JP6424696B2 - Printing apparatus, printing method, and printing system - Google Patents

Description

  The present invention relates to a printing apparatus and the like that perform reciprocating printing, and more particularly to a printing apparatus that can reduce a color difference in forward pass printing and return pass printing regardless of printing conditions such as a paper type.

  Conventionally, there is a printer that performs printing in synchronization with the operation of the print head in the main scanning direction and the sheet feeding operation in the sub-scanning direction. In such a printer, it is known that reciprocating printing (bidirectional printing) is performed in which printing is performed in both the forward pass and the return pass of the print head in order to improve the printing speed. This reciprocating printing is also widely adopted in color ink jet printers, but there is a problem that the order in which the inks overlap differs between the forward pass and the return pass depending on the arrangement of the nozzle rows of each color, and a color difference occurs between the forward pass and the return pass. The

  With respect to this problem, Patent Document 1 below proposes a technique for eliminating color unevenness due to differences in the order of overlapping of colorants in reciprocating printing, and the document includes a color processing look-up table (LUT) for the forward pass. Processing using two LUTs of a color processing look-up table (LUT) for return is described.

  Further, Patent Document 2 described below describes a technique for matching the color tone of an image recorded during forward movement with the color tone of an image recorded during backward movement with high accuracy. It is described that the image of the return path of the image is made to be able to be compared with the image of the return path.

JP 2007-136845 A JP 2004-34435 A

  However, even if the color difference in forward printing and return printing is adjusted to the minimum according to the background art described above, the color difference becomes large when the printing conditions such as the type of paper (paper type) as the printing medium are changed. There is a problem that The said patent document 1, 2 does not show the solution regarding the said subject.

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

  Therefore, an object of the present invention is to provide a printing apparatus that performs reciprocating printing, and is capable of reducing a color difference in forward pass printing and return pass printing regardless of printing conditions such as paper type. is there.

  In order to achieve the above object, according to one aspect of the present invention, there is provided a printing unit performing bidirectional printing on a printing medium, and a first direction printing image using first direction color conversion information for a first type printing medium. And an adjusting unit that causes the printing unit to print the second direction print image using the second direction color conversion information for the second type print medium so as to be compared with the second type print medium. The second direction color conversion information for the two types of print media is generated by adjusting the second direction color conversion information for the first type of print media.

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

  Furthermore, in the above-described invention, in one preferable aspect, the adjustment unit adjusts second direction color conversion information for the second type print medium based on a predetermined coefficient, and the plurality of values of the predetermined coefficient are adjusted. Printing a plurality of the second direction print images using the second direction color conversion information for the plurality of second type print media adjusted based on each other in pairs with the first direction print image; It is characterized by

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

  Furthermore, in the above-mentioned invention, in a preferable aspect, 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 the second direction printing, printing is performed based on the 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.

  In order to achieve the above object, another aspect of the present invention is to print a first direction print image using first direction color conversion information for a first type print medium, and for the first type print medium Generating second direction color conversion information for the second type print medium by adjusting the second direction color conversion information, and generating a second direction print image using the second direction color conversion information for the second type print medium, The printing method is characterized by printing comparably to the first direction print image.

  In order to achieve the above object, another aspect of the present invention is a printing system comprising a host device and a printing device, wherein the printing device is both based on image data generated by the host device on a print medium. Printing unit for performing a directional printing, a first direction print image using first direction color conversion information for a first type print medium, and a second direction using second direction color conversion information for a second type print medium An adjustment unit that causes the print unit to print the print image so as to be contrastable on the second type print medium, and the host device uses the first direction color conversion information for the first type print medium to execute the first The second direction color conversion information for a second type print medium, which generates the image data in one direction and is 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 be apparent from the embodiments of the invention described below.

1 is a configuration diagram according to an embodiment of a printing system provided with a printing apparatus to which the present invention is applied. It is the figure which expressed the color conversion table in three dimensions. FIG. 7 is a diagram showing an example of an α table 127. FIG. 6 is a diagram illustrating the configuration of a carriage 224. FIG. 16 is a diagram for describing an operation of the carriage 224 with respect to a print medium (paper) 229. It is a flow chart which shows an example of decision processing 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 color conversion processing.

