JPH09116707A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of sensors to detect a position of a light source and a reflection body to the utmost and to make the reader small. SOLUTION: First and second moving frames 31, 34 provided with a light source 32 and 1st, 2nd, 3rd mirrors 33,35,36 are moved by driving a stepping motor 22. A position sensor 44 detects that the 1st and 2nd frames 31, 34 are at a home position. The 1st and 2nd moving frames 31, 34 make measurement based on the count of a drive step number of the step motor 22. Furthermore, white reference data being a reference of correcting the signal level in read image data are acquired by emitting a light from the light source 32 onto a white sheet 16 placed to an under side of a retainer 13.

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 reading an image on an object to be read in a state where the object to be read such as a book is placed on a support plate in a copying machine or a facsimile machine. is there.

[0002]

2. Description of the Related Art Generally, in this type of image reading apparatus, an object to be read such as a book is placed on a cover glass as a transparent support plate. In this state, the light source and the mirror as a reflector are moved along the cover glass by driving the motor. At this time, the object to be read is irradiated with light from a light source through a cover glass, and the reflected light is guided to a CCD (charge coupled device) type image sensor through an optical system such as a plurality of mirrors and lenses to be read. The image on the object is read.

In such an image reading apparatus, since the light source and the mirror are moved when the image is read, it is necessary to accurately grasp the moving positions of the light source and the mirror. Usually, the light source and the mirror are moved from a state of waiting at a specific standby position (origin position) to a predetermined reading end position via a reading start position, and then return to the standby position. Therefore, in order to know that the light source and the mirror are at least at three positions of the origin position, the reading start position and the reading end position, it is necessary to provide sensors for detecting the light source and the mirror corresponding to the respective positions. There is.

Further, the plurality of LEDs constituting the light source and the CCD of the image sensor have variations in the brightness and sensitivity of the element itself, and the brightness and sensitivity change due to aging and temperature change. As a result, the signal level value of each pixel data in the read image data for one line varies or changes due to the brightness and the sensitivity. Moreover, the distortion of the optical system such as the lens affects the signal level value of each pixel data in the read image data for one line as so-called shading distortion.

In order to compensate for such variations and changes in the signal level value in the read image data, in the above-mentioned image reading device, a white color is provided at a predetermined position of the device prior to reading the image on the object to be read. One part of the line is read, and the read data of the one line is used as white reference data. Then, a correction coefficient is calculated so that the signal level value of each pixel data in the white reference data becomes a preset white reference level value. When the image on the object to be read is read, the signal level value of each pixel data in the read image data is corrected based on the correction coefficient obtained from the white reference data. In this case, in the conventional device, the white portion for acquiring the white reference data is provided at a position outside the cover glass which is the image reading range.

[0006]

However, as described above, when a plurality of sensors for detecting the light source and the mirror are provided, there arises a problem that the structure becomes complicated and the cost of the apparatus increases. Also, if a white part for acquiring white reference data is provided at a position outside the cover glass, the light source and the mirror are moved to a position facing the white part outside the cover glass in order to read the white part. It is necessary to let For this reason, it is necessary to secure a large moving range of the light source and the mirror, which causes a problem of increasing the size of the device.

The present invention has been made by paying attention to the problems existing in such conventional techniques. The purpose thereof is to reduce the number of sensors for detecting the positions of the light source and the reflector as much as possible and to downsize the device.

[0008]

In order to achieve the above-mentioned object, in the invention according to claim 1, while moving the light source and the reflector, the object to be read placed on the transparent support plate is moved. In addition to irradiating light from a light source, the reflected light is guided to an image sensor via a reflector, and in an image reading device for reading an image on an object to be read, a step motor for moving the light source and the reflector, One sensor for detecting that the light source and the reflector are located at a specific origin position.

According to a second aspect of the invention, in the image reading apparatus according to the first aspect, the measuring means for measuring the moving amount of the light source and the reflector based on the counting of the driving step number of the step motor, and the step motor When the light source and the reflector are moved in one direction by driving, and the on / off state of the sensor is not switched even if the movement amount reaches a predetermined amount, an abnormality determining means for determining that the device is abnormal is provided. Is provided.

According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, a pressing plate for pressing an object to be read is provided on the transparent supporting plate, and the pressing surface of the pressing plate is provided. A white portion is provided, and correction means for correcting the signal level value in the read image data is provided with the data obtained by reading the white portion of the pressing surface by the image sensor as white reference data.

