JP2022050987A - Image processing device, image processing method, and program - Google Patents

Abstract

To solve a problem of reducing a color reproduction range of a color image when the color image formed on a recording medium including a fluorescent whitener is observed under a light source including ultraviolet light.SOLUTION: Color separation is performed to inputted image data. Records by a plurality of recording materials to be used in forming a color image on a recording medium including a fluorescent whitener are controlled on the basis of the image data after the color separation. The control of the records is performed so as to reduce a color reproduction range to a color area corresponding to a specific recording material among the plurality of recording materials on the basis of color measurement data acquired from color information acquired by respectively performing measurement when a light source including ultraviolet light irradiates a test pattern recorded on the recording medium including the fluorescent whitener and when a light source including no ultraviolet light irradiates the test pattern.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to techniques for improving the color reproducibility of images.

An image forming apparatus such as an inkjet printer or an electrophotographic printer is known as an apparatus for forming an image by using a coloring material such as ink or toner as a recording medium.

In recent years, there has been an increasing opportunity to use a large-format inkjet printer to output printed matter for signage for the purpose of posting outdoors under a solar light source or semi-outdoors such as public transportation and commercial facilities. When obtaining a printed matter, a recording medium having an ink receiving layer to which a fluorescent whitening agent is added may be used on the surface on which the ink is recorded. It is known that when the fluorescent whitening agent added to the ink receiving layer of a recording medium is irradiated with ultraviolet light contained in an observation light source, fluorescence is generated and the whiteness of the printed matter is increased. On the other hand, the color of the color image on the printed matter changes because the fluorescence generated by the fluorescent whitening agent mixes with the normal reflected light from the printed matter. The amount of fluorescence generated from the printed matter depends on the amount of the fluorescent whitening agent added, the amount of ultraviolet light irradiation, and the like. Various techniques for improving the color reproducibility of color images have been developed. Patent Document 1 creates a look-up table (hereinafter referred to as LUT) for correcting a color value for each recording medium having a different amount of fluorescent whitening agent added, and uses the created LUT to create an image for printing. It discloses a technique for correcting the color value of data.

Japanese Unexamined Patent Publication No. 2002-292909

When a color image formed on a recording medium containing a fluorescent whitening agent is observed under a light source containing ultraviolet light, a color reproduction range is obtained in an image region formed of a color material having spectral characteristics close to the complementary color of the generated fluorescence color. Becomes smaller. For example, in the case of a fluorescent color having a blue-based color component, the color having a complementary color relationship is yellow. Therefore, it is presumed that the tint of the yellow ink is canceled by the fluorescent color and the saturation of the color visually recognized by the observer is lowered. When observed under a light source containing such ultraviolet light, the larger the amount of ultraviolet light, the more fluorescence is generated, and the saturation of the complementary colors is reduced accordingly. Further, as the amount of ink used to form the image region decreases, the ratio (coverage ratio) of covering the recording medium with the ink decreases. As the coverage of the ink decreases, more optical brightener in the ink receiving layer of the recording medium is exposed, so that the color of the ink used to form the image region is susceptible to the fluorescence tint. Become.

This is a problem that can occur even with the technique disclosed in Patent Document 1.

The present disclosure provides a technique for suppressing a reduction in the color reproduction range of a color image even when a color image formed on a recording medium containing a fluorescent whitening agent is observed under a light source containing ultraviolet light.

The image processing apparatus according to one aspect of the present disclosure, which solves the above-mentioned problems, is an image processing apparatus that performs processing for forming a color image on a recording medium containing a fluorescent whitening agent, and is an image processing apparatus that performs processing for forming a color image on a recording medium containing a fluorescent whitening agent. A color separation means for converting a color space into a color space corresponding to a plurality of recording materials, and the plurality of recording materials used when forming the color image based on the image data after the color separation. It has a control means for controlling recording, and the control means has a test pattern recorded on a recording medium containing a fluorescent whitening agent when it is irradiated with a light source containing ultraviolet light and with a light source containing no ultraviolet light. Based on the color measurement data obtained from the color information obtained by measuring each of the irradiation, the reduction of the color reproduction range is suppressed for the color region corresponding to the specific recording material among the plurality of recording materials. It is characterized in that the recording is controlled so as to be performed.

According to the present disclosure, even if a color image formed on a recording medium containing a fluorescent whitening agent is observed under a light source containing ultraviolet light, it is possible to suppress a reduction in the color reproduction range of the color image.

Block diagram showing a configuration example of an image processing device Diagram showing an example of printer hardware configuration Flow chart showing the flow of processing executed by the image processing device Diagram showing vertices in the color separation table The figure which shows the change example of the color reproduction range by the influence of fluorescence generated from a recording medium. The figure explaining the judgment example of the color reproduction range change Flowchart showing the procedure for creating a color separation table The figure which shows the example of the color separation table of a YY line. The figure which shows the example of the color separation table of the WC line. The figure explaining the application example of the recording order control mask The figure which shows the example of a recording order control mask The figure which shows typically the cross section of the printed matter which formed the image by the gradation of the intercolor line which reduces the color reproduction range. The figure which shows typically the cross section of the printed matter which formed the image by the gradation of the intercolor line which increases the color reproduction range. The figure which shows the example of the color separation table of a YY line. The figure which shows typically the cross section of the printed matter which formed the image by the gradation of the intercolor line which reduces the color reproduction range.

Hereinafter, this embodiment will be described with reference to the drawings. The following embodiments do not necessarily limit the present invention. Moreover, not all combinations of features described in the present embodiment are essential for the means of solving the present invention.

[First Embodiment]
<Hardware configuration of image processing device>
1A and 1B are block diagrams showing a configuration example of an image processing apparatus according to the present embodiment, FIG. 1A shows a hardware configuration example of the image processing apparatus, and FIG. 1B shows a function of the image processing apparatus. A configuration example is shown. In FIG. 1A, the image processing device 1 is, for example, a computer or the like. The image processing device 1 has a CPU 101, a ROM 102, a RAM 103, a general-purpose interface (I / F) 104, a serial ATA (SATA) I / F 105, and a video I / F 106. The CPU 101 uses the RAM 103 as a work memory to execute an operating system (OS) and various programs stored in a ROM 102, a hard disk drive (HDD) 15, various recording media, and controls each block via the system bus 107. The program executed by the CPU 101 includes a program that executes a process described later.

The general-purpose I / F 104 is, for example, a serial bus interface such as USB, and an input device 12 such as a mouse or a keyboard and a printer 13 are connected to the general-purpose I / F 104 via the serial bus 11. A general-purpose drive 16 for reading / writing HDD 15 and various recording media is connected to the SATA I / F 105 via the serial bus 14. The CPU 101 uses various recording media mounted on the HDD 15 and the general-purpose drive 16 as a data storage location for reading and writing.

The video I / F 106 is, for example, a video card (VC), and a display 17 is connected to the video I / F 106. The CPU 101 displays a user interface (UI) provided by the program on the display 17, and receives user input including user instructions via the input device 12. The image processing device 1 may be included in the printer 13.

<Printer configuration>
FIG. 2 is a block diagram showing a hardware configuration example of the printer 13. The printer 13 is a multi-pass inkjet printer that produces a printed matter in which a color image is formed on a recording medium by relatively scanning the recording medium and the recording head a plurality of times. Based on the data (print data) received from the image processing device 1, the printer 13 ejects ink to a recording medium containing a fluorescent whitening agent to form a color image and generate a printed matter. In the following description, even if it is simply described as "recording medium", it means "recording medium containing a fluorescent whitening agent".

The head cartridge 201 is provided with a recording head including a plurality of ejection ports, an ink tank for supplying ink to the recording head, and a connector for receiving a signal for driving each ejection port of the recording head. There is. The ink tank contains a total of five types of ink, cyan (C), magenta (M), yellow (Y), black (K), and white (W) for forming the color ink layer (color layer). The contained ink tank is provided independently. These inks are water-based pigment inks.

