JP7552469B2 - Image reader - Google Patents

Description

The present invention relates to an image reading device.

Conventionally, electrophotographic image forming devices are known as multifunction peripherals (MFPs) that combine the functions of a printer, copier, and the like. In order for these image forming devices to achieve optimal color reproducibility, there are image reading devices that read the printed image with a scanner and feed back the read results (RGB values) to the image forming device, thereby correcting (calibrating) the amount of toner adhesion in the image forming device.

Such image reading devices may also be equipped with a colorimeter to more accurately correct the color information read by the scanner. A colorimeter can obtain highly accurate color information (color values), but it takes a certain amount of time to read the color information. On the other hand, a scanner is inexpensive, has a wide reading range, and takes less time to read color information than a colorimeter.

However, when reading a color patch (patch image) formed on a transparent recording medium, the color of the background is significantly reflected in the color information, and there is a problem in that the color information of the color patch formed on the recording medium cannot be accurately grasped. For example, when a white color patch is placed on a white background and read, the components of the color information originating from the color patch are confused with the components of the color information originating from the background, and the color information of the color patch cannot be obtained accurately.

In response to the above problem, Patent Document 1 describes a technique for measuring black and chromatic patches with a transparent print medium placed against a white background, measuring a white patch with the transparent print medium placed against a black background, and obtaining the error between the colorimetric values of the white, black, and chromatic inks formed by a standard printing device and the colorimetric values of the white, black, and chromatic inks formed by a target printing device as the error in the amount of white, black, and chromatic ink applied. The technique described in Patent Document 1 makes it possible to accurately obtain the error in the amount of ink applied to the transparent print medium (specifically, the error between the amount of ink applied by the standard machine and the amount of ink applied by the printing device to be corrected).

JP 2011-73306 A

However, the technology described in Patent Document 1 requires switching between a white background and a black background between measuring the black patch and the chromatic patch and measuring the white patch, which is time-consuming.

The present invention aims to provide an image reading device that can read multiple patch images formed on a transparent recording medium without any hassle.

One aspect of the image reading device according to the present invention is
a first image reading unit that reads patch images formed on a transparent recording medium for each of a plurality of colors including each of the colors CMYK, a white background, and a white image forming color ;
a first backing portion that faces the first image reading portion via a transport path along which the recording medium is transported and that constitutes a first opposing surface having one of white and black;
a second image reading unit that is disposed downstream of the first image reading unit in a conveying direction of the recording medium and that reads the patch image formed on the recording medium;
a second backing portion that faces the second image reading portion across the transport path and constitutes a second facing surface having the other of white and black;
a calibration processing unit that performs a calibration process so that the gradation values of the patch images read by the first and second image reading units become target gradation values;
Equipped with
The calibration processing unit calculates the degree of transparency of the patch image formed with a white background based on the reading results of the first and second image reading units, and performs a calibration process so that the calculated degree of transparency becomes a target degree .
Another aspect of the image reading device according to the present invention is
a first image reading unit that reads patch images formed on a transparent recording medium for each of a plurality of colors from a back side of the recording medium;
a first backing portion that faces the first image reading portion via a transport path along which the recording medium is transported and that constitutes a first opposing surface having a black color;
a second image reading unit that is disposed downstream of the first image reading unit in a conveying direction of the recording medium and that reads the patch image formed on the recording medium from a front side of the recording medium;
a second backing portion that faces the second image reading portion across the transport path and that constitutes a second facing surface having a white color;
Equipped with
the first image reading unit reads the patch image formed with a white color for image formation or a white color for a base;
The second image reading unit reads the patch image formed in each of the colors of CMYK or in a white background.

According to the present invention, patch images formed on a transparent recording medium can be read without much effort.

1 is a configuration diagram illustrating a configuration of an image forming system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a functional configuration of the image forming system according to the present embodiment. 11A and 11B are diagrams illustrating examples of calibration chart images according to the present embodiment. 5 is a flowchart showing an example of a calibration operation in the present embodiment. 10 is a flowchart showing an example of a calibration table generating operation in the present embodiment. 10 is a flowchart showing an example of a calibration table generating operation in the present embodiment. 10 is a flowchart showing an example of a calibration table generating operation in the present embodiment. FIG. 13 is a diagram showing the relationship between the degree of transparency, the amount of toner adhesion, and the scanner measurement value. 5 is a flowchart showing an example of a calibration operation in the present embodiment. 11A and 11B are diagrams illustrating examples of calibration chart images according to the present embodiment.

