JP2012004775A - Image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a change in the spectral sensitivity characteristic of an image reading device when replacing the CCD imaging element or the illumination light source of a scanner unit and readjusting a color correction parameter value.SOLUTION: When a CCD imaging element (or the illumination light source) of a scanner unit 100 is replaced and adjustment of the parameter value is instructed, a storage unit 403 (or 404) is rewritten with a patch image signal value extracted from a patch chart read signal. As a result, only a parameter correction amount corresponding to variation in the property of the CCD imaging element (or the illumination light source) calculated by an arithmetic unit 410 (or 411) is updated. Using the parameter correction amount calculated by the arithmetic unit 410, 411, a parameter reference value stored in a storage unit 409 is corrected, and the corrected parameter value is set to a color correction unit 401.

Description

  The present invention provides an image reading apparatus including a scanner unit (image reading unit) that scans an original and outputs an image signal, and a color correction unit that performs color correction processing on the image signal output from the scanner unit. In particular, the present invention relates to a color correction parameter control technique.

  The spectral sensitivity characteristics (color separation characteristics) of a scanner unit (image reading means) that scans and outputs an image signal are the spectral sensitivity characteristics of the CCD image sensor used in the scanner unit, and the spectral emission of the illumination light source. It is determined by characteristics, spectral transmission characteristics such as a lens and an infrared cut filter interposed in the optical path from the document to the CCD image sensor.

  As described above, there are not a few parts in the scanner section that affect the spectral sensitivity characteristics. In particular, the spectral sensitivity characteristics of the CCD image sensor and the spectral radiation characteristics of the illumination light source vary greatly from part to part. Due to such variation in spectral characteristics among components, the variation in spectral sensitivity characteristics of the scanner unit is considerably large. Therefore, in an image reading apparatus, a color for performing color correction processing on an image signal output from the scanner unit is generally used. A correction unit is provided, and the color correction parameter value is appropriately set to compensate for variations in spectral sensitivity characteristics of the scanner unit.

  Examples of related prior art documents include Patent Document 1 and Patent Document 2. In Patent Document 1, a plurality of color correction parameter value candidates are prepared in advance for the purpose of realizing color correction in accordance with the spectral sensitivity characteristics of the scanner unit, and an image signal obtained by reading a reference document with the scanner unit. In addition, color correction parameter value candidates that minimize the error of the result of color correction using the respective color correction parameter value candidates are selected. In Patent Document 2, an image signal obtained by performing color correction processing on an image signal obtained by reading a standard document with a scanner unit using a predetermined color correction parameter value for the purpose of realizing color correction in accordance with variations in spectral sensitivity characteristics of the scanner unit. And a difference value between an image signal obtained by performing color correction using a predetermined color correction parameter value on an image signal obtained by reading a standard document with a scanner unit having a standard spectral sensitivity characteristic, and using the difference value. A predetermined color correction parameter value is corrected.

  Conventionally, in an image reading apparatus, when a component such as a CCD image sensor of a scanner unit (image reading means) is replaced and the color correction parameter value is readjusted, the spectral sensitivity characteristic of the image reading apparatus changes significantly. There was a problem that it was impossible to read the same image as before.

  The object of the present invention is to improve the spectral sensitivity characteristics of conventional image reading devices when the color correction parameter values are readjusted by replacing components such as the CCD image sensor and illumination light source of the scanner unit (image reading means). An object of the present invention is to provide an image reading apparatus in which no significant change occurs.

In order to achieve the above object, an image processing apparatus of the present invention provides:
Image reading means for reading and scanning an original and outputting an image signal;
Color correction means for performing color correction processing of an image signal output from the image reading means;
An image signal value corresponding to each patch on the patch chart is extracted as a patch image signal value from an image signal output by the image reading unit scanning and outputting a predetermined patch chart, and based on the patch image signal value Determining a correction amount of the parameter of the color correction processing (hereinafter referred to as a color correction parameter) according to the variation in spectral characteristics for each of a plurality of replaceable specific parts constituting the image reading unit, Parameter value determining means for setting a value obtained by correcting the reference value of the color correction parameter using the correction amount as a color correction parameter value in the color correction means;
An instruction means for instructing an adjustment related to a specified part (hereinafter referred to as a specified part) among the plurality of specific parts;
When the adjustment of the designated part is instructed by the instruction unit, the parameter value determination unit converts the patch image signal value extracted from the image signal output by the image reading unit by scanning the predetermined patch chart. Based on this, the correction amount of the color correction parameter corresponding to the specified component is updated, and the correction amount of the color correction parameter corresponding to the specific component other than the specified component is not updated.

  For example, a CCD image pickup device and an illumination light source are considered as replaceable specific components constituting the image reading unit. The spectral characteristics of these parts gradually change over time.

  In a conventional image reading apparatus, for example, when a color correction parameter value adjustment operation is performed by exchanging a CCD image pickup device, a color correction parameter is set so as to compensate for a temporal change in spectral emission characteristics of an illumination light source up to that point. The value is corrected. As a result, the spectral sensitivity characteristic of the image reading apparatus is greatly changed from the spectral sensitivity characteristic before the replacement of the CCD image sensor, and there is a problem that the difference in color tone of the read image is conspicuous from that before that. The same problem occurs when the illumination light source is replaced.

