JP2006303710A - Reading apparatus and control method of reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of reducing a memory capacity required for shading correction while suppressing deterioration in read data. <P>SOLUTION: A register 313 deletes higher-order 4 bits of digital data corresponding to each CCD outputted from an analog processing means when a light source is turned out, the resulting data are stored in a black shading memory 321, a register 315 deletes lower-order 4 bits of the digital data corresponding to each CCD outputted from the analog processing means while each CCD is moved to a read position of a white reference board, the resulting data are stored in a white shading memory 323, in executing black shading correction, a register 309 adds 4 bits to the higher-order of the data read from the memory 321, and in executing white shading correction, a register 311 adds 4 bits to the lower-order of the data read from the memory 323. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reader and a method for controlling the reader, and more particularly to processing of data used for shading correction in the reader.

  2. Description of the Related Art Conventionally, a reading device (scanner) samples an analog signal output from a CCD, which is an image sensor, performs offset adjustment, gain adjustment, and the like, and then converts it into digital data by an A / D converter. After conversion to digital data, image data is obtained by performing shading correction in order to correct variations in each pixel of the CCD and the light source (see, for example, Patent Document 1).

There are two types of shading correction: black shading correction for correcting the offset for each pixel and white shading for correcting the gain for each pixel. Both of these corrections require that the offset and gain be stored in the memory for each pixel. is there.
JP-A-5-143722

  However, when shading correction is performed with the conventional configuration, the following problems occur.

  In recent readers, the number of read pixels is greatly increased in order to improve the resolution of the CCD, so that the memory capacity required for shading correction is significantly increased. In general, the reader is used by connecting to a computer such as a PC. However, in order to improve not only the resolution but also the quality of an image transmitted to the PC, the number of bits of each pixel is changed from 8 bits to 16 bits. The number of bits is increasing, and the memory capacity required for shading correction is further increased.

  In general, an image to be transmitted to a PC is basically provided with a non-linear characteristic (gamma characteristic) in accordance with a human visual sensitivity characteristic. Usually, since the non-linear gamma value is less than 1, a black image with a small luminance value requires a larger number of bits than a white image. However, in the conventional shading correction, the correction is performed with the number of bits according to the output of the A / D converter without considering it.

  The present invention has been made in view of the above situation, and an object of the present invention is to reduce memory capacity required for shading correction while suppressing deterioration of read data.

A reading apparatus as one aspect of the present invention that achieves the above object includes a light source that irradiates a document,
Reading means having a plurality of image sensors arranged in a predetermined direction;
Analog processing means for performing a predetermined process on the analog signal output from each image sensor and then converting it to digital data and outputting it,
First correction data acquisition means for deleting a plurality of upper or lower bits of digital data corresponding to each image sensor output from the analog processing means and storing them in a first memory with the light source turned off. When,
With the reading unit moved to the reading position of the white reference plate, the lower plurality of bits of the digital data corresponding to each image sensor output from the analog processing unit are deleted and stored in the second memory. Two correction data acquisition means;
Black shading correction means for correcting variations in output values of the respective image pickup elements in a state where the light source is turned off based on data stored in the first memory;
White shading correction means for correcting variations in the gain of each image sensor and the amount of light from the light source based on data stored in the second memory.

  With such a configuration, as black shading correction data, correction data is stored in the first memory in a state where a plurality of upper or lower bits are deleted, and as white shading correction data, data that has substantially no influence on image quality. The correction data is stored in the second memory in a state where is deleted. When using correction data, it is sufficient to add 0 to the number of deleted bits.

  Therefore, it is possible to secure sufficient bit accuracy for the black shading correction, and to reduce the capacity of the memory for storing the respective shading correction data while suppressing the deterioration of the image quality to the extent that there is no practical problem for the white shading correction. it can.

  The black shading correction means performs correction using data obtained by adding 0 to the upper or lower bits of the data stored in the first memory, and the white shading correction means performs the data stored in the second memory. It is preferable to perform correction using data in which 0 is added to the lower-order multiple bits.

  The number of upper bits and the number of lower bits may be equal, for example, the number of bits may be four.

  The analog processing means may include an offset adjusting means for adjusting the offset value of the entire reading means, a gain adjusting means for adjusting the gain of the entire reading means, and an A / D converter.

