JP2009177505A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader capable of obtaining a normal read image even if a driving circuit of a lighting light source gets out of order, and a control method and program thereof. <P>SOLUTION: LED blocks 101a and 101b are connected to driving circuits 104a and 104b through selector switches 102a and 102b, and 103a and 103b, respectively. The switches 102a and 102b, and 103a and 103b are operative to connect the LED block 101a to the driving circuit 104b which is operating normally. Further, the LED block 101b is connected to the driving circuit 104a which is getting out of order. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus having an illumination light source in which a plurality of point light sources such as LEDs are arranged.

  Conventionally, as a light source for illuminating a document used in an image reading apparatus, a light source typified by a Xe fluorescent tube filled with Xe (xenon) gas has been used in many cases. However, since fluorescent tubes such as Xe fluorescent tubes are lit and driven by high-frequency AC driving, it is necessary to secure a space for placing an inverter that converts a DC voltage into an AC voltage in the image reading apparatus. In addition, since the luminous efficiency of the fluorescent tube is poor, a large amount of heat is generated from the inverter and the fluorescent tube, and a countermeasure against heat is required and appropriate power is required. Furthermore, the life of the fluorescent tube is relatively short, and the fluorescent tube viewed from the product is positioned as a replacement part.

  Therefore, due to recent technological innovations, LEDs having a light emission amount suitable for use as an image reading system have appeared, and it has become possible to realize an image reading apparatus having an illumination light source in which a plurality of LEDs are arranged (for example, , See Patent Document 1). For example, as shown in FIG. 13, an example in which 48 LEDs 801 are linearly arranged on a substrate 800 and are turned on to form an illumination light source is common.

In this case, all 48 LEDs 801 may be connected in series to a constant current circuit, but if the forward voltage of one LED is 3.3 V, a voltage of 3.3 × 48 = 158.4 V or more is applied. Needed and not realistic. Therefore, as shown in FIG. 14, the 48 LEDs 801 are divided into 6 LED blocks 901, and a drive circuit 902 for lighting the LED 801 of the LED block 901 is connected to each LED block 901. The drive circuit 902 includes a constant current circuit and supplies a desired current to the block 901. For example, when the forward voltage per LED 801 is 3.3V, the drive circuit 902 applies a voltage of 3.3 × 6 = 19.8V or more.
JP 2002-247296 A

  However, in the conventional image reading apparatus, when the drive circuit 902 fails, the LED 801 of the LED block 901 cannot be turned on, and therefore the LED block 901 cannot be used as an illumination light source. Therefore, if even one drive circuit 902 fails, a normal read image cannot be obtained until the failed part is repaired or replaced.

  An object of the present invention is to provide an image reading apparatus capable of obtaining a normal read image even if a failure occurs in a driving circuit of an illumination light source.

  In order to achieve the above object, an image reading apparatus according to claim 1 has a plurality of blocks arranged linearly in the main scanning direction, and illumination means for illuminating the document while moving in the sub scanning direction. An image reading apparatus comprising a plurality of lighting means connected to the plurality of blocks and lighting the connected blocks, and a reading means for reading an image of the original from the original illuminated by the illumination means, A detecting means for detecting a malfunctioning lighting means among the plurality of lighting means; and a switching means for replacing the detected malfunctioning lighting means with a malfunctioning lighting means to connect to a block. It is characterized by.

  According to the present invention, since the failed lighting means is replaced with the non-failed lighting means and connected to the block, a normal read image can be obtained even if a failure occurs in the driving circuit of the illumination light source. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a cross-sectional view showing an internal configuration of an image copying apparatus equipped with an image reading apparatus according to a first embodiment of the present invention.

  In FIG. 1, an image copying apparatus 1 is an electrophotographic system, and includes an image reading apparatus 2 and a printer 3. The image reading device 2 reads an image of a document and acquires image information. The printer 3 forms an image on the transfer material P based on the image information acquired by the image reading device 2.

