JP2003011347A - Sheet feed error correction in printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for enhancing the image quality by correcting the sheet feed error of a printer. SOLUTION: Effect of sub-scanning feed error due to production error of a sheet feed roller for feeding a print medium in the sub-scanning direction onto the image quality is measured actually for individual printers. At the time of printing an image, sub-scanning feeding amount is corrected based on the measurements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for printing by recording ink dots on a print medium while moving a print head in the main scanning direction.

[0002]

2. Description of the Related Art As an output device of a computer, an ink jet printer or a laser printer which ejects ink from a head is widely used. In particular, in recent years, color printers using color ink have been widely used.

Various print media for ink jet printers are commercially available. Different print media have different coloring properties of inks, and therefore, there is a large difference in the obtained image quality. The type of print medium also affects the accuracy of the sub-scan feed of the print medium (hereinafter referred to as “paper feed”). For example, a print medium whose surface is slippery and a print medium whose surface is hard to slip may have considerably different actual feed amounts even if the same feeding operation is performed. Also, the paper feed accuracy is
It tends to vary considerably from printer to printer.

The quality of paper feeding has a great influence on the image quality. However, in a printer that performs printing in the so-called interlaced recording mode, it is possible to suppress deterioration of image quality due to a paper feed error to some extent by appropriately setting the paper feed amount. Here, the “interlaced recording mode” means a printing method performed using a print head having nozzles arranged at a nozzle pitch twice or more the dot pitch in the sub-scanning direction (that is, main scanning line pitch). There is. When such a print head is used, there is a gap between main scan lines (raster lines) that can be printed by one main scan. Then, 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 interlaced recording mode. Therefore, conventionally, by appropriately selecting the paper feed amount in the interlace recording mode, the influence of the image quality due to the variation of the paper feed accuracy is suppressed to a small level.

[0005]

For the above reasons, in the printer of the interlaced recording mode, direct correction of the paper feed error has not been considered so much. However, with the recent progress in high image quality of printers, even in printers that perform printing in the interlace recording mode, there has been a demand for further improving the image quality by appropriately correcting the paper feed error. Such a demand is increasing not only for printers using only the interlaced recording mode but also for printers using the non-interlaced recording mode.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a technique capable of improving the image quality by correcting the paper feed error of the printer.

[0007]

In order to achieve the above-mentioned object, the method of the present invention prints by recording ink dots on a print medium while moving the print head in the main scanning direction. A method of correcting a sub-scan feed amount of a print medium in a printing apparatus for performing (a) 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 Impact
And a step of correcting the sub-scan feed amount based on the actual measurement result of the step (a) when printing an image. To do.

According to this method, the influence of the sub-scan feed error due to the manufacturing error of the paper feed roller on the image quality is measured for each printing apparatus, and the sub-scan feed amount is corrected based on the measured result. Therefore, even when the allowable value of the manufacturing error of the paper feeding roller is large, it is possible to correct the paper feeding error due to it and improve the image quality.

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) the dot pitch in the sub-scanning direction substantially perpendicular to the main scanning direction. However, the printing of the image in the step (b) may be executed according to the interlace recording mode.

With this configuration, even in a printer that performs printing in the interlaced recording mode, it is possible to appropriately correct the sub-scan feed error due to the manufacturing error of the paper feed roller.

The step (a) includes a step of printing a predetermined test pattern used for measuring the influence of the sub-scan feed error on the image quality, and the step of printing the test pattern includes: It may be preferably executed in response to a command from a user of the printing device.

According to this configuration, even if the paper feed error changes over time, it is possible to correct it and improve the image quality.

The present invention can be implemented in various forms. For example, a sub-scan feed amount (paper feed amount) correction method and device, a sub-scan feed control method and device, and a sub-scan feed device. Printing method and apparatus in consideration of correction of amount, printing control apparatus and method for controlling printing apparatus in consideration of correction of sub-scan feed amount, computer program for realizing those methods and apparatus, and recording the computer program It can be realized in various forms such as a recording medium, a data signal including a computer program thereof, and embodied in a carrier wave.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in the following order based on examples. A. Overall configuration of device: B. General procedure for paper feed correction: C. Details of test pattern printing method and paper feed correction value determination method: D. Structure of test pattern print signal: E. Modification:

A. Overall Configuration of Apparatus: FIG. 1 is a block diagram showing the configuration of a printing system as an embodiment of the present invention. The printing system includes a computer 90 and a color inkjet printer 20. In addition,
A printing system including the printer 20 and the computer 90 can be called a “printing device” in a broad sense.

