JP2016179595A - Printing device, printing method and printing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing device and the like which perform reciprocation printing and can reduce the color difference between the forward printing and the return printing regardless of a printing condition such as a sheet type.SOLUTION: A printing device comprises: a printing part which performs bidirectional printing on a printing medium; and an adjustment part which causes the printing part to print a first direction printing image using first direction color conversion information for a first type printing medium and a second direction printing image using second direction color conversion information for a second type printing medium on the second type printing medium in a comparable manner. The second direction color conversion information for the second type printing medium is generated by adjusting the second direction color conversion information for the first type printing medium.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printing apparatus that performs reciprocal printing, and more particularly to a printing apparatus that can reduce a color difference between forward printing and backward printing regardless of printing conditions such as paper type.

  2. Description of the Related Art Conventionally, there are printers that perform printing by synchronizing the operation of a print head in the main scanning direction and the paper feeding operation in the sub scanning direction. In such a printer, it is known that reciprocal printing (bidirectional printing) is performed in which printing is performed in both the forward path and the backward path of the print head in order to improve the printing speed. This reciprocal printing is also widely used in color ink jet printers, but there is a problem in that the order of ink overlap in the forward path and the return path differs depending on the arrangement of the nozzle rows of each color, resulting in a color difference between the forward path and the return path. It was.

  In order to solve this problem, the following Patent Document 1 proposes a technique for eliminating color unevenness due to a difference in the order of colorant overlap in reciprocal printing. This document includes a color processing look-up table (LUT) for an outward path. For example, processing using two LUTs of a color processing look-up table (LUT) for the return path is described.

  Patent Document 2 listed below describes a technique for highly accurately matching the color tone of an image recorded during the forward movement and the color tone of an image recorded during the backward movement. In other words, it is described that the return image is formed so as to be comparable with the forward image.

JP 2007-136845 A JP 2004-34435 A

  However, even if the color difference between forward printing and backward printing is adjusted to the minimum according to the background art described above, the color difference becomes large if the printing conditions such as the type of paper (paper type) as the printing medium are changed. There is a problem that it ends up. Regarding the problem, Patent Documents 1 and 2 do not show a solution.

  Furthermore, it is desired that the user can easily adjust the color conversion processing according to the printing conditions such as the paper type.

  Accordingly, an object of the present invention is to provide a printing apparatus that performs reciprocal printing, and that can reduce a color difference between forward printing and backward printing regardless of printing conditions such as paper type. is there.

  In order to achieve the above object, one aspect of the present invention provides a first direction print image using a printing unit that performs bidirectional printing on a print medium and first direction color conversion information for the first type print medium. A second direction print image using the second direction color conversion information for the second type print medium, and an adjustment unit that prints the second type print medium in a manner comparable to the second type print medium. The second direction color conversion information for the second type print medium is generated by adjusting the second direction color conversion information for the first type print medium.

  Furthermore, in the above invention, a preferred aspect is characterized in that the first direction print image and the second direction print image are images filled with a predetermined color.

  Furthermore, in the above-described invention, a preferable aspect thereof is characterized in that the adjustment unit causes the first direction print image and the second direction print image to be printed adjacent to each other.

  Further, in the above invention, according to one preferable aspect, the adjustment unit adjusts the second direction color conversion information for the second type print medium based on a predetermined coefficient, and sets each of the plurality of values of the predetermined coefficient. Printing a plurality of second direction print images using a plurality of second direction color conversion information for the second type print medium adjusted based on the first direction print image, respectively. It is characterized by.

  Furthermore, in the above invention, a preferable aspect is that the adjustment unit acquires identification information of one second direction print image input corresponding to printing of the plurality of second direction print images, and acquires the information. The value of the predetermined coefficient corresponding to the second direction print image identified by the identified identification information is stored.

  Furthermore, in the above invention, a preferable aspect is that the printing unit performs printing based on the image data converted using the first direction color conversion information for the first type print medium during the first direction printing, At the time of second direction printing, printing is performed based on image data converted using the second direction color conversion information for the second type print medium adjusted based on the stored value of the predetermined coefficient. It is characterized by that.

  In order to achieve the above object, another aspect of the present invention is to print a first direction print image using the first direction color conversion information for the first type print medium, and for the first type print medium. The second direction color conversion information for the second type print medium adjusted with the second direction color conversion information is generated, and the second direction print image using the second direction color conversion information for the second type print medium is generated. The printing method is characterized in that printing is performed so as to be comparable with the first direction print image.