The head cartridge 201 is mounted on the carriage 202 in a replaceable manner. The carriage 202 is provided with a connector holder for transmitting a drive signal or the like to the head cartridge 201 via the connector. The carriage 202 is configured to be reciprocally movable along the guide shaft 203. Specifically, the carriage 202 is driven by a drive mechanism such as a motor pulley 205, a driven pulley 206, and a timing belt 207 with the main scanning motor 204 as a drive source, and its position and movement are controlled. The movement of the carriage 202 along the guide shaft 203 is referred to as "main scanning", and the moving direction is referred to as "main scanning direction". The printing recording medium 208 is mounted on the auto sheet feeder (ASF) 210. When an image is formed on the recording medium 208, the pickup roller 212 rotates with the drive of the paper feed motor 211, and the recording media 208 are separated from the ASF 210 one by one and fed. Further, the recording medium 208 is conveyed to the recording start position on the carriage 202 facing the discharge port surface of the head cartridge 201 by the rotation of the transfer roller 209. The transfer roller 209 is driven via gears using the line feed motor 213 as a drive source. Whether or not the recording medium 208 has been supplied and the determination of the paper feed position are performed when the recording medium 208 passes through the end sensor 214. The head cartridge 201 mounted on the carriage 202 is held so that the discharge port surface projects downward from the carriage 202 and is parallel to the recording medium 208. The operation control unit 220 is composed of a CPU, a storage unit, and the like, receives print data from the outside, and controls the operation of each part based on the received data.

<Image formation operation by printer>
The image forming operation of each part controlled by the operation control unit 220 will be described. First, when the recording medium 208 is conveyed to the recording start position in order to form the color layer, the carriage 202 moves on the recording medium 208 along the guide shaft 203. During the movement, cyan (C), magenta (M), yellow (Y), black (K), and white (W) color inks (CMYKW inks) are ejected from the ejection port of the recording head. When the carriage 202 moves to one end of the guide shaft 203, the transport roller 209 conveys the recording medium 208 by a predetermined amount in a direction orthogonal to (intersects) the scanning direction of the carriage 202. The transport of the recording medium 208 is referred to as "paper feed" or "sub-scanning", and this transport direction is referred to as "paper feed direction" or "sub-scanning direction". When the recording medium 208 has been conveyed by a predetermined amount in the sub-scanning direction, the carriage 202 moves along the guide shaft 203 again. By repeating scanning by the carriage 202 of the recording head and paper feeding in this way, a color layer for controlling the diffuse color is formed on the entire recording medium 208. For the sake of simplicity, the recording head of the printer 13 is controlled by a binary value of whether or not to eject ink droplets, and a state in which all ink droplets are turned on in one pixel area of image data having a predetermined resolution. Treat as 100% ink amount. A recording head in which the ink ejection amount can be modulated is generally used, but it can be applied by extending the above-mentioned binarization process to a multi-valued process to multiple levels that can be modulated. It is not limited to binarization.

<Logical configuration of image processing device>
The logical configuration of the image processing apparatus 1 will be described with reference to FIG. 1 (b). The image processing device 1 includes an input image data acquisition unit 111, a color matching processing unit 112, a color change acquisition unit 113, a determination unit 114, a color separation table creation unit 115, a color separation processing unit 116, a halftone processing unit 117, and a mask creation. It has a unit 118 and a print control unit 119.

The input image data acquisition unit 111 acquires the input image data 121 for printing. The input image data 121 is 8-bit color image data of each of R, G, and B, and is acquired from the input device 12 via the general-purpose I / F 104, the HDD 15 via the SATA I / F 105, and the like.

The color matching processing unit 112 executes a color conversion process for the input image data to match the color reproduction range of the input image data R, G, and B acquired by the input image data acquisition unit 111 with the color reproduction range of the printer 13. By executing the color conversion process for the input image data, the color matching processing unit 112 generates the image data (R'G'B' color image data) after the color conversion. The color conversion process is, for example, a process using a look-up table (LUT), which is a color conversion table created in advance. When matching with the color reproduction range of the printer 13, a color image is formed on a recording medium by the printer 13 based on the print data obtained by each processing of the functional units 116, 117, and 119 performed after the color conversion processing. Colors are matched using the printed material. The color conversion process is not limited to the process using the LUT, and may be, for example, a known color matching process such as matrix conversion or mathematical expression conversion.

The color change acquisition unit 113 acquires color change information indicating a color change due to the color of fluorescence emitted from a recording medium when irradiated with a light source containing ultraviolet light. In the acquisition of color change information, first, a printed matter in which a test pattern (also referred to as a test chart) composed of a plurality of color patches is recorded on a recording medium is created. The color of each color patch is measured when the created printed matter is irradiated with a light source that does not contain ultraviolet light and when it is irradiated with a light source that contains ultraviolet light, and the color of each color patch is measured and used as recording medium information 122 under each light source. Get color information. Then, the color change information is acquired as color measurement data by obtaining the difference between these color information. The color to be measured is a Lab value, and the diffuse reflection component of the printed matter is measured using a colorimeter or a spectral radiance meter.

Based on the color change information acquired by the color change acquisition unit 113, the determination unit 114 has a color reproduction range in which the colors located in each line (frame of the color separation table) between the grid points in the color separation table are affected by the generation of fluorescence. Determine how is changing. In the determination process by the determination unit 114, it is determined whether the color reproduction range under a light source containing ultraviolet light is smaller, larger, or the same as the color reproduction range under a light source not containing ultraviolet light. Will be done.

The color separation table creation unit 115 creates a color separation table to be used by the color separation processing unit 116 according to the determination result by the determination unit 114. The color separation table is in LUT format, for example, a three-dimensional LUT having 17 × 17 × 17 grid points. As will be described in detail later, the color separation table can be said to be a table in which the color space in the input image data corresponds to the color space in a plurality of color inks.

The color separation processing unit 116 receives the image data (R'G'B' color image data) after color conversion generated by the color matching processing unit 112 as an input, and is mounted on the printer 13 using the color separation table. Convert to recording material data indicating the amount of color ink (recording material). If the printer 13 is equipped with five color inks (recording materials) of cyan (C), magenta (M), yellow (Y), black (K), and white (W), the image after color conversion As data, recording material data representing the amount of each color ink of CMYKW in 8 bits is generated. It can be said that the image data after color conversion is the image data after color separation.

The halftone processing unit 117 executes halftone processing on the recording material data received from the color separation processing unit 116 by using the dither method, and binary data C'representing ON / OFF of dots in the printer 13. , M', Y', K', W'. The halftone process is not limited to the process using the dither method, and may be a process using a known method such as an error diffusion method.

The mask creating unit 118 creates a path mask (recording order control mask) used by the print control unit 119 according to the determination result of the determination unit 114.

The print control unit 119 processes the binary data generated by the halftone processing unit 117 by using the recording order control mask created by the mask creation unit 118 to form a color image on the printer 13. Create recording scan data. Each recording scan data is print data used by the printer 13 for forming a color image by recording on a recording medium using a plurality of color inks, and is sent to the printer 13.

<Operation of image processing device>
The flow of processing executed by the image processing apparatus will be described with reference to the drawings. FIG. 3 is a flowchart showing the flow of processing executed by the image processing apparatus. The process according to the flowchart shown in FIG. 3 is executed by the CPU 101 after the program code stored in the ROM 102 is expanded in the RAM 103. The flowchart shown in FIG. 3 starts when the user operates the input device 12 to input an instruction and the CPU 101 accepts the input instruction. The symbol "S" in the description of the flowchart represents a step. The same applies to the description of the following flowchart.

First, in S301, the input image data acquisition unit 111 acquires color image data of 8 bits each of R, G, and B, which are input image data input from the outside.

In S302, the color matching processing unit 112 uses a LUT for matching the color reproduction range of the input image data R, G, and B with the color reproduction range of the printer 13, and performs color conversion processing on the input image data acquired in S302. (Color matching process) is executed. By this color conversion process, the RGB input image data is converted into 8-bit R'G'B'color image data.

