JP5984856B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus and an image forming apparatus capable of executing a shading correction process on read image data.

  In an image reading apparatus such as a scanner, image data is read by receiving light emitted from a light source and reflected by an original by a photoelectric conversion element. Here, there may be variations in the pixel density in the main scanning direction in the image data due to variations in the light emission characteristics of the light source or variations in the light receiving sensitivity of the photoelectric conversion elements. For this reason, the image reading apparatus is equipped with a shading correction circuit that corrects image data based on color reference data read from a color reference plate having a predetermined reference color.

  On the other hand, when executing print processing for print data in an image forming apparatus, a technique is known in which print processing based on reference data is executed first, and correction data used for color correction for print data is obtained from an output result. (See Patent Document 1).

JP-A-6-55779

  By the way, in the image reading apparatus, when the color reference data is read from the color reference plate, a circuit for setting the read image data as the color reference data is driven. However, the shading correction circuit and various image processings are driven. The circuit is not driven. On the other hand, during reading of image data from a document in the image reading apparatus, the shading correction circuit and various image processing circuits are driven. That is, either or both of the number and type of circuits to be driven are different between reading the color reference data and reading the image data of the document, and the color reference data and the image data of the document have a power load on the image reading apparatus. Read in different states. Therefore, there is a case where high accuracy cannot be obtained for shading correction only by correcting the image data based on the color reference data.

  An object of the present invention is to provide an image reading apparatus and an image forming apparatus capable of improving the accuracy of shading correction.

  An image reading apparatus according to one aspect of the present invention includes an image reading unit, a color reference data acquisition unit, a shading correction circuit, one or a plurality of image processing circuits, and a correction amount changing unit. The image reading unit reads image data from a document. The color reference data acquisition means reads color reference data from a color reference member having a predetermined reference color using the image reading means. The shading correction circuit corrects the image data read by the image reading unit based on the color reference data read by the color reference data acquisition unit. The one or more image processing circuits perform predetermined image processing on the image data read by the image reading unit. The correction amount changing means includes a circuit that is simultaneously driven during reading of the color reference data by the color reference data acquisition means, the shading correction circuit, and the image processing circuit of the shading correction circuit and the image processing circuit. The correction amount of the image data by the shading correction circuit is determined according to either or both of the circuit number difference and the circuit type difference from the circuit that is simultaneously driven during reading of the image data from the document by the image reading unit. change.

  An image forming apparatus according to another aspect of the present invention includes an image reading device and an image forming unit. The image forming unit can form an image based on image data read by the image reading device.

  According to the present invention, it is possible to improve the accuracy of shading correction.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram showing a circuit configuration of an image reading unit of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram showing an internal configuration of an ASIC of an image forming apparatus according to an embodiment of the present invention. FIG. 5 is a diagram showing a process of processing image data in the ASIC of the image forming apparatus according to the embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of an image forming apparatus 10 according to an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the image forming apparatus 10 includes an ADF 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, and a control unit 5. The image forming apparatus 10 is a multifunction device having a plurality of functions such as a printer function, a facsimile function, and a copy function, in addition to a scan function for reading image data from a document. The present invention can also be applied to image reading apparatuses or image forming apparatuses such as scanners, facsimile machines, and copiers.

  The image forming unit 3 performs an image forming process (printing process) based on image data read by the image reading unit 2 or image data input from an information processing apparatus such as an external personal computer. The image forming unit. Specifically, as shown in FIG. 1, the image forming unit 3 includes a photosensitive drum 31, a charging device 32, an exposure device (LSU) 33, a developing device 34, a transfer roller 35, a cleaning device 36, a fixing roller 37, A pressure roller 38 and a paper discharge tray 39 are provided. In the image forming unit 3, an image is formed on the paper supplied from the paper feed cassette 41 that can be attached to and detached from the paper feed unit 4 according to the following procedure, and the paper after the image formation is discharged to the paper discharge tray 39. Is done.

