JP2009218955A - Image processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To similarly correct processing algorithm or the like so that the quality of images of a surface image and the quality of a rear side image which are simultaneously read by a simple means coincide with each other. <P>SOLUTION: An image processor on which a mechanism for simultaneously reading both sides of a color original is mounted is provided with a first memory unit 105 for storing a surface image, a second memory unit 106 for storing a rear side image, an image comparator 108 for reading out image data at a plurality of specified positions on the surface image and the rear side image stored by the memory means to compare them and an image correcting unit 109 for correcting based on the comparison result of the image comparator 108, whereby the quality of the read rear side image coincides with the quality of the read surface image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image processing apparatus including a reading apparatus that can simultaneously read the front and back surfaces of a document, and more particularly to an image processing apparatus that unifies the image quality of the read front and back images.

  Conventionally, this technology is a double-sided image reading device that can simultaneously read double-sided originals, and is optimized for different image quality of double-sided original images by simultaneously reading on the front and back sides of the original under separate image reading conditions. A technique for performing processing and image compression processing is disclosed (see, for example, Patent Document 1).

JP 2007-81687 A

  However, in the conventional technology as described above, two types of processing on the front and back surfaces are necessary in order to determine the image quality individually on both sides and perform optimum image processing and image compression based on the determination. End up. For example, two systems of algorithms are required to implement these two systems, two circuits are required to implement the algorithms, and there is only one processing circuit. However, there is a problem in that switching control is frequently generated to realize two systems of processing, resulting in complicated control.

  The present invention has been made in view of the above, and an object of the present invention is to correct the processing algorithm and the like so that the image quality of the front and back images read simultaneously by simple means becomes the same. .

  In order to solve the above-described problems and achieve the object, the invention according to claim 1 has a double-sided document reading device that simultaneously reads both the front and back surfaces of a color document, and the image read by the double-sided document reading device. An image processing apparatus that performs image processing on a first storage unit that stores a front-side image read by the double-sided document reading device and a second storage that stores a back-side image read by the double-sided document reading device. And image data read out from the first storage means and the second storage means for comparison between image data at a plurality of specific positions of the front image and the back image stored in the first storage means and the second storage means respectively. Comparing means and image correcting means for executing MTF correction of the read image data on the back surface based on the comparison result of the image comparing means.

  The invention according to claim 2 further includes a non-volatile third storage unit, and the image correction unit stores correction data in the third storage unit, and the third storage unit is provided for each reading operation. The correction data is read out and corrected.

  The invention according to claim 3 includes an operation panel for setting the operation of the image processing apparatus, and sets a plurality of specific positions of the front and back images to be compared by the image comparison means from the operation panel. Features.

  Further, the invention according to claim 4 further includes a nonvolatile fourth storage unit, and when the correction data of the third storage unit is updated, the correction data before update is transferred to the fourth storage unit, The new correction data is backed up.

  The invention according to claim 5 further includes a pattern generating means for outputting an internal pattern for correcting the read image, and an internal pattern for correcting the read image generated by the pattern generating means on the recording paper. And an image output means for outputting.

  According to a sixth aspect of the present invention, in the case where the image output means includes a double-side output mechanism that outputs images on both sides of the recording paper, the internal pattern is drawn on both sides of the recording paper, When only a single-side output mechanism for outputting an image on one side is provided, the internal pattern is drawn only on one side of the recording paper.

  According to a seventh aspect of the present invention, when the internal pattern is output on both the front surface and the back surface, the front surface is stored in the first storage unit and the back surface is stored in the second storage in the double-sided document reading device. When the internal pattern is output on one side, the front side is stored in the first storage unit in the first reading, and the back side is stored in the second storage unit in the second reading. It is characterized by doing.

  The invention according to claim 8 is characterized in that when the image output means includes a double-sided output mechanism, the drawing position of the output pattern is output so as not to overlap the front side and the back side of the recording paper.