The following describes in detail the embodiments of the present invention with reference to the drawings.

Figure 1 is a schematic diagram showing the configuration of an image forming system 100 (corresponding to the "image reading device" of the present invention) according to this embodiment. The image forming system is composed of an image forming device 2 and an image reading device 3. A paper feed device 1 is provided upstream of the image forming device 2. A paper discharge device 4 is provided downstream of the image reading device 3. Note that the paper feed device 1 and the paper discharge device 4 do not necessarily have to be provided.

The image forming device 2 forms images, for example, by electrophotography, and is a so-called tandem type color image forming device that forms full-color images by vertically arranging multiple photoconductor drums 11W, 11Y, 11M, 11C, and 11K facing a single intermediate transfer belt 15. The image forming device 2 is configured with a document reading device SC, five sets of image forming sections 10W, 10Y, 10M, 10C, and 10K, and a fixing device 30.

The document reading device SC scans and exposes the image of the document using the optical system of the scanning exposure device, and reads the reflected light using a line image sensor to obtain an image signal. The image signal undergoes A/D conversion, shading correction, compression, and other processing, and is then input as the image reading value. Note that the input image data is not limited to that read by the document reading device SC, but may be, for example, data received from a personal computer connected to the image forming device 2, another image forming device, or data read from a portable recording medium such as a semiconductor memory.

The five image forming units 10W, 10Y, 10M, 10C, and 10K are composed of image forming unit 10W that forms a white (W) image, image forming unit 10Y that forms a yellow (Y) image, image forming unit 10M that forms a magenta (M) image, image forming unit 10C that forms a cyan (C) image, and image forming unit 10K that forms a black (K) image. Each image forming unit 10W, 10Y, 10M, 10C, and 10K is composed of photoconductor drums 11W, 11Y, 11M, 11C, and 11K, a charging unit arranged around the drums, an optical writing unit, a developing device, and a drum cleaner.

The surfaces of photoconductor drums 11W, 11Y, 11M, 11C, and 11K are uniformly charged by the charging unit, and a latent image is formed by scanning exposure by the optical writing unit. The developing device visualizes the latent image on photoconductor drums 11W, 11Y, 11M, 11C, and 11K by developing it with toner. As a result, an image (toner image) of a predetermined color corresponding to one of white, yellow, magenta, cyan, and black is formed on photoconductor drums 11W, 11Y, 11M, 11C, and 11K.

The images formed on the photoconductor drums 11W, 11Y, 11M, 11C, and 11K are transferred sequentially to predetermined positions on the rotating intermediate transfer belt 15 by the primary transfer roller. Note that yellow (Y), magenta (M), cyan (C), and black (K) correspond to the "CMYK colors" of the present invention. Also, white (W) corresponds to the "white color for image formation" of the present invention.

The image transferred onto the intermediate transfer belt 15 is transferred by the secondary transfer roller 16 onto paper P (corresponding to the "recording medium" of the present invention) that is transported at a predetermined timing by the paper transport unit 20. The secondary transfer roller 16 is positioned in pressure contact with the intermediate transfer belt 15 to form a secondary transfer nip.

The paper transport section 20 transports the paper P fed from the paper feed unit 21 along the transport path. In the paper feed unit 21, the paper P is loaded in a paper tray, and the paper P loaded in the paper tray is taken in by the paper feed section 22 and sent out to the transport path.

The transport path is provided with a number of paper transport means for transporting paper P. Each transport means is made up of a pair of rollers pressed against each other, with at least one of the rollers being driven to rotate by an electric motor, which serves as a drive means. In addition to being made up of a pair of rollers, the transport means can also be made up of a wide variety of configurations consisting of a pair of rotating members, such as a combination of belts or a combination of a belt and a roller.

