-side reading, and sets the document G in the document insertion slot 3. Next, when the operator operates the buttons on the operation panel 50 and instructs to start reading the original,
The illumination lamp control circuit 46 turns on the illumination lamp 9 (confirms that the illumination lamp 10 is turned off at the same time).
The conveyance roller 5 is rotated by the drive of
Are transported in the transport direction indicated by. At this time, the imaging unit 13 is set at the reference position P1.

As shown in FIG. 1, when the document G reaches the position R1, light is illuminated on the surface of the document G by the illumination lamp 9, and the reflected light from the surface of the document G is transmitted through the mirror 14 to the image pickup unit 13 And the reading of the front surface image of the document G is started. Then, manuscript G
When the rear end of the document G has passed the position R1, the reading of the front surface image of the document G is completed. Thereby, a front surface image of the document G can be obtained.

When the reading of the front surface image of the original G is completed, as shown in FIG.
Move to 2. On the other hand, the original G is transported by rollers 5, 6, 7
And once inverted. Document position detection sensor 1
1 detects the position of the leading end of the document G, the illumination lamp control circuit 46 turns off the illumination lamp 9 and turns on the illumination lamp 1.
Lights 0. When the original G reaches the position R2, the original G
Is illuminated by the illumination lamp 10 and the reflected light from the back of the document G is reflected by the contact glass 12 and the mirror 1.
The document G is guided to the CCD sensor 16 of the image pickup unit 13 via 4 and reading of the back surface image of the document G is started.

Thereafter, when the rear end of the original G passes the position R2, the reading of the back surface image of the original G is completed. As a result, a backside image of the document G can be obtained. When the reading of both sides of the document G is completed, the document G is transported by the transport rollers 5 and discharged to the discharge tray 4. Then, the imaging unit 13 returns (moves) to the reference position P1.

As described above, the position when reading the front surface of the document G is R1, and the position when reading the back surface of the document G is R2. Here, it is assumed that a straight line distance between the positions R1 and R2 is D. Imaging unit 1 for reading the surface
If the back side is read from the same position as the position P1 of No. 3, since the optical path length becomes longer by the distance D, the image quality of the back side image deteriorates. Therefore, by moving the imaging unit 13 from the position P1 to a position P2 closer to the position R2 by a distance D in the optical axis direction of the reflected light, the optical path length for reading the front surface and the optical path length for reading the back surface are equal. Thus, deterioration of the image quality of the back side image is prevented.

As described above, in the image reading apparatus 1 of the first embodiment, the surface of the original G is read at the position R1 by the imaging unit 13, and the imaging unit 13 is moved by the distance D along the optical axis of the reflected light. Since the original G is inverted once by the transport rollers 6 and 7 and the back side of the original G is read at the position R2 by the image pickup unit 13, there is no need to duplicate the transport path, and the transport time can be shortened, and Efficiency is improved.

[Second Embodiment] FIG. 5 is a configuration diagram of an image reading apparatus according to a second embodiment of the present invention. In the image reading device 30, a transparency variable member 32 is provided instead of the contact glass 12 of the image reading device 1 of the first embodiment, and a transparency control unit (a transparency control unit (L) for controlling the transparency of the transparency variable member 32 to low or high transparency. (Not shown). The other configuration is the same as that of the image reading apparatus 1, and the description thereof is omitted. Note that the length of the transparency changing member 32 is the same as or longer than the length of the document G at least in a direction orthogonal to the transport direction of the document G.

Next, the operation of the image reading apparatus 30 will be described with reference to FIGS. When reading both sides of the document, the operator operates the buttons on the operation panel 50 on the outer case 21 to instruct double-side reading, and sets the document G in the document insertion slot 3. Subsequently, the operator operates the operation panel 5
When the start of document reading is instructed by operating the button 0, the transparency control unit sets the transparency of the transparency variable member 32 low, and the illumination lamp control circuit 46 turns on the illumination lamp 9 (simultaneously turns off the illumination lamp 10). ), Transfer motor 5
1 drives and the original G is conveyed. At this time, the imaging unit 13 is set at the reference position P1.

