JP2006211100A - Preparation and printing of profile based on colorimetry value under real observation condition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To print a profile after preparing it on the basis of the colorimetry result obtained by automatically measuring a color. <P>SOLUTION: When the profile is prepared which makes image data and a colorimetry value of an output based on the image data correspond to each other, a colorimetry value is acquired by measuring the color of the output result based on the image data at first observation conditions, the colorimetry value obtained by measuring the color in a colorimetry value acquiring process is converted to a colorimetry value when the color of the output result is measured at second observation conditions, and then, the profile is prepared by making the converted colorimetry value and the image data correspond to each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for performing printing based on a profile.

A colorimeter is used to accurately measure the color of an output result by an output device, for example, an output result on a printed matter or a display. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 10-142775

  Conventionally, the colorimetric value has been used on the assumption that the colorimetric result obtained by the colorimeter is accurate. For example, in order to output a desired color in a printing apparatus, a color conversion table is used, and a colorimeter is used when creating this color conversion table. In other words, in the gradation value in the device-dependent color space, for example, the gradation value that specifies the usage amount of the recording material used in the printing apparatus for each color, the color is not output based on this gradation value. Cannot be identified.

  Therefore, a predetermined number of patches are actually printed, and a colorimetric value is obtained by performing colorimetry with a colorimeter. Using this colorimetric value, the gradation value in the device-independent color space and the above recording are recorded. A color conversion table is formed by associating gradation values for each color of the material. Here, the colorimeter measures the color of the patch by specifying the observation conditions, and the colorimetric values are accurate as long as the observation conditions are assumed. The value is not correct. In other words, the conversion result based on the color conversion table is strictly correct only when the printed matter is observed under the condition that matches the observation condition in the colorimeter.

  It is natural that the colorimetric values differ due to different observation conditions, but the measurement is based on the observation conditions measured by the colorimeter and the observation conditions in the environment where the colorimetric object is actually used. When the color values are greatly different, inconvenience occurs when the colorimetric object is actually used. In other words, if the observation conditions for creating the color conversion table and the observation conditions for the observer to observe the printed matter are different, the color is different from the color intended by the creator when creating the color conversion table. I feel it. For example, it is felt that the contrast is lower than the contrast intended by the creator, or the hue is different from the color intended by the creator. In particular, the above-mentioned inconvenience is likely to occur in an output product in which the color appearance is likely to be different due to different observation conditions, for example, an output product by pigment ink.

  In addition, it is only necessary to be able to use a colorimeter that performs colorimetry under observation conditions for actually observing the colorimetric object, but it is inconvenient to measure a large number of colorimetric objects with such a colorimeter. There are many. In other words, the colorimeter includes a colorimeter that can automatically measure a plurality of colorimetric objects and a colorimeter that measures a plurality of colorimetric objects while changing the colorimetric object by human work, In the former, color measurement is performed in a state where the observation conditions are determined in advance, but in the latter, the observation conditions are optional.

Further, when creating the color conversion table, it is almost essential to perform color measurement automatically. That is, in order to create a color conversion table, it is necessary to measure a large number (for example, 1000) of patches, but it is impractical to measure such a large number of patches one by one by human work. Therefore, automatic measurement is almost essential. Therefore, conventionally, it has been difficult to accurately acquire colorimetric values when a large number of colorimetric objects are observed under desired observation conditions.
The present invention has been made in view of the above problems, and an object of the present invention is to create and print a profile based on a color measurement result automatically measured.

  In order to achieve the above object, in the present invention, a colorimetric value obtained when colorimetry is performed under the second observation condition is obtained from the colorimetric value obtained by measuring the output result based on the image data under the first observation condition. Then, a profile is created by associating the acquired colorimetric values with the image data. That is, a profile is created by acquiring colorimetric values under a second observation condition that is different from the first observation condition under which color measurement is actually performed.

  Therefore, it is possible to perform a large number of color measurements under the first observation condition that facilitates a large number of color measurements, and to create a profile based on the color measurement values obtained as a result. Even if it exists, a color measurement can be easily performed and a profile can be created. Further, by setting the observation condition for actually observing the output result as the second observation condition, the profile can be created so that the color is output as intended by the profile creator. Of course, here, the profile only needs to associate the image data with the output colorimetric value based on the image data, and is a color conversion table including a plurality of data associated with gradation values in different color systems. It may be a function that associates gradation values in different color systems, and various configurations can be employed.

  Here, as the observation condition, it is preferable that an observation condition in a colorimeter (a colorimeter including a light source) that performs color measurement using a predetermined light source is the first observation condition. That is, as this color measuring device, there is a color measuring device that automatically measures a large number of color measuring objects. According to this color measuring device, automatic color measurement under the first observation condition is possible. On the other hand, it is preferable that the observation condition in the colorimeter that performs color measurement using an arbitrary light source is the second observation condition. That is, in this colorimeter, generally, the colorimetric objects are set artificially, and when measuring a plurality of colorimetric objects, the colorimetry is performed while sequentially changing the positions of the colorimetric objects.

  Therefore, it is difficult for this colorimeter to automatically measure many colorimetric objects. However, since an arbitrary light source can be used, color measurement can be performed by generating an observation condition for actually observing the output result, for example, a condition close to the observation condition for actually observing the printed matter. Therefore, it is possible to create a profile that faithfully reproduces the colors under the observation conditions when actually observing.

  The colorimetric value conversion means has various configurations as long as the colorimetric value measured under the first observation condition can be converted into the colorimetric value obtained when the output result is measured under the second observation condition. It can be adopted. For example, data for converting a colorimetric value measured under the first observation condition into a colorimetric value when the output result is measured under the second observation condition is created in advance. Conversion processing may be performed based on this.

  As this data, various data modes can be adopted as long as the above conversion can be performed. For example, it is possible to adopt a configuration in which the colorimetric values in the first viewing condition are associated with the colorimetric values in the second viewing condition, and this correspondence is defined by a plurality of data or functions. Of course, when conversion is performed using a plurality of pieces of data, it is possible to adopt a configuration in which conversion is performed for an arbitrary colorimetric value by interpolation calculation.

  Further, a configuration in which the colorimetric value under the second observation condition is calculated by a predetermined calculation may be employed. For example, if a spectral distribution corresponding to the reflectance for each wavelength of visible light is used, colorimetric values in the device-independent color space can be calculated using a color matching function. The conversion may be performed by data indicating a spectral distribution for obtaining a colorimetric value under the second observation condition in combination with the spectral distribution.

  The profile creation means only needs to create a profile by associating the converted colorimetric values with the image data. Again, the profile may be a table in which colorimetric values and image data are associated with each other for a plurality of combinations, or a function in which both are associated, and various configurations can be employed. . In any case, a profile can be created by acquiring the correspondence between the colorimetric value and the image data for a plurality of combinations.

  As a preferred configuration of the data used when performing the conversion in the colorimetric value conversion means, spectral distribution data obtained by calculating the spectral distribution component that varies depending on the observation conditions as the spectral distribution component for the color measurement target is adopted. can do. The colorimetric values obtained by measuring the same colorimetric object under different viewing conditions are different, but the difference is that the spectral distribution obtained by measuring the colorimetric object varies depending on the viewing conditions. Caused by.

  This spectral distribution is expressed by the product of the spectral distribution of light (light source) irradiated to the colorimetric object and the spectral distribution (spectral reflectance) of the colorimetric object itself. Naturally, the component corresponding to the spectral distribution of the light source changes if the observation conditions change. However, in the present invention, the spectral distribution of the color measurement object further varies depending on the observation conditions. It is assumed that a component and a component of a spectral distribution that does not vary depending on the observation conditions are included. That is, it is natural that the spectral distribution of the light source fluctuates due to a change in observation conditions, but the spectral distribution for the colorimetric object is not constant, and it is considered that it includes a component of the spectral distribution that varies depending on the observation conditions. Thus, it can be said that the inventors have invented that the variation of the colorimetric values caused by different observation conditions can be corrected accurately.

  Therefore, if spectral distribution data indicating a component of the spectral distribution that varies depending on the observation condition is used, it corresponds to the component of the spectral distribution that does not vary depending on the observation condition and the spectral distribution of the light source in the second observation condition. The colorimetric value can be corrected based on the component to be corrected. For example, a component of a spectral distribution that does not vary depending on the observation condition is acquired from the color measurement result under the first observation condition, a sum with the component of the spectral distribution that varies depending on the observation condition is calculated, and the second It is possible to obtain colorimetric values such as tristimulus values by multiplying the spectral distribution and color matching function of the light source under the viewing conditions.

  Of course, when the colorimetric values are converted based on the spectral distribution data, an operation for calculating the tristimulus values or the like with reference to the spectral distribution data may be performed, or the tristimulus values may be calculated in advance based on the spectral distribution data. It may be calculated and converted. In the latter case, for example, a tristimulus value obtained from the spectral distribution under the first observation condition is calculated, the above calculation is performed using the spectral distribution to calculate a tristimulus value, and the two are associated with each other. What is necessary is just to employ | adopt a structure.

