JP5429000B2 - Color measuring device, color measuring method, and color measuring program - Google Patents

Description

  The present invention relates to a color measurement device, a color measurement method, and a color measurement program that perform color measurement based on reflectance.

  Conventionally, in color matching such as calibration, a spectral characteristic of reflectance of a colorimetric object is detected by a sensor, and a colorimetric value is calculated based on this reflectance. For example, the colorimetric value can be obtained by multiplying the spectral intensity of an arbitrary light source, the reflectance of the colorimetric object, and the color matching function. In addition, in order to obtain a colorimetric value with high accuracy, a sensor capable of detecting spectral characteristics in the entire visible wavelength range is required as the sensor.

  Since the above-described sensor capable of detecting the visible wavelength range in a wide range is expensive, an apparatus for obtaining a colorimetric value by combining a sensor group having high sensitivity with respect to an arbitrary wavelength range is disclosed. (For example, see Patent Documents 1 and 2.)

JP 2008-180742 A Japanese Patent Laid-Open No. 11-211673

  When a sensor having high sensitivity with respect to any wavelength described above is used in combination, the detection result may vary depending on the background color and material of the color measurement target or the structure on which the color measurement target is placed. For example, when a patch is drawn on paper with a white background color, the reflection component obtained by detecting this patch includes a reflection component due to ink, a reflection component due to the background (paper), and further reflected after passing through the paper. Consists of the sum of reflection components. For this reason, if the reflection components other than the reflection component due to ink differ depending on various conditions, different reflectances are detected even when patches of the same color are detected, making it difficult to obtain uniform colorimetric values. .

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a color measurement device capable of obtaining uniform color measurement values while taking costs into consideration.

  In order to solve the above-described problem, the present invention provides a colorimetric device that performs colorimetry using a colorimetric patch that includes a background portion and a plurality of patches in which arbitrary gradations are expressed. A plurality of sensors having high sensitivity with respect to a wavelength region, detecting means for detecting the reflectance of the base portion and the reflectance of each patch, and the relative of each patch based on the reflectance of the base portion And a colorimetric value calculation means for calculating a colorimetric value of each patch based on a typical reflectance.

In the invention configured as described above, the detection means includes a plurality of sensors having high sensitivity with respect to an arbitrary wavelength range, and when measuring a colorimetric patch, the reflectance of the base portion and each patch are measured. To detect the reflectance. Then, the colorimetric value calculation means calculates the colorimetric value of each patch based on the relative reflectance of each patch based on the reflectance of the background portion.
Here, the reflectance of each patch includes the reflection component of the ground portion, and the reflectance of the ground portion includes the reflection component from the paper and the reflection component reflected after passing through the paper. . Therefore, by calculating the colorimetric values of each patch using the relative relationship between the ground portion and the reflectance of each patch, it is possible to cancel the influence of components other than the reflectance due to ink, and uniform measurement. A color value can be obtained.

The combination of the sensors for measuring the colors of the patches may be associated in advance.
In the invention configured as described above, the patch can be colorimetrically measured with a simpler configuration by preliminarily defining the relationship between the relative reflectance and the colorimetric value.

  Further, as an example of a method for obtaining a colorimetric value from relative reflectance, the colorimetric value calculation means records data defining a relationship between the calculated relative reflectance and colorimetric value. The colorimetric value may be obtained based on this data.

  Further, as an example of a method for obtaining a colorimetric value from the relative reflectance, the colorimetric value calculation means calculates a spectral reflectance in each patch by interpolating the calculated relative reflectances. The colorimetric value may be obtained based on the calculated spectral reflectance.

Then, as an example of a method for obtaining the reflectance of the background portion, a configuration may be adopted in which the background portion in the vicinity of the four patches is detected and the average value of the detected values is obtained.
In the invention configured as described above, it is possible to obtain a more uniform colorimetric value by absorbing variations in the reflectance of the base portion.

  The present invention is not limited only to the color measurement device, but can also be applied to a color measurement method and a color measurement program to which the present invention is applied.

2 is a block diagram illustrating a configuration of a host PC 10. FIG. 4 is a block diagram for explaining functions of a host PC 10. FIG. 2 is a block diagram illustrating a configuration of a printer 20. FIG. It is a schematic diagram for demonstrating the colorimetry method concerning this embodiment. It is a figure which shows the patch for colorimetry concerning this embodiment. It is a flowchart explaining the flow of the calibration concerning this embodiment. It is a figure for demonstrating the detection of reflectance Rp ((lambda)). It is a figure which shows the colorimetric value conversion table MT concerning this embodiment. It is a figure which shows the spectral reflectance produced by host PC10 concerning 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described in the following order.
1. First embodiment:
1.1. Configuration of the color measuring device:
1.2. About the color measurement method:
1.3. Calibration flow:
2. Second embodiment:
3. Other embodiments:

1. First embodiment:
1.1. Configuration of the color measuring device:
A first embodiment in which a colorimetric device according to the present invention is embodied will be described below with reference to the drawings. In the first embodiment, the color measurement device is realized as a system including the host PC 10 and the printer 20.