As shown in FIG. 5, when the document G reaches the position R1, the illumination lamp 9 illuminates the surface of the document G, and the light reflected from the surface of the document G is transmitted via the mirror 14 to the CCD of the image pickup unit 13. Irradiation is performed on the sensor 16 and reading of the front surface image of the document G is started. Thereafter, when the rear end of the document G passes through the position R1, the reading of the front surface image of the document G ends. Thereby, a front surface image of the document G can be obtained. When the member disposed on the back side of the original G at the position R1 is a transparent member such as a contact glass, the light from the illumination lamp 9 causes the original G and the transparent member to pass through depending on the paper quality (thickness) of the original G. There is a risk that the transmitted image will have insufficient light intensity of the reflected light and the front image will be dark. However, in the second embodiment, since the transparency of the variable transparency member 32 is set low, the light from the illumination lamp 9 is sufficiently reflected by the original G and the variable transparency member 32,
It can be avoided that the front image becomes dark due to insufficient light intensity of the reflected light.

When the reading of the front surface image of the original G is completed, as shown in FIG.
Move to 2. On the other hand, the original G is transported by rollers 5, 6, 7
And once inverted. Document position detection sensor 1
When the position of the leading end of the document G is detected by 1, the transparency control unit sets the transparency of the transparency variable member 32 high, and the illumination lamp control circuit 46 turns off the illumination lamp 9 and turns on the illumination lamp 10.

Subsequently, when the document G reaches the position R2,
The back surface of the document G is illuminated by the illumination lamp 10, and the reflected light from the back surface of the document G is radiated to the CCD sensor 16 of the imaging unit 13 via the transparency changing member 32 and the mirror 14, so that the back surface image of the document G is read. Be started.
Thereafter, when the rear end of the document G passes the position R2, the reading of the back surface image of the document G ends. As a result, a backside image of the document G can be obtained. When the reading of both sides of the document G is completed, the document G is transported by the transport rollers 5 and discharged to the discharge tray 4. Then, the imaging unit 13 returns (moves) to the reference position P1.

As described above, when reading the image on the back surface, most of the reflected light passes through the transparency changing member 32 because the transparency of the transparency changing member 32 is high. Although a detailed description is omitted, the read back image is multiplied by the reciprocal of the maximum transmittance of the transparency variable member 32 to perform density correction, so that the degradation of the back image due to the transparency of the transparency variable member 32 is reduced. Prevention can prevent image quality from deteriorating.

As described above, in the image reading apparatus 30 according to the second embodiment, when the front surface of the document G is read at the position R1, the transparency of the transparency changing member 32 is set low, and when the back surface of the document G is read at the position R2. The transparency of the transparency variable member 32 is set high, and the transparency
, The transport time when reading both sides of a document can be reduced without deteriorating the image quality of the front and rear images and without increasing the apparatus cost. .

[Third Embodiment] FIG. 7 is a block diagram of an image reading apparatus according to a third embodiment of the present invention. In the image reading apparatus 40, the optical path lengths of the positions R1 and R2 are made the same by moving the imaging unit 13 along the optical axis of the reflected light by the distance D in the first and second embodiments. Instead, the reflected light is
The mirror 14 for guiding to the CD sensor 16 (photoelectric conversion means) is moved by a distance D along the optical axis of the reflected light.
The basic configuration and operation are the same as those of the first embodiment, and only different portions will be described in detail here.

As shown in FIG. 7, in the image reading device 40 of the third embodiment, the contact glass 12 of the first embodiment is used.
Instead of the position where the (or the variable transparency member 32 of the second embodiment) is disposed, the contact glass (or the variable transparency member) is disposed at a position indicated by reference numeral 42. The illumination lamp 10, the document position detection sensor 11, and the position R2
(Second reading position) is moved below the contact glass 42, and the transport rollers 5 in the vicinity are moved and arranged to the upstream side of the transport path along with these movements.