In S303, it is determined whether or not the color separation table and the recording order control mask have been created. When the determination result that the color separation table and the recording order control mask have not been created is obtained (NO in S303), the process is transferred to S304. By executing a series of processes from S304 to S307, a color separation table and a recording order control mask are created. On the other hand, when the determination result that the color separation table and the recording order control mask have been created is obtained (YES in S303), S304 to S307 are skipped and the process is shifted to S308. In S303, the determination process of whether or not the color separation table and the recording order control mask have been created is performed at the same time, but the determination of whether or not the color separation table and the recording order control mask have been created is separately performed. May be done in. If either the color separation table or the recording order control mask has been created, the procedure may be such that only the uncreated one is created.

In S304, the color change acquisition unit 113 acquires color change information indicating a color change due to the influence of fluorescence generated from the recording medium by being irradiated with a light source including ultraviolet light. First, a printed matter in which a plurality of color patches, which are test charts, are recorded on a recording medium is created. The Lab value representing the color of each color patch is measured for the created printed matter when it is irradiated with a light source that does not contain ultraviolet light and when it is irradiated with a light source that contains ultraviolet light, and the color information under each light source is obtained. get. Then, the color change information is acquired by obtaining the difference between these color information. The color patch includes, for example, a patch of input values for a total of eight colors. As shown in FIG. 4, this patch uses R, G, B, C, M, Y, K, and W, which are the eight vertices of the color separation table, as input values. The input values in the patch are R (255, 0, 0), G (0, 255, 0), B (0, 0, 255), C (0, 255, 255), M (255, 0, 255), Y (255, 255, 0), K (0, 0, 0), W (255, 255, 255). Here, it suffices if it is possible to obtain color change information indicating what kind of color the color of the color patch changes due to the influence of fluorescence generated from the recording medium by being irradiated with a light source including ultraviolet light, and it is sufficient to obtain the hue difference and Lab. It may be a color measurement value of a color other than XYZ, a color name representing a color, or the like. An example in which the color reproduction range changes due to the influence of fluorescence generated from the recording medium by being irradiated with a light source including ultraviolet light will be described later.

In S305, the determination unit 114 corresponds to the color located in each line (eight frames of the color separation table) between the grid points in the color separation table based on the color change information of each color patch acquired in S304. Determine how the color reproduction range changes due to the influence of the generation of fluorescence. An example of determining a change in the color reproduction range will be described later.

In S306, the color separation table creating unit 115 creates a color separation table based on the determination result by the determination unit 114 in S305. The details of the process of creating the color separation table will be described later.

In S307, the mask creating unit 118 creates a path mask (recording order control mask) used by the print control unit 119 according to the determination result by the determination unit 114 in S305. The details of the recording order control mask will be described later.

In S308, the color separation processing unit 116 uses the color separation table created in S306 to execute color separation processing on the color-converted image data received as input from the color matching processing unit 112. By executing the color separation process, the received image data after color conversion is converted into recording material data representing the amount of each color ink of CMYKW mounted on the printer in 8 bits. In the color separation table, the ink values (8 bits) for five colors C, M, Y, K, and W are stored on the grid points thinned out to 17 × 17 × 17, and the values between the grid points are stored. Is calculated by linear interpolation. When the color separation table and the recording order control mask are created in advance and stored in a storage device such as ROM 102 or HDD 15, the created color separation table and the recording order control mask are read out from the storage device. When image formation is performed by a printer, it is required that the time required to obtain a printed matter is as short as possible. Therefore, if the recording medium used for image formation is predetermined, the following processing may be performed. good. That is, the color separation table and the recording order control mask may be created and stored in the storage device at the time of product design of the printer and the image processing device, and the color separation table and the recording order control mask may be read out from the storage device at the time of use. ..

In S309, the halftone processing unit 117 executes halftone processing using the dither method on the recording material data received as input from the color separation processing unit 116. In the halftone processing, the recording material data is converted into binary data C', M', Y', K', W'used by the printer, which represent ON / OFF of the dots of the printer. The halftone process is not limited to the process using the dither method, and may be a process using a known method such as an error diffusion method.

In S310, the print control unit 119 forms binary data C', M', Y', K', W'created in S309 by each recording scan using the recording order control mask created in S307. Executes print control that decomposes into dot patterns. In the print control of the present embodiment, as the data indicating the dot pattern, each recorded scanning data for completing the color image by the multi-pass method in which the number of scannings is 4 passes is created.

Finally, in S311, each recording scan data created in S310 is used, a printed matter in which a color image is formed on the recording medium is created by the printer 13, and the processing of this flow is completed.

This completes the process executed by the image processing device 1.

<Changes in color reproduction range due to the effect of fluorescence>
The change in the color reproduction range due to the influence of fluorescence generated from the recording medium by irradiation with a light source including ultraviolet light (hereinafter, also referred to as the influence of fluorescence) will be described with reference to the figure. FIG. 5 is a diagram showing an example of a change in the color reproduction range due to the influence of fluorescence generated from a recording medium when irradiated with a light source containing ultraviolet light, and FIG. 5 (a) shows a bl plane in the Lab space. 5 (b) shows the ab plane in the Lab space. A test chart consisting of multiple color patches is printed on a recording medium, and the Lab value representing the color of each color patch is measured when irradiated with a light source that does not contain ultraviolet light and when irradiated with a light source that contains ultraviolet light. , Changes in the color reproduction range are required based on the measurement results. The recording medium is assumed to have a predetermined amount of fluorescent whitening agent added, and the light source containing ultraviolet light is assumed to contain a predetermined amount of ultraviolet light. In FIGS. 5A and 5B, the white circle plots indicated by W0, K0, C0, M0, Y0, R0, G0, and B0 are in white, black, cyan, magenta, yellow, red, green, and blue, respectively. Corresponding, it is a color measurement value of each color patch under a light source that does not contain ultraviolet light. The black circle plots indicated by W1, K1, C1, M1, Y1, R1, G1, and B1 correspond to white, black, cyan, magenta, yellow, red, green, and blue, respectively, under a light source containing ultraviolet light. It is the color measurement value of each color patch of. In FIGS. 5A and 5B, the area surrounded by the broken line, which includes the white circle plot, corresponds to the color reproduction range when measured under a light source that does not contain ultraviolet light, and includes the black circle plot. The area surrounded by the solid line corresponds to the color reproduction range when measured under a light source containing ultraviolet light.

At this time, the part shown by the diagonal line pattern (the part with hatching) has a color reproduction range measured under a light source containing ultraviolet light due to the influence of fluorescence, and is measured under a light source not containing ultraviolet light. It is a color region (color region) that is smaller than the color reproduction range when the light source is used. On the other hand, in the part indicated by the point pattern (the part with dots), the color reproduction range when measured under a light source containing ultraviolet light was measured under a light source not containing ultraviolet light due to the influence of fluorescence. It is a color region (color region) that is larger than the current color reproduction range. In this way, the change in color that occurs when irradiated with a light source containing ultraviolet light, that is, the difference in the color reproduction range, differs depending on the color of the color patch.

In this embodiment, focusing on the above-mentioned phenomenon in which the color reproduction range is different, image processing and image processing are performed so that the reduction of the color reproduction range is suppressed for the color region where the color reproduction range becomes small due to the influence of fluorescence. Image formation is performed. That is, the corresponding color region is determined, and in the determined color region, a color separation table and a recording order control mask are created so that the surface of the recording medium is not exposed as much as possible, and the created color separation table and recording order control mask are created. Is used to form a color image on a recording medium.

On the other hand, for the color region where the color reproduction range becomes large due to the influence of fluorescence, image processing and image formation are performed so as to utilize the expansion of the color reproduction range by fluorescence. That is, the corresponding color region is determined, and in the determined color region, a color separation table and a recording order control mask are created so that the surface of the recording medium is exposed as much as possible, and the created color separation table and recording order control are created. A color image is formed on a recording medium using a mask.