The fixing device 30 is a device that performs a fixing process on the paper P onto which an image has been transferred. The fixing device 30 is configured, for example, with a pair of fixing rollers that are pressed against each other to form a fixing nip, and a heater that heats one or both of the fixing rollers. The fixing device 30 fixes the transferred image onto the paper P through the action of the pressure applied by the pair of fixing rollers and the heat of the fixing rollers. The paper P that has been subjected to the fixing process by the fixing device 30 is discharged outside the machine (outside the image forming device 2) by the paper discharge rollers 23.

When an image is to be formed on the back side of the paper P, the paper P after image formation on the front side is transported to the re-feed transport path by the switching gate 24. In the re-feed transport path, the rear end of the transported paper P is clamped by reversing rollers, and then the paper P is reversed by being fed in the opposite direction. The paper P whose front and back have been reversed is transported by multiple transport rollers and is made to merge with the transport path upstream of the transfer position in order to be used for image formation on the back side.

The operation panel 45 is a touch panel type input section that allows the user to input information according to information displayed on a display (not shown). By operating the operation panel 45, the user can set information about the paper P, specifically, the image density or magnification, the paper tray from which the paper is fed, and the like. The operation panel 45 can also function as a display section that displays various information to the user via the operation panel 45 when controlled.

The image reading device 3 is disposed downstream of the image forming device 2 in the transport direction of the paper P. The image reading device 3 is provided with a paper transport section 50. The paper transport section 50 has a transport path for transporting the paper P fed from the image forming device 2 and discharging it outside the machine.

In addition, in the image reading device 3, a first scanner 60a (corresponding to the "first image reading unit" of the present invention), a second scanner 60b (corresponding to the "second image reading unit" of the present invention), and a spectrophotometer 70 (corresponding to the "color measurement unit" of the present invention) are provided from the upstream side to the downstream side in the transport direction of the paper P.

A first backing 80a (background member, corresponding to the "first backing portion" of the present invention) is provided at a position facing the first scanner 60a so that the first scanner 60a can read the image on the paper P with high accuracy. The first backing 80a faces the first scanner 60a via the transport path along which the paper P is transported, and constitutes a first opposing surface that is black (background color).

A second backing 80b (background member, equivalent to the "second backing portion" of the present invention) is provided at a position facing the second scanner 60b so that the second scanner 60b can read the image on the paper P with high accuracy. The second backing 80b faces the second scanner 60b via the transport path along which the paper P is transported, and constitutes a second opposing surface having a white color (background color).

A third backing 80c (background member) is provided at a position facing the spectrophotometer 70 so that the spectrophotometer 70 can accurately measure the color of the image on the paper P. The third backing 80c faces the spectrophotometer 70 via the transport path along which the paper P is transported, and constitutes a third opposing surface having a white color (background color).

When the image reading device 3 receives the paper P supplied from the image forming device 2, it detects the image formed on the paper P. The first and second scanners 60a and 60b are each disposed to face the paper P transported along the transport path, and read the image formed on the paper P.

Specifically, the first scanner 60a reads the image formed on the paper P from the back side of the paper P (corresponding to the "first side" of the present invention), and is used, for example, to read the patch image formed on the paper P, check for misalignment between the front and back of the image formed on the paper P, and check for the presence or absence of unexpected images.

The second scanner 60b reads the image formed on the paper P from the front side of the paper P (corresponding to the "second side opposite to the first side" in the present invention), and is used for reading patch images and the like formed on the paper P. Hereinafter, the first scanner 60a and the second scanner 60b will be collectively referred to as the scanner 60.

Next, the functional configuration of the image forming device 2 and the image reading device 3 will be described with reference to FIG. 2. FIG. 2 is a diagram showing an example of the functional configuration of an image forming system according to this embodiment. The functional configuration of the image forming system 100 can be realized using a microcomputer mainly composed of a CPU, ROM, RAM, and an I/O interface.

First, the scanner 60 and the spectrophotometer 70 will be described. The scanner 60 is provided upstream of the spectrophotometer 70 in the transport direction of the paper P, and is configured with a light source 101 that irradiates light onto the paper P passing the reading position, and a line image sensor in which multiple image pickup elements that perform photoelectric conversion for each pixel are arranged one-dimensionally in the paper width direction.