  First, the photosensitive drum 31 is uniformly charged to a predetermined potential by the charging device 32. Next, the exposure device 33 irradiates the surface of the photosensitive drum 31 with light based on image data. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 31. The electrostatic latent image on the photosensitive drum 31 is developed (visualized) as a toner image by the developing device 34. The developing device 34 is supplied with toner (developer) from a toner container 34 </ b> A that can be attached to and detached from the image forming unit 3. Subsequently, the toner image formed on the photosensitive drum 31 is transferred onto a sheet by the transfer roller 35. Thereafter, the toner image transferred to the sheet is heated and fixed by the fixing roller 37 when the sheet passes between the fixing roller 37 and the pressure roller 38. The toner remaining on the surface of the photosensitive drum 31 is removed by the cleaning device 36.

  The control unit 5 includes control devices such as a CPU, ROM, RAM, and EEPROM (not shown). The CPU is a processor that executes various arithmetic processes. The ROM is a non-volatile storage unit in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile storage unit, and the EEPROM is a non-volatile storage unit. The RAM and the EEPROM are used as a temporary storage memory (working area) for various processes executed by the CPU. Then, the control unit 5 comprehensively controls the image forming apparatus 10 by executing various control programs stored in advance in the ROM using the CPU. The control unit 5 may be an electronic circuit such as an integrated circuit (ASIC), and is provided separately from a main control unit that controls the image forming apparatus 10 in an integrated manner. It may be.

  As shown in FIG. 1, the ADF 1 is an automatic document feeder that includes a document setting unit 11, a plurality of conveyance rollers 12, a document pressing unit 13, and a paper discharge unit 14. In the ADF 1, each of the transport rollers 12 is driven by a motor (not shown) so that the document placed on the document setting unit 11 passes through the image data reading position by the image reading unit 2. It is conveyed to the paper discharge unit 14. As a result, the image reading unit 2 can read image data from a document conveyed by the ADF 1.

  Further, the document presser 13 is provided at a position above the reading position on a later-described transport reading surface 212 of the image reading unit 2 at an interval through which the document can pass. The document retainer 13 is elongated in the main scanning direction (the depth direction in FIG. 1), and a white sheet 13A is attached as a color reference member to the lower surface (the surface on the side of the conveyance reading surface 212). It has been. In the image forming apparatus 10, the image data of the white sheet 13 </ b> A is read as color reference data used in shading correction described later.

  As shown in FIG. 1, the image reading unit 2 includes a document table 21, a reading unit 22, mirrors 23 to 24, an optical lens 25, and a CCD (Charge Coupled Device) 26.

  The document table 21 is provided on the upper surface of the image reading unit 2, and includes a document placement surface 211 and a conveyance reading surface 212. The document placement surface 211 is a translucent contact glass on which a document to be read of image data is placed. On the document placement surface 211, documents of various sizes are placed according to a predetermined placement reference position. The conveyance reading surface 212 is a conveyance reading glass that transmits light emitted from the reading unit 22 to a document conveyed by the ADF 1.

  The reading unit 22 includes a light source 221 and a mirror 222, and is configured to be movable in the sub-scanning direction (left and right direction in FIG. 1) by a moving mechanism (not shown) using a driving unit such as a stepping motor. When the reading unit 22 is moved in the sub-scanning direction by the driving unit, the light emitted from the light source 221 onto the document table 21 is scanned in the sub-scanning direction.

  The light source 221 includes a large number of white LEDs arranged along the main scanning direction (the depth direction in FIG. 1). The light source 221 passes through the document placement surface 211 or the conveyance reading surface 212 of the document table 21 and irradiates the document with white light for one line in the main scanning direction. The irradiation position of the light from the light source 221 is the reading position of the image data by the image reading unit 2, and the reading position moves in the sub-scanning direction as the reading unit 22 moves in the sub-scanning direction. Specifically, the reading unit 22 is moved to a position where the light of the light source 221 passes through the document placement surface 211 when reading image data from the document placed on the document placement surface 211. . Further, when reading image data from a document conveyed by the ADF 1, the reading unit 22 is moved to a position where the light from the light source 221 passes through the conveyance reading surface 212.

  The mirror 222 reflects the light emitted from the light source 221 and reflected by the surface of the document at the reading position on the document table 21 toward the mirror 23. The light reflected by the mirror 222 is guided to the optical lens 25 by the mirrors 23 to 24. The optical lens 25 collects the light incident from the mirror 24 and makes it incident on the CCD 26.

  The CCD 26 is an image sensor having a photoelectric conversion element that outputs an analog signal (voltage) corresponding to the amount of reflected light from a received document. The analog signal output from the CCD 26 is input to an AFE 27 described later.