In order to realize these, the change in the color reproduction range due to the influence of fluorescence is measured and judged for each color region, a color separation table and a recording order control mask according to the judgment result are created, and the created data is used as the next step. Produces a printed matter that forms a color image such as. That is, in the color region corresponding to the color image of the printed matter, the reduction of the color reproduction range due to the influence of the fluorescent color generated from the printed matter by being irradiated by the light source including ultraviolet light is suppressed or the color reproduction range is expanded. In addition, the coverage of the surface of the recording medium to be coated with the ink is different. However, this recording medium contains an optical brightener.

<Judgment of change in color reproduction range>
The determination of the change in the color reproduction range will be described with reference to the figure. FIG. 6 is a diagram illustrating an example of determining a change in the color reproduction range. The cube shown in FIG. 6 represents a color separation table, and like FIG. 4, the color name of each grid point is shown. In the determination of the change in the color reproduction range, the change in the color reproduction range that can be expressed by the ink mounted on the printer 13 that records the color image corresponding to the input image data on the recording medium is determined based on the acquired color change information. Will be done. The part shown by the thick solid line is an intercolor line whose color reproduction range becomes smaller due to the influence of fluorescence. In the present embodiment, the four intercolor lines YY, RY, RK, and YY have a small color reproduction range due to the influence of fluorescence based on the change in the color reproduction range shown in FIG. It is determined that it corresponds to the color region.

On the other hand, the portion shown by the broken line is an intercolor line in which the color reproduction range becomes large due to the influence of fluorescence. In the present embodiment, the four intercolor lines WC, MR, MB, and BC have a large color reproduction range due to the influence of fluorescence based on the change in the color reproduction range shown in FIG. It is determined that it corresponds to the color region.

Further, it is determined that the other intercolor lines other than the above, WM, KG, KB, and GC, correspond to the color region in which the color reproduction range does not change due to the influence of fluorescence.

In this way, the change in the color reproduction range due to the influence of fluorescence is determined by the color region of the color separation table.

<Process for creating a color separation table>
The detailed flow of the process of creating the color separation table of S306 will be described with reference to the drawings. FIG. 7 is a flowchart showing a detailed flow of the process of creating the color separation table of S306.

First, in S701, the color separation table creation unit 115 patches in advance with a printer a combination of values obtained by dividing the values of 0 to 255 represented by 8 bits for C, M, Y, K, and W into 16 equal parts. Print, measure them, get and hold each color measurement value.

In S702, the color separation table creation unit 115 sets the grid point data (color separation data) of the eight grid points corresponding to the vertices of the color separation table. For example, the vertex W is (C, M, Y, K, W) = (0, 0, 0, 0, 255), and the vertex Y is (C, M, Y, K, W) = (0, 0, 255). , 0, 0), the vertex C is set as (C, M, Y, K, W) = (255, 0, 0, 0, 0). The vertex M is (C, M, Y, K, W) = (0, 255, 0, 0, 0), and the vertex K is (C, M, Y, K, W) = (0, 0, 0). , 255, 0).

In S703, the color separation table creating unit 115 corresponds to a specific color ink among a plurality of color inks, in which the color reproduction range becomes smaller due to the influence of fluorescence generated from the recording medium by being irradiated by a light source containing ultraviolet light. Design a color separation table for the intercolor line. The intercolor line to be designed in S703 is the intercolor line YY, RY, RY, in which the color reproduction range is determined to be smaller due to the influence of fluorescence in the color reproduction range change determination process in S305. K and YG. In each intercolor line, the grid point data (color separation data) of the grid points on each line is obtained as follows, and a color separation table for these grid points is created. More specifically, for example, in the line connecting the vertices W and the vertices Y, the color measurement values of the patches are obtained for the vertices W and the vertices Y as follows. That is, (C, M, Y, K, W) = (0, 0, 0, 0, 255) corresponding to the vertex W set in S702, and (C, M, Y, The color measurement values of the printed patches are obtained based on the set of values of K, W) = (0, 0, 255, 0, 0). Then, the grid points are defined so as to be evenly distributed on the line connecting the above two color measurement values on the uniform color space. The values of the data (C, M, Y, K, W) that output the patch of the color measurement values of these evenly distributed grid points and the patch of the color measurement values closest to each are obtained as the grid point data of each grid point.

The color separation table of the YY line will be described with reference to the drawings. FIG. 8 is a diagram showing an example of a color separation table of a YY line, FIG. 8A shows an example of a color separation table of the present embodiment, and FIG. 8B shows an example of a conventional color separation table. show. As shown in FIG. 8B, in the conventional color separation table, when the gradation of yellow changes from W (minimum gradation) to Y (maximum gradation), the amount of ink of yellow ink 803 is changed to W. It is designed so that it increases as it changes from 0% to Y and becomes 100% at Y. However, in this case, the closer to W, the more the surface of the recording medium is exposed, so that more blue-based fluorescent colors are generated, and the tint of the yellow ink is canceled by the fluorescent colors to become white. That is, the saturation of the color visually recognized by the observer is reduced.

Therefore, in the present embodiment, the intercolor line to be designed in S703 is irradiated with a light source containing ultraviolet light so that the influence of fluorescence generated from the recording medium is minimized. Determine the value of the data. Here, the yellow (Y) ink, which is a color ink having a complementary color relationship with the blue color of the fluorescent tint, and the original color of the recording medium so as not to expose the surface of the recording medium at the time of image formation as much as possible. Design the amount of white (W) ink, which is an ink that can reproduce colors close to. As shown in FIG. 8A, in the color separation table of the present embodiment, when the gradation of yellow changes from W (minimum gradation) to Y (maximum gradation), yellow ink 801 and white ink 802 The amount of ink in is designed as shown below. That is, the yellow gradation is designed to fill the ink amount of the yellow ink 801 with 100% (predetermined value) of a certain amount from the minimum gradation to the maximum gradation. Further, the ink amount of the white ink 802 is designed to be reduced from 100% (maximum value) at the minimum gradation to 0% (minimum value) at the maximum gradation according to the magnitude of the gradation. By creating the color separation table in this way, the total amount of yellow ink and white ink is 100% or more at any grid point of the YY line, and the surface of the recording medium is covered with ink at the time of image formation. It will be. As a result, since the surface of the recording medium is not exposed, it is possible to suppress the reduction of the color reproduction range due to the influence of fluorescence generated from the recording medium when irradiated with a light source containing ultraviolet light. Therefore, in the present embodiment, it is possible to suppress the decrease in saturation caused by the use of the conventional color separation table. In this way, since the yellow gradation is adjusted by the amount of white ink, the white ink is an ink that adjusts the yellow gradation, which is a color that absorbs the fluorescent color, and is used as a recording medium. It can be said that it is an ink that can reproduce a color close to the color.

In S704, the color separation table creating unit 115 designs a color separation table for intercolor lines in which the color reproduction range becomes large due to the influence of fluorescence generated from the recording medium when irradiated with a light source including ultraviolet light. The intercolor line to be designed in S704 is the intercolor line WC, MR, M-, in which the color reproduction range is determined to be large due to the influence of fluorescence in the color reproduction range change determination process in S305. B and BC. In each intercolor line, the grid point data (color separation data) of the grid points on each line is obtained as follows by the same method as in S703, and a color separation table for these grid points is created. More specifically, for example, in the line connecting the vertices W and the vertices C, the color measurement values of the patches are obtained for the vertices W and the vertices C as follows. That is, (C, M, Y, K, W) = (0, 0, 0, 0, 255) corresponding to the vertex W set in S702, and (C, M, Y, corresponding to the vertex C). The color measurement values of the printed patches are obtained based on the set of values of K, W) = (255, 0, 0, 0, 0). Then, the grid points are defined so as to be evenly distributed on the line connecting the above two color measurement values on the uniform color space. The values of the data (C, M, Y, K, W) that output the patch of the color measurement values of these evenly distributed grid points and the patch of the color measurement values closest to each are obtained as the grid point data of each grid point.

For the intercolor line to be designed in S704, the value of the data of each color ink is determined so as to make the best use of the influence of the fluorescence generated from the recording medium by being irradiated with the light source including ultraviolet light. Here, the amount of white (W) ink is designed so that the surface of the recording medium is exposed as much as possible during image formation.