  In order to achieve the above object, according to another aspect of the present invention, there is provided a printing system including a host apparatus and a printing apparatus. A printing unit that performs directional printing, a first direction print image that uses the first direction color conversion information for the first type print medium, and a second direction that uses the second direction color conversion information for the second type print medium An adjustment unit that prints the print image on the second type print medium so that the print unit can be compared with the second type print medium, and the host device uses the first direction color conversion information for the first type print medium. The second direction using the second direction color conversion information for the second type print medium generated by generating the image data in one direction and adjusted using a value of a predetermined coefficient determined based on printing by the adjustment unit A driver unit for generating the image data of Second direction color conversion information for the serial second type print medium, wherein is has been generated adjust the second direction color conversion information for the first type print media, is that.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

1 is a configuration diagram according to an embodiment of a printing system including a printing apparatus to which the present invention is applied. It is the figure which expressed the color conversion table in three dimensions. 5 is a diagram showing an example of an α table 127. FIG. 5 is a diagram illustrating a configuration of a carriage 224. FIG. FIG. 10 is a diagram for explaining an operation of a carriage 224 with respect to a print medium (paper) 229. It is a flowchart which shows an example of the determination process of coefficient (alpha). It is the figure which illustrated the printed patch image. 5 is a flowchart illustrating an example of a processing procedure in the printing system 100. It is the flowchart which illustrated the procedure of the color conversion process.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a configuration diagram according to an embodiment of a printing system including a printing apparatus to which the present invention is applied. A printer 2 shown in FIG. 1 is a printing apparatus to which the present invention is applied. The printer 2 is a printer that performs reciprocal printing (bidirectional printing). In forward printing, image data that has been subjected to color conversion processing using a forward color conversion table (outward LUT 125, first direction color conversion information) is used. Based on the color conversion table (return path LUT) adjusted according to the type of paper (paper type) that is the printing medium to be used in the return path printing, the image data is subjected to color conversion processing. Print based on Further, the printer 2 determines each of the forward print image (first direction print image) and the coefficient α in order to determine a coefficient α (predetermined coefficient) for adjusting the color conversion table for the return path according to the paper type. In order to adjust the value α of the return pass image selected by the user in the color conversion table for the return pass by printing out each return pass print image (second direction print image) adjusted according to the value. Is determined as the value of the coefficient α. By the processing of the printer 2, the color difference between the forward printing and the backward printing can be suppressed to be small for each paper type, and the preparation work for that can be easily performed.

  As shown in FIG. 1, a printing system 100 according to this embodiment includes a host computer 1 and a printer 2 that is a color ink jet printer that performs reciprocal printing.

  The host computer 1 is a host device of the printer 2 that gives a print instruction to the printer 2, and is configured by a personal computer, for example. Therefore, although not shown, the host computer 1 includes a CPU, RAM, ROM, HDD, display (display device), operation device (instruction device), and the like.

  As shown in FIG. 1, the host computer 1 includes an application unit 11 and a printer driver unit 12 as functional configurations.

  The application unit 11 is a print request source for the printer 2. When printing is requested, image data to be printed (hereinafter referred to as original image data) with respect to the printer driver unit 12 by a user's instruction operation on the host computer 1 or the like. Send. The original image data is data in a standard format (for example, a format conforming to GDI (Graphical Data Interface)) in which print targets such as characters and graphics are expressed in object units. Also, in the original image data, the color of the image is expressed by RGB (red, green, blue) multivalue (for example, 256 gradations from 0 to 255) as an example. Note that the application unit 11 includes a program describing processing contents, a CPU that executes processing according to the program, a RAM, and the like.

  The printer driver unit 12 is a part responsible for the driver function for the printer 2, performs various processes on the original image data output from the application unit 11, generates print data for the printer 2, and outputs the print data. Send to printer 2. The printer driver unit 12 includes a driver program describing processing contents, a CPU that executes processing according to the program, various data used for processing, a memory that stores the driver program and various data, and the like.

  As shown in FIG. 1, the printer driver unit (control unit) 12 includes a rendering unit 121, a color conversion unit 122, a halftone processing unit 123, a command generation unit 124, a forward path LUT 125, a backward path LUT 126, and the functional configuration. , An adjustment table (α table) 127 is provided.

  The rendering unit 121 is a part that performs rendering processing on the original image data output from the application unit 11, and converts the original image data into image data in pixel units. That is, the rendering unit 121 converts the original image data into image data in which each pixel has RGB multi-values (for example, 256 gradations of 0 to 255). The pixel unit image data is hereinafter referred to as RGB pixel data.

  The color conversion unit 122 converts the RGB pixel data generated by the rendering unit 121 into color data (in this example, CMYK (cyan, magenta, yellow, black)) used in the printer 2. Hereinafter, this is a part for executing a process (color conversion process) for conversion into CMYK pixel data). The CMYK pixel data is ink amount data in which each pixel has CMYK multivalue (for example, 256 gradations of 0 to 255). Therefore, the CMYK pixel data is data representing the ink amount of each ink in the printer 2.

  As described above, the color conversion unit 122 performs adjustment according to the printing conditions such as the type of paper (paper type) that is the printing medium used in the printer 2 in the color conversion processing for the backward printing of the printer 2, This processing is characteristic of the printing system. Specific contents of the color conversion process including the adjustment process will be described later.