  In the image reading apparatus of the present invention, for example, when an instruction is given to use a CCD image sensor as a designated component, the color correction parameter correction amount corresponding to the CCD image sensor based on the patch image signal value extracted from the image signal of the patch chart However, the color correction parameter correction amount corresponding to the illumination light source is not updated, and the temporal change in the spectral radiation characteristics of the illumination light source up to that point is reflected in the color correction parameter correction amount corresponding to the illumination light source. Therefore, the color correction parameter value is corrected so as to compensate only for the variation in the spectral sensitivity characteristics of the replaced CCD image sensor. Therefore, a change in spectral sensitivity characteristic due to replacement of the CCD image sensor can be suppressed as compared with the conventional image reading apparatus. Similarly, when the adjustment is instructed using the illumination light source as the designated component, the change in the spectral sensitivity characteristic of the image reading apparatus accompanying the replacement of the illumination light source can be similarly suppressed.

  As described above, the CCD image pickup device and the illumination light source have been described as examples of the replaceable specific parts. However, it is apparent that the same effect can be achieved when other parts are specified parts.

1 is a block diagram for explaining an outline of a functional configuration of an image reading apparatus of the present invention. FIG. 2 is a schematic diagram illustrating a specific example of a single unit form of the image reading apparatus of the present invention and a scanner unit (image reading means). It is a schematic diagram which shows the example of the display screen of an instruction | indication input part. It is a block diagram for demonstrating the internal structure of a parameter value determination part. It is a schematic diagram which shows an example of a patch chart. It is explanatory drawing of the relational expression of a feature-value and a masking coefficient variation | change_quantity. It is a flowchart for demonstrating the operation | movement of "the whole adjustment" in the case of using the patch chart for CCD adjustment and the patch chart for light source adjustment. It is a flowchart for demonstrating operation | movement of "overall adjustment" when using a patch chart common to CCD adjustment and light source adjustment. 6 is a flowchart for explaining an operation of “CCD adjustment”. 6 is a flowchart for explaining an operation of “light source adjustment”.

  FIG. 1 is a block diagram for explaining an outline of a functional configuration of an image reading apparatus according to the present invention. In FIG. 1, reference numeral 100 denotes a scanner unit (image reading unit) that scans a document and outputs an image signal. The scanner unit 100 has components that affect its spectral sensitivity characteristics (color separation characteristics) (for example, a light source for illuminating a document, an image sensor that receives reflected light from the document, photoelectrically converts it, and outputs an image signal. Etc.) are included in the components.

  In FIG. 1, reference numeral 109 denotes an image signal processing unit that processes an image signal output from the scanner unit 100. In the present invention, the image signal processing unit 109 performs color correction processing that performs color correction processing that compensates for the influence of variations in spectral sensitivity characteristics of the scanner unit 100 on the image signal output from the scanner unit 100. And a parameter value determining unit 402 for determining the value of the color correction processing parameter (color correction parameter). The parameter value determination unit 402 independently sets a color correction parameter correction amount that affects the spectral sensitivity characteristics of the scanner unit 100 according to variations in spectral characteristics of a plurality of replaceable specific parts for each specific part. A value obtained by correcting the reference value of the color correction parameter using the determined color correction parameter correction amount is set in the color correction unit 401 as a color correction parameter value.

  An instruction input unit 110 is used to input an instruction regarding the operation of the image reading apparatus. A control unit 111 controls the scanner unit 100, the image signal processing unit 109, and the instruction input unit.

  The image reading apparatus of the present invention as shown in FIG. 1 can be incorporated into a copying machine, a facsimile apparatus, an apparatus combining these functions, and the like, and such forms are also included in the present invention. In addition, the image reading apparatus of the present invention can take the form of being combined into a single unit, or can take the form of being divided into a plurality of units. As an example of a form divided into a plurality of units, the scanner unit 100, the instruction input unit 110, the functional unit related to the scanner unit 100 and the instruction input unit 110 of the control unit 111 are used as a reading unit, and this reading unit is connected to a computer. The computer can be used to realize the remaining functional parts of the image reading apparatus. Such embodiments are also encompassed by the present invention. Using such a computer, a program for realizing a functional part that is not incorporated in the reading unit, and various types of computers readable such as a semiconductor storage element, a magnetic disk, an optical disk, and a magneto-optical disk in which the program is recorded Recording media are also included in the present invention.

  FIG. 2 is a schematic diagram for explaining a form in which the image reading apparatuses of the present invention are combined into a single unit. FIG. 2 schematically shows a specific example of the scanner unit 100.

  An example of the scanner unit (image reading unit) 100 shown here includes an illumination unit 102 that illuminates an original 101, a first mirror 104 that guides reflected light from the original 101 to a lens 103, a second mirror 105, and a third mirror. 106, an optical filter 107 that removes extraneous light components such as infrared light, and a photoelectric conversion unit 108 that receives the reflected light from the document 101 collected by the lens 103 and converts it into an electrical signal (image signal). ing. The illumination unit 102 includes an illumination light source that is long in the main scanning direction (a direction perpendicular to the paper surface of FIG. 2), and this illumination light source is a replaceable part. Since the spectral sensitivity characteristic of the scanner unit 100 depends on the spectral characteristic (spectral radiation characteristic) of the illumination light source, the illumination light source is one of the replaceable parts that affect the spectral sensitivity characteristic of the scanner unit 100. The photoelectric conversion unit 108 includes a CCD image pickup device that color-separates incident light into R, G, and B components, photoelectrically converts these components, and outputs an image signal. This CCD image pickup device is one of replaceable components whose spectral characteristics (spectral sensitivity characteristics) greatly affect the spectral sensitivity characteristics of the scanner unit 100. The spectral reflection characteristics of the mirrors 104, 105, and 106, the spectral transmission characteristics of the optical filter 107, and the spectral transmission characteristics of the lens 103 also affect the spectral sensitivity characteristics of the scanner unit 100. Here, only the illumination light source and the CCD image sensor are used. Suppose that it is handled as a specific part that is subject to color correction parameter value correction at the time of replacement.