  An image processing apparatus according to the present invention is an image processing apparatus that includes a double-sided document reading device that simultaneously reads both the front and back sides of a color document, and that performs image processing on an image read by the double-sided document reading device. A first storage means for storing the front side image read by the double-sided original reading apparatus; a second storage means for storing the back side image read by the double-sided original reading apparatus; and the first storage means and the second storage means. Based on the comparison results of the image comparison means and the image comparison means for reading and comparing the image data at a plurality of specific positions of the front image and the back image stored in each from the first storage means and the second storage means And an image correction unit that performs MTF correction of the read image data on the back surface, so that the read image on the back surface has the same image quality as the read image on the front surface. There is an effect that it is possible.

  Exemplary embodiments of an image processing apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings.

(Embodiment)
FIG. 1 is a block diagram showing a system configuration including an image processing apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a front side reading unit that reads an image on the front side of a document, reference numeral 102 denotes a back side reading unit that reads an image on the back side of the document, and reference numeral 103 denotes a format that can handle characteristics unique to the front side reading unit 101 in subsequent processing. The front side reading I / F unit to be converted, reference numeral 104 is a back side reading I / F unit that converts the characteristics unique to the back side reading unit 102 into a format that can be handled by subsequent processing, and the reference numeral 105 stores the front side image read by the front side reading unit 101. A first storage unit 106 is a second storage unit that stores the back side image read by the back side reading unit 102, and 107 is an operation panel that allows the operator to specify the operation of the apparatus and to make necessary settings. is there.

  Reference numeral 108 denotes an image comparison unit that compares the images in the first storage unit 105 and the second storage unit 106 and generates back side image correction data. Reference numeral 109 denotes a back side image corrected by the correction data obtained by the image comparison unit 108. An image correction unit 110, a third storage unit 110 for storing correction data currently used, a fourth storage unit 111 for storing correction data used last time, and a code 112 An image processing unit that performs predetermined image processing on the front image and the back image, reference numeral 113 is a pattern generation unit that generates an internal pattern image according to the present invention, and reference numeral 114 is an internal pattern to be output to the subsequent stage, a front image, or a back image The selector 115 is an image forming unit that outputs image data from the previous stage to a recording sheet or the like.

  Next, an image flow of the image processing apparatus of FIG. 1 configured as described above will be described. The front and back surfaces of the double-sided document are simultaneously read, and the RGB image data of the front image is stored in the first storage unit 105 and the RGB image data of the back image is stored in the second storage unit 106. At this time, the image read from the surface reading unit 101 is converted by the surface reading I / F unit 103 in accordance with the characteristics of the subsequent processing and stored in the first storage unit 105. Similarly, the image read from the back side reading unit 102 is converted by the back side reading I / F unit 104 according to the characteristics of the subsequent processing and stored in the second storage unit 106. As a result, it is possible to perform the characteristic conversion so that the mechanically and electrically different characteristics of the front side reading unit 101 and the back side reading unit 102 are matched with each other in the subsequent processing, and the same processing can be performed on the front side and the back side.

  Next, the image comparison unit 108 reads and compares the image data at a plurality of specific positions of the front surface RGB image data and the back surface RGB image data stored in the first storage unit 105 and the second storage unit 106. The plurality of specific positions may be positions registered in advance or may be positions designated by the operator from the operation panel 107.

  FIG. 2 is a document in which a plurality of vertical line and horizontal line patterns having different numbers of lines per unit are arranged. Each adjacent vertical line pattern and horizontal line pattern are arranged so as to have the same number of lines (however, the pattern described at the bottom is excluded. The solid pattern will be described later). The image processing apparatus reads a document in which the pattern is drawn on both sides from the front side reading unit 101 and the back side reading unit 102, stores them in the first storage unit 105 and the second storage unit 106, and the image comparison unit 108 The MTF (Modulation Transfer function) levels on the front and back surfaces are compared.