Therefore, the invention according to claims 1 to 3 has the following operations. In the invention according to claim 1, the light source and the reflector are moved by driving the step motor. Therefore, if one sensor detects that the light source and the reflector are at the specific origin position, the amount of movement of the light source and the reflector from the origin position can be accurately known based on the number of driving steps of the step motor. As a result, the moving positions of the light source and the reflector can be accurately grasped.

According to the second aspect of the invention, when the light source and the reflector are moved by driving the step motor, the moving amount of the light source and the reflector is measured by the measuring means based on the number of driving steps of the step motor. To be done. When the light source and the reflector are moved in one direction, the sensor is turned on / off even though the movement amount exceeds a predetermined amount.
If the off state is not switched, the abnormality determining means determines that the device has an abnormality. For example, when a light source and a reflector other than the origin position are moved in a direction closer to the sensor (direction closer to the origin position), the amount of movement is a predetermined amount (for example, from one moving end of the light source and the reflector to the other). If the sensor does not switch from OFF to ON even after reaching the maximum movement amount up to the movement end), it is determined that the sensor or the mechanism for moving the light source and the reflector is abnormal. Also, when the reflector at the origin position is moved in the direction away from the sensor (direction away from the origin position), even if the sensor does not switch from on to off even if the amount of movement reaches a predetermined amount, the same error occurs. It is determined that there is.

According to the third aspect of the present invention, the white reference data is acquired from the pressing surface of the pressing plate located at the position facing the support plate. That is, in a state where the light source and the reflector are moved to a position facing the support plate which is the image reading range,
The white reference data is obtained by reading the white portion of the pressing plate with the image sensor. Therefore, it is not necessary to move the light source and the reflector to a position outside the image reading range in order to obtain the white reference data.

[0014]

An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, a cover glass 12 as a transparent support plate on which an object to be read A such as a book is placed is attached to an upper opening of a device case 11. A pressing plate 13 for pressing the object A to be read placed on the cover glass 12 from above is rotatably attached to the upper surface of the device case 11. The pressing plate 13 has a substrate 14 and an elastic body 15 such as a sponge attached to the lower surface of the substrate 14.
A white sheet 16 is attached to the lower surface of the elastic body 15.

Inside the apparatus case 11, a pair of pulleys 1 is provided.
7, 18 are rotatably supported. Each pulley 17,
18 has first pulleys 17a and 18a and second pulleys 17b and 18b, respectively. First pulley 1
The diameter of 7a, 18a is twice the diameter of the second pulley 17b, 18b. The first belt 19 is looped between the first pulleys 17a and 18a, and the second pulleys 17b and 18a
A second belt 20 is hung between b.

A step motor 22 is mounted inside the apparatus case 11 via a mounting plate 21. The rotation of the step motor 22 is performed by a plurality of gears 23, 24, 2
It is transmitted to one pulley 18 via 5, 26, 27 and 28. Therefore, as the step motor 22 is driven, both belts 1 are driven through the gears 23 to 28 and the pulleys 17 and 18.
9, 20 orbit clockwise or counterclockwise. In each pulley 17, 18, the first pulley 17a, 18
Since the diameter of a is twice the diameter of the second pulleys 17b and 18b, the orbital speed of the first belt 19 is equal to that of the second belt 20.
It is twice the orbital speed of.

The first moving frame 31 is the device case 11
The belts 19 and 20 are arranged therein so as to be capable of reciprocating along the extending direction. The first moving frame 31 is the first
And is moved in the left-right direction in the drawing as the first belt 19 goes around. The light source 32 and the first mirror 33 as a reflector are attached to the first moving frame 31 and extend along a direction orthogonal to the paper surface.
The light source 32 irradiates the object A to be read placed on the cover glass 12 with light through the cover glass 12.
The first mirror 33 reflects the reflected light in the vertical direction, which is incident from the object to be read A, in the horizontal direction.

The second moving frame 34 is the device case 11
The belts 19 and 20 are arranged therein so as to be capable of reciprocating along the extending direction. The second moving frame 34 is the second
Of the second belt 20 and is moved in the left-right direction in the drawing as the second belt 20 goes around. Since the orbital speed of the second belt 20 is 1/2 times the orbital speed of the first belt 19,
When the first moving frame 31 is moved in one direction at the speed V1, the second moving frame 34 moves at 1 / th of the speed V1.
It is moved in the same direction at a speed V2 of 2. The second and third mirrors 35 and 36 as reflectors are attached to the second moving frame 34 and extend along the direction orthogonal to the paper surface. The second mirror 35 is the first mirror 33.
The reflected light in the horizontal direction that is incident from is reflected in the vertical direction. The third mirror 36 reflects the reflected light in the vertical direction, which is incident from the second mirror 35, in the horizontal direction.

Lens 41 and CCD image sensor 4
2 is fixedly disposed in the device case 11 via a fixing frame 43. The reflected light in the horizontal direction from the third mirror 36 passes through the lens 41 and the image sensor 42.
The image on the object to be read A is read by the image sensor 42 by being guided to.

Since the moving speed V1 of the first moving frame 31 is twice the moving speed V2 of the second moving frame 34,
Even if both moving frames 31 and 34 are moved, the object to be read A
The length of the optical path from the image sensor 42 to the image sensor 42 is always constant. Therefore, the focal position of the reflected light from the object A to be read is always constant with respect to the image sensor 42.

As shown in FIGS. 1 and 2, the position detection sensor 44, which is a limit switch, is provided on the left side in the figure of the apparatus case 11 and includes a contactor 45 that can contact the second moving frame 34. ing. Then, when the first and second moving frames 31 and 34 are moved to the standby position (origin position) P1 shown by the two-dot chain line in FIG.
The position detecting sensor 44 is turned “on” by the touching of the second moving frame 34.

In the present embodiment, the first and second moving frames 31 and 34 pass from the origin position P1 to a reading start position P2 shown by a solid line in FIG. 1 and a reading end position shown by a two-dot chain line in FIG. Moved to P3. Further, as shown by the solid line in FIG. 2, in the present embodiment, the first and second moving frames 31, 34 start reading within the image reading range between the reading start position P2 and the reading end position P3. A position slightly moved from the position P2 to the reading end position P3 side is set as a white reference data acquisition position P4 described later.

Next, the circuit configuration of the image reading apparatus will be described with reference to FIG. A CPU (Central Processing Unit) 51 stores an R for storing programs for controlling the operation of the entire device.
An OM (Read Only Memory) 52 and a RAM (Random Access Memory) 53 for temporarily storing various information are connected. CPU51, ROM52 and RAM53
Constitutes a measuring means, an abnormality judging means and a correcting means. The step motor 22 and the position detection sensor 44 are connected to the CPU 51 via a drive circuit 54. The drive circuit 54 is C
An excitation signal is generated based on a drive pulse having a predetermined frequency output from the PU 51 and given to the step motor 22. The step motor 22 is driven to rotate one step at a time by an excitation signal from the drive circuit 54.

The reading section 55 optically reads an image on the object A to be read placed on the cover glass 12, and includes the light source 32, the mirrors 33, 35 and 36, and the lens 4.
1 and the image sensor 42. The encoding circuit 56 encodes the image data read by the reading unit 55.

An NCU (network control unit) 57 controls a line connection with an external facsimile device F or a telephone line L connected to the image reading device.
The modem 58 modulates transmission data. Operation key group 5
Reference numeral 9 includes various keys such as a scanner communication key 60, a copy key 61, and a reading start key 62. CPU51
When the scanner communication key 60 is in the ON state, the scanner communication mode is set, and the image data on the object to be read A read by the reading unit 55 under the mode is transmitted to the partner machine via the telephone line L. On the other hand, the CPU 51 sets the copy mode when the copy key 61 is on,
The read image data is transmitted to the external facsimile device F and is copied and output by the same device. That is, the image reading apparatus of the present embodiment has a facsimile transmission function and does not have a function of printing out the read image data, but instead of transmitting the read image data to the external facsimile apparatus F for printing out. have. The selection of the scanner communication mode or the copy mode is performed alternatively. When both the scanner communication key 60 and the copy key 61 are both in the off state, the CPU 5
1 sets the standby mode (the telephone line L and the facsimile device F are directly connected).

The display section 63 is a liquid crystal display panel or LED.
And displays the current state of the image reading apparatus such as "scanner communication mode", "copy mode", "standby", and "device abnormality".

Next, the operation of the image reading apparatus performed under the control of the CPU 51 will be described with reference to the flow charts shown in FIGS. First, the operation of the image reading apparatus when the power is turned on will be described with reference to FIG. At this time, the pressing plate 13 is assumed to be closed as shown in FIG. When a power switch (not shown) provided in the image reading device is turned on, the CPU 51 determines whether the position detection sensor 44 is "on" (steps S1 and S2). When the position detection sensor 44 is not “on”, the CPU 51 determines that the first and second moving frames 31 and 34 are not located at the origin position P1 and operates the step motor 22 via the drive circuit 54. It is driven to move the first and second moving frames 31 and 34 in a direction approaching the origin position P1 (step S3).
At that time, the CPU 51 causes the first and second moving frames 3
It is determined whether or not 1, 34 have moved by the maximum movement amount (step S4). The maximum movement amount is the origin position P at which the first and second moving frames 31 and 34 are the moving ends.
This is the amount of movement required to move in the range from 1 to the reading end position P3. When the CPU 51 moves the first and second moving frames 31, 34, the step motor 22
The number of driving steps is counted, and the amount of movement of the first and second moving frames 31 and 34 is measured based on the count. Here, when the movement amount of the first and second moving frames 31 and 34 reaches the maximum movement amount without the position detection sensor 44 turning on, the CPU 51 causes the position detection sensor 44 to move.
Alternatively, it is determined that the mechanism for moving the first and second moving frames 31 and 34 is abnormal. And CP
U51 performs a predetermined error process, for example, displays a message such as "device abnormality" on the display unit 63, stops the operation of the step motor 22, and temporarily ends the process (step S5).

On the other hand, the first and second moving frames 31, 3
When the position detection sensor 44 is turned “on” before the movement amount of No. 4 reaches the maximum movement amount, the CPU 51 causes the first
It is determined that the second moving frames 31 and 34 have been normally moved to the origin position P1. Then, the CPU 51 rotates the step motor 22 in the opposite direction via the drive circuit 54, and the first and second moving frames 31 and 34 reach the white reference data acquisition position P4. The moving frames 31 and 34 are moved toward the white reference data acquisition position P4 (steps S6 and S7). CPU51
When it is determined that the first and second moving frames 31 and 34 have moved to the white reference data acquisition position P4 based on the count of the number of driving steps of the step motor 22, the position detection sensor 44 is turned off. It is determined whether or not (step S8). Here, if the position detection sensor 44 is not "OFF", the CPU 51 determines that the image reading device has an abnormality in the same manner as in step S5, performs a predetermined error process, and then executes the process. It ends once (step S9). That is, “device abnormality” is displayed on the display unit 63 and the operation of the step motor 22 is stopped.

When the position detection sensor 44 is "OFF", the CPU 51 determines that the first and second moving frames 31 and 34 have been normally moved to the white reference data acquisition position P4, and the white To obtain the reference data, the light source 3
2 is turned on to irradiate the sheet 16 of the pressing plate 13 with light (step S10). The reflected light from the white sheet 16 is guided to the image sensor 42 via the first, second and third mirrors 33, 35 and 36 and the lens 41,
Captured as white reference data. And the CPU 51
Calculates a correction coefficient such that the signal level value of the fetched white reference data becomes a preset white reference level value. (Step S11).

Next, the CPU 51 causes the step motor 22 to rotate in the opposite direction again, and the first and second moving frames 3
1, 34 are moved toward the origin position P1 (step S12). Then, the CPU 51 determines whether or not the position detection sensor 44 is turned "on" (step S1).
3). Here, when it is “on”, the CPU 51
Determines whether or not the amount of movement of the first and second moving frames 31, 34 has reached the maximum amount of movement based on the number of driving steps of the position detection sensor 44 (step S14).

Here, when the movement amount of the first and second moving frames 31 and 34 reaches the maximum movement amount before the position detection sensor 44 is turned "on", the CPU 51 performs the same as steps S5 and S9. Then, it is determined that the image reading device has an abnormality, a predetermined error process is performed, and then the process is temporarily terminated (step S15). On the other hand, the CPU 51
When the position detection sensor 44 is turned “on” before the moving amount of the first and second moving frames 31, 34 reaches the maximum moving amount, the first and second moving frames 31, 34 are set to the origin position P1. It is determined that the print job has been normally moved to the standby state, the state shifts to the standby state, the display section 63 displays “standby”, and the process ends (step S16).

Next, the object A to be read is placed on the cover glass 12 of the image reading apparatus in the standby state as described above,
The operation of reading the image on the read object A will be described with reference to the flowchart shown in FIG.

Scanner communication key 60 or copy key 61
With one of the modes set by the operation,
When the reading start key 62 of the operation key group 59 is turned on, the CPU 51 drives the step motor 22 to move the first and second moving frames 31 and 34 from the origin position P1 toward the reading start position P2. (Steps S21 and S22). Then, the CPU 51 determines whether or not the first and second moving frames 31, 34 have reached the reading start position P2 based on the count of the number of driving steps of the step motor 22 (step S23). The CPU 51 causes the first and second moving frames 31 and 34 to read the reading start position P2.
If it is determined that the position detection sensor 44 has reached "0", it is then determined whether or not the position detection sensor 44 is "off" (step S24).

When the CPU 51 determines that the position detection sensor 44 is not "OFF", the steps S5 and S are executed.
9. Similar to steps S15 and S15, it is determined that the image reading device has an abnormality, a predetermined error process is performed, and then the process ends (step S25). On the other hand, when it is determined that the position detection sensor 44 is “off”, the CPU 51 causes the first and second moving frames 31 and 34 to read the reading start position P2.
Then, the image reading on the object A to be read is started (step S26). That is, the object A on the cover glass 12 is irradiated with the light from the light source 32, and the first and second moving frames 31, 34 are moved by the image sensor 42 while moving toward the reading end position P3. The image is read. 1st, 2nd
When the moving frames 31 and 34 of No. 1 are moved to the reading end position P3, the CPU 51 ends the reading, and the first and second
The moving frames 31, 34 are returned to the origin position P1. The movement of the first and second moving frames 31, 34 to the reading end position P3 and the return from the reading end position P3 to the origin position P1 are also accurately performed by counting the number of driving steps of the step motor 22. Further, the signal level value of the read image data is corrected to an appropriate level value according to the correction coefficient based on the white reference data acquired in step S11. The corrected image data is sent to the telephone line L or the external facsimile device F according to the selected mode.

The image reading apparatus of this embodiment is configured as described above and further operates, and therefore has the following advantages. (1) The step motor 22 is used to move the first and second moving frames 31 and 34. For this reason,
If the one position detection sensor 44 detects that the first and second moving frames 31, 34 are at the origin position P1, the first and second moving frames 31, 34 are detected based on the number of driving steps of the step motor 22. The amount of movement of 34 from the origin position can be accurately known. Therefore, the moving positions of the first and second moving frames 31 and 34 can be accurately grasped only by providing one position detecting sensor 44. As a result, the structure of the image reading apparatus can be simplified and the manufacturing cost can be reduced.

(2) The white reference data is the cover glass 12
It is acquired by reading the white sheet 16 provided on the lower surface of the pressing plate 13 facing the. That is, in order to obtain the white reference data, the first and second moving frames 31,
It is not necessary to move 34 to a position outside the cover glass 12 which is the image reading range. Therefore, the moving ranges of the first and second moving frames 31 and 34 can be minimized, and the device can be downsized.

(3) In steps S5, S9, S15 and S25, when the CPU 51 determines that the image reading device has an abnormality, it stops driving the step motor 22. As a result, the first and second moving frames 31,
It is possible to prevent the problem that 34 is moved beyond the allowable movement range and damages the device. Further, by displaying “device abnormality” on the display unit 63, it is possible to surely inform the user that the image reading apparatus has an abnormality.

(4) Since the step motor 22 is used, the feed amount of the first and second moving frames 31 and 34 can be accurately controlled, and the feed speed can be easily variably controlled. Therefore, it is possible to easily deal with the case where the transmission time of each line in the image data is different, such as in facsimile communication, and the read image data can be transmitted in real time without storing it in the memory.

(5) When the power switch is turned on, an operation check is made as to whether or not the mechanical section is normal, and white reference data to be a reference for correcting the signal level value in the read image data is acquired. Therefore, the reading operation can be performed immediately when the document is read. Further, it is not necessary to specially provide a backup circuit for holding the storage of the white reference data when the power is off.

The present invention can be embodied with the following modifications. (1) The origin position P1 should be the same position as the reading start position P2. Thus, when the image data on the object A to be read is read, the movement of the first and second moving frames 31 and 34 may be immediately started from the origin position P1.

