JPH11334055A - Bidirectional printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance print quality at the time of bidirectional printing by providing a main/subscan drive section for moving any one of a head or a print medium and adjusting the recording position in the main scanning direction with an adjusting value of one kind of dot selected from reciprocal positional shift adjusting values thereby relaxing the recording positional shift. SOLUTION: A printer 22 comprises a main scan driving section, i.e., a carriage motor 24 for reciprocating a carriage 31 in the axial direction of a platen 26, a subscan driving section, i.e., a paper feed motor 23, a head drive section, i.e., a control circuit 40, and a control section, i.e., the driving signal generating circuit 44 for the circuit 40, functioning as a recording position adjusting section for varying the ink ejecting position in the main scanning direction. Two kinds of dot (combined into three kinds of dot) are formed by regulating the driving wave at an ink ejecting section and adjusting values for reducing positional shift of recording are determined in the scanning direction for at least two kinds of going and returning strokes. Recording position in the main scanning direction is adjusted for going and returning strokes using an adjusting value for one kind of dot selected from these dots.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a technique for printing an image on a print medium while performing main scanning in both directions in a reciprocating manner. The present invention relates to a bidirectional printing technology that is capable of.

[0002]

2. Description of the Related Art In recent years, as an output device of a computer,
A color printer that discharges several colors of ink from a head is widely used. In recent years, as such a color printer, a multi-value printer capable of recording one pixel with a plurality of ink droplets has been proposed. In a multilevel printer, a relatively small amount of ink droplets form a relatively small dot in a one-pixel region, and a relatively large amount of ink droplets form a relatively large dot in a one-pixel region. Even with such a multi-value printer, so-called "bidirectional printing" can be performed to improve the printing speed, similarly to other conventional printers.

[0003]

In the bidirectional printing, due to the backlash of the driving mechanism in the main scanning direction and the warpage of the platen supporting the print medium below, the printing in the main scanning direction in the forward path and the return path is performed. The problem that the recording position is shifted easily occurs. As a technique for solving such a displacement, for example, Japanese Patent Application Laid-Open No. 5-696 disclosed by the present applicant is disclosed.
No. 25 is known. In this conventional technique, a positional deviation amount (print deviation) in the main scanning direction is used.
Are registered in advance, and the recording positions in the forward path and the backward path are corrected based on the positional deviation amount.

However, conventionally, little consideration has been given to the positional deviation between the forward path and the backward path when bidirectional printing is performed by a multi-value printer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and alleviates the deviation of the recording position in the main scanning direction between the forward pass and the return pass when performing bidirectional printing in a multi-value printer. The purpose is to improve the image quality.

[0006]

In order to solve at least a part of the above problems, the apparatus of the present invention performs printing in accordance with a print image signal while performing bidirectional main scanning in both directions. A bidirectional printing apparatus having a bidirectional printing function of printing an image on a medium, wherein a print head capable of recording a plurality of types of dots having different sizes in each pixel area on the print medium. A main scanning drive unit that performs bidirectional main scanning by moving at least one of the print medium and the print head, and a sub-scan that performs sub-scanning by moving at least one of the print medium and the print head A drive unit, a head drive unit that supplies a drive signal to the print head to perform printing on the print medium, and a control unit that controls the above units. Further, the control unit is configured to store, for at least two types of dots among the plurality of types of dots, an adjustment value for reducing a deviation of a recording position in a main scanning direction in a forward pass and a return pass, respectively, A recording position adjustment unit that adjusts a recording position in the main scanning direction in the forward path and the return path of the plurality of types of dots by using the adjustment value for one type of dot selected from two types of dots;
Is provided.

In this bidirectional printing apparatus, the print position in the main scanning direction in the forward path and the return path of a plurality of types of dots is adjusted using an adjustment value for one type of dot selected from at least two types of dots. Therefore, when performing bidirectional printing in the multi-value printer, it is possible to reduce the deviation of the recording position in the main scanning direction between the forward path and the backward path for one selected type of dot. Therefore, the image quality can be improved by selecting a dot in which the positional deviation is conspicuous as a target for adjusting the positional deviation.

In addition, the generation timing of the drive signal pulse is adjusted in at least one of the forward path and the backward path so as to reduce the deviation of the recording position of the selected one type of dot in the main scanning direction between the forward path and the backward path. You may do so. Specifically, for example, by delaying the drive signal in at least one of a forward path and a return path, it is possible to adjust the generation timing of the pulse of the drive signal. Alternatively, the generation timing of the pulses of the drive signal can be adjusted by changing the frequency of the drive signal in at least one of the forward path and the return path along the main scanning direction.

[0009] In this way, it is possible to reduce the positional deviation of the selected one type of dot.