  The printer 3 employs an intermediate transfer method, and includes an image forming unit 10, a paper feed unit 20, an intermediate transfer unit 30, a fixing unit 40, and a control unit (not shown). The image forming unit 10 includes four stations 10a, 10b, 10c, and 10d. Since the stations 10a, 10b, 10c, and 10d have the same configuration, the configuration of the station 10a will be described here.

  The station 10a includes a photosensitive drum 11a, a primary charger 12a, an exposure unit 13a, a developing device 14a, a cleaning device 15a, and a folding mirror 16a. A photosensitive drum 11a as an image carrier is pivotally supported at its center and is driven to rotate in the direction of an arrow. Opposing the outer peripheral surface of the photosensitive drum 11a, a primary charger 12a, an exposure unit 13a of an optical system as an exposure unit, a folding mirror 16a, and a developing device 14a are arranged in the rotation direction.

  The primary charger 12a applies a uniform charge amount to the surface of the photosensitive drum 11a. Next, the exposure unit 13a exposes the photosensitive drum 11a through a folding mirror 16a with a light beam such as a laser beam modulated according to the recording image signal, thereby forming an electrostatic latent image there.

  Further, the electrostatic latent image is visualized by a developing device 14a containing a developer (hereinafter referred to as “toner”). The developing devices 14a to 14d respectively store toners of four colors, yellow, cyan, magenta, and black.

  A visible image (developed image) visualized by the developing device 14a is transferred to an image transfer area Ta of an intermediate transfer belt 31 described later, which is an intermediate transfer member.

  The cleaning device 15a cleans the drum surface by scraping off toner remaining on the photosensitive drum 11a without being transferred to the intermediate transfer belt 31 downstream of the photosensitive drum 11a rotating and passing through the image transfer area Ta. . Through the above process, image formation with each toner is sequentially performed by the stations 10a to 10d.

  The paper feed unit 20 includes cassettes 21a and 21b, a manual feed tray 27, pickup rollers 22a, 22b and 26, a paper feed roller pair 23, a paper feed guide 24, and registration rollers 25a and 25b.

  The cassettes 21 a and 21 b and the manual feed tray 27 store the transfer material P. The pickup rollers 22a, 22b, and 26 feed the transfer material P one by one from the cassettes 21a and 21b and the manual feed tray 27. The paper feed roller pair 23 and the paper feed guide 24 convey the transfer material P fed from the pickup rollers 22a, 22b, and 26 to the registration rollers 25a and 25b. The registration rollers 25 a and 25 b send the transfer material P to the secondary transfer region Te in accordance with the image formation timing of the image forming unit 10.

  The intermediate transfer unit 30 includes an intermediate transfer belt 31, a drive roller 32, a driven roller 33, a secondary transfer counter roller 34, primary transfer chargers 35a to 35d, a secondary transfer roller 36, a cleaning blade 51, a waste toner box 52, And a registration sensor 60.

  The intermediate transfer belt 31 is opposed to the secondary transfer region Te across the belt 31 as a winding roller, a driving roller 32 that transmits driving to the intermediate transfer belt 31, a driven roller 33 that follows the rotation of the intermediate transfer belt 31, and the belt 31. The secondary transfer counter roller 34 is wound around. Among these, a primary transfer surface A is formed between the driving roller 32 and the driven roller 33. The driving roller 32 is coated with rubber (urethane or chloroprene) on the surface of the metal roller to prevent slippage with the belt 31. The drive roller 32 is rotationally driven in the direction of arrow B by a pulse motor (not shown).

  The primary transfer surface A is opposed to the stations 10a to 10d, and the photosensitive drums 11a to 11d are opposed to the primary transfer surface A of the intermediate transfer belt 31. Accordingly, the primary transfer areas Ta to Td are positioned on the primary transfer surface A. Primary transfer chargers 35 a to 35 d are arranged behind the intermediate transfer belt 31 in the primary transfer regions Ta to Td where the photosensitive drums 11 a to 11 d and the intermediate transfer belt 31 face each other.

