JP3876654B2 - Correction of paper feed error in printer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for performing printing by recording ink dots on a print medium while moving a print head in a main scanning direction.
[0002]
[Prior art]
As computer output devices, ink jet printers and laser printers that eject ink from a head have become widespread. In particular, in recent years, color printers using color inks have been widely used.
[0003]
Various print media for inkjet printers are commercially available. Since different inks have different color developability, there is a great difference in image quality. In addition, the type of print medium also affects the accuracy of sub-scan feed (hereinafter referred to as “paper feed”) of the print medium. For example, an actual feed amount may be considerably different between a print medium having a slippery surface and a print medium having a less slippery surface even if the same feed operation is performed. Further, the accuracy of paper feeding tends to vary considerably from printer to printer.
[0004]
The quality of the paper feeding accuracy has a great influence on the image quality. However, in a printer that performs printing in a so-called interlaced recording mode, it is possible to suppress deterioration in image quality due to a paper feed error to some extent by appropriately setting the paper feed amount. Here, the “interlace recording mode” means a printing method performed using a print head having nozzles arranged at a nozzle pitch that is twice or more the dot pitch in the sub-scanning direction (that is, main scanning line pitch). Yes. When such a print head is used, a gap is generated between main scanning lines (raster lines) that can be recorded by one main scanning. In order to eliminate this gap, the number of main scans equal to the number of main scan lines included in the gap is further required. It is known that various feed amounts can be adopted in such an interlace recording mode. Therefore, conventionally, by appropriately selecting the paper feed amount in the interlaced recording mode, the influence of image quality due to variations in paper feed accuracy has been suppressed to a small level.
[0005]
[Problems to be solved by the invention]
For the reasons described above, direct correction of paper feed error has not been considered much in interlaced recording mode printers. However, with the recent progress of high image quality of printers, there has been a demand for further improving image quality by appropriately correcting paper feed errors in printers that perform printing in the interlaced recording mode. Such a demand is not only increasing for printers using only the interlaced recording mode but also for printers using the non-interlaced recording mode.
[0006]
SUMMARY An advantage of some aspects of the invention is to provide a technique capable of improving image quality by correcting a paper feeding error of a printer.
[0007]
[Means for solving the problems and their functions and effects]
To achieve the above object, the method of the present invention corrects the sub-scan feed amount of a print medium in a printing apparatus that performs printing by recording ink dots on the print medium while moving the print head in the main scanning direction. A method of (a) measuring the effect on image quality due to a sub-scan feed error caused by a manufacturing error of a paper feed roller for feeding the print medium in the sub-scan direction for each printing device; (B) a step of correcting the sub-scan feed amount based on the actual measurement result of the step (a) when printing an image,
The step (a)
A step of setting a plurality of feed amounts used in actual printing as the feed amount of the sub-scan feed of the print medium;
A different correction value is used as a test pattern for determining a correction value for the representative feed amount to be printed using at least one representative feed amount selected in advance from the plurality of feed amounts. Printing a test pattern including a plurality of color patches each printed;
Predicting other feed amount correction values based on the representative feed amount correction values set according to the test pattern printing results;
Including
The step (b) is a step of correcting the sub-scan feed amount based on the correction value related to the representative feed amount and the correction value predicted for the other feed amount when printing an image. Including
The other feed amount correction values are predicted from the typical feed amount correction values according to a predetermined prediction curve that is not a straight line.
[0008]
According to this method, the effect on the image quality due to the sub-scan feed error caused by the manufacturing error of the paper feed roller is measured for each printing apparatus, and the sub-scan feed amount is corrected based on the actual measurement result. Even when the tolerance of the manufacturing error of the paper feed roller is large, it is possible to improve the image quality by correcting the paper feed error. Further, since the test pattern is printed only with respect to a representative feed amount among a plurality of feed amounts used in printing, it is possible to complete the work necessary for correction with little effort.
The print head has a plurality of nozzles arranged in the sub-scanning direction at a nozzle pitch k times (k is an integer of 2 or more) in the sub-scanning direction substantially perpendicular to the main scanning direction. The plurality of feed amounts may be feed amounts used for printing in the interlace recording mode, and the test pattern printing may be executed according to the interlace recording mode.
The other feed amount correction values may be predicted from the representative feed amount correction values according to a predetermined prediction curve. .
Further, the representative feed amount may include a maximum value among the plurality of feed amounts.
[0009]
The print head has a plurality of nozzles arranged in the sub-scanning direction at a nozzle pitch k times (k is an integer of 2 or more) in the sub-scanning direction substantially perpendicular to the main scanning direction. The image printing in the step (b) may be executed in accordance with the interlace recording mode.
[0010]
In this way, even in a printer that performs printing in the interlaced recording mode, it is possible to appropriately correct the sub-scan feed error caused by the paper feed roller manufacturing error.
[0011]
The step (a) includes a step of printing a predetermined test pattern used for measuring the influence on the image quality due to the sub-scan feed error, and the step of printing the test pattern includes the printing device. It can be executed in response to a user command.
[0012]
According to this configuration, even when the paper feed error changes over time, it is possible to correct this and improve the image quality.
[0013]
The present invention can be realized in various forms, for example, a sub-scan feed amount (paper feed amount) correction method and apparatus, a sub-scan feed control method and apparatus, and a sub-scan feed amount correction. Printing method and apparatus in consideration of printing, printing control apparatus and method for controlling printing apparatus in consideration of correction of sub-scan feed amount, computer program for realizing the method and apparatus, and recording medium on which the computer program is recorded It can be realized in various forms such as a data signal including the computer program and embodied in a carrier wave.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in the following order based on examples.