[0010] Further, one type of dot is selected from the at least two types of dots in accordance with image type information indicating the type of image represented by the print image signal. The adjustment value may be used.

The type of dot in which the positional deviation is conspicuous may depend on the type of image. If a dot to be adjusted for positional deviation is selected in accordance with the type of image, the positional deviation of the dot can be reduced, so that image quality can be improved.

The image type information is information for at least distinguishing between a natural image main image mainly including a natural image in one page and a non-natural image main image mainly including an image other than the natural image in one page. The control unit, when recording the natural image main image, while adjusting the recording position of the plurality of types of dots in the main scanning direction so as to reduce the deviation of the recording position for relatively small dots, When recording the non-natural image-based image, the recording positions of the plurality of types of dots in the main scanning direction may be adjusted so as to reduce the deviation of the recording positions for relatively large dots.

A relatively large number of relatively small dots tend to be recorded when a natural image-based image is printed, while a relatively large number of relatively large dots are printed when a non-naturally-based image is printed. Therefore, the image quality can be improved by selecting the type of dot for which the positional deviation is to be adjusted according to the type of the image.

The image type information may be determined according to a statistical index value indicating the frequency of the plurality of types of dots recorded in one page.

This makes it possible to select the type of dot for which positional deviation is to be adjusted in accordance with the frequency of each dot used for recording an image. , The displacement can be reduced.

The method according to the present invention uses a print head capable of recording a plurality of types of dots having different sizes in each pixel area on a print medium while performing a main scan in both directions in a reciprocating manner. A bidirectional printing method of printing an image on the print medium in accordance with a print image signal, wherein at least two types of dots among the plurality of types of dots are recorded in a main scanning direction in a forward scan and a return scan. Adjustment values for reducing the deviation are set in advance, respectively, and the adjustment values for one type of dot selected from the at least two types of dots are used for the forward and backward passes of the plurality of types of dots. The recording position in the main scanning direction is adjusted.

Further, the recording medium according to the present invention can be used to reciprocate main scanning in a computer provided with a printing device capable of recording a plurality of types of dots having different sizes in each pixel area on the printing medium. A computer-readable recording medium recording a computer program for printing an image on the print medium in accordance with a print image signal while performing bidirectional printing, wherein at least two types of dots among the plurality of types of dots are provided. Regarding, among the adjustment values set in advance to reduce the deviation of the recording position in the main scanning direction between the forward pass and the return pass, the adjustment value for one type of dot selected from the at least two types of dots is set. The function of adjusting the recording position in the main scanning direction in the forward path and the backward path of the plurality of types of dots using the selected adjustment value. A computer-readable recording medium recording a computer program for implementing the computer.

With such a method and a recording medium, substantially the same effects as those of the above-described apparatus can be obtained.

[0019]

Other Embodiments of the Invention The present invention includes the following other embodiments. A first aspect is an aspect as a program supply device that supplies, via a communication path, a computer program that causes a computer to realize the functions of each step or each part of the above-described invention. In such an embodiment, the above-described method and apparatus can be realized by placing the program on a server or the like on a network, downloading the necessary program to a computer via a communication path, and executing the program.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Configuration of Apparatus Hereinafter, embodiments of the present invention will be described based on examples. FIG. 1 is a block diagram showing a configuration of a bidirectional printing apparatus as one embodiment of the present invention. As shown in the figure, the scanner 12 and the color printer 22 are connected to a computer 90, and a predetermined program is loaded and executed on the computer 90, so that the computer 90 functions as a bidirectional printing apparatus as a whole. This computer 90
Is centered on a CPU 81 that executes various arithmetic processes for controlling operations related to image processing according to a program,
The following components are connected to each other by a bus 80. R
The OM 82 previously stores programs and data necessary for the CPU 81 to execute various types of arithmetic processing.
Reference numeral 83 denotes a memory for temporarily reading and writing various programs and data necessary for the CPU 81 to execute various arithmetic processes. The input interface 84 controls input of signals from the scanner 12 and the keyboard 14, and the output interface 85 controls output of data to the printer 22. The CRTC 86 is a CRT2 capable of color display.
1 to the disk controller (DD).
C) 87 controls the exchange of data with the hard disk 16, the flexible drive 15, or a CD-ROM drive (not shown). On the hard disk 16,
The RAM 83 stores various programs loaded and executed, various programs provided in the form of device drivers, and the like.

In addition, a serial input / output interface (SIO) 88 is connected to the bus 80. This SIO 88 is connected to the modem 18 and the modem 1
8 is connected to a public telephone line PNT. The computer 90 is connected to an external network via the SIO 88 and the modem 18, and by connecting to a specific server SV, it is also possible to download a program required for image processing to the hard disk 16. In addition, it is also possible to load a necessary program from a flexible disk FD or a CD-ROM, and cause the computer 90 to execute the program.