  The illumination unit 102 and the first mirror 104 are mounted on a first carriage (not shown), and the second mirror 105 and the third mirror 106 are mounted on a second carriage (not shown). There is a motor (not shown) for driving these carriages.

  In the scanner unit 100, the main scanning of the document reading scan is electrically performed inside the CCD image sensor of the photoelectric conversion unit 108. The sub-scan of the reading scan is performed by moving the illumination unit 102 mounted on the first carriage to the right in FIG. During the scanning of the original, the second carriage is moved to the right at half the moving speed of the first carriage in order to keep the optical path length from the original reading point to the photoelectric conversion unit 108 constant. Such drive control of the motor for moving the carriage is performed by the control unit 111.

  In FIG. 2, the circuit board on which the control unit 111 is mounted and the circuit board on which the image signal processing unit 109 is mounted are arranged at the bottom of the unit. The operation unit 110 is disposed at the upper right side of the unit. The photoelectric conversion unit 108 also includes means for amplifying an analog image signal output from the CCD image sensor and converting it to a digital image signal, and means for generating a timing signal for driving the CCD image sensor. However, it is not limited to this. For example, a means for converting an analog image signal into a digital image signal can be provided in the image signal processing unit 109, and a timing signal generating means for driving the CCD image sensor can be provided in the control unit 111. It is also possible to use a MOS type image pickup device instead of the CCD image pickup device. Such modified embodiments are also included in the present invention.

  The instruction input unit 110 is configured as a touch panel display, for example. An example of such a display screen of the instruction input unit 110 is shown in FIG. The display screen of the instruction input unit 110 has a hierarchical structure, and FIG. 3A is a standard screen corresponding to the top screen. The control unit 111 causes the instruction input unit 110 to display this standard screen immediately after the image reading apparatus is turned on. When the “full color reading” display 201 or the “monocolor reading” display 202 on the standard screen is touched, the control unit 111 causes the scanner unit 100 to read the document in the “full color reading mode” or the “monocolor reading mode”. The image signal processing unit 109 outputs a full color or mono color image signal.

  When the “color adjustment” display 203 on the standard screen is touched, the control unit 111 shifts to the color adjustment mode and causes the instruction input unit 110 to display a color adjustment screen as shown in FIG. The color adjustment screen includes an “overall adjustment” display 204, a “CCD adjustment” display 205, a “light source adjustment” display 206, and a “return” display 207. When the “return” display 207 is touched, the color adjustment mode ends and the screen returns to the standard screen shown in FIG.

  When it is desired to adjust the color correction parameter value according to the variation in spectral sensitivity characteristics of the CCD image sensor, such as when the CCD image sensor of the photoelectric conversion unit 108 is replaced, a “CCD adjustment” display 205 on the color adjustment screen is displayed. Touch. Touch the “light source adjustment” display 206 on the color adjustment screen when you want to adjust the color correction parameter value according to the dispersion of the spectral characteristics of the illumination light source, such as when the illumination light source of the illumination unit 102 is replaced. To do. That is, the instruction input unit 110 functions as an instruction means for instructing an adjustment related to one specified component (CCD image sensor or illumination light source) selected from a plurality of specific components (here, a CCD image sensor and an illumination light source). . When initial setting of the color correction parameter value is desired at the time of assembling the image reading apparatus or at the time of factory shipment, the “overall adjustment” display 204 on the color adjustment screen is touched.

  Next, the image signal processing unit 109 will be specifically described. FIG. 4 is a block diagram illustrating an example of an internal configuration of the parameter value determination unit 302 of the image signal processing unit 109.

  The color correction unit 401 performs color correction processing for converting an image signal (in this case, an RGB signal) depending on the spectral sensitivity characteristic of the scanner unit 100 input from the scanner unit 100 into a standard image signal. Here, a description will be given on the assumption that the conversion (masking operation) of Expression (1) shown in [Equation 1] is performed as the color correction processing.

  In Expression (1), (Ri, Gi, Bi) is a value (R, G, B component value) of an image signal input from the scanner unit 100 to the color correction unit 401, and (Ro, Go, Bo) is This is the value (R, G, B component value) of the image signal output from the color correction unit 401. The masking coefficients M11 to M33 in the equation (1) correspond to color correction parameters whose values are determined by the parameter value determination unit 402.

  Masking coefficients M11 to M33 optimal for color correction (referred to as reference values) for image signals read by a scanner section having a spectral sensitivity characteristic as a reference (hereinafter referred to as “reference” scanner section) are determined in advance. These reference values are stored in the parameter reference value storage unit 409 in the parameter value determination unit 402. The parameter reference value storage unit 409 is a non-volatile storage unit, and the stored contents are preserved even when the apparatus power is turned off. A known method may be used to determine the reference value of the masking coefficient (color correction parameter).