  FIG. 1 is a block diagram illustrating the configuration of the host PC 10. FIG. 2 is a block diagram for explaining functions of the host PC 10. FIG. 3 is a block diagram illustrating the configuration of the printer 20.

  The host PC 10 includes a CPU 11, a RAM 12, a ROM 13, an HDD 14, various interfaces (GIF, VIF, IIF) 15 to 17, and a bus 18, and integrated control via the bus 18 by the CPU 11. Is done. Further, the host PC 10 realizes the functions of the calibration execution module M1 and the driver module M2 by executing the program data PD recorded in the HDD 14.

  The GIF (general-purpose interface) 15 is an interface conforming to the USB standard, for example, and transmits data output from the host PC 10 to the printer 20 by connecting to the printer 20. A VIF (video interface) 16 is connected to the display 40 to display an image on the display 40. The IIF (input device interface) 17 is connected to the keyboard 50a and the mouse 50b, and causes the host PC 10 to input operation inputs obtained by operating the keyboard 50a and the mouse 50b.

  In addition to the program data PD, the HDD 14 includes, as data for performing printing processing or calibration, a color conversion table LUT, a correction table AT, a colorimetric value conversion table MT, standard data SD, and patch data CPD. And are recorded.

  The calibration execution module M1 includes functions of a setting management unit M1a, a sensor selection unit M1b, a colorimetry control unit M1c, and a correction data creation unit M1d, and controls calibration executed by the host PC 10 and the printer 20. .

.
The setting management unit M1a manages parameters corresponding to various settings in calibration, and performs various settings in calibration according to the parameters.

  The sensor selection unit M1b selects a combination of sensors used when measuring the colorimetric patch. In the present embodiment, as will be described later, an arbitrary patch P in the colorimetric patch and a combination of sensors that measure the color of the patch P are associated in advance, and the sensor selection unit M1b performs colorimetry on the predetermined patch P. When the target is selected, a signal for designating a combination of sensors corresponding to the patch P is output to the printer 20.

  The color measurement control unit (color measurement value calculation means) M1c controls the color measurement processing executed in the calibration in an integrated manner. That is, the printer 20 detects the reflectance Rp (λ) of the colorimetric patch, and obtains a colorimetric value for each patch based on the detection result.

  The correction data creation unit M1d corrects each value of the correction table AT based on the color measurement result. In the correction table AT, the relationship between the ink combination (input ink amount gradation value) set using the color conversion table LUT and the ink combination (output ink amount gradation value) transmitted to the printer 20 is shown. It is a table that prescribes. Therefore, the correction data creation unit M1d executes calibration by correcting the output ink gradation value of the correction table AT based on the color measurement result.

  The driver module M2 has functions of a size conversion unit M2a, a color conversion unit M2b, a halftone unit M2c, and a print data generation unit M2d, and controls printing processing in the host PC 10.

  The size conversion unit M2a performs a pixel number conversion process on the image data ID to be printed so that the subsequent part can be processed. The color conversion unit M2b converts the image data ID into ink amount data IID based on the color conversion table LUT. Here, in the color conversion table LUT, the color elements (R, G, B) constituting the image data ID and the CMYK ink amounts ejected by the printer 20 are recorded in association with each other, and the ink amount data IID is recorded. Is data indicating the ink amount (combination of CMYK inks) expressing the gradation indicated by the color element of the image data ID. Then, the halftone portion M2c acquires a halftone image obtained by converting the presence / absence of ink recording and the ink amount for each pixel using the dither method or the error diffusion method from the ink amount data IID. The print data generation unit M2d converts the halftone image into band-unit print data that can be processed by the printer 20.

  The printer 20 includes an ASIC 21, a print head 22, an ejection control circuit 24, a print head drive control circuit 25, a paper transport mechanism 27, a GIF 28, and a bus 29, and the ASIC 21 passes the bus 29. Integrated control is performed. In addition to the above configuration, the printer 20 according to the present embodiment includes a color measurement head (detection unit) 23 and a color measurement head drive control circuit 26, and performs color measurement on the patch P printed on paper. Color measurement can be performed by the head 23.