Here, the imaging element is specifically a CCD (Charge Coupled Device). The CCD is an optical sensor that reads the image on the paper P at the reading position, and by being arranged in a line, it functions as a color line sensor that can read the entire range in the width direction of the paper P. The imaging element may also be a CMOS (Complementary MOS).

Specifically, when actually performing a reading operation, in addition to the image sensor, an optical system (not shown) and a light source 101 of an LED (Light Emitting Diode) that illuminates the reading position work in conjunction with each other. The optical system is for guiding the image at the reading position to the CCD, and is equipped with multiple mirrors and multiple lenses. The above-mentioned line image sensor can be realized by a CCD line sensor 103.

The reading range of the scanner 60 is set to cover the maximum width of the paper P that can be supplied from the image forming device 2. The scanner 60 reads the image formed on the paper P as a two-dimensional image by repeatedly reading one line of an image extending in the paper width direction in accordance with the transport operation of the paper P passing the reading position. The read image is generated as image measurement values (RGB values).

In other words, the scanner 60 has a line image sensor that reads the paper P along the width direction of the paper P, and can obtain an image of the entire surface of the paper P by reading the width of the paper P as one line in the transport direction of the paper P. Also, if the spectrophotometer 70 and the scanner 60 are collectively referred to as the reading device 55, the image reading device 3 feeds back the results of reading the paper P by the reading device 55 to the image forming device 2. In other words, the image forming device 2 performs a calibration process that creates a calibration table for each color of the image to be formed on the paper P based on the results of reading the paper P by the image reading device 3.

The spectrophotometer 70 is disposed so as to face the paper P being transported along the transport path, and is disposed downstream of the scanner 60 in the transport direction of the paper P. The spectrophotometer 70 measures the color of the image formed on the paper P, specifically, the patch image, etc.

The spectrophotometer 70 irradiates a patch image or the like formed on the paper P with a visible light source from the light source 105, acquires the spectral spectrum of the reflected light of the visible light source using the spectroscopic imaging unit 107, and performs calculations into a predetermined color system. This derives the color (color value) of the patch image or the like formed on the paper P.

The color measurement range of the spectrophotometer 70, i.e., the viewing angle, is set to be narrower than the reading range of the scanner 60 and narrower than the width of the patch image along the paper width direction. In this way, the spectrophotometer 70 performs color measurement within a limited range of viewing angles, and therefore can obtain color information with higher accuracy than the scanner 60.

As shown in FIG. 1, the image forming device 2 is disposed upstream of the image reading device 3 in the transport direction of the paper P. The image reading device 3 operates in either an inline mode or an offline mode.

The inline method is configured to feed paper P with an image formed thereon, which is discharged from the image forming device 2, directly to the image reading device 3. On the other hand, the offline method is not configured to feed paper P with an image formed thereon, which is discharged from the image forming device 2, directly to the image reading device 3, but rather is a method in which the image forming device 2 and the image reading device 3 are configured independently. Here, the following explanation will be given assuming the inline method, but the image reading device 3 may also operate in the offline method.

Next, we will explain the control unit 123 and image forming units 10W, 10Y, 10M, 10C, and 10K that are configured as the functional components of the image forming device 2. The control unit 123 corresponds to the "calibration processing unit," "reading result correction unit," and "color value correction unit" of the present invention.

The control unit 123 performs a calibration process for each color of the image formed on the paper P, based on the results of reading the patch images formed on the paper P by the first and second scanners 60a and 60b. The calibration process is a process for correcting changes in the output characteristics of the image forming device 2 in order to maintain a constant color reproducibility of the image forming device 2.

Figure 3 shows an example of a calibration chart image used for the calibration process. The calibration chart image is an image in which patch images are arranged in the number required to perform the calibration process for each color of the image to be formed on the paper P.

In the example shown in FIG. 3, the calibration chart image is composed of multiple patch images 200 corresponding to black (K), multiple patch images 202 corresponding to cyan (C), multiple patch images 204 corresponding to magenta (M), multiple patch images 206 corresponding to yellow (Y), multiple patch images 208 corresponding to white (W), and multiple patch images 210 corresponding to background white (W) on one page. Note that background white (W) corresponds to the "white background" of the present invention.