In the computer 90, the application program 9 is executed under a predetermined operating system.
5 is working. A video driver 91 and a printer driver 96 are incorporated in the operating system, and the print data PD to be transferred to the printer 20 is output from the application program 95 via these drivers. An application program 95 for retouching an image performs desired processing on an image to be processed, and also a video driver 91.
An image is displayed on the CRT 21 via.

When the application program 95 issues a print command, the printer driver 9 of the computer 90
6 receives the image data from the application program 95 and converts it into print data PD to be supplied to the printer 20. Inside the printer driver 96, a resolution conversion module 97, a color conversion module 98,
Halftone module 99 and rasterizer 100
And a user interface display module 101,
A test pattern supply module 102 and a color conversion lookup table LUT are provided.

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 whose resolution has been converted in this way is still image information composed of three color components of RGB. Color conversion module 98
Refers to the color conversion lookup table LUT,
The RGB image data is converted into multi-tone data of a plurality of ink colors that can be used by the printer 20 for each pixel.

The color-converted multi-tone data is, for example, 25
It has 6 gradation values. The halftone module 99 executes so-called halftone processing to generate halftone image data. The halftone image data is sorted by the rasterizer 100 in the order of data to be transferred to the printer 20, and the final print data PD
Is output as. The print data PD includes raster data indicating the dot formation state during each main scan and data indicating the sub-scan feed amount.

User interface display module 1
01 has a function of displaying various user interface windows related to printing, and a function of receiving user input in those windows.

The test pattern supply module 102 is
It has a function of reading the test pattern print signal TPS used to determine the correction value of the sub-scan feed amount (also referred to as “paper feed amount”) from the hard disk 92 and supplying it to the printer 20. If the test pattern print signal TPS is stored as compressed data,
It has a function of expanding the compressed data.

The printer driver 96 sends the print data PD and the test pattern print signal TPS to the printer 20.
Corresponds to a program for realizing the function to be supplied to. The program for realizing the functions of the printer driver 96 is supplied in the form recorded in a computer-readable recording medium. Examples of such a recording medium include a flexible disk, a CD-ROM, a magneto-optical disk, an IC card, a ROM cartridge, a punch card, a printed matter on which codes such as a bar code are printed, and an internal storage device (RAM, ROM, etc.) of a computer. memory)
Also, various computer-readable media such as an external storage device can be used. It is also possible to download such a computer program to the computer 90 via the Internet.

The computer 90 equipped with the printer driver 96 uses the print data PD and the test pattern print signal T.
It functions as a print control device that supplies PS to the printer 20 to perform printing.

FIG. 2 shows a color ink jet printer 2.
It is a schematic perspective view which shows the main structures of 0. The printer 20 includes a paper stacker 22, a paper feed roller 24 driven by a step motor (not shown), a platen 26,
The carriage 28 includes a carriage motor 30, a traction belt 32 driven by the carriage motor 30, and a guide rail 34 for the carriage 28. A print head 36 having a large number of nozzles is mounted on the carriage 28.

The printing paper P is wound from the paper stacker 22 by the paper feeding roller 24 and is fed on the surface of the platen 26 in the sub-scanning direction. The carriage 28 is pulled by the pull belt 32 driven by the carriage motor 30 and moves along the guide rail 34 in the main scanning direction. The main scanning direction is perpendicular to the sub scanning direction.

FIG. 3 is a block diagram showing the electrical construction of the ink jet printer 20. This printer 20
Is a reception buffer memory 50 that receives signals supplied from the 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 E
And an EPROM 58. 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. .

The main scanning drive circuit 61, the carriage motor 30, the traction belt 32 (FIG. 2), and the guide rail 34.
Constitutes a main scanning drive mechanism. Further, the sub-scanning drive circuit 62, the paper feed motor 31, the paper feed roller 24
(FIG. 2) constitutes a sub-scanning drive mechanism (or referred to as a “feed mechanism”).

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 the necessary information from the print data from the reception buffer memory 50, and based on this, the drive circuits 61, 62, 6
Send a control signal to 3.

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 receives the image buffer 52 according to the control signal from the system controller 54.
The print data of each color component is read out from, and the nozzle array of each color provided in the print head 36 is driven accordingly.