  The example of the parameter value determination unit 402 shown here is not only the parameter reference value storage unit 409, but also the patch image signal value extraction unit 412, the extracted patch image signal value storage units 403 and 404, and the reference patch image signal value storage unit 405. , 406, feature quantity calculation units 407 and 408, and parameter value correction calculation units 4120 and 411.

  In the figure, elements surrounded by a broken line frame 413 determine a parameter correction amount according to the variation in spectral characteristics (spectral sensitivity characteristics) of the CCD image sensor, and correct the parameter reference value using the parameter correction amount. This means. The element surrounded by the broken line frame 414 is a means for determining a parameter correction amount corresponding to the variation in the spectral characteristics (spectral radiation characteristics) of the illumination light source and further correcting the parameter reference value using the parameter correction amount. It constitutes. Note that the extracted patch image signal value storage units 403 and 404 and the reference patch image signal value storage units 405 and 406 are nonvolatile storage units, and the stored contents are preserved even when the apparatus power is turned off.

  First, the patch image signal value extraction unit 412 and the extracted patch image signal value storage units 403 and 404 will be described. In the color adjustment mode, a document (referred to as a patch chart) in which a plurality of patches having a predetermined spectral reflectance are arranged is read by the scanner unit 100, and an image signal of the patch chart is input. The patch data extraction unit 412 extracts image signal values (patch image signal values) corresponding to the patches on the patch chart. As this patch image signal value, for example, an average value of image signal values (R, G, B component values) at a plurality of positions in the patch is extracted for each patch. Although it is possible to extract an image signal value at a certain point in the patch as a patch image signal value as it is, it is generally preferable to take an average because it is less susceptible to noise.

  When the “CCD adjustment” display 204 is touched in the color adjustment mode, the stored content of the extracted patch image signal value storage unit 403 is rewritten by the patch image signal value extracted by the patch image signal value extraction unit 412. When the “light source adjustment” display 305 is touched, the content stored in the extracted patch image signal value storage unit 404 is rewritten by the extracted patch image signal value. Such an operation is controlled by the control unit 111. Note that separate patch charts may be used for “CCD adjustment” and “light source adjustment”, or a common patch chart may be used (however, it is necessary to unify them).

  In the color adjustment mode, the operation when the “global adjustment” display 206 is touched is slightly different depending on whether different patch charts are used for “CCD adjustment” and “light source adjustment” or a common patch chart is used. The case where separate patch charts are used will be described. First, the patch chart for “CCD adjustment” is read by the scanner unit 100, and the patch image signal value extraction unit 412 extracts patch image signal values for each patch from the image signal. The stored content of the extracted patch image signal value storage unit 403 is rewritten with the patch image signal value. Next, the patch chart for “light source adjustment” is read, the patch image signal value for each patch is extracted from the image signal, and the stored contents of the extracted patch image signal value storage unit 404 are rewritten with the patch image signal value. On the other hand, when a common patch chart is used for [CCD adjustment] and [Light source adjustment], the patch chart is read only once by the scanner unit 100, and the patch image signal value extraction unit 412 uses the patch signal for each patch. The patch image signal value is extracted, and the contents stored in both of the extracted patch image signal value storage units 403 and 404 are rewritten with the patch image signal value. Such an operation is controlled by the control unit 111.

  In the reference patch image signal value storage units 405 and 406, the color adjustment patch chart is read by the “reference” scanner unit, and the patch image signal value for each patch extracted from the image signal is written in advance as the reference patch image signal value. It is. When separate patch charts are used for “CCD adjustment” and “light source adjustment”, the patch image signal value extracted from the image signal obtained by reading the “CCD adjustment” patch chart with the “reference” scanner unit. Is written in advance in the reference patch image signal value storage unit 405 as a reference patch image signal value, and the patch image signal value extracted from the image signal obtained by reading the “light source adjustment” patch chart by the “reference” scanner unit is the reference patch image. It is written in advance in the signal value storage unit 406 as a reference patch image signal value. On the other hand, when a common patch chart is used for “CCD adjustment” and “light source adjustment”, the patch image signal value extracted from the image signal read from the patch chart by the “reference” scanner unit is the reference patch image. The reference patch image signal value is written in advance in both the signal value storage units 405 and 406.

  FIG. 5 shows an example of a patch chart used in the color adjustment mode. In this patch chart example, square patches of predetermined colors 11 to mn are arranged in a grid pattern. However, the shape and arrangement of the patches are not limited to the example of FIG. As described above, separate patch charts may be used for “CCD adjustment” and “light source adjustment”, or a common patch chart may be used. However, in the color adjustment mode of each image processing apparatus, the patch chart read by the scanner unit and the patch chart read by the “reference” scanner unit have the same spectral reflectance of each corresponding patch. In addition, patch charts need to be managed.

