JP2008141624A - Image reading apparatus and image processing method therefor - Google Patents

Abstract

An image reading characteristic of an image reading apparatus that reads images on both sides of a document by one conveyance can be selectively switched by a user according to the purpose of reading the document image or the characteristics of the document image.
In an image reading apparatus that reads images on both sides of a document by one transport, a reading unit reads a front image of the document, and a reading unit reads a back image of the document. The control unit 102 controls the selectors 109 and 110 according to the user instruction input from the operation unit 101, and minimizes the color difference between the image read by the reading unit 501 and the image read by the reading unit 502. Are input to the color space conversion processing units 105 and 106. Alternatively, the image is input to the color space conversion processing units 107 and 108 that minimize the color difference between the image read by the reading unit 501 and the front image and minimize the color difference between the image read by the reading unit 502 and the back image.
[Selection] Figure 5

Description

  The present invention relates to an image reading apparatus that reads images on both sides of a document with a single conveyance.

  As means for electronically reading an image recorded on a document, there are image reading apparatuses such as a copying machine, a facsimile, and a scanner. Further, there is an automatic double-sided reading device that reads an image (hereinafter referred to as “double-sided image”) recorded on both sides of a document by reversing the front and back of the document by a document reversing unit without user intervention.

[Original reading unit of automatic duplex scanning device]
FIG. 1 is a diagram illustrating a schematic configuration example of the document reading unit 201.

  The pickup roller 203 picks up the originals 211 stacked on the original placing table 202 one by one and sends them to the reading path. The picked-up document 211 is conveyed through the conveying roller 204 in the direction of the path 1 formed by the roller 205 shown in the drawing. The document 211 that has reached the reading position through the path 1 is illuminated by the light source 208 provided in the reading unit 209 via the document table glass 210, and the reflected light from the document 211 enters the reading unit 209.

  The reading unit 209 includes a photoelectric conversion element and outputs an electrical signal corresponding to the intensity of incident light. This electric signal is converted into a digital signal by an analog-to-digital (A / D) converter (not shown), and digital image data indicating an image of a document is obtained. In this way, the reading unit 209 reads an image (hereinafter referred to as “surface image”) recorded on the surface of the document 211 passing through the reading position through the path 1. Note that the light source 208 has a spectral intensity substantially in the visible wavelength region. The intensity of light incident on the reading unit 209 depends on the spectral reflectance distribution of the image recorded on the document 211.

  When the leading end of the document 211 reaches the reverse conveyance / discharge roller 206, the document 211 is discharged from the document reading unit 201 to the trailing end. Thereafter, the document 211 is again taken into the document reading unit 201 by the reverse rotation of the reverse conveyance / discharge roller 206 and guided by the separation claw 207 in the direction of the path 2 formed by the roller 205.

  The document 211 that has passed the path 2 is transported again to the reading position through the path 1 by the transport roller 204. Then, an image recorded on the back side of the document 211 (hereinafter referred to as “back side image”) is read by the reading unit 209. Thereafter, the document 211 is discharged out of the document reading unit 201 by the reverse conveyance / discharge roller 206.

  The document reading unit 201 sequentially reads the images on both sides of a plurality of documents stacked on the document table 202 by repeating the above operation.

  The advantage of reading an image on both sides of an original with an automatic double-sided reading device having an original reading unit 201 as shown in FIG. 1 is that the image on both sides can be automatically read without user intervention. is there. Furthermore, since the images on both sides are read by a single light source and a single reading unit, the configuration of the reading optical system is single, and the geometric characteristics and color characteristics of the reading results of the images on both sides match.

  On the other hand, the document is transported through the document reading unit 201 twice, when reading the front image and when reading the back image, so that it takes time to read the image, and the document transport configuration becomes complicated, so that jamming occurs. There is a high probability.

[Simultaneous scanning device of the double-sided scanning device]
There is a simultaneous double-sided reading device that simultaneously reads both-side images by conveying a document once.

  FIG. 2 is a diagram illustrating a schematic configuration example of the document reading unit 301 of the simultaneous duplex reading apparatus.

