JP2017148943A - Print control device, print control method and computer program therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress periodical unevenness in dot density in a raster line.SOLUTION: A print control device for controlling a printer having a nozzle array in which a plurality of nozzles are arrayed in the first direction and performing a pass for changing a ratio of dots with a prescribed periodic width in the second direction intersecting the first direction, includes: a printing instruction unit which causes the printer to print a test pattern in which a plurality of raster lines formed of dot lines arrayed in the second direction are arrayed in the first direction so that the length in the second direction of the test pattern becomes equal to or greater than a prescribed periodic width; a density acquisition unit which acquires density of dots for each prescribed interval along the second direction in each raster line obtained on the basis of photographed image data of the printed test pattern; and a correction value calculation unit which calculates a density correction value for each prescribed interval of each raster line on the basis of the acquired density of dots.SELECTED DRAWING: Figure 1

Description

  The present invention relates to control of a printing apparatus.

  Printing that forms an image consisting of a large number of dots on a print medium by moving a print head having a large number of nozzles for ejecting ink in the main scan direction and transporting the print medium in a transport direction that intersects the main scan direction The device is known. In this printing apparatus, the ink droplet landing position deviates from the planned position for reasons such as variations in the ink discharge amount for each nozzle and variations in the flying direction of the ink droplets, and the density of the streaks along the main scanning direction in the printed image is increased. (Banding) may appear. Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique for suppressing the occurrence of such banding, in which a correction pattern is printed and a dot density based on a position between adjacent dot rows before and after the conveyance direction in the obtained print image. Is detected, and a correction value of the dot row is calculated according to the detected dot density, and normal printing is performed by applying the correction value.

  In such a printing apparatus, when a print image is formed by ejecting ink both in the forward movement and in the backward movement when the print head reciprocates in the main scanning direction, In some cases, dots to be formed during the backward movement are determined by a mask prepared in advance. Such a mask is configured such that dot formation or non-formation is complementary to each other during forward movement and backward movement in an area having a certain number of pixels in each of the main scanning direction and the conveyance direction. By using such a mask to determine the dot formation pattern at the time of forward movement and at the time of backward movement and applying the mask on the print medium a plurality of times, the average density is obtained when viewed as the entire print medium.

JP 2005-246937 A

  By repeatedly applying such a mask to the image to be printed along the main scanning direction, uneven dot density for each width of the mask may occur in the raster line in the main scanning direction on the print medium. . However, when such density unevenness correction is performed using the technique disclosed in Patent Document 1, the correction value is based on the dot density based on the position between adjacent dot rows before and after in the transport direction. Therefore, it is difficult to obtain a correction value corresponding to density unevenness appearing in the main scanning direction. Such a problem is not limited to ink but is common to printing apparatuses that discharge other arbitrary liquids. Further, the present invention is not limited to the case where the dot density unevenness occurs in the raster line due to the application of the mask, but is common to the case where the dot density unevenness occurs in the raster line for any other reason. Therefore, even in such a printing apparatus, there is a demand for a technique for suppressing periodic dot density unevenness in a raster line.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one embodiment of the present invention, a print control apparatus is provided. This printing control apparatus has a nozzle row in which a plurality of nozzles are arranged in a first direction, and performs a pass in which a dot ratio changes with a predetermined period width in a second direction that intersects the first direction. A test pattern in which a plurality of raster lines composed of dot rows arranged in the second direction are arranged in the first direction, and the length of the test pattern in the second direction is the predetermined period. A print instructing unit that causes the printing apparatus to print to be equal to or larger than a width; dots at predetermined intervals along the second direction in each raster line obtained based on the captured image data of the printed test pattern A density acquisition unit that acquires the density of each of the raster lines, and a correction value calculation unit that calculates a density correction value for each predetermined interval of each raster line based on the acquired density of the dots.
According to the printing control apparatus of this aspect, the dot density at predetermined intervals is acquired for each period width of the change in the dot ratio along the second direction in each raster line of the printed test pattern, and the dot Since the density correction value of each raster line is calculated based on the density, the density correction is performed using the density correction value, thereby suppressing the occurrence of periodic dot density unevenness in the raster line.

  (2) In the printing control apparatus according to the above aspect, the predetermined interval may be narrower than the predetermined period width. According to the printing control apparatus of this aspect, since the dot density is acquired at an interval narrower than the period width of the change in the dot ratio along the second direction in each raster line of the printed test pattern, the density correction value Can be obtained more accurately. For this reason, it is possible to accurately correct the density by using such a density correction value.

  (3) In the printing control apparatus according to the above aspect, the printing apparatus may include an imaging unit that captures the test pattern and obtains the captured image data. According to the printing control apparatus of this aspect, since the printing apparatus includes the imaging unit, it is possible to acquire the captured image data of the printed test pattern in parallel with the printing of the test pattern, thereby reducing the density correction value acquisition processing time. it can.

  (4) In the printing control apparatus according to the above aspect, the printing apparatus may further include a density detection unit that obtains the density of the dots in each raster line based on the captured image data. According to the printing control apparatus of this aspect, since the printing apparatus includes the density detection unit, the dot density in each raster line is obtained based on the captured image data in parallel with the acquisition of the captured image data of the printed test pattern. Therefore, the density correction value acquisition processing time can be shortened.

  (5) In the printing control apparatus according to the above aspect, the printing apparatus includes a print head having the nozzle row, and a carriage configured to be movable in the second direction with the print head attached. And when the carriage reciprocates along the second direction, the liquid is ejected onto the same area of the print medium in both the forward path and the backward path to print an image; Dots to be respectively formed in the return path are determined by a predetermined mask; the predetermined period width is equal to a width of the predetermined mask along the second direction when the predetermined mask is applied Also good. According to the printing control apparatus of this aspect, by repeatedly applying a predetermined mask in the second direction for determining whether dots are formed during forward movement or double movement of the carriage, the raster line can be Even when there is a possibility of uneven dot density, the occurrence of such uneven density can be suppressed.

  (6) In the printing control apparatus according to the above aspect, the density correction value calculated by the correction value calculation unit is used when the printing apparatus prints another image different from the test pattern; May print the other image after the density is corrected by the density correction value. According to the printing control apparatus of this aspect, the print data of another image after the density is corrected using the density correction value is generated and printed, so that the density unevenness in the raster line in the other image is generated. Can be suppressed.

  (7) The print control apparatus according to the above aspect may further include a storage instruction unit that causes the printing apparatus to store the density correction value calculated by the correction value calculation unit. According to the printing control apparatus of this aspect, since the density correction value calculated by the correction value calculation unit is stored in the printing apparatus, in the configuration in which the printing apparatus is controlled by another printing control apparatus, the other printing control apparatus However, the density correction value can be easily obtained from such a printing apparatus, and the density correction value can be referred to when another image is printed by such a printing apparatus.

  The present invention can be realized in various forms. For example, the present invention can be realized in the form of a printing apparatus, a printing method, a printing control method, a computer program for realizing these apparatuses and methods, a recording medium on which such a computer program is recorded, and the like. Further, the present invention is not limited to the print control apparatus, and can be realized as a print control apparatus that controls an arbitrary liquid ejecting apparatus.

  A plurality of constituent elements of each aspect of the present invention described above are not indispensable, and some or all of the effects described in the present specification are to be solved to solve part or all of the above-described problems. In order to achieve the above, it is possible to appropriately change, delete, replace with another new component, and partially delete the limited contents of some of the plurality of components. In order to solve part or all of the above-described problems or to achieve part or all of the effects described in this specification, technical features included in one embodiment of the present invention described above. A part or all of the technical features included in the other aspects of the present invention described above may be combined to form an independent form of the present invention.

1 is a block diagram illustrating a configuration of a print control apparatus as an embodiment of the present invention. 2 is a block diagram illustrating a schematic configuration of a printing apparatus 200. FIG. 4 is an explanatory diagram illustrating a configuration of a nozzle row of a print head 90. FIG. It is explanatory drawing which shows the position of the nozzle row | line | column 95 in two main scanning passes in this embodiment, and the formation area of the dot in the position. It is a flowchart which shows the process sequence of a printing process. It is explanatory drawing which shows an example of the detailed structure of mask MS. It is explanatory drawing which shows typically a mode that mask MS is applied in a printing data output process (step S120). It is a flowchart which shows the procedure of the density | concentration correction value acquisition process in this embodiment. FIG. 6 is an explanatory diagram showing a relationship between raster line density and density correction value 37; It is explanatory drawing which shows an example of the dot group formed when the density correction process in this embodiment is not performed. It is explanatory drawing which shows an example of the dot group formed when the density correction process in this embodiment is performed.

A. Embodiment:
A1. Configuration of print control device:
FIG. 1 is a block diagram showing the configuration of a print control apparatus as an embodiment of the present invention. The print control apparatus 100 is used to set a density correction value 37 to be described later with respect to the printing apparatus 200 before shipment. In the present embodiment, the print control apparatus 100 is configured by a computer and is installed on an inspection line in a factory. Although details will be described later, the print control apparatus 100 having the same configuration as the print control apparatus 100 is also installed in the user's home, and the print control apparatus 100 after the shipment is controlled by the print control apparatus 100 to perform normal printing. . In FIG. 1, the configuration of the print control apparatus 100 installed at the user's home is indicated by a broken line.

  In the print control apparatus 100, an arbitrary operating system is operating. The operating system incorporates a video driver 22, a printer driver 30, and an inspection program 40. In addition, a display 111, a keyboard 112, a mouse 113, and a printing apparatus 200 are connected to the printing control apparatus 100 through a predetermined interface. In this embodiment, the predetermined interface is USB.

  The inspection program 40 includes a density acquisition unit 41 and a correction value calculation unit 42. When the inspection program 40 is executed, the test pattern TP is printed by the printing apparatus 200 via the printer driver 30, and the density correction value 37 is acquired based on the printed test pattern TP. The density acquisition unit 41 acquires the dot density obtained from the captured image data of the printed test pattern TP. The correction value calculation unit 42 calculates a density correction value 37 in a density correction value acquisition process described later, and stores it in the memory 311.

  The printer driver 30 includes a resolution conversion module 31, a color conversion module 32, a halftone module 34, and a print data output module 35. As will be described later, the printer driver 30 of the print control apparatus 100 (not shown) installed at the user's home includes the above-described modules, the resolution conversion module 31, the color conversion module 32, the halftone module 34, and the print data output module 35. In addition, a density correction module 33 is incorporated. Note that the density correction module 33 may also be incorporated in the print control apparatus 100 installed in the inspection line in the factory.

  The resolution conversion module 31 has a function of converting the resolution of the input image into the print resolution. The color conversion module 32 has a function of converting an input image color (RGB) into an ink color (CMYK). The color conversion module 32 performs the color conversion with reference to a color conversion table 36 prepared in advance. The halftone module 34 performs a so-called halftone process in which the input gradation value is reduced to the number of output gradations that can be expressed by dot formation. In the present embodiment, the halftone process is executed by a so-called dither method. The halftone module 34 refers to a dither matrix 38 for determining the dot recording rate for halftone processing. The print data output module 35 rearranges the halftone data generated by the halftone module 34 into dot data, generates print data including a print control command, and transmits the print data to the printing apparatus 200. When the halftone data is rearranged into dot data, a mask MS is applied to determine whether a dot of each pixel is formed during forward movement or double movement of the carriage 230 described later.

  The printer driver 30 corresponds to a program for realizing a function for generating print data. The printer driver 30 is supplied in a form recorded on a computer-readable recording medium. Examples of such recording media include CD-ROMs, flexible disks, magneto-optical disks, IC cards, ROM cartridges, punch cards, printed matter printed with codes such as barcodes, computer internal storage devices (RAM, ROM, etc.) A variety of computer-readable media, such as memory) and external storage devices.

A2. Configuration of printing device:
FIG. 2 is a block diagram illustrating a schematic configuration of the printing apparatus 200. In the present embodiment, the printing apparatus 200 is configured as an ink jet printer that ejects four color inks, specifically, C (cyan), M (magenta), Y (yellow), and K (black) inks. Yes. The printing apparatus 200 includes a supply unit 210, a transport unit 220, a carriage moving unit 240, a carriage 230, and a control unit 300. The printing apparatus 200 controls the supply unit 210, the transport unit 220, the carriage moving unit 240, and the carriage 230 based on the print data input from the print control apparatus 100, and prints the test pattern TP on the print medium P. In FIG. 2, the carriage 230 reciprocates along the main scanning direction D1, and the print medium P is conveyed from upstream to downstream in the sub-scanning direction D2. The sub-scanning direction D2 is a direction that intersects the main scanning direction D1, and is a direction that is orthogonal to the main scanning direction in the present embodiment.

  The supply unit 210 supplies the print medium P to the transport unit 220 in response to a control signal from the control unit 300. In the present embodiment, although not shown, the supply unit 210 includes a roll body around which the printing medium P is wound, a roll drive motor, and a roll drive wheel train. For example, instead of the roll body, a print medium P that is stacked and accommodated in a paper tray may be used.

  The transport unit 220 drives the transport roller 221 in response to a control signal from the control unit 300, thereby causing the print medium P supplied by the supply unit 210 from the upstream side to the downstream side along the sub-scanning direction D2. Transport. Although not shown, the transport unit 220 is provided with sensors such as a feed detection sensor that detects the transport amount of the print medium P and a front end detection sensor that detects the front end position of the print medium P. The control unit 300 refers to signals from these sensors and controls the transport unit 220.

  The carriage moving unit 240 reciprocates the carriage 230 along the main scanning direction D1 in response to a control signal from the control unit 300. The carriage moving unit 240 includes a carriage guide shaft 241 and a carriage motor (not shown). The carriage guide shaft 241 is disposed along the main scanning direction D1, and both ends are fixed to the casing of the printing apparatus 200. The carriage 230 is attached to the carriage guide shaft 241 so as to reciprocate in the main scanning direction D1. When the carriage moving unit 240 drives the carriage motor in response to a control signal from the control unit 300, the carriage 230 reciprocates along the carriage guide shaft 241. Although not shown, the carriage moving unit 240 includes a carriage position sensor that detects the position of the carriage 230. The control unit 300 refers to the signal from the carriage position sensor and controls the movement amount of the carriage 230.

  The carriage 230 includes a printing unit 231 and an imaging device 232. The printing unit 231 prints an image by ejecting ink droplets onto the printing medium P in accordance with a control signal from the control unit 300. The printing unit 231 includes a print head 90 to be described later, and a plurality of nozzles that eject liquid are provided on the surface of the print head 90 that faces the print medium P. Details of the configuration of the print head 90 and the dot formation method will be described later. In the present embodiment, the printing apparatus 200 is a so-called off-carriage type printer, and an ink cartridge is provided at a site different from the carriage 230, and ink is supplied from the ink cartridge to the printing unit 231.

  The imaging device 232 captures an image when the carriage 230 moves in the main scanning direction D1 in accordance with a control signal from the control unit 300. The imaging device 232 is disposed on the surface of the carriage 230 that faces the print medium P, and as illustrated in FIG. 2, the imaging device 232 is disposed downstream of the printing unit 231 in the sub-scanning direction D2 in the carriage 230. Thereby, when the printing medium P is conveyed downstream by the conveying unit 220, the imaging device 232 can image an image printed on the printing medium P, that is, a dot group formed on the printing medium P. . In the present embodiment, the imaging device 232 is configured by a line sensor including a large number of sensors arranged in the main scanning direction D1.

  The control unit 300 includes an input / output interface (I / F) 310, a memory 311, a unit control circuit 312, and a CPU 320. The input / output interface 310 outputs print data input from the print control apparatus 100 to the CPU 320. The memory 311 stores a control program for controlling the operation of the printing apparatus 200. The unit control circuit 312 includes control circuits that respectively control the supply unit 210, the transport unit 220, and the carriage movement unit 240 described above, and controls the operation of each unit according to a control signal from the CPU 320.

  The CPU 320 functions as a scanning control unit 321, a print instruction unit 322, and a density detection unit 323 by developing and executing a control program stored in the memory 311.

  The scanning control unit 321 controls the main scanning operation of the carriage 230 and the conveying operation of the print medium P. Specifically, the scanning control unit 321 transmits a control signal to the unit control circuit 312 in order to control the main scanning operation of the carriage 230, thereby driving the carriage motor of the carriage moving unit 240 and moving the carriage 230. Move to the print start position in the main scanning direction D1. In addition, the scanning control unit 321 transmits a control signal to the unit control circuit 312 to control the transport operation of the print medium P, thereby driving the roll drive motor of the supply unit 210 and transporting the print medium P to the transport unit. 220. In addition, by transmitting a control signal to the unit control circuit 312, the transport motor of the transport unit 220 is driven to transport the print medium P to the print start position in the sub-scanning direction D2.

  The print instruction unit 322 generates a control signal for driving the printing unit 231 based on the print data input from the input / output interface (I / F) 310 and transmits the control signal to the printing unit 231 via the unit control circuit 312. The unit control circuit 312 controls the carriage moving unit 240 in accordance with a control signal from the print instruction unit 322, so that the printing unit 231 performs printing. More specifically, the dot formation processing of the printing medium P by the printing unit 231 according to the control signal from the printing instruction unit 322 and the printing medium P by the transport unit 220 according to the control signal from the scanning control unit 321. The transport process in the sub-scanning direction D2 and the movement process in the main scanning direction D1 of the carriage 230 by the carriage moving unit 240 according to the control signal from the scanning control unit 321 are executed, so that the print medium P The image is printed.

  The density detection unit 323 controls the imaging device 232 to execute imaging, and detects the density of dots in each raster line based on image data obtained by the imaging device 232 imaging the print medium P in the imaging area.

  In the above-described embodiment, the printing apparatus 200 corresponds to a subordinate concept of the printing apparatus in the claims. Further, ink is imaged in the subordinate concept of the liquid in the claims, the main scanning direction D1 is in the subordinate concept in the second direction in the claims, and the sub-scanning direction D2 is in the subordinate concept in the first direction in the claims. The device 232 corresponds to a subordinate concept of the imaging unit in the claims.

A3. Detailed configuration of printing section:
FIG. 3 is an explanatory diagram showing the configuration of the nozzle array of the print head 90. FIG. 3 shows a surface of the print head 90 that faces the print medium P. The print head 90 includes a first print head 90a and a second print head 90b. The first print head 90a and the second print head 90b each include a nozzle row 91 for each ink color. Each nozzle row 91 includes a plurality of nozzles 92 arranged at a predetermined interval (hereinafter referred to as nozzle pitch) dp along the sub-scanning direction D2. The nozzles 92x at the end of the nozzle row 91 of the first print head 90a and the nozzles 92y at the end of the nozzle row 91 of the second print head 90b are sub-same as the predetermined interval dp in the nozzle row 91. It is shifted in the scanning direction D2.

  With such a configuration, the total nozzle row for one color of the first print head 90a and the second print head 90b has the number of nozzles twice the number of nozzles for one color of one print head. That is, the total nozzle row for one color of the first print head 90a and the second print head 90b is equivalent to the nozzle row 95 shown on the left side of FIG. In the present embodiment, it is assumed that dot formation for one color is performed using the nozzle row 95, and the nozzle pitch dp is equal to the pixel interval on the print medium P. The above-mentioned “pixel” refers to a unit region in which dots are formed on the print medium P. The nozzle pitch dp may be an integer multiple of the pixel interval on the print medium P. In addition, the print head 90 is configured by two of the first print head 90a and the second print head 90b, but may be configured by only one of the first print head 90a, for example. You may be comprised by N pieces (N is an integer greater than or equal to 3).

  FIG. 4 is an explanatory diagram showing the position of the nozzle row 95 and the dot formation region at that position in the two main scanning passes in this embodiment. FIG. 4 illustrates an example in which an image (solid image) in which dots are formed on all the pixels of the print medium P using one color ink is formed on the print medium P. In the present embodiment, each dot row (hereinafter referred to as “raster line”) along the main scanning direction D1 is formed by two main scanning passes. The main scanning pass is not limited to two times but may be N times (N is an integer of 2 or more). Here, “main scanning” means movement of the print head 90 in the main scanning direction D1 and ink ejection operation, and “main scanning pass” means at the time of one forward movement or backward movement. Refers to main scanning. As shown in FIG. 4, in the first main scanning pass and the second main scanning pass, the position of the nozzle row 95, more precisely, the relative position of the nozzle row 95 with respect to the print medium P is the first main scanning pass. Since the print medium P is transported downstream in the sub-scanning direction D2 after the scanning pass, the print medium P is shifted upstream in the sub-scanning direction D2 by a distance corresponding to ½ of the head height Hh. Here, the head height Hh refers to a distance represented by the number of nozzles in the nozzle row 95 × nozzle pitch dp.

  In the first main scanning pass, 50% of all the pixels in the region Q1 along the main scanning direction D1 through which the upper half of the nozzle row 95 of the print medium P passes, Dots are formed in 50% of all pixels in the region Q2 along the main scanning direction D1 through which half of the nozzles pass. In the second main scanning pass, in the printing medium P, dots are formed in the first pass among all the pixels in the region Q2 configured along the main scanning direction D1 through which the upper half nozzles of the nozzle row 95 pass. Dots are formed in the remaining 50% of the pixels that have not been formed and 50% of all the pixels in the region Q3 configured along the main scanning direction D1 through which the lower half of the nozzle row 95 passes. Is done. That is, in the region Q2, 50% of dots are formed in each of the first pass and the second pass, and a dot of 100% pixels is formed in total. In the third pass, dots are formed in the remaining 50% of the pixels in the region Q3 and 50% of the pixels in the next region Q4 (not shown). Whether or not dots are actually formed on each pixel of the print medium P is determined based on a mask described later.

A4. Printing process:
FIG. 5 is a flowchart showing the processing procedure of the printing process. The processing procedure of the printing process shown in FIG. 5 is a normal printing procedure performed at the user's home using the printing apparatus 200 after shipment. As described above, the print control apparatus 100 having the same configuration as the print control apparatus 100 shown in FIG. 1 is also installed in the user's home. Since the print control apparatus 100 installed in the user's home has the same configuration as the print control apparatus 100 installed in the factory, the same functional units will be described with the same reference numerals.

  As described above, the print control apparatus 100 installed in the user's home incorporates the application 20 shown in FIG. Further, the printer driver 30 incorporates a density correction module 33. The density correction module 33 has a function of correcting the print density for the purpose of suppressing banding. When correcting the print density, the density correction module 33 uses the density correction value 37 acquired (calculated) in a density correction value acquisition process described later.

  As shown in FIG. 5, when the user designates image data and issues a print instruction in the print control apparatus 100, a print process is executed. The resolution conversion module 31 performs resolution conversion processing on the designated image data (step S100). The image data to be processed includes image data generated by the application 20 and image data received from an input I / F (not shown). In this embodiment, red (R), green (G), blue ( This is image data having gradation values (0 to 255) composed of the color components of B). In step S <b> 100, the resolution conversion module 31 converts the resolution of the image data into a resolution for printing on the print medium P.

  The color conversion module 32 performs a color conversion process (step S105). Specifically, the color conversion module 32 refers to the color conversion table 36 and converts RGB data into 256-level CMYK data represented by the color space of the ink colors CMYK of the printing apparatus 200.

  The density correction module 33 executes density correction processing (step S110). Specifically, the density correction module 33 acquires the density correction value 37 via the connection interface (USB), and refers to the density correction value 37 and is adjacent to the raster line along the sub-scanning direction D2. Based on the density correction value 37 of the matching dot row, the density of the corresponding raster line is corrected. The density correction is performed by adjusting the amount of ink ejected from the nozzles. When the density is decreased, the ink ejection amount is decreased. When the density is increased, the ink ejection amount is increased.

  The halftone module 34 performs halftone processing (step S115). Specifically, the halftone module 34 uses the dither matrix 38 to convert the 256 gradation (stage) gradation values of the CMYK data into four gradation values that can be expressed by the printing apparatus 200. Specifically, data of 256 gradations is converted into 1-bit data indicating 2 gradations or 2-bit data indicating 4 gradations.

  The print data output module 35 executes a print data output process using the image data after the halftone process (step S120). Specifically, the print data output module 35 repeatedly applies the mask MS to the halftone processed image data to form each dot of each raster line in any of the two main scanning passes. Is determined, rasterization processing is executed based on the determination, and the processed data (print data) is output to the printing apparatus 200. Since this print data is subjected to density correction by applying a density correction value, density unevenness is suppressed in an image printed based on the print data.

A5. Detailed mask configuration:
FIG. 6 is an explanatory diagram showing an example of a detailed configuration of the mask MS. In the present embodiment, the mask MS has a rectangular shape. The size of the mask MS is smaller than the image to which the mask MS is applied in step S120, that is, the image represented by the image data after the halftone process of the test pattern TP. Therefore, as will be described later, the mask MS is repeatedly applied to the image represented by the image data along each of the main scanning direction D1 and the sub-scanning direction D2, and the first main scanning pass in each region. It is determined in which pass of the second main scanning pass the dot is formed. In FIG. 6, arrows indicating the main scanning direction D1 and the sub-scanning direction D2 are attached so that the positional relationship between the mask MS and the image when the mask MS is applied is clear.

  The mask MS is composed of a first mask MS1 assigned to the upper half nozzle group X of the nozzle row 95 and a second mask MS2 assigned to the lower half nozzle group Y. The first mask MS1 includes four regions (a first mask region Mu1, a second mask region Mm1, a third mask region Md1, a fourth mask) arranged in order from the left side to the right side in the main scanning direction D1. Mask region Mm1). The mask areas Mu1, Mm1, Md1, and Mm1 have the same size.

  In the present embodiment, in the first mask area Mu1, the ratio of the upper half nozzle group X in charge of dot formation in that area (hereinafter referred to as “dot ratio”) is set to 67%. Yes. The third mask region Md1 is set so that the dot ratio of the upper half nozzle group X in the region is 33%. Here, in the present embodiment, the dot ratio of the first mask area Mu1 and the dot ratio of the third mask area Md1 are set so that the average of each other is 50%. Each of the second and fourth mask regions Mm1 is a region in which the dot ratio of the upper half nozzle group X is set to 50%. Accordingly, the dot ratio of the first mask MS1 as a whole is set to be 50% on average.

  The second mask MS2 is such that the downstream boundary line along the sub-scanning direction D2 of each mask region of the first mask MS1 coincides with the upstream boundary line along its own sub-scanning direction D2. Has been placed. Similarly to the first mask MS1, the second mask MS2 includes four mask regions (fifth mask region Mu2, sixth mask region Mm2, seventh mask region Md2, eighth mask) arranged in the main scanning direction D1. Mask region Mm2). The dot ratio of the fifth mask region Mu2 is 33%. Further, the dot ratio of the sixth mask region Mm2 and the eighth mask region Mm2 is 50%. The dot ratio of the seventh mask region Md2 is 67%.

  By setting the dot ratio in each mask area as described above, the first mask MS1 and the second mask MS2 have a total dot ratio of 100% corresponding to (adjacent to) each area in the sub-scanning direction D2. And are set to be complementary to each other. Therefore, for example, in the fifth mask region Mu2, pixels in which dots are formed in the first mask region Mu1 are pixels in which dots are not formed in the fifth mask region Mu2, and dots are formed in the first mask region Mu1. The pixels that are not formed are set to be the pixels on which dots are formed in the fifth mask region Mu2. The same applies to other regions.

  FIG. 7 is an explanatory diagram schematically showing how the mask MS is applied in the print data output process (step S120). The mask MS in which the dot ratio is set as described above is repeatedly applied in the main scanning direction D1 and the sub-scanning direction D2 to the image F1 represented by the image data after the halftone process, so that the dots in each region are It is determined which of the first main scanning pass and the second main scanning pass is used.

  As shown in FIG. 7, when the mask MS is regularly and repeatedly applied, density unevenness due to the dot ratio set in each area constituting the mask MS is caused in each raster line (along the main scanning direction D1). Can occur stepwise and periodically. More specifically, dark portions and thin portions can be generated periodically and alternately for each width NHw of the mask MS. However, by performing the above-described density correction process (step S110) using the density correction value 37 acquired by the print control apparatus 100 of the present embodiment, the occurrence of uneven dot density in the raster line is suppressed. Is done. Hereinafter, the process of acquiring the density correction value 37 will be described with reference to FIGS.

A6. Density correction value acquisition processing:
FIG. 8 is a flowchart showing the procedure of density correction value acquisition processing in the present embodiment. When the print control apparatus 100 is connected to the printing apparatus 200 before shipment in the factory and the operator selects an operation menu for executing the density correction value acquisition process, the density correction value acquisition process is executed in the print control apparatus 100. The

  The inspection program 40 instructs the printing apparatus 200 via the printer driver 30 to print the test pattern TP with the printing apparatus 200, and causes the printing apparatus 200 to print the test pattern TP (step S205). In step S205, processing other than step S110 is executed from the printing processing shown in FIG. 5 described above. In the present embodiment, the test pattern TP is arranged in such a manner that regions of each color including only dots of each color of C (cyan), M (magenta), Y (yellow), and K (black) are arranged along the main scanning direction D1. It is the image which was made the strip | belt shape. As shown in FIGS. 6 and 7, in the printing apparatus 200 of the present embodiment, the mask MS is repeatedly applied in the main scanning direction D1, so that the density variation with the periodic width NHw along the main scanning direction D1 on the print medium P. Can occur. Accordingly, in order to accurately calculate the density correction value 37, when printing the test pattern TP, the length of the print region in the main scanning direction D1 is printed so as to be at least the periodic width NHw.

  As illustrated in FIG. 8, the density detection unit 323 controls the imaging device 232 to image the printed test pattern TP, and obtains captured image data obtained (step S210). In the present embodiment, the imaging device 232 is controlled to image the test pattern TP for each period width NHw.

  The density detector 323 detects the dot density at predetermined intervals along the main scanning direction D1 in each raster line from the captured image data acquired in step S210 (step S215). The density detection unit 323 acquires the dot density for each dot in the present embodiment at predetermined intervals along the main scanning direction D1 in each raster line based on the luminance of the captured image data. Note that the predetermined interval is not limited to one dot, and may be two dots, or may be an interval that is narrower than the periodic width NHw as long as it does not exceed the periodic width NHw, and an arbitrary value may be set. The acquired dot density is stored in the memory 311 for each cycle width NHw of each raster line.

  The density acquisition unit 41 of the printing control apparatus 100 acquires the dot density stored in the memory 311 of the printing apparatus 200 (step S220).

  The correction value calculation unit 42 of the print control apparatus 100 calculates the density correction value 37 for each predetermined interval of each raster line based on the dot density acquired in step S220 (step S225). In the present embodiment, the density correction value 37 is obtained by applying a known technique (for example, a technique described in JP-A-2005-246937). Briefly, the average value of the dot density for each period width NHw in each raster line obtained in step S220 is calculated, and the value obtained by dividing the deviation between the dot density of each dot and the average value by the average value is The dot density correction value is determined. A set of density correction values for all dots is calculated as the density correction value 37. The correction value calculation unit 42 stores the acquired density correction value 37 in the memory 311 for each acquired region. In the present embodiment, the storage instruction unit in the claims is configured by the correction value calculation unit 42.

  FIG. 9 is an explanatory diagram showing the relationship between the density of the raster line and the density correction value 37. In FIG. 9, for convenience of explanation, an X axis and a Y axis that are orthogonal to each other are attached. The X axis is set parallel to the main scanning direction D1. The direction from the right to the left in the drawing corresponds to the + X direction. The Y axis is set parallel to the sub-scanning direction D2. The direction from upstream to downstream corresponds to the + Y direction.

  According to the method for determining the density correction value 37 described above, the density correction value is positive when the density between adjacent dots in each raster line is low, and the density correction value is negative when the density is high. In the example shown in FIG. 9, along the main scanning direction D1, each dot constituting the rn row is formed at a position closer to the −X side than the normal position. It is assumed that the other dot rows are formed at regular positions. In this case, since the dot is formed at the regular position in each of the r (n-2) row and the r (n-1) row, the r (n-2) row and the r (n-1) row are The density correction value 37 corresponding to the density of the dots in between is set to zero. In the r (n−1) column and the rn column, since the rn column is closer to the r (n + 1) column than the normal position, dots are formed, and therefore the r (n−1) column and the rn column are between Since the dot density is light, the density correction value 37 corresponding to the dot density between the r (n-1) and rn lines is set to a positive value. In the rn row and the r (n + 1) row, since the rn row is closer to the r (n + 1) row than the normal position, the dot density between the rn row and the r (n + 1) row is Since it becomes darker, the density correction value 37 corresponding to the density of dots between the rn and r (n + 1) columns is set to minus. In the r (n + 1) row and the r (n + 2) row, dots are formed at regular positions, respectively, so that the density correction value according to the dot density between the r (n + 1) row and the r (n + 2) row. 37 is set to zero. The dot density between the dot rows corresponds to the density between the dots in each raster line, and corresponds to the subordinate concept of the dot density in the claims.

  When density correction is performed using a density correction value 37, which will be described later, when the density correction value 37 is positive, it acts to increase the density of the raster line, and when the density correction value 37 is negative. This acts to reduce the density of the raster line.

  FIG. 10 is an explanatory diagram showing an example of a dot group formed when the density correction process in this embodiment is not executed. FIG. 11 is an explanatory diagram illustrating an example of a dot group formed when the density correction process according to the present embodiment is executed. 10 and 11, the X axis and the Y axis are attached as in FIG. 9. FIG. 11 shows a dot group formed when the same image data as in FIG. 10 is designated and the printing process is executed.

  In the example of FIG. 10, as in the example shown in FIG. 9, the rn column and the r (n + 1) column along the sub-scanning direction D <b> 2 are on the −X direction side of the normal position compared to the other columns. Dots are formed close to (r (n + 1) column side). Thereby, in the print image, the print density is relatively high in the rn column and the r (n + 1) column, and the print density is relatively low in the r (n-1) column and the rn column. Here, when printing is performed with the density correction processing of the present embodiment, the density of the rn and r (n + 1) columns is decreased, and the density of the r (n-1) and rn columns is increased. To be corrected. Specifically, as shown in FIG. 11, the dot dt1 is not formed so as to reduce the density of the r (n + 1) column, and the dot dt2 is added so as to increase the density of the r (n-1) column. Formed. It should be noted that the area where the dot dt1 is not formed and the area where the dot dt2 is added are separated from each other in a dot row (dot arrangement in the Y-axis direction), and adjustment of dot formation and non-formation within the same dot row Therefore, the occurrence of density unevenness is suppressed.

  According to the printing control apparatus of the present embodiment described above, unevenness in dot density occurs for each width of the mask MS (period width NHw) in the raster line by repeatedly applying the mask MS in the main scanning direction D1. Even when there is a possibility of obtaining, the density of dots at predetermined intervals is obtained for each periodic width NHw of density fluctuation along the main scanning direction D1 in each raster line from the captured image data of the printed test pattern TP. Since the density correction value 37 of each raster line is calculated based on the density of the dots, the print data after the density is corrected using the density correction value 37 is printed to periodically Generation of uneven dot density can be suppressed. Further, since the dot density is acquired at an interval narrower than the periodic width NHw of density fluctuation, the density correction value 37 can be acquired with higher accuracy. Further, since the printing apparatus includes the imaging unit and the density detection unit, in parallel with the printing of the test pattern, the captured image data of the printed test pattern is obtained and the dot density in each raster line is obtained based on the captured image data. Therefore, the density correction value acquisition processing time can be shortened.

B. Variations:
B1. Modification 1:
In the above embodiment, the mask MS has a rectangular shape, but the present invention is not limited to this. For example, an arbitrary shape such as a triangle or a hexagon may be used. Even in such a configuration, if the mask MS is repeatedly arranged in the main scanning direction D1, the dot ratio of each mask region aligned in the main scanning direction D1 can be changed stepwise and periodically. The same effect as the embodiment is achieved.

B2. Modification 2:
In the above embodiment, the density correction processing can suppress the uneven dot density in the raster line due to the application of the mask MS, but the present invention is not limited to this. The same effect can be obtained for dot density unevenness along the main scanning direction D1 or the sub-scanning direction D2 caused by any other reason.

B3. Modification 3:
In the above embodiment, the print control apparatus 100 and the printing apparatus 200 are connected via USB, but the present invention is not limited to this. It may be a network connection. The print control apparatus 100 may be connected to an external device such as a scanner or a USB memory. Also in these structures, there exists an effect similar to embodiment.

B4. Modification 4:
In the above embodiment, the printing apparatus 200 is an off-carriage type printer, but the present invention is not limited to this. For example, an on-carriage type printer may be used, and an ink tank may be used instead of the ink cartridge. Further, the liquid ejected from the nozzle may be a liquid other than ink. For example,
(1) Color materials used in the manufacture of color filters for image display devices such as liquid crystal displays (2) Used for forming electrodes such as organic EL (Electro Luminescence) displays and surface emission displays (FED) Electrode material (3) Liquid containing biological organic material used for biochip production (4) Sample as precision pipette (5) Lubricating oil (6) Resin liquid (7) Micro hemispherical lens (optical lens) used for optical communication element etc. ) Etc. Transparent resin liquid such as UV curable resin liquid (8) Liquid that jets acidic or alkaline etching liquid to etch the substrate etc. (9) Any other small amount of liquid droplets May be. Also in these structures, there exists an effect similar to embodiment.

B5. Modification 5:
In the above embodiment, the imaging device 232 images the test pattern TP when the print medium P is conveyed in the sub-scanning direction D2, but the present invention is not limited to this. For example, when the test pattern TP does not fall within the imaging area of the imaging device 232, imaging may be performed in multiple steps. Even in such a configuration, it is possible to obtain the density correction value 37 for the dots in the area included in the captured image data from the imaging data obtained each time, and to obtain the density correction value 37 by combining them. There is an effect similar to the form.

B6. Modification 6:
In the above embodiment, the carriage 230 includes the imaging device 232, but the imaging device 232 may be omitted. In this case, the operator causes the scanner or the like to read the print result of the test pattern TP, and obtains the captured image data and the data indicating the dot density from the scanner to the print control apparatus 100 via a predetermined recording medium or network. You may send it. With such a configuration, the manufacturing cost of the printing apparatus 200 can be kept low.

B7. Modification 7:
In the above embodiment, the acquired (calculated) density correction value 37 is stored in the memory 311 of the printing apparatus 200, but the present invention is not limited to this. For example, it may be stored in the memory of the print control apparatus 100. Further, a RIP (raster image processor) may be added to the printing apparatus 200 and stored in the RIP. The RIP may be configured as hardware connected between the printing apparatus 200 and any other external device. In this case, the print data may be generated by the RIP, or the test pattern TP may be stored in the RIP. Even in such a configuration, the same effects as in the embodiment can be obtained. In the case where the printing apparatus 200 has a slot for storing a recording medium such as a memory card, the density correction value 37 may be stored in the recording medium stored in the slot.

B8. Modification 8:
In the above embodiment, the resolution of the imaging device 232 is 1200 dpi, and the number of imaging pixels of the imaging device 232 is 1920 × 1080 (pixels), but is not limited thereto. The imaging device 232 may be detachably mounted on the carriage 230. Even in such a configuration, the same effects as in the embodiment can be obtained.

B9. Modification 9:
In the above embodiment, the printing unit 231 forms a print image during forward movement and backward movement in the main scanning direction D1, but the present invention is not limited to this. For example, a printing apparatus that forms a print image in a main scanning pass during forward movement and does not form a print image (dot) in a main scanning pass during backward movement may be used. Even in such a configuration, since a change in density can occur for each width (period width NHw) of the mask MS along the main scanning direction D1 in the print medium P, the density correction process according to the embodiment is performed. There is an effect similar to the form.

B10. Modification 10:
In the above embodiment, the density correction acquisition process is executed in the factory before the printing apparatus 200 is shipped, but the present invention is not limited to this. For example, it may be executed at the user's home. In this configuration, the inspection program 40 may be incorporated in the printer driver 30 in advance as a utility function of the printer driver 30. Even in such a configuration, the same effect as the embodiment can be obtained.

B11. Modification 11:
In the above-described embodiment, another device may have at least part of the functions of the print control apparatus 100. For example, the printing apparatus 200 may include the correction value calculation unit 42. The printing apparatus 200 may have all the functions of the printing control apparatus 100. Conversely, the print control apparatus 100 may have a part of the functions of the printing apparatus 200. For example, the print control apparatus 100 may include the print instruction unit 322. Even in these configurations, the same effects as those of the embodiment can be obtained.

B12. Modification 12:
In the embodiment and the modification, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. Good. In addition, when part or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, a hard disk, etc. It also includes an external storage device fixed to the computer. That is, the “computer-readable recording medium” has a broad meaning including an arbitrary recording medium in which data can be fixed instead of temporarily.

  The present invention is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit of the present invention. For example, the technical features in the embodiments and the modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

    DESCRIPTION OF SYMBOLS 20 ... Application, 22 ... Video driver, 30 ... Printer driver, 31 ... Resolution conversion module, 32 ... Color conversion module, 33 ... Density correction module, 34 ... Halftone module, 35 ... Print data output module, 36 ... Color conversion table , 37 ... density correction value, 38 ... dither matrix, 40 ... inspection program, 41 ... density acquisition unit, 42 ... correction value calculation unit, 90 ... print head, 90a ... first print head, 90b ... second print head 91 ... Nozzle row, 92 ... Nozzle, 92x ... Nozzle, 92y ... Nozzle, 95 ... Nozzle row, 100 ... Print control device, 111 ... Display, 112 ... Keyboard, 113 ... Mouse, 200 ... Printing device, 210 ... Supply unit , 220 ... transport unit, 221 ... transport roller, 230 ... carrier 231 ... Printing unit, 232 ... Imaging device, 240 ... Carriage moving unit, 241 ... Carriage guide shaft, 300 ... Control unit, 310 ... Input / output interface, 311 ... Memory, 312 ... Unit control circuit, 320 ... CPU, 321 ... Scanning control unit, 322 ... Printing instruction unit, 323 ... Density detection unit, CMYK ... Ink color, D1 ... Main scanning direction, D2 ... Sub scanning direction, F1 ... Image, MS ... Mask, MS1 ... First mask, MS2 ... 2nd mask, Md1 ... 3rd mask area, Md2 ... 7th mask area, Mm1 ... 4th mask area, Mm1 ... 2nd mask area, Mm2 ... 8th mask area, Mm2 ... 1st 6 mask regions, Mu1 ... first mask region, Mu2 ... 5th mask region, NHw ... periodic width, P ... print medium, Q1 ... region, Q2 ... region, Q ... region, Q4 ... regions, TP ... test pattern, X ... nozzle group, Y ... nozzle group, dp ... nozzle pitch, dt1 ... dot, dt2 ... dot

Claims (9)

Print control for controlling a printing apparatus having a nozzle row in which a plurality of nozzles are arranged in the first direction and performing a pass in which the dot ratio changes in a second direction intersecting the first direction with a predetermined period width A device,
A test pattern in which a plurality of raster lines composed of dot rows arranged in the second direction are arranged in the first direction is set so that the length of the test pattern in the second direction is equal to or greater than the predetermined period width. A print instructing unit for causing the printing apparatus to print,
A density acquisition unit that acquires the density of dots at predetermined intervals along the second direction in each raster line obtained based on the captured image data of the printed test pattern;
A correction value calculation unit that calculates a density correction value for each predetermined interval of each raster line based on the acquired dot density;
Comprising
Print control device. The print control apparatus according to claim 1,
The predetermined interval is narrower than the predetermined period width;
Print control device. In the printing control apparatus according to claim 1 or 2,
The printing apparatus includes an imaging unit that captures the test pattern and obtains the captured image data.
Print control device. The print control apparatus according to claim 3,
The printing apparatus further includes a density detection unit that determines the density of the dots in each raster line based on the captured image data.
Print control device. In the printing control apparatus according to any one of claims 1 to 4,
The printing apparatus includes:
A print head having the nozzle row; and a carriage to which the print head is attached and configured to be movable in the second direction;
When the carriage reciprocates along the second direction, an image is printed by ejecting liquid onto the same area of the print medium in both the forward path and the return path;
The printing instruction unit determines a dot to be formed in each of the forward path and the backward path by a predetermined mask,
The predetermined period width is equal to a width of the predetermined mask along the second direction when the predetermined mask is applied;
Print control device. In the printing control apparatus according to any one of claims 1 to 5,
The density correction value calculated by the correction value calculation unit is used when the printing apparatus prints another image different from the test pattern,
The printing apparatus prints the other image after the density is corrected by the density correction value;
Print control device. The print control apparatus according to any one of claims 1 to 6, further comprising:
A storage instructing unit that causes the printing apparatus to store the density correction value calculated by the correction value calculating unit;
Print control device. Print control for controlling a printing apparatus having a nozzle row in which a plurality of nozzles are arranged in the first direction and performing a pass in which the dot ratio changes in a second direction intersecting the first direction with a predetermined period width A method,
A test pattern in which a plurality of raster lines composed of dot rows arranged in the second direction are arranged in the first direction is set so that the length of the test pattern in the second direction is equal to or greater than the predetermined period width. Printing on the printing device;
Obtaining a density of dots at predetermined intervals along the second direction in each raster line obtained based on the captured image data of the printed test pattern;
Calculating a density correction value for each of the predetermined intervals of each raster line based on the acquired dot density;
Comprising
Print control method. A computer for controlling a printing apparatus having a nozzle row in which a plurality of nozzles are arranged in a first direction and performing a pass in which a dot ratio changes with a predetermined period width in a second direction intersecting the first direction A program,
A test pattern in which a plurality of raster lines composed of dot rows arranged in the second direction are arranged in the first direction is set so that the length of the test pattern in the second direction is equal to or greater than the predetermined period width. A function for causing the printing apparatus to print,
A function of acquiring the density of dots at predetermined intervals along the second direction in each raster line obtained based on the captured image data of the printed test pattern;
A function of calculating a density correction value for each predetermined interval of each raster line based on the acquired dot density;
To make the computer
Computer program.

Images