In addition, multiple patch images 200 corresponding to black (K), multiple patch images 202 corresponding to cyan (C), multiple patch images 204 corresponding to magenta (M), multiple patch images 206 corresponding to yellow (Y), and multiple patch images 208 corresponding to white (W) may be configured on one page, and multiple patch images 210 corresponding to the base white (W) may be configured on one page.

An example of the calibration operation of the control unit 123 will be described with reference to the flowchart in FIG. 4. Note that the process shown in FIG. 4 is executed, for example, when a user requests execution of the calibration process via an operation on the operation panel 45.

First, the control unit 123 controls the image forming units 10W, 10Y, 10M, 10C, and 10K to form a calibration chart image (see FIG. 3) on the surface of transparent paper P (transparent substrate) (step S101).

Next, the control unit 123 acquires the reading result of the first scanner 60a, which reads the calibration chart image (specifically, patch images 208, 210 corresponding to white (W) and base white (W)) formed on the paper P from the back side of the paper P (step S102).

Next, the control unit 123 acquires the reading result of the second scanner 60b, which reads the calibration chart image (specifically, patch images 200, 202, 204, 206, 210 corresponding to black (K), cyan (C), magenta (M), yellow (Y), and base white (W)) formed on the paper P from the front side of the paper P (step S103).

It is preferable that the second scanner 60b reads the patch images 200, 202, 204, 206, and 210 corresponding to black (K), cyan (C), magenta (M), yellow (Y), and base white (W) formed on the paper P from the front side of the paper P. The reason for this is that if the patch images 200, 202, 204, 206, and 210 are read from the back side of the paper P (i.e., through the paper P), an error will occur in the reading result of the second scanner 60b depending on the parameters representing the transparency of the paper P (e.g., film thickness and transparency). Generally, errors are more likely to occur in the reading results of the second scanner 60b for each of the CMYK colors than for white, so in this embodiment, the second scanner 60b ensures the reading accuracy of the second scanner 60b by reading patch images 200, 202, 204, 206, and 210 corresponding to black (K), cyan (C), magenta (M), and yellow (Y) formed on the paper P from the front side of the paper P.

Next, the control unit 123 generates a calibration table for each color of the image to be formed on the paper P based on the results of reading by the first and second scanners 60a, 60b (step S104). The calibration table is a correction table that indicates the correspondence between the output characteristic values (e.g., density values, brightness values, etc.) of the image forming device 2. The specific operation of step S104 will be described with reference to the flowcharts of Figures 5 to 7.

Finally, the control unit 123 registers the generated calibration table by storing it in a storage unit (not shown) (step S105). When the process of step S105 is completed, the control unit 123 ends the process shown in FIG. 4.

Next, referring to the flowchart in FIG. 5, an example of the calibration table generation operation for each of the CMYK colors (black (K), cyan (C), magenta (M), and yellow (Y)) performed by the control unit 123 will be described.

First, the control unit 123 refers to target value information indicating the target RGB values (corresponding to the "target gradation values" of the present invention) for maintaining a constant color reproducibility of the image forming device 2 for each color (black (K), cyan (C), magenta (M), and yellow (Y)) (step S201).

Finally, the control unit 123 generates a calibration table for each of the colors black (K), cyan (C), magenta (M), and yellow (Y) so that the actual RGB values (tone values) of the patch images 200, 202, 204, and 206 formed from the scan results of the second scanner 60b, specifically black (K), cyan (C), magenta (M), and yellow (Y), match the target RGB values (step S202). Completion of the process of step S202 causes the control unit 123 to end the process shown in FIG. 5.

Next, an example of the operation of generating a calibration table for white (W) by the control unit 123 will be described with reference to the flowchart in FIG. 6.

First, the control unit 123 refers to correction information including parameters representing the transparency of the paper P (step S301). The correction information corresponds to the "transparency information" of the present invention, and specifies the film thickness, transparency, etc. of the paper P as parameters representing the transparency of the paper P.