  The pickup roller 203 picks up the originals 211 stacked on the original placing table 202 one by one and sends them to the reading path. The picked-up original 211 is conveyed through the conveying roller 204 in the direction of the path 3 formed by the roller 205 shown in the drawing. The document 211 that has reached the first reading position through the path 3 is illuminated by the light source 208 provided in the reading unit 209 via the document table glass 210, and the reflected light from the document 211 enters the reading unit 209. The reading unit 209 reads the surface image of the document 211 that passes through the first reading position.

  Thereafter, the document 211 reaches the second reading position, is illuminated by a light source 303 provided in the reading unit 304, and reflected light from the document 211 enters the reading unit 304. The reading unit 304 reads the back image of the document 211 that passes through the second reading position. Thereafter, the document 211 is discharged out of the document reading unit 301 by the discharge roller 302.

  The document reading unit 301 repeats the above-described operation, and reads the images on both sides of each document only by conveying each document loaded on the document table 202 once.

  The advantage of reading a double-sided image of a document with a simultaneous double-sided reading device having a document reading unit 301 as shown in FIG. 2 is that it can only automatically read a double-sided image without user intervention. Absent. In other words, since the images on both sides of the document are read in a single conveyance, the image reading time is shortened to improve the performance of the image reading apparatus, and the probability of jam occurrence can be reduced because there is only one conveyance path. .

  Hereinafter, a combination of the light source 208 and the reading unit 209 is referred to as a reading device A, and a combination of the light source 303 and the reading unit 304 is referred to as a reading device B.

Configuration of Reading Device A As shown in FIG. 2, the reading device A is arranged below the platen glass 210, and when the document 211 is placed on the platen glass 210, the reading device A is sub-scanned. The image on one side of the original 211 can be read by moving in the direction. Hereinafter, the reading method for moving the reading device is referred to as pressure plate reading.

  Reading device A used for platen reading has a margin in its arrangement space and scanning space, so use either the reduction optical system as shown in FIG. 3A or the equal magnification optical system as shown in FIG. 3B. It doesn't matter.

● Reading Image with Reduction Optical System Image reading with the reduction optical system shown in FIG. 3A is as follows.

  The reading unit 209 includes a mechanically fixed light source 208 and a reflection mirror 401, and the reading unit 209 itself moves in the direction of arrow A shown in the drawing. The reading unit 209, the light source 208, and the reflection mirror 401 have a width equal to or greater than the entire width of the document 211 to be read. In FIG. 3A, the width corresponds to the depth direction.

  The light L emitted from the light source 208 illuminates the document 211 through the document table glass 210. The light L reflected from the document 211 is reflected by the reflection mirror 401 and the optical path is changed. The light L is reduced by a reduction lens (f-θ lens) 403 and enters the photoelectric conversion element 402. The reduction lens 403 reduces the light L having a width equal to or larger than that of the document 211 in accordance with the width of the photoelectric conversion element 402.

  The photoelectric conversion element 402 is a semiconductor device that converts incident light into an electric signal, for example, a charge coupled device (CCD). Usually, the width of the photoelectric conversion element 402 is narrower than the width of the document 211. Therefore, the reduction ratio of the reduction lens 403 is determined based on the ratio between the width of the document 211 and the width of the photoelectric conversion element 402.

  The reading unit 209 and the reduction lens 403 of the reduction optical system move in the direction of the arrow A in synchronization and scan the original 211 to read the image of the original 211.

● Image reading by 1x optical system Image reading of 1x optical system shown in Fig. 3B is as follows.

  The reading unit 209, which is a contact image sensor (CIS) unit, includes a mechanically fixed light source 208, an equal magnification lens 404, and a photoelectric conversion element 402, and the reading unit 209 itself moves in the direction of arrow B shown in the figure. To do. The reading unit 209, the light source 208, the equal-magnification lens 404, and the photoelectric conversion element 402 have a width equal to or greater than the entire width of the document 211 to be read.

  The light L emitted from the light source 208 illuminates the document 211 through the document table glass 210. The light L reflected from the document 211 enters the photoelectric conversion element 402 via the equal magnification lens 404.

  In this way, the reading unit 209, which is a CIS unit, moves in the direction of arrow B and scans the document 211, thereby reading the image of the document 211.

Light Source and Photoelectric Conversion Element Generally, when reading a color image, the light source 208 uses a light source that covers the visible wavelength region. As the photoelectric conversion element 402, a device having three primary color red R, green G, and blue B color separation filters and three rows of photoelectric conversion element groups corresponding to the filters is used.

  Further, there is a method in which a light source capable of emitting R, G, and B wavelengths is used as the light source 208, and a device having a single photoelectric conversion element group is used as the photoelectric conversion element 402. That is, when scanning the original 211, the light source R, the light source G, and the light source B are sequentially turned on, the reflected light of each light source is read by a single photoelectric conversion element 402, and the R signal, G signal, and B signal obtained for each light source Are combined into color image data.

● Configuration of Reading Device B As is clear from the arrangement shown in FIG. 2, it is difficult to adopt a reduction optical system having a long optical distance, and the reading device B usually adopts an equal magnification optical system.

[Differences in reading characteristics due to differences in optical systems]
As described above, when the reduction optical system is used for the reading device A and the equal magnification optical system is used for the reading device B, the reading characteristics, particularly the color reproducibility, of the front and back images are different. Even if scanning devices A and B use the same optical system, the scanning characteristics, especially color reproducibility, may vary depending on factors such as how the document floats at the scanning position and how the external light is incident. There is sex.

  When the same or similar color exists in a wide range of both-side images, the user desires that the color reproducibility between the front and back of the color is equivalent. In addition, when there are almost no similar colors between the images on both sides, it is desired that the color reproducibility of the front and back sides is equivalent.

  In Patent Document 1, a characteristic parameter R of reference image data prepared in advance is compared with a characteristic parameter F of read image data of a surface image (hereinafter referred to as “surface image data”) to correct the characteristic parameter F. Thereafter, the back side image is read, the characteristic parameter F ′ after correction of the front surface image data is compared with the characteristic parameter Q of the read image data of the back side image (hereinafter referred to as “back side image data”), and the characteristic parameter Q is A method of correcting is disclosed. It is described that this method reduces the difference in characteristics between the front surface image data and the back surface image data.

  FIG. 4 is a diagram illustrating a procedure of image processing assumed to correct the difference in the simultaneous double-sided reading device in which the color reproducibility of both-side images is different.

  First, the reading unit 501 serving as the reading device A reads the surface image of the document 211 and generates Ra, Ga, and Ba signals. The Ra, Ga, and Ba signals have characteristics that depend on the reading device A, and are signals that have no meaning as a color system defined by the International Commission on Illumination (CIE). Then, the color space conversion processing unit 503 converts the Ra, Ga, Ba signals into Ra ′, Ga ′, Ba ′ signals in the color space associated with the CIE color system (for example, L * a * b *). The surface image data 505 is obtained.

  Next, the back image of the same document 211 is read by the reading unit 502 serving as the reading device B, and Rb, Gb, and Bb signals are generated. The Rb, Gb, and Bb signals also have characteristics that depend on the reading device B. Then, the color space conversion processing unit 504 converts the Rb, Gb, and Bb signals into the Rb ′, Gb ′, and Bb ′ signals in the color space associated with the CIE color system, and obtains back surface image data 506.

  The color space conversion processing units 503 and 504 can apply a three-dimensional lookup table (3DLUT) of input three signals and output three signals, and 3 × 3 or 3 × 9 array calculation processing. Further, since color space conversion is well known, detailed description thereof is omitted.

  An image with a depth of 8 bits per RGB color can represent about 16 million colors. However, when 3DLUT or array calculation processing is used, it is difficult to achieve the color difference ΔE = 0 for all colors. This is because in the case of 3DLUT, unless a table having entries for about 16 million colors is prepared, an interpolation calculation is always required, and quantization and interpolation calculation errors corresponding to the table size occur. Of course, the data size of a table having about 16 million entries is 500 MB, which is not realistic. On the other hand, even when array calculation processing is used, the color difference ΔE = 0 cannot be achieved because the relationship between RGB and L * a * b * is non-linear.

  The invention described in the cited document 1 tries to match the color reproducibility of the front image data with the front image of the original and match the color reproducibility of the back image data with the color reproducibility of the front image data. This method is effective for minimizing the color difference between the front image and the front image data of the document and the color difference between the front image data and the back image data. However, the minimization of the color difference between the back side image and the back side image data of the document cannot always be achieved.

  In other words, in the case of a document in which the same or similar color exists in a wide range of both-side images, a color processing system that makes the color reproducibility between the front and back of the color equivalent can be provided. It can satisfy the user's wishes. However, in the case of a document in which there is almost no similar color between the images on both sides, it is impossible to provide a color processing system that equalizes the color reproducibility of each of the front and back sides, and satisfies the user's request described above. I can't.

JP2005-020224

  An object of the present invention is to enable selective switching of image reading characteristics of an image reading apparatus that reads images on both sides of a document with a single conveyance.

  The present invention has the following configuration as one means for achieving the above object.

  An image reading apparatus according to the present invention is an image reading apparatus that reads images on both sides of a document by a single conveyance, and is arranged on a conveyance path of the document, and a first reading unit that reads a surface image of the document And a second reading unit arranged on the conveyance path for reading the back side image of the original, an image read by the first reading unit, and an image read by the second reading unit are minimized. A first image processing unit configured to minimize a color difference between the image read by the first reading unit and the front image, and a color difference between the image read by the second reading unit and the back image. A second image processing unit; and a control unit configured to input outputs of the first and second reading units to the first or second image processing unit in response to a user instruction.

  The image processing method according to the present invention includes a first reading unit that is arranged on a conveyance path of a document and reads a front image of the document, and a second reading that is arranged on the conveyance path and reads a back image of the document. And an image processing method of an image reading apparatus that reads images on both sides of a document by a single conveyance, the image read by the first reading means according to a user instruction, and the second The first image processing that minimizes the color difference of the image read by the reading means, or the color difference between the image read by the first reading means and the surface image is minimized, and the second reading means reads The second image processing for minimizing the color difference between the image and the back image is performed.

  According to the present invention, it is possible to selectively switch the image reading characteristics of an image reading apparatus that reads images on both sides of a document with a single conveyance. As a result, the user can selectively switch the image reading characteristics according to the purpose of reading the document image or the characteristics of the document image.

  Hereinafter, image processing according to an embodiment of the present invention will be described in detail with reference to the drawings. Hereinafter, for convenience, the simultaneous double-sided reading device mounted on the copying machine will be described, but it can also be mounted on a facsimile machine or a scanner.

[Constitution]
FIG. 5 is a block diagram illustrating a configuration example of the simultaneous double-sided reader according to the embodiment. Note that the mechanical configuration of the document reading unit 301 is almost the same as the configuration shown in FIG. 2, and a description thereof will be omitted.

  A reading unit 501 serving as the reading device A includes a light source 208 and a reading unit 209 shown in FIG. 2, and reads a surface image of a document. Similarly, the reading unit 502 serving as the reading device B includes the light source 303 and the reading unit 304 shown in FIG. 2, and reads the back side image of the document.

  The read image processing units 103 and 104 perform known image processing such as shading correction, linearity correction, and MTF correction on the image data read by the reading unit 501 or 502, respectively.

  The color space conversion processing unit 105 for the front and back color difference minimum mode performs color space conversion processing on the image read by the reading unit 501 when the front and back color difference minimum mode is set. The color space conversion processing unit 107 for the minimum color difference mode for originals performs a color space conversion process on the image read by the reading unit 501 when the minimum mode for color differences between originals is set.

  The color space conversion processing unit 106 for the front and back color difference minimum mode performs color space conversion processing on the image read by the reading unit 502 when the front and back color difference minimum mode is set. The color space conversion processing unit 108 for the minimum color difference mode for originals performs color space conversion processing on the image read by the reading unit 502 when the minimum mode for color differences between originals is set.

  The control unit 102 is a one-chip microprocessor having, for example, a CPU, a ROM, and a RAM, executes a control program stored in the ROM, and controls a screen of the operation unit 101 described later. Further, in accordance with a user instruction input from the operation unit 101, the selectors 109 and 100 are controlled to switch the subsequent color space conversion processing. The operation unit 101 corresponds to an operation panel of a copier equipped with a simultaneous duplex reading device.

  As shown in FIG. 5, the color space conversion processing unit may be switched according to a user instruction, but the same result can be obtained by replacing the color space processing coefficient of the color space conversion processing unit according to the user instruction. Needless to say.

[Operation Unit] FIG. 6 is a diagram illustrating details of the operation unit 101.

  The operation unit 101 includes a start key 701 for instructing the user to start a job such as copying or scanning. Further, a stop key 702 for canceling a job being executed, a numeric keypad 703 used for dialing and numerical value input during facsimile operation, and a reset key 704 for returning operation settings to initial values are provided. In addition, a screen unit 705 for displaying various setting information and selecting an operation mode or the like using a touch panel is provided.

  FIG. 7 is a diagram showing a default screen of the copy function displayed on the screen unit 705. As shown in FIG.

  The status display unit 801 displays the status of whether or not a job can be accepted, the set copy magnification, the set recording paper size, the number of copies, and the like. Further, the buttons on the screen unit 705 include the following buttons. Equal magnification button 802 that sets the copy magnification to 100%. A magnification button 803 for shifting to a detailed magnification setting mode. A paper selection button 804 for shifting to the recording paper size setting mode. A sorter button 805 for shifting to a finishing (staple or sort) setting mode. A density setting button 807 for setting the copy density. A duplex button 806 for shifting to a detailed setting mode for duplex scanning. Note that these buttons execute a function set for each button when the user touches the button by a touch panel method.

  When performing simultaneous duplex scanning, the user places a document on the document table 202 and presses the duplex button 806. By this operation, the display on the screen unit 705 shifts to the screen shown in FIG.

  FIG. 8 is a view showing a reading mode display screen of the copying machine.

  A double-sided → double-sided button 901 designates an operation mode in which images on both sides of a document are read and double-sided copying is performed on recording paper. A single-sided → double-sided button 902 designates an operation mode in which an image on one side of a document is read and two-sided images read from one side of two documents are copied on one sheet of recording paper. A double-sided → single-sided button 903 designates an operation mode in which images on both sides of a document are read, and a front side image is printed on an odd page and a back side image is printed on an even page. A page continuous double-sided button 904 designates an operation mode in which an original on a booklet is read, and a right page of the booklet is copied on the front side of the recording paper and a left page of the booklet is copied on the back side of the recording paper.

  Here, since the double-sided → double-sided button 901 or double-sided → single-sided button 903 is a double-sided reading mode for reading images on both sides of a document, the display on the screen unit 705 is displayed in FIG. 9 when any operation mode is designated. Move to the screen shown.

  FIG. 9 is a diagram showing a selection screen for the front / back color difference minimum mode or the document original color difference minimum mode.

  The user presses the front / back color difference minimum mode button 1001 to specify an operation mode that minimizes the front / back color difference of the scanned image, or presses the anti-document color difference minimum mode button 1002 to minimize the color difference between the document image and the scanned image. You can specify the mode. That is, the user can select one of the operation modes according to the purpose of reading the document or the characteristics of the document image.

[processing]
FIG. 10 is a flowchart showing a document image reading process in the duplex reading mode, which is a process executed by the control unit 102.

  When the duplex scanning mode is designated and the start key 701 is pressed, the control unit 102 determines designation of the minimum color difference mode (S1101). When the front / back color difference minimum mode is designated, the selectors 109 and 110 are controlled so that the output of the read image processing units 103 and 104 is input to the color space conversion processing units 105 and 106 (S1102). If the minimum color difference mode for the original is designated, the selectors 109 and 110 are controlled to input the outputs of the read image processing units 103 and 104 to the color space conversion processing units 107 and 108 (S1103).

  Next, the control unit 102 controls the document reading unit 301 shown in FIG. 2 to read images on both sides of the document (S1104). Then, it is determined whether or not reading of all the documents loaded on the document table 202 has been completed (S1105) .When reading of all the documents has been completed, the process is terminated. Returning to step S1104, the next original is read.

[Coefficient of color space conversion processing]
FIG. 11 is a diagram illustrating a model for explaining the difference between the front / back color difference minimum mode and the document color difference minimum mode. Note that the color space for comparing color differences is CIEL * a * b *, and the Euclidean distance between the two colors plotted on the L * a * b * space is ΔE. In order to clarify the illustration, the color difference in the color space conversion process is constant (ΔE = a).

  In FIG. 11, point O is a point where L * a * b * values of a certain color of the document image are plotted. A sphere 1301 having a radius a centered on the point O is equal to the accuracy range when the color space conversion coefficient is built with the L * a * b * value of the color as a target. For example, when the reading device A reads the above color, the L * a * b * value P after the color space conversion processing exists in the sphere 1301 with the radius a centering on the point O, but in the worst case Plotted on the boundary surface of the sphere 1301. This is the color reproduction accuracy by the combination of the reading device A and the color space conversion process when the L * a * b * value of the document is targeted.

  Further, when the coefficient of the color space conversion process of the reading device B is built with the point P as a target, the color reproduction accuracy by the combination of the reading device B and the color space conversion process is a sphere 1302 having a radius a centered on the point P. It is represented by When the reading device B reads the above color, the L * a * b * value Q ′ after the color space conversion processing is present in the sphere 1302 with the radius a centering on the point P. In the worst case, the sphere Plotted on 1302 interface.

  When color space conversion processing is built in this way, the color difference between point P and point Q 'must be 0 ≦ ΔE ≦ a, and the color difference between the front and back sides should be minimized within the range of color difference ΔE in the color space conversion processing. Can do. However, the color difference between the point O and the point Q ′ may be 0 ≦ ΔE ≦ 2a, and the color reproduction accuracy of the reading device B to be a document may not be minimized. At this time, the points O, P, and Q ′ are in a straight line on the L * a * b * space. Such a state is the smallest color difference between the front and back, but is not the smallest color difference between the original and the original.

  On the other hand, when the coefficient of the color space conversion process of the reading device B is built with the point O as a target, the color reproduction accuracy by the combination of the reading device B and the color space conversion process is a sphere 1301 having a radius a centered on the point O. expressed. When the reading device B reads the above color, the L * a * b * value Q after the color space conversion processing exists in the sphere 1301 having the radius a centered on the point O, but in the worst case, the sphere 1301. Is plotted on the boundary of.

  When color space conversion processing is built in this way, the color difference between point O and point P, and the color difference between point O and point Q are 0 ≦ ΔE ≦ a, and the color difference from the original is within the range of color difference ΔE in color space conversion processing. Within can be minimized. However, the color difference between the points P and Q may be 0 ≦ ΔE ≦ 2a, and the color difference between the front and back surfaces may not be minimized. At this time, the points Q, O, and P are aligned in the L * a * b * space. Such a state is the smallest color difference between the original and the original, but not the smallest color difference between the front and back sides.

  In other words, for example, color space conversion coefficient patches are recorded in the corners of the original, and the L * a * b * value (point O) obtained by reading the color patch is used as the target for the front and back color difference minimum mode. The coefficient of the color space conversion processing unit 105 is set. Furthermore, the L * a * b * value (point P) after the color space conversion processing unit 105 performs color space conversion processing on the read result of the color patch is used as a target, and the color space conversion processing unit 106 for the front and back color difference minimum mode. The coefficient may be set.

  Further, the coefficients of the color space conversion processing units 107 and 108 for the minimum color difference mode for originals may be set with the L * a * b * value (point O) obtained by reading the color patch as a target.

  The color patch for coefficient build is not limited to one color, but may be three colors such as RGB, and six colors including cyan C, magenta M, and yellow Y.