  Returning to the description of the parameter value determination unit 402. Based on the patch image signal value stored in the extracted patch image signal value storage unit 403 and the patch image signal value stored in the reference patch image signal value storage unit 405, the feature amount extraction unit 407 A feature amount representing variation in spectral characteristics (spectral sensitivity characteristics) is calculated. For example, a difference between both patch image signal values is obtained, and one or more feature amounts are obtained by multiplying the difference with a predetermined weighting coefficient. That is, the patch image signal value for the i-th patch stored in the extracted patch image signal value storage unit 403 is (Rxi, Gxi, Bxi), and the same i stored in the reference patch image signal value storage unit 405 is used. If the patch image signal value for the i-th patch is (Roi, Goi, Boi), and the weighting coefficient for the j-th feature amount for the i-th patch is (Rij, Gij, Bij), the j-th feature amount is [ It can be calculated by equation (2) shown in Equation 2].

  The weighting coefficients (Rij, Gij, Bij) used in the feature amount calculation unit 407. For example, the CCD image sensor of the “reference” scanner unit is changed to another CCD image sensor within the variation range of the spectral sensitivity characteristic. The patch chart is read in the exchanged state, and the operation of extracting the patch image signal value from the image signal is sequentially performed by exchanging with a plurality of CCD image sensors, and the plurality of sets of patch image signal values obtained in this way The eigenvalue vector obtained by principal component analysis of the difference from the patch image signal value extracted from the image signal obtained by reading the patch chart using the “reference” scanner unit that does not replace the CCD image sensor is used as a weighting coefficient (Rij, Gij). , Bij).

  That is, the patch image signal value for the i-th patch obtained by the “reference” scanner unit that does not replace the CCD image sensor is (Roi, Goi, Boi), and is obtained by replacing the k-th CCD image sensor. If the patch image signal value for the i-th patch is (Rki, Gki, Bki), the characteristic value calculation is performed on the eigenvalue vector obtained by principal component analysis of the difference of the patch data as shown in [Formula 3] below. Can be used as weighting factors for (Rij, Gij, Bij). Note that it is sufficient to use only the upper eigenvalue vector in order to capture the variation in the spectral sensitivity characteristics of the CCD image pickup device, and the number of feature quantities to be calculated can be determined according to the contribution rate and the like.

  The feature quantity creation unit 408 is configured to generate a feature quantity calculation unit based on the patch image signal value stored in the extracted patch image signal value storage unit 404 and the patch image signal value stored in the reference patch image signal value storage unit 406. Similarly to the case of 407, a feature amount representing fluctuation of the spectral characteristics (spectral radiation characteristics) of the illumination light source is calculated by the calculation of the above formula (2). The weighting factors (Rij, Gij, Bij) used at this time can be similarly determined. For example, the illumination light source of the “reference” scanner unit is replaced with another illumination light source within the variation range of the spectral radiation characteristics. The operation of reading the patch chart and extracting the patch image signal value from the image signal is sequentially performed by exchanging with a plurality of illumination light sources, and the plural sets of patch image signal values thus obtained and the illumination light source are not exchanged. The eigenvalue vector obtained by principal component analysis of the difference from the patch image signal value extracted from the image signal obtained by reading the patch chart using the “reference” scanner unit is used as a weighting coefficient (Rij) for calculating the feature quantity regarding the illumination light source. , Gij, Bij).

  The parameter value correction calculation unit 410 calculates each of the above formulas (1) by performing a product-sum operation on the feature amount corresponding to the variation in the spectral sensitivity characteristic of the CCD image sensor calculated by the feature amount calculation unit 407 and a predetermined weighting coefficient. A correction amount for correcting the variation in the spectral sensitivity characteristic of the CCD image sensor with respect to the masking coefficient (color correction parameter) is calculated. That is, when the weighting coefficient for the j-th feature amount of the masking coefficient Mpq is αpqj, the correction amount for the masking coefficient Mpq is expressed by the following equation.

  The weighting coefficient αpqj includes, for example, a masking coefficient value suitable for a reference spectral sensitivity characteristic (that is, a spectral sensitivity characteristic of a “reference” scanner unit) and a CCD image pickup device of the “reference” scanner unit as described above. Prepare multiple sets of masking coefficient values suitable for the state where the CCD image sensor is replaced with another CCD image sensor within the range of variation in spectral sensitivity characteristics. The relationship between the masking coefficient value and the difference between the masking coefficient value suitable for the spectral sensitivity characteristic used as a reference can be obtained by a single regression equation or a multiple regression equation.

  FIG. 6 illustrates the relationship between the feature amount-masking coefficient change amount and the obtained single regression equation.

  Similarly, the parameter value correction calculation unit 411 performs the above formula (1) by multiplying the feature amount according to the variation of the spectral radiation characteristic of the illumination light source calculated by the feature amount calculation unit 408 and a predetermined weighting factor. The correction amount for correcting the variation of the spectral radiation characteristic of the illumination light source for each of the masking coefficients (color correction parameters) is calculated. If the weighting coefficient for the j-th feature amount of the masking coefficient Mpq is αpqj, the correction amount for the masking coefficient Mpq is similarly calculated by the above equation (4). The weighting coefficient αpqj used in this calculation is, for example, a masking coefficient value suitable for the reference spectral sensitivity characteristic (spectral sensitivity characteristic of the “reference” scanner unit) and the illumination light source of the “reference” scanner unit as described above. Multiple sets of masking coefficient values suitable for the state where the light source is replaced with another illumination light source within the dispersion range of the spectral radiation characteristics, and the above-mentioned feature amount and masking coefficient change amount (suitable for the state where the light source is replaced with another light source) The relationship between the masking coefficient value and the difference between the masking coefficient value suitable for the spectral sensitivity characteristic used as a reference can be obtained by a single regression equation or a multiple regression equation.