  The halftone processing unit 123 is a part that executes halftone processing for converting image data in units of pixels into image data expressed by the presence or absence of printing dots. In the present embodiment, the halftone processing unit 123 converts CMYK pixel data into data expressed by the presence or absence of each CMYK print dot (hereinafter referred to as dot data). The print dots are dots formed on the print medium (paper) by ejecting ink from the printer 2. For example, a plurality of dots having large, medium, and small sizes are used. In this case, the dot data includes information representing the presence / absence of a large dot, the presence / absence of a medium dot, and the presence / absence of a small dot for each color for each position of the print medium on which ink is ejected.

  The command generation unit 124 is a part that expresses a print request including image data to be printed with a command for the printer 2. The print request generated by the command generation unit 124 is transmitted from the host computer 1 to the printer 2 as print data. When the command generation unit 124 generates a print request (print data), the dot data is represented by a command for the printer 2 and included in the print data.

  The forward path LUT (first LUT, first color conversion information) 125 and the backward path LUT (second LUT, second color conversion information) 126 are respectively a color conversion table for forward printing in the printer 2 and It is a color conversion table (color conversion information) for return pass printing. The color conversion table is a table storing data for converting the color representation of the image data output from the application unit 11 into the color representation of the ink color used in the printer 2, that is, by the color conversion unit 122. It is a table for color conversion processing. In this embodiment, the color representation in the RGB color space is converted to the color representation in the CMYK color space.

  The color conversion table expresses (R, G, B) which is the color value of three-dimensional data expressed by 8 bits (256 gradations) of each color of RGB by 8 bits (256 gradations) of each color of CMYK. Information to be assigned to (C, M, Y, K) which are the color values of the four-dimensional data is provided. Therefore, when the color conversion table is used, an arbitrary color expressed in RGB can be expressed in CMYK. However, if all the colors (about 16.77 million colors) expressed by 8 bits (256 gradations) of each color have corresponding data, the amount of data becomes enormous. Includes data only for colors in which each color is expressed by a predetermined number n of gradations smaller than 256.

  FIG. 2 is a diagram representing the color conversion table in three dimensions. The example shown in FIG. 2A shows a case where each RGB color is expressed by 18 gradations (n = 18). In this color conversion table, each RGB axis in the RGB color space is divided into 17 parts. A CMYK value (C, M, Y, K) is assigned to each grid (R, G, B).

  When the color to be converted is not on the grid, the color conversion unit 122 calculates a corresponding (C, M, Y, K) value using an interpolation method such as “tetrahedral interpolation”. In this case, for example, when color conversion is performed for the color indicated by the point O in FIG. 2A, it is associated with eight grid points (A to H) of the unit cube including the point O ( The (C, M, Y, K) values for the O point can be obtained from the (C, M, Y, K) values (values shown in FIG. 2B).

  The forward path LUT 125 and the backward path LUT 126 are respectively the forward path printing and the backward path printing when the printer 2 uses a printing medium of a predetermined paper type (hereinafter referred to as a standard paper type; first type printing medium). And the data adjusted so that the difference in color after printing is minimized. The forward path LUT 125 and the backward path LUT 126 are stored in a ROM, an HDD, or the like.

  The α table 127 is a table in which a coefficient α that is an adjustment value is stored corresponding to the printing conditions. In the present embodiment, the α table 127 stores, for each paper type (printing condition) of the print medium used in the printer 2, information in which the paper type coefficient α is associated with the paper type identification information. The coefficient α is set so that when the printer 2 uses a print medium of the corresponding paper type (in the case of the second printing condition), the difference in color after printing between the forward printing and the backward printing is minimized. This is a coefficient for generating an adjusted color conversion table (third LUT, third color conversion information). Although details will be described later, the color conversion unit 122 includes a forward path LUT (first color conversion information) 125 and a backward path LUT (second color conversion information) 126 of the first printing condition (standard paper type), Third color conversion information is generated from the coefficient α and used for color conversion processing.

  FIG. 3 is a diagram showing an example of the α table 127. In the example shown in FIG. 3, for the paper types “AA”, “BB”, “CC”,..., The corresponding coefficient α values “1.0”, “0.8”, “1.4”. ", ... are stored. The paper type “AA” is a standard paper type (first printing condition). As the paper type, for example, there are types called plain paper, glossy paper, synthetic paper, fine paper, Japanese paper, and the like.

  The value of each coefficient α is transmitted from a color conversion information adjustment unit 212 (adjustment unit) of the printer 2 described later and stored in the α table 127. The process of determining the coefficient α by the color conversion information adjustment unit 212 will be described later. The α table 127 is stored in a ROM, HDD, or the like.