The color separation table of the WC line will be described with reference to the drawings. FIG. 9 is a diagram showing an example of a color separation table of the WC line according to the present embodiment. In the color separation table of the present embodiment, when the gradation of cyan changes from W (minimum gradation) to C (maximum gradation), the ink amounts of cyan ink 901 and white ink 902 are designed as shown below. Will be done. That is, in the range where the gradation of cyan is from the minimum gradation to the maximum gradation, the amount of ink of cyan ink 901 is increased from 0% (minimum value) at the minimum gradation according to the magnitude of the gradation, and the maximum scale is used. It is designed to be 100% (maximum value) in key. On the other hand, the ink amount of the white ink 902 is set to 100% (maximum value) at the minimum gradation, and is rapidly reduced according to the magnitude of the gradation, from a predetermined gradation (predetermined grid point) to the maximum gradation. It is designed to be 0% (minimum value). By creating the color separation table in this way, in the WC line, the closer the cyan gradation is to the maximum gradation, the smaller the amount of white ink is, and the surface of the recording medium is covered at the time of image formation. The area will be reduced. As a result, since the surface of the recording medium is exposed, the color reproduction range of the patch having a bluish color becomes larger due to the influence of the fluorescence generated from the recording medium when irradiated with a light source including ultraviolet light.

In S705, the color separation table creation unit 115 creates a color separation table for other lines. The intercolor line to be designed in S705 is the intercolor line WM, KG, K in which the color reproduction range is determined not to change due to the influence of fluorescence in the color reproduction range change determination process in S305. -B, GC. The color separation table of each intercolor line created in S705 is not particularly limited in design, and can be any color separation table so that a desired color can be reproduced.

As described above, in S703 to S705, a color separation table corresponding to each intercolor line is designed according to the difference in the influence of fluorescence generated from the recording medium by being irradiated with a light source including ultraviolet light. Focusing on white ink, the following color separation table will be designed. In the color separation table, the amount of white ink used is larger for colors whose color reproduction range is smaller due to the influence of fluorescence, and the amount of white ink is used less for colors whose color reproduction range is larger or does not change. It will be designed.

In S706, the color separation table creating unit 115 performs internal interpolation processing based on the grid point data of the grid points on each line created in S703 to S705, and obtains the grid point data for the grid points other than the above line.

Finally, in S707, the color separation table creation unit 115 performs smoothing processing on the grid point data obtained as described above. In this smoothing process, 3 × 3 × 3 low-pass filters for each of the R, G, and B axis directions are sequentially obtained in S706 while changing the grid points so that the change in the amount of ink in the color separation table becomes smooth. Filtering is performed on the grid point data.

This completes the process of creating the color separation table.

<Recording order control mask>
The recording order control mask will be described with reference to the drawings. First, a method of applying the recording order control mask will be described, and then the recording order control mask will be described. FIG. 10 is a diagram showing an application example of the recording order control mask to the binary data generated by the halftone processing unit 117 for each recording scan. The recording order control mask according to the present embodiment is realized by a so-called path mask. Here, the path mask for controlling the order of recording on the recording medium using each color ink is particularly referred to as a recording order control mask.

As shown in FIG. 10, the recording order control mask is moved for the binary data by the recording width of each pass, that is, the length of the nozzle row of the recording head divided by the number of passes. Scan data is generated by performing dot thinning processing using. The scanning data are complementary to each other, and when the patterns of all the nozzle groups are superimposed, the recording pattern of the entire area is obtained. As for a general path mask, the path mask is designed so that the recording rate of each recording scan is not biased as much as possible. That is, in order to suppress deterioration of image quality such as sujimura, the recording rate is made uniform with respect to the number of recording scans. Alternatively, in order to suppress the dot position shift at the end of the recording head, a gradation shape is performed in which the recording rate on the preceding pass and the succeeding pass side is slightly lowered. On the other hand, the recording order control mask generated in the present embodiment corresponds to each color ink in order to control the recording order of the color inks, especially when the printing control of the color region where the color reproduction range becomes small due to the influence of fluorescence is performed. The path mask to be used biases the recording order of each recording scan.

Subsequently, the recording order control mask will be described with reference to the drawings. FIG. 11 is a diagram showing an example of a recording order control mask applied to a color region in which the color reproduction range becomes small due to the influence of fluorescence generated from a recording medium when irradiated with a light source containing ultraviolet light. As shown in FIG. 11, the recording order control mask 1101 for yellow ink has a recording rate of 50% for each of the first pass and the second pass, so that the total is 100% with the first pass. It is designed to complement each other with the second pass. Further, the recording order control mask 1101 for yellow ink is designed so that the recording rate is 0% in both the third pass and the fourth pass and recording is not performed.

Further, the recording order control mask 1102 for white ink has a recording rate of 50% for each of the 3rd pass and the 4th pass, so that the total is 100% for the 3rd pass and the 4th pass. Designed to complement each other. Further, the recording order control mask 1102 for white ink is designed so that the recording rate is 0% in both the first pass and the second pass and recording is not performed.

By designing the recording order control mask for each color ink in this way, yellow ink is formed on the preceding pass side (1st pass and 2nd pass), and white ink is formed on the succeeding pass side. .. By using the recording order control mask designed in this way, it is possible to control the recording order of the ink so that the yellow ink is formed on the lower layer side and the white ink is formed on the upper layer side. By designing the recording order control mask in combination with the design of the color separation table described above, even if the influence of fluorescence generated from the recording medium by irradiation with a light source including ultraviolet light occurs, the influence of fluorescence It is possible to maintain the color reproduction range when there is no such thing.

It should be noted that the recording order control mask may not be such that the recording rate is extremely divided into the preceding path and the succeeding path as described above. The recording order control mask may be such that the recording rate is continuously biased within 4 passes so that the yellow ink is generally recorded on the preceding pass side as compared with the white ink.

On the other hand, for the color region where the color reproduction range becomes large due to the influence of fluorescence, the surface of the recording medium is controlled to be exposed by designing a predetermined amount of ink in the design of the color separation table described above. Therefore, there is no particular need to control the recording order for each color ink. Therefore, for example, each recording scan data is created by using an arbitrary pass mask 1103, such as a pass mask having a constant recording rate for each pass. Similarly, for a color region in which the color reproduction range does not change due to the influence of fluorescence, it is not necessary to control the recording order for each color ink, so each recording scan data is created using an arbitrary path mask.

<Image structure of printed matter>
The image structure of the printed matter will be described. A printed matter in which an image is formed with gradations of intercolor lines in which the color reproduction range is smaller than that under a light source containing ultraviolet light will be described with reference to the figure. FIG. 12 schematically shows a cross section of a printed matter in which an image is formed with gradations of intercolor lines in which the color reproduction range becomes smaller due to the influence of fluorescence generated from a recording medium when irradiated with a light source containing ultraviolet light. It is a figure. FIG. 12 shows eight gradations from i = 1 to i = 8 for the intercolor line YY.

As shown in FIG. 12, the printed matter is one in which ink is recorded on a recording medium having an ink receiving layer 1201 containing a fluorescent whitening agent and a base paper layer 1202 supporting the ink receiving layer 1201. As the numerical value of i increases, the gradation approaches Y, and when i reaches the maximum value of 8, the gradation becomes Y. The following dots are formed on the surface 1203 of the ink receiving layer 1201. Are formed based on the desired amount of ink and the order of recording, respectively. The dots formed on the surface 1203 of the ink receiving layer 1201 include yellow dots 1204 formed by ejecting yellow ink and white dots 1205 formed by ejecting white ink.

As can be seen from the dot formation positions at each gradation from i = 1 to i = 8, the yellow dots 1204 cover the entire surface of the ink receiving layer 1201 at any gradation, and the white dots 1205 It is formed in a layer on the lower layer side. As a result, the surface of the recording medium is covered with the yellow dots of the ink, which is a color that has a complementary color relationship with the fluorescent color and is a color that can absorb the fluorescent color, so that fluorescence from the recording medium is generated on the paper surface. Is suppressed. Then, on the upper layer side, white dots 1205 of ink having a color that can reproduce a color close to the color of the recording medium are discretely formed so as to be a desired color of gradation, and the color on the paper surface is formed. Is matched.