  Note that the component of the spectral distribution that varies depending on the observation conditions can be calculated based on the colorimetric values obtained by measuring the samples for evaluation in advance under the first observation condition and the second observation condition. . That is, in the present invention, the colorimetric result under the first viewing condition is corrected to the colorimetric result under the second viewing condition, so that it does not vary depending on the viewing condition with the colorimetric value under the first viewing condition as a reference. The component of the spectral distribution can be predicted. If a spectral distribution component that does not vary depending on the observation condition can be predicted, the spectral distribution component that does not vary depending on the observation condition is excluded from the colorimetric values in the second observation condition. The component of the spectral distribution that varies depending on the observation conditions can be calculated.

  In this case, since the first observation condition is an observation condition that serves as a reference for predicting a component of the spectral distribution that does not vary depending on the observation condition, the color measurement that performs color measurement using a predetermined light source The observation conditions in the vessel are preferred. That is, the observation conditions include the type of light source, the light irradiation direction from the light source, the orientation direction of the sensor in the colorimeter with respect to the color measurement target, the physical properties of the color measurement target (the print medium in the printed material and the color material used for printing) Various types of conditions can be assumed.

  Here, if the sample for evaluation is specified, the physical property of the colorimetric object is specified. Therefore, if a colorimeter (a colorimeter having a light source) that performs color measurement using a predetermined light source is used. Among the main factors of the viewing conditions, the type of light source, the direction of light irradiation from the light source, and the orientation direction of the sensor in the colorimeter with respect to the color measurement target can be specified. In this way, if the main factor of the observation condition is fixedly specified, it can be assumed that the colorimetric value in the first observation condition does not have a spectral distribution that varies depending on the observation condition.

  On the other hand, in a colorimeter that performs colorimetry using an arbitrary light source (colorimeter that does not include a light source), it is common to prepare some light source for colorimetry. Even if the object is illuminated, light from multiple directions other than this light source is irradiated to the colorimetric object. Therefore, color measurement can be performed in a state close to the observation condition (second observation condition) in which a color measurement object such as a printed matter is actually observed. As described above, it has been found that, under the observation conditions in which light is applied to the colorimetric object from multiple directions, the contribution of the component of the spectral distribution that is extracted according to the present invention and varies depending on the observation conditions increases.

  Therefore, according to the above configuration, the color measurement result when the color measurement is performed in a state close to the observation condition under which the color measurement target is actually observed is obtained using the color measurement result obtained by the color measuring device including the light source. It becomes possible to do. As a result, it is possible to acquire a component of the spectral distribution that varies depending on the observation condition, which occurs when the colorimetric object is observed under the second observation condition. Note that the sample for evaluation may be a sample that can be observed under the same conditions as the colorimetric conditions for the output based on the image data. For example, a color chart including patches of a plurality of colors is used. Is possible.

  As described above, the spectral distribution of the light source varies depending on the observation condition. In the present invention, the colorimetric value can be acquired by correction even under observation conditions in which it is difficult to specify the spectral distribution of the light source in advance (observation conditions in a colorimeter that performs colorimetry using an arbitrary light source). The purpose is to do. Therefore, when extracting the component of the spectral distribution that varies depending on the observation conditions in the present invention, it is preferable to exclude the spectral distribution of the light irradiated to the colorimetric object.

  As a configuration for this purpose, it is preferable to use the color measurement result of the white plate. That is, the white plate is a sample having a substantially constant reflectance over the entire wavelength of visible light. If this spectral distribution is measured, the white plate is almost the same as the spectral distribution of the light irradiated to the colorimetric object under the observation conditions. An equivalent spectral distribution can be acquired. Specifically, it is assumed that the white plate is color-measured under the first observation condition and the second observation condition, and the obtained spectral distribution is the spectral distribution of light irradiated to the colorimetric object under each observation condition.

  If this spectral distribution can be acquired, the spectral distribution component of the light source and other spectral distribution components can be easily separated from the colorimetric values obtained by measuring the sample for evaluation under the second observation condition. be able to. Therefore, it is very easy to analyze the remaining spectral distribution as a component of a spectral distribution that varies depending on the observation conditions and a component of a spectral distribution that does not vary depending on the observation conditions.

  Furthermore, the component of the spectral distribution that varies depending on the observation condition may be a spectral component that varies depending on the wavelength of visible light, and various functional forms can be assumed. As a preferable function as the spectral component, a function composed of a product of a constant and a function depending on a predetermined wavelength can be adopted. That is, the dependence on the observation condition can be expressed by a constant part. Specifically, if a wavelength-dependent function is determined in advance in this configuration, the wavelength-dependent function can be a component that does not depend on observation conditions.

  Further, the above constant is defined as a constant that is constant under the same observation condition but varies depending on the observation condition. As a result, the dependency on the observation condition can be expressed only by the constant part, and the dependency on the observation condition can be handled very easily. Various functions can be adopted as the function depending on the predetermined wavelength. For example, a linear combination of color matching functions can be adopted.

  That is, the color matching function has a property corresponding to the sensitivity of the human eye and is defined as a function that depends on the wavelength of visible light. On the other hand, the influence of the spectral distribution that varies depending on the observation conditions is recognized by being observed by the human eye. Therefore, if a function depending on the predetermined wavelength is defined by linear combination of these color matching functions, a spectral distribution reflecting the recognition by the human eye to some extent can be defined. As a result, it is possible to accurately express the wavelength dependence of the spectral distribution that varies depending on the observation conditions.

  As a specific method for performing linear combination, various methods can be adopted, and for example, it can be configured by the sum of three color matching functions. Of course, the configuration that expresses the component of the spectral distribution that varies depending on the observation conditions by the product of the constant and a function that depends on a predetermined wavelength is an example, and this spectral distribution varies depending on the observation conditions. As long as it does, various structures are employable.

  Various observation conditions can be employed as the observation conditions on which the components of the spectral distribution depend. For example, it is possible to adopt a configuration that depends on any one or combination of a print medium for printing a colorimetric object, a color material for printing the colorimetric object, and a light source. That is, the type of printing medium for printing the colorimetric object and the type of color material for printing the colorimetric object affects the spectral distribution of the colorimetric object. The types of color materials include all conditions that can vary the spectral distribution, such as dye and pigment inks and toners, or differences in the composition thereof.

  The type of light source affects the spectral distribution of the light received by the colorimeter when the colorimetric object is measured, so the observation conditions differ for different types of light sources and vary depending on the observation conditions. The component of the spectral distribution is varied. Of course, in the present invention, even if the observation condition is difficult to specify the spectral distribution of the light source in advance (observation condition in a colorimeter that performs colorimetry using an arbitrary light source), a colorimetric value is obtained by correction, and a profile is obtained. Is aimed at creating. Therefore, as the type of the light source, in addition to a configuration in which one light source is specified, a main light source is specified, or a light source such as sunlight or a fluorescent lamp is specified abstractly without specifying a light source. The light source may be indicated by specifying the surrounding environment, for example, the color temperature of the light source or the weather such as sunny or cloudy.

  Furthermore, the observation condition on which the component of the spectral distribution depends may be defined so as to depend on the relative positional relationship between the light source, the color measurement target, and the light receiving unit of the colorimeter. In other words, it has been found that the spectral distribution that varies depending on the observation conditions can vary depending on the angle at which the colorimetric object is observed. To describe this variation, the spectral distribution depends on the relative positional relationship. I decided to. In this configuration, by defining the relative positional relationship by an angle close to the angle at which the colorimetric object is actually observed, it is possible to obtain a spectral distribution in a state close to the actual observation condition.

  As the relative positional relationship, it is only necessary to define the positional relationship between the light source, the colorimetric object, and the light receiving unit of the colorimeter, and an angle or the like can be adopted. For example, for the angle between the light source and the colorimetric object, define a perpendicular to the sample from a certain observation point in a flat sample, define a straight line connecting this observation point and the light source, and define the angle between this straight line and the perpendicular To do. Furthermore, if a straight line connecting this observation point and the light receiving part of the colorimeter is defined, and the angle between this straight line and the perpendicular is defined, the positional relationship between the light source, the colorimetric object, and the light receiving part of the colorimeter is determined. Can be defined.

  The distance between the light source and the light receiving unit of the colorimeter and the colorimetric object has a small degree of influence on the spectral distribution, and thus the distance can be set arbitrarily, but of course the distance may be considered. As described above, when considering the observation conditions in which it is difficult to specify the spectral distribution of the light source in advance, the position of the main light source is defined in a situation where a large amount of light is applied to the colorimetric object. What is necessary is just to define the positional relationship of a light source, a colorimetric object, and the light-receiving part of a colorimeter.

  As described above, the spectral distribution data may be calculated by various methods, and the colorimetric values may be converted based on the spectral distribution data. Alternatively, the colorimetric values may be calculated based on the correspondence relationship of the calorimetric values calculated in advance instead of the spectral distribution data. The value may be converted, but in any case, the conversion can create a profile, and a color conversion profile can be further created based on this profile.