  The printer 2 is a color inkjet printer that executes a printing process in accordance with a printing instruction from the host computer 1. The printer 2 performs printing by synchronizing the operation in the main scanning direction of the print head 225 provided with the nozzles that eject ink (coloring material) onto the printing medium and the operation in the sub-scanning direction of the paper that is the printing medium. Then, reciprocal printing (bidirectional printing) in which ink is ejected in both directions of the operation of the print head 225 is performed.

  As shown in FIG. 1, the printer 2 includes a controller unit 21 and a printing mechanism unit 22.

  The controller unit 21 includes a program describing processing contents, a CPU that executes processing according to the program, a RAM, a ROM that stores the program, an ASIC, and the like. As a functional configuration, as shown in FIG. 1, a print control unit 211 and a color conversion information adjustment unit 212 are provided.

  The print control unit 211 is a part that receives print data according to a print instruction and causes the print mechanism unit 22 to execute print processing according to the print data. The print control unit 211 controls each of a main scanning unit 221 and a sub-scanning unit 222 which will be described later. Further, the print control unit 211 causes the printing mechanism unit 22 to execute patch printing for determining the value of the coefficient α in accordance with an instruction from the color conversion information adjustment unit 212.

  The color conversion information adjustment unit 212 is a part that executes processing for determining the value of the coefficient α. The process executed by the color conversion information adjustment unit 212 is a feature of the printer 2, and specific processing contents will be described later.

  The printing mechanism unit 22 is a part that executes a printing process on a print medium (paper) in accordance with an instruction from the controller unit 21. As illustrated in FIG. 1, the printing mechanism unit 22 includes a main scanning unit 221 and a sub-scanning unit 222. Note that the print control unit 211 and the print mechanism unit 22 surrounded by a broken line in FIG.

  The main scanning unit 221 includes a print head 225 that includes nozzles 227 for ejecting CMYK inks, a carriage 224 that includes the print head 225 and moves in the main scanning direction, and a carriage motor 223 for driving the carriage 224. Etc.

  FIG. 4 is a plan view of the print head 225 viewed from the nozzle surface side. In this embodiment, the print head 225 includes a plurality of nozzles 227 corresponding to the respective colors of black (K), magenta (M), yellow (M), and cyan (C) in the sub-scanning direction (conveyance of the print medium). The nozzle row 228 is arranged corresponding to each color. In the present embodiment, 180 nozzles 227 are arranged in a staggered manner in each nozzle row 228 at a pitch of 180 dpi.

  The print heads 225 are arranged in the main scanning direction (movement direction of the carriage 224) in the order of K → M → Y → C. In forward printing, ink is ejected in the order of K → M → Y → C, and the return path In printing, ink is ejected in the order of C → Y → M → K. Therefore, since the ink ejection order is different between the forward path and the backward path, the ink stacking order is changed, and the color development characteristics are changed between the forward path and the backward path. Therefore, when the same color conversion process is performed in both directions, a color difference (color unevenness) occurs between the forward pass print area and the return pass print area. For this reason, in this embodiment, two color conversion tables (first LUT and second LUT) for forward printing and backward printing are used in the color conversion processing. Furthermore, when the first LUT and the second LUT are used, the color difference can be reduced under the first printing condition, but the color difference may not be reduced under the second printing condition. In this case, the third LUT is used as described above. In the present embodiment, there is a difference in ink characteristics depending on the paper type between the first printing condition and the second printing condition.

  The sub-scanning unit 222 is a device that conveys the print medium 229 in the sub-scanning direction. The sub-scanning unit 222 includes a paper feed motor 226 and the like for moving the print medium 229 in synchronization with the operation of the print head 225.

  FIG. 5 is a diagram for explaining the operation of the carriage 224 with respect to the print medium 229. FIG. 5 shows a relative positional relationship between the print medium 229 and the carriage 224, and the carriage 224 moves relative to the print medium 229 in the direction of the arrow shown. The printer 2 performs printing while moving the carriage 224 in the main scanning direction from the printing start position (home position) P at the position indicated by the dotted line. When the printer 2 finishes printing to the end of the print image, it temporarily stops moving the carriage 224, conveys the paper in the sub-scanning direction, and performs printing while moving the carriage 224 to the print start position P side. Then, the printer 2 stops the movement of the carriage 224 when printing is completed to the end of the print image, and after printing in the sub-scanning direction, performs printing while moving the carriage 224 in the main scanning direction again.

  As described above, the printer 2 performs printing while repeating the printing in the main scanning direction and the paper feeding operation in the sub-scanning direction. In the present embodiment, printing when the carriage 224 moves in the right main scanning direction with respect to the sub-scanning direction is referred to as “forward printing”, and printing when it moves in the left main scanning direction is referred to as “return printing”. Further, image data for one pass corresponding to a print image in a print area printed by one forward printing or backward printing is referred to as “partial image data”.