As described above, the number of occurrences of each dot of yellow dots and white dots is determined by the color separation table, and the recording order of each of yellow dots and white dots is determined by the recording order control mask. By designing each with consideration for both the color separation table and the recording order control mask, the layered image structure as described above can be created.

In this way, for the color region where the color reproduction range becomes small due to the influence of fluorescence, a color separation table and a recording order control mask are created and used so that the surface of the recording medium that generates fluorescence is not exposed. To form a color image. At this time, by using white ink of the same color as the recording medium, it is possible to match the colors at the intercolor line while reducing the influence of the fluorescent whitening agent. As the white ink, for example, an ink that does not contain a fluorescent whitening agent and has little color change due to the influence of fluorescence is used.

As a result, since the surface of the recording medium is not exposed, a blue fluorescent color is generated, the color tint is not canceled out with the yellow ink, and the saturation is not lowered, and the color reproduction range due to the influence of fluorescence is not reached. Shrinkage can be suppressed.

Further, an image structure is formed in which the entire surface of the recording medium is covered with white ink so as to eliminate the influence of the color of fluorescence generated from the recording medium by being irradiated with a light source including ultraviolet light as much as possible. Therefore, even if the amount of ultraviolet light contained in the observation light source or the amount of fluorescent whitening agent added to the recording medium differs depending on the recording medium, it is necessary to change the color separation table and the recording order control mask each time. It is possible to suppress the reduction of the color reproduction range of the color image formed on the printed matter.

On the other hand, a printed matter in which an image is formed with gradations of intercolor lines having a larger color reproduction range under a light source containing ultraviolet light than under a light source not containing ultraviolet light will be described with reference to the drawings. FIG. 13 schematically shows a cross section of a printed matter in which an image is formed with gradations of intercolor lines in which the color reproduction range becomes large due to the influence of fluorescence generated from a recording medium when irradiated with a light source including ultraviolet light. It is a figure. FIG. 13 shows eight gradations from i = 1 to i = 8 for the intercolor line WC.

As shown in FIG. 13, the printed matter is one in which ink is recorded on a recording medium having an ink receiving layer 1201 containing a fluorescent whitening agent and a base paper layer 1202 supporting the ink receiving layer 1201. As the numerical value of i increases, the gradation approaches C, and when i reaches the maximum value of 8, the gradation becomes C. The following dots are formed on the surface 1203 of the ink receiving layer 1201. Are formed based on the desired amount of ink and the order of recording, respectively. The dots formed on the surface 1203 of the ink receiving layer 1201 include cyan dots 1301 formed by ejection of cyan ink and white dots 1205 formed by ejection of white ink.

The number of cyandot 1301 shots increases as it approaches C. At this time, the cyandots 1301 are arranged discretely, and the white dots 1205 are formed so that the surface of the recording medium is exposed as much as possible.

In this way, image processing and image formation are performed so as to utilize the expansion of the color reproduction range by fluorescence in the color region where the color reproduction range becomes large due to the influence of fluorescence. That is, the corresponding color region is determined, and in the determined color region, a color separation table and a recording order control mask are created so that the surface of the recording medium is exposed as much as possible, and the colors are used on the recording medium by using them. Form an image. As a result, it is possible to increase the color reproduction range of the color image formed on the printed matter in the color in which the color reproduction range becomes large due to the influence of fluorescence.

As described above, in the present embodiment, color change information due to the influence of fluorescence generated from the recording medium when the printed matter formed on the recording medium containing the fluorescent whitening agent is irradiated with a light source containing ultraviolet light is acquired. do. Then, the change in the color reproduction range is determined based on the color change information, a color separation table and a recording order control mask are created according to the determination result, and an image is formed using them. As a result, the coverage of the surface of the recording medium containing the fluorescent whitening agent is controlled for each color. In particular, in a color whose color reproduction range is reduced due to the influence of fluorescence, even if the amount of ultraviolet light contained in the observation light source and the amount of the fluorescent whitening agent added to the recording medium are different, the color image formed on the printed matter is formed. It is possible to suppress the reduction of the color reproduction range. Further, in a color in which the color reproduction range is increased due to the influence of fluorescence, the color reproduction range of the color image formed on the printed matter can be increased.

[Second Embodiment]
Subsequently, an embodiment using a color separation table for shade inks of colors having a complementary color relationship with the fluorescent color will be described as a second embodiment. On the premise that the color of the fluorescence generated from the recording medium when irradiated with a light source containing ultraviolet light is the same blue as in the first embodiment, the color of yellow, which is a complementary color to the blue, is used. An example of using two types of light and dark inks, a dark yellow ink and a light and light ink, will be described. Hereinafter, the contents common to the first embodiment will be omitted, and the color separation table of the light and shade ink, which is different from the first embodiment, will be mainly described.

<Printer configuration>
The configuration of the printer according to the present embodiment, which is added to the printer of the first embodiment due to the use of the light and shade ink, will be described. In addition to the cyan (C), magenta (M), yellow (Y), and black (K) color inks, light yellow (LY) color inks are added to the ink tank of the printer 13 of the present embodiment. An ink tank containing each of the five types of ink is independently provided. The light yellow ink is an ink having a lower ink density than the yellow ink. The light yellow ink is, for example, an ink in which the pigment concentration is relatively diluted to 1/2. In the following description, normal yellow ink will be referred to as dark yellow ink.

<Logical configuration of image processing device>
Further, the image processing device 1 according to the present embodiment has the same logical configuration as the image processing device of the first embodiment. In the present embodiment, the light yellow data added in the color matching processing unit 112, the color separation table creation unit 115, the color separation processing unit 116, the halftone processing unit 117, the mask creation unit 118, and the print control unit 119 are also obtained. Each process is applied.

<Process for creating a color separation table>
The process of creating the color separation table by the color separation table creation unit 115 according to the present embodiment will be described. As described with reference to FIG. 6 in the first embodiment, yellow (Y) exists in an intercolor line under a light source containing ultraviolet light and having a smaller color reproduction range than under a light source not containing ultraviolet light. do. Therefore, in the present embodiment, in the process of S703 of FIG. 7, in the process of designing the color separation table of the intercolor line, which is determined to reduce the color reproduction range due to the influence of fluorescence, the following color separation table is used. design. That is, design a color separation table corresponding to light and shade yellow ink, which is a color ink that absorbs the fluorescent color, so that the influence of fluorescence generated from the recording medium when irradiated with a light source containing ultraviolet light is minimized. .. Hereinafter, among the color separation tables designed for the light and shade yellow ink, the color separation table of the YY line will be described as an example.

The color separation table applied to the YY line will be described with reference to the drawings. FIG. 14 is a diagram showing an example of a color separation table of a YY line, and FIG. 14A shows a case where the design is made for both dark yellow ink and light yellow ink, and FIG. 14B shows a case where the design is made. ) Shows the case where it is designed only for dark yellow ink.

As shown in FIG. 14B, only the dark yellow ink 1402 is used in the example of the color separation table of the YY line. The amount of ink in the dark yellow ink 1402 is 100% when the yellow gradation is Y (maximum gradation), decreases from Y to W (minimum gradation), and becomes 0% at W. ing. In this case, the closer to W, the less the surface of the recording medium is exposed, so that more blue-based fluorescent colors are generated, and the tint of the yellow ink is canceled by the fluorescent colors to become white. That is, the saturation of the color visually recognized by the observer is reduced.