A. Overall configuration of the device:
B. General procedure for paper feed correction:
C. Details on how to print test patterns and how to determine paper feed correction values:
D. Test pattern print signal configuration:
E. Variation:
[0015]
A. Overall configuration of the device:
FIG. 1 is a block diagram showing the configuration of a printing system as an embodiment of the present invention. This printing system includes a computer 90 and a color inkjet printer 20. The printing system including the printer 20 and the computer 90 can be called a “printing apparatus” in a broad sense.
[0016]
In the computer 90, an application program 95 operates under a predetermined operating system. A video driver 91 and a printer driver 96 are incorporated in the operating system, and print data PD to be transferred to the printer 20 is output from the application program 95 via these drivers. The application program 95 that performs image retouching or the like performs desired processing on the image to be processed, and displays an image on the CRT 21 via the video driver 91.
[0017]
When the application program 95 issues a print command, the printer driver 96 of the computer 90 receives the image data from the application program 95 and converts it into print data PD to be supplied to the printer 20. The printer driver 96 includes a resolution conversion module 97, a color conversion module 98, a halftone module 99, a rasterizer 100, a user interface display module 101, a test pattern supply module 102, and a color conversion lookup table LUT. And are provided.
[0018]
The resolution conversion module 97 plays a role of converting the resolution of the color image data formed by the application program 95 into the print resolution. The image data thus converted in resolution is still image information composed of three color components of RGB. The color conversion module 98 converts RGB image data into multi-tone data of a plurality of ink colors that can be used by the printer 20 for each pixel while referring to the color conversion lookup table LUT.
[0019]
The color-converted multi-gradation data has, for example, 256 gradation values. The halftone module 99 performs so-called halftone processing to generate halftone image data. The halftone image data is rearranged in the order of data to be transferred to the printer 20 by the rasterizer 100, and output as final print data PD. The print data PD includes raster data indicating the dot formation state during each main scan and data indicating the sub-scan feed amount.
[0020]
The user interface display module 101 has a function of displaying various user interface windows related to printing, and a function of receiving user input in these windows.
[0021]
The test pattern supply module 102 has a function of reading a test pattern print signal TPS used for determining a correction value for the sub-scan feed amount (also referred to as “paper feed amount”) from the hard disk 92 and supplying the read test pattern print signal TPS to the printer 20. Have. When the test pattern print signal TPS is stored as compressed data, the test pattern print signal TPS has a function of expanding the compressed data.
[0022]
The printer driver 96 corresponds to a program for realizing a function of supplying the print data PD and the test pattern print signal TPS to the printer 20. A program for realizing the function of the printer driver 96 is supplied in a form recorded on a computer-readable recording medium. Such recording media include flexible disks, CD-ROMs, magneto-optical disks, IC cards, ROM cartridges, punch cards, printed matter on which codes such as bar codes are printed, computer internal storage devices (such as RAM and ROM). A variety of computer-readable media such as a memory) and an external storage device can be used. It is also possible to download such a computer program to the computer 90 via the Internet.
[0023]
A computer 90 having a printer driver 96 functions as a print control device that supplies the print data PD and the test pattern print signal TPS to the printer 20 to perform printing.
[0024]
FIG. 2 is a schematic perspective view showing the main configuration of the color inkjet printer 20. The printer 20 includes a paper stacker 22, a paper feed roller 24 driven by a step motor (not shown), a platen 26, a carriage 28, a carriage motor 30, a traction belt 32 driven by the carriage motor 30, and a carriage. And a guide rail 34 for 28. A print head 36 having a large number of nozzles is mounted on the carriage 28.
[0025]
The printing paper P is taken up by the paper feed roller 24 from the paper stacker 22 and fed on the surface of the platen 26 in the sub-scanning direction. The carriage 28 is pulled by a pulling belt 32 driven by a carriage motor 30 and moves in the main scanning direction along the guide rail 34. The main scanning direction is perpendicular to the sub-scanning direction.
[0026]
FIG. 3 is a block diagram showing an electrical configuration of the inkjet printer 20. The printer 20 includes a reception buffer memory 50 that receives a signal supplied from a computer 90, an image buffer 52 that stores print data, a system controller 54 that controls the overall operation of the printer 20, a main memory 56, and an EEPROM 58. And. The system controller 54 is further connected to a main scanning drive circuit 61 that drives the carriage motor 30, a sub-scanning drive circuit 62 that drives the paper feed motor 31, and a head drive circuit 63 that drives the print head 36. .
[0027]
The main scanning drive circuit 61, the carriage motor 30, the traction belt 32 (FIG. 2), and the guide rail 34 constitute a main scanning drive mechanism. The sub-scanning drive circuit 62, the paper feed motor 31, and the paper feed roller 24 (FIG. 2) constitute a sub-scanning drive mechanism (or “feed mechanism”).
[0028]
The print data transferred from the computer 90 is temporarily stored in the reception buffer memory 50. In the printer 20, the system controller 54 reads necessary information from the print data from the reception buffer memory 50, and sends control signals to the drive circuits 61, 62, and 63 based on the read information.
[0029]
The image buffer 52 stores print data of a plurality of color components received by the reception buffer memory 50. The head drive circuit 63 reads the print data of each color component from the image buffer 52 in accordance with a control signal from the system controller 54 and drives the nozzle array of each color provided in the print head 36 in response to this.
[0030]
FIG. 4 is a perspective view showing the configuration of the sub-scanning drive mechanism. The power of the paper feed motor 31 is transmitted to the paper feed roller 24 and the paper discharge roller 42 via the gear train 40. The paper feed roller 24 is provided with a driven roller 25, and the paper discharge roller 42 is also provided with a jagged roller 44 as its driven roller. The printing paper P is fed while being sandwiched by these rollers, and moves on the platen 26.
[0031]
A rotary encoder 46 composed of a code plate 46a and a photo sensor 46b is provided on the shaft of the paper feed roller 24. The paper feed amount (sub-scan feed amount) is determined according to the pulse signal from the rotary encoder 46.