  Next, the circuit configuration of the image reading unit 2 will be described with reference to FIG. As shown in FIG. 2, the image reading unit 2 further includes an AFE 27, an ASIC 28, and an SDRAM 29 in addition to the above configuration.

  The AFE 27 is a signal processing unit that executes processing based on the analog signal output from the CCD 26. Specifically, the AFE 27 is an analog front-end circuit including electronic circuits such as a CDS 271, an AGC 272, an ADC 273, and a DSP 274, as shown in FIG.

  The CDS 271 executes noise removal processing based on a correlated double sampling method on the analog signal input from the CCD 26. For example, in the CDS 271, noise removal processing for removing low-frequency fluctuations is executed by a bit clamp method in which an analog signal output from the CCD 26 is clamped at a bit period. The analog signal that has been subjected to noise removal processing by the CDS 271 is input to the AGC 272.

  The AGC 272 is a gain control amplifier that amplifies the analog image data input from the CDS 271 according to a preset amplification factor (gain). The analog image data amplified by the AGC 272 is input to the ADC 273.

  The ADC 273 is an analog-digital converter that converts the analog signal input from the AGC 272 into a digital signal (hereinafter referred to as “image data”). The image data output from the ADC 273 is input to the DSP 274.

  The DSP 274 executes signal conversion processing for converting the RGB format image data input from the ADC 273 into the CMYK format image data. The image data after the signal conversion processing by the DSP 274 is input to the ASIC 28.

  In this way, the light emitted from the LED light source 221 and reflected by the document enters the CCD 26 via the mirror 222, the mirror 23, the mirror 24, and the optical lens 25, and depends on the amount of light. Converted into the analog signal. The analog signal output from the CCD 26 is converted into the image data by the ADC 273 of the AFE 27, whereby the image data of the document is read. Here, the reading unit 22 including the LED light source 221 and the mirror 222, the mirror 23, the mirror 24, the optical lens 25, the CCD 26, and the AFE 27 are examples of image reading means.

  The ASIC 28 is a signal processor that performs various types of image processing on the image data input from the AFE 27. Then, the image data after the image processing by the ASIC 28 is input to the SDRAM 29 and recorded. Details of the ASIC 28 will be described later.

  The SDRAM 29 is storage means used as an image memory in which the image data is stored. Reading and writing data to and from the SDRAM 29 is controlled by a DMAC (Direct Memory Access Controller) not shown. A storage unit such as a hard disk may be provided in place of the SDRAM 29.

  Next, the internal configuration of the ASIC 28 will be described with reference to FIG. As shown in FIG. 3, the ASIC 28 includes a first image processing circuit 281, a color reference data storage unit 282, a shading correction circuit 283, a second image processing circuit 284, a second image processing circuit 285, and a second image processing circuit 286. , And a correction amount changing circuit 287.

  The first image processing circuit 281 is a first image processing circuit that executes predetermined image processing on the image data read by the image reading unit 2. Specifically, in the image forming apparatus 10, the control unit 5 reads the image data from the white sheet 13 </ b> A using the image reading unit 2. The first image processing circuit 281 is used for the shading correction executed by the shading correction circuit 283 based on the image data corresponding to the white sheet 13A read by the image reading unit 2. Set color reference data. The control unit 5 acquires the color reference data from the white sheet 13A, for example, when the image forming apparatus 10 is powered on or returned from the sleep state. Here, the control unit 5 that reads the image data from the white sheet 13A using the image reading unit 2 is an example of a color reference data acquisition unit.

  More specifically, the control unit 5 reads the image data for one line from the white sheet 13 </ b> A using the image reading unit 2. The first image processing circuit 281 sets the image data for one line read by the control unit 5 as the color reference data. That is, in the image forming apparatus 10, the color reference data is data for one line of pixels indicating white. For example, when the density of the pixel of the image data is expressed by 256 gradations, and the density value of the pixel indicating black is 255 and the density value of the pixel indicating white is 0, the color The density value of the reference data is a value such as 7-12. The control unit 5 reads the image data for a plurality of lines from the white sheet 13A using the image reading unit 2, and the first image processing circuit 281 reads the image data read by the control unit 5. The average value at each pixel position may be calculated and set as the color reference data.