FIG. 4 is a perspective view showing the structure of the sub-scanning drive mechanism. The power of the paper feed motor 31 is the gear train 4
It is transmitted to the paper feed roller 24 and the paper discharge roller 42 via 0. The paper feed roller 24 is provided with a driven roller 25, and the paper discharge roller 42 is also provided with a serrated roller 44 as a driven roller thereof. The printing paper P is sent while being nipped by these rollers and moves on the platen 26.

A code plate 46a is provided on the shaft of the paper feed roller 24.
A rotary encoder 46 including a photo sensor 46b and a photo sensor 46b is provided. Paper feed amount (sub-scan feed amount)
Is determined according to the pulse signal from the rotary encoder 46.

FIG. 5 is an explanatory view showing the nozzle arrangement on the lower surface of the print head 36. This print head 36
It has a black nozzle row and a color nozzle row that are respectively arranged on a straight line along the sub-scanning direction SS. In the present specification, the “nozzle row” is also referred to as a “nozzle group”.

There are 18 black nozzle rows (indicated by white circles).
It has zero 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 a dot pitch in the sub-scanning direction SS, and k is an integer. The dot pitch D in the sub-scanning direction is also equal to the pitch of the main scanning line (raster line). In the following, the nozzle pitch k
The integer k representing 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.

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.

The color nozzle row is a yellow nozzle group Y.
(Shown by white triangles), a magenta nozzle group M (shown by black squares), and a cyan nozzle group C (shown by white diamonds). In this specification, the nozzle group for chromatic color ink is also referred to as a “chromatic color nozzle group”. Each chromatic color nozzle group has 60 nozzles # 1 to # 60. The nozzle pitch of the chromatic color 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 positions as the nozzles of the black nozzle row.

During printing, ink droplets are ejected from each nozzle while the print head 36 moves together with the carriage 28 (FIG. 2) in the main scanning direction at a constant speed. However,
Depending on the printing method, not all nozzles are always used, and only some nozzles may be used.

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 CMY color, and 60 black nozzles are also used. The 60 black nozzles used in color printing are nozzles # 121 to # 180 arranged at the same sub-scanning position as the 60 cyan nozzles, for example.

B. General procedure for paper feed correction: As described below, the paper feed error can be corrected before the printer 20 is shipped, and can be corrected by the user after the shipment.

FIG. 6 is a flow chart showing the procedure of paper feed correction before the printer 20 is shipped. In step S1, the type of print paper (print medium) scheduled to be used in the printer 20 is sequentially selected. Examples of types of printing paper include plain paper, glossy film, photo paper, and roll-type photo paper. In step S2, the selected printing paper is set in the printer 20, and
Print a predetermined test pattern.

FIG. 7 shows an example of the 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 next to each color patch is associated with the paper feed correction value δ in advance. However, the paper feed correction value δ
Is only drawn for convenience, not actually printed. Each color patch has a uniform gray area C
It is a gray patch reproduced with composite black using MY ink. Such a gray patch reflects both the paper feed error and the dot position error of each color. The image quality of an actual printed matter affects not only the paper feed error but also the dot position error of each color. Therefore, from the viewpoint of improving the image quality, it is preferable to use a gray patch reproduced in composite black as a test pattern. However, as the test pattern, various patterns other than this can be used, and for example, other types of color patches, ruled line patterns, and the like can also be used. In the present specification, the "color patch" means
It means an image area reproduced in a substantially uniform color. Details of the test pattern printing method will be described later.

In the present specification, "composite black" means a gray color reproduced by using inks of three hues of CMY, and even if reproduced by using three or more kinds of inks. Good. For example, when dark and light inks are available for cyan and magenta, respectively, it is also possible to reproduce composite black using these four types of ink and five types of yellow ink.

The main cause of the paper feed error in the printer 20 is the 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 feeding error becomes positive, and if it is small, the feeding error becomes negative. In this embodiment, the correction of the paper feed error caused by the manufacturing error of the paper feed roller 24 is performed for each printer before shipping. 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. In addition, since the yield of the paper feed roller 24 increases as the allowable value for the manufacturing error of the paper feed roller 24 is relaxed, there is an advantage that the cost of the printer 20 decreases.

In step S3 of 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 to EEPRO of the printer 20.
Set in M58 (FIG. 3). In the example of FIG. 7, white streaks are generated in the uppermost color patch, and black streaks 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. It should be noted that the paper feed correction value set by the inspection before shipment is called a "reference correction value".

In step S4, all the printing papers scheduled to be used by the printer 20 are processed in step S1.
~ It is determined whether or not S3 is completed, and if not completed, the process returns to step S1. Here, "all the print sheets scheduled to be used in the printer 20" mean the sheet types 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 values are set for all types of printing paper.