[0032]
FIG. 5 is an explanatory diagram showing the nozzle arrangement on the lower surface of the print head 36. The print head 36 has a black nozzle row and a color nozzle row arranged on a straight line along the sub-scanning direction SS. In this specification, the “nozzle row” is also referred to as “nozzle group”.
[0033]
The black nozzle row (indicated by white circles) has 180 nozzles # 1 to # 180. These nozzles # 1 to # 180 are arranged at a constant nozzle pitch k · D along the sub-scanning direction. Here, D is the dot pitch in the sub-scanning direction SS, and k is an integer. The dot pitch D in the sub-scanning direction is equal to the pitch of the main scanning line (raster line). Hereinafter, the integer k representing the nozzle pitch k · D is simply referred to as “nozzle pitch k”. The unit of the nozzle pitch k is [dot], which means the dot pitch in the sub-scanning direction.
[0034]
In the example of FIG. 5, the nozzle pitch k is 4 dots. However, the nozzle pitch k can be set to an arbitrary integer of 2 or more.
[0035]
The color nozzle row includes a yellow nozzle group Y (indicated by a white triangle), a magenta nozzle group M (indicated by a black square), and a cyan nozzle group C (indicated by a white rhombus). In this specification, the nozzle group for chromatic ink is also referred to as a “chromatic nozzle group”. Each chromatic nozzle group has 60 nozzles # 1 to # 60. Further, the nozzle pitch of the chromatic nozzle group is the same as the nozzle pitch k of the black nozzle row. The nozzles of the chromatic color nozzle group are arranged at the same sub-scanning position as the nozzles of the black nozzle row.
[0036]
At the time of printing, ink droplets are ejected from each nozzle while the print head 36 is moving at a constant speed in the main scanning direction together with the carriage 28 (FIG. 2). However, depending on the printing method, not all nozzles are always used, and only some nozzles may be used.
[0037]
In black and white printing, almost all 180 black nozzles are used. On the other hand, in color printing, 60 nozzles are used for each color of CMY, and 60 black nozzles are also used. The 60 black nozzles used in color printing are, for example, nozzles # 121 to # 180 arranged at the same sub-scanning position as the 60 cyan nozzles.
[0038]
B. General procedure for paper feed correction:
As will be described below, the paper feed error is corrected before shipment of the printer 20 and can be corrected by the user after shipment.
[0039]
FIG. 6 is a flowchart showing a procedure for paper feed correction before the printer 20 is shipped. In step S1, the type of printing paper (printing medium) scheduled to be used by the printer 20 is sequentially selected. Examples of types of printing paper include plain paper, glossy film, photographic paper, and roll-type photographic paper. In step S2, the selected printing paper is set in the printer 20, and a predetermined test pattern is printed.
[0040]
FIG. 7 shows an example of a test pattern. In this example, a test pattern including three color patches having different paper feed correction values δ is shown. The patch number printed beside each color patch is associated in advance with the paper feed correction value δ. However, the paper feed correction value δ is drawn for convenience only and is not actually printed. Each color patch is a gray patch in which a gray region having a uniform density is reproduced with composite black using CMY inks. Such a gray patch reflects both a paper feed error and a position error of each color dot. Since the actual printed image quality is affected not only by the paper feed error but also by the position error of each color dot, it is preferable to use a gray patch reproduced with composite black as a test pattern from the viewpoint of improving the image quality. However, various other patterns can be used as the test pattern. For example, other types of color patches, ruled line patterns, and the like can be used. In the present specification, “color patch” means an image area reproduced in a substantially uniform color. Details of the test pattern printing method will be described later.
[0041]
In this specification, “composite black” means a gray color reproduced using inks of three hues of CMY, and may be reproduced using three or more types of inks. For example, when dark ink and light ink can be used for cyan and magenta, it is also possible to reproduce composite black using these four types of ink and five types of yellow ink.
[0042]
The main factor of the paper feed error in the printer 20 is a manufacturing error of the paper feed roller 24 (FIG. 4). This manufacturing error includes an outer diameter error and a surface roughness error. For example, if the outer diameter of the paper feed roller 24 is larger than the design value, the feed error becomes positive, and if it is smaller, it becomes negative. In this embodiment, correction of the paper feed error due to the manufacturing error of the paper feed roller 24 is performed for each printer before shipment. Therefore, even if the tolerance of the paper feed roller 24 is set to be slightly large, the paper feed error during actual printing can be made almost zero. Further, since the yield of the paper feed roller 24 is increased as the tolerance for the manufacturing error of the paper feed roller 24 is relaxed, there is an advantage that the cost of the printer 20 is reduced.
[0043]
In step S3 in FIG. 6, the color patch with the highest image quality is selected from the plurality of printed color patches, and the patch number is set in the EEPROM 58 (FIG. 3) of the printer 20. In the example of FIG. 7, white stripes are generated in the uppermost color patch, and black stripes are generated in the lowermost test pattern. Therefore, the patch number of the central color patch without such image quality deterioration is stored in the EEPROM 58. The paper feed correction value set by the inspection before shipment is referred to as a “reference correction value”.
[0044]
In step S4, it is determined whether or not steps S1 to S3 have been completed for all printing sheets scheduled to be used by the printer 20, and if not, the process returns to step S1. Here, “all print sheets scheduled to be used by the printer 20” means types of sheets that can be selected by the user in the property window of the printer driver 96 (FIG. 1). In this way, the paper feed reference correction value is set for all types of printing paper.
[0045]
FIG. 8 is a flowchart showing the procedure of paper feed correction by the user. In step S11, the user selects the type of printing paper, and in step S12, the test pattern is printed by inputting a test pattern print command. FIG. 9 is an explanatory diagram illustrating an example of a user interface window W1 that allows a user to issue a test pattern print instruction. This window W1 is a utility window in the printer properties, and is provided with a button B1 for inputting a print instruction for a paper feed adjustment test pattern. When the user clicks the button B1, the test pattern supply module 102 (FIG. 1) reads the test pattern print signal TPS from the hard disk 92 and supplies it to the printer 20, and the printer 20 prints the test pattern accordingly. This test pattern may be the same as the test pattern (FIG. 7) used for paper feed correction before shipment, or may be a different test pattern. In the present embodiment, it is assumed that the test pattern shown in FIG. The configuration of the test pattern print signal TPS will be described later.
[0046]
In step S13 of FIG. 8, a color patch with the highest image quality is selected from a plurality of printed color patches, and the patch number is set. FIG. 10 is an explanatory diagram showing an example of a user interface window W2 that allows the user to set a preferred patch number. This window W2 is automatically displayed by the user interface display module 101 (FIG. 1) when the test pattern is printed. The window W2 is provided with a plurality of buttons B11 to B13 for selecting a preferred patch number. When the user clicks one of these buttons B11 to B13, a preferred patch number is set in the EEPROM 58 (FIG. 3) of the printer 20. The patch number may be registered in the EEPROM 58 as a replacement for the reference correction value set in step S3 in FIG. 6, or may be registered in the EEPROM 58 as a value for further correcting the reference correction value. Further, the patch number indicating the feed correction value by the user may be registered in the printer driver 96 instead of the EEPROM 58.
[0047]
In step S14 of FIG. 8, actual printing is executed in accordance with a user instruction. At this time, the operation of the paper feed motor 31 (FIG. 3) is controlled in accordance with the paper feed correction value set in step S13.
[0048]
As described above, in this embodiment, the paper feed error caused by the manufacturing error of the paper feed roller 24 is corrected for each printer. Therefore, the paper feed error during actual printing can be reduced, and the image quality can be improved. Printing can be realized. Further, the tolerance of the manufacturing error of the paper feed roller 24 can be increased, and the yield of the paper feed roller 24 is increased accordingly, so that the cost of the printer 20 can be reduced. Furthermore, since the user can also correct the paper feed error, even when the paper feed error changes over time due to wear of the gear train 40 (FIG. 4) of the paper feed mechanism, the error is compensated and high-quality printing is performed. Can be done.
[0049]
C. Details on how to print test patterns and how to determine paper feed correction values:
FIG. 11 shows an example of paper feeding used when printing a test pattern in step S2 of FIG. 6 and step S12 of FIG. Here, the positions of the print head 36 in the sub-scanning direction in the five passes 1 to 5 are shown. Here, “pass” means one main scan. In FIG. 11, for convenience of illustration, the number of nozzles of the print head 36 is drawn small, the number of black nozzles (indicated by white circles) is nine, and the number of chromatic color nozzles for one color is three. It is said that. Further, since the composite black gray patch shown in FIG. 7 is reproduced, nine black nozzles are not used. In other words, three nozzles are used for three colors of CMY.
[0050]
Here, since the nozzle pitch k is 4 dots, there is a gap of 3 lines between raster lines (main scanning lines) recorded in one pass. The paper feed amounts F1, F2, and F3 after passes 1, 2, and 3 are each one dot. Therefore, in passes 2 to 4, three lines of gaps that were not recorded in pass 1 are recorded. The raster line positions recorded in passes 1 to 4 are shown at the right end of FIG. As can be understood from this, in the passes 1 to 4, twelve continuous lines are recorded with one color of ink. Here, the twelve lines recorded in yellow are referred to as “yellow color band YCB”. Similarly, twelve lines recorded in magenta are called “magenta color band MCB”, and twelve lines recorded in cyan are called “cyan color band CCB”. These color bands are the same as the raster lines printed in one pass for each ink using a virtual dense nozzle row having 12 nozzles arranged with a nozzle pitch k of 1 dot. In other words, passes 1 to 4 are equivalent to a single pass using a dense nozzle array as shown at the right end of FIG.
[0051]
The paper feed amount F4 after pass 4 is 9 dots. By this paper feed, the uppermost nozzle of the yellow nozzle of the print head 36 is positioned at the uppermost end of the area where no yellow dot is recorded. The same applies to the nozzles at the upper ends of the other inks. Such a recording method is substantially equivalent to a recording method in which the virtual dense nozzle row shown at the right end of FIG. 11 is used and paper is fed by a bandwidth Lc1 for one color for each pass. I understand that. Therefore, paper feeding as shown in FIG. 11 is called “pseudo band feeding”.
[0052]
The feed amount F4 after pass 4 is equal to the value obtained by subtracting the total value (= 3 dots) of the previous three feed amounts F1 to F3 from the band width Lc1 for one color. Therefore, the total ΣFi of the feed amounts F1 to F4 for four times is equal to the band width Lc1 for one color. Note that the band width Lc1 for one color is equal to the range of one chromatic color nozzle array, which is a value N × k (== multiplying the number of nozzles N (= 3) and the nozzle pitch k (= 4). 12).
[0053]
In FIG. 11, for convenience of explanation, the number N of nozzles per color is set to 3, but the number N of nozzles per color is actually several tens or more. FIG. 12 shows an example of the paper feed amount used for actual printing using the print head 36 shown in FIG. Such an actual paper feed amount is preset in the printer driver 96. FIG. 12A shows an example of pseudo band feeding. In the color mode, the third feed amount F1 to F3 is 1 dot, and the fourth feed amount F4 is 237 dots. The total of these four feed amounts F1 to F4 is equal to the band width N × k (= 240) for one color. The number N of nozzles used for one color is 60. FIG. 11 is a simplified drawing of this color mode paper feed.
[0054]
In the monochrome mode of FIG. 12A, 180 black nozzles are used. The third feed amount F1 to F3 is 1 dot, and the fourth feed amount F4 is 717 dots. The total of these four feed amounts F1 to F4 is equal to the black nozzle bandwidth N × k (= 720).
[0055]
FIG. 12B shows an example of the paper feed amount in the normal interlace recording mode printing that is not pseudo band feeding. Here, “interlace recording mode” means a printing method in which a gap is generated between raster lines recorded in one pass. In other words, a printing method using a print head having a nozzle pitch k of 2 dots or more corresponds to the “interlace recording mode”.
[0056]
In the example of FIG. 12B, each feed amount Fi is set to a constant integer value equal to the number of used nozzles N and relatively prime to the nozzle pitch k. Here, when two integers are “relative to each other”, it means that there is no common divisor other than 1. In the color mode in the example of FIG. 12B, since the number N of used nozzles is 59, one of the 60 nozzles of each color is not used. In the monochrome mode, since the number N of used nozzles is 179, one of the 180 black nozzles is not used. In this specification, sub-scanning in which the paper feed amount Fi is a constant value is referred to as “regular feed”. It is also possible to use “anomalous feed” that employs a plurality of different values as the paper feed amount Fi.
[0057]
When a test pattern is printed using pseudo band feeding as shown in FIG. 11 and FIG. 12A, banding is likely to occur at the boundary of each color band due to paper feeding error, so it is easy to detect paper feeding error. There is a feature. Here, “banding” means a streak-like image degradation portion along the main scanning direction. For example, in the uppermost test pattern of FIG. 7, thin banding (white stripes) occurs at the boundary between the upper half and the lower half, and in the lowermost test pattern, dark banding (black stripes) occurs. White streaks occur when the paper feed is insufficient, and black streaks occur when the paper feed is excessive. Banding detection may be performed with the naked eye, or may be performed automatically by imaging a test pattern and performing image processing.
[0058]
As described above, when the test pattern (color patch) is printed by the pseudo band feed using the print head 36 having the nozzle pitch k of 2 or more, there is an advantage that the paper feed error can be easily detected. In this sense, it is preferable to print the test pattern using the pseudo band feed shown in FIG. 12A rather than the interlace recording mode printing which is not the pseudo band feed shown in FIG. Further, the pseudo band feeding in FIG. 12A is a paper feeding that is most frequently used when printing an actual printed matter in the printer 20 having the print head 36 shown in FIG. Therefore, the pseudo band feed shown in FIG. 12A is preferable also in the sense that the test pattern is printed using the paper feed most frequently used in actual printing as it is.
[0059]
The test pattern print signal TPS representing the test pattern is registered in the printer driver 96 (FIG. 1) and stored as a file for the printer driver 96 in the hard disk 92 of the computer 90. The test pattern print signal TPS has the same format as the print data PD (raster data + paper feed amount) transmitted from the printer driver 96 to the printer 20. However, the test pattern print signal TPS is preferably stored in a data-compressed format. When the user gives an instruction to print a test pattern, the test pattern print signal TPS is called by the test pattern supply module 102, decompressed as necessary, and transferred to the printer 20. As described above, in this embodiment, the test pattern print signal TPS is registered in the printer driver 96 in a format that can be transferred to the printer 20 as it is, so that there is an advantage that the test pattern can be printed in a short time. . This advantage is particularly remarkable when a test pattern having a two-dimensional spread is used, such as the color patch shown in FIG.
[0060]
In this embodiment, since the test pattern print signal TPS is stored as a file of the printer driver 96, when the specification of the printer driver 96 is changed, the test pattern print signal TPS is simultaneously sent together with the printer driver 96. There is an advantage that the version can be upgraded. Accordingly, a test pattern suitable for the paper feed amount actually used by the printer driver 96 can be used for correcting the paper feed amount.
[0061]
As shown in FIG. 12, this printer 20 can use a plurality of types of paper feed amounts. Therefore, in this embodiment, the correction value δ is determined for each paper feed amount.
[0062]
FIG. 13A shows the relationship between the paper feed amount F and the correction value δ. Here, the unit of the feed amount F is [dot], and the unit of the correction value δ is [pulse]. FIG. 13B shows a unit of the correction value δ. Here, it is assumed that one cycle of the A-phase and B-phase signals of the rotary encoder 46 (FIG. 4) of the paper feed mechanism corresponds to 1440 dpi. In a normal encoder, the phases of the A phase signal and the B phase signal are shifted by ¼ period, so that the position can be commanded in units of ¼ of one period (1440 dpi). Therefore, in this embodiment, a distance corresponding to a quarter period of one period (1440 dpi) of the A-phase and B-phase signals of the encoder 46 is used as a unit [pulse] of the correction value δ.
[0063]
However, other values may be adopted as the unit of the correction value δ. For example, 1/2 of one cycle of the output signal of the encoder may be adopted as the unit of the correction value δ. When a step motor is used as the paper feed motor 31, one step pulse can be used as a unit of the correction value δ.
[0064]
Black dots in FIG. 13A indicate correction values δ for four feed amounts F (59 dots, 179 dots, 237 dots, and 717 dots). These four feed amounts F are the feed amounts used in the four examples shown in FIGS. 11 (A) and 11 (B). However, the one-dot feed is omitted in FIG. 13A because the correction value is almost zero.
[0065]
The following various methods can be used as a method of determining the relationship between the plurality of feed amounts F and their correction values δ.
[0066]
Method 1: A test pattern is actually printed using a plurality of feed amounts, and a correction value δ for each feed amount is determined.
Method 2: A test pattern is printed using a representative feed amount among a plurality of feed amounts to determine its correction value δ, and correction values for other feed amounts are predicted based on this.
[0067]
When the method 1 is adopted, for example, test patterns are printed in four types of modes shown in FIGS. 12A and 12B, and the respective correction values δ (specifically patch numbers) are determined. Just do it.
[0068]
In Method 2, there are a case where only one value is used as a representative feed amount and a case where two or more values are used. When only one feed amount F is used as a representative feed amount, for example, a test pattern is printed only for the maximum value (= 717) of the feed amounts F shown in FIGS. And the other three feed amount correction values are predicted from this correction value. Prediction of the correction value of the feed amount other than the representative feed amount is performed by presetting the shape of a characteristic curve (prediction curve) such as a curve G1 as shown in FIG. It is possible to do this. In general, a correction value for a feed amount other than a typical feed amount may be predicted according to a predetermined prediction curve. Here, the “prediction curve” has a broad meaning including a straight line.
[0069]
The reason why it is preferable to use the maximum value of the feed amount used in the printer as a typical feed amount is that the correction value increases as the feed amount increases. When two or more values are used as typical feed amounts, for example, the maximum feed amount used in the printer and any other one feed amount are used.
[0070]
In this way, if a correction value is determined by printing a test pattern only for a representative feed amount and a correction value for another feed amount is predicted from the correction value for a representative feed amount, the test pattern is It is possible to reduce the amount of time, and it is possible to shorten the time required for correction.
[0071]
FIG. 14 is a table showing paper feed correction values determined for each type of printing paper. In this table, correction values δ for four feed amounts F are registered for each of the four types of printing paper. As can be understood from this example, since the slipperiness varies depending on the type of printing paper, it is preferable to register the correction value δ for each type of printing paper. In this way, it is possible to perform an appropriate paper feed correction for each type of printing paper.
[0072]
It is not necessary to actually measure the correction value δ for each printing paper. For example, the correction value may be actually measured for only one predetermined type of a plurality of types of printing paper, and the correction value for other printing paper may be predicted from now on. Specifically, for example, the correction value δ is actually measured for plain paper, and the correction values for other printing papers can be obtained by multiplying the correction values for plain paper by a certain coefficient. In general, correction values relating to different types of printing paper have a substantially constant relationship, and are unlikely to deviate greatly from this, so such a prediction is possible. In this way, it is possible to perform appropriate paper feed correction for other printing papers by only obtaining correction values for one type of printing paper. In particular, there is an advantage that it is possible to reduce the trouble of printing the test pattern by the user of the printer 20 and reduce the complexity of the paper feed correction.
[0073]
FIG. 15 is a graph showing the relationship between the paper feed speed V and the correction value δ. As shown here, the correction value of the paper feed amount tends to increase as the paper feed speed V increases. Therefore, when the paper feed speed varies depending on the print mode, it is preferable to set the paper feed correction value δ according to the paper feed speed. In this case as well, it is possible to actually measure a correction value for one paper feed speed and to predict a correction value for another paper feed speed.
[0074]
The correction value δ shown in FIGS. 13 to 15 is registered in a nonvolatile memory (EEPROM 58) in the printer 20 or a printer driver 96 (specifically, a hard disk of the computer 90). During actual printing, a value obtained by correcting the paper feed amount F with the correction value δ is given as a command value from the system controller 54 to the sub-scanning drive circuit 62.
[0075]
FIG. 16 shows two transmission methods related to the paper feed amount F and its correction value δ. In the first method shown in FIG. 16A, only the normal feed amount F that has not been corrected is transmitted from the printer driver 96 to the system controller 54. The paper feed controller 54a of the system controller 54 reads the correction value δ from the EEPROM 58, corrects the feed amount F, and supplies the corrected feed amount to the sub-scanning drive circuit 62 as a command value. In the second method shown in FIG. 16B, the corrected feed amount F ′ is transmitted from the printer driver 96 to the system controller 54. The paper feed controller 54a of the system controller 54 supplies the corrected feed amount F ′ to the sub-scanning drive circuit 62 as a command value.
[0076]
As described above, in this embodiment, the test pattern is printed using the same interlaced recording mode as that used in actual printing, and the paper feed amount is corrected using the correction value δ determined according to the result. Therefore, it is possible to perform high quality printing with little paper feed error. In particular, since a correction value is registered for each type of printing paper, it is possible to compensate for the difference in paper feed amount depending on the printing paper used.
[0077]
D. Test pattern print signal configuration:
FIG. 17 shows an example of a test pattern print signal for reproducing the patch of patch number 2 shown in FIG. In FIG. 17, the virtual dense nozzle row 36a shown in FIG. 11 is shown. As described with reference to FIG. 11, the dense nozzle row 36a is constituted by four passes. It can be considered that the dense nozzle row 36a is sub-scan fed by the band width Lc1 for one color.
[0078]
The right half of FIG. 17 shows the configuration of raster data RD1 for forming one color patch with 24 raster lines L1 to L24 using such a dense nozzle row 36a. According to the raster data RD1, dots of three colors Y, M, and C are recorded on all the raster lines L1 to L24, respectively. In FIG. 18, for convenience of illustration, the Y, M, and C dot formation positions are depicted as shifted, but actually, dots of each color are formed at the same pixel position.
[0079]
When such a test pattern print signal is used, when the paper feed error is 0, a patch without banding is printed like the patch of patch number 2 shown in FIG. Further, when the paper feed error becomes positive, white stripes are generated at the band boundary. Conversely, when the paper feed error becomes negative, black stripes are generated at the band boundary. In other words, in the print signal of FIG. 17, a paper feed error is simulated by the difference in the paper feed amount of each patch.
[0080]
FIG. 18 shows an example of a test pattern print signal for reproducing the patch with patch number 1 shown in FIG. In this print signal, the paper feed amount is the same as that shown in FIG. 17, but the raster data representing the dot formation state in each pixel is different from that in FIG. That is, raster data is formed on the raster line L13 immediately below the band boundary so that no Y, M, or C ink dots are formed. In other words, in the print signal of FIG. 18, a paper feed error is simulated by the difference in raster data of each patch. When such a test pattern print signal is used, when the paper feed error is 0, a patch with white stripes is printed like the patch of patch number 1 shown in FIG. Therefore, if there is a paper feed error for one dot during actual printing, a clean patch without white stripes is reproduced.
[0081]
FIG. 19 is an explanatory diagram of a configuration example of a test pattern print signal. The print signal for each patch includes a paper feed amount and raster data. In the first example shown in FIG. 19A, the print signals for each patch have the same paper feed amount and different raster data. As the paper feed amount, the value in the color mode of the paper feed example 1 shown in FIG. 12 is used. The print signals shown in FIGS. 17 and 18 correspond to the print signals in FIG.
[0082]
In the second example shown in FIG. 19B, the print signals for each patch have the same raster data and different paper feed amounts. That is, as the raster data, the data having no inherent banding shown in FIG. 17 is used. As for the paper feed amount, the print signal for each patch has a different value for the fourth feed amount F4, one dot at a time.
[0083]
Each of the print signals in FIGS. 19A and 19B can print the three patches shown in FIG. However, as shown in FIG. 19A, when printing each patch using the same paper feed amount and raster data simulating the sub-scan feed error, the unit of the paper feed amount correction value is a raster. Limited to an integral multiple of the line pitch. On the other hand, as shown in FIG. 19B, when each patch is printed using the same raster data and the paper feed amount simulating the sub-scan feed error, as described in FIG. The unit of the amount correction value can be set to a unit finer than the raster line pitch.
[0084]
E. Variation:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
[0085]
E1. Modification 1:
In the above embodiment, a color ink jet printer has been described. However, the present invention can also be applied to a monochrome printer, and can also be applied to printers other than the ink jet system. The present invention is generally applicable to a printing apparatus that records an image on a print medium, and can also be applied to, for example, a facsimile machine and a copier.
[0086]
E2. Modification 2:
In the above embodiment, the case where the nozzle pitch k is 4 dots has been described. However, the present invention is generally applicable to the case where printing in the interlaced recording mode is performed using a print head having a nozzle pitch k of 2 dots or more. is there. Generally, the pseudo band feed is achieved by performing the sub-scan of 1 dot feed (k−1) times and then performing the sub-scan of {N × k− (k−1)} dots once. At this time, dot recording by main scanning is performed between each sub-scan feed. The unit “1 dot” means the dot pitch in the sub-scanning direction.
[0087]
E3. Modification 3:
In the above embodiment, as shown in FIG. 5, the case where the print head 36 having the two-row configuration of the black nozzle row and the color nozzle row is used has been described. The present invention can also be applied to print heads that are in the sub-scanning direction position and are sequentially arranged in the main scanning direction.
[0088]
E4. Modification 4:
In the above embodiment, the color patch is used as the test pattern. However, any pattern other than the color patch can be used as the test pattern. However, the use of color patches has the advantage that banding due to paper feed errors can be easily detected.
[0089]
In the above embodiment, the correction value is determined by one type of test pattern, but the correction value may be determined by using a plurality of types of test patterns. For example, the coarse correction value may be determined using the first test pattern for coarse adjustment, and the final fine correction value may be determined using the second test pattern for fine adjustment. For example, a coarse correction value can be set at an interval of 10 steps, and a fine correction value can be set at an interval of 1 step. In this way, if a plurality of adjustments are performed, it is possible to efficiently determine a fine correction value.
[0090]
E5. Modification 5:
In the above embodiment, the gray patch reproduced with composite black is used as the color patch of the test pattern. However, a color patch other than this can be used. For example, it is also possible to use a gray patch reproduced only with black ink, or a single color patch reproduced with cyan ink or magenta ink. Alternatively, it is also possible to use secondary color patches that are reproduced using two of the three colors of cyan, magenta, and yellow. As the ink used for reproducing the color patch, an ink having a color component for which image quality improvement is desired by correcting a paper feed error is selected. In other words, if a color patch is reproduced using ink of a color component whose image quality is to be improved by correcting the paper feed error, by correcting the paper feed error using the color patch, an image in which the ink is often used is corrected. It is possible to improve the image quality.
[0091]
E6. Modification 6:
In the above embodiment, the correction value is determined by observing the test pattern by human beings. Instead, the image quality measurement unit that mechanically measures the image quality of the test pattern is used to reduce the image quality of the sub-scan feed error. It is also possible to measure the influence of the correction and the correction unit corrects the sub-scan feed according to the measurement result. In this way, it is possible to appropriately correct the sub-scan feed error without requiring manual work.
[0092]
E7. Modification 7:
In the above embodiment, printing is performed according to the interlaced recording mode, but the present invention can also be applied to the case where printing is performed according to the non-interlaced recording mode. The “non-interlaced recording mode” means a printing method performed using nozzles arranged at a nozzle pitch equal to the dot pitch in the sub-scanning direction (that is, the main scanning line pitch).
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a printing system as an embodiment of the present invention.
FIG. 2 is a schematic perspective view showing a main configuration of the color inkjet printer 20;
FIG. 3 is a block diagram showing an electrical configuration of the printer 20;
FIG. 4 is a perspective view showing a configuration of a sub-scanning drive mechanism.
FIG. 5 is an explanatory diagram showing nozzle arrangement on the lower surface of the print head.
FIG. 6 is a flowchart illustrating a procedure for paper feed correction before shipment of the printer.
FIG. 7 is an explanatory diagram showing an example of a test pattern.
FIG. 8 is a flowchart illustrating a procedure for paper feed correction by a user.
FIG. 9 is an explanatory diagram illustrating an example of a user interface window W1 that allows a user to issue a test pattern print instruction;
FIG. 10 is an explanatory diagram showing an example of a user interface window W2 that allows a user to set a patch number.
FIG. 11 is an explanatory diagram illustrating an example of paper feeding used when printing a test pattern.
12 is an explanatory diagram showing an example of paper feeding when the print head of FIG. 5 is used.
FIG. 13 is an explanatory diagram showing a relationship between a paper feed amount F and a correction value δ.
FIG. 14 is an explanatory diagram showing a paper feed correction value determined for each type of printing paper.
FIG. 15 is a graph showing the relationship between the paper feed speed V and the correction value δ.