  That is, the color conversion profile here refers to a profile that defines the correspondence between the image data handled by the first image device and the second image data handled by the second image device. In general use. Therefore, if the correspondence between the second image data handled by the second image device and the output colorimetric value is acquired in advance, the profile (image data handled by the first image device) obtained by the profile creation means is obtained. The color conversion profile can be created with reference to the correspondence relationship between the color measurement value and the color measurement value. Therefore, the invention is established as an apparatus for creating this color conversion profile.

  As described above, according to the present invention, a general-purpose color conversion profile can be created, but when the above-described profile is measured in a state close to the observation condition under which the color measurement target is actually observed. It is created based on the colorimetric values. Therefore, the output based on the conversion by the color conversion profile is not significantly different from the color intended by the creator of the profile, and good color reproducibility can be realized. Of course, if a color conversion profile that defines the correspondence between the image data handled by the first image device and the second image data handled by the second image device can be obtained in this way, the color conversion profile is referred to. Thus, accurate color reproduction can be realized by a print control apparatus that executes printing. Therefore, the invention is also established as a print control apparatus that executes printing with reference to this color conversion profile.

  The above configuration can also be applied to a method invention based on the same technical idea. Therefore, the inventions according to claims 11 and 12 basically have the same action as described above. In addition, the present invention may be implemented by executing a predetermined program on a computer. Therefore, the present invention can also be applied as the program, and the invention according to claims 13 and 14 basically has the same operation as described above.

  Of course, it is also possible to make the structure described in claims 2 to 10 correspond to the above method and program. Any storage medium can be used to provide the program. For example, a magnetic recording medium or a magneto-optical recording medium may be used, and any recording medium that will be developed in the future can be considered in the same manner. In addition, even when a part is software and a part is realized by hardware, the idea of the present invention is not completely different, and a part is recorded on a recording medium and is appropriately changed as necessary. It includes a reading form.

Here, embodiments of the present invention will be described in the following order.
(1) Color conversion profile creation device:
(1-1) Print control processing:
(1-2) Color conversion profile creation process:
(2) Calculation of spectral distribution:
(2-1) Apparatus and process for calculating spectral distribution:
(3) Second embodiment:
(4) Other embodiments:

(1) Color conversion profile creation device:
FIG. 1 is a block diagram of a color conversion profile creation apparatus according to the present invention. In this embodiment, the color conversion profile creation device, the device for calculating the spectral distribution, and the print control device are realized by an integrated computer, but each device may be realized by a separate computer. In addition, a plurality of patches are printed based on the data after the color separation processing described later. This printing is preferably performed by a printer using the color conversion profile created in the present invention. Is also required to have the same algorithm as the halftone processing employed in the printer.

  The computer 10 includes a CPU 11 that is the center of arithmetic processing, and the CPU 11 controls the entire computer 10 via a system bus. The system bus is connected to a ROM 12, a RAM 13, a hard disk 14, a USB I / F, a CRTI / F, an input device I / F, etc. (not shown). In the hard disk 14, an operating system (OS) as software, a spectral distribution calculation program 20 for calculating a spectral distribution for correcting colorimetric values, a printer driver 30 for performing print control, and a color conversion profile are created. The color conversion profile creation program 60 and the like are stored, and the software is appropriately transferred to the RAM 13 by the CPU 11 at the time of execution. The CPU 11 executes various programs under the control of the OS while appropriately accessing the RAM 13 as a temporary work area.

  A keyboard and mouse (not shown) are connected to the input device I / F as operation input devices. Further, a display for display is connected to the CRTI / F. Therefore, the computer 10 can accept the operation content by the keyboard and the mouse, and can display various information on the display. Further, a printer 15 is connected to the USB I / F, and an image can be printed based on data output from the computer 10.

  Of course, the connection I / F with the printer 15 is not limited to the USB I / F, and various connection modes such as a parallel I / F, a serial I / F, and a SCSI connection can be adopted. The same applies to the connection mode. The computer 10 is connected with a colorimeter 40 and a colorimeter 50 through an interface (not shown), and the printed matter printed by the printer 15 is measured as a colorimetric object, and its spectral distribution and tristimulus values are measured. Or the like can be supplied to the computer 10.

(1-1) Print control processing:
The computer can calculate the spectral distribution, create the color conversion profile, and perform the print control in the above configuration. First, the print control and the creation of the color conversion profile will be described. Printing control is performed by the printer driver 30. The printer driver 30 includes an image data acquisition module 31, a color conversion module 32, a halftone processing module 33, and a print processing module 34. The image data acquisition module 31 is a module that acquires image data indicating a print target image.

  In the present embodiment, the image data acquired by the image data acquisition module 31 is sRGB standard data, and is data having a gradation range of 256 gradations for each RGB color component. The image data acquisition module 31 executes resolution conversion for matching the acquired image data when the number of pixels of the acquired image data and the number of pixels necessary for printing do not match. The color conversion module 32 is a module that converts the color system of image data by interpolation with reference to the color conversion profile 14 f stored in the hard disk 14.

  The color conversion profile 14f is a table that is created by the process described later and associates sRGB standard RGB data and CMYKlclm data for a plurality of combinations. The color conversion module 32 acquires image data from the image data acquisition module 31, refers to data described in the color conversion profile 14f, and converts arbitrary sRGB data into CMYKlclm data by interpolation calculation.

  When the color conversion module 32 performs color conversion to generate CMYKlclm data, the CMYKlclm data is transferred to the halftone processing module 33. The halftone processing module 33 converts the CMYKlclm gradation value of each dot and acquires halftone data specifying the presence / absence of ink droplet recording for each pixel and the amount of ink droplets recorded for each pixel.

  The print processing module 34 receives the halftone data and rearranges them in the order used by the printer 15. That is, the printer 15 is equipped with an ejection nozzle row (not shown) as an ink ejection device, and in this nozzle row, a plurality of ejection nozzles are arranged in parallel in the sub-scanning direction. Are used simultaneously. Therefore, rearrangement processing is performed to rearrange data in the main scanning direction in order so that data to be used at the same time is buffered by the printer 15 at the same time. After the rearrangement process, the print processing module 34 adds predetermined information such as image resolution to generate print data, and outputs the print data to the printer 15. The printer 15 prints an image indicated by the image data based on the print data, and obtains an output image.

  The color conversion profile 14f is created based on the result of correcting the colorimetric value by coefficient data 14d described later. Therefore, when printing is performed based on the conversion result of the color conversion profile 14f, a printed material that can be reproduced with good color under the observation conditions when the printed material is actually observed can be obtained. In this embodiment, in order to create the color conversion profile 14f, it is also possible to input CMYKlclm data to the halftone processing module 33 and perform printing.

  That is, printing processing can be performed by skipping processing by the color conversion module 32 as necessary. Of course, once the color conversion profile 14f is created, the process of creating the color conversion profile 14f is not necessary. Therefore, in a computer that does not include the spectral distribution calculation program 20 and the color conversion profile creation program 60, the color conversion profile 14f The printer driver 30 can be used for printing. Further, the configuration in which the printer 15 uses six colors of ink is an example, and the number of ink colors is not limited to six.

(1-2) Color conversion profile creation process:
FIG. 2 is a block diagram showing the configuration of the color conversion profile creation program 60, and FIG. 3 is a flowchart showing the processing when creating a color conversion profile. The color conversion profile creation program 60 includes a color separation processing unit 61, a colorimetric value acquisition unit 62, a colorimetric value correction unit 63, a target generation unit 64, and an interpolation calculation unit 65. In this embodiment, first, image data (CMYKlclm data) and colorimetric values (L ^* a ^* b) handled by the printer 15 by the color separation processing unit 61, the colorimetric value acquisition unit 62, and the colorimetric value correction unit 63. ^* Value) is created, and the target generation unit 64 and the interpolation calculation unit 65 generate sRGB data for outputting an image on the display based on the profile and image data handled by the printer 15. Create a corresponding color conversion profile.

  The color separation processing unit 61 specifies a three-dimensional gradation value (RGB: red, green, blue) for each ink color based on a predetermined color separation rule in order to specify a color measurement target patch. Conversion into (CMYKlclm: cyan, magenta, yellow, black, light cyan, light magenta) (step 100). Here, RGB data is adopted as an example of a three-dimensional gradation value, and CMYKlclm data is adopted as an example of a six-dimensional gradation value, and there are 256 gradations for each color component. The tone value range is not limited to this.

  Here, it is only necessary that 6-dimensional CMYKlclm data can be acquired from 3-dimensional RGB data according to a plurality of rules. That is, in the 6-dimensional CMYKlclm data, the same color can be expressed by a combination of different CMYKlclm gradation values by combining 6 colors of CMYKlclm. Accordingly, it is difficult to uniquely determine an ideal combination of CMYKlclm tone values for a patch that is a CMYKlclm tone value corresponding to a specific color and is a colorimetric target without providing any rules. Therefore, if the correspondence between RGB data and CMYKlclm data is defined as following a plurality of rules, CMYKlclm data can be easily obtained from RGB data.