  The correction amount calculated by the parameter value correction calculation unit 410 and the correction amount calculated by the parameter value correction calculation unit 411 are added to the reference value of each masking coefficient (color correction parameter) read from the parameter reference value storage unit 409. By adding, the reference value of each masking coefficient (color correction parameter) is corrected, and the corrected masking coefficient value is set in the color correction unit 401 and used for the color correction process (masking calculation process). become. That is, assuming that the correction amounts for the masking coefficient Mpq calculated by the parameter value correction calculation units 407 and 408 are Δpq (CCD) and Δpq (light source), the correction value Mpq ′ of the masking coefficient Mpq is expressed by the following equation.

  As described above, the parameter value determination unit 402 independently performs parameter value correction according to variations in spectral characteristics of the CCD image sensor and parameter value correction according to variations in spectral characteristics of the illumination light source. It can be carried out.

  The “total adjustment” in the color adjustment mode is used when initializing the spectral sensitivity characteristics of the image reading apparatus such as when the image reading apparatus is assembled or shipped from the factory. FIGS. 7 and 8 are flowcharts for explaining the operation of “overall adjustment”, respectively, but FIG. 7 shows a flow when separate patch charts are used for “CCD adjustment” and “light source adjustment”. Shows a flow when a common patch chart is used for “CCD adjustment” and “light source adjustment”.

  When the “global adjustment” display 204 is touched on the color adjustment screen of the instruction input unit 110, although not shown, guidance for instruction input related to “global adjustment” is displayed, and the operator needs to follow the guidance. Instruction input can be performed.

  First, referring to FIG. The operator sets a patch chart for “CCD adjustment” in the scanner unit 100 and inputs a reading instruction. The patch chart is read by the scanner unit 100, and the image signal is input to the image signal processing unit 109. The patch image signal value extraction unit 412 sequentially extracts patch image signal values for each patch from the image signal, and the stored contents of the extracted patch image signal value storage unit 403 are sequentially rewritten by the extracted patch image signal values (step 1001). .

  Next, the operator sets a patch chart for “light source adjustment” and inputs a reading instruction. The patch chart is read by the scanner unit 100, and the image signal is input to the image signal processing unit 109. The patch image signal value extraction unit 412 sequentially extracts patch image signal values for each patch from the image signal, and the stored contents of the extracted patch image signal value storage unit 404 are sequentially rewritten by the extracted patch image signal values (step 1002). .

  Next, a feature amount representing a variation in spectral sensitivity characteristics of the CCD image sensor is calculated by the feature amount calculation unit 407. In the parameter value correction calculation unit 410, a parameter value correction amount corresponding to the feature amount is calculated, and the correction amount is added to the reference value of the color correction parameter (masking coefficient) read from the reference value storage unit 409. Thus, the color correction parameter value is corrected (step 1003).

  Next, the feature amount calculation unit 408 calculates a feature amount representing variation in the spectral radiation characteristics of the illumination light source. The parameter value correction calculation unit 411 calculates a parameter value correction amount corresponding to the feature amount, and the correction value is added to the corrected color correction parameter (masking coefficient) value by the parameter value correction calculation unit 410. Thus, the color correction parameter value is further modified (step 1004).

  The color correction parameter (masking coefficient) value corrected as described above is set in the color correction unit 401 (step 1005).

  Note that step 1003 may be executed in parallel with step 1002 immediately after step 1001 is completed. Further, step 1003 and step 1004 may be executed in parallel.

  Please refer to FIG. The operator sets a patch chart common to “CCD adjustment” and “light source adjustment” in the scanner unit 100 and inputs a reading instruction. The patch chart is read by the scanner unit 100, and the image signal is input to the image signal processing unit 109. The patch image signal value extracting unit 412 sequentially extracts patch image signal values for each patch from the image signal, and an extracted patch image signal value storage unit 403 and an extracted patch image signal value storage unit 404 based on the extracted patch image signal values. Both stored contents are sequentially rewritten (step 1011).

  When the above processing is completed, the feature amount calculation unit 407 calculates the feature amount representing the variation in the spectral sensitivity characteristics of the CCD image pickup device, and the parameter value correction calculation unit 410 calculates the parameter correction amount according to the feature amount. The correction amount is added to the reference value of the color correction parameter (masking coefficient) read from the reference value storage unit 409, thereby correcting the color correction parameter value (step 1012).

  Next, the feature amount calculation unit 408 calculates a feature amount representing the variation in the spectral radiation characteristics of the illumination light source, and the parameter value correction calculation unit 411 calculates a parameter value correction amount according to the feature amount. Is added to the corrected color correction parameter (masking coefficient) value by the parameter value correction calculation unit 410 to further correct the color correction parameter value (step 1013).

  The color correction parameter (masking coefficient) value corrected as described above is set in the color correction unit 401 (step 1014). Note that step 1012 and step 1013 may be executed in parallel.

