JP2006231734A - Printing method, printer, printing program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in adjustment of a timing of printing by a nozzle and a print head unit, selection of a plurality of print head units, and their combination, two straight lines with a clear gap is printed because of the troublesome adjustment and limitation in the selection and the combination even when one straight line should be printed. <P>SOLUTION: This printing method comprises a process of a first change schedule for scheduling a first forward change and a first reverse change with respect to a pixel in a reference range, a process of a second change schedule for scheduling a second forward change and a second reverse change with respect to a pixel in a plurality of adjacent ranges, and an adjustment process for increasing or decreasing the number of times of the first forward change or the first reverse change on the basis of the magnitude relationship between the number of times of the first forward change or the first reverse change and the average of the number of times of the second forward change or the second reverse change. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention uses a plurality of nozzles arranged along the main scanning direction of printing, or a plurality of print head units each arranged along the main scanning direction and each having the plurality of nozzles. The present invention relates to a printing method for printing an image on a medium, a printing apparatus for performing the printing method, a printing program for causing the printing apparatus to perform the printing method, and a computer-readable recording medium on which the printing program is recorded.

  FIG. 14 shows a configuration of nozzles provided in a conventional printing apparatus, FIG. 15 shows a configuration of a print head unit provided in the conventional printing apparatus, and FIG. 16 shows a conventional printed image.

  As shown in FIG. 14A, in the conventional print head unit PHU, m (m is an arbitrary integer of 2 or more) nozzles N (1) to N (m) are inherently Although it must be arranged in a state parallel to the main scanning direction (in a state where it does not vary in the sub-scanning direction), it is not actually parallel to the main scanning direction as shown in FIG. May be arranged in a state (with variations in the sub-scanning direction).

  Further, as shown in FIG. 15A, conventional n (n is an arbitrary integer of 2 or more) print head units PHU (1) to PHU (n) (print head units PHU (1) to Each of the PHU (n) is the same as the print head unit PHU shown in FIG. 14A.) Originally, the PHU (n) is regularly arranged in the same posture, that is, in a posture parallel to the main scanning direction. In spite of having to be, in actuality, as shown in FIG. 15 (B), there are cases where they are irregularly arranged in a posture not parallel to the main scanning direction.

  The m nozzles N (1) to N (m) illustrated in FIG. 14B and the n print head units PHU (1) to PHU (n) illustrated in FIG. When an image of one straight line L extending in the main scanning direction as shown in (A) has to be printed, due to the state and posture not parallel to the main scanning direction as described above, As shown in FIG. 16B, there is a possibility that a problem of printing two straight lines L1 and L2 having a gap may occur.

  In order to avoid the occurrence of the problem, in the techniques described in the following Patent Documents 1 to 4, by adjusting the printing timing of each of the m nozzles N (1) to N (m), , The timing of printing by each of the n print head units PHU (1) to PHU (n) is adjusted.

  Moreover, in order to perform the same avoidance, in the techniques described in the following Patent Documents 5 to 7, for example, a large number of print head units (a number larger than the above-mentioned n) are manufactured, and among the large number of print head units, The selection and combination so that printing by the n print head units PHU (1) to PHU (n) after selection and combination is as close as possible to the single straight line L shown in FIG. I do.

JP-A-9-123482 JP 2002-178505 A JP 2002-248744 A JP 2001-232781 A JP-A-8-118647 JP-A-8-230190 JP 2001-388892 A

  However, in the adjustment of the printing timing of the conventional nozzle and the print head unit described above and the selection and combination of a plurality of print head units, due to the complexity of the adjustment and the limitation of the selection and combination, FIG. A straight line L as illustrated in A) cannot be printed with high accuracy, and there is a problem that the two straight lines L1 and L2 are printed while the existence of a gap is clear.

  In order to solve the above-described problem, the printing method according to the present invention sequentially discharges droplets from a plurality of nozzles to be arranged along the main scanning direction in the sub-scanning direction so that each pixel is A printing method for printing on a print medium an image composed of a plurality of pixels that display one of two gradations of “dark” and “light”. Among the plurality of first pixels displaying the “dark” and the plurality of second pixels displaying the “light” existing within the reference range for displaying the gradation, the plurality of first pixels are The first order change is planned to be changed from the “dark” to the “light” according to the descending order of the distance between the plurality of first pixels and the corresponding plurality of nozzles, and the first order change is supported. Preferably, the plurality of second pixels are combined with the plurality of second pixels and the corresponding plurality of pixels. A first change scheduled step in which a first reverse change is made to change from the “light” to the “dark” in ascending order of the distance between the nozzles of the plurality of pixels; A plurality of adjacent ranges located adjacent to each other, each of the adjacent ranges being present within each adjacent range of the plurality of adjacent ranges having the same area as the reference range The third pixel and the plurality of fourth pixels displaying the “light”, the plurality of third pixels are arranged in the descending order of the distance between the plurality of third pixels and the corresponding plurality of nozzles. The second order change to change from “dark” to the “light” is scheduled to be performed, and the plurality of fourth pixels are associated with the plurality of fourth pixels in order to cope with the second order change. According to the ascending order of the distance between the plurality of nozzles A second scheduled change step that schedules a second reverse change to change to the first order change or the number of the first reverse changes, the second order change or the second order change When it is smaller than the average value of the number of reverse changes, the number of the first order changes or the first order change is brought closer to the average value of the number of the second order changes or the second reverse change. When the number of the first order change or the second reverse change is greater than an average value of the number of the second order change or the second reverse change, the first order change or the An adjusting step of reducing the number of third reverse changes so as to approach the average value of the second forward changes or the second number of reverse changes.