  Specifically, since each RGB color has a complementary color relationship with each CMY color, C = 255−R, M = 255−G, and Y = 255−B unless the color is strictly defined by gradation values. In this sense, the RGB data in the reference LUT is equivalent to the CMY data. Therefore, when the RGB data is regarded as CMY data, the equal value a is subtracted from the CMY gradation values and C = M = Y = a is substituted with the K gradation value b. Furthermore, lc and lm are substituted at a fixed ratio for the remainder of C and M.

  Each gradation value of CMYKlclm is data for specifying the amount of ink used for each color. Therefore, in order to limit the use of ink, that is, the condition for limiting the ink weight to be recorded per unit area to a specific weight or less and the ink generation limit, that is, to make it difficult to give a grainy feeling or to reduce the color difference due to the light source. Each gradation value of CMYKlclm is determined in consideration of a condition for limiting the amount of specific ink used. Also, the more colors that can be expressed by the combination of CMYKlclm inks, the better for improving the image quality, so the color gamut is made as wide as possible. The rule determined in consideration of the above elements is a color separation rule, and the color separation processing unit 61 converts a plurality of RGB data into CMYKlclm data in accordance with a predetermined color separation rule.

  The CMYKlclm data obtained by the conversion is associated with the RGB data and recorded on the hard disk 14 as the separation data 14e. The CMYKlclm data in the separation data 14e is transferred to the halftone processing module 33. As a result, a plurality of patches are printed based on a plurality of CMYKlclm data defined in the color separation data 14e. Note that the number of RGB data and CMYKlclm data defined in the color separation data is about 1000, and a large number of patches are printed.

The colorimetric value acquisition unit 62 acquires a colorimetric value (spectral distribution R ₁ (λ)) obtained by measuring the plurality of patches with the colorimeter 40 (step S105). Here, the colorimeter 40 has a built-in light source, and can perform colorimetry by placing a colorimetric object such as a color chart on the document table. In addition, the sensor of the colorimeter 40 can move on a plane parallel to the document table, and can automatically measure a plurality of predetermined parts. Therefore, even if a large number of patches are printed as described above, the colorimetric values can be easily obtained. The above step S105 corresponds to the process in the colorimetric value acquisition means.

ここで、Ｒ_2w（λ）は測色器５０において白色板を測色して得られる分光分布、Ｒ_1w（λ）は測色器４０において白色板を測色して得られる分光分布、Ｒ₁（λ）はステップＳ１０５で取得した分光分布であり、詳細は後述する。また、上部に−を付したｘ（λ），ｙ（λ），ｚ（λ）は等色関数、係数Ｋ_mは最大視感度（「色彩工学」、東京電機大学出版局、大田登著、２４頁）であり、Δλは測色器におけるサンプリング間隔である。 When the colorimetric values are obtained for a plurality of patches, the colorimetric value correction unit 63 refers to the coefficient data 14d, and corrects the colorimetric values based on the following equation (1) while tristimulus values of each patch. (X′Y′Z ′) is acquired, and an L ^* a ^* b ^* value is acquired from these tristimulus values (step S110). The above step S110 corresponds to the processing in the colorimetric value conversion means.

Here, R _2w (λ) is a spectral distribution obtained by measuring the color of the white plate in the colorimeter 50, R _1w (λ) is a spectral distribution obtained by measuring the color of the white plate in the colorimeter 40, and R ₁ (λ) is the spectral distribution acquired in step S105, and details will be described later. In addition, x (λ), y (λ), and z (λ) with − attached to the upper part are color matching functions, the coefficient K _m is the maximum visual sensitivity (“Color Engineering”, Tokyo Denki University Press, Noboru Ota, 24), and Δλ is a sampling interval in the colorimeter.

The coefficient k _W is a value described in the coefficient data 14d and will be described in detail later. In this embodiment, the spectral distributions R _2w (λ) and R _1w (λ) are included in the coefficient data 14d, and the color matching function is recorded in advance on the hard disk 14 as the color matching function data 14c. The conversion from the tristimulus value to the L ^* a ^* b ^* value can be performed based on a known formula. By correcting as described above and calculating the tristimulus value, the tristimulus value in the observation condition (second observation condition) for actually observing the printed matter can be obtained, and the color is determined based on the colorimetric value. By creating the conversion profile 14f, it is possible to create a color conversion profile that performs color matching under this viewing condition.

When the colorimetric values are corrected by the colorimetric value correction unit 63, the L ^* a ^* b ^* values based on the corrected tristimulus values can be associated with the RGB data before the color separation process in step S100. . Also, the correspondence between arbitrary RGB data and CMYKlclm data can be defined by referring to the separation data 14e or by processing of the separation processing unit 61. Accordingly, the L ^* a ^* b ^* value based on the corrected tristimulus value can be associated with the CMYKlclm data.

Therefore, the correspondence relationship between RGB data before color separation processing and the corrected L ^* a ^* b ^* value, or the correspondence relationship between CMYKlclm data and the corrected L ^* a ^* b ^* value is converted by the present invention. The colorimetric values (L ^* a ^* b ^* values) and image data (RGB data or CMYKlclm data) are associated with each other. In the present embodiment, the process of creating a profile in which the colorimetric values converted by the colorimetric value correction unit 63 are associated with the image data corresponds to the process in the profile creating unit.

  According to this profile, the correspondence between the image data handled by the printer 15 and the output colorimetric value based on the image data can be acquired. Next, a predetermined target is set and the color conversion profile is set. create. For this purpose, first, the target generation unit 64 sets sRGB data as a target (step S115) and performs color gamut mapping (step S120).

That is, the target generation unit 64 sets sRGB data as a reference point registered in the color conversion profile as a target. In the present embodiment, each gradation value range in sRGB is equally divided (for example, 17 equally), and a value obtained by combining the obtained gradation values is set as target sRGB data. sRGB data can acquire the L ^* a ^* b ^* values corresponding by known formula, L ^* a ^* b ^* values corresponding to the target can be easily acquired.

Therefore, when the L ^* a ^* b ^* values obtained from all the sRGB data are taken into consideration and plotted in the L ^* a ^* b ^* space, the color gamut based on the sRGB data can be grasped by the outline. On the other hand, if the corrected L ^* a ^* b ^* values are plotted in the L ^* a ^* b ^* space, the color gamut of the printer 15 can be grasped. Therefore, the target generation unit 64 performs color gamut mapping so that the L ^* a ^* b ^* value corresponding to the sRGB data is included in the color gamut of the printer 15. Of course, other corrections may be performed in addition to the above mapping. For example, humans tend to memorize sky and skin colors more vividly than actual colors, so human memory colors are different from actual colors, so correct the colors so that they are close to human memory colors. May be.

When the mapping as described above is completed, since the correspondence between the sRGB data and the L ^* a ^* b ^* values is known, the color conversion profile 14f is created together with the profile acquired in step S110. That is, the interpolation calculation unit 65 acquires an L ^* a ^* b ^* value corresponding to the target sRGB data. The RGB data corresponding to the L ^* a ^* b ^* values (RGB data in the color system before color separation processing in step S100) is defined in the profile created by the colorimetric value correction unit 63. The L ^* a ^* b ^* value is converted into RGB data with reference to the profile (step S125).

  Since the CMYKlclm data corresponding to the RGB data can be obtained by the color separation processing by the color separation processing unit 61, the interpolation calculation unit 65 passes the RGB data to the color separation processing unit 61, and after the color separation processing The CMYKlclm data is acquired. That is, the RGB data is converted into CMYKlclm data (step S130). Of course, the RGB data may be converted into CMYKlclm data by interpolation with reference to the color separation data 14e.

In any case, the obtained CMYKlclm data is CMYKlclm data for outputting L ^* a ^* b ^* values corresponding to the target sRGB data. Therefore, the sRGB data of the target is associated with the CMYKlclm data. This process is performed for all the targets, and data defining the correspondence is recorded on the hard disk 14 as the color conversion profile 14f (step S135). In the present embodiment, the processing in steps S115 to S135 corresponds to the processing in the color conversion profile creation means.

(2) Calculation of spectral distribution:
In the color conversion profile 14f created as described above, the correction based on the component of the spectral distribution that varies depending on the observation conditions is performed in step S110, so that the observation conditions for actually observing the printed matter are satisfied. In addition, a printed matter with good color reproduction can be obtained. Therefore, next, a method for calculating the spectral distribution will be described in detail.

  In the present invention, the spectral distribution is obtained for the purpose of obtaining a colorimetric value obtained by correcting the colorimetric value measured under the first observation condition and performing colorimetry under the second observation condition. calculate. In general, colorimetric values differ when colorimetric measurements are performed under different viewing conditions, so there is a difference between the two colorimetric values. In the present invention, however, the cause of this difference is analyzed and depends on the viewing conditions. Thus, the correction can be performed by calculating the component of the spectral distribution that fluctuates.