  As described above, it is difficult to unify the coefficient of the color space conversion process that realizes the minimum color difference between the front and back sides and the coefficient of the color space conversion process that realizes the minimum color difference with respect to the document. Therefore, the color space conversion processing coefficient built for the front / back color difference minimum mode and the color space conversion processing coefficient built for the original color difference minimum mode are used according to the user's mode selection, so that the user's original Can be reproduced in accordance with the purpose of reading the image or according to the characteristics of the document.

  Needless to say, a LUT corresponding to the input / output of the color space conversion process using the built coefficient may be created, and the LUT may be used as the color space conversion processing unit.

  The image processing according to the second embodiment of the present invention will be described below. Note that the same reference numerals in the second embodiment denote the same parts as in the first embodiment, and a detailed description thereof will be omitted.

[Constitution]
FIG. 12 is a block diagram illustrating a configuration example of the simultaneous double-sided reading device according to the second embodiment. Note that the mechanical configuration of the document reading unit 301 is almost the same as the configuration shown in FIG. 2, and a description thereof will be omitted.

  A page buffer 607 buffers image data output from the reading units 501 and 502.

  The read image processing unit 603 is connected to both the reading unit 501 and the reading unit 502, and performs known image processing such as shading correction, linearity correction, and MTF correction on the image data read by the reading units 501 and 502. Further, a register 604 for storing a processing coefficient when executing the read image processing is provided.

  A color space conversion processing unit 605 performs color space conversion processing in the front / back color difference minimum mode or the document color difference minimum mode on the image data output from the read image processing unit 603. In addition, a register 606 is provided for storing processing coefficients for executing the color space conversion processing.

  A ROM 602 is a storage unit that stores processing coefficients of the read image processing unit 603 and the color space conversion processing unit 605. In addition, you may use not only ROM but a non-volatile memory.

  The control unit 102 reads out the processing coefficient stored in the ROM 602 in accordance with a user instruction input from the operation unit 101 and sets the processing coefficient in the register 604 and the register 606.

  As described above, the simultaneous duplex reading apparatus according to the second embodiment is configured to include a single image processing system for the reading devices A and B. Therefore, the image data read by the reading devices A and B is temporarily stored in the page buffer 607 and sequentially transferred to the image processing system.

[processing]
FIG. 13 is a flowchart showing a document image reading process in the duplex reading mode, which is a process executed by the control unit 102.

  When the duplex scanning mode is designated and the start key 701 is pressed, the control unit 102 determines the designation of the minimum color difference mode (S1201). If the front / back color difference minimum mode is designated, the process proceeds to step S1202. If the minimum document color difference mode is designated, the process proceeds to step S1208.

  When the front / back color difference minimum mode is designated, the control unit 102 determines whether the current processing target is the front image or the back image (S1202). In the case of the front image, the coefficient of the read image processing for the front image is read from the ROM 602 and set in the register 604 (S1203), and the coefficient of the color space conversion processing for the front image and the front / back color difference minimum mode is read. It is set in the register 606 (S1204). Thereby, the read image process and the color space conversion process for the surface image are executed.

  Next, the control unit 102 returns the process to step S1202, but next, it is clear that the back side image is a processing target, so the ROM 602 reads the coefficient of the read image processing for the back side image and registers 604. (S1205). Then, the coefficients of the color space conversion processing for the back image and the front and back color difference minimum mode are read out and set in the register 606 (S1206). Thereby, the read image process and the color space conversion process are performed on the back image. Then, it is determined whether or not reading of all the documents loaded on the document table 202 has been completed (S1207) .When reading of all the documents has been completed, the process ends. Returning to step S1202, the next original is read.

  On the other hand, when the minimum document color difference mode is designated, the control unit 102 determines whether the current processing target is the front image or the back image (S1208). In the case of a front image, the read image processing coefficients for the front image are read from the ROM 602 and set in the register 604 (S1209), and the color space conversion processing coefficients for the front image and the minimum color difference mode for the original are read. Is set in the register 606 (S1210). Thereby, the read image process and the color space conversion process for the surface image are executed.

  Next, the control unit 102 returns the processing to step S1208. Next, since it is clear that the back side image is the processing target, the coefficient of the read image processing for the back side image is read from the ROM 602 and the register 604 is read out. (S1211). Then, the coefficients of the color space conversion processing for the back image and the anti-document color difference minimum mode are read and set in the register 606 (S1212). Thereby, the read image process and the color space conversion process are performed on the back image. Then, it is determined whether or not reading of all the documents loaded on the document table 202 has been completed (S1213) .When reading of all the documents has been completed, the process is terminated. Returning to step S1208, the next original is read.

  According to the above embodiment, in the case of an original having the same or similar color in a wide range of both-side images, a color processing system is provided that makes the color reproducibility between the front and back of the color equivalent. In addition, a color processing system is provided that equalizes the color reproducibility of each of the front and back sides of a manuscript that has almost no similar color between the images on both sides. The user can read the images on both sides of the document by switching both color processing systems in accordance with the purpose of reading the document or the characteristics of the document image.

[Other embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.

  Another object of the present invention is to supply a storage medium (recording medium) that records software for realizing the functions of the above-described embodiments to a system or apparatus, and a computer (CPU or MPU) of the system or apparatus executes the software. Is also achieved. In this case, the software itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the software constitutes the present invention.

  In addition, the above functions are not only realized by the execution of the software, but an operating system (OS) running on a computer performs part or all of the actual processing according to instructions of the software, and thereby the above functions This includes the case where is realized.

  In addition, the software is written in a function expansion card or unit memory connected to the computer, and the CPU of the card or unit performs part or all of the actual processing according to instructions of the software, thereby This includes the case where is realized.

  When the present invention is applied to the storage medium, the storage medium stores software corresponding to the flowchart described above.

The figure which shows the example of schematic structure of a document reading part, The figure which shows the schematic structural example of the original document reading part of a simultaneous double-sided reader, The figure explaining the image reading of a reduction optical system, The figure explaining the image reading of a 1x optical system, The figure which shows the procedure of the image processing assumed in order to correct | amend the difference in the simultaneous double-sided reader from which the color reproducibility of a double-sided image differs. Block diagram showing a configuration example of the simultaneous double-sided reading device of the embodiment, The figure explaining the details of the operation part, The figure which shows the default screen of the copying function which is displayed on the screen part, The figure which shows the display screen of the reading mode which a copier has, The figure which shows the selection screen of the front and back color difference minimum mode or the document original color difference minimum mode, A flowchart showing a document image reading process in the duplex reading mode; The figure which shows the model explaining the difference of the front and back color difference minimum mode and an original color difference minimum mode, Block diagram showing a configuration example of the simultaneous double-sided reading device of Example 2, 6 is a flowchart illustrating document image reading processing in a duplex reading mode.

Claims (6)

An image reading apparatus that reads images on both sides of a document by a single conveyance,
A first reading unit arranged on a conveyance path of the document and reading a surface image of the document;
A second reading unit disposed on the conveyance path and reading a back image of the document;
First image processing means for minimizing a color difference between the image read by the first reading means and the image read by the second reading means;
A second image processing means for minimizing a color difference between the image read by the first reading means and the front image, and a color difference between the image read by the second reading means and the back image;
An image reading apparatus comprising: control means for inputting outputs of the first and second reading means to the first or second image processing means in response to a user instruction.   2. The image reading apparatus according to claim 1, further comprising input means for inputting the user instruction.   3. The image reading apparatus according to claim 1, wherein the first reading unit includes a reduction optical system, and the second reading unit includes an equal magnification optical system. A first reading unit disposed on the document conveyance path and reading the front image of the document, and a second reading unit disposed on the conveyance path and reading the back image of the document, An image processing method of an image reading apparatus that reads images on both sides of a document,
In response to a user instruction, first image processing that minimizes the color difference between the image read by the first reading unit and the image read by the second reading unit, or the first reading unit reads And a second image process for minimizing a color difference between the image and the front image and minimizing a color difference between the image read by the second reading unit and the back image.   5. A computer program for controlling the image reading device to realize the image processing according to claim 4.   6. A computer-readable recording medium on which the computer program according to claim 5 is recorded.

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