  The print head 22 is a mechanism that reciprocates in the main scanning direction under the control of the print head drive control circuit 25. The print head 22 is controlled by the discharge control circuit 24 and is supplied from each ink cartridge (C, M, Y, K) (not shown). The supplied ink is discharged onto the printing paper. The GIF 28 establishes communication with the host PC 10 by connecting to the GIF 15 of the host PC 10.

  The color measurement head 23 according to the present embodiment is attached to the print head 22 and moves in accordance with the reciprocation of the print head 22 in the main scanning direction under the control of the color measurement head drive control circuit 26. The colorimetric head 23 includes three sensors 23a, 23b, and 23c having different sensitivity in the wavelength range to be detected. Here, the sensor 23a is a sensor having the highest detection sensitivity in the high wavelength region, the sensor 23b is a sensor having the highest detection sensitivity in the intermediate wavelength region, and the sensor 23c has the highest detection sensitivity in the low wavelength region. It is a sensor. Therefore, each sensor 23a, 23b, 23c can detect the reflectance R (λ) in each wavelength region under an arbitrary colorimetric condition.

  The paper transport mechanism 27 is a mechanism for transporting paper to be printed, a transport roller (not shown), a transport belt stretched between the transport rollers, and a platen PR on which a paper is placed when printing is performed. It is configured with. In addition, the platen PR has irregularities formed on the mounting surface with which the transported paper comes into contact, and reduces friction with the transported paper.

1.2. About the color measurement method:
FIG. 4 is a schematic diagram for explaining the color measurement method according to the present embodiment. FIG. 5 is a diagram showing a colorimetric patch according to the present embodiment. Hereinafter, the color measurement method according to the present embodiment will be described with reference to FIGS. 4 and 5.

  The color measurement patch is an image printed on a sheet based on the patch data CPD, and includes a base area Aw where no ink is recorded and a patch area Ap where the patch P is formed. The patch area Ap is configured by including a plurality of patch rows in which patches P formed so as to have a predetermined ink amount gradation with an arbitrary ink amount are arranged in series. Here, each patch P has its ink amount gradation set so as to express the color value defined by the standard data SD. The base region Aw is a region where the patch P in the patch region Ap is not formed, and is formed between adjacent patches P (that is, gaps positioned on the top, bottom, left, and right of the patch P).

  In the color measurement method using the above-described color measurement patch, in this embodiment, the color measurement value of the patch is obtained based on the ratio between the reflectance of the base area Aw and the reflectance of the patch area Ap. As shown in FIG. 4, the reflection component of each patch is the sum of the reflection component of the ink, the reflection component of the paper, and the reflectance that passes through the paper and is reflected by the platen PR and the like. Further, each reflection component also changes depending on the case where the background color of the paper changes due to the material or the like, or the shape of the platen PR. Therefore, the reflectance Rp (λ) detected by the colorimetric head 23 may vary even with patches having the same ink gradation.

  Therefore, in the present embodiment, when the colorimetric value in any patch P is detected, the ratio Rre of the reflectance Rp (λ) detected in the patch area Ap and the reflectance Rw (λ) detected in the base area Aw is used as the basis. By obtaining the colorimetric value, the variation of each reflection component is absorbed so that a uniform colorimetric value can be calculated.

1.3. Calibration flow:
FIG. 6 is a flowchart for explaining the flow of calibration according to the present embodiment. Hereinafter, calibration using the color measurement device according to the present embodiment will be described with reference to FIG.

  When the conditions for executing calibration are established in the host PC 10, in step S1, the driver module M2 records the patch data CPD in the RAM 12, and changes the patch data CPD to print data.

  In step S2, the driver module M2 prints an arbitrary patch P on a sheet using the converted print data.

  In step S3, the sensor selection unit M1b selects a combination of the sensors 23a, 23b, and 23c corresponding to the patch P to be detected from the sensors 23a, 23b, and 23c included in the color measurement head 23. For example, the combination of the patch P and the sensor that detects the reflectance Rp (λ) of the patch P is set in advance by a table or the like, and the sensor selection unit M1b uses the combination of the sensors 23a, 23b, and 23c based on this table. Judging. Here, the combination of the patch P and the sensor may be set according to the characteristic of the reflection component of the patch P to be detected (for example, the peak wavelength value). With the above configuration, the colorimetric value can be obtained with a simpler configuration.

  In step S4, the colorimetry control unit M1c causes the printer 20 to detect the reflectance Rp (λ) of an arbitrary patch P by the selected combination of sensors.