  A secondary transfer roller 36 is disposed to face the secondary transfer counter roller 34, and a secondary transfer region Te is formed by a nip with the intermediate transfer belt 31. The secondary transfer roller 36 is pressed against the intermediate transfer belt 31 with an appropriate pressure. Further, downstream of the secondary transfer region Te on the intermediate transfer belt 31, a cleaning blade 51 for cleaning the image forming surface of the intermediate transfer belt 31 and a waste toner box 52 for storing waste toner are provided. .

  The fixing unit 40 includes a roller pair 41, a guide 43, an inner discharge roller 44, an outer discharge roller 45, and a discharge tray 48.

  The roller pair 41 includes a fixing roller 41a having a heat source such as a halogen heater inside, and a pressure roller 41b that is pressed against the fixing roller 41a. A heat source may also be provided inside the pressure roller 41b.

  The guide 43 guides the transfer material P to the nip portion of the roller pair 41. The inner discharge roller 44 and the outer discharge roller 45 guide the transfer material P discharged from the roller pair 41 to the outside of the apparatus. When an image forming operation start signal is issued from a control unit (not shown), feeding of the transfer material P is started from the paper feed stage selected according to the selected paper size or the like.

  Next, a description will be added in accordance with the operation of the image copying apparatus 1.

  When an image forming operation start signal is issued from a control unit (not shown), first, the transfer material P is sent out one by one from the cassette 21a by the pickup roller 22a. The transfer material P is guided between the paper feed guides 24 by the paper feed roller pair 23 and conveyed to the registration rollers 25a and 25b. At that time, the registration rollers 25a and 25b are stopped, and the leading edge of the paper hits the nip portion. Thereafter, the registration rollers 25a and 25b start rotating in accordance with the timing at which the image forming unit 10 starts image formation. The rotation of the registration rollers 25a and 25b is set so that the transfer material P and the toner image primarily transferred from the image forming unit 10 onto the intermediate transfer belt 31 exactly coincide with each other in the secondary transfer region Te. ing.

  On the other hand, in the image forming unit 10, the toner image formed on the photosensitive drum 11 d that is the most upstream in the rotation direction of the arrow B of the intermediate transfer belt 31 is primary-transferred by the primary transfer charger 35 d to which a high voltage is applied. Primary transfer is performed on the intermediate transfer belt 31 in the transfer region Td. The primarily transferred toner image is conveyed to the next primary transfer region Tc. Image formation is performed by delaying the time during which the toner images are conveyed between the image forming units 10, and the next toner image is transferred with registration (image position) aligned on the previous image. The same process is repeated for the primary transfer areas Ta and Tb of other colors, and the four-color toner images are primarily transferred onto the intermediate transfer belt 31.

  Thereafter, when the transfer material P enters the secondary transfer region Te and contacts the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in accordance with the passing timing of the transfer material P. Then, the four color toner images formed on the intermediate transfer belt 31 by the above-described process are collectively transferred onto the surface of the transfer material P. Thereafter, the transfer material P is accurately guided to the nip portion of the fixing roller pair 41 by the conveyance guide 43. The toner image is fixed on the paper surface by the heat of the fixing roller pair 41 and the pressure of the nip. The transfer material P is conveyed by the inner and outer paper discharge rollers 44 and 45 and discharged to a paper discharge tray 48 outside the apparatus.

  In this type of image copying apparatus, a mechanical attachment error between the photosensitive drums 11a to 11d and an optical path length error of the laser beam generated by the exposure units 13a to 13d are generated. Also, due to reasons such as optical path changes and warpage due to the ambient temperature of the LED, registration shifts of the color images formed on the photosensitive drums 11a to 11d, that is, color shifts (registration shifts) occur. In order to correct these errors and deviations, a registration sensor that detects registration deviation at a position downstream of all the image forming units 10 on the primary transfer surface A and before the belt 31 is folded back by the driving roller 32. 60 is provided.