Therefore, in the present embodiment, the data value of each color ink is determined so as to cover the surface of the recording medium with light yellow ink or dark yellow ink from the gradation in which yellow is as small as possible on the YY line. Therefore, as shown in FIG. 14A, in the color separation table of the present embodiment, when the yellow gradation changes from W (minimum gradation) to Y (maximum gradation), the light yellow ink 1401 and The amount of ink in the dark yellow ink 1402 is designed as shown below. That is, in the intermediate gradation from the minimum gradation to the predetermined gradation of yellow, the ink amount of the light yellow ink 1401 increases from 0% (minimum value) at the minimum gradation according to the magnitude of the gradation and is intermediate. It is designed to be 100% (maximum value) in gradation. Further, the ink amount of the dark yellow ink 1402 is designed to be 0% (minimum value) in the intermediate gradation from the minimum gradation to the predetermined gradation of yellow. When the gradation of yellow is from the middle gradation to the maximum gradation, the amount of ink of the light yellow ink 1401 decreases according to the magnitude of the gradation and becomes 0% (minimum value) at the maximum gradation, while the dark yellow ink. It is designed so that the amount of ink of 1402 increases and becomes 100% (maximum value) at the maximum gradation. Here, by using a large amount of light yellow ink 1401 that requires a larger amount of ink to produce the same color, the amount of the surface of the recording medium covered during image formation is increased. At this time, the ink amount of the light yellow ink 1401 does not necessarily have to be 100%, and the ink amount may be as shown below. That is, the amount of ink that can sufficiently cover the surface of the recording medium with only the light yellow ink 1401 or the amount of ink that can cancel the fluorescence generated from the recording medium by being irradiated with a light source containing ultraviolet light may be used. For the dark yellow ink 1402, as described above, a color separation table in which the dark yellow ink 1402 is increased so as to replace the light yellow ink 1401 is designed. By designing the color separation table using more light yellow ink 1401 in this way, the surface of the recording medium is more covered at the time of image formation. As a result, the surface of the recording medium is not exposed as much as possible, so that the color reproduction range is suppressed from being reduced due to the influence of fluorescence generated from the recording medium when irradiated with a light source containing ultraviolet light. Therefore, in the present embodiment, by using the color separation table of FIG. 14 (a), the decrease in color saturation visually recognized by the observer caused by using the color separation table of FIG. 14 (b) is suppressed. be able to.

In the present embodiment, the smaller the dilution ratio of the pigment concentration of the light yellow ink, the more the surface of the recording medium can be covered with the same amount of ink, and the recording medium can be covered with the same amount of ink, especially in the gradation on the highlight side. There is an advantage that the influence of the fluorescence generated from the ink can be suppressed. However, since the dilution rate of the pigment concentration of the light yellow ink, the effect of blocking the influence of fluorescence, and the consumption amount of the ink correlate with each other, the dilution rate of the pigment concentration of the light yellow ink is the above-mentioned effect and the consumption amount. Is determined in consideration of.

<Bivalent data by halftone processing>
The binary data obtained by the halftone processing according to the present embodiment will be described. When forming a color image using the YY line color separation table shown in FIG. 14, in order to cover the surface of the recording medium as much as possible, it is necessary to make the positional relationship of the dot patterns between the ink colors exclusive to each other. It is effective. In order to realize this, when the halftone processing unit 117 creates a dot pattern between ink colors, the dots of dark yellow ink and the dots of light yellow ink are mutually exclusive in a predetermined intercolor line. Apply halftone processing as in. The target predetermined intercolor line is an intercolor line that is determined in S703 to have a smaller color reproduction range due to the influence of fluorescence generated from a recording medium when irradiated with a light source containing ultraviolet light. Therefore, in the present embodiment, the dither matrix is designed so that the dots of the dark yellow ink and the dots of the light yellow ink have an exclusive relationship with each other. The dither matrix designed in this way is easily generated by using, for example, the inversion value of the dark yellow ink (the maximum value of the input range-the threshold value of the dark yellow ink) as the threshold value of the light yellow ink.

<Image structure of printed matter>
A printed matter in which an image is formed with gradations of intercolor lines in which the color reproduction range is smaller than that under a light source containing ultraviolet light will be described with reference to the figure. FIG. 15 schematically shows a cross section of a printed matter in which an image is formed with gradations of intercolor lines in which the color reproduction range becomes smaller due to the influence of fluorescence generated from a recording medium when irradiated with a light source containing ultraviolet light. It is a figure. FIG. 15 shows eight gradations from i = 1 to i = 8 for the intercolor line YY.

As shown in FIG. 15, the printed matter is one in which ink is recorded on a recording medium having an ink receiving layer 1201 containing a fluorescent whitening agent and a base paper layer 1202 supporting the ink receiving layer 1201. As the numerical value of i increases, it approaches the gradation of Y, and when i reaches the maximum value of 8, the gradation of Y (maximum gradation) is obtained on the surface 1203 of the ink receiving layer 1201. Each of the following dots is formed based on the desired amount of ink and recording order. The dots formed on the surface 1203 of the ink receiving layer 1201 include light yellow dots 1503 formed by ejection of light yellow ink and dark yellow dots 1504 formed by ejection of dark yellow ink. As described in the above halftone processing, in the YY line, which is an intercolor line in which the color reproduction range is determined to be reduced due to the influence of fluorescence, the dark yellow dots 1504 and the light yellow dots 1503 are mutually exclusive. You can see that. Although the cross section of the printed matter is shown in FIG. 15, the positions of the dark yellow dots and the light yellow dots are controlled for each gradation so as to be as exclusive as possible even on the two-dimensional plane of the printed matter.

By forming a color image so that the dark yellow dots 1504 and the light yellow dots 1503 are mutually exclusive, a fluorescent whitening agent is contained at the time of image formation, as in the case of using the white ink shown in the first embodiment. The exposure of the surface of the recording medium can be reduced. Therefore, a bluish fluorescent color is not generated, the hue is canceled out with the yellow ink, and the saturation is not lowered, and the reduction of the color reproduction range due to the influence of the fluorescence can be suppressed.

As described above, in the present embodiment, color change information due to the influence of fluorescence generated from the recording medium when the printed matter formed on the recording medium containing the fluorescent whitening agent is irradiated with a light source containing ultraviolet light is acquired. do. Then, the change in the color reproduction range is judged based on the color change information, and a color separation table and a recording order control mask corresponding to the light and shade ink having a color relationship opposite to the fluorescent color are created according to the judgment result. , Use them to form an image. As a result, the coverage of the surface of the recording medium containing the fluorescent whitening agent is controlled for each color. In particular, for colors whose color reproduction range is reduced by the influence of fluorescence generated from the recording medium, even if the amount of ultraviolet light contained in the observation light source and the amount of the fluorescent whitening agent added to the recording medium differ depending on the recording medium. It is possible to suppress the reduction of the color reproduction range of the printed matter. Further, as in the first embodiment, the color reproduction range of the printed matter can be increased in the color in which the color reproduction range is increased due to the influence of fluorescence.

[Other embodiments]
In addition to the embodiments shown in the first embodiment and the second embodiment, various modifications can be implemented.

As the ink mounted on the printer 13, white ink and light ink may be used at the same time. Further, the ink is not limited to the above-mentioned ink. For example, in a configuration including special color inks such as red (R) ink, green (G) ink, and blue (B) ink, and light cyan (LC), light magenta (LM), light yellow (LY), and clear ink. Any color of ink may be used as long as the following data can be designed. That is, a color separation table and halftone processing are performed so that the color of the fluorescence generated from the recording medium containing the fluorescent whitening agent is suppressed from being reduced in the color reproduction range by being irradiated with a light source containing ultraviolet light. Any color of ink may be used as long as the data and recording order control mask can be designed.

Further, as the type of ink, any ink can be used as long as it is an ink capable of forming a color image on a recording medium containing a fluorescent whitening agent. For example, various inks capable of forming an image, such as water-based dye inks, latex inks, and solvent-based inks, can be used.

Further, the recording medium may be a material other than paper made from pulp as long as it is a recording medium that generates fluorescence. Alternatively, there may be a case where fluorescence is generated from a substrate laid under the transparent recording medium. Alternatively, the fluorescent whitening agent may be contained in the special ink such as the precursor ink formed as the base of the color ink with respect to the recording medium. Further, a clear ink having similar spectral characteristics may be used instead of the light yellow ink.