  According to the printing method of the present invention, the adjustment step is performed for the plurality of first “dark” pixels and the plurality of second “light” pixels within the reference range in the first scheduled change step. The number of the first order change or the first reverse change scheduled according to the descending order or the ascending order of the distance, and the plurality of third “dark” in the plurality of adjacent ranges in the second change schedule step. ”Pixel and the plurality of fourth“ light ”pixels according to the magnitude relationship between the second order change or the average number of times of the second reverse change scheduled according to the descending or increasing order of the distance, After the first order change or the first reverse change is performed, the number of the first order change or the first reverse change is increased or decreased so that the number approaches the average value. The pseudo multi-gradation display accuracy within the reference range, and the second It is possible to equalize the precision of the pseudo multi-gradation display in said plurality of adjacent range after the forward change or the second reverse change.

  In the above-described printing method according to the present invention, the adjustment step is scheduled to increase the number of times of the first order change or the first reverse change, and to change the first order change or the first reverse change. This is done by adding the first order change or the first reverse change for pixels that are not.

  In the above-described printing method according to the present invention, the adjustment step is scheduled to reduce the number of the first order change or the first reverse change, and to change the first order change or the first reverse change. The at least one of the plurality of first pixels or the plurality of second pixels is canceled by canceling the first order change or the first reverse change.

  The printing apparatus according to the present invention sequentially discharges droplets from a plurality of nozzles to be arranged along the main scanning direction in the sub-scanning direction, so that each pixel is “deep” and “light”. A printing apparatus that prints on a printing medium an image composed of a plurality of pixels that display one of the two gradations, and that is within a reference range that displays a pseudo multi-gradation of the plurality of pixels. A plurality of first pixels displaying “dark” and a plurality of second pixels displaying “light”, the plurality of first pixels corresponding to the plurality of first pixels The first order change is made to change from the “dark” to the “light” according to the descending order of the distances between the plurality of nozzles, and the second order is made to correspond to the first order change. In ascending order of the distance between the plurality of second pixels and the corresponding plurality of nozzles. A first scheduled change portion that plans to perform a first reverse change to change from the “light” to the “dark”, and a plurality of pixels that are located adjacent to the reference range among the plurality of pixels A plurality of third pixels that display the “dark” and are present in each of the adjacent ranges of the plurality of adjacent ranges having the same width as the reference range. Regarding the plurality of fourth pixels displaying “light”, the plurality of third pixels are changed from the “dark” to the “light” according to the descending order of the distance between the plurality of third pixels and the corresponding plurality of nozzles. In order to cope with the second order change, the plurality of fourth pixels are connected between the plurality of fourth pixels and the corresponding plurality of nozzles. A second reverse change is performed in which the “light” is changed to the “dark” in ascending order of distance. When the number of the second scheduled change part and the first order change or the first reverse change is smaller than the average value of the second order change or the second reverse change Increasing the number of the first order change or the first order change so as to approach an average value of the second order change or the second number of reverse changes, and the first order change or When the number of times of the second reverse change is greater than the average value of the second order change or the number of the second reverse change, the number of the first order change or the third reverse change, And an adjusting unit that reduces the second order change or the second reverse change so as to approach an average value.

  In the printing apparatus according to the present invention described above, the adjustment unit is scheduled to increase the number of times of the first order change or the first reverse change, and to change the first order change or the first reverse change. This is done by adding the first order change or the first reverse change for pixels that are not.

  In the printing apparatus according to the present invention described above, the adjustment unit is scheduled to reduce the number of the first order change or the first reverse change, and to change the first order change or the first reverse change. The at least one of the plurality of first pixels or the plurality of second pixels is canceled by canceling the first order change or the first reverse change.

  The printing program according to the present invention sequentially discharges droplets from a plurality of nozzles to be arranged in the main scanning direction in the sub-scanning direction, so that each pixel is “dark” and “light”. Printing an image composed of a plurality of pixels that display one of the two gradations on a print medium, which includes a first change scheduled part, a second scheduled change part, and an adjustment part A printing program to be executed by the apparatus, wherein the “deep”, which is present in a reference range for pseudo-multi-gradation display among the plurality of pixels, is displayed on the first scheduled change portion. The plurality of first pixels and the plurality of second pixels displaying the “light” according to the descending order of the distance between the plurality of first pixels and the corresponding plurality of nozzles. A first order change is made to change from “dark” to “light” In order to correspond to the first order change, the plurality of second pixels are changed from the “light” to the “in order of increasing distance between the plurality of second pixels and the corresponding plurality of nozzles”. A plurality of pixels located adjacent to the reference range among the plurality of pixels in a first scheduled change step that schedules the first reverse change to be changed to “dark”; A plurality of third pixels that display the “dark” and are present in each of the adjacent ranges of the plurality of adjacent ranges having the same width as the reference range. Regarding the plurality of fourth pixels displaying “light”, the plurality of third pixels are changed from the “dark” to the “light” according to the descending order of the distance between the plurality of third pixels and the corresponding plurality of nozzles. Scheduled to make a second order change to " A second reverse change in which the plurality of fourth pixels are changed from the “light” to the “dark” in ascending order of the distances between the plurality of fourth pixels and the corresponding plurality of nozzles. A second scheduled change step that is scheduled to be performed, and the number of times of the first order change or the first reverse change in the adjustment unit is the number of times of the second order change or the second reverse change. Less than the average value of the first order change or the number of the first order change to approach the average value of the number of the second order change or the second reverse change, When the number of times of the first order change or the second reverse change is greater than the average value of the number of times of the second order change or the second reverse change, the first order change or the third reverse change The number of changes is reduced to approach the average value of the number of the second forward changes or the second reverse changes. And an adjusting step for executing the operation.