  FIG. 2 is a cross-sectional view showing a schematic configuration of the image reading apparatus 2 in FIG.

  In FIG. 2, the image reading apparatus 2 includes a reading unit 510, an original table glass 503, a second mirror 506, a third mirror 507, a lens 508, an image sensor 509, a shading correction plate 511, a member 512, and a pressure plate 513. The reading unit 510 includes a document illumination lamp 501 and a first mirror 505.

  The image of the original 504 placed on the original platen glass 503 is illuminated by the original illumination lamp 501 and is connected to the image sensor 509 via the first mirror 505, the second mirror 506, the third mirror 507, and the lens 508. Image. As a result, the image sensor 509 reads the line image of the document 504.

  A reading unit 510 including the document illumination lamp 501 and the first mirror 505 moves in the direction of arrow C and sequentially reads line images. At this time, the second mirror 506 and the third mirror 507 are also moved in the direction of arrow C, and are driven by a drive system (not shown) so that the distance (optical path length) from the document surface to the image sensor 509 is constant.

  A sequence in which the document image of the document 504 is actually read with the above configuration will be described.

  When an original reading command is input by an operator (specifically, a copy button is pressed, etc.), the image reading apparatus 2 cannot read the reading unit 510 from the arrangement shown in FIG. It is moved in the direction of arrow D by the illustrated drive system. As a result, the reading position of the reading unit 510 is arranged directly below the shading correction plate 511.

  Next, the image reading apparatus 2 turns on the document illumination lamp 501 to illuminate the shading correction plate 511. The reflected light of the shading correction plate 511 is guided to the image sensor 509 via the first mirror 505, the second mirror 506, the third mirror 507, and the lens 508 as a line image of the shading correction plate 511.

  The output signal for each pixel of the line image of the shading correction plate 511 read by the image sensor 509 is corrected so that the output level of all the pixels becomes a predetermined level by an image processing circuit (not shown). By this image processing, uneven illuminance of the document illumination lamp 501, a decrease in peripheral light amount of the lens 508, and uneven sensitivity of each pixel of the image sensor 509 are corrected, and uneven reading of the document image is corrected. When the shading correction process is completed, the reading unit 510 is further moved in the direction of arrow D by a drive system (not shown), and is disposed immediately below the member 512.

  Directly below the member 512 is a document image reading start position, and from this position, a driving system (not shown) accelerates the reading unit 510 in the direction of arrow C. The reading unit 510 is controlled so as to be driven at a constant speed at a predetermined speed until the reading position reaches the leading end of the original 504 that is pressed by the pressure plate 513 and maintains flatness.

  When the reading position of the reading unit 510 reaches the leading end of the document 504, the image sensor 509 starts reading the line images of the document 504 sequentially.

  A drive system (not shown) moves the reading unit 510 in the direction of arrow C while maintaining a constant speed, and stops reading after the reading to the end of the original 504 is completed. Thereafter, the drive system moves the reading unit 510 in the direction of arrow D to return to the home position shown in FIG. 2, ends a series of image reading, and waits for the next reading.

  This is the end of the description of the basic image reading operation of the image reading apparatus 2.

  By the way, the document illumination lamp 501 is composed of an LED substrate on which 48 white LEDs are linearly arranged. Next, the LED substrate constituting the document illumination lamp 501 will be described.

  FIG. 3 is a diagram showing a part of the configuration of the LED substrate included in the document illumination lamp 501 in FIG.

  In FIG. 3, the LED substrate 200 includes eight LED blocks. FIG. 3 shows only two of the LED blocks 101a and 101b. Each LED block includes six LEDs 201 connected in series. Therefore, the LED substrate 200 includes 48 LEDs 201.

  The LED blocks 101a and 101b are connected to drive circuits 104a and 104b via changeover switches 102a, 102b, 103a, and 103b, respectively.