  A method for calculating the MTF level in the main scanning direction will be described below. The MTF in the main scanning direction is calculated from the vertical line pattern shown in FIG. The calculation obtains the MTF in a specific area at a specific position specified in advance. An area indicated by a dotted line in FIG. 3 is a specific area for obtaining the MTF. The average value of G (green) image data in the line direction (sub-scanning direction) in this area is obtained for each column. FIG. 4 is an enlarged view of a line pattern in a specific area. As shown in this figure, the average value for each column is calculated from the read values of J pixels in the vertical direction of each pixel Y. This calculation formula is shown in Equation 1. Ya is an average value of the read values for each column. N indicates the number of pixels for one column in the specific area. Yj indicates the read value for one column in the specific area.

  Next, the maximum reading value and the minimum reading value are obtained from the average value of the reading values for each column in the specific area. When the average value of the reading values for each column is larger than the adjacent image, it is detected as a maximum value (Hn), and when it is small, it is detected as a minimum value (Lm), and the maximum value is obtained from the moving average values of these maximum values and minimum values. Max and the minimum value Min are calculated. This calculation formula is shown in Formula 2. Hn represents the maximum value, Lm represents the minimum value, Max (Y) represents the read value of the column with the maximum value, and Min (Y) represents the read value of the column with the minimum value.

  Similarly, MTF calculation in the sub-scanning direction is also obtained from the horizontal line. Although not shown in the figure, the MTF is obtained from a specific area of the horizontal line pattern. The average value of G (green) image data in the line direction (main scanning direction) in this area is obtained for each column. FIG. 5 is an enlarged view of a line pattern in a specific area. As shown in this figure, the average value for each line is calculated from the read values of I pixels in the horizontal direction of each pixel Y. This calculation formula is shown in Equation 3. Xa is the average value of the read values for each line. N indicates the number of pixels for one line in the specific area. Xi indicates the read value for one line in the specific area.

  Next, the maximum reading value and the minimum reading value are obtained from the average value of the reading values for each line in the specific area. When the average value of the reading values for each line is larger than the adjacent image, it is detected as a maximum value (Hn), and when it is small, it is detected as a minimum value (Lm), and the maximum value is obtained from the moving average values of these maximum values and minimum values. Max and the minimum value Min are calculated. This calculation formula is shown in Equation 4. Hn represents the maximum value, Lm represents the minimum value, Max (X) represents the maximum line read value, and Min (X) represents the minimum line read value.

  Next, a white solid pattern is drawn on the left side of the bottom of the correction sheet shown in FIG. 2, and a black solid pattern is drawn on the right side. The average value of the reading values of the white solid specific area is W, Let B be the average value of the pattern readings. FIG. 6 shows the relationship among Max, Min, W (background reading level), and B (solid reading level) at this time. The MTF is calculated according to the following formula depending on the ratio of the difference between Max and Min with respect to the difference between W (background reading level) and B (black solid reading level) of the solid pattern. In this calculation formula, the MTF is expressed in%, and the closer to 100%, the better the MTF.

    MTF = (Max−Min) / (W−B) × 100

  First, internal processing of the image comparison unit 108 will be described with reference to the flowchart of FIG. The processing in the main scanning direction uses 1 to 8 line pattern images of the read correction sheet of FIG.

  In FIG. 7, first, the vertical line pattern image 1 shown in the correction sheet of FIG. 2 is read (steps S11 and S12), and the MTF in the main scanning direction of the front line pattern is calculated and stored (step S13). . Subsequently, the MTF in the main scanning direction of the front line pattern is calculated and stored (step S14). Next, the MTFs in the main scanning direction on the front surface and the back surface are compared (step S15), and it is determined whether or not the comparison result is equivalent (step S16). If it is determined that the comparison result is not the same level, the strength of the enhancement filter in the main scanning direction is increased (step S17), the back surface line pattern is spatially filtered (step S18), and the process returns to step S14. On the other hand, if it is determined in step S16 that the comparison result is at the same level, the line pattern is shifted by one (step S19), and the process proceeds to step S12 to execute the subsequent processing. In this way, the vertical line pattern images 1 to 8 shown in the correction sheet of FIG. 2 are sequentially read to calculate the MTF in the main scanning direction, and the subsequent processing is sequentially performed.