  In the above-described printing program according to the present invention, the adjustment step causes the adjustment unit to increase the number of times of the first order change or the first reverse change, the first order change, or the first order change. For a pixel that is not scheduled to be reversely changed, the first order change or the first reverse change is added to be executed.

  In the above-described printing program according to the present invention, the adjustment step causes the adjustment unit to reduce the number of times of the first order change or the first reverse change, the first order change, or the first order change. Canceling the first forward change or the first reverse change for at least one of the plurality of first pixels or the plurality of second pixels scheduled for reverse change. To do that.

  The above-described printing program is recorded on a computer-readable recording medium according to the present invention.

  Embodiments of a printing apparatus according to the present invention will be described with reference to the drawings.

"Constitution"
1 shows the configuration of the printing apparatus of the embodiment, FIG. 2 shows the pixels in the image of the embodiment, FIG. 3 shows the configuration of the nozzles in the print head unit of the embodiment, and FIG. The distance between the pixel (black circle) in the image of the embodiment and the nozzle (white circle) in the print head unit is shown.

  The printing apparatus PRT of the embodiment shown in FIG. 1 has pixels P (1, 1) and P (P) arranged in a matrix that form an input image IMG under the control of a computer (including a program). 1, 2), P (1, 3),. . . (Shown in FIG. 2), and the pixels P (1,1), P (1,2), P (1,3),. . . , A plurality of print head units PHU (1), (2), (3),. . . , Eight nozzles N (1), N (2),... That should be arranged parallel to the main scanning direction (actually arranged in a scattered manner). . . (See FIG. 3) and the positional error (exactly, the positional error between the pixel and the nozzle after the position conversion (shown in FIG. 4)) is optimally converted, Further, in order to output a medium MED on which an image in which the shading is corrected is output by correcting the shading of the pixel after the position conversion from the viewpoint of the positional error and pseudo multi-gradation, FIG. As shown, it has an input unit 10, a processing unit 20, a storage unit 30, and an output unit 40. With regard to pixel shading, “dark” and “light” indicate the relative degree of general multi-gradation, so in two gradations, “dark” means “black” and “light” "Means" white ".

  Here, for example, the pixel P (1, 1) corresponds to the nozzle N (1) of the print head unit PHU (1), and the pixel P (1, 2) corresponds to the nozzle N of the print head unit PHU (1). Corresponding to (2), the pixel P (1, 3) corresponds to the nozzle N (3) of the print head unit PHU (1), and the pixel P (1, 8) corresponds to the print head unit PHU (1). Corresponding to the nozzle N (8), the pixel P (1, 9) corresponds to the nozzle N (1) of the print head unit PHU (2).

  As shown in FIG. 1, the input unit 10 includes a scanner 11, a digital camera 12, a video camera 13, and the like, and an image IMG (regardless of whether it is a still image or a moving image), for example, bitmap data. Is used to be transferred to the subsequent processing unit 20.

  As shown in FIG. 1, the processing unit 20 includes a gradation processing unit 21, a position conversion unit 22, and a gradation correction unit 23.

  The gradation processing unit 21 performs processing on the gradation of the image IMG transferred from the input unit 10, that is, the resolution and the color expression system (CMYK system, RGB system).

  The position conversion unit 22 includes pixels P (1, 1), P (1, 2),. . . , P (1,9),. . . , Position conversion PT [1], PT [2], PT [3],. . . Try to apply. Here, the pixels P (1,1), P (1,2),. . . , P (1,9),. . . For example, the position conversion PT [1] is applied to the pixels P (1,1) · PT [1], P (1,2) · PT [1],. . . , P (1,9) · PT [1],. . . Moved to. Position conversion PT [1], PT [2], PT [3],. . . Is, for example, parallel movement (main scanning direction or sub-scanning direction) or rotational movement (clockwise and counterclockwise), and further, for example, 1 dot ( 1 pixel) Right, 1 dot left, 1 dot above, 1 dot below, 2 dots right, 2 dots left, 2 dots above,. . . 1 dot right and 1 dot lower combination, 1 dot right and 1 dot upper combination,. . . It is.

  The position conversion unit 22 also relates to the position conversion PT [1], the pixels P (1,1) · PT [1], the pixels P (1,2) · PT [1],. . . , Pixels P (1, 9) .PT [1],. . . And print head units PHU (1), (2), (3),. . . Nozzles N (1), (2),. . . , P (8), the distance d (P (1,1) · PT [1], PHU (1) · N (1)), as illustrated in FIG. Distances d (P (1,2) · PT [1], PHU (1) · N (2)),. . . , Distance d (P (1,9) · PT [1], PHU (2) · N (1)),. . . And a total value dSUM (PT [1]), which is the total value of these distances, is calculated. The position conversion unit 22 further includes other position conversion PT [2], PT [3],. . . , A similar distance is calculated, and the total values dSUM (PT [2]), dSUM (PT [3]),. . . Is calculated. The position conversion unit 22 includes a total value dSUM (PT [1]), a total value dSUM (PT [2]), a total value dSUM (PT [3]),. . . To find an optimum position conversion that minimizes the total value dSUM (hereinafter referred to as position conversion PT [best]).

  Here, the print head units PHU (1), PHU (2),. . . Nozzles N (1), N (2),. . . , N (8) is measured in advance at the time of manufacture of the printer at the factory, and the data is stored by reading from a ROM (corresponding to the storage unit 30) in which data representing the position is written. It can be obtained by accessing the database via a network (not shown), and it can be obtained after taking into account misalignment due to secular change by performing test printing after shipment from the factory. It is possible.