  The drive circuits 104a and 104b are composed of constant current circuits. When the forward voltage per LED 201 is 3.3V, a voltage of 3.3 × 6 = 19.8V or more is applied to obtain a desired current. Is supplied to the LED blocks 101a and 101b. Accordingly, the drive circuits 104a and 104b turn on the LEDs 201 mounted on the LED blocks 101a and 101b.

  The drive circuits 104a and 104b connected to the LED blocks 101a and 101b are set to a constant current drive of 20 mA as a standard in order to drive one LED block. It also has a current control function for finely adjusting the amount of light for each LED block.

  FIG. 4 is a diagram illustrating an example of a control circuit of the image reading apparatus 2 of FIG.

  In FIG. 4, the image reading apparatus 2 includes an LED substrate 200, a control circuit substrate 701, an LED drive circuit control unit 707, an image sensor 509, and an I / F circuit 708.

  The control circuit board 701 includes a CPU 702, an ASIC 703, a ROM 704, and a RAM 705, which are connected to each other via a system bus 706.

  The ASIC 703 is a large-scale integrated circuit that transmits / receives image processing such as shading correction and control signals to the main unit of the image reading apparatus 2 according to a command from the CPU 702. The ROM 704 stores a control program for the CPU 702. The RAM 705 is used as a calculation area by the CPU 702.

  The ASIC 703 is connected to an LED drive circuit control unit 707, an image sensor 509, and an I / F circuit 708. A line image of the document image sent from the image sensor 509 is input to the ASIC 703.

  The ASIC 703 is connected to an external device such as a printer (not shown) connected to the I / F circuit 708, performs image processing on the read document image, and sends an image signal to the external device.

  The LED drive circuit control unit 707 includes a total of eight circuits including, for example, the changeover switches 102a and 103a and the drive circuit 104a shown in FIG. The changeover switch constituted may be a mechanical changeover switch such as a micro relay, or a semiconductor switch constituted by a switching transistor or the like.

  Each drive circuit and each changeover switch are configured to receive control from the CPU 702 via the ASIC 703. The LED board 200 is connected to the LED drive circuit controller 707. As described above, the LED board 200 is composed of 8 circuits each having 6 LEDs as one block, and the LED board 200 and the LED drive circuit control unit 707 are connected with the structure shown in FIG. Yes.

  When all the LED blocks mounted on the LED substrate 200 are normally lit, the changeover switches 102a, 102b, 103a, and 103b have the changeover switches at the positions shown in FIG. Therefore, one LED block corresponds to one drive circuit on a one-to-one basis. At this time, if unevenness in the light quantity of each LED block can be confirmed during the shading correction process, the CPU 702 controls the LED drive circuit control unit 707 via the ASIC 703 to finely adjust the drive current set for each drive circuit. .

  FIG. 5 is a view of the platen glass 503 in FIG. 2 as viewed from above.

  In FIG. 5, the document table glass 503 includes a main scanning index 401, a sub scanning index 402, and a reference mark 403. The user places the original 504 on the original platen glass 503 with the original size marked on the index and the corner of the original placed on the reference mark 403. FIG. 5 shows a state in which an A4 size document 504 is placed according to an A4 index.

  Here, a case where the LED block 101a of the LED block group 101 stops lighting due to a failure of the drive circuit 104a will be described. In this case, in the LED block 101a, all six LEDs 201 are not lit, and the original function as an image reading apparatus cannot be exhibited.

  6 is a diagram showing a relative positional relationship between the main scanning index 401 and the LED substrate 200 in FIG.

  In FIG. 6, the LED substrate 200 is driven in the sub-scanning direction of the arrow E to illuminate the document. The LED block group 101 including the LED blocks 101a and 101b is arranged linearly with respect to the main scanning direction.

  Here, the LED block 101a hatched due to the failure of the drive circuit 104a is not lit. Therefore, when an A4 size document is placed as shown in FIG. 5, if the reading operation is performed as it is, the portion facing the LED block 101a is not illuminated and a normal read image is not obtained. Further, even if a document is placed according to the A4R index as shown in FIG.