Next, the control unit 123 corrects the reading result of the first scanner 60a, specifically the actual RGB values (tone values) of the patch image 208 formed in white (W), with the correction information referenced in step S301 (step S302). The reason for correcting the RGB values (tone values) of the patch image 208 with the correction information is that if the patch image 208 is read from the back side of the paper P (i.e., through the paper P), it will be adversely affected depending on the film thickness, transparency, etc. of the paper P, causing errors in the reading result of the first scanner 60a.

The correction information may be generated based on the results of reading the paper P itself (i.e., paper P on which no image is formed) by the first scanner 60a, or may be generated in advance according to the type of paper P.

Next, the control unit 123 refers to target value information indicating target RGB values (corresponding to the "target gradation values" of the present invention) for maintaining a constant color reproducibility of the image forming device 2 for white (W) (step S303).

Finally, the control unit 123 generates a calibration table for white (W) so that the RGB values (tone values) of the patch image 208 corrected in step S302 become the target RGB values (step S304). When the process of step S304 is completed, the control unit 123 ends the process shown in FIG. 6.

Next, an example of the operation of the control unit 123 to generate a calibration table for background white (W) will be described with reference to the flowchart in FIG. 7.

First, the control unit 123 calculates the degree of transparency of the patch image 210 based on the reading results of the first and second scanners 60a and 60b, specifically, the RGB values (tone values) of the patch image 210 formed with a white (W) base (step S401).

Specifically, control unit 123 calculates corrected RGB values (=R1, G1, B1) of patch image 210 read by first scanner 60a using correction information related to the transparency of paper P. Then, control unit 123 calculates the degree of transparency (index) of patch image 210 for each of RGB using the RGB values (=R2, G2, B2) of patch image 210 read by second scanner 60b and the corrected RGB values (=R1', G1', B1') as shown in the following formula (1).
Degree of transparency of patch image 210={(RGB value (=R2, G2, B2)-corrected RGB value (=R1', G1', B1'))/RGB value (=R2, G2, B2)}×100 (1)

The greater the transparency of the patch image 210, the more transparent the patch image 210 formed with the white base (W) is. Generally, among RGB, the G value is most correlated with lightness, so it is preferable to use the transparency calculated with the G value as the transparency of the patch image 210 formed with the white base (W). However, depending on the white base (W), it may be easier to calculate the transparency with a color other than G, and in this case it is not necessarily necessary to use the transparency calculated with the G value as the transparency of the patch image 210 formed with the white base (W).

Finally, the control unit 123 generates a calibration table for the base white (W) so that the transparency of the patch image 210 calculated in step S401 becomes the target degree (step S402). In this embodiment, the target degree is set in advance in the image forming device 2 in order to maintain the color reproducibility of the image forming device 2 for the base white (W) in a constant state. When the process of step S402 is completed, the control unit 123 ends the process shown in FIG. 7.

Figure 8 shows the relationship between the degree of transparency, the amount of toner adhesion, and the scanner measurement value. Figure 8A shows the relationship between the degree of transparency and the amount of toner adhesion. As shown in Figure 8A, for a patch image 210 formed with a white (W) base, the degree of transparency decreases in proportion to the increase in the amount of toner adhesion within a range below a predetermined amount.

Figure 8B is a diagram showing the relationship between the degree of transparency and the scanner measurement value. As shown in Figure 8B, for patch image 210 formed with base white (W), the scanner measurement value decreases in proportion to the increase in the degree of transparency within a range equal to or greater than a predetermined value. Based on the relationship between the degree of transparency, the amount of toner adhesion, and the scanner measurement value shown in Figures 8A and 8B, the degree of transparency (amount of toner adhesion) can be adjusted from the scanner measurement value to the target degree of transparency (amount of toner adhesion) for patch image 210 formed with base white (W).

Next, referring to the flowchart in FIG. 9, an example of the operation of generating a calibration table by the control unit 123 using the color measurement results of the spectrophotometer 70 will be described. Here, an example of a calibration chart image 300 (see FIG. 10) that can also perform calibration of multi-colors such as secondary colors (RED, GREEN, BLUE) and tertiary colors (GRAY), for which correction by the spectrophotometer 70 is particularly effective, will be described.