  The gradation correction unit 23 functions as a first change scheduled unit that performs the first scheduled change process, a second scheduled change unit that performs the second scheduled change process, and an adjustment unit that performs the adjustment process. That is, the gradation of the gradation of the pixel P (1, 1) · PT [best] after the position conversion PT [best] is applied to the pixel P (1, 1) is expressed as the pixel P (1, 1). A distance d (P (1,1) .PT [best], PHU (1) .N) which is a distance between PT [best] and the nozzle N (1) of the corresponding print head unit PHU (1). It is scheduled to be corrected according to (1)). Similarly, the gradation correcting unit 23 converts the gradation of the gradation of the pixel P (1,2) · PT [best] into the distance d (P (1,2) · PT [best], PHU (1) · N (2)), and further, the gradation of the gradation of the pixel P (1,9) · PT [best] is changed to the distance d (P (1,9) · PT [best], PHU ( 2) • N (1)) will be corrected.

  In more detail about the above-described correction schedule, the gradation correction unit 23 sets the ranges CR, AR1, AR2, AR3,. . . In order to balance the number of pixels P for which the gradation correction is scheduled before and after the correction (shown in FIG. 7), for example, within the range AR1, forward change (described later) and reverse change (described later) are performed. The multi-gradation that is to be displayed as the entire range AR1 before being applied and the multi-gradation that is to be displayed by the range AR1 after the forward change and the reverse change are substantially the same. Therefore, for example, the pixel P according to the distance d (P (1, 3) · PT [best], PHU (1) · N (1)) of the pixel P (1, 3) in the range AR1. When (1 and 3) are scheduled to be corrected from “dark” to “light” (hereinafter referred to as “order change”) (or when “light” is corrected to “dark”), In order to correspond to “change”, the distance d (P (5,2) · PT of the other pixel P (5,2) within the range AR1. best], PHU (1) · N (5)), the pixel P (5, 2) is corrected from “light” to “dark” (hereinafter referred to as “reverse change”) (or “dark”). ”To“ light ”).

  FIG. 5 shows an example of the pseudo multi-tone of the embodiment, FIG. 6 shows a dither mask for the pseudo multi-tone of the embodiment, and FIG. 7 shows a reference range and an adjacent range in the image of the embodiment. Indicates.

  The image IMG displays “red 1” by, for example, 63 “light” pixels and one “dark” pixel in order to display a pseudo multi-gradation as shown in FIG. As shown in FIG. 7, corresponding to the 8-by-8 dither mask DM shown in FIG. 6 to display “red 4” by four “light” pixels and four “dark” pixels. , Ranges CR, AR1, AR2, AR3,. . . It is divided into

  The gradation correction unit 23 is configured to input the ranges CR, AR1, AR2,. . . In addition to balancing the number of “dark” and “light” pixels before and after correction within each range, the ranges CR, AR1, AR2,. . . In order to balance the number of corrections between two or more ranges, for example, the pixel P (9, 9) to the pixel P (16, 16), the number of pixels P whose gradation is to be corrected is set to the adjacent ranges AR1, AR2, AR3,. . . , Pixels P (1,1) to P (8,8), P (9,1) to P (16,8), P (17,1) to P (24,8),. . . , P (17, 17) to P (24, 24) are adjusted, that is, increased / decreased, compared with the number of pixels P for which gradation correction is scheduled.

  Returning to FIG. 1, another configuration of the printing apparatus PRT will be described.

  The storage unit 30 temporarily stores the image IMG, and also performs processing (first change schedule step, second change schedule) performed by the printing apparatus PRT from the recording medium 50 such as a flexible disk or a CD-ROM. A program PRG (consisting of a plurality of steps S shown in FIGS. 9, 10, and 12) that defines a process, an adjustment process, and the like is installed.

  As shown in FIG. 1, the output unit 40 includes a printer 41, a display (liquid crystal, CRT) 42, and the like. The output unit 40 displays an image IMG that has been subjected to gradation processing, position conversion, and gradation correction by the processing unit 20. Used to print or display on media MED. Here, the printer 41 includes print head units PHU (1), PHU (2), PHU (3),. . . And print head units PHU (1), PHU (2), PHU (3),. . . Each includes eight nozzles N (1) to N (8) that eject ink droplets.

  FIG. 8 shows the configuration of the computer apparatus. As for the relationship between the printing apparatus PRT shown in FIG. 1 and the general computer apparatus COM shown in FIG. 8, the input unit 10 shown in FIG. 1 includes the input interface 110 shown in FIG. 20 comprises the CPU 120 of FIG. 8, the storage unit 30 of FIG. 1 comprises the ROM and RAM 130 of FIG. 8, and the output unit 40 of FIG. 1 comprises the output interface 140 of FIG. ing.

<Operation>
FIG. 9 is a flowchart illustrating the operation of the printing apparatus according to the embodiment. Hereinafter, the operation of the printing apparatus PRT of the embodiment will be described with reference to the flowchart of FIG. In order to facilitate understanding and explanation, the number of pixels P to be subjected to gradation order change and reverse change by the gradation correction unit 23 should be balanced (the number of reverse change and order change is determined in the order of adjacent ranges). The range to be adjusted with reference to the number of changes and reverse changes) is a reference range CR (shown in FIG. 7) consisting of 64 pixels P (9, 9) to P (16, 16) in the image IMG. Assuming that

  Step S10: The user of the printing apparatus PRT inputs the image IMG using the input unit 10.

  Step S11: When the image IMG is input, in the processing unit 20, the gradation processing unit 21 converts the additive color system RGB into the mixed color system CMYK as is conventionally known for the color system of the image IMG. Convert to

  Step S12: The gradation processing unit 21 also sets the resolution of the image IMG by the print head units PHU (1), PHU (2), PHU (3),. . . Of the nozzles N (1) to N (8).

  Step S13: The gradation processing unit 21 further binarizes the image IMG by performing error diffusion, dither processing, and the like on the image IMG.