  The color reference data storage unit 282 is a storage unit such as an SRAM that stores the color reference data set by the first image processing circuit 281.

  The shading correction circuit 283 performs the shading correction for correcting the image data read from the document by the image reading unit 2 based on the color reference data stored in the color reference data storage unit 282. In the image reading unit 2, variations in the light emission characteristics of the LED light source 221 in the main scanning direction or variations in the light receiving sensitivity of the CCD 26 may occur. In this case, when an image having the same density (for example, a white image) is read by the image reading unit 2, there is a possibility that a reading error occurs in the image data of the pixels in the main scanning direction. The shading correction is image processing for correcting the reading error in the image reading unit 2 and suppressing density variation.

  For example, the shading correction circuit 283 performs the shading correction for each pixel of the read image data based on the following equation (1).

  Density value of image data after correction = number of gradations × (density value of read image data−density value of color reference data) / (density value of black level−density value of color reference data) (1)

  Then, the image data processed by the shading correction circuit 283 is input to the second image processing circuit 284. Here, the density value of the black level in the equation (1) is the density value of the pixel indicating black. The black level density value may be a predetermined fixed value or output from the CCD 26 and the AFE 27 when the ADF 1 is closed and the LED light source 221 is turned off. It may be set based on

  The second image processing circuit 284, the second image processing circuit 285, and the second image processing circuit 286 perform a second image process that performs predetermined image processing on the image data read by the image reading unit 2. An image processing circuit. The first image processing circuit 281, the second image processing circuit 284, the second image processing circuit 285, and the second image processing circuit 286 are examples of the image processing circuit in the present invention. When collectively referred to, it is referred to as an image processing circuit 280.

  Specifically, the second image processing circuit 284, the second image processing circuit 285, and the second image processing circuit 286 perform predetermined image processing on the image data corrected by the shading correction circuit 283. And output. Here, the image processing is various image processing such as gamma correction processing, rotation processing, and enlargement / reduction processing. For example, the second image processing circuit 284 executes the gamma correction process, and the second image processing circuit 285 executes the rotation process. The second image processing circuit 286 executes the enlargement / reduction process. The number of image processing circuits provided in the ASIC 28 that can execute the image processing may be one or more.

  Hereinafter, the flow of processing on the image data read by the image reading unit 2 and input to the ASIC 28 will be described with reference to FIG. The main scanning synchronization signal in FIG. 4 is a signal corresponding to the reading cycle of image data for one line by the image reading unit 2. Each main scanning effective section signal in FIG. 4 is a signal for controlling the driving of each image processing circuit in the ASIC 28.

  A series of processing in the ASIC 28 described here is repeatedly executed for each line of the image data. Here, the input data D1 shown in FIG. 4 indicates image data for one line input to the shading correction circuit 283. Similarly, the input data D2, D3, and D4 shown in FIG. 4 are for one line input to the second image processing circuit 284, the second image processing circuit 285, and the second image processing circuit 286, respectively. Image data is shown. 4 indicates the color reference data used in the shading correction circuit 283.

  First, the image data input to the ASIC 28 is input to the shading correction circuit 283 sequentially from the first pixel. The shading correction circuit 283 performs the shading correction on the input data D1 that has been input. Here, the shading correction circuit 283 performs the shading correction based on the color reference data stored in the color reference data storage unit 282. Then, after the elapse of time T1 shown in FIG. 4, the shading correction circuit 283 sequentially outputs the input data D2, which is the image data after the shading correction, from the top pixel, and the second image processing circuit 284. To enter. That is, the time T1 indicates a processing time for one pixel of the image data in the shading correction circuit 283. Note that the time T1 is a time corresponding to about several cycles to about a dozen cycles when processing is performed in one cycle per pixel in the ASIC 28, for example.

  Next, the second image processing circuit 284 performs the gamma correction on the input data D2 input from the shading correction circuit 283. Then, after the elapse of time T2 shown in FIG. 4, the second image processing circuit 284 sequentially outputs the input data D3, which is the image data after the gamma correction, from the top pixel, and performs the second image processing. Input to the circuit 285. That is, the time T2 indicates the processing time for one pixel of the image data in the second image processing circuit 284. Here, in the ASIC 28, the shading correction circuit 283 and the second image processing circuit 284 operate simultaneously during the time T2.