FIG. 8 is a flow chart showing the procedure of paper feed correction by the user. In step S11, the user selects the type of print paper, and in step S12, a test pattern is printed by inputting a test pattern print command. FIG. 9 is an explanatory diagram showing an example of the user interface window W1 that allows the user to print a test pattern. This window W1 is
This is a utility window in the printer properties, and is provided with a button B1 for inputting a print instruction of 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 in the paper feed correction before shipping,
Alternatively, a different test pattern may be used. In this embodiment, the test pattern shown in FIG. 7 is also used for the paper feed correction by the user. The configuration of the test pattern print signal TPS will be described later.

In step S13 of FIG. 8, the color patch with the highest image quality is selected from the 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 preferable patch number.
This window W2 is used for the user interface display module 101 when the test pattern is printed.
(Fig. 1) automatically displays. The window W2 is provided with a plurality of buttons B11 to B13 for selecting a preferable patch number. When the user clicks any of these buttons B11-B13, the preferred patch number is the EEPROM of printer 20.
58 (FIG. 3). Note that the patch number may be registered in the EEPROM 58 as a substitute for the reference correction value set in step S3 of FIG. 6, or EEPRO may be registered as a value for further correcting the reference correction value.
It may be registered in M58. 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.

In step S14 of FIG. 8, actual printing is executed according to the user's instruction. At this time, the operation of the paper feed motor 31 (FIG. 3) is controlled according to the paper feed correction value set in step S13.

As described above, in this embodiment, since the paper feed error caused by the manufacturing error of the paper feed roller 24 is corrected for each printer, the paper feed error at the time of actual printing can be reduced, It is possible to realize high-quality printing. Further, the allowable value of the manufacturing error of the paper feed roller 24 can be increased, and accordingly, the paper feed roller 2
Since the yield of No. 4 is high, the cost of the printer 20 can be reduced. Further, since the user can correct the paper feed error, the gear train 40 of the paper feed mechanism can be used.
Even when the paper feed error changes over time due to wear or the like (FIG. 4), it is possible to compensate for the error and perform high-quality printing.

C. Details of test pattern printing method and paper feed correction value determination method: FIG. 11 shows step S2 of FIG.
8 shows an example of paper feed used when printing a test pattern in step S12 of FIG. Here, the print head 3 in five passes of pass 1 to pass 5
The positions of 6 in the sub-scanning direction are shown. Here, "pass" means one main scan. Note that in FIG. 11, the number of nozzles of the print head 36 is illustrated small for convenience of illustration, the number of black nozzles (indicated by white circles) is 9, and the number of chromatic color nozzles for one color is 3.
It is supposed to be an individual. 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 each of the three colors of CMY.

Here, since the nozzle pitch k is 4 dots, there is a gap of 3 lines between the raster lines (main scanning lines) recorded in one pass. Paths 1, 2, 3
The subsequent paper feed amounts F1, F2, and F3 are each 1 dot. Therefore, in passes 2 to 4, three lines in the gap that were not recorded in pass 1 are recorded. At the right end of FIG. 11, the raster line positions recorded in passes 1 to 4 are shown. As you can see, in passes 1-4,
Twelve consecutive lines are printed with one color of ink. Here, 12 lines recorded in yellow are referred to as "yellow color band YCB". Similarly,
The 12 lines recorded in magenta are called "magenta color band MCB", and the 12 lines recorded in cyan are called "cyan color band CCB". These color bands are the same as raster lines printed in one pass using a virtual dense nozzle row having 12 nozzles in which the nozzle pitch k is arranged at 1 dot for each ink. In other words, passes 1 to 4 are equivalent to one pass using the dense nozzle row as shown at the right end of FIG.

The paper feed amount F4 after pass 4 is 9 dots, and by this paper feed, the nozzle at the upper end 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 other inks. Such a recording method is shown in FIG.
It can be understood that it is substantially equivalent to the recording method in which the virtual dense nozzle row shown at the right end of is used to feed the paper by the band width Lc1 of one color for each pass. Therefore, the paper feeding as shown in FIG. 11 is called “pseudo band feeding”.

The feed amount F4 after pass 4 is equal to a value obtained by subtracting the total value (= 3 dots) of the feed amounts F1 to F3 of the previous three times from the band width Lc1 for one color. Therefore, the total ΣFi of the four feeding amounts F1 to F4 is equal to the band width Lc1 for one color. The band width Lc1 for one color
Is equal to the range of one chromatic nozzle row, which is also equal to the value N × k (= 12) obtained by multiplying the number of nozzles N (= 3) by the nozzle pitch k (= 4).