  Step S <b> 14: The position conversion unit 22 performs the processing for all the pixels P (1, 1), pixels P (1, 2),. . . , Pixels P (1, 9),. . . , Position conversion PT [1], PT [2], PT [3],. . . Try to apply.

  Step S15: The position conversion unit 22 sets the distance d (P (1,1) · PT [1], PHU (1) · N (1)), distance d (P (1, 2) PT [1], PHU (1) N (2)),. . . , Distance d (P (1,9) · PT [1], PHU (2) · N (1)),. . . Is calculated. In the same manner, the position conversion unit 22 determines the distance d (P (1,1) · PT [2], PHU (1) · N (1)), the distance d (P (1) for the position conversion PT [2]. 2) .PT [2], PHU (1) .N (2)),. . . , Distance d (P (1,9) · PT [2], PHU (2) · N (1)),. . . , And another position transformation PT [3],. . . Similarly, the distances d (P (1,1) · PT [3], PHU (1) · N (1)),. . . Is calculated.

  Step S16: The position conversion unit 22 sets the distance d (P (1,1) · PT [1], PHU (1) · N (1)), distance d (P (1, 2) PT [1], PHU (1) N (2)),. . . , Distance d (P (1,9) · PT [1], PHU (2) · N (1)),. . . The total value dSUM (PT [1]), which is the total value of. Similarly, the position conversion unit 22 performs position conversion PT [2], position conversion PT [3],. . . , The total value dSUM (PT [2]), the total value dSUM (PT [3]),. . . Is calculated.

  Step S17: The position converter 22 adds the total value dSUM (PT [1]), the total value dSUM (PT [2]), the total value dSUM (PT [3]),. . . By searching for the smallest one of them, the optimum position conversion PT [best], which is the position conversion that gives the minimum total value, is found.

  Step S18: The gradation correcting unit 23 performs the position conversion PT [best] on the pixel P that has been subjected to the position conversion PT [best] according to the distance d between the pixel P and the corresponding nozzle N. The correction of the gradation of the pixel P is scheduled. The basic principle of the correction is that the pixel P (1,1) · PT [best], the pixel P (1,2) · PT [best],. . . , Pixels P (1,9) .PT [best],. . . Of the pixel P (1,1) · PT [best], P (1,2) · PT [best],. . . , P (1,9) .PT [best],. . . And the nozzle N (1) of the corresponding print head unit PHU (1), the nozzle N (2) of the print head unit PHU (1),. . . , Nozzles N (1),. . . Distance d (P (1,1) · PT [best], PHU (1) · N (1)), distance d (P (1,2) · PT [best], PHU (1) · N ( 2)),. . . , Distance d (P (1,9) · PT [best], PHU (2) · N (1)),. . . In other words, the gradation of the pixel P (1,1) · PT [best] is corrected by the distance d (P (1,1) · PT [best], PHU (1) · N (1)). In the same manner, the gray level of the pixel P (1,2) · PT [best] is changed to the distance d (P (1,2) · PT [best], PHU (1) · N. (2)) and the gradation of the pixel P (1,9) · PT [best] is changed to the distance d (P (1,9) · PT [best], PHU (2) · N (1). ).

  In actual correction, unlike the basic principle described above, in the image IMG, the ranges CR, AR1, AR2, AR3,. . . For each range of AR8 (shown in FIG. 7), the order of 64 pixels P existing in the range is planned to be changed from “dark” to “light” according to the descending order of the distance d. In order to cope with the above, a reverse change from “light” to “dark” is scheduled in ascending order of the distance d.

  FIG. 10 is a flowchart showing the order change and reverse change operations in the pixels within the reference range, and FIG. 11 is a state transition diagram showing the order change and reverse change operations. Hereinafter, the operation of forward change and reverse change will be described with reference to the flowchart of FIG. 10 and the state transition diagram of FIG.

  Step S18a: The gradation correcting unit 23 performs 64 pixels P (9, 9), pixels P (9, 10), pixels P (9, 11),. . . , Pixel P (16,16), distance d (P (9,9), PHU (2) · N (1)), distance d (P (9,10), PHU (2) · N (2) ), Distance d (P (9,11), PHU (2) · N (3)),. . . , In ascending order of distance d (P (16, 16), PHU (2) · N (8)), as shown in FIG.

  Step S18b: The density (gradation) of the pixel P (9, 11) having the longest distance d is scheduled to be changed from “dark” (black circle) to “light” (white circle). In order to cope with the change in the density of the pixel P (9, 11), it is planned to reversely change the density of the pixel P (9, 13) having the shortest distance d from “light” to “dark”.

  Step S18c: The density of the pixel P (16, 15) having the longest distance d after the distance d of the pixel P (9, 11) is scheduled to be changed from “dark” to “light”. In order to respond to the schedule for changing the order of density of the pixel P (16, 15), attention is paid to the pixel P (10, 16) whose distance d is the shortest next to the distance d of the pixel P (9, 13). Since the density is “dark”, the pixel P (10, 16) is skipped, and the pixel P (15, 11) whose distance d is short next to the distance d of the pixel P (10, 16). We plan to reversely change the density from “light” to “dark”.

  Step S18d: Since the density of the pixel P (12, 14) whose distance d is the second longest after the distance d of the pixel P (16, 15) is “light”, it remains “light”, that is, No correction is planned.

  Step S18e: The density of the pixel P (14, 13) whose distance d is the next longest to the distance d of the pixel P (12, 14) is scheduled to be changed from “dark” to “light”. In order to correspond to the order change of the pixel P (14, 13), the density of the pixel P (9, 10) whose distance d is short after the distance d of the pixel P (15, 11) is changed from “light” to “dark”. We plan to reverse change.