Although not shown, the position R1 (first
From the reading position) to the CCD sensor 16 and the optical path length of the reflected light from the position R2 (second reading position) to the CCD sensor 16
Mirror 14 so that the optical path length of the reflected light up to
Is moved along the optical axis of the reflected light. For example, a carriage mechanism used in a general copying machine can be used as the moving means.

The operation of the above configuration will be described with reference to FIGS. When reading the front side of the document G, the mirror 14 is stopped at the reference position P1 as shown in FIG. In this state, the reflected light of the light emitted from the illumination lamp 9 to the document G at the position R1 is transmitted through the mirror 14 to the CC.
The image is guided to the D sensor 16 and the image on the front surface of the document G is read.

Next, when reading the back side of the document G, the mirror 14 has been moved to the moving position P2 and stopped as shown in FIG. In this state, the reflected light of the light emitted from the illumination lamp 10 to the document G at the position R2 is reflected by the contact glass 42.
And the image is guided to the CCD sensor 16 via the mirror 14 and the image on the back surface of the original G is read.

Here, the reference position P1 and the movement position P2
Is a distance D from the contact glass 42 to the position R2.
Length equal to the distance to Therefore, the optical path length from the CCD sensor 16 to the position R1 and the CCD sensor 16
The optical path length from to the position R2 is the same.

As described above, in the image reading apparatus 40 according to the third embodiment, the surface of the original G is read at the position R1 by the imaging unit 13, and then the mirror 14 is moved by the distance D along the optical axis of the reflected light. The original G is inverted once by the conveying rollers 6 and 7, and then the position R is
Since the back side of the document G is read in step 2, it is not necessary to overlap the transport paths, so that the transport time can be reduced and the operation efficiency can be improved.

[0048]

As described above, in the image reading apparatus of the present invention (claim 1), the surface of the document passing through the first reading position is read by the photoelectric conversion means, and the document is read by the reversing portion of the document transport means. Is inverted once, and the second
When reading the back side of a document passing through the reading position, the moving unit determines the optical path length of the reflected light from the first reading position to the photoelectric conversion unit and the optical path of the reflected light from the second reading position to the photoelectric conversion unit. Since the photoelectric conversion means is moved along the optical axis of the reflected light so as to have the same length, the transport time when reading both sides of the document can be reduced without increasing the apparatus cost.

Further, the image reading apparatus of the present invention (Claim 2)
Then, the passage determination means determines whether or not the document has passed the first reading position. If the document has passed, the light source switching means turns off the first light source and turns on the second light source. And, when passing, the moving means moves the photoelectric conversion means along the optical axis of the reflected light,
Lighting switching of the light source and movement of the photoelectric conversion means can be performed at appropriate timing.

An image reading apparatus according to the present invention (claim 3)
Since the light from the light source does not pass through the original and the variable transparency member because the transparency of the variable transparency member is low when reading the surface of the original, it is possible to avoid darkening the surface image due to insufficient light intensity, Can be prevented from decreasing.

Further, the image reading apparatus of the present invention (Claim 4)
Since the image density correction of the back surface image is performed based on the maximum transmittance of the transparency variable member, the decrease in light intensity can be corrected, and the front image and the back image can be read with the same image quality.

Further, the image reading apparatus of the present invention (Claim 5)
Then, the front surface of the document passing through the first reading position is read by the photoelectric conversion means, and the document is read by the reversing unit of the document conveying means.
When the back surface of the document passing through the second reading position is read by the photoelectric conversion unit, the moving unit moves the optical path length of the reflected light from the first reading position to the photoelectric conversion unit and the second position.
The reflection mirror is moved along the optical axis of the reflected light so that the optical path length of the reflected light from the reading position to the photoelectric conversion means becomes the same, so that both sides of the document are read without increasing the apparatus cost. It is possible to reduce the time required for transportation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image reading device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram when the back side of a document is read by the image reading device of FIG. 1;

FIG. 3 is an explanatory diagram of a moving mechanism of the imaging unit.

