JP2010252216A - Image reader, and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a standard document size for a reading object document without increasing cost nor requiring an extra operation to a user for inputting document size information even when a failure part is detected in an LED as a light source. <P>SOLUTION: An image reader includes: a white determination part 214 for determining whether an image read by a scanner part 22 is white or black based on a white reference threshold; a failure detection part 2112 for detecting a failure of an LED of the scanner part 22 for every block based on a white reference value; a white reference threshold correction part 215 for reducing the white reference threshold when a failure is detected in any of the blocks; a document width calculation part 2110 for calculating a change point where the read image changes from white to black in a main scanning direction as a document width of a reading object document based on the determination result of the white determination part 214 using the white reference threshold after the correction; and a document size calculation part 2111 for calculating a standard document size having the calculated document width. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image reading apparatus and an image forming apparatus, and more particularly to a technique for detecting the size of a document to be read.

  2. Description of the Related Art Conventionally, as a light source for an image reading apparatus, an LED array light source in which an LED group having advantages of low heat generation and low power consumption has been proposed. This LED array light source is configured to be connected to the drive circuit for each block composed of a plurality of LEDs, so that when a malfunction occurs in the electrical system, a part that cannot be partially read occurs, but a halogen lamp or Unlike xenon tubes, the risk of all LED groups disappearing is reduced. For this reason, as shown in Patent Document 1 below, even when a faulty part is detected in some LEDs, the reading of the document that is the reading target at that time is sufficient for light irradiation other than the faulty part. Makes it possible to read a document by bringing the document to an area other than the failed part even if a failure part is detected in the LED as a light source, as shown in the following Patent Document 2 Technology has been proposed.

JP 2004-64406 A JP 2007-201952 A

  As in each of the prior arts described above, the size information of the document to be read is necessary to perform document reading when a failure of the LED as the light source is detected. However, as a method for determining the document size, (1) the document size is detected by a reflective sensor installed at the boundary where the document size is switched on the document reading table, and (2) document size information input from the user to the operation unit Have been proposed, or (3) the size of the original is determined by reading the original with a line sensor, but these require a special mechanism for acquiring the original size information. In addition, there is a problem that the cost is increased, or that the user is required to perform an extra operation for inputting document size information.

  The present invention has been made to solve the above-described problem. Even when a failure portion is detected in an LED as a light source, the document size information is input to the user without causing an increase in cost. It is an object of the present invention to enable detection of a standard document size for a document to be read without requiring an extra operation.

According to the first aspect of the present invention, there is provided a transparent document table on which a document to be read is placed;
A plurality of LEDs arranged in the main scanning direction are connected to a drive circuit for each of a plurality of blocks arranged in the main scanning direction, and the original placed on the original table is irradiated by the light source to irradiate the original. An image reading unit having a photoelectric conversion element for reading an image;
A white reference member disposed at a position where image reading by the image reading unit is possible;
A white reference value storage unit that stores a white reference value acquired by the reading operation of the white reference member by the image reading unit;
A white determination unit that determines whether the image read by the image reading unit indicates white or black based on a predetermined white reference threshold;
A failure detection unit that detects whether or not a failure has occurred in the LED for each block based on a white reference value acquired by the reading operation of the white reference member by the image reading unit;
A white reference threshold correction unit that performs correction to reduce the white reference threshold by a predetermined value when a failure is detected in any of the blocks by the failure detection unit;
Based on the determination result for the read image of the image reading unit by the white determination unit based on the corrected white reference threshold, a change point at which the read image changes from white to black in the main scanning direction. A document width calculating unit that calculates a document width in the main scanning direction of the document to be read;
An image reading apparatus including a document size calculation unit that calculates a standard document size having a document width calculated by the document width calculation unit.

  In this invention, the white reference threshold value correction unit performs correction to reduce the white reference threshold value by a predetermined value when a failure is detected in any of the blocks by the failure detection unit, and the document width calculation unit includes: Based on the determination result for the read image of the image reading unit by the white determination unit based on the corrected white reference threshold, a change point at which the read image changes from white to black in the main scanning direction is defined as the reading target. This is calculated as the document width in the main scanning direction of the document being read. As a result, the present invention reduces the amount of light in the irradiation area of the block due to the failure of the block, and the change point can be accurately detected for an image read in the irradiation area where the amount of light is reduced. The accuracy of document width calculation based on the image read by the reading unit can be improved. Therefore, according to the present invention, even if a failure portion is detected in the LED as the light source, the cost is not increased, and an extra operation for inputting document size information to the user is not required. The standard document size can be detected for the document to be read.

  The invention according to claim 2 is the image reading apparatus according to claim 1, wherein the light source of the image reading unit is in the vicinity of the boundary portion between the blocks, and the main scanning of different standard document sizes. This is arranged as a document size switching point corresponding to the document width in the direction.