  Step S18f: Since the density of the pixel P (11, 12) whose distance d is the second longest after the distance d of the pixel P (14, 13) is “light”, it remains “light”, that is, the density is changed. Do not change anything. Accordingly, no change is made to the density of the pixel P (13, 13) whose distance d is short after the pixel P (9, 10).

  Thereafter, the steps S18b to 18f described above are performed for the other pixels P, that is, the order of changing the density of the pixels P from “dark” to “light” according to the descending order of the distance d. In order to cope with this, it is planned to reversely change the density of the pixel P from “light” to “dark” in ascending order of the distance d. However, not all of the 64 pixels P are scheduled to be changed in order or reversely, but are determined in advance based on characteristics of the reference range CR (for example, the position and importance of the reference range CR in the entire image IMG). Only a predetermined number of pixels are scheduled to be changed in order and reversely.

  Returning to the flowchart of FIG.

  Step S19: The gradation correcting unit 23 schedules the same order change and reverse change as in Step S18 (Steps S18a to 18f) for the pixel P in the adjacent range AR1 (shown in FIG. 7) adjacent to the reference range CR. Similarly, for the pixels P in the other seven adjacent ranges AR2 to AR8, the order change and the reverse change are scheduled in the same manner.

  Step S20: The gradation correction unit 23 calculates the average value of the number of forward changes or reverse changes in the adjacent ranges AR1 to AR8. More specifically, the number of order changes in the adjacent range AR1, the number of order changes in the adjacent range AR2,. . . The average value AVF between the number of forward changes in the adjacent range AR8 is calculated, or the number of reverse changes in the adjacent range AR1, the number of reverse changes in the adjacent range AR2,. . . The average value AVI between the number of reverse changes in the adjacent range AR8 is calculated.

  FIG. 12 is a flowchart showing an operation of increasing / decreasing the number of order changes and reverse changes in the reference range based on the number of order changes and reverse changes in the adjacent range. The operation of step S21 (shown in FIGS. 9 and 12) subsequent to step S20 (shown in FIG. 9) will be described below along the flowchart of FIG.

  Step S21: The gradation correction unit 23 adjusts the number of forward and reverse changes in the reference range CR. More specifically, the gradation correction unit 23 compares the average value AVF or reverse change average value AVI of the forward change in the adjacent ranges AR1 to AR8 with the number of forward or reverse changes in the reference range CR. (Step S21a), when the number of forward or reverse changes in the reference range CR is smaller than the average values AVF and AVI of the forward or reverse changes in the adjacent ranges AR1 to AR8, the forward and reverse changes in the reference range CR When the number of changes is increased (step S21b), on the contrary, when the number of forward or reverse changes in the reference range CR is larger than the average values AVF and AVI of the forward or reverse changes in the adjacent ranges AR1 to AR8, The number of forward or reverse changes in the range CR is decreased (step S21c).

  For example, as illustrated in FIG. 11, the gradation correction unit 23 assumes that the number of forward and reverse changes in the reference range CR is “3”. When the average value AVF, AVI of the number of forward changes or reverse changes is “4”, the pixel P (not shown) having the longest distance d is next to the pixel P (11, 12) corresponding to the “3” order change. )) Is changed from “dark” to “light”, and the distance d is next to the pixel P (9, 10) corresponding to the “3” reverse change to correspond to the change in order. It is decided to reversely change the short pixel P (not shown) from “light” to “dark”. On the other hand, under the same assumption, in contrast to the above, when the average value AVF, AVI of the number of forward or reverse changes in the adjacent ranges AR1 to AR8 is “2”, the “3” th This cancels the plan to change the order of the pixel P (11, 12) corresponding to the change in order from “dark” to “light”, and corresponds to the “3” reverse change in order to cope with the cancellation of the change in order. Cancels the plan to reversely change the pixel P (9, 10) from “light” to “dark”.

  Returning again to the flowchart of FIG. 9, the description will be continued.

  Step S22: In the output unit 40, the printer 41 uses the pixel P (1,1) · PT [1], the pixel P (1,1) · PT [1] whose gradation is corrected in the entire image IMG including the reference range CR and the adjacent ranges AR1 to R8. P (1,2) · PT [1],. . . , Pixels P (1, 9) .PT [1],. . . Is printed on the medium MED.

"effect"
As described above, in the printing apparatus PRT of the embodiment, the position conversion unit 22 includes the pixel P (1, 1), the pixel P (1, 2),. . . , Pixels P (1, 9),. . . To position conversion PT [1], PT [2], PT [3],. . . Are successively added, and the total value d (PT [1]), the total value (PT [2]), and the total value (PT [3], which are the total values of the distances between the position-converted pixels and the corresponding nozzles. ]),. . . Find the optimal position transformation PT [best] that gives the smallest sum of the values. The gradation correction unit 23 further includes the pixel P (1, 1) · PT [best], the pixel P (1,2) · PT [best],. . . , Pixels P (1,9) .PT [best],. . . Are the distance d (P (1,1) · PT [best], PHU (1) · N (1)), the distance between the pixel and the corresponding nozzle, and the distance d (P (1,2). ) · PT [best], PHU (1) · N (2)),. . . , Distance d (P (1,9) · PT [best], PHU (2) · N (1)),. . . Based on the principle that the greater the distance, the lighter the color and the darker the distance, the darker the color will be corrected, according to the ascending or descending order, and the reverse change from “light” to “light” will be planned. To do. In addition, the gradation correction unit 23 additionally compares the number of forward or reverse changes in the reference range CR with the average values AVF and AVI of the forward or reverse changes in the adjacent ranges AR1 to AR8. The number of forward or reverse changes within the reference range CR is increased or decreased.

  As a result, it is impossible to avoid the situation where a line that should originally be printed on one straight line is printed on two straight lines with a gap, but the user recognizes the gap between the two straight lines. This makes it possible to give the user the impression that a single straight line is printed. In addition, within the reference range CR, which is one of the unit ranges for displaying the pseudo multi-gradation, the reference range CR must originally display the multi-gradation (for example, “red 4” (FIG. 5 Can be displayed with high accuracy without impairing the balance of the number between “deep” and “light” within the reference range CR. Further, between the reference range CR and the adjacent ranges AR1 to AR8, the number of order changes and reverse changes in the reference range CR is the average value AVF of the number of forward changes and reverse changes in the adjacent ranges AR1 to AR8. Therefore, the number of forward and reverse changes in the reference range CR is significantly larger than the number of forward and reverse changes in the adjacent ranges AR1 to AR8. As a result, it is possible to avoid a situation where the gradation balance between the reference range CR and the adjacent ranges AR1 to AR8 is lost.

<Modification 1>
As described above, the pixels P (14, 13) and P (9, 10) are subsequently changed in order or reversely to the pixel P (not shown) to be changed in order, so that the reference range CR is obtained. Instead of increasing the number of forward and reverse changes, a pixel P that does not need to be forward or reverse in nature, for example, a pixel having a relatively high priority in descending or ascending rules. Similar to the above, the number of forward and backward changes in the reference range CR is increased by changing the order or reverse of a certain pixel P (12, 14) and pixel P (10, 16). It is possible to obtain an advantageous effect.

<Modification 2>
FIG. 13 shows a reference range and an adjacent range of the modification. Instead of the reference range CR and adjacent ranges AR1 to AR8 shown in FIG. 7, a plurality of print head units PHU (1) to PHU (24) are arranged in four rows as shown in FIG. In the case where the print head unit PHU (in the third line to be printed on the medium MED is used, for example, as shown in FIG. 2) The average number of forward and reverse changes in the area to be printed in the reference area CS (corresponding to the reference area CR) and the areas AC1 to AC8 (corresponding to the adjacent areas AR1 to AR8) adjacent to the reference area CS The same effect as described above can also be obtained by increasing or decreasing the number of times of forward change and reverse change in the reference region CS based on the values AVF and AVI.

1 is a diagram illustrating a configuration of a printing apparatus according to an embodiment. The figure which shows the pixel in the image of an Example. The figure which shows the structure of the nozzle in the print head unit of an Example. FIG. 4 is a diagram illustrating a distance between a pixel in an image of an embodiment and a nozzle in a print head unit. The figure which shows the pseudo multi gradation of an Example. The figure which shows the dither mask for pseudo multi gradations of an Example. The figure which shows the reference | standard range and adjacent range in the image of an Example. The figure which shows the structure of a computer apparatus. 6 is a flowchart illustrating the operation of the printing apparatus according to the embodiment. The flowchart which shows the operation | movement of the order change and reverse change within the reference | standard range of an Example. The state transition diagram which shows the operation | movement of the order change and reverse change of an Example. The flowchart which shows the increase / decrease operation | movement of the frequency | count of the order change and reverse change in the reference | standard range based on the order change and reverse change in the adjacent range of an Example. The figure which shows the reference | standard range and adjacent range of a modification. The figure which shows the structure of the nozzle of the conventional printing apparatus. FIG. 6 is a diagram illustrating a configuration of a print head unit of a conventional printing apparatus. The figure which shows the image printed conventionally.

Explanation of symbols

PRT printing apparatus 10 input unit 20 processing unit 30 storage unit 40 output unit 50 recording medium 22 position conversion unit 23 gradation correction unit

Claims (10)

By sequentially discharging droplets from a plurality of nozzles to be arranged along the main scanning direction in the sub-scanning direction, each pixel has one of two gradations of “dark” and “light”. A printing method for printing an image composed of a plurality of pixels for displaying gradation on a printing medium,
Among the plurality of pixels, a plurality of first pixels that display the “dark” and a plurality of second pixels that display the “light” that exist within a reference range in which pseudo gray scales are displayed. The first order of changing the plurality of first pixels from the “dark” to the “light” according to the descending order of the distances between the plurality of first pixels and the corresponding plurality of nozzles. In order to cope with the first order change, the plurality of second pixels are changed from the “light” to the “dark” in ascending order of the distance between the plurality of second pixels and the corresponding plurality of nozzles. A first scheduled change step that schedules a first reverse change to change to
Among the plurality of pixels, a plurality of adjacent ranges located adjacent to the reference range, each adjacent range having the same area as the reference range, and within each adjacent range of the plurality of adjacent ranges Regarding the plurality of third pixels displaying “dark” and the plurality of fourth pixels displaying “light”, the plurality of third pixels correspond to the plurality of third pixels. In accordance with the descending order of the distance between the plurality of nozzles, the second order change is made to change from the “deep” to the “light”, and the plurality of fourth orders are made to correspond to the second order change. A second scheduled change step for performing a second reverse change in which the pixel is changed from the “light” to the “dark” according to the ascending order of the distance between the plurality of fourth pixels and the corresponding plurality of nozzles. When,
When the number of times of the first order change or the first reverse change is smaller than an average value of the number of times of the second order change or the second reverse change, the first order change or the first reverse change The number of forward changes is increased to approach an average value of the second forward changes or the second reverse changes, and the first forward change or the second reverse change is When the order of 2 or the number of times of the second reverse change is larger than the average value, the number of the first order change or the third reverse change is changed to the second order change or the second reverse change. And an adjusting step of decreasing so as to approach the average value of the number of times of printing.   The adjustment step includes increasing the number of times of the first order change or the first reverse change, and the first order change for a pixel for which the first order change or the first reverse change is not scheduled. The printing method according to claim 1, wherein the printing is performed by adding the first reverse change.   In the adjusting step, the first order change or the first reverse change is reduced in number, the first order change or the first reverse change is scheduled for the plurality of first pixels or The printing method according to claim 1, wherein the printing is performed by canceling the first order change or the first reverse change for at least one of the plurality of second pixels. By sequentially discharging droplets from a plurality of nozzles to be arranged along the main scanning direction in the sub-scanning direction, each pixel has one of two gradations of “dark” and “light”. A printing apparatus for printing an image composed of a plurality of pixels for displaying gradation on a print medium,
Among the plurality of pixels, a plurality of first pixels that display the “dark” and a plurality of second pixels that display the “light” that exist within a reference range in which pseudo gray scales are displayed. The first order of changing the plurality of first pixels from the “dark” to the “light” according to the descending order of the distances between the plurality of first pixels and the corresponding plurality of nozzles. In order to cope with the first order change, the plurality of second pixels are changed from the “light” to the “dark” in ascending order of the distance between the plurality of second pixels and the corresponding plurality of nozzles. A first scheduled change section that is scheduled to perform a first reverse change to
Among the plurality of pixels, a plurality of adjacent ranges located adjacent to the reference range, each adjacent range having the same area as the reference range, and within each adjacent range of the plurality of adjacent ranges Regarding the plurality of third pixels displaying “dark” and the plurality of fourth pixels displaying “light”, the plurality of third pixels correspond to the plurality of third pixels. In accordance with the descending order of the distance between the plurality of nozzles, the second order change is made to change from the “deep” to the “light”, and the plurality of fourth orders are made to correspond to the second order change. A second scheduled change unit that plans to perform a second reverse change in which the pixel is changed from the “light” to the “dark” in ascending order of the distance between the plurality of fourth pixels and the corresponding plurality of nozzles. When,
When the number of times of the first order change or the first reverse change is smaller than an average value of the number of times of the second order change or the second reverse change, the first order change or the first reverse change The number of forward changes is increased to approach an average value of the second forward changes or the second reverse changes, and the first forward change or the second reverse change is When the order of 2 or the number of times of the second reverse change is larger than the average value, the number of the first order change or the third reverse change is changed to the second order change or the second reverse change. And an adjustment unit that reduces the value so as to approach the average value of the number of times of printing.   The adjustment unit increases the number of times of the first order change or the first reverse change, and the first order change is performed for a pixel for which the first order change or the first reverse change is not scheduled. The printing apparatus according to claim 4, wherein the first reverse change is added.   The adjustment unit reduces the number of the first order change or the first reverse change, the plurality of first pixels for which the first order change or the first reverse change is scheduled, 5. The printing apparatus according to claim 4, wherein the first order change or the first reverse change is canceled with respect to at least one of the plurality of second pixels. 6. By sequentially discharging droplets from a plurality of nozzles to be arranged along the main scanning direction in the sub-scanning direction, each pixel has one of two gradations of “dark” and “light”. Printing program for causing a printing apparatus having a first scheduled change portion, a second scheduled change portion, and an adjustment unit to print an image composed of a plurality of pixels for displaying gradation on a print medium Because
Among the plurality of pixels, a plurality of first pixels displaying the “dark” and the “light” which are present in a reference range in which pseudo gray scales are displayed among the plurality of pixels, and the “light”. The plurality of first pixels are changed from the “dark” to the “light” according to the descending order of the distances between the plurality of first pixels and the corresponding plurality of nozzles. The first order is scheduled to be changed, and the plurality of second pixels are arranged according to the ascending order of the distance between the plurality of second pixels and the corresponding plurality of nozzles in order to cope with the first order change. A first scheduled change step that schedules a first reverse change to change from the “light” to the “dark”;
The plurality of adjacent ranges that are adjacent to the reference range among the plurality of pixels in the second scheduled change portion, and each adjacent range has the same area as the reference range. Among the plurality of third pixels displaying “dark” and the plurality of fourth pixels displaying “light”, which are present in each adjacent range of the adjacent ranges of the plurality of third pixels. Scheduled to perform a second order change that changes from the “dark” to the “light” according to the descending order of the distance between the plurality of third pixels and the corresponding plurality of nozzles, and corresponds to the second order change. Therefore, a second reverse change is performed in which the plurality of fourth pixels are changed from the “light” to the “dark” in the ascending order of the distances between the plurality of fourth pixels and the corresponding plurality of nozzles. A second scheduled change process for scheduling
In the adjustment unit, when the number of times of the first order change or the first reverse change is smaller than an average value of the number of times of the second order change or the second reverse change, the first order change Alternatively, the number of first order changes is increased so as to approach the average value of the second order changes or the second number of reverse changes, and the first order change or the second reverse change is performed. When the number of times is greater than the average value of the number of times of the second order change or the second number of reverse changes, the number of times of the first order change or the third number of reverse changes is changed to the second order change or the second order change. A printing program comprising: an adjusting step for executing a reduction so as to approach an average value of the number of times of the second reverse change.   In the adjustment step, the adjustment unit is configured to increase the number of times of the first order change or the first reverse change, and the pixels that are not scheduled for the first order change or the first reverse change. The printing program according to claim 7, wherein execution is performed by adding a first order change or the first reverse change.   In the adjustment step, the adjustment unit is configured to reduce the number of times of the first order change or the first reverse change, and to change the first order change or the first reverse change. The at least one pixel of the first pixel or the plurality of second pixels is executed by canceling the first order change or the first reverse change. Item 8. The printing program according to Item 7. A computer-readable recording medium on which the printing program according to claim 7 is recorded.

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