Further, the printer 13 is not limited to the above-mentioned operation and recording method. For example, a full-line inkjet printer may be used in which a recording head having a length corresponding to the width of the recording medium is provided for each color ink, fixed to each color ink, and then the recording medium is passed through the paper only once. Alternatively, it can be applied to an electrophotographic method, a printer using an LED or a heating element, and the like.

Further, if the recording order of each color ink recorded on the recording medium can be controlled in order to suppress the reduction of the color reproduction range with respect to the color region for a specific color ink, it is not necessary to use the recording order control mask. For example, refer to the information consisting of a data file or a mathematical formula that specifies which path to assign to each pixel of the binary data generated by the halftone processing unit 117 before controlling the recording order, and set each path. Dots may be assigned. Alternatively, probabilistic arithmetic processing may be performed on each pixel so that the recording order is controlled, and which path each dot is formed may be determined. Alternatively, the multi-valued data before the halftone processing may be distributed to each path so that the recording order is controlled, and the halftone processing may be performed while considering the arrangement relationship with respect to the multi-valued data of each path. ..

Further, the color separation is not limited to the method using the color separation table, and may be a function conversion by a mathematical formula or the like.

The present disclosure supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

1 Image processing device 116 Color separation processing unit 119 Print control unit

Claims (19)

An image processing device that performs processing for forming a color image on a recording medium containing a fluorescent whitening agent.
A color separation means that performs color separation to convert the color space of the input image data into a color space corresponding to multiple recording materials, and
It has a control means for controlling recording by the plurality of recording materials used when forming the color image based on the image data after color separation.
The control means obtains a test pattern recorded on a recording medium containing a fluorescent whitening agent by measuring it when it is irradiated with a light source containing ultraviolet light and when it is irradiated with a light source not containing ultraviolet light. Based on the color measurement data obtained from the color information, the recording is controlled so as to suppress the reduction of the color reproduction range for the color region corresponding to the specific recording material among the plurality of recording materials. Image processing device. Further having a creating means for creating a recording order control mask for controlling the recording by a plurality of recording materials used when forming the color image.
The image processing apparatus according to claim 1, wherein the control means controls the recording based on the recording order control mask and the image data after color separation. The image according to claim 2, wherein the creating means creates the recording order control mask so as not to expose the surface of the recording medium as much as possible in the color region corresponding to the specific recording material. Processing equipment. The color region corresponding to the specific recording material is a color region in which the color reproduction range becomes small.
The producing means records a color that absorbs a fluorescent color generated from the recording medium by being irradiated by a light source containing ultraviolet light among the plurality of recording materials in a color region where the color reproduction range becomes small. The material is formed in a layer on the recording medium, and further, among the plurality of recording materials, a recording material for adjusting the gradation of a color that absorbs the fluorescent color is discretely formed. The image processing apparatus according to claim 2 or 3, wherein the recording order control mask is created. The color region corresponding to the specific recording material is a color region in which the color reproduction range becomes small.
The producing means records a color that absorbs a fluorescent color generated from the recording medium by being irradiated by a light source containing ultraviolet light among the plurality of recording materials in a color region where the color reproduction range becomes small. The recording order control mask for increasing the coverage of the surface of the recording medium with the material, and the recording order corresponding to each of the dark ink and the light ink, which are the color recording materials that absorb the fluorescent color. The image processing apparatus according to claim 2 or 3, wherein the control mask is created. Claims 1 to 5 are characterized in that the color separation table used by the color separation means is created so as not to expose the surface of the recording medium as much as possible in the color region corresponding to the specific recording material. The image processing apparatus according to any one of the above. The color region corresponding to the specific recording material is a color region in which the color reproduction range becomes small.
The color separation table is used in the color region where the color reproduction range is small.
Of the plurality of recording materials, the amount of the color recording material that absorbs the fluorescent color generated from the recording medium by being irradiated by the light source containing the ultraviolet light is the gradation of the color that absorbs the fluorescent color. Is a predetermined value from the minimum gradation to the maximum gradation, while
Of the plurality of recording materials, the amount of the recording material for adjusting the gradation of the color that absorbs the fluorescent color is the maximum value at the minimum gradation of the gradation of the color that absorbs the fluorescent color. The image processing apparatus according to claim 6, wherein the image processing apparatus is created so as to decrease according to the size of the key and to be the minimum value at the maximum gradation. The color region corresponding to the specific recording material is a color region in which the color reproduction range becomes small.
The color separation table is a dark ink and a color recording material that absorbs the fluorescent color generated from the recording medium by being irradiated by a light source containing ultraviolet light in the color region where the color reproduction range is small. Corresponds to each of the light inks,
The amount of the light ink increases according to the magnitude of the gradation from the minimum gradation to the intermediate gradation of the color that absorbs the fluorescent color, and reaches the maximum value in the intermediate gradation. From the gradation to the maximum gradation, it decreases according to the magnitude of the gradation and becomes the minimum value at the maximum gradation.
The amount of ink of the dark ink is the minimum value from the minimum gradation to the intermediate gradation of the color that absorbs the fluorescent color, and the magnitude of the gradation is from the intermediate gradation to the maximum gradation. The image processing apparatus according to claim 6, wherein the image processing apparatus is created so as to increase in accordance with the above and to reach the maximum value at the maximum gradation. Claim 4, claim 5, claim 7, or claim 7, wherein the color recording material that absorbs the fluorescent color is a recording material that can reproduce a color that has a complementary color relationship with the fluorescent color. The image processing apparatus according to any one of claims 8. The image according to any one of claims 4, 5, 7, 8, and 9, wherein the color recording material that absorbs the fluorescent color is yellow ink. Processing equipment. The image according to claim 4 or 7, wherein the recording material for adjusting the gradation of the color that absorbs the fluorescent color is a recording material capable of reproducing a color close to the color of the recording medium. Processing equipment. The image processing apparatus according to claim 4, wherein the recording material for adjusting the gradation of the color that absorbs the fluorescent color is white ink. The second aspect of the present invention is characterized in that the creating means creates the recording order control mask that expands the color reproduction range with respect to a color region corresponding to another specific recording material among the plurality of recording materials. The image processing device described. The color region corresponding to the other specific recording material is a color region in which the color reproduction range becomes large.
The image processing apparatus according to claim 13, wherein the image processing means creates the recording order control mask so as to expose the surface of the recording medium as much as possible in the color region where the color reproduction range becomes large. .. The color region corresponding to the other specific recording material is a color region in which the color reproduction range becomes large.
The color separation table used by the color separation means is used in the color region where the color reproduction range becomes large.
Of the plurality of recording materials, the amount of the color recording material to be reproduced on the surface of the recording medium becomes the minimum value at the minimum gradation of the color to be reproduced, and increases according to the magnitude of the gradation. And while the maximum gradation is the maximum value,
Of the plurality of recording materials, the amount of the recording material capable of reproducing a color close to the color of the recording medium has the maximum value at the minimum gradation of the color to be reproduced, depending on the magnitude of the gradation. The image processing apparatus according to claim 13, wherein the image processing apparatus is created so as to decrease and become a minimum value at a predetermined gradation. The image processing apparatus according to claim 15, wherein the color recording material to be reproduced on the surface of the recording medium is cyan ink. The image processing apparatus according to claim 15, wherein the recording material capable of reproducing a color close to the color of the recording medium is white ink. A program for causing a computer to function as each means of the image processing apparatus according to any one of claims 1 to 17. An image processing method for forming a color image on a recording medium containing a fluorescent whitening agent.
A color separation step that converts the color space of the input image data into a color space corresponding to multiple recording materials, and a color separation step.
A control step for controlling recording by the plurality of recording materials used when forming the color image based on the image data after color separation is included.
In the control step, the test pattern recorded on the recording medium containing the fluorescent whitening agent is measured and obtained when it is irradiated with a light source containing ultraviolet light and when it is irradiated with a light source not containing ultraviolet light. Based on the color measurement data obtained from the color information, the recording is controlled so as to suppress the reduction of the color reproduction range for the color region corresponding to the specific recording material among the plurality of recording materials. Characteristic image processing method.

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