  FIG. 4 shows an outline of processing for calculating a component of the spectral distribution that varies depending on the observation conditions. In this embodiment, the observation condition by the colorimeter 40 (automatic colorimeter with built-in light source) is set as the first observation condition, and the observation condition by the colorimeter 50 (colorimeter without light source) is set at the second. The component of the spectral distribution that varies depending on the observation condition is calculated based on the colorimetric values of both. The colorimeter 40 is the above-described colorimeter and has a built-in light source. Therefore, the incident angle of light from the light source to the observation object and the observation angle (the angle between the perpendicular line in the observation object and the sensor in the colorimeter 40 ) Has been identified.

  The colorimeter 50 does not have a built-in light source, and performs colorimetry by setting an original to be measured within the field of view of the sensor in the colorimeter 50. When changing the colorimetric object in the colorimeter 50, it is necessary to move the desired colorimetric object into the field of view of the sensor in the colorimeter 50. Further, since the colorimeter 50 does not have a built-in light source, it is necessary to perform color measurement in a situation where light is irradiated from the surroundings to the color measurement target. A predetermined light source can be prepared to illuminate the colorimetric object, but even in this case, light can enter the colorimetric object from multiple directions.

  When actually observing a printed matter, not only light from a specific light source but also light from multiple directions reflected by the printed matter is observed, and the light source and observation angle are not limited. Therefore, a colorimeter that does not include a light source and does not have a limited light source and observation angle like the colorimeter 50 can perform color measurement under conditions closer to the observation conditions when actually observing the printed matter. Is possible. Therefore, in the present embodiment, the colorimeter 40 performs colorimetry on a large number of patches, and the colorimetry result is corrected, so that the colorimetry result obtained by the colorimeter 50 can be obtained. Then, the component of the spectral distribution that fluctuates is calculated.

  As a result of the color measurement of the printed matter by the colorimeter 40 and the colorimeter 50, the applicant of the present application has found that the spectral distribution of the printed matter has a certain tendency. That is, it was found that the spectral distribution obtained by the colorimeter 50 is larger than the spectral distribution obtained by the colorimeter 40 over almost all wavelengths, and the spectral distribution approximates a linear combination of color matching functions. . Furthermore, it has been found that different spectral distributions can be described for each observation condition by multiplying a linear combination of color matching functions by a constant depending on the observation condition.

  As the observation conditions, a plurality of conditions with different types of light sources and angles with respect to the colorimetric object can be assumed. However, according to the above approximation, the colorimetric values are corrected even if such conditions vary. Is possible. Further, the observation conditions for the color measurement object include conditions for the color measurement object itself. In addition, since the fluctuation of the spectral distribution depending on the above observation conditions is larger in the pigment than in the dye, the present invention is more effective when the pigment ink is used as a colorimetric object.

  When a color chart is observed under the second observation condition in order to acquire a component of the spectral distribution that varies depending on the observation condition, the spectral distribution of the color chart is not dependent on the observation condition (hereinafter referred to as a basic distribution). It is assumed that the sum of a reflection component and a spectral distribution depending on the observation conditions. This assumption is based on the fact that the spectral distribution obtained by the colorimeter 50 is larger than the spectral distribution obtained by the colorimeter 40 over almost all wavelengths. In addition, since the component of the spectral distribution depending on the observation condition exists over almost all wavelengths of visible light, this spectral distribution is hereinafter referred to as a white reflection component.

ここで、左辺は３刺激値であり、Ｒ_2p（λ）は、測色器５０においてカラーチャートを測色して得られる分光分布であり、他の文字は上記式（１）と同様である。 In addition, when the color measurement result (tristimulus value) by the colorimeter 50 is expressed by an equation, the equation (2) is obtained.

Here, the left side is tristimulus values, R _2p (λ) is a spectral distribution obtained by measuring the color chart in the colorimeter 50, and the other characters are the same as the above formula (1). .

ここで、Ｒ_2w（λ）は測色器５０において白色板を測色して得られる分光分布、Ｒ_p（λ）は上記基礎反射成分の分光分布、Ｒ_M（λ）は上記白色反射成分の分光分布である。他の文字は上記式（２）と同様である。また、３刺激値のＸ，Ｚについても同様に記述することができる。 When the above assumption is introduced to this equation, the following equation (3) is obtained.

Here, R _2w (λ) is the spectral distribution obtained by measuring the color of the white plate in the colorimeter 50, R _p (λ) is the spectral distribution of the basic reflection component, and R _M (λ) is the white reflection component. Is the spectral distribution. Other characters are the same as in the above formula (2). The tristimulus values X and Z can be described in the same manner.

In general, tristimulus values for objectively expressing colors are obtained by calculating the product of the spectral distribution of the light source, the spectral distribution of the colorimetric object, and the color matching function for each wavelength, and taking the sum. Calculated. However, in this embodiment, since the color measurement is performed without specifying the spectral distribution of the light source, the spectral distribution acquired by the colorimeters 40 and 50 is the spectral distribution of the light source and the spectral distribution of the color measurement target. Is multiplied by. Therefore, the spectral distribution of the light irradiated to the colorimetric object is acquired by measuring the white plate. That is, the white plate is a sample having a substantially constant reflectance over the entire wavelength of visible light, and the spectral distribution of the light irradiated to the colorimetric object can be obtained by measuring the white plate. it can. Therefore, R _2w (λ) in the above formula (3) is equivalent to the spectral distribution of the light source under the second observation condition.

Assuming that the luminance Y _{2p of the} tristimulus values in the second observation condition is expressed by the above equation (3), as shown in FIG. 4, the luminance Y _2p in the second observation condition is derived from the basic reflection component. It may be the sum of the luminance Y _M derived from Y _p and white reflection component.

In this embodiment, it is assumed that the luminance Y _M due to the white reflection component is the product of the sum of the color matching functions x (λ), y (λ), z (λ) and the coefficient k _W. In other words, the white reflection component is a component that occurs when light is emitted from multiple directions to the colorimetric object and the color of the printed material is measured under the condition that the reflected light reflected in multiple directions is observed. It is visually recognized when doing. Therefore, the applicant of the present application adopts the above assumption, assuming that the wavelength dependence is close to the wavelength dependence of the white reflection component if the wavelength dependence is expressed by linear combination of color matching functions corresponding to the sensitivity of the human eye. Actually, when the colorimetric values of the printed matter printed with the pigment are different between the colorimeter 40 and the colorimeter 50, the colorimetric values of the colorimeter 50 are determined by taking into account the spectral distribution determined based on the above assumption. I know I can describe it.

すなわち、上記Ｒ_M（λ）がｋ_W（ｘ（λ）＋ｙ（λ）＋ｚ（λ））となっており、他の文字は上記式（３）と同様である。 This assumption can be expressed as the following formula (4).

That is, R _M (λ) is k _W (x (λ) + y (λ) + z (λ)), and other characters are the same as those in the above formula (3).

On the other hand, since the luminance Y _M due to the white reflection component is Y _2p −Y _p , the white reflection component can be calculated by calculating the difference between the actually measured Y _2p and the Y _p estimated from the colorimetric values obtained by the colorimeter 40. The value of luminance Y _M can be calculated. Therefore, it can be said that if it is possible to determine the coefficients k _W as the white reflection component by the luminance Y _M and the formula (4) and is equal, it is possible to obtain the spectral distribution of the white reflection component.

In the present embodiment, for determining the coefficient k _W, color measurement and sample and white plate for evaluation in the first observation condition and the second viewing conditions. In this embodiment, the sample for evaluation is a color chart in which a plurality of patches are printed by a printer. In FIG. 4, the spectral distribution obtained as a result of colorimetry of the color chart by the colorimeter 40 under the first observation condition is R _1p (λ), and the white plate is obtained by the colorimeter 40 under the first observation condition. The spectral distribution obtained as a result of the color measurement is shown as R _1w (λ).

Further, the spectral distribution obtained as a result of measuring the color chart with the colorimeter 50 under the second observation condition is R _2p (λ), and the result of measuring the color of the white plate with the colorimeter 50 under the second observation condition is obtained. The resulting spectral distribution is shown as R _2w (λ). Of course, tristimulus values can be acquired by multiplying the spectral distribution and the color matching function for each wavelength and taking the sum. In the present invention, it is only necessary to determine the spectral distribution of the white reflection component based on these colorimetric results, and various methods can be employed as long as the spectral distribution of the white reflection component can be determined. . A specific processing example for this will be described in detail later.

  As described above, if the spectral distribution of the white reflection component can be acquired, correction is made from the colorimetric value obtained by measuring the color of an arbitrary printed matter by the colorimeter 40 and the colorimetric value obtained by measuring the white plate by the colorimeter 50. A later value (a colorimetric value obtained when the colorimetric device 50 performs colorimetry on the arbitrary printed matter) can be acquired. That is, the corrected tristimulus value can be calculated by the above equation (1).