FIG. 4 is a block diagram of the image reading apparatus of FIG. 1;

FIG. 5 is a configuration diagram of an image reading device according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a case where the back side of a document is read by the image reading device of FIG. 5;

FIG. 7 is a configuration diagram of an image reading apparatus according to Embodiment 3 of the present invention.

FIG. 8 is an explanatory diagram in the case where the back side of a document is read by the image reading device of FIG. 7;

FIG. 9 is an explanatory diagram showing a configuration of a conventional image reading apparatus (reading section of a digital copying machine having an ADF).

[Explanation of symbols]

 Reference Signs List 1, 30, 40 Image reading device 2 Transport path 3 Document insertion port 4 Eject tray 5, 6, 7 Transport roller 9, 10 Illumination lamp 11 Document position sensor 13 Imaging unit 14 Mirror 20 Image processing board G Document P1 Reference position P2 Move Position R1, R2 Reading position

Claims (5)

[Claims] 1. A document conveying means for conveying a document along a conveying path having a reversing section for reversing the front and back of the document, and a first position upstream of a position of the reversing section on the conveying path. A first light source that irradiates the document with light at the reading position, a second light source that irradiates the document with light at a second reading position that is located downstream with respect to the position of the reversing unit on the transport path, A photoelectric conversion unit that receives reflected light of light emitted from the first light source to the original and reflected light of light emitted from the second light source to the original, and converts the reflected light into an electrical signal; The optical axis of the reflected light is adjusted so that the optical path length of the reflected light from the reading position to the photoelectric conversion unit is the same as the optical path length of the reflected light from the second reading position to the photoelectric conversion unit. Moving means for moving along the Image reading apparatus for. 2. The image forming apparatus according to claim 1, further comprising: a passage determination unit configured to determine whether the document has passed the first reading position; and a first light source and a second light source based on a determination result of the passage determination unit.
Light source switching means for performing light source switching control of the light source, wherein the moving means moves the photoelectric conversion means along the optical axis of the reflected light based on the determination result of the passage determining means. The image reading device according to claim 1. 3. The image forming apparatus according to claim 2, wherein the width of the original is at least the same as the original reading width to be read by the photoelectric conversion means, and
And a transparency control means for controlling the transparency of the transparency control means, wherein the transparency control means controls the transparency of the transparency control means. 2. The method according to claim 1, wherein the control unit controls the transparency of the variable transparency member to a low state, and controls the transparency of the variable transparency member to a high state when the position of the document is the second reading position. 3. The image reading device according to 2. 4. The image processing apparatus according to claim 1, further comprising a density correction unit configured to perform image density correction on an image read at the second reading position based on a maximum transmittance of the transparency changing member. 4. The image reading device according to 3. 5. A document transport means for transporting a document along a transport path having a reversing section for reversing the front and back of the document, and a first position located upstream with respect to the position of the reversing section on the transport path. A first light source that irradiates the document with light at the reading position, a second light source that irradiates the document with light at a second reading position that is located downstream with respect to the position of the reversing unit on the transport path, A photoelectric conversion unit that receives reflected light of light emitted from the first light source to the document and reflected light of light emitted from the second light source to the document, and converts the reflected light into an electrical signal; A reflection mirror that guides reflected light of light emitted from the light source to the document and reflected light of light emitted from the second light source to the document to the photoelectric conversion unit; and from the first reading position to the photoelectric conversion unit. From the optical path length of the reflected light and the second reading position. Image reading apparatus characterized by comprising moving means and the optical path length of the reflected light to the photoelectric conversion means moves along the reflecting mirror to be identical to the optical axis of the reflected light.