  When the scanner mode is designated, the first correction data acquisition unit deletes the upper multiple bits of the digital data corresponding to each image sensor output from the analog processing unit, and stores them in the first memory. When the copy mode is designated, the lower plurality of bits of the digital data corresponding to each image sensor output from the analog processing means may be deleted and stored in the first memory.

In addition, the above-mentioned purpose is to perform a predetermined process on the analog signal output from each image sensor, and then convert it to digital data and output it,
A first correction data acquisition step of deleting a plurality of upper or lower bits of digital data corresponding to each image sensor output in the analog processing step and storing them in a first memory with the light source turned off When,
With the reading unit moved to the reading position of the white reference plate, the lower plurality of bits of the digital data corresponding to each image sensor output in the analog processing step are deleted and stored in the second memory. 2 correction data acquisition step;
Based on the data stored in the first memory, a black shading correction step for correcting variations in the output values of the imaging elements in a state where the light source is turned off,
This can also be achieved by a control method for a reading apparatus comprising a white shading correction step of correcting variations in the gain of each image sensor and the amount of light from the light source based on data stored in the second memory.

  The above object can also be achieved by a computer program for realizing the above-described reading apparatus control method by a computer apparatus, and a storage medium storing the computer program.

  According to the present invention, sufficient black accuracy is ensured for black shading correction, and deterioration of image quality for white shading correction is suppressed to a level that does not cause a problem in practice, and the capacity of a memory for storing each shading correction data is increased. Can be reduced.

  Also, optimum results can be obtained in each mode by changing the processing method between a scan mode that requires correction accuracy and a copy mode that requires improvement in correction processing speed.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the components described in the following embodiments are merely examples, and are not intended to limit the scope of the present invention only to them.

  FIG. 1 is a block diagram illustrating a control configuration of a multifunction machine having a scanner function, a print function, and a copy function as an embodiment of the present invention.

  In the figure, reference numeral 101 denotes a CPU that controls the entire multifunction peripheral. 103 is a CCD device as an image sensor for reading image data, 105 is an analog processing unit that amplifies and samples an analog image signal output from the CCD, then performs A / D conversion and outputs digital image data, and 107 is an analog This is a read image processing unit that performs image processing such as edge enhancement and color conversion on the digital image data output from the processing unit 105. These 103, 105, and 107 realize a scanner function for reading a document. .

  In the multifunction machine of this embodiment, a scanner function is realized by scanning a line-type CCD (line sensor) 103 and reading reflected light while irradiating a document with a light source.

  An operation control unit 109 has a key input unit and a display unit. The operation control unit 111 functions as a user interface for the user to instruct operations such as mode selection and operation start such as a copy mode and a scan mode. 111 denotes read image data and recording An image memory 113 temporarily stores image data to be transmitted. A PC i / f (interface) 113 transmits image data read to a connected PC during scanning, and receives image data and control data from the connected PC during printing. It is.

  Reference numeral 115 denotes a recording image processing unit that executes a scaling process or the like that changes the size of the image data to be recorded or matches the print head specifications. 117 prints the image data output from the recording image processing unit 115. The recording head control unit converts the head into a format corresponding to the head and generates a head drive signal. Reference numeral 119 denotes a print head that records on a recording sheet according to an ink jet method.

  FIG. 2 is a block diagram showing in more detail a part of the analog processing unit 105 and the read image processing unit 107 in the control configuration shown in FIG.

  A sample and hold circuit 201 samples an analog image signal read by a CCD, and 203 adds an offset voltage to the sampled analog signal to adjust the zero voltage of the A / D converter 207 in the subsequent stage. An offset adjustment unit. Reference numeral 205 denotes a variable GAIN adjustment unit that performs GAIN adjustment on the signal output from the offset adjustment unit 203 so as to be within the reference voltage of the A / D converter 207 in the subsequent stage. Reference numeral 207 denotes an A / D converter that converts an analog signal output from the variable GAIN adjustment unit 205 into a digital value.

  A shading correction unit 209 forms a part of the read image processing unit 107. The shading correction unit 209 is composed of two blocks, 219 is a black shading correction unit that corrects offset variation for each pixel, and 211 is white shading that corrects gain variation and light source variation for each pixel. It is a correction unit.

  When actually reading an image, after setting appropriate values as adjustment values of the offset adjustment unit 203 and the variable GAIN adjustment unit 205 by the CPU, the black and white shading correction data for the shading correction unit 209 is acquired. , Controlled to start reading the image.

  FIG. 3 is a block diagram showing the configuration of the shading correction unit 209 in FIG. 2 in more detail.

  301 is a subtractor used for black shading correction calculation, 303 is a 0 clamp circuit that clamps with zero so that the result of black shading calculation is not negative, and 305 is a divider used for white shading calculation. , 306 is a clamp circuit that clamps at a predetermined value when overflowing by division, and 307 is a subtracter that subtracts black shading correction data from white shading correction data to calculate input data to the divider.

  Next, in order to match the bit width of the digital image data output from the A / D converter 207 with the bit width of the black shading correction data read from the black shading memory 321, 309 sets the upper bit or the lower bit. This register adds 0 data. In this embodiment, data “0000” is added with the difference in bit width between the two as 4 bits.

  Here, the register 309 switches the bit position to which the data “0000” is added depending on whether the mode specified by the mode selection signal is the copy mode or the scan mode. In the present embodiment, “0000” is added to the upper bits in the scan mode, and “0000” is added to the lower bits in the copy mode. The mode selection signal may be output when the user selects the scanner mode or the copy mode from an operation unit (not shown) provided in the reading apparatus. Furthermore, a mode selection signal may be output to the register 309 when a scan instruction is issued from a PC connected to the PCi / f 113.

  Similarly, 311 applies white shading correction data to match the bit width of digital image data output from the A / D converter 207 and the bit width of white shading correction data read from the white shading memory 323. This register adds “0000” to the lower 4 bits.

  Reference numerals 321 and 323 denote memories for storing black shading correction and white shading correction data used at the time of correction processing, respectively storing white / black shading correction data for each pixel.

  Reference numerals 317 and 319 denote memory i / f for reading / writing black shading correction and white shading correction data with respect to the black shading memory 321 and the white shading memory 323, respectively.

  Also, 313 deletes the lower 4 bits or the upper 4 bits in order to match the bit width of the digital data output from the A / D converter 207 with the bit width of the black shading memory 321 when storing the black shading correction data. The register 315 deletes the lower 4 bits in order to match the bit width of the digital data output from the A / D converter 207 with the bit width of the white shading memory 323 when storing white shading correction data. Register. Here, the register 313 switches the bit position to be deleted depending on whether the mode designated by the mode selection signal is the copy mode or the scan mode. In the present embodiment, the upper 4 bits are deleted in the scan mode, and the lower 4 bits are deleted in the copy mode.

  FIG. 4 is a diagram illustrating a data flow when acquiring shading correction data in the scan mode in the configuration shown in FIG. Acquisition of shading correction data is executed after the offset adjustment and variable GAIN adjustment settings in the analog processing unit 105 shown in FIG. In addition, the order of obtaining the white shading correction data and the order of obtaining the black shading correction data may be first, but here, it is assumed that the white shading correction data is obtained first.

  When acquiring the white shading data, the image data is read after turning on the light source and moving the reading position of the CCD 103 to the position of the white plate with the white reference. The read analog image signal is converted into digital image data by the analog processing unit 105 and stored in the white shading memory 323 for the number of pixels of the CCD 103.

  As described above, in this embodiment, in order to reduce the capacity of the white shading memory 323, the number of bits (bits) of the white shading memory 323 is more than the number of bits of digital image data output from the analog processing unit 105 for each pixel data. The width is smaller. Therefore, as shown in (1), the data input to the shading correction unit 209 has a plurality of bits (4 bits in this embodiment) deleted from the lower order of the digital image data by the register 315 and passes through the memory i / f 319. It is stored in the white shading memory 323.

  Next, when acquiring the black shading data, the light source is turned off and the image data is read. The read analog image signal is converted into digital image data by the analog processing unit 105 and stored in the black shading memory 321 for the pixels of the CCD 103.

  In order to reduce the capacity of the black shading memory 321, the bit number (bit width) of the black shading memory 321 is smaller than the bit number of the digital image data output from the analog processing unit 105 for each pixel data. is there. Therefore, the data input to the shading correction unit 209 has its upper plurality of bits (4 bits in the present embodiment) deleted in the register 313 as shown in (2), and the black shading memory 321 via the memory i / f 317. Stored in

  Here, the case where the CCD 103 is a monochrome sensor has been described. However, when the CCD 103 is a color sensor, the white shading memory 323 and the black shading memory 321 store data for three colors of RGB for each pixel. It will be.

  FIG. 5 is a diagram for explaining a data flow when performing shading correction processing on data obtained by reading a document in the scan mode in the configuration shown in FIG.

  The analog image signal read by the CCD 103 is converted into digital image data by the analog processing unit 105, and at the same time, the black shading correction data and the white shading correction data are transferred from the black shading memory 321 and the white shading memory 323 to the corresponding memory i / f 317. And 319 through.

For the black shading correction data read from the black shading memory 321, 0 is added to the upper multiple bits (4 bits in this embodiment) in the register 309, and then the digital image data after A / D conversion is performed in the subtractor 301. Subtract from On the other hand, for the white shading correction data read from the white shading memory 323, 0 is added to the lower plural bits (4 bits in the present embodiment), and then output from the subtractor 301 and the 0 clamp circuit 303 as necessary. Divide the zero clamped data by that value. When overflow occurs as a result of division, the clamp circuit 306 clamps the digital data to the maximum value. For example, if the data is 12 bits wide, it is clamped at 2 ¹² −1 = 4095. As described above, shading-corrected data is obtained.

  FIG. 6 is a graph for explaining the magnitude of the quantization error in the scan mode when the gamma value is γ = 0.45. The horizontal axis of the graph represents the input luminance value, and the vertical axis represents the luminance value after the γ conversion. Since the γ-converted data at the time of scanning is returned to linear again on the PC side, it can be seen that the quantization error in the black portion having a small luminance value has a greater influence than the white quantization error. Therefore, it can be seen that in the shading correction before γ conversion, the bit accuracy of black shading is more important than the bit accuracy of white shading correction.

  FIG. 7 is a graph for explaining the magnitude of the quantization error in the copy mode. The horizontal axis of the graph represents the input luminance value, and the vertical axis represents the luminance value after the γ conversion. Since the gamma value γ = 1.0 at the time of copying, the luminance error is constant for all values. For this reason, even if the black shading data is tweaked as in the scan, the accuracy is not improved.

  FIG. 8 is a graph for explaining the magnitude of an error caused by a calculation in black shading correction. Since the calculation performed in the black shading correction is subtraction, the quantization error is constant for all values regardless of the luminance value. Therefore, in order to increase the accuracy of the black shading correction, it can be said that the bit accuracy equivalent to the input digital image data is necessary. However, since the black shading correction data is data read with the light source turned off, if the offset adjustment is performed properly by the analog processing unit, the value will be close to zero and all the upper bits should be zero. It is. In this embodiment, this is utilized, and in the scan mode, it is assumed that all of the upper bits of the black shading correction data are 0, and the bit width is reduced and stored, thereby effectively using the memory capacity.

FIG. 9 is a graph for explaining the magnitude of a calculation error in white shading correction. Since the calculation performed in the white shading correction is division, the ratio between the luminance value and the quantization error is constant. Therefore, as digital data, the larger the luminance value, the larger the quantization error. However, since the gamma value γ = 0.45 at the time of scanning as described with reference to FIG. 6, the error in the region close to white where the luminance is large is small, so even if some lower bits are deleted, Although the accuracy is slightly lowered, the image quality is not so affected.

FIG. 10 is a flowchart showing a processing sequence until scanning is started when a document is scanned in the scan mode.

  First, the analog processing unit and the read image processing unit are initially set (S101). Specific contents include various mode settings, CCD drive waveform settings, and the like.

  Next, the offset adjustment of the CCD is performed with the light source turned off (S102). Specifically, the offset value is adjusted so that the value of the digital image data, which is the output of the analog processing unit, becomes substantially zero for each pixel. However, it is set on the positive side so that the smallest data value does not become negative due to the variation of each pixel of the CCD.

  Thereafter, the light source is turned on (S103). At this time, if the light source is an LED, the light amount is immediately stabilized and the digital data is also stabilized. However, if the light source is a fluorescent lamp or the like, a waiting time is required until the light amount is stabilized.

  Next, the variable GAIN of the analog processing unit is adjusted (S104). As a specific adjustment, GAIN is set so that the maximum value of the read digital image data does not exceed a predetermined threshold value and becomes a large value (for example, about 80% to 90% of the threshold value).

  Then, white shading correction data is acquired (S105). As described above with reference to FIGS. 3 and 4, the white shading memory 323 stores data in which the lower 4 bits are deleted from the digital value obtained by reading the reference white plate of each CCD pixel.

  Next, the light source is turned off to obtain black shading correction data (S106). When the light source is an LED, it is turned off immediately, but when the light source is a cold cathode tube, there is afterglow, so a waiting time is required as in the case of lighting.

  Then, black shading correction data is acquired (S107). As described above with reference to FIGS. 3 and 4, the black shading memory 321 stores data in which the upper 4 bits are deleted from the digital value of the offset of each CCD pixel.

  Then, since the light source is turned off to obtain black shading correction data, the light source is turned on again (S108), and reading of the document is started (S109).

  FIG. 11 is a flowchart showing a processing sequence until scanning is started when a document is scanned in the copy mode.

  First, the analog processing unit and the read image processing unit are initialized as in the scan mode (S111).

  Next, the light source is turned on (S112). At this time, if the light source is an LED, the light amount is immediately stabilized and the digital data is also stabilized. However, if the light source is a fluorescent lamp or the like, a waiting time is required until the light amount is stabilized.

  Thereafter, the offset and gain are set (S113). Since the copy mode requires less bit precision than the scan mode, a predetermined value set in advance is set. Since the black shading correction range is equivalent to the white shading correction range, the offset and gain may be set so that the analog signal voltage of each pixel falls within the reference voltage range of the A / D converter.

  Then, white shading correction data is acquired (S114). As described above with reference to FIGS. 3 and 4, the white shading memory 323 stores data in which the lower 4 bits are deleted from the digital value obtained by reading the reference white plate of each CCD pixel.

  Next, the light source is turned off to obtain black shading correction data (S115). When the light source is an LED, it is turned off immediately, but when the light source is a cold cathode tube, there is afterglow, so a waiting time is required as in the case of lighting.

  Then, black shading correction data is acquired (S116). As described above with reference to FIGS. 3 and 4, the black shading memory 321 stores data in which the lower 4 bits are deleted from the digital value of the offset of each CCD pixel.

  Since the light source has been turned off to acquire black shading correction data, the light source is turned on again (S117), and reading of the document is started (S118).

  As described above, according to the present embodiment, in the digital multi-function peripheral, sufficient bit accuracy is ensured for black shading correction, and deterioration of image quality for white shading correction is suppressed to such a level that there is no practical problem. The memory capacity for storing shading correction data can be reduced. Furthermore, by changing the processing method between reading in the copy mode where processing speed is important and reading in the scan mode where accuracy is required, a result suitable for each mode can be obtained.

<Other embodiments>
In the embodiment described above, the reading apparatus using the line sensor adopting the CCD as the image pickup device has been described as an example of applying the present invention. However, the present invention is a reading apparatus using another type of image pickup device. It can also be applied to.

  The present invention may be applied to a system or a multi-function peripheral composed of a plurality of devices, or may be applied to a reading device composed of a single device.

  In the present invention, a software program for realizing the functions of the above-described embodiment (in this embodiment, a program corresponding to the flowcharts shown in FIGS. 10 and 11) is directly or remotely supplied to a system or apparatus. This includes the case where the object is also achieved by reading and executing the supplied program code by the computer of the system or apparatus. In that case, as long as it has the function of a program, the form does not need to be a program.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. That is, the claims of the present invention include the computer program itself for realizing the functional processing of the present invention.

  In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

It is a block diagram which shows the control structure of the multifunctional machine as one Embodiment of this invention. FIG. 2 is a block diagram illustrating in detail a part of an analog processing unit 105 and a read image processing unit 107 in FIG. 1. It is a block diagram which shows the structure of the shading correction | amendment part 209 of FIG. 2 in detail. FIG. 4 is a diagram illustrating a data flow when acquiring shading correction data in a scan mode in the configuration illustrated in FIG. 3. FIG. 4 is a diagram illustrating a data flow when performing shading correction processing on data obtained by reading a document in a scan mode in the configuration shown in FIG. 3. It is a graph explaining the magnitude | size of the quantization error in a scan mode when a gamma value is (gamma) = 0.45. It is a graph explaining the magnitude | size of the quantization error in copy mode. It is a graph explaining the magnitude | size of the error which arises by the calculation in black shading correction. It is a graph explaining the magnitude | size of the calculation error in white shading correction. It is a flowchart which shows the process until the reading start in scan mode. It is a flowchart which shows the process until the reading start in a copy mode.