  That is, the first partial image data (first partial image data) is printed by the first forward printing. Further, the second partial image data (second partial image data) is printed by the subsequent backward printing, and the third partial image data (third partial image data) is printed by the subsequent forward printing. That is, odd-numbered partial image data is printed by forward printing, and even-numbered partial image data is printed by backward printing. When all the images have been printed, the carriage 224 is moved to the print start position P and waits for the next print instruction.

  In the printing system 100 according to the present embodiment having the configuration described above, processing is executed in the following procedure.

  First, a process for determining a coefficient α for generating a color conversion table (third LUT) for return pass printing according to the paper type of the print medium will be described. FIG. 6 is a flowchart illustrating an example of the coefficient α determination process. 6 is described as processing contents of the color conversion information adjustment unit 212.

  In this process, first, a process of printing patch images corresponding to a plurality of α values is performed. The user activates the color conversion information adjustment unit 212 from an operation unit (not shown) of the printer 2. Thereafter, the user inputs the print color (patch color), the interval and range of the α value, and the paper type identification information from the operation unit of the printer 2, and the color conversion information adjustment unit 212 acquires the information ( Step S1) in FIG.

  The print color is a representative color for determining the LUT (3), and a color for enabling an effective color conversion process with little error is selected for the paper type. The print color can be determined in several ways.

  One of them is a method of selecting a color having the largest color difference between the LUT (1) and the LUT (2). The converted color (C1, M1, Y1, K1) stored in association with the color (R, G, B) in the LUT (1) and the color (R, G, B) in the LUT (2) Differences (ΔC = C2-C1, ΔM = M2-M1, ΔY = Y2-Y1, ΔK = K2−) for each color component of the converted colors (C2, M2, Y2, K2) stored in association with each other. The color with the maximum sum (ΔC + ΔM + ΔY + ΔK) of K1, is selected.

  Further, as an option of this method, a predetermined number (for example, 10) of colors having a large color difference is selected, and a color (black ink) having the smallest K value (K2 value) among the predetermined number of colors is selected. It is also possible to select a color with a small amount) as the printing color.

  The second method is a method of setting a color specified by the user of the printer system 100. This method is effective when there are important colors that do not want to cause uneven color.

  The third method is a method for obtaining a frequently used color in the printer system 100.

  Next, the interval and range of the α values are the pitch of the α value corresponding to the patch image to be generated and the minimum / maximum values. For example, if the interval is 0.2 and the range is 0 to 2.0, the α value increases in increments of 0.2 from the patch image corresponding to α = 0 to the patch image corresponding to α = 2.0. Each corresponding patch image is generated, and a total of 11 patch images are generated (printed).

  The color conversion information adjustment unit 212 that has acquired the information from the host computer 11 uses the post-conversion LUT 125 and the return path LUT 126 after conversion corresponding to the acquired print colors (R, G, B). The values of the colors (C1, M1, Y1, K1) and (C2, M2, Y2, K2) are acquired (step S2 in FIG. 6).

Next, the color conversion information adjustment unit 212 calculates the color (C3, M3, Y3, K3) of each patch image to be generated (step S3 in FIG. 6). In other words, candidate colors in the LUT (3) are determined. Specifically, each α value for generating a patch image is obtained from the interval and range of the α values acquired in step S1, and the color (C3, M3, Y3, K3) of the patch image corresponding to each α value is obtained. Calculate with the following formula.
C3 = C1 + α × (C2-C1)
M3 = M1 + α × (M2-M1)
Y3 = Y1 + α × (Y2−Y1)
K3 = K1 + α × (K2-K1)
In the above-described example in which the α value interval is 0.2 and the α value range is 0 to 2.0, α = 2 in the order of α = 0.0, α = 0.2, α = 0.4. Up to .0, eleven patch image colors (C3, M3, Y3, K3) are determined.

  Next, the color conversion information adjustment unit 212 generates patch image print data according to the calculated color (C3, M3, Y3, K3) of the patch image (step S4 in FIG. 6). FIG. 7 is a diagram illustrating a printed patch image. In (A) and (B) of FIG. 7, each rectangular image (PC in the figure) with numbers (patch identification information) such as (1) and (2) is a patch corresponding to each α value. It is an image.

  Each patch image has a configuration in which two rectangles are arranged adjacent to each other in the main scanning direction (FIG. 7A) or the sub-scanning direction (FIG. 7B). Of the two rectangles, the left rectangle in FIG. 7A and the upper rectangle in FIG. 7B are images at the time of forward printing, that is, the color (C1 after conversion in the forward LUT 125). , M1, Y1, K1), the right rectangle in FIG. 7A and the lower rectangle in FIG. 7B are candidate images for return pass printing, that is, step S3. It is an image of the color (C3, M3, Y3, K3) calculated in (1).

  In each patch image ((1), (2),...), The image at the time of forward printing is the same color (color data), and the candidate image at the time of backward printing is determined by the α value indicated below the image. An image of the calculated color (color data), and an image of a different color depending on the α value.