  That is, in FIG. 7, the first line-of-interest pattern (PTN) of interest is calculated as a line pattern 1 in FIG. 2, and the MTF value of main scanning on the front side of this line pattern is calculated and stored. Next, similarly, the MTF value of the main scanning on the back side of this line pattern is calculated and compared with the previously stored MTF value in the main scanning direction on the front side. The MTF calculation method at this time is as described above. In addition, the comparison method at this time is, for example, the same as when the MTF value on the back surface is within ± 3% of the MTF value on the front surface, or equivalent when the MTF value is within ± 5% in advance. Just decide.

  If it is determined by this comparison that the two are equal, the line pattern (PTN) to be compared is shifted by one so that PTN = PTN + 1, and the MTF values of the front and back surfaces are again set as the target pattern. Calculate and compare for equality. At this time, if it is determined that they are not equal, the strength of the enhancement filter in the main scanning direction is increased, and the enhancement filter processing in the main scanning is performed on the image data of the attention pattern on the back surface.

  Thereafter, the MTF value of the back image subjected to further enhancement filter processing is calculated and compared with the held MTF value of the front surface. If the comparison results indicate that they are equivalent, the same processing is performed by shifting the line-of-interest pattern by one as described above. If they are not equivalent, the strength of the emphasis filter is increased as described above, the spatial filter processing is performed, and the surface MTF value is compared again. In this way, in this embodiment, the process is executed until the process of comparing the MTFs in the eight main scanning directions is completed, and the enhancement filter having the finally set intensity calculates the MTF values in the main scanning direction on the front and back surfaces. The main scanning spatial filter processing is the same.

  Similarly, for the sub-scanning direction, 9 to 16 line pattern images of the read correction sheet of FIG. 2 are used. This process is shown in the flowchart of FIG. As shown in FIG. 8, the horizontal line pattern image 9 shown on the correction sheet of FIG. 2 is read (steps S21 and S22), and the MTF in the sub-scanning direction of the front line pattern is calculated and stored (step S23). ). Subsequently, the MTF in the sub-scanning direction of the front line pattern is calculated and stored (step S24). Next, the MTFs in the sub-scanning direction of the front surface and the back surface are compared (step S25), and it is determined whether or not the comparison result is at the same level (step S26). If it is determined that the comparison result is not at the same level, the strength of the enhancement filter in the sub-scanning direction is increased (step S27), the back side line pattern is subjected to spatial filter processing (step S28), and the process returns to step S14. On the other hand, if it is determined in step S26 that the comparison result is at the same level, the line pattern is shifted by one (step S29), the process proceeds to step S22, and the subsequent processing is executed. As described above, the horizontal line pattern images 9 to 16 shown on the correction sheet of FIG. 2 are sequentially read, the MTF in the sub-scanning direction is calculated, and the subsequent processing is sequentially performed.

  That is, in FIG. 8, the first line-of-interest pattern (PTN) of interest is the line-pattern 9 of FIG. 2, and the MTF value of the sub-scan on the front side of this line-pattern is calculated and stored. Next, similarly, the MTF value of the back side sub-scanning of this line pattern is calculated and compared with the previously stored front side sub-scanning MTF value. The MTF calculation method at this time is also as described above.

  If it is determined by this comparison that the two are equal, the line pattern (PTN) to be compared is shifted by one so that PTN = PTN + 1, and the MTF values of the front and back surfaces are again set as the target pattern. Calculate and compare for equality. At this time, when it is determined that they are not equivalent, the strength of the enhancement filter in the sub-scanning direction is increased, and the sub-scanning enhancement filter processing is performed on the image data of the attention pattern on the back surface.

  Thereafter, the MTF value of the back image subjected to further enhancement filter processing is calculated and compared with the held MTF value of the front surface. If the comparison results indicate that they are equivalent, the same processing is performed by shifting the line-of-interest pattern by one as described above. If they are not equivalent, the strength of the sub-scanning enhancement filter is increased as described above, spatial filtering is performed, and the surface MTF value is compared again. In this manner, in the embodiment, the process is performed until the process of comparing the MTFs in the eight sub-scanning directions is completed, and the enhancement filter having the finally set intensity equalizes the MTF values in the sub-scanning direction on the front surface and the back surface. The sub-scanning spatial filter processing is performed.

  In this manner, parameters of the spatial filter for main scanning and the spatial filter for sub-scanning that make the front and back MTFs equal are derived.

  Next, the image correcting unit 109 performs main scanning filter processing and sub scanning filter processing on the back side image data read from the back side reading unit 102 according to the derived main / sub spatial filter processing parameters. The third storage unit 110 is storage means for storing the parameters of the spatial filter for MTF correction. This storage means is a non-volatile memory, and the parameters are retained even when the power is turned off. By using these parameters, the subsequent MTF levels can be made equal between the front image and the back image.

  The fourth storage unit 111 is a storage unit that holds the previous correction parameter. For example, when the parameters of the spatial filter are derived by the MTF correction, but there is a problem in the image of the subsequent reading due to variations in the reading means, the original is not set correctly, etc. The previous parameter can be stored so that the process parameter can be restored.

  Reference numeral 112 indicates that the back image is corrected to be equivalent to the front image by the image correction unit 109 in the previous stage, which is an image processing unit. Therefore, the image processing unit 112 does not significantly change the image processing contents on the front and back surfaces. Can be processed. Reference numeral 113 denotes a pattern generation unit. The correction sheet of FIG. 2 may be prepared as a correction document in advance, but by generating a pattern from the pattern generation unit 113, it is not necessary to prepare a correction sheet separately.

  Reference numeral 115 denotes an image forming unit. The image forming unit 115 may not be capable of duplex printing, and the front image and the corrected back image cannot be duplex printed. Can be output on one double-sided output paper.

  Further, by setting a specific position at which the pattern for performing the comparison process is read from the operation panel 107, the reading position can be finely adjusted due to different reading standards by the reading means. FIG. 9 shows the screen of the operation panel 107 at this time. For example, it is possible to specify the distance to the pattern specifying position in the vertical direction and the horizontal direction by using the upper left corner of the document as a reference. FIG. 10 is an operation screen for selecting whether to perform the comparison processing according to the present invention and obtain a new correction parameter or return to the previously obtained correction parameter. By selecting from the operation panel 107, a new parameter or a previous parameter can be selected.

  The flowchart at this time is shown in FIG. When this comparison process is performed to select a new parameter or to return to the previous correction parameter (steps S31 and S32), when the process is executed to make a new parameter, the current correction parameter in the third storage unit 110 is selected. Is transferred to the fourth storage unit 111 for backup (step S33), a process for deriving a new parameter is executed (step S34), and the new parameter is stored in the third storage unit 110 (step S35). When returning to the previous correction parameter, the correction parameter is read from the fourth storage unit 111 and overwritten in the third storage unit 110, whereby the previous correction parameter can be replaced with the current correction parameter (step). S36).

  Further, when the image forming unit 115 is provided with a double-sided output mechanism (for example, a double-sided conveying device using a switchback conveying mechanism as is generally known), the pattern generating unit 113 has two patterns on both sides of the output paper. A correction sheet as shown in FIG. 5 is output, and the correction process can be executed with the output correction sheet. The selector determines whether to output the front image stored in the first storage unit 105, the back image stored in the second storage unit 106, or the internal pattern from the internal pattern generation unit 113. Select by switching 114.

  In addition, when the pattern generation unit 113 outputs an internal pattern for correction on both sides from the image forming unit 115 having a double-sided mechanism, the correction pattern on the front surface and the correction pattern on the back surface are output so as not to overlap. Yes. This is because when the correction patterns on the front surface and the back surface overlap and are output, accurate correction parameters cannot be calculated due to the effect of show-through. A dotted line portion in FIG. 12 indicates a correction pattern on the back surface. By arranging in this way, even if show-through occurs, it can be avoided because it affects each other on the front and back. In this case, the specific position of the correction pattern can be specified by adding a uniform offset to the pattern position on the front surface to specify the pattern position on the back surface, and can be realized with a simple processing configuration.

  Therefore, according to the embodiment that has been invented above, the following effects are listed. First, an image processing apparatus equipped with a mechanism for simultaneously reading both sides of a color document, a first storage unit 105 that stores a front image, a second storage unit 106 that stores a back image, and a storage unit. By providing an image comparison unit 108 that reads and compares the image data at a plurality of specific positions of the stored front and back images, and an image correction unit 109 that corrects the read image data on the back side based on the comparison result of the image comparison unit 108. The read image on the back surface can have the same image quality as the read image on the front surface.

  Secondly, a nonvolatile third storage unit 110 is further provided. The image correction unit 109 stores correction data in the third storage unit 110, and reads the correction data from the third storage unit 110 for each reading operation. By correcting, the correction data obtained above can be corrected quickly and appropriately in the subsequent double-sided reading process.

  Third, the operation panel 107 capable of instructing the operation of the image processing apparatus is provided, and a plurality of specific positions of the front and back images to be compared by the image comparison unit 108 can be set from the operation panel 107, thereby specifying a correction sheet. You can select the sheet according to the original you want to scan at that time, and if you perform correction on both sides of the correction sheet, even if the correction pattern differs on the front and back sides, The reading position for correction can be made different depending on the setting from the panel 107, and the correction sheet can be flexibly handled.

  Fourth, the nonvolatile fourth storage unit 111 is provided, and when the correction data in the third storage unit 110 is updated, the correction data before update is transferred to the fourth storage unit 111 and stored as a backup. As a result, when the correction cannot be properly performed due to a mistake in the specific position set from the operation panel 107, the contents of the fourth storage unit 111 storing the previous correction data are stored in the third storage unit 110. By writing back to, it is possible to return to the previous correction process, and it is possible to reduce wasted time due to the fact that correction cannot be performed well.

  Fifth, an image forming unit that has a pattern generation unit 113 that outputs a read image correction internal pattern for the purpose of making a read original, and that outputs the read image correction internal pattern generated by the pattern generation unit 113 to output paper. 115, the recording paper on which the pattern output from the image processing apparatus of the present invention is drawn can be used as a correction sheet even when there is no appropriate correction sheet at hand. Can do.

  Sixth, when the image forming unit 115 includes a double-sided output mechanism (double-sided conveyance unit), the internal pattern is drawn on both sides of the recording paper, and when only the single-sided output mechanism is provided, the internal pattern is recorded on the recording paper. By drawing only on one side, the correction sheet can be output regardless of the presence or absence of the double-sided output mechanism, and the double-sided option of the output device is not affected.

  Seventh, in the above, when the internal pattern is output on both sides, the front side is stored in the first storage unit 105 and the back side is stored in the second storage unit 106 simultaneously by the color double-sided simultaneous reading mechanism, When the pattern is output on one side, it is stored in the first storage unit 105 by the first reading and stored in the second storage unit 106 by the second reading. The read image at the time of the double-sided reading can be corrected.

  Eighth, when the image forming unit 115 includes a double-sided output mechanism, the image on the back side of the correction sheet is corrected at the time of correction by outputting the drawing position of the output pattern so as not to overlap the front side and the back side of the output paper. The front image and the front image can be prevented from affecting the back image, and appropriate correction can be performed.

  As described above, the image processing apparatus according to the present invention is useful for an image processing apparatus provided with a reading apparatus that can simultaneously read the front and back surfaces of a document. It is suitable for an image processing apparatus, system, and method that unify the image quality of the back image.

1 is a block diagram showing a system configuration including an image processing apparatus according to an embodiment of the present invention. It is explanatory drawing which shows the example of a document which has arrange | positioned the several vertical line and horizontal line pattern which differed in the number of lines per unit. It is explanatory drawing which shows the example of a specific area in the case of calculating MTF of the main scanning direction from a vertical line pattern. It is an enlarged view of a vertical line pattern in a specific area. It is an enlarged view of the horizontal line pattern in a specific area. It is a graph which shows the relationship between Max, Min, W (background reading level), and B (solid reading level). It is a flowchart which shows the process example of the main scanning direction of an image comparison part. It is a flowchart which shows the process example of the subscanning direction of an image comparison part. It is explanatory drawing which shows the example of a screen of the operation panel which sets the specific position which reads the pattern for performing a comparison process from an operation panel. It is explanatory drawing which shows the example of an operation screen which selects whether it implements the comparison process concerning this invention and a new correction parameter is calculated | required or it returns to the correction parameter calculated | required last time. It is a flowchart which shows the processing operation in FIG. It is explanatory drawing which shows the correction pattern (dotted line part) of the back surface in the image forming part provided with the double-sided mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Front surface reading part 102 Back surface reading part 105 1st memory | storage part 106 2nd memory | storage part 107 Operation panel 108 Image comparison part 109 Image correction part 110 3rd memory | storage part 111 4th memory | storage part 112 Image processing part 113 Pattern generation part 115 Image formation Part

Claims (8)

An image processing apparatus having a double-sided document reading device that simultaneously reads both the front and back surfaces of a color document, and performing image processing on an image read by the double-sided document reading device,
First storage means for storing a surface image read by the double-sided document reading device;
Second storage means for storing a reverse image read by the double-sided document reading device;
Image comparison means for reading out and comparing the image data at a plurality of specific positions of the front image and the back image stored in the first storage means and the second storage means respectively from the first storage means and the second storage means; ,
An image correction unit that performs MTF correction of the read image data on the back surface based on the comparison result of the image comparison unit;
An image processing apparatus comprising:   Furthermore, a non-volatile third storage unit is provided, and the image correction unit stores the correction data in the third storage unit, and reads and corrects the correction data from the third storage unit for each reading operation. The image processing apparatus according to claim 1, wherein:   The image according to claim 1, further comprising an operation panel for setting an operation of the image processing apparatus, wherein a plurality of specific positions of the front and back images to be compared by the image comparison unit are set from the operation panel. Processing equipment.   Further, a nonvolatile fourth storage means is provided, and when the correction data in the third storage means is updated, the correction data before update is transferred to the fourth storage means, and the new correction data is backed up. The image processing apparatus according to claim 1, wherein: further,
Pattern generation means for outputting an internal pattern for correcting the read image;
Image output means for outputting an internal pattern for correcting the read image generated by the pattern generation means to recording paper;
The image processing apparatus according to claim 1, further comprising:   When the image output means includes a double-sided output mechanism that outputs images on both sides of the recording paper, the internal pattern is drawn on both sides of the recording paper, and only the single-sided output mechanism that outputs an image on one side of the recording paper. The image processing apparatus according to claim 5, wherein the internal pattern is drawn only on one side of the recording paper.   When the internal pattern is output on both the front and back surfaces, the front side is simultaneously stored in the first storage unit and the back side is stored in the second storage unit in the double-sided document reading device. 7. The apparatus according to claim 6, wherein when the data is output on one side, the front side is stored in the first storage unit by the first reading, and the back side is stored in the second storage unit by the second reading. The image processing apparatus described.   The image processing apparatus according to claim 6, wherein when the image output unit includes a double-sided output mechanism, the drawing position of the output pattern is output so as not to overlap the front side and the back side of the recording paper.

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