  Subsequently, the second image processing circuit 285 performs the rotation process on the input data D3 input from the second image processing circuit 284. Then, after the elapse of time T3 shown in FIG. 4, the second image processing circuit 285 sequentially outputs the input data D4, which is the image data after the rotation processing, from the top pixel, and performs the second image processing. Input to circuit 286. That is, the time T3 indicates the processing time for one pixel of the image data in the second image processing circuit 285. Here, in the ASIC 28, the shading correction circuit 283, the second image processing circuit 284, and the second image processing circuit 285 operate simultaneously during the time T3.

  Then, the second image processing circuit 286 performs the enlargement / reduction processing on the input data D4 input from the second image processing circuit 285. Then, the second image processing circuit 286 sequentially outputs the image data after the enlargement / reduction processing as output image data from the top pixel, and inputs it to the SDRAM 29. Here, in the ASIC 28, the shading correction circuit 283, the second image processing circuit 284, the second image processing circuit 285, and the second image processing circuit 286 operate simultaneously during the time T4.

  Thereafter, when the last pixel of the input data D4 is output from the second image processing circuit 286, the image data for the next one line is input to the ASIC 28, and the processing cycle described above is repeated. Will be.

  Incidentally, in the image forming apparatus 10, when the color reference data is read from the white sheet 13A by the control unit 5, the first image processing circuit 281 is driven, but the shading correction circuit 283, The second image processing circuits 284 to 286 are not driven. On the other hand, the first image processing circuit 281 is not driven while the image forming apparatus 10 is reading the image data from the original, but the shading correction circuit 283 and the second image are not driven as shown in FIG. The processing circuits 284 to 286 are sequentially driven. That is, at the time of reading the color reference data and at the time of reading the image data of the original, either or both of the number and type of circuits to be driven are different, and the color reference data and the image data of the original are Reading is performed with different power loads in the image forming apparatus 10. Therefore, there is a case where high accuracy cannot be obtained for the shading correction only by correcting the image data based on the color reference data. On the other hand, in the image forming apparatus 10, the accuracy of the shading correction is improved by the correction amount changing circuit 287 provided in the ASIC 28.

  Next, the correction amount changing circuit 287 will be described. The correction amount changing circuit 287 includes a circuit that is simultaneously driven during reading of the color reference data by the control unit 5 among the shading correction circuit 283 and the image processing circuit 280, and the shading correction circuit 283 and the image processing circuit. The correction amount of the image data by the shading correction circuit 283 is changed in accordance with the difference in the number of circuits with the circuit simultaneously driven during reading of the image data from the original by the image reading unit 2 in 280. The correction amount changing circuit 287 is an example of a correction amount changing unit.

  That is, in the image forming apparatus 10, when the image data is read from the document, more image processing circuits 280 are driven simultaneously than when the color reference data is read. The power load increases and the output of the image reading unit 2 decreases. Therefore, an output is performed between the image data output from the image reading unit 2 when reading the image data of the original and the image data output from the image reading unit 2 when reading the color reference data. A difference occurs in the density of the image data. The correction amount changing circuit 287 changes the correction amount of the image data by the shading correction circuit 283 in accordance with the difference in the number of circuits, thereby affecting the shading correction due to a decrease in the output of the image reading unit 2. It is suppressed.

  Here, in the image forming apparatus 10, during reading of the color reference data by the control unit 5, the first image processing circuit 281 of the image processing circuit 280 is driven, and the original by the image reading unit 2 is read. During the reading of the image data, the second image processing circuits 284 to 286 out of the shading correction circuit 283 and the image processing circuit 280 are driven. When the image reading unit 2 reads the image data from the document, the image data input to the ASIC 28 is processed by the shading correction circuit 283 and then the second image processing circuits 284 to 286. Is input. That is, in the image forming apparatus 10, the circuit number difference is the number of circuits that are driven simultaneously among the second image processing circuits 284 to 286 when the image reading unit 2 reads the image data from the document. means.