  As described above, the patch image generated by the printing system 100 is printed on the second type printing medium so that the color in the forward printing and the color in the backward printing can be easily compared.

  The color conversion information adjustment unit 212 generates print data for printing such a patch image. Specifically, the color conversion information adjustment unit 212 firstly corresponds to the values of (C1, M1, Y1, K1) acquired in step S2 and the respective α values calculated in step S3 (C3, M3, Y3). The image data (data in which each pixel has a color value) of each patch image described above is generated from the value of K3) and position information of each patch image determined in advance.

  Next, the color conversion information adjustment unit 212 performs halftone processing similar to the processing by the halftone processing unit 123 on the generated image data, generates dot data, and the print control unit 211 generates the generated dot data. The data is in an interpretable format.

  Further, the color conversion information adjustment unit 212 generates patch identification information for each patch image, and includes the image of the patch identification information in the print data so that the patch identification information is printed beside the corresponding patch image. Further, the color conversion information adjustment unit 212 stores the patch identification information and the α value of the patch image corresponding to the patch identification information in association with each other.

  When the print data of the patch image is generated in this way, the color conversion information adjustment unit 212 passes the print data to the print control unit 211 and instructs to print the patch image (step S5 in FIG. 6).

  Upon receiving the print instruction, the print control unit 211 interprets the received print data, controls the printing mechanism unit 22 based on the interpretation result, and causes the printing mechanism unit 22 to print a patch image. As a result, a patch image as illustrated in FIG. 7 is printed on the print medium (paper) 229. Note that the print medium (paper) 229 to be printed is a paper type print medium based on the paper type identification information acquired by the color conversion information adjustment unit 212 in step S1. Further, the patch identification information attached to each patch image described above is also printed beside each patch image, as shown in FIG. Further, the α value of each patch image shown in FIG. 7 may not be printed.

  When the patch image is printed in this way, the user of the printing system 100 checks each patch image (for example, visually checks), and the color difference between the forward pass image and the return pass image (see (A) in FIG. 7). In the example shown, the patch image with the smallest color difference between the left and right rectangles of each patch image is selected. The user inputs the patch identification information (patch number, (1), (2), etc. in the example shown in FIG. 7) to be printed next to the selected patch image to the printer 2. In the example shown in FIGS. 7A and 7B, since the color difference between the forward path image and the backward path image in the patch image with the patch number (3) is minimized, the information of the patch number (3) is input to the printer 2. The Note that the patch identification information is input via an operation unit (not shown) provided in the printer 2.

  The color conversion information adjustment unit 212 acquires the input patch identification information (step S6 in FIG. 6). Thereafter, the color conversion information adjustment unit 212 acquires the α value stored in association with the acquired patch identification information, and transmits the α value to the host computer 1 together with the paper type identification information acquired in step S1. (Step S7 in FIG. 6). In the example shown in FIG. 7, since the patch number (3) is selected by the user, “0.4” is transmitted to the host computer 1 as the α value.

  The transmitted α value and paper type identification information are stored in the α table 127 of the printer driver unit 12 in association with the paper type identification information.

  In this way, the process of determining the coefficient α for generating the color conversion table (LUT (3)) for return pass printing according to the paper type of the print medium is performed.

  In the above description, for one paper type, one print color is designated to generate a patch image, and the α value is determined from the patch image. However, a plurality of print colors may be designated. In this case, the processing of steps S2 to S5 described above is executed for each designated color, and the patch image with a small color difference is selected from the output patch images, and the α value is determined. Then, the average value of the determined α values is determined as the α value of the paper type.

  Next, an overall procedure from when the application unit 11 issues a print request to when the printer 2 performs print processing will be described.

  FIG. 8 is a flowchart illustrating an example of a processing procedure in the printing system 100. When a print request is made by the application unit 11, the printer driver unit 12 receives a print request including original image data (step S11 in FIG. 8). Note that the print request includes information on the paper type of the print medium used in the printer 2 (hereinafter referred to as paper type identification information) as one of the printing conditions.

  The received print request information is passed to the rendering unit 121, and the rendering unit 121 performs rendering processing on the original image data included in the print request to generate RGB pixel data (step S12 in FIG. 8). .

  The print request including the generated RGB pixel data is transferred to the color conversion unit 122, and the color conversion unit 122 performs color conversion processing to convert the RGB pixel data into CMYK pixel data (step S13 in FIG. 8). In the color conversion process, the color conversion unit 122 uses the forward path LUT (first color conversion information), the backward path LUT (second color conversion information), and the adjustment table (α table) 127 for the backward path. The third LUT (third color conversion information) is generated, and processing corresponding to the paper type indicated by the paper type identification information is executed using the third LUT. Specific contents of the color conversion process will be described later.