Claims (10)

A light source for illuminating the document;
Reading means having a plurality of image sensors arranged in a predetermined direction;
Analog processing means for performing a predetermined process on the analog signal output from each image sensor and then converting it to digital data and outputting it,
First correction data acquisition means for deleting a plurality of upper or lower bits of digital data corresponding to each image sensor output from the analog processing means and storing them in a first memory with the light source turned off. When,
With the reading unit moved to the reading position of the white reference plate, the lower plurality of bits of the digital data corresponding to each image sensor output from the analog processing unit are deleted and stored in the second memory. Two correction data acquisition means;
Black shading correction means for correcting variations in output values of the respective image pickup elements in a state where the light source is turned off based on data stored in the first memory;
A reading apparatus, comprising: white shading correction means for correcting variations in the gain of each image sensor and the amount of light from the light source based on data stored in the second memory. The black shading correction means performs correction using data obtained by adding 0 to the upper or lower bits of the data stored in the first memory,
2. The reading apparatus according to claim 1, wherein the white shading correction unit performs correction using data obtained by adding 0 to a plurality of lower-order bits of data stored in the second memory.   The reading apparatus according to claim 1, wherein the number of bits of the upper plurality of bits and the number of the lower plurality of bits are equal.   The reading apparatus according to claim 3, wherein the number of bits is four.   2. The analog processing unit includes an offset adjusting unit that adjusts an offset value of the entire reading unit, a gain adjusting unit that adjusts a gain of the entire reading unit, and an A / D converter. 5. The reading device according to any one of 4 above. The first correction data acquisition means includes
When the scanner mode is designated, the upper multiple bits of the digital data corresponding to each image sensor output from the analog processing means are deleted and stored in the first memory, and the copy mode is designated. 2. The reading apparatus according to claim 1, wherein the lower plurality of bits of the digital data corresponding to each image sensor output from the analog processing means are deleted and stored in the first memory.   When the scanner mode is designated, the black shading correction means performs correction using data obtained by adding 0 to the upper bits of the data stored in the first memory, and the copy mode is designated. The reading apparatus according to claim 6, wherein correction is performed using data obtained by adding 0 to a plurality of lower-order bits of data stored in the first memory. A method for controlling a reading apparatus, comprising: a light source for irradiating a document; and reading means having a plurality of image sensors arranged in a predetermined direction,
An analog processing step of performing a predetermined process on the analog signal output from each image sensor and then converting it to digital data and outputting it,
A first correction data acquisition step of deleting a plurality of upper or lower bits of digital data corresponding to each image sensor output in the analog processing step and storing them in a first memory with the light source turned off When,
With the reading unit moved to the reading position of the white reference plate, the lower plurality of bits of the digital data corresponding to each image sensor output in the analog processing step are deleted and stored in the second memory. 2 correction data acquisition step;
Based on the data stored in the first memory, a black shading correction step for correcting variations in the output values of the imaging elements in a state where the light source is turned off,
A reading apparatus control method, comprising: a white shading correction step of correcting a gain of each image sensor and a variation in the amount of light from the light source based on data stored in the second memory.   In the first correction data acquisition step, when the scanner mode is designated, the upper plurality of bits of the digital data corresponding to each image sensor output from the analog processing means are deleted, and the first memory is stored in the first memory. When the storage mode and the copy mode are designated, the lower plurality of bits of the digital data corresponding to each image sensor output from the analog processing means are deleted and stored in the first memory. The method for controlling a reading device according to claim 8.   In the black shading correction step, when the scanner mode is designated, correction is performed using data obtained by adding 0 to the upper bits of the data stored in the first memory, and the copy mode is designated. 9. The method of controlling a reading apparatus according to claim 8, wherein correction is performed using data obtained by adding 0 to a plurality of lower-order bits of data stored in the first memory.

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