  In the present invention, since the vicinity of the boundary between the blocks is arranged to be the document size switching point, the block near the paper width edge of the document to be read in the main scanning direction fails and the block Even when the amount of light in the irradiation region is small, the amount of light in the irradiation region of the failed block is easily compensated by the LED irradiation of the block adjacent to the failed block. For this reason, according to the present invention, it is easy to ensure the brightness of the image read in the irradiation area where the amount of light is reduced, and the accuracy of document width calculation based on the image read by the image reading unit is improved.

  The invention according to claim 3 is the image reading apparatus according to claim 1 or 2, wherein the white reference threshold value correction unit detects a failure in one of the blocks by the failure detection unit. When the white reference threshold is corrected, the white reference threshold is corrected to a value that is 50% of the white reference value acquired by the image reading unit.

  According to this invention, when a failure is detected in any of the above blocks by the failure detection unit, the white reference threshold correction unit sets the white reference threshold to 50% of the white reference value acquired by the image reading unit. Since the correction is made to the value, it is possible to accurately perform the above determination by the white determination unit in accordance with the amount of light in the irradiation area of the failed block.

According to a fourth aspect of the present invention, there is provided an image reading apparatus according to any one of the first to third aspects,
An image forming apparatus including an image forming unit that forms an image based on a document image read by the image reading apparatus.

  According to this invention, the effect obtained by the invention according to any one of claims 1 to 3 can be exhibited.

  According to the present invention, even when a failure portion is detected in the LED as the light source, without incurring an increase in cost, without requiring an extra operation for inputting document size information to the user, It is possible to detect a standard document size of a document to be read.

1 is a longitudinal sectional view schematically showing an internal configuration of a multifunction machine according to an embodiment. It is a figure which shows schematic structure of the LED array light source of a scanner part. It is a figure which shows the relationship between each block of a LED array light source, and a fixed document size. 1 is a schematic side view showing an image reading apparatus of a multifunction machine. 1 is a block diagram illustrating a schematic configuration of an image reading circuit of an image reading apparatus. It is a block diagram showing an internal configuration of a white color determination unit, a white reference threshold value correction unit, a document size calculation unit, a failure detection unit, and a shading correction unit. It is a figure which shows the example of the sample data of a white reference value. 6 is a diagram illustrating an example of pixel value sample data in image reading performed when a document size is detected by a scanner unit. FIG. 6 is a flowchart illustrating processing during an image reading operation performed by a scanner unit of the multifunction peripheral. It is a figure which shows the relationship between the white reference value at the time of failure of a light source, and a white reference threshold value. FIG. 4 is a diagram showing a positional relationship between a document placed on a contact glass and each block of a light source.

  Hereinafter, an image reading apparatus and an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the following embodiment, an example in which the image reading apparatus and the image forming apparatus according to the present invention are integrated into a multifunction machine having functions such as a color copy, a scanner, a facsimile, and a printer will be described.

  FIG. 1 is a longitudinal sectional view schematically showing the internal configuration of the multifunction machine 1 according to the present embodiment. FIG. 2 is a diagram showing a schematic configuration of the LED array light source of the scanner unit. FIG. 3 is a diagram showing the relationship between each block of the LED array light source and the standard document size.

  The multifunction device 1 is roughly composed of an image reading device 2 and a device body 3. The image reading apparatus 2 includes a document feeding unit (document feeding unit) 21 and a scanner unit 22. The document feeder 21 implements ADF, and includes a document tray 241, a sheet feed roller 232, a transport drum 233, a sheet discharge roller 234, and a sheet discharge tray 235. The document tray 241 is a place where the document is placed. The documents placed on the document tray 241 are taken one by one by the paper feed roller 232 and conveyed to the conveyance drum 233. The document that has passed through the transport drum 233 is discharged to a discharge tray 235 by a discharge roller 234.

  A scanner unit (an example of an image reading unit) 22 optically reads an image of a document and generates image data. The scanner unit 22 is provided in the apparatus main body 3. The scanner unit 22 includes a contact glass 221, a light source 222, a first mirror 223, a second mirror 224, a third mirror 225, a first carriage 226, a second carriage 227, an imaging lens 228, and a CCD (Charge Coupled Device) 229. Prepare. The scanner unit 22 uses an LED array light source as the light source 222, and the first mirror 223, the second mirror 224, the third mirror 225, the first carriage 226, the second carriage 227, and the imaging lens 228, from the document. Is guided to the CCD 229.