  Hereinafter, embodiments of the present invention will be described 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 components are described with the same reference numerals or 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. The 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 reciprocating printing (bidirectional printing), and in forward printing, image data subjected to color conversion processing using a forward color conversion table (forward LUT 125, first direction color conversion information) Image data printed on the basis of the color conversion processing using the color conversion table for return path (LUT for return path) adjusted according to the type (paper type) of paper which is the printing medium to be used in the return path printing Print based on. Also, the printer 2 determines the coefficient α (predetermined coefficient) for adjusting the color conversion table for the return path according to the paper type, each of the forward print image (first direction print image) and the coefficient α In order to print out a pair of return pass print images (second direction print images) adjusted by the value as a pair, and to adjust the value of the coefficient α of the return pass print image selected by the user for the color conversion table for return pass It is determined as the value of the coefficient α of By the processing of the printer 2, it is possible to suppress the color difference in the forward pass printing and the return pass printing for each paper type to be small, and further, it is possible to easily perform the preparation operation therefor.

  As shown in FIG. 1, a printing system 100 according to the present embodiment includes a host computer 1 and a printer 2 which is a color inkjet printer that performs reciprocating printing.

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

  The application unit 11 is a print request source for the printer 2, and when printing is requested, image data to be printed on the printer driver unit 12 by an instruction operation to the host computer 1 by the user (hereinafter referred to as original image data) Send The original image data is data in a standard format (for example, a format in accordance with GDI (Graphic Data Interface)) representing a print target such as characters and graphics in object units. In addition, in the original image data, the color of the image is expressed, for example, by RGB (red, green, blue) multi-value (for example, 256 gradations of 0 to 255). The application unit 11 is configured of a program in which the process content is described, a CPU that executes the process according to the program, a RAM, and the like.

  The printer driver unit 12 bears a driver function for the printer 2 and performs various processes on the original image data output from the application unit 11 to generate print data for the printer 2 and the print data Send to printer 2. The printer driver unit 12 includes a driver program in which the processing content is described, 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 has a functional configuration including a rendering unit 121, a color conversion unit 122, a halftone processing unit 123, a command generation unit 124, a forward LUT 125, a backward LUT 126, and , 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 units of pixels. That is, the rendering unit 121 converts the original image data into image data in which each pixel has RGB multiple values (for example, 256 gradations of 0 to 255 each). The image data in pixel units is hereinafter referred to as RGB pixel data.

  The color conversion unit 122 is a color data (RGB as an example (here, CMYK (cyan, magenta, yellow, black)) used to represent the RGB pixel data generated by the rendering unit 121. Hereinafter, the processing (color conversion processing) for converting into CMYK pixel data) is performed. The CMYK pixel data is ink amount data in which each pixel has CMYK multiple values (for example, 256 gradations of 0 to 255 each). 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 makes adjustments in accordance with the printing conditions such as the type of paper (paper type), which is the printing medium used by the printer 2, in the color conversion process for backward printing of the printer 2. The processing is characterized by this printing system. The 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 represented by the presence or absence of a print dot. In the present embodiment, the halftone processing unit 123 converts CMYK pixel data into data (hereinafter referred to as dot data) expressed by the presence or absence of each print dot of CMYK. The printing dots are dots formed on a printing medium (paper) by the ejection of ink by the printer 2. As an example, a plurality of dots of different sizes of large, medium, and small are used. In this case, the dot data includes information indicating the presence or absence of a large dot, the presence or absence of a medium dot, and the presence or absence of a small dot of each color for each position of the printing medium to which the ink is ejected.

  The command generation unit 124 is a part that expresses a print request including image data to be printed by 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 generating a print request (print data), the command generation unit 124 expresses dot data as a command for the printer 2 and includes the dot data in the print data.

  The forward LUT (first LUT, first color conversion information) 125 and the backward LUT (second LUT, second color conversion information) 126 are a color conversion table for forward printing in the printer 2 and It is a color conversion table (color conversion information) for return path 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. In other words, the color conversion table 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 are color values 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 It has information assigned to (C, M, Y, K) which is color values of four-dimensional data. Therefore, by using the color conversion table, any color expressed in RGB can be expressed in CMYK. However, if the corresponding data is held for all the colors (about 16.77 million colors) represented by 8 bits (256 gradations) of each color, the amount of data becomes enormous, so in practice the color conversion table The data is provided only for the color that represents each color by a predetermined number n of gradations less than 256.

  FIG. 2 is a diagram representing the color conversion table in three dimensions. The example shown in (a) of FIG. 2 shows the case where each color of RGB is expressed with 18 gradations (n = 18), and in this color conversion table, each axis of RGB in the RGB color space is divided into 17 CMYK values (C, M, Y, K) are assigned to the grids (R, G, B).