In FIG. 11, the number N of nozzles per color is set to 3 for the sake of convenience of explanation, 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. 12
(A) is an example of pseudo band feed. In the color mode, the feed amount F1 to F3 for three times is 1 dot, and the feed amount F4 for the fourth time is 237 dots. The total of these four feeding amounts F1 to F4 is the band width N × k for one color.
It is equal to (= 240). In addition, the number of nozzles used for one color N
Is 60. FIG. 11 is a simplified illustration of this color mode paper feed.

In the monochrome mode shown in FIG.
Zero black nozzles are used. Feed amount F3 three times
~ F3 is 1 dot, and the fourth feed amount F4 is 717
It is a dot. The total of these four feed amounts F1 to F4 is equal to the black nozzle band width N × k (= 720).

FIG. 12B shows an example of the paper feed amount in the printing in the normal interlace recording mode which is not the pseudo band feed. Here, the "interlaced printing mode" means a printing method in which a gap is created between raster lines printed in one pass. In other words, the printing method using the print head having the nozzle pitch k of 2 dots or more corresponds to the “interlace recording mode”.

In the example of FIG. 12B, each feed amount Fi is set to a constant integer value that is equal to the number of used nozzles N and is relatively prime to the nozzle pitch k. Here, two integers being “prime relative” means that they do not have a common divisor other than one. Note that in the color mode of the example of FIG. 12B, the number of used nozzles N is 59, so one of the 60 nozzles of each color is not used. Further, in the monochrome mode, the number of used nozzles N is 179, so one of the 180 black nozzles is not used. In this specification, such sub-scanning in which the paper feed amount Fi has a constant value is referred to as “constant feed”. It is also possible to use "irregular feeding" that employs a plurality of different values as the paper feeding amount Fi.

When a test pattern is printed by using the pseudo band feed as shown in FIGS. 11 and 12A, banding is likely to occur at the boundary of each color band due to a paper feed error. It is easy to detect. Here, “banding” means a streak-like image deterioration portion along the main scanning direction. For example,
In the uppermost test pattern in FIG. 7, thin banding (white stripes) is generated at the boundary between the upper half and the lower half, and in the lowermost test pattern, dark banding (black stripe) is generated. White streaks occur when the paper feed is insufficient, and black streaks occur when the paper feed is excessive.
The detection of banding may be performed with the naked eye, or may be automatically performed by capturing a test pattern and performing image processing.

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, 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 printing in the interlace recording mode which is not the pseudo band feed shown in FIG. 12B. The pseudo band feed shown in FIG. 12A is performed by the printer 20 having the print head 36 shown in FIG.
In the above, the paper feed is the most frequently used paper feed even when printing an actual printed matter. Therefore, the pseudo band feed shown in FIG. 12A is also preferable in that the test pattern is printed using the paper feed that is most frequently used in actual printing as it is.

The test pattern print signal TPS representing the test pattern is registered in the printer driver 96 (FIG. 1) and stored in the hard disk 92 of the computer 90 as a file for the printer driver 96. The test pattern print signal TPS is the print data P transmitted from the printer driver 96 to the printer 20.
It has the same format as D (raster data + paper feed amount). However, it is preferable that the test pattern print signal TPS is stored in a data compressed format. When the user gives an instruction to print the test pattern, the test pattern print signal TPS is called by the test pattern supply module 102, expanded 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 like the color patch shown in FIG.

Further, in this embodiment, the test pattern print signal TPS is stored as a file of the printer driver 96, so when the specifications of the printer driver 96 are changed, the test pattern print signal TPS is stored together with the printer driver 96. There is an advantage that the TPS can be upgraded at the same time. Therefore, it is possible to use a test pattern suitable for the paper feed amount actually used by the printer driver 96 for correcting the paper feed amount.

As shown in FIG. 12, this printer 20
In, it is possible to use a plurality of types of paper feed amount. Therefore, in this embodiment, the correction value δ is determined for each paper feed amount.

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]. Figure 1
3 (B) shows the 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 A-phase and B-phase signals are out of phase by 1/4 cycle, so one cycle (1
It is possible to command the position in units of 1/4 (440 dpi). Therefore, in the present embodiment, 1/4 of one cycle (1440 dpi) of the A-phase and B-phase signals of the encoder 46.
The distance corresponding to the cycle is used as the unit [pulse] of the correction value δ.