In the present invention, not only (R ₁ (λ) / R _1w (λ)) indicating the spectral distribution of the fundamental reflection component in the formula (1) but also k _W (x indicating the spectral distribution of the white reflection component. It is important that (λ) + y (λ) + z (λ)) is included. That is, if the component of the spectral distribution that varies depending on the observation conditions can be described only by the variation of the light source, it is not necessary to include the spectral distribution of the white reflection component in the expression (1). It is only necessary to multiply R _2w (λ) corresponding to the spectral distribution of the light source and the spectral distribution of the fundamental reflection component.

  However, in actuality, when tristimulus values are calculated under the second observation condition, accurate correction cannot be made unless the luminance is calculated by adding the spectral distribution of the white reflection component to the spectral distribution of the basic reflection component. This is because a printed matter such as a pigment can generate a white reflection component due to the influence of the observation angle and the like in addition to the difference in the light source. Therefore, it can be said that the spectral distribution of the white reflection component in the present embodiment is a spectral distribution that varies depending on the observation conditions.

In the present invention, the tristimulus value itself (result obtained by summing the values for each wavelength) is not calculated as a correction value depending on the observation condition, but a spectral distribution that varies depending on the observation condition is calculated. Calculated. Therefore, once the spectral distribution is determined, not only the luminance Y but also X and Z can be accurately corrected. As a result, the hue and saturation can be corrected. Further, the spectral distribution of the white reflection component from it is multiplied by the coefficient k _W to a known color matching function, the light source or the like in the second viewing conditions change the coefficient k _W even if the varied Thus, it is possible to easily follow the difference in observation conditions and perform correction.

(2-1) Apparatus and process for calculating spectral distribution:
Next, an apparatus to which the above-described spectral distribution calculation method is applied and its processing will be described in detail. Figure 1 is a block diagram showing a computer arrangement for calculating the coefficient k _W, FIG. 5 is a flowchart illustrating a process for calculating the coefficient k _W. This process is performed by the spectral distribution calculation program 20. The spectral distribution calculation program 20 includes a colorimetric value acquisition unit 21, a basic reflection component calculation unit 22, an average value calculation unit 23, and a white reflection component calculation unit 24. In the present embodiment, to calculate the coefficients k _W and spectral distribution calculation program 20 and the printer driver 30 is operated as follows.

  The printer driver 30 prints the color chart in step S200 of FIG. That is, in the present embodiment, patch image data 14a for printing a plurality of patches on a single printing sheet to form a color chart is recorded in the hard disk 14 in advance. In the present embodiment, the patch image data 14a is data that specifies the amount of use for each color of ink used in the printer 15, and is data that represents the amount of ink used for each color in gradation for a plurality of pixels. For example, when each color ink of CMYKlclm is used in the printer 15, the usage amount for each color is indicated by a gradation value (for example, 0 to 255) in each pixel.

  The patch image data 14a is transferred to the halftone processing module 33. The halftone processing module 33 performs halftone processing based on the patch image data 14a. The print processing module 34 receives the data after the halftone process and performs printing as described above. As a result, the printer 15 prints the image indicated by the patch image data 14a based on the print data to obtain a color chart.

When the color chart is printed, the colorimetric value acquisition unit 21 of the spectral distribution calculation program 20 acquires the colorimetric values (spectral distribution) measured by the colorimeter 40 and the colorimeter 50 (steps S205 to S220). . That is, the color meter 40 measures the color of the printed color chart (step S205), and the color meter 40 measures the color of the white plate (step S210). The obtained spectral distributions are R _1p (λ) and R _1w (λ), respectively. Since the colorimeter 40 has a built-in light source as described above and an observation angle is determined, the condition for measuring the color chart and the white plate at the light source and the observation angle is the first observation. It is a condition.

Further, the colorimeter 50 also measures the color of the printed color chart (step S215), and further measures the color of the white plate (step S220). The obtained spectral distributions are R _2p (λ) and R _2w (λ), respectively. Since the colorimeter 50 does not include a light source as described above, the state in which the colorimetric object is illuminated with a colorimetric brightness and an appropriate observation angle (when actually observing the printed matter) The color is measured at an observation angle). This observation condition is the second observation condition. That is, the observation conditions are set so that the observation conditions for measuring the color of the evaluation sample coincide with the observation conditions for actually observing the printed matter, and this observation condition is set as the second observation condition.

  The colorimetric values measured as described above are recorded on the hard disk 14 (colorimetric value data 14b). In the colorimeter 40 and the colorimeter 50, the spectral distribution of the colorimetric object is measured. Of course, the tristimulus value is easily calculated by multiplying the color matching function for each wavelength to obtain the sum. It is possible. In this embodiment, color matching function data 14c indicating a color matching function is recorded in advance on the hard disk 14 for this calculation.

Next, the basic reflection component calculation unit 22 refers to the colorimetric value data 14b and the color matching function data 14c, and calculates the luminance Y _p based on the basic reflection component (step S225). Specifically, the luminance Y _p is calculated by the following equation (5).

Here, R _2w (λ) is a spectral distribution obtained by measuring the white plate in the colorimeter 50 (step S220), and R _1w (λ) is measured in the colorimeter 40 (step S220). (S210) is a spectral distribution obtained by measuring the color chart (step S205) in the colorimeter 40, and R _1p (λ) is a spectral distribution obtained by measuring the color chart (step S205). It is the same. Since the spectral reflectance R _1p (λ) is obtained for each patch on the color chart, the luminance Y _p is calculated for each patch included in the color chart printed in step S200.

In the above formula (5), R _1p (λ) / R _1w (λ) corresponds to the spectral distribution (basic reflection component) of each patch itself. That is, the spectral distribution R _1p (λ) obtained by measuring the color of the patch under the first observation condition is the product of the spectral distribution of the light source and the spectral distribution of the patch itself. By normalizing with R _1w (λ) corresponding to the spectral distribution, a distribution corresponding to the spectral distribution of the patch itself is obtained. This derivation is made possible by assuming that a white reflection component is generated under the second observation condition and no white reflection component is generated under the first observation condition. If the spectral distribution of the patch itself is obtained in this way, the luminance Y _p can be calculated using this spectral distribution and R _2w (λ) corresponding to the spectral distribution of the light source under the second observation condition. Become.

The average value calculation unit 23 calculates the average for each of the plurality of patches for the luminance Y _M based on the white reflection component (step S230). Here, it is assumed that the luminance Y _M is the difference between the luminance Y _2p and the luminance Y _p . The brightness Y _2p is a value calculated by the equation (2) from the colorimetric value in step S215, and the brightness Y _p is the value calculated in step S225.

The applicant of the present application calculated the luminance Y _M by changing the type of the light source in the second observation condition for the patch printed with the pigment ink. As a result, it has been found that the luminance Y _M has a small light source dependency and can be considered to be substantially constant regardless of the light source. However, the luminance Y _M is substantially constant regardless of the light source, and the spectral distribution of the white reflection component is not constant regardless of the light source. That is, the luminance Y _M is calculated by adding the product of the spectral distribution of the light source, the spectral distribution of the white reflection component, and the color matching function for each wavelength. However, if the light source changes, the spectral distribution of the light source changes. In accordance with this, the spectral distribution of the white reflection component also fluctuates, and the resulting luminance Y _M may be substantially constant regardless of the light source.

The white reflection component calculation unit 24 calculates the luminance Y _M and the luminance Y _2w calculated in step S230 (the luminance obtained by the same calculation as equation (2) from the spectral distribution R _2w (λ) measured in step S220). and a preparative color matching function to calculate the coefficients k _W in white reflection component (step S235). In the present embodiment, to calculate the coefficients k _W based on the following derivation.

That is, the luminance Y _M is expressed by the following equation (6), and the luminance Y _W of the white plate measured under the second observation condition is expressed by the following equation (7).

Since the white plate is a sample having a substantially constant reflectivity over all wavelengths of visible light, if the spectral distribution R _2w (λ) is considered to be a constant r _{w in} the above formulas (6) and (7), the formula ( 6) and (7) can be modified as equations (8) and (9), respectively.

If r _w is deleted based on both equations and the equations are arranged, the coefficient k _W can be expressed as the following equation (10).

Since this formula includes only the calculated values of luminance Y _M , luminance Y _2w and color matching function or only known functions, the calculated value is substituted and the sum of the values for each wavelength based on the color matching function. The coefficient k _W can be calculated by taking White reflection component calculation unit 24, based on the above equation after calculating the coefficient k _W, is recorded in the hard disc 14 as the coefficient data 14d (step S240). At this time, the coefficient data 14d includes a spectral distribution R _1w (λ) obtained by measuring the color of the white plate in the colorimeter 40 and a spectral distribution R obtained by measuring the color of the white plate in the colorimeter 50. _2w (λ) is included. Thereby, the colorimetric value can be corrected based on the above equation (1).