  FIGS. 8A and 8B are diagrams showing a relative relationship between the reading levels of the LED block group 101 and the shading correction plate 511 in FIG. 6, where FIG. 8A shows a normal time and FIG. 8B shows a time when the drive circuit 104 a fails.

  In FIG. 8A, after fine adjustment of the drive current, the reading level 601 of the shading correction plate 511 is a uniform reading level in the illumination range by the LED block group 101.

  In FIG. 8B, when the drive circuit 104a is faulty, the reading level 602 of the shading correction plate having a uniform white density has a low profile at a location facing the LED block 101a. As described above, the image reading apparatus 2 detects the failure of the drive circuit 104a by executing the shading correction process. When a failure of the drive circuit 104a is detected, a normal read image is not obtained even if the reading operation is performed as it is, so the CPU 702 controls the image sensor 509 so as not to perform the reading operation. Further, the CPU 702 switches the changeover switches 102a, 102b, 103a, and 103b in the LED drive circuit control unit 707 as illustrated in FIG. 9 via the ASIC 703.

  FIG. 9 is a diagram showing a configuration of the LED substrate 200 when the drive circuit 104a in FIG.

  In FIG. 9, the LED block 101a is connected to the normally operating drive circuit 104b by switching the switches 102a, 102b, 103a, and 103b. The LED block 101b is connected to the drive circuit 104a that has failed. Thereby, the lighting state of the LED substrate 200 becomes as shown in FIG.

  In FIG. 10, the LED block 101a is turned on and the LED block 101b is turned off. Of course, a normal read image cannot be obtained even if an A4 size document is placed as shown in FIG. 5, but the document placement direction is changed according to the A4R index as shown in FIG. As a result, A4 size originals can be read.

  It is desirable that the CPU 702 notifies the user by displaying a message on a display unit (not shown) so that the document is placed on the A4R after detecting that the document is placed according to the A4 index. . As a result of document size detection, if the placed document cannot be read even if the drive circuit is switched by the above method, the reading operation process is interrupted and a message indicating that reading cannot be performed. Is displayed on the display unit or the like to be notified to the user. Further, it may be controlled so that a message prompting the user to replace the failed LED board 200 is displayed on the display unit or the like.

  As a method for detecting the document size, a method for detecting the document size using a reflection type sensor (for example, see Japanese Patent Laid-Open No. 5-330668) may be used. Alternatively, a method of detecting a document size by using a reading sensor that reads an image together with a reflective sensor (for example, see Japanese Patent Application Laid-Open No. 2001-28049) may be used.

  As described above, the line image data of the original read by the configuration of FIG. 2 is sequentially sent to the printer 3, and the read image is formed by the printer 3.

  According to the first embodiment, since the LED block 101a is connected to the drive circuit 104b that is operating normally, even if the drive circuit of the LED block fails, a normal read image can be obtained.

[Second Embodiment]
In the first embodiment, the method of expanding the readable document size range by replacing the failed drive circuit with the adjacent drive circuit has been described. However, the present invention is a method of replacing the adjacent LED drive circuits. It is not limited.

  In the first embodiment, the case where the drive circuit 104a has failed has been described. However, when the drive circuit at the front end in the main scanning direction out of a plurality of drive circuits provided in the first place, all the document sizes are set. It becomes unreadable. In the second embodiment, in view of this problem, a method for solving the problem using the present invention will be described.

  FIG. 11 is a diagram illustrating a relative positional relationship between the main scanning index 401 and the LED substrate 200 according to the second embodiment of the present invention.

  FIG. 11 shows a state in which the drive circuit connected to the LED block 101c has failed and the LED block 101c is turned off. Since the LED block 101c is an LED block that illuminates the leading end of the main scanning reading area of the original, it is impossible to read all the original sizes displayed on the main scanning index 401 regardless of the original placement direction.

  In the second embodiment, the configuration of the LED substrate shown in FIG. 3 is applied to the LED block 101c and the LED 101d disposed at the rear end with respect to the main scanning direction. The CPU 702 in FIG. 4 switches between the drive circuit of the LED block 101c that has failed and the drive circuit of the LED block 101d that is operating normally. Thereby, the lighting state of the LED board 200 becomes as shown in FIG.

  In FIG. 12, the LED block 101c disposed at the front end in the main scanning direction is turned on by switching the drive circuit of the LED block 101c and the LED block 101d. On the other hand, the LED block 101d disposed at the rear end with respect to the main scanning direction is turned off.

By this drive circuit switching control, postcards, A5R, B5R, A5 / A4R, B5 / B4, that is, all the standard document sizes other than the document size A3 can be read, and the image reading apparatus has improved convenience for the user. Can be provided.
According to the second embodiment, by switching between the drive circuit of the faulty LED block 101c and the drive circuit of the normally operating LED block 101d, the front-end drive circuit fails in the main scanning direction. In this case, a normal read image can be obtained.

1 is a cross-sectional view showing an internal configuration of an image copying apparatus equipped with an image reading apparatus according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic configuration of an image reading apparatus 2 in FIG. 1. FIG. 3 is a diagram showing a part of the configuration of an LED substrate included in the document illumination lamp 501 in FIG. 2. FIG. 3 is a diagram illustrating an example of a control circuit of the image reading apparatus 2 in FIG. 2. FIG. 3 is a view of the document table glass 503 in FIG. 2 as viewed from above. FIG. 6 is a diagram illustrating a relative positional relationship between the main scanning index 401 and the LED substrate 200 in FIG. 5. FIG. 3 is a view of the document table glass 503 in FIG. 2 as viewed from above. FIG. 7 is a diagram illustrating a relative relationship between reading levels of the LED block group 101 and the shading correction plate 511 in FIG. 6, where (a) shows a normal time, and (b) shows a time when the drive circuit 104 a fails. It is a figure which shows the structure of the LED board 200 at the time of failure of the drive circuit 104a in FIG. FIG. 6 is a diagram illustrating a relative positional relationship between the main scanning index 401 and the LED substrate 200 in FIG. 5. It is a figure which shows the relative positional relationship of the main scanning parameter | index 401 and LED board 200 in the 2nd Embodiment of this invention. It is a figure which shows the relative positional relationship of the main scanning parameter | index 401 and LED board 200 in the 2nd Embodiment of this invention. It is a figure which shows the structure of the conventional LED board. It is a figure which shows the structure of the conventional LED block.

Explanation of symbols

101a, 101b LED blocks 102a, 102b, 103a, 103b Changeover switches 104a, 104b Drive circuit 200 LED board 201 LED

Claims (5)

An illuminating means having a plurality of blocks arranged linearly in the main scanning direction and illuminating the document while moving in the sub-scanning direction;
A plurality of lighting means connected to each of the plurality of blocks and lighting the connected blocks;
An image reading apparatus comprising: reading means for reading an image of the original from the original illuminated by the illumination means;
Detecting means for detecting a malfunctioning lighting means among the plurality of lighting means;
An image reading apparatus comprising: a switching unit that replaces the detected lighting unit that has failed and is replaced with a lighting unit that has not failed. Detecting means for detecting the size of the document;
2. The apparatus according to claim 1, further comprising a control unit that controls the reading unit so that an image is not read from the original when the size of the detected original is larger than a size that can be illuminated by the illumination unit. Image reading apparatus.   When the detected size of the document is larger than the size that can be illuminated by the illumination unit, the user is notified when the document can be illuminated by the illumination unit by changing the orientation of the document. The image reading apparatus according to claim 2, further comprising a notification unit configured to perform notification.   The switching means replaces and connects the lighting means for lighting the block arranged at the front end in the main scanning direction among the plurality of blocks with the lighting means for lighting the block arranged at the rear end. The image reading apparatus according to any one of claims 1 to 3.   The image reading apparatus according to claim 1, further comprising a display unit configured to display a message that prompts a user to replace the illumination unit.

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