FIG. 2 is a block diagram showing the software configuration of the bidirectional printing apparatus. In the computer 90,
An application program 95 operates under a predetermined operating system. The operating system incorporates a video driver 91 and a printer driver 96, and the application program 95 outputs intermediate image data MID to be transferred to the printer 22 via these drivers. An application program 95 for retouching an image reads an image from the scanner 12 and displays the image on the CRT display 21 via the video driver 91 while performing predetermined processing on the image.
Data ORG supplied from the scanner 12 is original color image data ORG read from a color original and composed of three color components of red (R), green (G), and blue (B).

When the application program 95 issues a print command, the printer driver 96 of the computer 90 receives the image information from the application program 95, and receives the image information from the application program 95 in a signal that can be processed by the printer 22 (here, cyan, magenta, yellow, and black). (A multilevel signal for each color). In the example shown in FIG. 2, inside the printer driver 96, a resolution conversion module 97, a color correction module 98, a color correction table LUT, a halftone module 99,
A rasterizer 100 is provided.

The resolution conversion module 97 serves to convert the resolution of the color image data handled by the application program 95, that is, the number of pixels per unit length into a resolution that can be handled by the printer driver 96. The image data whose resolution has been converted in this way is still RGB.
The color correction module 98 refers to the color correction table LUT and uses the printer 22 for each pixel, cyan (C), magenta (M), yellow (Y), and black, with reference to the color correction table LUT. (K) is converted into data of each color. The data thus color-corrected is, for example, 2
It has a gradation value with a width such as 56 gradations. The halftone module executes halftone processing for expressing such gradation values in the printer 22 by forming dots in a dispersed manner. The image data processed in this way is rearranged by the rasterizer 100 in the order of data to be transferred to the printer 22, and the final print image data FNL
Is output as In the present embodiment, the printer 22 only plays a role of forming dots in accordance with the print image data FNL, and does not perform image processing.

Next, a schematic configuration of the printer 22 will be described with reference to FIG. As shown in the figure, the printer 22 includes a mechanism for transporting a sheet P by a paper feed motor 23 and a carriage 31 by a carriage motor 24 for moving the platen 2.
6, a mechanism for reciprocating in the axial direction, a mechanism for driving the print head 28 mounted on the carriage 31 to eject ink and form dots, and a mechanism for driving these paper feed motors 23,
The control circuit 40 controls the exchange of signals with the carriage motor 24, the print head 28, and the operation panel 32.

The carriage motor 24 functions as a main scanning drive unit, and the paper feed motor 23 functions as a sub scanning drive unit. Further, the control circuit 40 functions as a head driving unit that drives the print head 28, and also functions as a control unit that controls the main scanning driving unit, the sub-scanning driving unit, and the head driving unit.

A mechanism for reciprocating the carriage 31 in the axial direction of the platen 26 includes a sliding shaft 34 erected in parallel with the axis of the platen 26 and slidably holding the carriage 31.
A pulley 38 for extending an endless drive belt 36 between the carriage motor 24 and a position detection sensor 39 for detecting the origin position of the carriage 31 are provided.

The carriage 31 has a cartridge 71 for black ink (Bk) and five colors of cyan (C1), light cyan (C2), magenta (M1), light magenta (M2), and yellow (Y). A color ink cartridge 72 containing ink can be mounted. For two colors, cyan and magenta, two types of inks are provided. A total of six ink discharge heads 61 to 66 are formed on the print head 28 below the carriage 31, and at the bottom of the carriage 31, an introduction pipe 67 (for introducing ink from the ink tank to each color head). (See FIG. 4). Carriage 31
When the cartridge 71 for black (Bk) ink and the cartridge 72 for color ink are mounted from above, the introduction pipe 67 is inserted into the connection hole provided in each cartridge, and each ink cartridge is connected to the ejection heads 61 to 66. Supply of ink becomes possible.

The control circuit 40 includes a drive signal generation circuit 4 for generating a drive signal DRV for driving the print head 28.
4 is provided. The drive signal generation circuit 44 outputs the drive signal D
By adjusting the RV, it has a function as a recording position adjustment unit that changes the ink ejection position (that is, the dot recording position) in the main scanning direction. Drive signal generation circuit 4
4 will be described later.