In the present invention, by changing the coefficients k _W for each observation condition, it is possible to describe the spectral distribution that varies depending on the viewing conditions, while changing the second viewing conditions, the diagram By performing the processing shown in FIG. 5, it is possible to calculate spectral distributions for various observation conditions. In this case, the coefficient data 14d preferably includes data indicating the observation conditions (for example, data indicating the type of light source, the print medium, and the type of color material used for printing). In this configuration, it is possible to acquire colorimetric values under the various observation conditions based on the coefficient data 14d that matches the various observation conditions and the colorimetric values under the first observation condition. Of course, it is sufficient to calculate the coefficient data 14d for the specific viewing condition in order to create the color conversion profile 14f for implementing good color reproduction under the specific viewing condition. On the other hand, if it is configured to be able to acquire colorimetric values under various observation conditions, versatility is enhanced.

  In the measurement by the colorimeter 50, the light source cannot be clearly specified. That is, the colorimeter 50 does not include a light source, and even if a specific color source illuminates the color measurement target, light from other than the light source is irradiated to the color measurement target. Therefore, in specifying the observation condition associated with the coefficient data 14d, in addition to associating the type of the light source, the light source is indicated by specifying the surrounding environment, for example, the color temperature of the light source, the weather such as sunny or cloudy, etc. You may do it. Of course, the main light source used when the colorimeter 50 performs the measurement may be shown as the observation condition.

(3) Second embodiment:
In the above embodiment, the component of the spectral distribution depending on the observation condition is calculated for correction by the computer 10. However, after correction based on a colorimeter in which data for correction is recorded in advance. Colorimetric values may be acquired to create the color conversion profile 14f. For example, a configuration is adopted in which a correction profile is recorded in the colorimeter 40 in advance, and after the measurement under the first observation condition is performed by the colorimeter 40, the colorimetric value under the second observation condition is output. Is possible.

  FIG. 6 is a block diagram showing a configuration of the colorimeter 40 having a correction profile. As shown in the figure, the colorimeter 40 includes a sensor 41, a sensor driving unit 41a, an A / D conversion unit 42, a program execution environment (CPU 43, RAM 44, ROM 45), a user interface (operation unit 46, output unit 47), and the like. An interface (I / F 48) for connecting to the computer 10 and an optical system (light source 49, light source controller 49a) are provided.

  In the colorimeter 40, a program (not shown) recorded in advance in the ROM 45 is transferred to the RAM 44, and the CPU 43 controls each unit by executing this program. That is, the operation unit 46 is connected to an input device such as a button (not shown), and the CPU 43 acquires the operation content in the operation unit 46. The output unit 47 is a display device that outputs predetermined information, and can display an operation input guide and a color measurement result in the operation unit 46.

  The sensor 41 is configured to be movable in parallel to the surface of the document table (not shown) provided in the colorimeter 40. The sensor drive unit 41a drives the sensor 41 according to an instruction from the CPU 43 and sets it at a desired position. . The movement of the sensor 41 may be controlled based on an input from the operation unit 46, or may be controlled by a predetermined procedure, and various methods may be employed. The light source control unit 49a supplies power to the light source 49 according to an instruction from the CPU 43, and turns on the light source. The light source 49 irradiates the colorimetric object placed on the document table and is within the field of view of the sensor 41 with light.

  The A / D converter 42 is driven according to an instruction from the CPU 43 and converts a signal detected by the sensor 41 into a digital signal. CPU 43 Detects the spectral distribution of the colorimetric object based on this digital data. Of the programs executed by the CPU 43, the programs relating to the colorimetry control include a colorimetry control unit 43a and a correction unit 43b. As described above, the colorimetry control unit 43a instructs the sensor drive unit 41a and the light source control unit 49a, and acquires the digital signal output from the A / D conversion unit 42 as a result.

  Since the digital signal is a spectral distribution under the first observation condition, the correction unit 43b performs correction based on the spectral distribution. In the ROM 45, a correction profile 45a is recorded in advance for performing this correction. The correction profile 45a is profile data in which the colorimetric values in the first viewing condition and the colorimetric values in the second viewing condition are associated with each other, and various data modes are adopted as long as they can be associated with each other. can do.

For example, if the spectral distribution R ₁ (λ) when colorimetry is performed under the first observation condition is substituted for R _2p (λ) in the above equation (2), 3 in the first observation condition is substituted. Stimulus values can be calculated. On the other hand, if the spectral distribution R ₁ (λ), the coefficient k _W indicated by the coefficient data 14d, the spectral distribution R _1w (λ), and the spectral distribution R _2w (λ) are substituted into the equation (1), Tristimulus values under the second observation condition can be calculated.

  Therefore, if the tristimulus values in the first observation condition are associated with the tristimulus values in the second observation condition, and this correspondence is obtained for a plurality of tristimulus values, table data for converting the tristimulus values is obtained. Can be created. If such table data is used as the correction profile 45a, tristimulus values are calculated on the basis of the spectral distribution acquired by the colorimetric control unit 43a, and then subjected to an interpolation operation with reference to the correction profile 45a under the second observation condition. Tristimulus values can be acquired.

Of course, the correction profile 45a is a function indicating the relationship between the tristimulus values under the first observation condition and the tristimulus values under the second observation condition in addition to defining the correspondence between the plurality of tristimulus values. Alternatively, it may be data indicating the correspondence between other color systems, for example, L ^* a ^* b ^* . Further, the correction profile 45a may be constituted by the coefficient k _W , the spectral distribution R _1w (λ), the spectral distribution R _2w (λ), and a color matching function.

  In any case, the correction unit 43b corrects the colorimetric value under the first viewing condition with reference to the correction profile 45a, and acquires the colorimetric value under the second viewing condition. After calculating the corrected colorimetric value by the colorimeter 40 in this way, it is output to the computer 10. The computer 10 only needs to be able to execute the color conversion profile creation program 60 and the printer driver 30. The computer 10 performs the same processing as the processing shown in FIG. 3 and calculates the colorimetric values corrected in step S110. Get from. As a result of this processing, it is possible to create a color conversion profile 14f for performing good color reproduction under the observation conditions when actually observing the printed matter.

(4) Other embodiments:
In the present invention, correction is performed based on the component of the spectral distribution that varies depending on the observation conditions to create the color conversion profile 14f, or printing can be performed based on the color conversion profile 14f. In the above, various embodiments can be adopted. For example, the calculation method for calculating the white reflection component, which is a component of the spectral distribution that varies depending on the observation conditions, is not limited to the above equation (10).

Other techniques, it is possible to employ a structure to identify the coefficient k _W by numerical calculation. That is, the luminance Y _M due to the white reflection component is expressed by the above equation (4), and the value is the sample and white for evaluation under the first observation condition and the second observation condition as in step S230. It can be calculated from the colorimetric values of the board. Therefore, assuming that the calculated value is equal to the equation (4) and substituting the measured value or the constant r _w for the spectral distribution R _2w (λ) in the equation (4), the unknown number is limited to the coefficient k _W only. be able to.

As a result, it is possible to calculate the coefficients k _W by various numerical methods, the white reflected by the product of the coefficient k _W of the calculated result (x (λ) + y ( λ) + z (λ)) The spectral distribution of the component can be acquired. Of course, in step S235 of FIG. 5, the measured value may be used without setting the spectral distribution R _2w (λ) to the constant r _w .

Furthermore, in the above-described embodiment, the white plate is color-measured even under the first observation condition. However, the colorimeter 40 that performs color measurement under the first observation condition includes a light source. Alternatively, a predetermined spectral distribution of the light source may be acquired. Of course, in this case, the work of measuring the color of the white plate under the first observation condition becomes unnecessary. Further, in the above embodiments, the spectral distribution of the white reflection component is assumed to be the product of a coefficient k _W with (x (λ) + y ( λ) + z (λ)), course, linear color matching functions When performing the combination, a different coefficient may be multiplied for each color matching function, or another function depending on the wavelength may be assumed, and various configurations may be employed.

Further, in the above-described embodiment, assuming that the coefficient k _W in the spectral distribution of the white reflection component depends on the type of colorant used for printing the type and print media source, this condition is actually prints However, of course, the second observation condition may be defined including other elements. For example, the spectral distribution of the white reflection component may be determined as depending on the relative positional relationship between the light source, the sample for evaluation, and the colorimeter 50.

  FIG. 7 is an explanatory diagram for explaining an example in which the angle between the light source and the sample for evaluation and the angle between the sensor of the colorimeter 50 and the sample for evaluation are considered as the relative positional relationship. In this figure, the angle between the light source and the sample for evaluation is the vertical line of the sample for evaluation (of course, the color is measured with the same positional relationship even with a white plate) and the light path from the light source (light source and observation point). The angle between the sensor and the sample for evaluation is the angle θ between the perpendicular of the sample for evaluation and the optical path of light incident on the sensor (the line connecting the observation point and the sensor). It is.

  Here, if the angle φ and the angle θ are equal, the specularly reflected light is observed, and if the angle φ and the angle θ are not equal, the diffusely reflected light is observed. According to the applicant's experiment, it has been found that in a printed matter with a certain pigment, the white reflection component varies depending on the deviation from the regular reflection, and the white reflection component decreases as the deviation from the regular reflection increases. It has been found.