  The print request including the generated CMYK pixel data is transferred to the halftone processing unit 123, and the halftone processing unit 123 performs halftone processing on the CMYK pixel data and converts the CMYK pixel data into dot data ( Step S14 in FIG.

  The print request including the generated dot data is passed to the command generation unit 124, and the command generation unit 124 generates print data that represents the print request with a command for the printer 2 (step S15 in FIG. 8).

  The host computer 1 transmits the generated print data to the printer 2 (step S16 in FIG. 8).

  The printer 2 receives the print data and executes print processing according to the command included in the print data (step S17 in FIG. 8). Specifically, the controller unit 21 interprets the command and controls the main scanning unit 221 and the sub scanning unit 222 of the printing mechanism unit 22 based on the interpretation result. The printing mechanism unit 22 operates according to the control, and performs printing by ejecting ink onto the printing medium indicated by the paper type identification information by the reciprocating operation of the printing head 225 described above.

  As described above, the processing from the print request to the print execution is performed.

  FIG. 9 is a flowchart illustrating the procedure of the color conversion process (step S13 in FIG. 8) by the color conversion unit 122.

  First, the color conversion unit 122 acquires data of the forward path LUT 125 and the backward path LUT 126 (step S131 in FIG. 9).

  Thereafter, the color conversion unit 122 obtains a difference (hereinafter referred to as DIF) between the ink amounts (color material amounts) of the forward path LUT 125 and the backward path LUT 126 (step S132 in FIG. 9). Specifically, the color conversion unit 122 stores (C, M, Y, K) (hereinafter referred to as (C2, M2, B2)) in the return path LUT 126 for each of the grid points (R, G, B) described above. Y2 and K2)) (C, M, Y, K) (hereinafter referred to as (C1, M1, Y1, K1)) stored in the forward path LUT 125. The value obtained by subtracting the value of each corresponding color is obtained. That is, the color conversion unit 122 obtains ΔC = C2-C1, ΔM = M2-M1, ΔY = Y2-Y1, and ΔK = K2-K1 for each grid point (R, G, B).

  Next, the color conversion unit 122 refers to the α table 127 and acquires the value of the coefficient α (step S133 in FIG. 9). Specifically, the color conversion unit 122 reads the value of the coefficient α stored in the α table 127 in association with the paper type of the paper type identification information included in the print request. In the example of FIG. 3, when the paper type is “BB”, the color conversion unit 122 acquires a value of 0.8 as the value of the coefficient α.

  Next, the color conversion unit 122 generates third color conversion information for return pass printing that matches the paper type indicated by the paper type identification information (step S134 in FIG. 9). The color conversion unit 122 generates the third color conversion information by reflecting the difference in the ink amount between the forward path LUT 125 and the backward path LUT 126 at a rate proportional to the value of the acquired coefficient α in the forward path LUT 125. To do.

Specifically, (C, M, Y, K) (hereinafter referred to as (C3, M3, Y3, K3)) associated with each grid point (R, G, B) of the third color conversion information is It calculates | requires by the following formula | equation for every grid point.
C3 = C1 + α × ΔC
M3 = M1 + α × ΔM
Y3 = Y1 + α × ΔY
K3 = K1 + α × ΔK
Note that the grid points (R, G, B) are the same in the forward path LUT 125, the backward path LUT 126, and the third LUT.

  Next, the color conversion unit 122 converts the RGB pixel data into CMYK pixel data using the forward LUT 125 and the third LUT (step S135 in FIG. 9). In the conversion process, the color conversion unit 122 generates CMYK pixel data using the forward LUT 125 for RGB pixel data used in forward printing, and uses the third LUT for RGB pixel data used in backward printing. To generate CMYK pixel data. More specifically, for each pixel of the RGB pixel data, the color conversion unit 122 has (R, G, B) that the pixel has, and the (R, G, B) is a color conversion table (forward path LUT 125 or In the case of the grid point of the third LUT), (C, M, Y, K) stored in the grid point in the color conversion table and (R, G, B) are the color conversion table. If it is not a grid point, it is converted to (C, M, Y, K) obtained by the above interpolation calculation using (C, M, Y, K) stored in the surrounding grid points.

  As described above, for the backward printing, a color conversion table (third LUT) adjusted so as to minimize the color difference between the forward printing and the backward printing according to the paper type to be used is used.

  The color conversion process is executed with the contents described above. The color conversion unit 122 may hold the generated third LUT until processing for the next print request. In this case, if the paper type designated by the next print request is the same paper type as the third LUT held by the next print request, the color conversion unit 122 performs steps S31 to S31 in the color conversion process for the next print request. The process of S34 is omitted, and the third LUT stored in step S35 can be used.

  In the above description, the color conversion table for return pass printing is changed (adjusted) based on the coefficient α. However, the color conversion table for forward pass printing may be changed according to the paper type. In this case as well, a new color conversion table for forward printing is generated from the difference between the forward path LUT 125 and the backward path LUT 126 using a coefficient predetermined for each paper type, and the generated color conversion table is Used for color conversion processing.

  Alternatively, a corresponding third LUT may be generated and stored in advance for each paper type, and the third LUT may be used during color conversion processing.

  In the printing system 100 according to the present embodiment, the α value determination process is executed by the color conversion information adjustment unit 212 on the printer 2 side. However, the same process may be performed on the host computer 1 side.

  Further, in the printing system 100 according to the present embodiment, the color conversion processing is performed on the host computer 1 side, but may be performed on the printer 2 side.

  In this embodiment, the color conversion table is adjusted according to the paper type in the printing conditions. However, the color conversion table is adjusted according to other printing conditions such as temperature and humidity. Also good.

  As described above, in the printing system according to the present embodiment and the modification thereof, the value of the coefficient α for generating an appropriate color conversion table corresponding to the printing condition such as the paper type is used as the printed patch image. Since the user can visually determine (sample image), the color conversion table can be easily adjusted.

  Further, since the patch image to be printed is a filled image and the images to be compared are arranged adjacent to each other, the color difference is easy to understand, and the user can make an accurate determination.

  In addition, by specifying a color with a large color difference as a printing color when determining the α value, it is possible to adjust the color conversion table with little error, and as a result, it is possible to suppress the color difference between forward printing and backward printing.

  Also, in the color conversion process at the time of printing, since the color conversion table for the forward printing or the backward printing appropriately adjusted by the coefficient α for each printing condition is used, the color difference between the forward printing and the backward printing in each printing condition. Can be kept small.

  In this embodiment, the color conversion process from the RGB color space to the CMYK color space is described. However, the present invention can be applied to a color conversion process in a different color space.

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

  1 host computer, 2 printer, 11 application unit, 12 printer driver unit, 21 controller unit, 22 printing mechanism unit, 23 printing unit, 100 printing system, 121 rendering unit, 122 color conversion unit, 123 halftone processing unit, 124 command Generation unit, 125 forward path LUT, 126 return path LUT, 127 adjustment table, 211 print control unit, 212 color conversion information adjustment unit, 221 main scanning unit, 222 sub scanning unit, 223 carriage motor, 224 carriage, 225 print head, 226 Paper feed motor, 227 nozzle, 228 nozzle row, 229 Print medium (paper)

Claims (8)

A printing unit that performs bidirectional printing on a print medium;
A first direction print image using first direction color conversion information for the first type print medium and a second direction print image using second direction color conversion information for the second type print medium are printed on the printing unit. And an adjustment unit that prints the second type print medium in a comparable manner.
The second direction color conversion information for the second type print medium is generated by adjusting the second direction color conversion information for the first type print medium. In claim 1,
The printing apparatus, wherein the first direction print image and the second direction print image are images filled with a predetermined color. In claim 1 or 2,
The adjustment unit is
The printing apparatus, wherein the first direction print image and the second direction print image are printed adjacent to each other. In any one of Claims 1 thru | or 3,
The adjustment unit is
Adjusting the second direction color conversion information for the second type print medium based on a predetermined coefficient;
A plurality of the second direction print images using a plurality of second direction color conversion information for the second type print medium adjusted based on each of the plurality of values of the predetermined coefficient, respectively, in the first direction A printing apparatus that prints a print image in pairs. In claim 4,
The adjustment unit acquires identification information of one second direction print image input corresponding to printing of the plurality of second direction print images, and is identified by the acquired identification information. A printing apparatus that stores a value of the predetermined coefficient corresponding to a direction print image. In claim 5,
The printing unit
During the first direction printing, printing is performed based on the image data converted using the first direction color conversion information for the first type print medium,
At the time of second direction printing, printing is performed based on image data converted using the second direction color conversion information for the second type print medium adjusted based on the stored value of the predetermined coefficient. A printing apparatus characterized by that. Printing a first direction print image using the first direction color conversion information for the first type print medium;
Generating second direction color conversion information for the second type print medium adjusted from the second direction color conversion information for the first type print medium;
A printing method comprising: printing a second direction print image using the second direction color conversion information for the second type print medium so as to be comparable with the first direction print image. A printing system comprising a host device and a printing device,
The printing apparatus includes:
A printing unit that performs bidirectional printing on a print medium based on image data generated by the host device;
A first direction print image using first direction color conversion information for the first type print medium and a second direction print image using second direction color conversion information for the second type print medium are printed on the printing unit. And an adjustment unit that prints the second type print medium in a comparable manner.
The host device is
The second direction image data in the first direction is generated using the first direction color conversion information for the first type print medium, and adjusted using a value of a predetermined coefficient determined based on printing by the adjustment unit. A driver unit that generates the image data in the second direction using the second direction color conversion information for the seed print medium;
The second direction color conversion information for the second type print medium is generated by adjusting the second direction color conversion information for the first type print medium.

Images