  As shown in FIG. 2, the scanner unit 22 includes, as a light source 222, a plurality of LEDs 220 arranged in the main scanning direction and a DC-DC converter 2221 for each of the plurality of blocks A to E arranged in the main scanning direction. And an LED array light source connected to a driving circuit such as a low current driving circuit 2222. The low current drive circuit 2222 is connected to a control unit 2115 described later. In the present embodiment, an example is shown in which the light source 222 includes a LED whose size in the main scanning direction is 5 mm. In this case, 11 blocks A, 9 blocks B, 12 blocks C, 17 blocks D, and 8 blocks E are provided with LEDs.

  In the present embodiment, as shown in FIG. 3, each of the blocks A to E has a boundary portion between the blocks in the main scanning direction in the main scanning direction in the document reading area. A document size switching point corresponding to the document width is provided. For example, block A has a width of 10.5 cm in the main scanning direction, block B has a width of 4.5 cm in the main scanning direction, block C has a width of 6 cm in the main scanning direction, block D has a width of 8.5 cm in the main scanning direction, block E is arranged in parallel in the main scanning direction with a width of 4 cm in the main scanning direction. Thus, by setting the width in the main scanning direction of each of the blocks A to E, a document size switching point corresponding to a document width of A6 size 105 mm (105 mm × 148 mm) is located at the boundary between the block A and the block B. A document size switching point corresponding to the document width of A5 size 148 mm (148 mm × 210 mm) is located in the vicinity of the boundary portion between block B and block C, and A4 size 210 mm (210 mm × 210 mm × 210 mm × 210 mm × 297 mm) and a document size switching point corresponding to a document width of A3 size 297 mm (297 mm × 420 mm) is positioned near the boundary between block D and block E. Become. In the present embodiment, the arrangement of the LED provided in the light source 222 in the main scanning direction is assumed to be 5 mm. However, the size of the LED is different from that of the present embodiment, and each block When the document size switching point can be arranged at the boundary portion between the blocks, the document size switching point may be arranged at the boundary portion between the blocks.

  The CIS 231 is provided downstream of the scanner unit 22 in the document conveyance direction. The CIS 231 is provided at a position where the surface opposite to the document surface read by the scanner unit 22 can be read in the document transport path.

  A contact glass (an example of a document table in the claims) 221 is a place for placing a document. The document feeder 21 is attached to the upper surface edge of the apparatus body 3 (the back side in the drawing in FIG. 1) so as to be rotatable in the contact / separation direction with respect to the contact glass 221. In the flatbed reading mode described later, the user rotates the document feeder 21 in a direction away from the contact glass 221 to expose the contact glass 221.

  The light source 222 and the first mirror 223 of the scanner unit 22 are supported by the first carriage 226, and the second mirror 224 and the third mirror 225 are supported by the second carriage 227.

  As an original reading method of the image reading apparatus 2, there are a flat bed reading mode in which the scanner unit 22 reads an original placed on the contact glass 221 and an ADF reading mode in which the original is taken in by ADF and the original is read during the conveyance. is there.

  In the flat bed reading mode, the light source 222 irradiates a document placed on the contact glass 221, and reflected light for one line in the main scanning direction is reflected in the order of the first mirror 223, the second mirror 224, and the third mirror 225. Then, the light enters the imaging lens 228. The light incident on the imaging lens 228 is imaged on the light receiving surface of the CCD 229. The CCD 229 is a one-dimensional image sensor, and simultaneously processes a document image for one line. When the reading for one line is completed, the first carriage 226 and the second carriage 227 are moved in the direction orthogonal to the main scanning direction (sub-scanning direction, arrow Y direction), and the next line is read.

  In the ADF reading mode, the originals placed on the original tray 241 are taken one by one by the paper feed roller 232, and the originals are placed on the image reading position 230 provided in the conveyance path from the conveyance drum 233 to the paper discharge tray 235. When passing, the light source 222 irradiates the document, and the reflected light for one main scanning line is reflected in the order of the first mirror 223, the second mirror 224, and the third mirror 225, and enters the imaging lens 228. The light incident on the imaging lens 228 is imaged on the light receiving surface of the CCD 229. Subsequently, the document is conveyed by the document feeder 21 and the next line is read. In the following description, those not specifically described will be described on the assumption that an original is automatically fed in the flatbed reading mode and an image is read.

  Further, the document feeder 21 has a document reversing mechanism including a switching guide 236, a reversing roller 237, and a reversing conveyance path 238. The original whose surface (one side of the original) is read by the first ADF reading is reversed using the original reversing mechanism and conveyed again, so that the CCD 229 reads the back side (the other side of the original) again. Can be done. This document reversing mechanism operates only when reading both sides, and does not operate when reading one side. After reading the back side during single-sided reading and double-sided reading, the switching guide 236 is switched to the upper side, and the document that has passed through the transport drum 233 is discharged onto the discharge tray 235 by the discharge roller 234. After the surface reading at the time of double-sided reading, the switching guide 236 is switched to the lower side, and the document that has passed through the conveying drum 233 is conveyed to the nip portion of the reversing roller 237. Thereafter, the switching guide 236 is switched upward and the reversing roller 237 rotates in the reverse direction, whereby the document is re-conveyed to the conveying drum 233 via the reverse conveying path 238.