  FIG. 7 is a diagram for explaining the detection of the reflectance Rp (λ). For example, assume that the reflectance Rp (λ) of an arbitrary patch P is detected based on the combination of the sensors 23a, 23b, and 23c. At this time, as an example of detecting the reflectance Rp (λ), the area S of the region connected by interpolating the detection values (de1, de2, de3) detected by the sensors 23a, 23b, and 23c is defined as the reflectance Rp (λ). You may detect as.

In step S5, the colorimetry control unit M1c causes the printer 20 to detect the reflectance Rw (λ) of the base region Aw. As an example of a method for detecting the reflectance Rw (λ) of the base region Aw, the average value of the reflectances in the vicinity of the patch P around the patch P is calculated as the reflectance Rw (λ) based on (Equation 1) shown below. You may do it. By adopting the above configuration, it is possible to cancel variations in the background color and obtain uniform colorimetric values.
Rw (λ) = (Rwf (λ) + Rwb (λ) + Rwr (λ) + Rwl (λ)) / 4 (Formula 1)
Where Rwf (λ) is the reflectivity of the base region Aw in the upper part in FIG. 4, Rwb (λ) is the reflectivity of the base region Aw in the lower part of FIG. 4, and Rwr (λ) is the right part of the base region Aw in FIG. , Rwl (λ) is the reflectance of the left portion of FIG. 4 of the base region Aw.

In step S6, the colorimetry control unit M1c shows a ratio Rre between the reflectance Rw (λ) of the base region Aw detected in step S5 and the reflectance Rp (λ) of the patch region Ap (Equation 2) And a colorimetric value is obtained from the calculated ratio Rre.
Rre = Rp (λ) / Rw (λ) (Formula 2)

  FIG. 8 is a diagram showing a colorimetric value conversion table MT according to the present embodiment. In the colorimetric value conversion table MT, a reflectance ratio Rre and a colorimetric value corresponding to each value of the reflectance ratio Rre are recorded in association with each other. Specifically, the reflectance ratio Rre and the ink amount gradation are recorded in association with each other in the colorimetric value conversion table MT, and the colorimetric control unit M1c is obtained from the colorimetric value conversion table MT. An ink amount gradation corresponding to the ratio Rre is acquired. The colorimetric value conversion table MT is set for each combination of the sensors 23a, 23b, and 23c.

  If the color measurement has not been completed for all the patches P (step S7: NO), the color measurement control unit M1c changes the patch P to be measured (step S8), and repeats the processing from step S2 to step S6. .

  When the colorimetry has been completed for all the patches P (step S7: YES), in step S9, the correction data creation unit M1d compares the colorimetric values obtained in step S6 with the standard data SD, If there is a difference, the correction table AT is corrected. By correcting the correction table AT, the output ink gradation is corrected and calibration is executed.

  As described above, in the present embodiment, when measuring the colorimetric patch, the reflectance of the background portion and the reflectance of each patch are detected, and the relative of each patch based on the reflectance of the background portion is detected. The calorimetric value of each patch is calculated based on the typical reflectance. For this reason, it is possible to cancel the influence of components other than the reflectance due to the ink, and a uniform colorimetric value can be obtained.

2. Second embodiment:
In the first embodiment described above, the relationship between the reflectance ratio Rre and the colorimetric value is defined in advance. However, when the colorimetric head 23 has a large number of sensors, the discrete reflectance detected by each sensor is determined. May be interpolated to obtain the spectral reflectance characteristic, and the colorimetric value in an arbitrary patch may be obtained from the spectral reflectance characteristic.

  FIG. 9 is a diagram showing the spectral reflectance created by the host PC 10 according to the second embodiment. In FIG. 9, the relative reflectance (ratio Rre) at each wavelength (wl1 to wl7) is detected by seven sensors having different wavelength ranges to be sensed. Therefore, the colorimetric control unit M1c calculates the ratio Rre of the detected discrete reflectance and the reflectance of the ground area Aw, and equalizes the spectral reflectance in an arbitrary patch P by interpolating each ratio Rre. The value is calculated.

Here, when the colorimetric values are values (X, Y, Z) in the XYZ color system, the colorimetric values can be calculated by the following (Equation 3).
X = ΣS (λ) · Rp (λ) · x (λ)
Y = ΣS (λ) · Rp (λ) · y (λ) (Formula 3)
Z = ΣS (λ) · Rp (λ) · z (λ)
Note that Σ is the sum of the wavelengths λ in the visible light range of 380 nm to 750 nm, S (λ) is the spectral intensity at an arbitrary light source, and x (λ), y (λ), z (λ) are color matching functions.