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

  The forward pass LUT 125 and the return pass LUT 126 are respectively forward pass print and return pass print when a print medium of a predetermined paper type (hereinafter referred to as a standard paper type) is used in the printer 2. And fit the adjusted data so as to minimize the color difference after printing. The forward LUT 125 and the backward LUT 126 are stored in the ROM, HDD, or the like.

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

  FIG. 3 is a diagram showing an example of the α table 127. As shown in FIG. 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). Examples of paper types include types called plain paper, glossy paper, synthetic paper, fine paper, and Japanese paper, and even in the case of plain paper, paper types differ depending on the manufacturer.

  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. Further, the α table 127 is stored in the ROM, HDD or the like.

  The printer 2 is a color inkjet printer that executes printing processing in accordance with a printing instruction of the host computer 1. The printer 2 performs printing by synchronizing the operation in the main scanning direction of the print head 225 having a nozzle for discharging ink (color material) onto the printing medium and the operation in the subscanning direction of the paper as the printing medium. In the two-way operation of the print head 225, reciprocating printing (two-way printing) is performed in which ink is discharged.

  The printer 2 includes a controller unit 21 and a print mechanism unit 22 as shown in FIG.

  The controller unit 21 includes a program in which the process content is described, a CPU that executes the process 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 portion 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 respective units of a main scanning unit 221 and a sub scanning unit 222 described later. Further, the print control unit 211 causes the print 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 process contents will be described later.

  The print mechanism unit 22 is a portion that executes print processing on a print medium (paper) according to an instruction of the controller unit 21. The printing mechanism unit 22 includes a main scanning unit 221 and a sub-scanning unit 222, as shown in FIG. The print control unit 211 and the print mechanism unit 22 surrounded by the broken line in FIG.

  The main scanning unit 221 includes a print head 225 having a nozzle 227 for discharging ink of each color of CMYK, a carriage 224 which mounts 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 the present embodiment, in the print head 225, a plurality of nozzles 227 corresponding to each color of black (K), magenta (M), yellow (M), and cyan (C) are arranged in the sub-scanning direction In the direction, the nozzle row 228 is arranged corresponding to each color. In the present embodiment, 180 nozzles 227 are arranged in a staggered manner at a pitch of 180 dpi in each nozzle row 228.

  The print heads 225 are arranged in the order of K → M → Y → C in the main scanning direction (moving direction of the carriage 224), and in forward printing, eject ink in the order of K → M → Y → C, and return In printing, the ink is ejected in the order of C → Y → M → K. Therefore, since the discharge order of the ink is different between the forward pass and the return pass, the stacking order of the ink is changed, and the color development characteristics are changed between the forward pass and the return pass. Therefore, if the same color conversion processing is performed in both directions, a color difference (uneven color) occurs between the forward pass print area and the return pass print area. For this reason, in the present embodiment, two color conversion tables (first LUT and second LUT) for forward pass printing and return pass printing are used in the color conversion process. 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 able to be reduced under the second printing condition. In this case, as described above, the third LUT is used. In the present embodiment, in the first printing condition and the second printing condition, there are differences in the ink characteristics depending on the paper type.

  The sub-scanning unit 222 is a device for transporting 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 the 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 indicated by the arrow. 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 printing is finished up to the end of the print image, the printer 2 temporarily stops moving the carriage 224, transports the paper in the sub-scanning direction, and performs printing while moving the carriage 224 to the printing start position P side. Then, when printing is finished up to the end of the print image, the printer 2 again stops the movement of the carriage 224, and after paper feeding in the sub scanning direction, printing is performed while moving the carriage 224 in the main scanning direction again.

  Thus, the printer 2 performs printing while repeating printing in the main scanning direction and paper feeding operation in the sub-scanning direction. In the present embodiment, printing when the carriage 224 moves in the right-hand main scanning direction with respect to the sub-scanning direction is referred to as "forward pass printing", and printing when moving in the left-hand main scanning direction is referred to as "return pass printing". Also, image data for one pass corresponding to a print image of a print area printed by one forward pass printing or return pass 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. Also, the second partial image data (second partial image data) is printed by the subsequent return printing, and the third partial image data (third partial image data) is printed by the subsequent outward printing. That is, odd-numbered partial image data is printed in forward pass printing, and even-numbered partial image data is printed in backward pass printing. When printing of all the images is completed, the carriage 224 is moved to the print start position P, and the process waits for the next print instruction.

  In the printing system 100 according to the present embodiment having the configuration as described above, the process is performed according to the following procedure.

  First, processing 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 showing an example of the process of determining the coefficient α. 6 is described as processing contents of the color conversion information adjustment unit 212.

  In the 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 the 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 those information ( Step S1 of FIG.

  The print color is a representative color for determining the LUT (3), and a color is selected to enable effective color conversion processing with less error for the paper type. The printing color can be determined in several ways.

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

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

  The second method is to use a color designated by the user of the printer system 100. This method is effective when there are important colors that you do not want to cause color unevenness.

  The third method is a method of setting colors frequently used in the printer system 100.

  Next, the interval and range of the α value are the pitch and the minimum value / maximum value of the α value corresponding to the patch image to be generated. For example, if the interval is 0.2 and the range is 0 to 2.0, the patch image corresponding to α = 0 to the patch image corresponding to α = 2.0 is an α value that increases in 0.2 steps. 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 these pieces of information converts the converted print colors (R, G, B) that are acquired from the host computer 11 in the forward path LUT 125 and the backward path LUT 126, respectively. 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, the candidate color in LUT (3) is determined. Specifically, each α value for generating a patch image is obtained from the interval and range of α values acquired in step S1, and the color (C3, M3, Y3, K3) of patch image corresponding to each α value is calculated. Calculated using 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 example where the interval of the α value is 0.2 and the range of the α value is 0-2.0, α = 2 in the order of α = 0.0, α = 0.2 and α = 0.4. The color (C3, M3, Y3, K3) of 11 patch images is determined up to .0.

  Next, the color conversion information adjustment unit 212 generates print data of the patch image 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) to which numbers (patch identification information) such as (1) and (2) are attached corresponds to 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 the main scanning direction ((A) in FIG. 7) or the sub-scanning direction ((B) in FIG. 7). 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, colors after conversion in the forward LUT 125 (C1). , M1, Y1, K1), and the rectangle on the right side in FIG. 7A and the lower rectangle in FIG. It is an image of the color (C3, M3, Y3, K3) calculated by.

  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 the α value shown below the image It is an image of the calculated color (color data), and becomes 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 forward printing and the color in 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 first 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,. Image data of each patch image described above (data in which each pixel has a color value) is generated from the value of K3) and positional 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 to generate dot data, and the print control unit 211 generates the generated dot data. It is assumed to be interpretable data.

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

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

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

  When the patch image is printed in this manner, the user of the printing system 100 checks each patch image (for example, visually checks it), and the color difference between the forward image and the backward image (see FIG. 7A). In the example shown, the patch image having the smallest color difference between the left and right rectangles of each patch image is selected. The user inputs patch identification information (patch number, (1), (2) or the like in the example shown in FIG. 7) to be printed beside the selected patch image into the printer 2. In the example shown in FIGS. 7A and 7B, since the color difference between the forward pass image and the return pass image in the patch image of patch number (3) is minimized, the information of patch number (3) is input to the printer 2 Ru. The input of patch identification information is performed 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 12 with the α value being associated with the paper type identification information.

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

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

  Next, the entire procedure from the print request by the application unit 11 to the print processing in the printer 2 will be described.

  FIG. 8 is a flowchart showing an example of the 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). The print request includes, as one of the printing conditions, information on the paper type of the print medium used in the printer 2 (hereinafter referred to as paper type identification information).

  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 passed to the color converter 122, and the color converter 122 executes color conversion processing to convert the RGB pixel data into CMYK pixel data (step S13 in FIG. 8). In the color conversion processing, the color conversion unit 122 uses the forward pass LUT (first color conversion information), the return pass LUT (second color conversion information), and the adjustment table (α table) 127 for the return pass. The third LUT (third color conversion information) is generated, and processing appropriate to the paper type indicated by the paper type identification information is executed using the third LUT. The specific contents of the color conversion process will be described later.

  The print request including the generated CMYK pixel data is passed to the halftone processing unit 123, and the halftone processing unit 123 performs halftone processing on the CMYK pixel data to convert the CMYK pixel data into dot data ( Step S14 of 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 in which the print request is expressed by 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 the print process 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 discharging ink to 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 converter 122.