  Further, in the ADF reading mode, the image reading apparatus 2 according to the present embodiment causes the CCD 229 to read the front surface of the document while the document is being conveyed as described above, and at the same time reads the back side of the document by the CIS 231. Can be performed. That is, the front side of the original fed from the original tray 241 is read by the CCD 229 when passing over the image reading position 230, and the back side is read when passing through the CIS 231. By using the CCD 229 and the CIS 231 in this way, it is possible to read both sides of a document with one pass.

  The multifunction device 1 includes an apparatus main body 3 and a stack tray 6 disposed on the left side of the apparatus main body 3. The apparatus main body 3 includes a plurality of paper feed cassettes 461, a paper feed roller 462 that feeds sheets (recording media) one by one from the paper feed cassette 461 and conveys them to the recording unit (image forming unit) 40, and a paper feed cassette 461. And a recording unit 40 that forms an image on the sheet conveyed from the printer. Further, a manual feed tray 471 is provided. From this manual feed tray 471, paper of a size that is not stored in any paper feed cassette, paper on which an image is already formed on one side (back paper), or an OHP sheet is provided. An arbitrary recording medium can be placed, and is fed into the apparatus main body 3 one by one by a paper feed roller 472.

  The recording unit 40 is based on a charge eliminating device 421 that removes residual charges from the surface of the photosensitive drum 43, a charging device 422 that charges the surface of the photosensitive drum 43 after charge removal, and image data acquired by the scanner unit 22. The laser beam is output to expose the surface of the photosensitive drum 43, and an exposure device 423 that forms an electrostatic latent image on the surface of the photosensitive drum 43, and on the photosensitive drum 43 based on the electrostatic latent image, Developing devices 44C, 44M, 44Y, and 44K that form toner images of each color of cyan (C), magenta (M), yellow (Y), and black (K), and toner images of each color that are formed on the photosensitive drum 43 A transfer drum 49 on which toner images are transferred, a transfer device 41 that transfers the toner image on the transfer drum 49 to a sheet, and a sheet on which the toner image has been transferred is heated to set the toner image on the sheet. And a fixing device 45 for. Note that toner is supplied to each color of cyan, magenta, yellow, and black from a toner supply container (toner cartridge) (not shown). Further, conveyance rollers 463 and 464 that convey the sheet that has passed through the recording unit 40 to the stack tray 6 or the discharge tray 48 are provided.

  When images are formed on both sides of a sheet, after the recording unit 40 forms an image on one side of the sheet, the sheet is nipped by a conveyance roller 463 on the discharge tray 48 side. In this state, the transport roller 463 is rotated in the reverse direction to switch back the paper, and the paper is sent to the paper transport path L to be transported again to the upstream area of the recording unit 40. The recording unit 40 forms an image on the other surface. Then, the paper is discharged to the stack tray 6 or the discharge tray 48.

  Further, in front of the apparatus main body 3, a display unit 51 that allows a user to visually recognize an operation screen and various messages, and an operation unit 5 having operation buttons for inputting various operation commands are provided. . The operation unit 5 includes a display unit 51 including a touch panel, a numeric key group 53, a start button 55, and the like. The display unit 51 is configured by an LCD (Liquid Crystal Display), an ELD (Electronic Luminescent Display), or the like, and displays selection screens such as paper size selection, magnification selection, and density selection.

  Next, an operation of acquiring the black reference value and the white reference value for shading correction by the scanner unit 22 and the CIS 231 will be described. FIG. 4 is a schematic side view showing the image reading device 2 of the multifunction machine 1.

  In the image reading apparatus 2 of the present embodiment, a white reference plate (white reference member) 10 is provided at a position that is out of the image reading position 230 and that can be read by the scanner unit 22. The white reference plate 10 is a white belt-like member attached to the contact glass 221 so as to extend in the main scanning direction (a direction orthogonal to the paper surface in FIG. 4). When the scanner unit 22 acquires a white reference value for shading correction, the first carriage 226 and the second carriage 227 move to the position of the white reference plate 10 in the sub-scanning direction, and the white color of the white reference plate 10 is moved by the light source 222. The white surface is read with the surface illuminated. When the scanner unit 22 acquires the black reference value for shading correction, the first carriage 226 and the second carriage 227 are similarly moved to the position of the white reference plate 10, the light source 222 is turned off, and the white reference plate 10 is turned off. The white surface is read in a state where the white surface is not irradiated.