  Further, in the image forming apparatus 10, as shown in FIG. 4, a circuit that is simultaneously driven out of the shading correction circuit 283 and the image processing circuit 280 performs the image for one line from the original by the image reading unit 2. Changes while reading data. The correction amount changing circuit 287 can change the color reference data in accordance with a change in the circuit number difference during the reading of the image data for one line from the original by the image reading unit 2. Therefore, the image forming apparatus 10 can improve the accuracy of the shading correction from the first line of the image data read by the image reading unit 2.

  Specifically, the correction amount changing circuit 287 changes the correction amount of the image data by changing the color reference data in accordance with the circuit number difference. For example, the correction amount change circuit 287 may increase the change amount of the color reference data in proportion to the increase in the circuit number difference. Then, when the difference in the number of circuits increases and the density of the image data read by the image reading unit 2 decreases, the correction amount changing circuit 287 causes the color reference data to decrease in density in the shading correction. Make changes. For example, if the density value of a pixel indicating black is 255 and the density value of a pixel indicating white is 0, and the density value of the color reference data is 10, the density value of the color reference data is 8 It will be reduced to such a value. Further, when the difference in the number of circuits becomes large and the density of the image data read by the image reading unit 2 becomes dark, the correction amount changing circuit 287 causes the color reference data to be dark in the shading correction. Make changes. For example, when the density value of a pixel indicating black is 0 and the density value of a pixel indicating white is 255, and the density value of the color reference data is 245, the density value of the color reference data is set to 243. It will be reduced to such a value. Accordingly, the density of the image data output from the image reading unit 2 in a state where the power load of the image forming apparatus 10 is large is added to the color reference data read in a state where the power load of the image forming apparatus 10 is small. It is possible to reflect the effect of the decrease in value.

  As shown in FIG. 4, the number of circuits that are driven simultaneously among the second image processing circuits 284 to 286 during the reading of the image data from the original by the image reading unit 2 is the shading correction circuit 283. The second image processing circuit 284 and the second image processing circuit 285 increase when the processing times T1, T2, and T3 have elapsed. Therefore, when the content of the image reading process is specified, the number of circuits that are driven simultaneously among the second image processing circuits 284 to 286 during the reading of the image data from the document by the image reading unit 2. It will also be specified when the increase.

  Therefore, in the image forming apparatus 10, the circuit number difference corresponding to each content of the image reading processing executed in the image forming apparatus 10 is stored in advance in a storage unit such as the EEPROM of the control unit 5. . Here, the content of the image reading process is the content and order of the image processing executed by the ASIC 28. Specifically, the EEPROM stores a processing time for each of the shading correction circuit 283 and the image processing circuit 280 for executing the image processing. Then, the control unit 5 sets the processing time for each image processing from the EEPROM in the register inside the correction amount changing circuit 287 according to the contents of the image reading processing, so that the correction amount changing circuit 287 is It is possible to change the color reference data in accordance with an increase in the number of simultaneously driven circuits among the second image processing circuits 284 to 286. The EEPROM stores the processing time for each image processing and the change amount of the color reference data corresponding to the difference in the number of circuits, and the control unit 5 stores the processing time for each image processing together with the processing time for the image processing. The change amount of the color reference data corresponding to the difference in the number of circuits may be set in a register in the correction amount change circuit 287 together. Thereby, the correction amount changing circuit 287 does not need to detect when the number of simultaneously driven circuits among the second image processing circuits 284 to 286 is increased, and the processing content of the correction amount changing circuit 287 is simplified. It becomes.

  As described above, in the image forming apparatus 10, the correction amount changing circuit 287 drives the shading correction circuit 283 and the image processing circuit 280 simultaneously during reading of the color reference data by the control unit 5. The shading correction circuit 283 and the image processing circuit 280 are controlled by the shading correction circuit 283 in accordance with a difference in the number of circuits from the image reading unit 2 and a circuit that is simultaneously driven during reading of the image data from the document. The correction amount of the image data is changed. Therefore, it is possible to increase the accuracy of shading correction.

[Other Embodiments]
Unlike the embodiment described above, the correction amount changing circuit 287 includes a circuit that is simultaneously driven during reading of the color reference data by the control unit 5 in the shading correction circuit 283 and the image processing circuit 280. The shading correction circuit 283 and the image processing circuit 280 are controlled by the shading correction circuit 283 according to a circuit type difference between the image reading unit 2 and a circuit that is simultaneously driven while the image reading unit 2 reads the image data from the document. It is conceivable to change the correction amount of the image data. It is also conceivable that the correction amount changing circuit 287 changes the correction amount of the image data by the shading correction circuit 283 in accordance with both the circuit number difference and the circuit type difference. Thus, the difference in power consumption due to the difference in circuit type can be reflected in the change in the correction amount of the image data by the shading correction circuit 283.