However, another value 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. Also,
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.

The black circles in FIG. 13A indicate four feed amounts F.
The correction value δ for (59 dots, 179 dots, 237 dots, 717 dots) is shown. These four feed amounts F are the feed amounts used in the four examples shown in FIGS. 11 (A) and 11 (B). However, since the correction value for the one-dot feed is almost zero, it is omitted in FIG.

As a method of determining the relationship between the plurality of feed amounts F and their correction values δ, the following various methods can be used.

Method 1: A test pattern is actually printed using a plurality of feed amounts, and the correction value δ for each feed amount is determined. Method 2: A test pattern is printed using a typical feed amount among a plurality of feed amounts to determine the correction value δ, and the correction values for other feed amounts are predicted based on this.

When the method 1 is adopted, for example, as shown in FIG.
The test pattern may be printed in each of the four types of modes shown in FIGS. 2A and 2B to determine the correction value δ (specifically, the patch number).

In method 2, there is a case where only one value is used as a typical 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 correction values for the other three feed amounts are predicted from this correction value. For predicting the correction value of the feed amount other than the typical feed amount, for example, a shape of a characteristic curve (prediction curve) such as a curve G1 shown in FIG. 13A or a straight line G2 passing through the origin is set in advance. This can be done by keeping Generally, a correction value for a feed amount other than the typical feed amount may be predicted according to a predetermined prediction curve. Here, the “prediction curve” has a broad meaning including a straight line.

The reason why it is preferable to use the maximum value of the feed amount used in the printer as the typical feed amount is that the larger the feed amount is, the larger the correction value is. When using two or more values as the typical feed amount, for example, the maximum value of the feed amount used in the printer,
Any other one feed amount is used.

In this way, if the test pattern is printed only for the typical feed amount to determine the correction value and the correction values for other feed amounts are predicted from the typical feed amount correction values, The number of test patterns is small, and the time required for correction can be shortened.

FIG. 14 is a table showing the 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. By doing so, it is possible to perform appropriate paper feed correction for each type of printing paper.

It is not necessary to actually measure the correction value δ for each printing sheet. For example, the correction value may be measured only for a predetermined one of the plurality of types of printing paper, and the correction values for the other printing papers may be predicted. Specifically, for example, the correction value δ can be 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 constant coefficient. In general, correction values for different types of printing papers have a substantially constant relationship, and there is little deviation from this, so such a prediction is possible. This way
By simply obtaining the correction value for one type of printing paper, it is possible to perform appropriate paper feed correction for other printing papers. Further, there is an advantage that the user of the printer 20 can reduce the trouble of printing the test pattern, and the complexity of the paper feed correction can be reduced.

FIG. 15 is a graph showing the relationship between the paper feed speed V and the correction value δ. As shown here, as the paper feed speed V increases, the correction value of the paper feed amount also tends to increase. Therefore, when the paper feed speed differs depending on the print mode, it is preferable to set the paper feed correction value δ according to the paper feed speed. Also in this case, it is possible to actually measure a correction value for one paper feed speed and predict a correction value for another paper feed speed.

The correction value δ shown in FIGS. 13 to 15 is
Non-volatile memory (EEPROM58) in the printer 20
Or the printer driver 96 (specifically, the computer 9
0 hard disk). At the time of actual printing, the 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.

FIG. 16 shows two transmission methods for the paper feed amount F and its correction value δ. In the first method shown in FIG. 16A, only the uncorrected regular feed amount F is transmitted from the printer driver 96 to the system controller 54. The paper feed control unit 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 control unit 54a of the system controller 54 uses the corrected feed amount F ′ as a command value for the sub-scanning drive circuit 62.
Supply to.

As described above, in the present embodiment, the test pattern is printed using the same interlace recording mode as that used for actual printing, and the paper feed is performed using the correction value δ determined according to the result. Since the amount is corrected, it is possible to perform high-quality printing with less paper feed error. Further, in particular, since the correction value is registered for each type of printing paper, it is possible to compensate for the difference in the paper feed amount depending on the printing paper used.

D. Structure of test pattern print signal: Fig. 1
7 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 configured 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.

In the right half of FIG. 17, 24 raster lines L1 to L24 are formed using such a dense nozzle row 36a.
Raster data R for forming one color patch with
The configuration of D1 is shown. According to the raster data RD1, dots of three colors of Y, M, and C are recorded on all the raster lines L1 to L24. Note that, in FIG. 18, for convenience of illustration, the Y, M, and C dot formation positions are illustrated as being displaced, but in reality, dots of each color are formed on the same pixel position.

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. When the paper feed error becomes positive, white stripes occur at the band boundary, and conversely, when the paper feed error becomes negative, black stripes occur at the band boundary. In other words, in the print signal of FIG. 17, the paper feed error is simulated by the difference in the paper feed amount of each patch.

FIG. 18 shows an example of a test pattern print signal for reproducing the patch of 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 indicating the dot formation state in each pixel is different from that in FIG. That is, the raster data is formed on the raster line L13 immediately below the band boundary so that dots of Y, M, and C inks are not formed. In other words,
In the print signal of FIG. 18, a paper feed error is simulated due to 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 lines is printed like the patch with patch number 1 shown in FIG. Therefore, if a paper feed error of one dot exists during actual printing, a clean patch without white lines is reproduced.

FIG. 19 is an explanatory diagram showing a configuration example of the test pattern print signal. The print signal for each patch includes the 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 above-described paper feed example 1 in FIG. 12 is used. 17 and 18
The print signal shown in (1) corresponds to the print signal in FIG.

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 shown in FIG. 17 which originally has no banding is used. Regarding the paper feed amount, the print signal for each patch is such that the value of the feed amount F4 at the fourth time is sequentially different by one dot.

The print signals shown in FIGS. 19A and 19B can print the three patches shown in FIG. However, as shown in FIG. 19A, when each patch is printed using the same paper feed amount and raster data simulating a sub-scan feed error, the unit of the correction value of the paper feed amount is raster. Limited to an integral multiple of the line pitch. On the other hand, as shown in FIG. 19B, when each patch is printed by using the same raster data and using the paper feed amount simulating the sub-scan feed error, as shown in FIG. The unit of the amount correction value can be set to a unit smaller than the raster line pitch.

E. Modifications: The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are also possible. is there.

E1. Modified Example 1 In the above embodiment, the color ink jet printer has been described, but the present invention can be applied to a monochrome printer and also to a printer other than the ink jet system. INDUSTRIAL APPLICABILITY The present invention is generally applicable to a printing apparatus that records an image on a print medium, and is also applicable to, for example, a facsimile apparatus or a copying machine.

E2. Modified Example 2 In the above embodiment, the case where the nozzle pitch k is 4 dots has been described. However, in the present invention, in general, when printing in the interlace recording mode is performed using a print head having a nozzle pitch k of 2 dots or more. Is applicable to. In general, pseudo band feed is 1
After performing (k-1) times of sub-scanning for dot feeding, {N ×
This is achieved by performing one sub-scan of k- (k-1)} dot feed. At this time, dot recording by main scanning is performed between each sub-scan feed. Also, "1 dot"
The unit means the dot pitch in the sub-scanning direction.

E3. Modification Example 3 In the above-described embodiment, as shown in FIG. 5, the case where the print head 36 having a two-row configuration of a black nozzle row and a color nozzle row is used has been described. It is also applicable to a print head in which all columns are at the same position in the sub-scanning direction and are sequentially arranged in the main scanning direction.

E4. Modification 4: In the above-described embodiment, the color patch is used as the test pattern, but any pattern other than the color patch can be used as the test pattern. However, the use of color patches has an advantage that banding due to a paper feed error can be easily detected.

Although the correction value is determined by one type of test pattern in the above embodiment, the correction value may be determined by using a plurality of types of test patterns. For example, a coarse correction value may be determined using the first test pattern for coarse adjustment, and a final fine correction value may be determined using the second test pattern for fine adjustment. For example, the coarse correction value can be set at 10-step intervals and the fine correction value can be set at 1-step intervals. In this way, by making adjustments in a plurality of stages, it is possible to efficiently determine fine correction values.

E5. Modification 5: In the above embodiment, the gray patch reproduced in composite black was used as the color patch of the test pattern, but it is also possible to use other color patches. For example, it is 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 a secondary color patch that is reproduced by using two of the three color inks of cyan, magenta, and yellow. As the ink used for reproducing the color patch, the ink of the color component whose image quality is desired to be improved by correcting the paper feed error is selected. That is, if a color patch is reproduced using ink of a color component whose image quality is desired to be improved by correcting the paper feed error, by correcting the paper feed error using the color patch, it is possible to obtain an image of an image in which the ink is often used. It is possible to improve the image quality.

E6. Modification 6: In the above-described embodiment, the correction value is determined by observing the test pattern by a human, but instead of this, an image quality measuring unit that mechanically measures the image quality of the test pattern is used to perform sub-scan feed. The influence of the error on the image quality may be measured, and the correction unit may correct the sub-scan feed according to the measurement result. By doing so, it is possible to appropriately correct the sub-scan feed error without requiring manual work.

E7. Modification 7: In the above embodiment, printing was performed in the interlaced recording mode, but the present invention is also applicable to printing in 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, main scanning line pitch).

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a printing system as an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a main configuration of a 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 a nozzle array on the lower surface of the print head.

FIG. 6 is a flowchart illustrating a procedure of paper feed correction before shipping the printer.

FIG. 7 is an explanatory diagram showing an example of a test pattern.

FIG. 8 is a flowchart showing a procedure of paper feed correction by a user.

FIG. 9 is an explanatory diagram showing an example of a user interface window W1 which allows a user to print a test pattern.

FIG. 10 is an explanatory diagram showing an example of a user interface window W2 that allows a user to set patch numbers.

FIG. 11 is an explanatory diagram showing an example of paper feeding used when printing a test pattern.

FIG. 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 for the 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 showing 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 ... driven roller 26 ... Platen 28 ... Carriage 30 ... Carriage motor 31 ... Paper feed motor 32 ... Tow belt 34 ... Guide rail 36 ... Print head 40 ... Gear train 42 ... Paper ejection roller 44 ... Giza Laura 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 scanning drive 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

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Claims (9)

[Claims] 1. A method 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, the method comprising: A step of actually measuring, for each printing apparatus, the effect of the sub-scan feed error on the image quality due to the manufacturing error of the paper feed roller for feeding the print medium in the sub-scan direction, and (b) when printing the image. In the step (a)
And a step of correcting the sub-scan feed amount based on the actual measurement result. 2. The correction method according to claim 1, wherein the print head has a nozzle pitch that is k times (k is an integer of 2 or more) a dot pitch in a sub-scanning direction substantially perpendicular to the main scanning direction. A correction method having a plurality of nozzles arranged in the scanning direction, wherein the printing of the image in the step (b) is performed according to an interlace recording mode. 3. The correction method according to claim 1, wherein in the step (a), a predetermined test pattern used for measuring the influence of the sub-scan feed error on image quality is printed. A correction method including a step, wherein the step of printing the test pattern can be executed according to a command from a user of the printing apparatus. 4. An apparatus for correcting a sub-scan feed amount of a print medium in a printing apparatus for performing printing by recording ink dots on the print medium while moving the print head in the main scanning direction, wherein: An image quality measurement unit that measures the effect on the image quality due to the sub-scan feed error due to the manufacturing error of the paper feed roller that feeds the print medium in the sub-scan direction, and when printing the image. And a correction unit that corrects the sub-scan feed amount based on the result of the actual measurement. 5. The apparatus according to claim 4, wherein the print head is sub-scanned at a nozzle pitch that is k times a dot pitch (k is an integer of 2 or more) in a sub-scanning direction substantially perpendicular to the main scanning direction. A sub-scan feed correction device having a plurality of nozzles arranged in a direction, and printing of the image is performed according to an interlace recording mode. 6. The apparatus according to claim 4 or 5, wherein the image quality measuring unit causes a predetermined test pattern used for measuring an influence of the sub-scan feed error on image quality to the printing apparatus. A sub-scan feed correction apparatus capable of being printed, and printing of the test pattern can be executed in response to a command from a user of the printing apparatus. 7. A computer including a printing device that prints 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 computer program, comprising: (a) a step of actually measuring, for each printing device, an 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. , (B) a step of correcting the sub-scan feed amount based on the actual measurement result of the step (a) when printing the image,
A computer program comprising a program for realizing the above-mentioned computer. 8. The computer program according to claim 7, wherein the print head has a nozzle pitch that is k times (k is an integer of 2 or more) a dot pitch in a sub-scanning direction substantially perpendicular to the main scanning direction. A computer program having a plurality of nozzles arranged in the scanning direction, wherein the printing of the image in the step (b) is executed according to an interlaced recording mode. 9. The computer program according to claim 7, wherein the step (a) prints a predetermined test pattern used to measure the influence of the sub-scan feed error on the image quality. A computer program including a step, wherein the step of printing the test pattern can be executed in response to an instruction from a user of the printing apparatus.