  Next, an image reading circuit for the image reading device 2 in the multifunction machine 1 will be described. FIG. 5 is a block diagram illustrating a schematic configuration of the image reading circuit of the image reading apparatus 2. The image reading circuit 210 of the image reading apparatus 2 includes a CPU 211, a RAM 212, a ROM 213, a white color determination unit 214, a white reference threshold value correction unit 215, an A / D conversion unit 217, a shading correction unit 218, and image processing. Part 219. These units are communicably connected to each other via a bus BUS.

  The CPU 211 is a control circuit for managing overall operation control of the multifunction machine 1. The CPU 211 performs a document width calculation unit 2110, a document size calculation unit 2111, a failure detection unit 2112, a determination by an operation according to the operation control program of the MFP 1 and the image reading device 2 stored in the ROM 212 or the HDD (not shown). Functions as a unit 2113, a display control unit 2114, and a control unit 2115.

  The document width calculation unit 2110 determines a change point at which the pixel value of the read image changes from white to black in the main scanning direction based on the determination result by the white color determination unit 214 for the image of the document read by the scanner unit 22. The document width in the main scanning direction of the document is calculated.

  The document size calculation unit 2111 calculates a standard document size having the document width calculated by the document width calculation unit 2110.

  The failure detection unit 2112 detects whether or not a failure has occurred in the LED constituting the light source 222 for each of the blocks based on the image read by the scanner unit 22. Details of the failure detection processing by the failure detection unit 2112 will be described later.

  The display control unit 2114 controls display control of the display unit 51. For example, when the failure detection unit 2112 detects a failure in one of the blocks of the light source 222, the display control unit 2114 prompts an input of an instruction as to whether or not the scanner unit 22 should read the original image. Is displayed on the display unit 51.

  The control unit 2115 is responsible for overall operation control of the multifunction machine 1 and is also responsible for operation control of the image reading apparatus 2. For example, the control unit 2115 operates as a white reference value for shading correction and an operation of a driving mechanism such as the scanner unit 22 and the CIS 231 necessary for performing an image reading operation for acquiring the white reference value, or the operation unit 5 includes the scanner unit 22. When the input of an instruction to cause the document to be read is received, the image reading operation or the like for the document from which the document size is detected is controlled.

  The RAM 212 is a storage mechanism used as a work area when controlling the operations of the multifunction machine 1 and the image reading apparatus 2 according to the operation control program by the CPU 211.

  The ROM 213 stores the operation control program and the like.

  The operation unit 5 receives various operation instructions such as a copy operation start instruction from the operator.

  The white color determination unit 214 uses a predetermined white reference threshold value (for example, a pixel value (luminance) 128 in the case of monochrome binary data) stored in a built-in memory, and sets a value equal to or higher than the white reference threshold value. The pixel is determined to be white, and the pixel having a value smaller than the white reference threshold is determined to be black, thereby determining whether the image indicated by the document image read by the scanner unit 22 is white or black. . When the white reference threshold correction unit 215 corrects the white reference threshold, the white determination unit 214 uses the corrected white reference threshold to determine whether the image indicated by the document is white or black. It is determined whether or not.

  When the failure detection unit 2112 detects a failure in any of the blocks A to E, the white reference threshold correction unit 215 sets the white reference threshold stored in the white determination unit 214 to a predetermined value (for example, Correction is performed to reduce the pixel value by 50% of the white reference value stored in the white reference memory 2182).

  The A / D conversion unit 217 converts read image data composed of analog electric signals sent from the CCD 229 and the CIS 231 of the scanner unit 22 into digital read image data. Further, the A / D conversion unit 217 outputs the read image data after the digital conversion to the shading correction unit 218.

  The shading correction unit 218 uses the white reference value and the black reference value acquired by the reading operation of the white reference plate 10 by the scanner unit 22 and the reading operation of the shading roller 11 by the CIS 231, respectively. The shading correction is performed on each original image read in step (b). The shading correction unit 218 sends the data of the document image after the shading correction to the image processing unit 219.

  The image processing unit 219 performs various types of image processing on the shading-corrected image data sent from the shading correction unit 218. For example, the image processing unit 219 performs image processing such as level correction and gamma correction, image data compression or expansion, and enlargement or reduction on the image data.

  Next, the internal configuration of the document size calculation unit 2111 and the shading correction unit 218 will be described. FIG. 6 is a block diagram showing the internal configuration of the white color determination unit 214, white reference threshold value correction unit 215, document size calculation unit 2111, failure detection unit 2112, and shading correction unit 218. FIG. 7 is a diagram illustrating an example of white reference value sample data. FIG. 8 is a diagram illustrating an example of pixel value sample data in image reading performed when the scanner unit detects the document size.