Therefore, if the spectral distribution of the white reflection component is defined in consideration of the angle dependency of the white reflection component in such a printed matter, correction can be performed more accurately. For this purpose, for example, instead of the coefficient k _W, the coefficient with the angle-dependent beta / | it is possible to introduce | phi-theta. That is, as the deviation from regular reflection increases, the coefficient β / | φ−θ | decreases, and the product of this coefficient and (x (λ) + y (λ) + z (λ)) is the spectral distribution of the white reflection component. Assume that

  Further, the coefficient is determined by a plurality of combinations of the angle φ and the angle θ. For example, in carrying out the flowchart of FIG. 5 in the same configuration as in FIG. 2, the angle φ related to the light source and the angle θ related to the colorimeter 50 are measured with respect to the color chart and the white plate. In the colorimeter 50, it is not necessary to limit the number of light sources to one. However, if a main light source used when measuring a color chart or a white plate is specified, the light source and the sample for evaluation are used. An angle can be defined.

  When the angle is measured, the same processing as the flow shown in FIG. 5 is performed, and the value of β is determined assuming that the coefficient calculated by the above equation (10) is the coefficient β / | φ−θ |. When the value of β is determined for this angle combination, the combination of the values of the angle φ and the angle θ is changed, and the same process is repeated a plurality of times. As a result, a plurality of βs depending on the angle can be obtained, and if the colorimetric value in the second observation condition is calculated from the colorimetric value in the first observation condition, the angle φ and the angle θ are specified. It is possible to acquire the spectral distribution of the white reflection component depending on the angle and perform correction depending on the angle.

  Of course, if a plurality of β corresponding to the combination of the values of the angle φ and the angle θ is obtained, the coefficient β / | φ−θ | which is not actually measured by the angle φ and the angle θ. However, it can be calculated by interpolation. Therefore, the coefficient β / | φ−θ | can be determined for a combination of an arbitrary angle φ and angle θ. Therefore, the combination of the angle φ and the angle θ is calculated from the relationship between the light source, the human eye, and the printed material when actually observing the printed material, and the coefficient β / | φ−θ | Correction in step S110 is performed. As a result, it is possible to create a color conversion profile 14f for performing good color reproduction under conditions closer to the observation conditions when actually observing the printed matter.

1 is a block diagram of a color conversion profile creation device according to the present invention. FIG. It is a block diagram which shows the structure of a color conversion profile creation program. It is a flowchart which shows the process which produces a color conversion profile. It is explanatory drawing which illustrates roughly the spectral distribution calculation method concerning this invention. It is a flowchart illustrating a process for calculating the coefficient k _W. It is a block diagram of a colorimeter provided with a profile for correction. It is explanatory drawing explaining the example which considers angle dependence.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... CPU, 12 ... ROM, 13 ... RAM, 14 ... Hard disk, 14a ... Patch image data, 14b ... Colorimetric value data, 14c ... Color matching function data, 14d ... Coefficient data, 14e ... Separation data , 14f ... color conversion profile, 15 ... printer, 20 ... spectral distribution calculation program, 21 ... colorimetric value acquisition unit, 22 ... basic reflection component calculation unit, 23 ... average value calculation unit, 24 ... white reflection component calculation unit, 30 ... Printer driver, 31 ... Image data acquisition module, 32 ... Color conversion module, 33 ... Halftone processing module, 34 ... Print processing module, 40, 50 ... Colorimeter, 41 ... Sensor, 41a ... Sensor driver, 42 ... A / D conversion unit, 43 ... CPU, 43a ... colorimetry control unit, 43b ... correction unit, 44 ... RAM, 45 ... ROM, 45a ... complement Profile, 46 ... operation unit, 47 ... output unit, 49 ... light source, 49 a ... light source control unit, 60 ... color conversion profile creation program, 61 ... color separation processing unit, 62 ... colorimetric value acquisition unit, 63 ... colorimetric value Correction unit, 64 ... target generation unit, 65 ... interpolation calculation unit

Claims (14)

A profile creation device for creating a profile that associates image data with an output colorimetric value based on the image data,
Colorimetric value acquisition means for acquiring a colorimetric value obtained by measuring the output result based on the image data under a first observation condition;
A colorimetric value conversion means for converting the colorimetric value measured by the colorimetric acquisition means into a colorimetric value when the output result is measured under the second observation condition;
A profile creation device comprising profile creation means for creating a profile by associating the converted colorimetric values with the image data. The first observation condition is an observation condition in a colorimeter that performs colorimetry using a predetermined light source, and the second observation condition is in a colorimeter that performs colorimetry using an arbitrary light source. The profile creation apparatus according to claim 1, wherein the profile creation apparatus is an observation condition. The colorimetric value conversion means performs the conversion based on spectral distribution data calculated as a spectral distribution component for a colorimetric object, which varies depending on an observation condition. The profile creation apparatus according to claim 1 or 2. The spectral distribution data is calculated based on a colorimetric value obtained by measuring the color of the sample for evaluation under the first observation condition and a colorimetric value obtained by measuring the color of the sample for evaluation under the second observation condition. Based on the colorimetric value obtained by measuring the color of a predetermined white plate under the first observation condition and the colorimetric value obtained by measuring the color of the predetermined white plate under the second observation condition, the colorimetric object is irradiated under each observation condition. The profile creation apparatus according to claim 3, wherein a spectral distribution of light is acquired. 4. The spectral distribution data according to claim 3, wherein the spectral distribution data is calculated as a product of a component of a spectral distribution that varies depending on the observation condition and a function that depends on a predetermined wavelength. The profile creation apparatus according to claim 4. 6. The profile creation apparatus according to claim 5, wherein the function depending on the predetermined wavelength is a linear combination of color matching functions. The spectral distribution component that varies depending on the observation conditions depends on one or a combination of a print medium for printing the color measurement object, a color material for printing the color measurement object, and a light source type. The profile creation device according to claim 3, wherein the profile creation device is defined as follows. The component of the spectral distribution that varies depending on the observation condition depends on the relative positional relationship between the light source, the color measurement object, and the light receiving unit of the colorimeter when the color measurement object is observed under the second observation condition. The profile creation device according to claim 3, wherein the profile creation device is defined as a function to perform. The image data is data handled by the first image device, and the image is based on the created profile and the correspondence between the second image data handled by the second image device and the colorimetric value of the output. 9. The profile creation apparatus according to claim 1, further comprising color conversion profile creation means for creating a color conversion profile that defines a correspondence relationship between the data and the second image data. A print control device that performs printing by performing color conversion with reference to a color conversion profile,
The color conversion profile acquires a colorimetric value obtained by measuring the output result based on the image data handled by the first image device under the first observation condition, and outputs the colorimetric value under the second observation condition. The result is converted into a colorimetric value when the colorimetry is performed, the colorimetric value thus converted is associated with the image data, the correspondence relationship, the second image data handled by the second image device, and its output A print control apparatus, characterized in that it is data created by defining a correspondence between the image data and the second image data based on a correspondence with a colorimetric value. A profile creation method for creating a profile that associates image data with an output colorimetric value based on the image data,
A colorimetric value acquisition step of acquiring a colorimetric value obtained by measuring the output result based on the image data under a first observation condition;
A colorimetric value conversion step of converting the colorimetric value measured by the colorimetric acquisition step into a colorimetric value when the output result is measured under the second observation condition;
A profile creation method comprising: a profile creation step of creating a profile by associating the converted colorimetric values with the image data. A print control method for performing color conversion with reference to a color conversion profile and executing printing,
The color conversion profile acquires a colorimetric value obtained by measuring the output result based on the image data handled by the first image device under the first observation condition, and outputs the colorimetric value under the second observation condition. The result is converted into a colorimetric value when the colorimetry is performed, the colorimetric value thus converted is associated with the image data, the correspondence relationship, the second image data handled by the second image device, and its output A print control method characterized in that the print control method is data created by defining a correspondence relationship between the image data and the second image data based on a correspondence relationship with a colorimetric value. A profile creation program for creating a profile that associates image data with an output colorimetric value based on the image data,
A colorimetric value acquisition function for acquiring a colorimetric value obtained by measuring the output result based on the image data under a first observation condition;
A colorimetric value conversion function for converting a colorimetric value measured by the colorimetric acquisition function into a colorimetric value obtained when the output result is measured under a second observation condition;
A profile creation program for causing a computer to realize a profile creation function for creating a profile by associating the converted colorimetric values with the image data. A print control program that performs color conversion with reference to a color conversion profile and executes printing,
An image data acquisition function for acquiring image data handled by the first image device;
When a colorimetric value obtained by measuring the output result based on the image data handled by the first image device under the first observation condition is obtained and the output result is measured under the second observation condition. And the corresponding colorimetric value and the image data are associated with each other, and this correspondence is associated with the second image data handled by the second image device and the output colorimetric value. A color conversion function for performing color conversion processing on the acquired image data with reference to a color conversion profile created in advance by defining the correspondence between the image data and the second image data based on the relationship When,
A printing control program for causing a computer to realize a printing control function for controlling a printing apparatus based on data after color conversion.

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