  “CCD adjustment” or “light source adjustment” in the color adjustment mode is used when the CCD image pickup device or illumination light source of the scanner unit 100 of the image reading apparatus is replaced. FIG. 9 is a flowchart for explaining the operation of “CCD adjustment”. FIG. 10 is a flowchart for explaining the operation of “light source adjustment”. When the “CCD adjustment” display 205 or the “light source adjustment” display 206 is touched on the color adjustment screen of the instruction input unit 110, although not shown, guidance for inputting instructions related to “CCD adjustment” or “light source adjustment” is shown. Is displayed, and the operator can input necessary instructions according to the guidance.

  Please refer to FIG. When the CCD image pickup device of the scanner unit 100 is replaced, the operator sets a patch chart for “CCD adjustment” (or a common patch chart when using a common patch chart) in the scanner unit 100 and issues a reading instruction. input. The patch chart is read by the scanner unit 100, and the image signal is input to the image signal processing unit 109. The patch image signal value extraction unit 412 sequentially extracts patch image signal values, and the stored contents of the extracted patch image signal value storage unit 403 are sequentially rewritten by the extracted patch image signal values (step 1021).

  Next, a feature amount representing a variation in spectral sensitivity characteristics of the CCD image sensor is calculated by the feature amount calculation unit 407, and a parameter correction amount corresponding to the feature amount is calculated by the parameter value correction calculation unit 410. Is added to the reference value of the color correction parameter (masking coefficient) read from the reference value storage unit 409, thereby correcting the color correction parameter value (step 1022).

  Next, the feature amount calculation unit 408 calculates a feature amount representing the variation in the spectral radiation characteristics of the illumination light source, and the parameter value correction calculation unit 411 calculates a parameter correction amount according to the feature amount. Then, the color correction parameter value is further corrected by being added to the corrected color correction parameter (masking coefficient) value by the parameter value correction calculation unit 411 (step 1023). Note that step 1022 and step 1023 may be executed in parallel.

  The color correction parameter (masking coefficient) value corrected as described above is set in the color correction unit 401 (step 1024).

  As described above, in the case of “CCD adjustment”, the stored content of the extracted patch image signal value storage unit 403 is rewritten by the patch image signal value extracted from the image signal of the patch chart. The color correction parameter correction amount calculated in 410 is updated. On the other hand, since the stored content of the extracted patch image signal value storage unit 404 is not rewritten, the color correction parameter correction amount calculated by the parameter value correction calculation unit 411 in step 1023 is calculated before the CCD image sensor replacement. It is the same as the correction amount and is not updated. That is, the color correction parameter value according to the variation in the spectral radiation characteristic of the illumination light source at that time is substantially re-corrected according to the variation in the spectral sensitivity characteristic of the replaced CCD image sensor. The value is not re-corrected. Therefore, the temporal change in the spectral radiation characteristic of the illumination light source from the time point when the “global adjustment” or “light source adjustment” before the time point is performed is not reflected in the corrected color correction parameter value, and thus the CCD imaging Changes in the spectral sensitivity characteristics of the image reading apparatus accompanying element replacement are suppressed.

  Please refer to FIG. When the illumination light source of the scanner unit 100 is replaced, the operator sets a “light source adjustment” patch chart (or a common patch chart when a common patch chart is used) in the scanner unit 100 and inputs a reading instruction. To do. The scanner unit 100 scans and reads the patch chart, and the image signal is input to the image signal processing unit 109. The patch image signal value extraction unit 412 sequentially extracts patch image signal values for each patch from the image signal, and the stored contents of the extracted patch image signal value storage unit 404 are sequentially rewritten with the extracted patch image signal values (step). 1031).

  Next, a feature amount representing the variation in spectral sensitivity characteristics of the CCD image sensor is calculated by the feature amount calculation unit 407, and a color correction parameter correction amount corresponding to the feature amount is calculated by the parameter value correction calculation unit 410. The correction amount is added to the reference value of the color correction parameter (masking coefficient) read from the reference value storage unit 409, thereby correcting the color correction parameter value (step 1032).

  Next, the feature amount calculation unit 408 calculates the feature amount representing the variation in the spectral radiation characteristics of the illumination light source, and the parameter value correction calculation unit 411 calculates the color correction parameter correction amount according to the feature amount, and the correction. The color correction parameter value is further corrected by adding the amount to the corrected color correction parameter (masking coefficient) value by the parameter value correction calculation unit 410 (step 1033).

  The color correction parameter (masking coefficient) value corrected as described above is set in the color correction unit 401 (step 1034). Note that step 1032 and step 1033 may be executed in parallel.

  As described above, in the case of “light source adjustment”, the stored content of the extracted patch image signal value storage unit 404 is rewritten by the patch image signal value extracted from the image signal of the patch chart. The color correction parameter correction amount calculated by 411 is updated. On the other hand, since the stored content of the extracted patch image signal value storage unit 403 is not rewritten, the color correction parameter correction amount calculated by the parameter value correction calculation unit 410 in step 1032 is the correction calculated before the illumination light source replacement. It is the same as the quantity and is not updated. That is, the color correction parameter value corresponding to the variation in the spectral sensitivity characteristic of the CCD image sensor at that time is substantially re-corrected according to the variation in the spectral radiation characteristic of the replaced illumination light source. The value is not re-corrected. Therefore, the temporal change in the spectral sensitivity characteristic of the CCD image sensor from the time point when the “global adjustment” or “CCD adjustment” before the time point is performed is not reflected in the corrected color correction parameter value. A change in spectral sensitivity characteristics of the image reading apparatus accompanying the replacement of the light source is suppressed.