  The shading correction unit 218 includes a black reference memory 2181, a white reference memory 2182, and a shading correction circuit 2185.

  The black reference memory 2181 stores the black reference value B (n) for shading correction acquired by the scanner unit 22 and the CIS 231.

  A white reference memory (white reference value storage unit) 2182 stores the white reference value W (n) for shading correction acquired by the scanner unit 22 and the CIS 231.

  The shading correction circuit 2185 is read by the scanner unit 22 or the CIS 231 using the black reference value and the white reference value acquired by the reading operation of the white reference plate 10 by the scanner unit 22 or the reading operation of the shading roller 11 by the CIS 231. Shading correction is performed on the original image. For example, in the case of 256 gradations, the shading correction circuit 2185 performs image processing using the following equation (1) to calibrate image data. The actual input data is actual document image data read by the scanner unit 22 or the CIS 231. The input image data value (I_out) is the document image data after shading correction. The actual input data (I_in) is data of an original image read by the scanner unit 22 or the CIS 231.

Input image data value (I_out) = 256 x (actual input data (I_in)-black reference value B (n)) ÷ (white reference value W (n)-black reference value B (n)) ... Formula (1)
For example, when the shading correction of the read image is performed by the shading correction unit 218, the failure detection unit 2112 performs abnormality detection and abnormal position detection of the LED group included in the LED array light source as the light source 222 included in the scanner unit 22. When the white reference value W (n) for shading correction is acquired by the scanner unit 22 at the time of shading correction, if any of the blocks A to E constituting the light source 222 is abnormal, the white reference value W (n) shows the distribution of sample data as shown in FIG. That is, among the blocks A to E, the irradiation area due to the failed block has the brightness data of the area falling due to insufficient light amount due to LED non-lighting (in FIG. The case where irradiation by the LED group of block C is not performed is shown). The failure detection unit 2112 obtains the sample data from the scanner unit 22 and compares the sample data with a predetermined value (threshold value A). Detects a block in which a lighting state, deterioration, or failure occurs. Here, the predetermined threshold A is a value (eg, luminance 200) that guarantees sufficient luminance so that the output image is not output as a black stripe or a white stripe. The failure detection unit 2112 stores the detected block name in a built-in memory.

  The document width calculation unit 2110 reads a document to be read that is placed on the contact glass 221 by the scanner unit 22 under the control of the control unit 2115 immediately before the document feeding unit 21 is closed during flatbed mode reading. Are read for one or more predetermined lines for document size detection, the main scanning direction is determined based on the determination result by the white color determination unit 214 for the document image read by the scanner unit 22. 8, the change point as shown in FIG. 8 where the pixel value of the read image changes from white to black is detected, and the distance from the first pixel position arranged first in the main scanning direction to the pixel position of the change point is determined. The document width in the main scanning direction of the document is calculated.

  The document size calculation unit 2111 includes a document width information storage unit 2141 and a document size detection unit 2143.

  The document width information storage unit 2141 stores document width information in the main scanning direction corresponding to each of a standard document size (specified document size) according to vertical and horizontal directions such as A size and B size. In the present embodiment, in order to detect the A-size vertical standard document size, it is sufficient to store the document width information in the main scanning direction corresponding to the A-size vertical standard document size.

  The document size detection unit 2143 reads the document size having the document width in the main scanning direction calculated by the document width calculation unit 2110 from the document width information storage unit 2141, and sets the read document size as the reading target. Is detected as the size of the original.

  Next, an image reading operation by the scanner unit 22 of the multifunction machine 1 will be described. FIG. 9 is a flowchart illustrating processing during an image reading operation by the scanner unit 22 of the multifunction machine 1. FIG. 10 is a diagram showing the relationship between the white reference value and the white reference threshold when the light source 222 is faulty. FIG. 11 is a diagram showing the positional relationship between the document placed on the contact glass and each block of the light source.

  When the copying operation is started in the multifunction device 1 based on an instruction from the user and shading correction is performed, the shading data of the white reference value W (n) and the black reference value B (n) is acquired by the scanner unit 22. Then (S1), the failure detection unit 2112 determines whether all the white reference values W (n) for the pixels arranged in the main scanning direction are equal to or greater than the threshold A (S2). That is, the failure detection unit 2112 detects whether or not a failure such as non-lighting has occurred in each of the blocks A to E of the LED group constituting the light source 222 based on the white reference value W (n).

  If the failure detection unit 2112 determines that the white reference values W (n) of the pixels arranged in the main scanning direction are all equal to or greater than the threshold A (YES in S2), the control unit 2115 performs a normal copy operation. Is executed (S15). That is, since the failure detection unit 2112 determines that no failure has occurred in each block of the LED group constituting the light source 222, a normal copy operation is performed.