FIG. 16 is an explanatory diagram showing two transmission methods related to a paper feed amount F and its correction value δ.
FIG. 17 is an explanatory diagram showing the contents of a test pattern print signal for patch number 2;
FIG. 18 is an explanatory diagram showing the contents of a test pattern print signal for patch number 1;
FIG. 19 is an explanatory diagram illustrating a configuration example of a test pattern print signal.
[Explanation of symbols]
20 ... Color inkjet printer
21 ... CRT
22 ... Paper stacker
24. Paper feed roller
25. Followed roller
26 ... Platen
28 ... Carriage
30 ... Carriage motor
31 ... Paper feed motor
32 ... Traction belt
34 ... Guide rail
36 ... Print head
40 ... Geartrain
42: Paper discharge roller
44 ... Giza Rolla
46: Rotary encoder
46a ... code plate
46b ... Photo sensor
50: Receive buffer memory
52 ... Image buffer
54 ... System controller
54a: Paper feed control unit
56 ... Main memory
58… EEPROM
61. Main scan driving circuit
62 ... Sub-scanning drive circuit
63. Head drive circuit
90 ... Computer
91 ... Video driver
92: Hard disk
95 ... Application program
96 ... Printer driver
97 ... Resolution conversion module
98 ... Color conversion module
99 ... Halftone module
100 ... Rasterizer
101 ... User interface display module
102 ... Test pattern supply module

Claims (7)

A method of correcting a sub-scan feed amount of a print medium in a printing apparatus that performs printing by recording ink dots on the print medium while moving the print head in the main scanning direction,
(A) a step of actually measuring the influence on the image quality due to the sub-scan feed error caused by the manufacturing error of the paper feed roller for feeding the print medium in the sub-scan direction for each printing device;
(B) a step of correcting the sub-scan feed amount based on the actual measurement result of the step (a) when printing an image;
With
The step (a)
A step of setting a plurality of feed amounts used in actual printing as the feed amount of the sub-scan feed of the print medium;
A different correction value is used as a test pattern for determining a correction value for the representative feed amount to be printed using at least one representative feed amount selected in advance from the plurality of feed amounts. Printing a test pattern including a plurality of color patches each printed;
Predicting other feed amount correction values based on the representative feed amount correction values set according to the test pattern printing results;
Including
The step (b) is a step of correcting the sub-scan feed amount based on the correction value related to the representative feed amount and the correction value predicted for the other feed amount when printing an image. Including
The correction value for the other feed amount is predicted according to a predetermined prediction curve that is not a straight line from the correction value for the representative feed amount. The correction method according to claim 1,
The print head has a plurality of nozzles arranged in the sub-scanning direction at a nozzle pitch k times (k is an integer of 2 or more) in the sub-scanning direction substantially perpendicular to the main scanning direction.
The plurality of feed amounts are feed amounts used for printing in the interlaced recording mode,
The test method printing is performed according to an interlace recording mode. The correction method according to claim 1 or 2,
The representative feed amount includes a maximum value among the plurality of feed amounts. The correction method according to any one of claims 1 to 3,
The print head has a plurality of nozzles arranged in the sub-scanning direction at a nozzle pitch k times (k is an integer of 2 or more) in the sub-scanning direction substantially perpendicular to the main scanning direction.
The correction method, wherein the printing of the image in the step (b) is executed according to an interlace recording mode. The correction method according to any one of claims 1 to 3,
The correction method, wherein the step of printing the test pattern can be executed according to a command from a user of the printing apparatus. An apparatus for correcting a sub-scan feed amount of a print medium in a printing apparatus that performs printing by recording ink dots on the print medium while moving the print head in the main scanning direction,
An image quality measuring unit that measures the influence on the image quality due to the sub-scan feed error caused by the manufacturing error of the paper feed roller for feeding the print medium in the sub-scan direction for each printing device;
When printing an image, a correction unit that corrects the sub-scan feed amount based on the actual measurement result;
With
The image quality measurement unit
Means for setting a plurality of feed amounts used in actual printing as the feed amount of the sub-scan feed of the print medium;
A different correction value is used as a test pattern for determining a correction value for the representative feed amount to be printed using at least one representative feed amount selected in advance from the plurality of feed amounts. Means for printing a test pattern including a plurality of color patches each printed;
Means for predicting a correction value for another feed amount based on the correction value for the representative feed amount set according to the print result of the test pattern;
Including
The correction unit corrects the sub-scan feed amount based on the correction value related to the representative feed amount and the correction value predicted for the other feed amount when printing an image,
The correction value for the other feed amount is predicted from the correction value for the representative feed amount according to a predetermined prediction curve that is not a straight line. A computer program for causing a computer including a printing apparatus that performs printing by recording ink dots on a print medium while moving the print head in the main scanning direction to correct the sub-scan feed amount of the print medium. ,
(A) a step of actually measuring the influence on the image quality due to the sub-scan feed error caused by the manufacturing error of the paper feed roller for feeding the print medium in the sub-scan direction for each printing device;
(B) a step of correcting the sub-scan feed amount based on the actual measurement result of the step (a) when printing an image;
A program for causing the computer to realize
The step (a)
A step of setting a plurality of feed amounts used in actual printing as the feed amount of the sub-scan feed of the print medium;
A different correction value is used as a test pattern for determining a correction value for the representative feed amount to be printed using at least one representative feed amount selected in advance from the plurality of feed amounts. Printing a test pattern including a plurality of color patches each printed;
Predicting other feed amount correction values based on the representative feed amount correction values set according to the test pattern printing results;
Including
The step (b) is a step of correcting the sub-scan feed amount based on the correction value related to the representative feed amount and the correction value predicted for the other feed amount when printing an image. Including
The other feed amount correction value is predicted from the representative feed amount correction value according to a predetermined prediction curve that is not a straight line.

Images