  Note that since the stored contents of the extracted patch image signal value storage unit 404 are not rewritten in step 1021 of FIG. 9, the color correction parameter correction amount calculated by the parameter value correction calculation unit 411 in step 1023 is the value before the CCD image sensor replacement. And no different. Further, since the stored content of the extracted patch image signal value storage unit 403 is not rewritten in step 1031 of FIG. 10, the color correction parameter correction amount calculated by the parameter value correction calculation unit 410 in step 1032 is the same as that before the illumination light source replacement. does not change. Therefore, if a non-volatile storage unit for storing the color correction parameter correction amounts calculated by the parameter value correction calculation units 410 and 411 is provided, it is not necessary to perform the feature amount and correction amount calculation processing in steps 1023 and 1032. . It is also possible to combine the extracted patch image signal value storage units 403 and 404 into one (however, when using the “CCD adjustment” patch chart and the “light source adjustment” patch chart, the extracted patch image signal value storage is possible). It is necessary to provide the parts 403 and 404 independently). Such modified embodiments are also encompassed by the present invention.

  Further, when a common patch chart is used for “CCD adjustment” and “light source adjustment”, the reference patch image signal value storage units 405 and 406 can be combined into one because the stored contents are the same. Such modified embodiments are also encompassed by the present invention.

  In the embodiment, the color correction unit 401 is configured to perform a single linear masking operation as a color correction process, but includes a masking operation divided into regions (for example, see Patent Document 2) and higher-order terms. A configuration for performing a masking operation or a configuration using a three-dimensional LUT (look up table) can be employed. However, it is necessary to appropriately change the processing content of the parameter value determination unit 402 according to the change of the color correction unit 401.

  In the embodiment, the color correction parameter value correction according to the variation in the spectral characteristics of the CCD image sensor and the illumination light source in the scanner unit 100 can be performed independently. However, other parts that affect the spectral sensitivity characteristics of the scanner unit 100, such as the lens 103, the optical filter 107, the mirrors 104, 105, 106, and all or part of the contact glass on which the document is set, are also subject to the spectral characteristics. It is easy to independently perform color correction parameter value correction according to variations in transmission characteristics or spectral reflection characteristics. Such modifications are also encompassed by the present invention.

  It is also possible to realize functions related to the control of the image signal processing unit according to the embodiment or the modification thereof and the image signal processing unit of the control unit by using hardware resources of the computer, and this aspect is also described in this embodiment. Included in the invention. A program for this purpose is also included in the present invention. The present invention also includes a semiconductor memory element in which such a program is recorded and other various computer-readable recording (storage) media.

100 Scanner unit (image reading means)
DESCRIPTION OF SYMBOLS 102 Illumination part 108 Photoelectric conversion part 109 Image signal processing part 110 Instruction input part 111 Control part 401 Color correction part 402 Parameter value determination part 403,404 Extraction patch image signal value storage part 405,406 Standard patch image signal value storage part 407, 408 Feature value calculation unit 409 Parameter reference value storage unit 410, 411 Parameter value correction calculation unit 412 Patch image signal value extraction unit

Japanese Patent No. 3494924 Japanese Patent No. 4115098

Claims (3)

Image reading means for reading and scanning an original and outputting an image signal;
Color correction means for performing color correction processing on the image signal output from the image reading means;
An image signal value corresponding to each patch on the patch chart is extracted as a patch image signal value from an image signal output by the image reading unit performing scanning scanning of a predetermined patch chart, and based on the patch image signal value Then, for each of a plurality of replaceable specific parts constituting the image reading unit, a correction amount of the color correction processing parameter (hereinafter referred to as a color correction parameter) corresponding to the dispersion of the spectral characteristics is determined. A parameter value determination unit that sets a value obtained by correcting the reference value of the color correction parameter using the correction amount as a color correction parameter value in the color correction unit;
An instruction means for instructing an adjustment related to a specified part (hereinafter referred to as a specified part) among the plurality of specific parts;
When the adjustment of the designated part is instructed by the instruction unit, the parameter value determination unit converts the patch image signal value extracted from the image signal output by the image reading unit by scanning the predetermined patch chart. An image reading apparatus comprising: updating a correction amount of a color correction parameter corresponding to the designated component based on the update amount, and not updating a correction amount of the color correction parameter corresponding to a specific component other than the designated component. The parameter value determining means is stored in a plurality of nonvolatile storage means for storing patch image signal values associated with the plurality of specific parts on a one-to-one basis, and the plurality of nonvolatile storage means. Means for determining a correction amount of a color correction parameter corresponding to each of the plurality of specific components based on the patch image signal value being
When the adjustment of the designated component is instructed by the instruction unit, the parameter value determination unit uses the patch image signal value extracted from the image signal output by the image reading unit scanning and reading a predetermined patch chart. 2. The storage content of the nonvolatile storage means corresponding to the designated part is rewritten, and the storage content of the nonvolatile storage means corresponding to a specific part other than the designated part is not rewritten. The image reading apparatus described.   The image reading apparatus according to claim 1, wherein the plurality of specific parts include at least one of an image sensor that receives reflected light from a document and a light source that illuminates the document.

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