First, the control unit 123 controls the image forming units 10W, 10Y, 10M, 10C, and 10K to form a calibration chart image 300 (see FIG. 10, specifically, patch images corresponding to black (K), cyan (C), magenta (M), yellow (Y), red (R), green (G), blue (B), and gray) on the surface of a transparent sheet P (transparent substrate) (step S501).

Next, the control unit 123 acquires the reading result of the second scanner 60b, which reads the calibration chart image 300 formed on the paper P from the front side of the paper P (step S502).

Next, the control unit 123 acquires the color measurement results of the spectrophotometer 70, which measures a portion of the calibration chart image 300 formed on the paper P (patch images 302 within the frames arranged in the center of the calibration chart image in FIG. 10) from the front side of the paper P (step S503). These patch images 302 within the frames are patch images whose color information is read by both the spectrophotometer 70 and the second scanner 60b, and are arranged so that one patch image is included for each color type to be calibrated.

Next, the control unit 123 refers to the scanner profile (a conversion table from RGB values to color values (L*a*b* values)) that is preset in the image forming device 2, and calculates color values from the read results (RGB values) of the patch image read in step S502 (step S504).

Next, the control unit 123 corrects the color value (calculated color value) of the corresponding patch image (step S505) using the color measurement result (colorimetric color value) of the patch image 302 within the frame obtained in step S503 by the spectrophotometer 70, the color value (calculated color value) calculated in step S504, and the read result (RGB value) read in step S502. The difference between the colorimetric color value and the calculated color value of the patch image 302 within the frame makes it possible to accurately correct the calculated color value (step S504) of the patch image read by the second scanner 60b in step S502.

Finally, the control unit 123 generates a calibration table for the corresponding color so that the color values of the patch image corrected in step S505 become target color values for maintaining a constant color reproducibility of the image forming device 2 (step S506). Upon completion of the process of step S506, the control unit 123 ends the process shown in FIG. 9.

As described with reference to the flowchart in FIG. 9, the results of measuring some of the patch images of the calibration chart image (patch images 302 within the frame aligned in the center of the calibration chart image in FIG. 10) by the spectrophotometer 70 can be used to accurately calculate the color values of patch images that were not measured by the spectrophotometer 70 (patch images outside the frame in the calibration chart image in FIG. 10). Therefore, even if the spectrophotometer 70 cannot measure all of the patch images of the calibration chart image, the color values of the entire calibration chart image can be accurately determined. In particular, when it is desired to perform multi-color calibration of secondary colors (RED, GREEN, BLUE) or tertiary colors (GRAY), the color values of the entire calibration chart image can be accurately determined.

Moreover, if all patch images of the calibration chart image are measured by the spectrophotometer 70, the color values of the patch images can be obtained with high accuracy, but the color measurement takes time, which slows down the calibration process. Therefore, by using the results of measuring some of the patch images of the calibration chart image by the spectrophotometer 70 to correct the color values of the patch images that were not measured by the spectrophotometer 70, it is possible to obtain color values with high accuracy while preventing a slowdown in the calibration process.

As described above in detail, in this embodiment, the image forming system 100 (image reading device) includes a first scanner 60a (first image reading unit) that reads patch images formed on transparent paper P (recording medium) for each of a plurality of colors, a first backing 80a (first backing unit) that faces the first scanner 60a via the transport path along which the paper P is transported and constitutes a first opposing surface having a white color, a second scanner 60b (second image reading unit) that reads the patch images formed on the paper P downstream of the first scanner 60a in the transport direction of the paper P, and a second backing 80b (second backing unit) that faces the second scanner 60b via the transport path and constitutes a second opposing surface having a black color.

In this embodiment, which is configured in this manner, all patch images formed on paper P can be read in one pass (one paper transport) using the first scanner 60a and the second scanner 60b, so patch images formed on transparent paper P can be read without the need to switch between a white background and a black background between reading black patch and chromatic patch images and reading white patch images, as is the case with conventional technology.

In the above embodiment, an example has been described in which the image reading device 3 is disposed downstream of the image forming device 2 in the transport direction of the paper P, but the present invention is not limited to this. For example, the image reading device 3 may be disposed within the image forming device 2. In this case, the image forming device 2 corresponds to the "image reading device" of the present invention.