  On the other hand, when the failure detection unit 2112 determines that there is an area indicating a pixel value having a value less than the threshold A among the white reference values W (n) of the pixels arranged in the main scanning direction (NO in S2). The display control unit 2114 causes the display unit 51 to display a message prompting the user to input an instruction as to whether or not to continue the copy operation (S3). In this embodiment, as shown in FIG. 2, each LED group of the light source 222 is connected to the drive circuit for each of a plurality of blocks, and thus a defect such as a non-lighting state occurs in one LED. In such a case, all the LEDs belonging to the block including the LED causing the malfunction are not lit, and the LEDs belonging to the block not including the LED causing the malfunction are kept lit. For this reason, as shown in FIG. 7, the brightness value of the white reference value W (n) falls due to insufficient light quantity due to LED non-lighting in the pixel value of the portion corresponding to the irradiation area of the failed block.

  After the message is displayed, when the user inputs an instruction not to continue the copy operation by operating the start button 55 or the like (NO in S4), the subsequent document image reading operation and the recording unit by the scanner unit 22 are performed. The image forming operation by 40 is not performed. The display control unit 2114 causes the display unit 51 to display a message indicating a serviceman call that prompts the user to request a repair to the maintenance work (S14).

  In addition, after the message is displayed, if the user inputs a copy operation continuation instruction by operating the start button 55 or the like (YES in S4), the display control unit 2114 displays the standard size document for the user. Is displayed on the display unit 51 (S5). Here, the reason for prompting the placement of the standard-size document is that any of the blocks A to E of the light source 222 is out of order, so that the free-size document is placed on the contact glass 221 and placed. This is because the width of the placed document cannot be calculated, and the document size cannot be calculated.

  After displaying the message in S3, the white reference threshold correction unit 215 performs correction to reduce the white reference threshold used by the white determination unit 214 to a value corresponding to 50% of the white reference value W (n) (S6). ). For example, when the block C of the light source 222 is out of order and the white reference value of the portion corresponding to the irradiation area by the block C is lower than the irradiation area by other blocks, as shown in FIG. The white reference threshold value correction unit 215 reduces the white reference threshold value to a value corresponding to 50% of the white reference value W (n). As a result, even when the white determination unit 214 determines a white image or a black image, even if it is an image of the irradiation area portion of the block C that is determined to be defective, and is a read image that indicates a reduced pixel value, Using the white reference threshold that takes into account the reduction in the amount of light, the read image is a white image (in other words, an image indicating that a document is present) or a black image (that is, a document is present). It is possible to determine whether the image is an image that does not exist.

  Then, the control unit 2115 causes the scanner unit 22 to read the image of the placed document in order to acquire document size detection data (S7). The control unit 2115 causes the scanner unit 22 to read the document with the light source 222 turned on. At this time, as described above, the control unit 2115 causes the scanner unit 22 to read an image of only one scanning line, and the pixel value of the pixel forming the scanned image for the one scanning line is used as the document size detection data. Alternatively, the control unit 2115 may cause the scanner unit 22 to read an image for a plurality of scanning lines, and the average value of the pixel values forming the read image for the plurality of scanning lines may be used as the document size detection data. Good.

  Thereafter, the document width calculation unit 2110 scans the document to be read placed on the contact glass 221 by the scanner unit 22 for a predetermined number of lines or lines for detecting the document size. At this time, based on the determination result by the white color determination unit 214 on the image of the document read by the scanner unit 22, a change point where the pixel value of the read image changes from white to black in the main scanning direction is detected, and main scanning is performed. The distance from the first pixel position arranged first in the direction to the pixel position of the change point is calculated as the document width in the main scanning direction of the document (S8).

  Subsequently, the document size detection unit 2143 reads the document size having the document width calculated by the document width calculation unit 2110 from the document width information storage unit 2141 and uses the read document size as the document to be read. Is detected as a document size (S9). In this embodiment, it is assumed that the document width information storage unit 2141 stores A-size portrait document size information, and the multifunction device 1 detects the A-size portrait document size.

  For example, as illustrated in FIG. 11, when a failure occurs in the block C of the blocks A to E of the light source 222, the change point is adjacent to the block C where the failure is detected and the block C. It appears as the pixel value of the pixel located at the boundary of block D. Here, since the change point is arranged at the boundary portion between the block C and the block D, the change point is affected by irradiation by the adjacent block D that is not in failure. As a result, the amount of light in the irradiation area of the failed block C is compensated, and the brightness of the image read in the irradiation area of the block in which the amount of light is reduced is easily secured. The accuracy of the document width calculation based on the is increased.

  Subsequently, the display control unit 2114 causes the display unit 51 to display the detected document size and a message prompting the user to input an instruction as to whether or not to continue the copy operation (S10).