  Further, it is conceivable that the correction amount change circuit 283 increases the change amount of the color reference data as the power consumption difference due to one or both of the circuit number difference and the circuit type difference increases. Thereby, the influence on the shading correction due to the decrease in the output of the image reading unit 2 is suppressed with higher accuracy.

  Further, in the present embodiment, the case where the correction amount of the image data by the shading correction circuit 283 is changed by changing the color reference data by the correction amount changing circuit 287 has been described. On the other hand, the method of changing the correction amount of the image data by the shading correction circuit 283 is not limited to this. For example, in place of the correction amount changing circuit 287, the image data after the shading correction circuit 283 corrects based on the color reference data is used as one or both of the circuit number difference and the circuit type difference. Further correction may be considered in response. In this case, the shading correction circuit 283 is an example of a correction amount changing unit.

1: ADF
13: Document holder 13A: White sheet 2: Image reading unit 21: Document table 22: Reading unit 221: Light source 222: Mirror 23: Mirror 24: Mirror 25: Optical lens 26: CCD
27: AFE
271: CDS
272: AGC
273: ADC
274: DSP
28: ASIC
281: First image processing circuit 282: Color reference data storage unit 283: Shading correction circuit 284: Second image processing circuit 285: Second image processing circuit 286: Second image processing circuit 287: Correction amount changing circuit 29: SDRAM
3: Image forming unit 4: Paper feeding unit 5: Control unit 10: Image forming apparatus

Claims (7)

Image reading means for reading image data from a document;
Color reference data obtaining means for reading color reference data from a color reference member having a predetermined reference color using the image reading means;
A shading correction circuit that corrects the image data read by the image reading unit based on the color reference data read by the color reference data acquisition unit;
One or more image processing circuits for executing predetermined image processing on the image data read by the image reading unit;
Of the shading correction circuit and the image processing circuit, a circuit that is simultaneously driven during the reading of the color reference data by the color reference data acquisition unit, and from the original by the image reading unit of the shading correction circuit and the image processing circuit. Correction amount changing means for changing the correction amount of the image data by the shading correction circuit according to one or both of a circuit number difference and a circuit type difference from a circuit driven simultaneously during reading of the image data ,
An image reading apparatus comprising:   The image according to claim 1, wherein the correction amount changing unit changes the correction amount of the image data by changing the color reference data according to one or both of the circuit number difference and the circuit type difference. Reader. A circuit that is driven simultaneously among the shading correction circuit and the image processing circuit changes during the reading of the image data for one line from the original by the image reading unit,
The correction amount changing unit is configured to change the color reference according to a change in one or both of the circuit number difference and the circuit type difference during reading of the image data for one line from the original by the image reading unit. The image reading apparatus according to claim 2, wherein the data can be changed.   4. The image according to claim 2, wherein the correction amount changing unit increases the change amount of the color reference data as a power consumption difference caused by one or both of the circuit number difference and the circuit type difference increases. Reader. A storage unit that stores in advance either or both of the circuit number difference and the circuit type difference corresponding to each content of the image reading process executed by the image reading apparatus;
The correction amount changing unit acquires one or both of the circuit number difference and the circuit type difference from the storage unit according to the content of the image reading process executed by the image reading apparatus. 5. The image reading apparatus according to any one of 4 above. In the plurality of image processing circuits, a first image processing circuit that sets the color reference data based on the image data read by the image reading unit, and the image data that has been corrected by the shading correction circuit are set in advance. One or a plurality of second image processing circuits for performing and outputting the processed image processing,
During the reading of the color reference data by the color reference data acquisition means, the first image processing circuit of the image processing circuit is driven, and during the reading of the image data from the document by the image reading means, the shading correction is performed. The image reading apparatus according to claim 1, wherein the second image processing circuit is driven among the circuit and the image processing circuit.   An image forming apparatus comprising: the image reading apparatus according to claim 1; and an image forming unit capable of forming an image based on image data read by the image reading apparatus.

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