  In FIG. 9, since the area obtained by interpolation (the area surrounded by the slanted line and the solid line in the figure) is the spectral reflectance Rp (λ), this area value is substituted into the above (Equation 3) to obtain an arbitrary value. Colorimetric values (X, Y, Z) in the patch P can be simply calculated. With the above configuration, although the number of sensors increases, it becomes possible to reduce the cost compared to the sensor for detecting all wavelengths, and the colorimetric values are changed to the colorimetric values according to the first embodiment. Compared to this, it is possible to obtain with higher accuracy. The second embodiment has been described above.

3. Other embodiments:
There are various embodiments of the present invention.
The system configured by the host PC 10 and the printer 20 as the color measuring device is an example, and the function according to the present embodiment may be realized by the printer 20 alone. In this case, the ASIC 21 of the printer 20 implements the functions of the calibration execution module M1 and the driver module M2 in the host PC 10.

  Further, the colorimetric patch may have any arrangement configuration as long as it includes the base area Aw and the patch area Pw, and is not limited to the one described in the present embodiment.

  Needless to say, the present invention is not limited to the above embodiments. That is, the mutually replaceable members and configurations disclosed in the above embodiments are applied by changing their combinations as appropriate. The members and configurations disclosed in the examples can be replaced with the members and configurations interchangeable with each other as appropriate, and the combination thereof is changed and applied. It is one of the present invention that a person skilled in the art can appropriately substitute the members and configurations that can be assumed as substitutes for the members and configurations disclosed in the above-described embodiments based on the above, and change the combination to apply. It is disclosed as an example.

  DESCRIPTION OF SYMBOLS 10 ... Host PC, 11 ... CPU, 12 ... RAM, 13 ... ROM, 14 ... HDD, 15 ... GIF, 16 ... VIF, 17 ... IIF, 18 ... Bus, 20 ... Printer, 21 ... ASIC, 22 ... Print head, 23 ... Color measuring head, 23a, 23b, 23c ... Sensor, 24 ... Discharge control circuit, 25 ... Print head drive control circuit, 26 ... Color measurement head drive control circuit, 27 ... Paper transport mechanism, 28 ... GIF, 29 ... Bus 40, display, 50a, keyboard, 50b, mouse, M1, calibration execution module, M1a, setting management unit, M1b, sensor selection unit, M1c, colorimetry control unit, M1d, correction data creation unit, M2 driver module M2a: Size conversion unit, M2b: Color conversion unit, M2c: Halftone unit, M2d: Print data generation unit

Claims (7)

A colorimetric device that performs colorimetry using a colorimetric patch including a background portion and a plurality of patches in which arbitrary gradations are expressed,
A plurality of sensors having high sensitivity with respect to an arbitrary wavelength region, and detecting means for detecting the reflectance of the base portion and the reflectance of each patch;
A colorimetric value calculating means for calculating a colorimetric value of each patch based on a relative reflectance of each patch based on the reflectance of the base portion. .   The colorimetric apparatus according to claim 1, wherein the combination of the sensors that measure the color of each patch is associated in advance. The colorimetric value calculation means includes:
3. The data defining the relationship between the calculated relative reflectance and the colorimetric value is recorded, and the colorimetric value is obtained based on this data. The colorimetric device according to any one of the above. The colorimetric value calculation means includes:
Interpolating the calculated relative reflectances to calculate the spectral reflectance in each patch,
The colorimetric apparatus according to claim 1, wherein a colorimetric value is obtained based on the calculated spectral reflectance.   5. The measurement according to claim 1, wherein the reflectivity of the base portion is obtained by detecting a base portion in the vicinity of four of the patch and calculating an average value of the detected values. Color device. A colorimetric method for performing colorimetry using a colorimetric patch comprising a background portion and a plurality of patches expressing arbitrary gradations,
A detection step of detecting the reflectance of the base portion and the reflectance of each patch by a plurality of sensors having high sensitivity with respect to an arbitrary wavelength range,
A colorimetric value calculating step of calculating a colorimetric value of each patch based on a relative reflectance of each patch based on the reflectance of the base portion. . A colorimetry program that realizes a function of causing a computer to acquire a colorimetric value of each patch using a colorimetric patch comprising a background portion and a plurality of patches expressing arbitrary gradations,
A detection function for detecting the reflectance of the base portion and the reflectance of each patch through a plurality of sensors having high sensitivity with respect to an arbitrary wavelength range;
A colorimetry program for causing a computer to realize a colorimetric value calculation function for calculating a colorimetric value of each patch based on a relative reflectance of each patch based on the reflectance of the base portion.

Images