  After the message is displayed, when a copy operation execution instruction is input again by the operation of the operation unit 5 by the user (YES in S11), the control unit 2115 includes a paper feed mechanism including a paper feed cassette 461, a manual feed tray 471, and the like. The size of the document fed by the above is set to the detected document size (S12). The control unit 2115 performs an image reading operation by the scanner unit 22 and an image forming operation by the recording unit 40 (S13). At this time, as in the normal copy operation, the shading correction by the shading correction circuit 2185 is performed using the white reference value stored in the white reference memory 2182 and the black reference value stored in the black reference memory 2181. Since this is performed on the image read in S13, an image with improved image quality is formed on the recording paper after the image formation by shading correction.

  If the user does not input a copy operation execution instruction after displaying the message in S12 (NO in S11), the subsequent document image reading operation by the scanner unit 22 and the image forming operation by the recording unit 40 are not performed. The control unit 2114 causes the display unit 51 to display a message indicating the surviving man call (S14).

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above embodiment, detection of A size vertical size has been described as an example, but the number of blocks of the light source 222 is increased, each block width is shortened, and the main scanning direction corresponding to each size of A size vertical Document width information for all document width information including document width information in the main scanning direction corresponding to each size of B size and each document width information in the main scanning direction of other sizes. The information storage unit 2141 stores the document width information in the main scanning direction corresponding to each of the A size vertical size, B size vertical size, and other standard document sizes, and the document is located near the boundary between the blocks. By arranging the size switching points, calculation of the document width in the main scanning direction for A size portrait, B size portrait, and other sizes, and consequently, document sizes of A size portrait, B size portrait, and other sizes are calculated. It becomes possible to do.

  Further, in the above embodiment, an example in which the document size switching point is arranged near the boundary between the blocks has been shown, but the document size switching point is not necessarily arranged near the boundary between the blocks, For example, even when the document size switching point is arranged near the center of the main scanning direction of each block, the irradiation of the adjacent blocks can be performed by making the width of each block in the main scanning direction shorter than in the above embodiment. If the document size switching point is arranged at the affected position, the detection of the width in the main scanning direction of the document to be read is detected by the white reference threshold reduction correction process at the time of failure detection by the failure detection unit 2112 described above. The document size can be detected.

DESCRIPTION OF SYMBOLS 1 Multifunctional device 2 Image reader 10 White reference board 22 Scanner part 229 CCD
40 Recording unit 51 Display unit 210 Image reading circuit 211 CPU
2110 Document width calculation unit 2111 Document size calculation unit 2112 Failure detection unit 2113 Determination unit 2114 Display control unit 2115 Control unit 214 White color determination unit 2141 Document width information storage unit 2143 Document size detection unit 215 White reference threshold correction unit 218 Shading correction unit 2182 White reference memory

Claims (4)

A transparent document table on which a document to be read is placed;
A plurality of LEDs arranged in the main scanning direction are connected to a drive circuit for each of a plurality of blocks arranged in the main scanning direction, and the original placed on the original table is irradiated by the light source to irradiate the original. An image reading unit having a photoelectric conversion element for reading an image;
A white reference member disposed at a position where image reading by the image reading unit is possible;
A white reference value storage unit that stores a white reference value acquired by the reading operation of the white reference member by the image reading unit;
A white determination unit that determines whether the image read by the image reading unit indicates white or black based on a predetermined white reference threshold;
A failure detection unit that detects whether or not a failure has occurred in the LED for each block based on a white reference value acquired by the reading operation of the white reference member by the image reading unit;
A white reference threshold correction unit that performs correction to reduce the white reference threshold by a predetermined value when a failure is detected in any of the blocks by the failure detection unit;
Based on the determination result for the read image of the image reading unit by the white determination unit based on the corrected white reference threshold, a change point at which the read image changes from white to black in the main scanning direction. A document width calculating unit that calculates a document width in the main scanning direction of the document to be read;
An image reading apparatus comprising: a document size calculation unit that calculates a standard document size having a document width calculated by the document width calculation unit.   2. The image according to claim 1, wherein the light source of the image reading unit is arranged as a document size switching point corresponding to a document width in the main scanning direction of a different standard document size in the vicinity of a boundary portion between the blocks. Reader.   The white reference threshold correction unit, when correcting the white reference threshold when a failure is detected in any of the blocks by the failure detection unit, the white reference threshold acquired by the image reading unit. The image reading apparatus according to claim 1, wherein the image reading apparatus corrects the value to be 50% of the reference value. An image reading apparatus according to any one of claims 1 to 3,
An image forming apparatus comprising: an image forming unit that forms an image based on a document image read by the image reading apparatus.

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