In addition, in the above embodiment, an example has been described in which the first scanner 60a is provided upstream of the second scanner 60b in the transport direction of the paper P, but the present invention is not limited to this. For example, the first scanner 60a may be provided downstream of the second scanner 60b in the transport direction of the paper P.

In addition, in the above embodiment, an example has been described in which the first scanner 60a reads the image formed on the paper P from the back side of the paper P, but the present invention is not limited to this. For example, if the first scanner 60a is not used to check for misalignment between the front and back of the image formed on the paper P, it may read the image formed on the paper P from the front side of the paper P.

In addition, in the above embodiment, an example has been described in which the second scanner 60b reads the image formed on the paper P from the front side of the paper P, but the present invention is not limited to this. For example, the second scanner 60b may read the image formed on the paper P from the back side of the paper P.

In addition, in the above embodiment, an example has been described in which the image reading device 3 is provided with the first scanner 60a, the second scanner 60b, and the spectrophotometer 70, but the present invention is not limited to this. For example, the image reading device 3 does not have to be provided with the spectrophotometer 70.

In the above embodiment, an example has been described in which the control unit 123 provided in the image forming device 2 executes the calibration process, but the present invention is not limited to this. For example, a control unit (not shown) provided in the image reading device 3 may execute the calibration process. In this case, the control unit provided in the image reading device 3 corresponds to the "calibration processing unit," "reading result correction unit," and "color value correction unit" of the present invention.

Furthermore, the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted in a limiting manner based on these. In other words, the present invention can be implemented in various forms without departing from its gist or main features.

REFERENCE SIGNS LIST 1 Paper feed device 2 Image forming device 3 Image reading device 4 Paper discharge device 20, 50 Paper transport section 60a First scanner 60b Second scanner 70 Spectrophotometer 80a First backing 80b Second backing 80c Third backing 100 Image forming system 123 Control section 200, 202, 204, 206, 208, 210 Patch image P Paper

Claims (7)

a first image reading unit that reads patch images formed on a transparent recording medium for each of a plurality of colors including each of the colors CMYK, a white background, and a white image forming color ;
a first backing portion that faces the first image reading portion via a transport path along which the recording medium is transported and that constitutes a first opposing surface having one of white and black;
a second image reading unit that is disposed downstream of the first image reading unit in a conveying direction of the recording medium and that reads the patch image formed on the recording medium;
a second backing portion that faces the second image reading portion across the transport path and constitutes a second facing surface having the other of white and black;
a calibration processing unit that performs a calibration process so that the gradation values of the patch images read by the first and second image reading units become target gradation values;
Equipped with
the calibration processing unit calculates a transparency of the patch image formed with a white background color based on the reading results of the first and second image reading units, and performs a calibration process so that the calculated transparency degree becomes a target degree.
Image reading device. The target degree is preset.
2. The image reading device according to claim 1 . a first image reading unit that reads patch images formed on a transparent recording medium for each of a plurality of colors from a back side of the recording medium;
a first backing portion that faces the first image reading portion via a transport path along which the recording medium is transported and that constitutes a first opposing surface having a black color;
a second image reading unit that is disposed downstream of the first image reading unit in a conveying direction of the recording medium and that reads the patch image formed on the recording medium from a front side of the recording medium;
a second backing portion that faces the second image reading portion across the transport path and that constitutes a second facing surface having a white color;
Equipped with
the first image reading unit reads the patch image formed with a white color for image formation or a white color for a base;
the second image reading unit reads the patch image formed in each of the colors of CMYK or in a white background;
Image reading device. a read result correction unit that corrects the read result of the first image reading unit according to transparency information that indicates the transparency of the recording medium;
4. The image reading device according to claim 3 . the transparency information is generated based on a result of reading the recording medium by the first image reading unit;
5. The image reading device according to claim 4 . the transparency information is generated in advance according to the type of the recording medium;
5. The image reading device according to claim 4 . a colorimetric unit that measures the color of the patch image formed on the recording medium;
a color value correction unit that corrects color values calculated based on the reading result of the second image reading unit by using the color measurement result of the color measurement unit;
The image reading device according to any one of claims 3 to 6, further comprising: