JP2011097348A - Lighting device and image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technologies to cancel or reduce temperature fluctuations between light source arrays while saving cost. <P>SOLUTION: Resistance elements 103 and 104 are serially connected to LED series circuits of temperature adjustment modules 107 and 108 respectively, and the light emitting state of light emitters 101 and 102 is indirectly detected through both-end voltages V<SB>R1</SB>and V<SB>R2</SB>of the resistance elements 103 and 104. A table storing a peltier current prespecified for every value of the both-end voltages V<SB>R1</SB>and V<SB>R2</SB>is prepared to control an amount of light emission of the light emitters 101 and 102 to be a specified value. When a current detector 113 detects both-end voltages V<SB>R1</SB>and V<SB>R2</SB>of the resistance elements 103 and 104, a peltier controller 115 reads a peltier current I (control value) corresponding to the detected voltages V<SB>R1</SB>and V<SB>R2</SB>from a table storage part 114, and supplies the peltier current I to the temperature adjustment modules 107 and 108. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention belongs to the technical field of illumination devices that irradiate light on a document of an image reading device such as a scanner.

  Conventionally, as described in, for example, Patent Document 1 below, in a lighting device having a light source array including a plurality of LED chips, a technique for cooling the light source array with a Peltier module is known. Patent Document 1 below discloses a technique for cooling the light source array by detecting the temperature of the LED chip using a thermistor and adjusting the amount of current to the Peltier module according to the detected temperature. .

JP 2004-342557 A

  A case is assumed in which a plurality of the light source arrays are mounted in order to increase the light quantity of the illumination device, and the illumination device is used as a scanner light source of the image reading device. In this case, if a temperature variation occurs between the light source arrays, the light quantity distribution of the light sources becomes non-uniform, thereby causing a problem that the image of the original cannot be read properly. It is necessary to suppress the occurrence of variations.

  Here, the structure which installs the thermistor employ | adopted by the said patent document 1 for every light source array, and controls operation | movement of each Peltier module based on the temperature detected by each thermistor can be considered.

  However, mounting a plurality of thermistors results in an increase in the cost of the lighting device. In addition, the thermistor has a problem that the characteristics vary greatly from element to element and accurate control cannot be performed.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique capable of eliminating or reducing temperature variations between light source arrays while suppressing an increase in cost. .

  The invention according to claim 1 includes a plurality of light emitting units, a plurality of thermoelectric elements for cooling the plurality of light emitting units, and a current detection unit for detecting current flowing in each of the light emitting units, A storage unit for storing in advance a correspondence relationship between a current that can be detected by the current detection unit and a current to be supplied to the thermoelectric element for causing each of the light emission units to emit light with a predetermined amount of light; and the current detection unit When the current flowing through each light emitting unit is detected by the control unit, the current to be supplied to the thermoelectric element corresponding to the current is read from the storage unit, and the read current is controlled to be supplied to the thermoelectric element. It is an illuminating device provided with the thermoelectric element control part to perform.

  According to the present invention, when the current flowing through each of the light emitting units is detected by the current detection unit, the current to be supplied to the thermoelectric element corresponding to the detected current by the thermoelectric element control unit is the light emission. The current is read from the storage unit as a current for causing the unit to emit light with a predetermined light amount, and the read current is supplied to the thermoelectric element.

  In this way, the light emitting state of the light emitting unit is indirectly detected by the current flowing through the light emitting unit, and the current detecting unit detects the light emitting unit to emit light with a predetermined amount of light. Current that should be supplied to the thermoelectric element is set in advance, and when a current flowing through each light emitting unit is detected, a current corresponding to the detected current is supplied to the thermoelectric element. Compared to a configuration in which the temperature of the part is detected by a thermistor, an increase in cost can be suppressed because the thermistor is unnecessary.

  In addition, a current that can be detected by the current detection unit and a current to be supplied to the thermoelectric element for causing the light emission unit to emit light with a predetermined light amount are set in advance for each combination of the light emission unit and the thermoelectric element. When the current flowing through each light emitting unit is detected, the current corresponding to the detected current is supplied to the thermoelectric element corresponding to each light emitting unit, so that the temperature variation of each light emitting unit can be reduced. it can.

  2. The lighting device according to claim 1, wherein the light emitting unit has a characteristic that the amount of light emission increases as the current flowing through the light emitting unit increases, and the current that flows through the light source as the temperature of the light emitting unit increases. When the element has a characteristic of decreasing, the current to be supplied to the thermoelectric element as the current that can be detected by the current detection unit increases in the storage unit as in the invention of claim 2. The correspondence relationship between the current that can be detected by the current detection unit and the current that should be supplied to the thermoelectric element may be stored in advance so that the current becomes smaller.

  According to a third aspect of the present invention, in the illuminating device according to the second aspect, the correspondence relationship is set for each combination of a corresponding light emitting section and a thermoelectric element.

  According to this invention, since the correspondence relationship between the current that can be detected by the current detection unit and the current to be supplied to the thermoelectric element is set for each combination of the corresponding light emitting unit and thermoelectric element, each light emitting unit In addition, variations in characteristics among individual thermoelectric elements can be absorbed.

  As a specific configuration of the current detection unit, for example, as in the invention described in claim 4, the current detection unit includes a plurality of resistance elements connected in series to each of the light emitting units, and an output signal of each of the resistance elements is It is assumed that each of the currents flowing through the light emitting portion is detected based on the voltage across the resistance element shown. According to this configuration, the current detection unit can be configured at low cost.

  Each of the light emitting units is assumed to have a plurality of LEDs connected in series as in the invention described in claim 5.

  Further, as the thermoelectric element, a form of a Peltier element is assumed as an example as in the invention described in claim 6.

  According to a seventh aspect of the present invention, the illuminating device according to any one of the first to sixth aspects of the present invention and the illumination light output from the illuminating device are applied to the document, and the reflected light is received to receive the document. An image reading apparatus includes an image reading unit that reads an image.

  According to this invention, it is possible to eliminate or reduce the temperature variation of each light emitting unit, so it is possible to eliminate or reduce the positional variation of the light emission amount of the unit composed of the plurality of light emitting units. As a result, the image to be read can be read more accurately.

  ADVANTAGE OF THE INVENTION According to this invention, the variation in the temperature between light emission parts can be eliminated or reduced, suppressing a cost increase. This can eliminate or reduce variations in the amount of light between the light emitting elements.

1 is a diagram illustrating a configuration of a first embodiment of an image forming apparatus. It is a block diagram which shows the electric constitution of the illuminating device with which a scanner part is provided, and the control part which controls this illuminating device. It is a figure which shows the structure of a temperature control module. It is a figure which shows the table previously memorize | stored in the table memory | storage part. It is a flowchart which shows operation control of the temperature control module by a control part.

  An embodiment of an image forming apparatus having an illumination apparatus according to the present invention and an image reading apparatus including the illumination apparatus will be described. FIG. 1 is a diagram illustrating a configuration of a first embodiment of an image forming apparatus.

  An image forming apparatus 1 shown in FIG. 1 includes a main body unit 2, a stack tray 3 disposed on the left side of the main body unit 2, a document reading unit 4 disposed on the top of the main body unit 2, and a document reading unit. 4 and a document feeding section 5 disposed above 4.

  The document reading unit 4 includes a scanner unit 6 including a CCD (Charge Coupled Device) sensor and an illumination device 100 described below, a document table 7 made of a transparent member such as glass, and a document reading slit 8. The scanner unit 6 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 7, the scanner unit 6 is moved along the document surface at a position facing the document table 7, and reads the document image. Image data acquired while scanning is output to an unillustrated image processing unit.

  When reading the document fed by the document feeding unit 5, the document is moved to a position facing the document reading slit 8, and is synchronized with the document feeding operation by the document feeding unit 5 via the document reading slit 8. The image of the original is acquired and the image data is output to the image processing unit.

  The document feeder 5 includes a document placement unit 9 for placing a document, a document discharge unit 10 for discharging a document whose image has been read, and a document placed on the document placement unit 9. A document transport mechanism 11 including a feed roller (not shown), a transport roller (not shown), and the like for feeding the paper one by one to a position facing the document reading slit 8 and discharging it to the document discharge section 10 is provided. The document transport mechanism 11 is further provided with a sheet reversing mechanism (not shown) that reverses the front and back of the document and transports it again to a position facing the document reading slit 8, and scans the images on both sides of the document via the document reading slit 8. The unit 6 can be used for reading.

  The document feeding unit 5 is provided so as to be rotatable with respect to the document reading unit 4 so that the front side thereof can move upward. By moving the front side of the document feeder 5 upward to open the upper surface of the document table 7, the operator can place a read document, for example, a book in a spread state, on the upper surface of the document table 7. It is like that.

  The main body 2 has been fed from a plurality of paper feed cassettes 12, a paper feed roller 13 for feeding recording sheets from the paper feed cassette 12 one by one to a later-described image forming unit 14, and a paper feed cassette 12. And an image forming unit 14 that forms an image on recording paper.

  The image forming unit 14 outputs a laser or the like based on the image data acquired by the scanner unit 6 or the like to expose the photoconductive drum 15, and an electrostatic latent image formed on the surface of the photoconductive drum 15. A developing unit 17 that visualizes an image to form an image, a transfer unit 18 that transfers an image formed on the photosensitive drum 15 to a recording paper, and a heating unit that heats the recording paper on which the image is transferred. The image forming apparatus includes a fixing unit 19 that fixes the recording paper and a pair of conveyance rollers 20 and 21 that are provided on a paper conveyance path in the image forming unit 14 and convey the recording paper to the stack tray 3 or the discharge tray 22.

  When forming images on both sides of the recording paper, the image forming unit 14 forms an image on one side of the recording paper, and then the recording paper is nipped by the pair of conveying rollers 20 on the discharge tray 22 side. . In this state, the conveyance roller pair 20 is reversed to switch back the recording paper, and the recording paper is sent to the paper conveyance path L and is conveyed again to the upstream area of the image forming unit 14. After the image is formed on the surface, the recording paper is discharged to the stack tray 3 or the discharge tray 22.

  An operation unit 23 is provided on the front portion of the image forming apparatus 1. The operation unit 23 displays a start key 24 for a user to input a print execution instruction, a numeric keypad 25 for inputting the number of copies to be printed, operation guide information for various copying operations, and the like. A display unit 26 including a liquid crystal display having a touch panel function, a reset key 27 for resetting the setting contents set on the display unit 26, and a stop key 28 for stopping a printing (image forming) operation being executed. And a function switching key 29 for switching between a copy function, a printer function, a scanner function, and a facsimile function.

  FIG. 2 is a block diagram showing an electrical configuration of the illumination device 100 provided in the scanner unit 6 and the control unit 106 that controls the illumination device 100. In addition, the same number is attached | subjected about the structure same as the structure shown in FIG. 1, and the description is abbreviate | omitted.

  As shown in FIG. 2, the lighting device 100 includes a plurality (two in this embodiment) of light emitting units 101 and 102 each including a plurality of LEDs (Light Emitting Diodes) 101 a and 102 a as light emitting elements connected in series. Have Hereinafter, a series circuit of a plurality of LEDs in each of the light emitting units 101 and 102 is referred to as an LED series circuit.

  The lighting device 100 includes a plurality of resistance elements 103 and 104 connected in series to the LED series circuits of the light emitting units 101 and 102, an inverter 105 connected to each LED series circuit, and a control unit 106 described later. And have.

  The inverter 105 receives a control signal (command signal) from the control unit 106, generates DC power (DC current) having a predetermined voltage based on the power supplied from the power source Vp, and each light emitting unit 101, 102. To supply.

  The light emitting units 101 and 102 emit light by receiving the supply of the DC power (DC current) from the inverter 105. When the voltage applied to the light emitting units 101 and 102 is equal to or higher than a predetermined voltage, the light emitting units 101 and 102 have a characteristic that the light emission amount increases as the current flowing through the light emitting units 101 and 102 increases (hereinafter referred to as characteristic (1) ))). In addition, the light emitting units 101 and 102 have a characteristic that the current flowing through the light emitting units 101 and 102 decreases as the temperature of the light emitting units 101 and 102 increases (hereinafter referred to as characteristic (2)).

The resistance elements 103 and 104 are connected between the LED series circuit and the ground. Of the two terminals of the resistance elements 103 and 104, the terminal connected to the LED series circuit is connected to a certain input terminal of the control unit 106, and the control unit 106 is connected to both ends of the resistance elements 103 and 104. Voltages between the terminals (voltages at both ends) V _R1 and V _R2 are taken in as voltage signals.

  Temperature control modules 107 and 108 as thermoelectric elements are attached to the LEDs 101a and 102a of the light emitting units 101 and 102, respectively. The temperature control modules 107 and 108 in the present embodiment have substantially the same configuration as each other. As shown in FIG. 3, the first and second substrates 109 and 110, the P-type semiconductor 111, and the N-type semiconductor 112 are used. It is a Peltier module configured with.

  As shown in FIG. 3, electrodes a and b are provided on the P-type semiconductor 111 and the N-type semiconductor 112, respectively, and the temperature control modules 107 and 108 are provided on the P-type semiconductor 111 and the N-type semiconductor 112, respectively. By passing a current (hereinafter referred to as a Peltier current) from a to the electrode b, one substrate functions as a heat dissipation plate and the other substrate functions as a heat absorption plate.

  The temperature control modules 107 and 108 are supplied with a current different from the supply current to the light emitting units 101 and 102. The magnitude of the current (Peltier current) is controlled by a control unit 106 (described later). It is controlled by the Peltier control unit 115).

  The LEDs 101a and 102a of the light emitting units 101 and 102 are mounted on a substrate that acts as a heat absorbing plate, whereby the temperature adjustment module 107 causes the light emitting unit 101 and the temperature adjustment module 108 to Each of the light emitting units 102 can be cooled. FIG. 2 shows a state in which the LEDs 101a and 102a of the light emitting units 101 and 102 are mounted on the substrate that acts as the heat absorbing plate of the temperature control modules 107 and 108.

  Returning to FIG. 2, the control unit 106 reads out a RAM (Random Access Memory) having a function of temporarily storing data and a function as a work area, a ROM storing a program in advance, and the program from the ROM. The CPU, the RAM, and the ROM are configured to exchange data via a data bus. The CPU executes processing corresponding to the contents of the program by appropriately executing the program stored in the ROM.

  The control unit 106 functions as a current detection unit 113, a table storage unit 114, and a Peltier control unit 115 by executing a control program stored in a ROM, for example.

The current detection unit 113 detects currents flowing through the resistance elements 103 and 104, that is, currents I _X and I _Y flowing through the light emitting units 101 and 102, based on voltage signals from the resistance elements 103 and 104. . That is, assuming that the resistance values of the resistance elements 103 and 104 are R1 and R2, information indicating the resistance values R1 and R2 is stored in advance by the current detection unit 113, and the current detection unit 113 stores the voltage of the resistance element 103. When the signal is captured, V _R1 / R1 obtained by dividing the voltage (voltage at both ends) V _R1 indicated by the voltage signal by the resistance value R1 of the resistance element 103 is detected as a current I _X flowing through the light emitting unit 101. Similarly, when the current detection unit 113 takes in the voltage signal from the resistance element 104, V _R2 / R2 obtained by dividing the voltage (both-end voltage) V _R2 indicated by the voltage signal by the resistance value R2 of the resistance element 104 is obtained. , And detected as a current I _Y flowing through the light emitting unit 102.

As shown in FIG. 4, the table storage unit 114 includes currents I _X and I _Y flowing through the light emitting units 101 and 102 and the temperature control modules 107 and 108 for causing the light emitting units 101 and 102 to emit light with a predetermined light emission amount. those stored in advance a table indicating the correspondence relation between the current I _s, I _t to be supplied to.

In the table shown in FIG. 4A, for example, when the current I _X flowing through the light emitting unit 101 detected by the current detection unit 113 is the current I _X1 , the current (control value) to be supplied to the temperature adjustment module 107. current _{I s1} is set as I _s. Also, the table shown in FIG. 4 (b), when the current _{I Y} flowing in the light emitting unit 102 detected by the current detecting section 113 of the current _{I Y1} is as a current _{I t} to be supplied to the temperature regulator module 108 A current value _It1 is set.

Current _I X flowing in such a light-emitting unit 101, _{I Y} and the Peltier current _I s, the relationship between the _{I t,} the characteristics of the light emitting portion 101, 102 (1), is set based on (2) ing.

  That is, when the temperature of the light emitting units 101 and 102 increases, the current flowing through the light emitting units 101 and 102 decreases due to the characteristic (2) of the light emitting units 101 and 102, and when the current flowing through the light emitting units 101 and 102 decreases. Since the light emission amount of the light emitting units 101 and 102 is reduced by the characteristic (1), in order to cause the light emitting units 101 and 102 to emit light with a constant light emission amount, it is necessary to suppress the temperature rise of the light emitting units 101 and 102. There is.

On the other hand, in the lighting device 100 according to the present embodiment, the current flowing through the light emitting units 101 and 102 is the same as the current flowing through the resistance elements 103 and 104. Therefore, when the currents I _X and I _Y flowing through the light emitting units 101 and 102 are reduced and the light emission amount of the light emitting units 101 and 102 is reduced, the current flowing through the resistance elements 103 and 104 is also reduced. Both-end voltages V _R1 and V _R2 are reduced.

In addition, when the current flowing through the light emitting units 101 and 102 increases and the light emission amount of the light emitting units 101 and 102 increases, the current flowing through the resistance elements 103 and 104 also increases, and the voltage V _R1 between both ends of the resistance elements 103 and 104 increases. _VR2 increases. Thus, there is a correlation between the light emission amounts of the light emitting units 101 and 102 and the currents I _X and I _Y flowing through the light emitting units 101 and 102, that is, the both-end voltages V _R1 and V _{R2 of the} resistance elements 103 and 104.

In the present embodiment, using the correlation between the light emission amounts of the light emitting units 101 and 102 and the currents I _X and I _Y flowing through the light emitting units 101 and 102, the light emitting states of the light emitting units 101 and 102 are changed. indirectly be detected by the current _I X, _{I Y} flowing in the current _I X flowing to the light emitting unit 101, _{I Y} is reduced (the light emission amount of the light emitting portion 101 is small), the light emitting portion Since the temperatures of the light sources 101 and 102 are high, by increasing the Peltier current I and cooling the light emitting units 101 and 102, the currents I _X and I _Y flowing through the light emitting units 101 and 102 are increased, and light emission occurs. The amount of light emitted from the units 101 and 102 is increased.

The increase amount of the Peltier current I is an amount corresponding to an insufficient light emission amount with respect to a predetermined light emission amount of the light emitting units 101 and 102, and is obtained in advance. The table is set based on the increase amount of the Peltier current I and the currents I _X and I _Y flowing through the light emitting units 101 and 102. Then, by setting this table in advance for each of the temperature control modules 107 and 108, variation in characteristics between the light emitting units 101 and 102 (individual difference) and variation in cooling characteristics between the temperature control units 107 and 108 ( Individual differences) are absorbed.

The Peltier control unit 115 controls the operation of the temperature adjustment modules 107 and 108, and the current flowing through the resistance elements 103 and 104 (current flowing through the light emitting units 101 and 102) I _X by the current detection unit 113. , I _Y is detected, the Peltier current I (control value) corresponding to the currents I _X , I _Y is read from the table storage unit 114, and the read Peltier current I is sent to the temperature control modules 107, 108. Control to supply.

For example, when the current flowing through the resistance element 103 detected by the current detection unit 113 (current flowing through the light emitting unit 101) I _X is the current I _X1 , the Peltier control unit 115 supplies a current value I to the temperature adjustment module 107. _s1 is supplied, and when the current flowing through the resistance element 104 (current flowing through the light emitting unit 102) I _Y detected by the current detection unit 113 is the current I _Y1 , the current is supplied to the temperature adjustment module 108. Supply a current of value _It1 . The Peltier control unit is an example of a thermoelectric element control unit.

  FIG. 5 is a flowchart showing operation control of the temperature adjustment modules 107 and 108 by the control unit 100.

As shown in FIG. 5, the current detection unit 113 receives currents flowing through the resistance elements 103 and 104 (currents flowing through the light emitting units 101 and 102) I _X and I based on voltage signals from the resistance elements 103 and 104. Upon detection of the _Y (YES in step # 1), reads from the detected current _{I X} to supply current corresponding (the temperature adjustment module 107 to supply current) _{I s} the table storage unit 114, the detected current _{I Y} corresponding supply current read out (the temperature regulating current supplied to the module 108) _{I t} from the table storage unit 114 (step # 2).

Then, the Peltier controller 115 supplies the supply current I _s read in step ♯2 the temperature control module 107 supplies a supply current I _t read in step ♯2 the temperature control module 108 (step ♯3 ).

As described above, the resistance elements 103 and 104 are connected in series to the LED series circuits of the temperature control modules 107 and 108, respectively, and the light emission state of the light emitting units 101 and 102 is changed to the currents flowing through the resistance elements 103 and 104 (the above-mentioned The currents flowing through the light emitting units 101 and 102) are indirectly detected by I _X and I _Y , and the current supplied to the temperature control modules 107 and 108 for setting the light emission amount of the light emitting units 101 and 102 to a predetermined value is determined by resistance. A preset table is prepared for each value of currents flowing through the elements 103 and 104 (currents flowing through the light emitting units 101 and 102) I _X and I _Y , and currents flowing through the resistance elements 103 and 104 (the light emitting units 101) are prepared. , 102 flows _current) I X, when _{I Y} is detected, said current _I X, the current supplied to the temperature control module 107 corresponding to the _{I Y} Since the supply current is supplied to the temperature control modules 107 and 108 by reading from the table, it is not necessary to mount a thermistor on each of the temperature control modules 107 and 108, thereby suppressing an increase in cost. Can do.

In addition, the correspondence between the currents I _X and I _Y that can be detected by the current detection unit 113 and the current supplied to the temperature control modules 107 and 108 for causing the light emitting units 101 and 102 to emit light with a predetermined light amount. Since the relationship is set in advance for each combination of the light emitting units 101 and 102 and the temperature adjusting modules 107 and 108, the light emitting characteristics vary between the light emitting unit 101 and the light emitting unit 102, or the temperature adjusting module 107 and the temperature adjusting module Even if there is a variation in the cooling characteristics between the modules 108, the variation can be absorbed and the variation in the temperatures of the light emitting units 101 and 102 can be eliminated or reduced.

  And since the variation in the temperature of each light emission part 101,102 can be eliminated or reduced, the positional variation can be eliminated or reduced with respect to the light emission amount (emission intensity) of the illumination device 100. As a result, the image to be read can be read more accurately.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 4 Original reading part 6 Scanner part 100 Illuminating device 101a, 102a LED
101, 102 Light emitting unit 103, 104 Resistance element 106 Control unit 107, 108 Temperature adjustment module 113 Current detection unit 114 Table storage unit 115 Peltier control unit

Claims (7)

A plurality of light emitting units;
A plurality of thermoelectric elements for cooling each of the plurality of light emitting units;
A current detection unit for detecting the current flowing through each of the light emitting units, and
A storage unit for preliminarily storing a correspondence relationship between a current that can be detected by the current detection unit and a current to be supplied to the thermoelectric element in order to cause each of the light emission units to emit light with a predetermined light amount;
When the current flowing through each light emitting unit is detected by the current detecting unit, the current to be supplied to the thermoelectric element corresponding to the current is read from the storage unit, and the read current is supplied to the thermoelectric element. An illuminating device comprising: a thermoelectric element control unit that performs control. The light emitting unit is an element having a characteristic that the amount of light emission increases as the current flowing through itself increases, and the characteristic that the current flowing through itself decreases as the temperature increases.
The storage unit includes a current that can be detected by the current detection unit and a current that should be supplied to the thermoelectric element so that the current to be supplied to the thermoelectric element decreases as the current that can be detected by the current detection unit increases. The illuminating device according to claim 1, wherein the correspondence relationship is stored in advance.   The lighting device according to claim 2, wherein the correspondence relationship is set for each combination of a corresponding light emitting unit and a thermoelectric element.   The current detection unit includes a plurality of resistance elements connected in series to each of the light emitting units, and based on a voltage across the resistance element indicated by an output signal of each resistance element, a current flowing through the light emitting unit. The lighting device according to claim 1, wherein each of the lighting devices is detected.   5. The lighting device according to claim 1, wherein each of the light emitting units includes a plurality of LEDs connected in series.   The lighting device according to claim 1, wherein the thermoelectric element is a Peltier element. The illumination device according to any one of claims 1 to 6,
An image reading apparatus comprising: an image reading unit that reads an image of the original by irradiating the original with illumination light output from the illumination device and receiving the reflected light.

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