(2) The white reference data acquisition position P4 should be the same position as the reading start position P2. This also makes it possible to obtain the same effects as the above embodiment. (3) In the above embodiment, the white reference data is acquired only when the power switch is turned on by the user. However, when the power is continuously on for a predetermined time or more, the predetermined time has elapsed. After that, automatically acquire the white reference data by using the time when the device is in "standby". With this configuration, even when the power is always on, the white reference data is acquired every predetermined time, so that the signal level value in the read image data is reduced even if the light source 32 or the like deteriorates. Can be corrected more appropriately.

(4) When the CPU 51 determines that the device is abnormal, not only the "device abnormal" is displayed on the display unit 63, but also a voice such as "beep" is output. This allows the user to more easily and reliably know that there is an abnormality in the device.

(5) The white part of the sheet 16 is provided only in the part corresponding to the white reference data acquisition position P4. Also by this, the white reference data can be acquired in the same manner as in the above embodiment.

(6) The reading end position P3 can be arbitrarily changed and set by a key operation according to the size of the object A to be read. Also in this case, the plurality of reading end positions P3 can be surely grasped based on the count of the number of driving steps of the step motor 22.

(7) The position detecting sensor 44 should be a non-contact type sensor such as an optical sensor. The technical ideas that can be grasped from the above embodiment will be described below. (1) The image reading apparatus according to claim 3, wherein the white reference data is acquired when the power switch is turned on.

(2) The image reading apparatus according to claim 2, wherein the abnormality judging means stops the driving of the step motor when the abnormality is judged.

[0047]

As described above in detail, the present invention has the following excellent effects. According to the invention described in claim 1, since the step motor is used, only one sensor for detecting the positions of the light source and the reflector is required, and the complexity and cost of the apparatus can be suppressed. It is possible.

According to the second aspect of the invention, when there is an abnormality in a device such as a sensor, it can be recognized. Therefore, it is possible to prevent the problem that the device is destroyed due to the movement of the light source and the reflector beyond the allowable movement range.

According to the third aspect of the invention, the moving ranges of the light source and the reflector can be made as small as possible.
The device can be downsized.

[Brief description of the drawings]

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

FIG. 2 is a partially enlarged cross-sectional view of the image reading device.

FIG. 3 is a block diagram of the image reading apparatus.

FIG. 4 is a flowchart showing an operation at power-on.

FIG. 5 is a flowchart showing an operation at the time of reading an image.

[Explanation of symbols]

12 ... Cover glass as transparent support plate, 13 ... Press plate, 22 ... Step motor, 31 ... First moving frame, 32 ... Light source, 33 ... First mirror as reflector,
34 ... 2nd moving frame, 35 ... 2nd as a reflector
Mirror, 36 ... third mirror as a reflector, 41 ...
Lens, 42 ... Image sensor, 44 ... Position detection sensor, 45 ... Contact, 51 ... CPU that constitutes measuring means, abnormality judging means and correcting means, 52 ... ROM that constitutes measuring means, abnormality judging means and correcting means, 53 ... Measuring means,
RAM constituting the abnormality determining means and the correcting means, 54 ... Driving circuit, A ... Object to be read, P1 ... Origin position, P2 ... Reading start position, P3 ... Reading end position, P4 ... White reference data acquisition position.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04N 1/00 106 H04N 1/00 106C 1/401 1/40 101A

Claims (3)

[Claims] 1. While moving the light source and the reflector, the object to be read placed on the transparent supporting plate is irradiated with light from the light source, and the reflected light is guided to the image sensor through the reflector. In the image reading device for reading the image on the object to be read, a step motor for moving the light source and the reflector and one sensor for detecting that the light source and the reflector are at a specific origin position are provided. Image reading device. 2. A measuring means for measuring the amount of movement of the light source and the reflector based on counting the number of driving steps of the step motor, and the amount of movement when the light source and the reflector are moved in one direction by driving the step motor. The image reading apparatus according to claim 1, further comprising: an abnormality determining unit that determines that the apparatus has an abnormality when the on / off state of the sensor does not switch even when a predetermined amount is reached. 3. A pressing plate for pressing an object to be read on a transparent support plate is provided, a white portion is provided on a pressing surface of the pressing plate, and the white portion of the pressing surface is read by an image sensor. The image reading apparatus according to claim 1, further comprising a correction unit that corrects a signal level value in the read image data by using the data as white reference data.