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

  Thereafter, the color conversion unit 122 obtains the difference (hereinafter, referred to as DIF) of the ink amount (color material amount) of the forward pass LUT 125 and the return pass LUT 126 (step S132 in FIG. 9). Specifically, the color conversion unit 122 stores (C, M, Y, K) for each of the grid points (R, G, B) described above (C, M, Y, K) (hereinafter, (C2, M2, (C, M, Y, K) (hereinafter referred to as (C1, M1, Y1, K1)) stored in the forward LUT 125 from the values (color data) of each color of Y2, K2)) Calculate the value obtained by subtracting the values of the corresponding colors. 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 converter 122 refers to the α table 127 to obtain 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 sheet type of the sheet 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 path 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 ink amount between the forward LUT 125 and the backward LUT 126 in the forward LUT 125 at a ratio proportional to the value of the acquired coefficient α. Do.

Specifically, (C, M, Y, K) (hereinafter referred to as (C3, M3, Y3, K3)) corresponding to grid points (R, G, B) of the third color conversion information is For each grid point, it is determined by the following equation.
C3 = C1 + α × ΔC
M3 = M1 + α × ΔM
Y3 = Y1 + α × ΔY
K3 = K1 + α × ΔK
The grid points (R, G, B) are the same in the forward LUT 125, the backward LUT 126, and the third LUT.

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

  Thus, for the return pass printing, a color conversion table (third LUT) adjusted so as to minimize the color difference in the forward pass printing and the return pass printing is used according to the paper type used.

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

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

  In addition, a third LUT corresponding to each paper type may be generated and stored in advance, and the third LUT may be used at the time of color conversion processing.

  In the printing system 100 according to the present embodiment, the color conversion information adjustment unit 212 of the printer 2 executes the process of determining the α value. However, the host computer 1 may perform the same process.

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

  Further, in the present embodiment, the color conversion table is adjusted according to the paper type of the printing conditions, but the color conversion table is adjusted according to other printing conditions such as temperature and humidity. It is also good.

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

  Also, since the patch image to be printed is a fill image, and the images to be compared are arranged adjacent to each other, the color difference can be easily understood and the user can make an accurate judgment.

  Further, by designating a color having a large color difference as the 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 reduce the color difference between forward printing and return printing.

  In addition, since color conversion tables for forward pass printing or return pass printing properly adjusted by the coefficient α for each printing condition are used in color conversion processing at the time of printing, color difference between forward pass printing and return pass printing under each printing condition Can be kept small.

  Although the color conversion processing from the RGB color space to the CMYK color space is described in the present embodiment, the present invention can be applied to color conversion processing from different color spaces.

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

  Reference Signs List 1 host computer 2 printer 11 application 12 printer driver 21 controller 22 print mechanism 23 print unit 100 print system 121 render unit 122 color converter 123 halftone processor 124 command Generation unit, 125 forward LUT, 126 return LUT, 127 adjustment table, 211 print control unit, 212 color conversion information adjustment unit, 221 main scan unit, 222 sub scan unit, 223 carriage motor, 224 carriage, 225 print head, 226 paper feed motor, 227 nozzles, 228 nozzle rows, 229 print media (paper)

Claims (8)

A printing unit that performs bidirectional printing on a print medium;
The printing unit includes: 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 An adjustment unit that makes the second type print medium printable in a contrastable 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. In claim 1,
The printing apparatus according to claim 1, 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
A 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 to 3,
The adjustment unit is
Adjusting second direction color conversion information for the second type print medium based on a predetermined coefficient;
The plurality of second direction print images using the plurality of second direction color conversion information for the plurality of second type print media adjusted based on each of the plurality of values of the predetermined coefficient are respectively the first direction A printing apparatus characterized by being printed in pairs with a print image. In claim 4,
The adjustment unit acquires identification information of one second direction print image input corresponding to the printing of the plurality of second direction print images, and the second identified by the acquired identification information A printing apparatus, which stores the value of the predetermined coefficient corresponding to a direction print image. In claim 5,
The printing unit is
At the time of 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 the second direction printing, printing is performed based on the 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 Printing a first direction print image using first direction color conversion information for a first type print medium;
Generating second direction color conversion information for a second type print medium, wherein second direction color conversion information for the first type print medium is adjusted;
A printing method comprising: printing a second direction print image using second direction color conversion information for the second type print medium so as to be contrastable with the first direction print image. A printing system comprising a host device and a printing device, the printing system comprising:
The printing device is
A print unit that performs bidirectional printing on a print medium based on image data generated by the host device;
The printing unit includes: 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 An adjustment unit that makes the second type print medium printable in a contrastable manner;
The host device is
The image data of the first direction is generated using the first direction color conversion information for the first type print medium, and the second adjusted using the value of the predetermined coefficient determined based on the printing by the adjusting unit. A driver unit that generates the image data in a second direction using second direction color conversion information for a seed print medium;
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.

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