FIG. 4 is an explanatory diagram showing a schematic configuration inside the print head 28. As shown in FIG. When the ink cartridges 71 and 72 are mounted on the carriage 31, the ink in the ink cartridge is sucked out through the introduction pipe 67 by utilizing the capillary phenomenon as shown in FIG. The print head 28 is guided to each color head 61 to 66 of the print head 28. When the ink cartridge is first installed, the operation of sucking ink into the heads 61 to 66 of the respective colors is performed by a dedicated pump. In this embodiment, a pump for suction and a cap for covering the print head 28 at the time of suction are provided. The illustration and description of such a configuration are omitted.

As will be described later, the heads 61 to 66 of each color are provided with 48 nozzles Nz for each color (see FIG. 6), and each nozzle is one of the electrostrictive elements. A piezo element PE having excellent responsiveness is arranged.
FIG. 5 shows the structure of the piezo element PE and the nozzle Nz in detail. As shown in the upper part of FIG. 5, the piezo element PE has an ink passage 68 for guiding ink to the nozzle Nz.
It is installed in a position in contact with. As is well known, the piezo element PE is an element that distorts the crystal structure due to the application of a voltage and converts electro-mechanical energy very quickly. In this embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, the piezo element PE expands by the voltage application time as shown in the lower part of FIG. One side wall 68 is deformed. As a result,
The volume of the ink passage 68 contracts in accordance with the expansion of the piezo element PE, and the ink corresponding to the contraction is discharged as particles Ip at a high speed from the tip of the nozzle Nz. Printing is performed by the ink particles Ip penetrating into the paper P mounted on the platen 26.

FIG. 6 is an explanatory diagram showing the arrangement of the ink jet nozzles Nz in the ink discharge heads 61 to 66. The arrangement of these nozzles is composed of six sets of nozzle arrays that eject ink for each color, and 48 nozzles Nz are arranged in a staggered manner at a constant nozzle pitch k. The positions of the nozzle arrays in the sub-scanning direction coincide with each other. The 48 nozzles Nz included in each nozzle array need not be arranged in a staggered manner, but may be arranged on a straight line. However, the arrangement in a staggered pattern as shown in FIG. 6 has an advantage that the nozzle pitch k can be easily set small in manufacturing.

The printer 22 is provided with a nozzle Nz having a constant diameter as shown in FIG.
Three types of dots having different diameters can be formed using z. This principle will be described. FIG. 7 is an explanatory diagram showing the relationship between the driving waveform of the nozzle Nz when ink is ejected and the ink Ip ejected. The drive waveform indicated by a broken line in FIG. 7 is a waveform when a normal dot is ejected. In the section d2, once a negative voltage is applied to the piezo element PE, the piezo element PE is deformed in a direction in which the cross-sectional area of the ink passage 68 is increased, contrary to the case described above with reference to FIG. As shown in the state A of FIG. 7, the ink interface Me called the meniscus is
The state is dented inside z. On the other hand, when a negative voltage is suddenly applied as shown in the section d1 using the drive waveform shown by the solid line in FIG. 7, the meniscus is greatly depressed inward compared to the state A as shown in the state a. next,
When the voltage applied to the piezo element PE is made positive (section d)
3) Ink is ejected based on the principle described above with reference to FIG. At this time, the state B and the state C are changed from the state in which the meniscus is not much depressed inward (state A).
Large ink droplets are ejected as shown in (a), and small ink droplets are ejected as shown in the state (b) and the state (c) from the state where the meniscus is largely dented inward (state a).

As described above, the dot diameter can be changed according to the change rate when the drive voltage is made negative (section d1, d2). It is easy to imagine that the dot diameter can be changed according to the magnitude of the peak voltage of the driving waveform. In the present embodiment, two types of driving waveforms, one for forming small dots and the other for forming medium dots, are prepared based on such a relationship between the driving waveform and the dot diameter. . FIG. 8 shows a driving waveform used in this embodiment. The drive waveform W1 is a waveform (small dot pulse) for forming a small dot, and the drive waveform W2 is a waveform (medium dot pulse) for forming a medium dot. When the small dot pulse W1 and the medium dot pulse W2 are generated continuously as shown in FIG. 8 within the main scanning period for one pixel, the small dot ink droplet and the medium dot ink droplet Landed in the area, large dots can be formed.

In the printer 22 having the hardware configuration described above, the carriage 31 is reciprocated by the carriage motor 24 (hereinafter, referred to as main scanning) while the paper P is transported by the paper feed motor 23 (hereinafter, referred to as sub-scanning). ), And at the same time, the respective color heads 61 to 6 of the print head 28.
By driving the piezo elements PE of No. 6, each color ink is ejected, dots are formed, and a multicolor image is formed on the paper P.

In the present embodiment, as described above, the printer 22 having the head for discharging ink using the piezo element PE is used. However, as the discharge drive element, various devices other than the piezo element are used. It is possible to use. For example, the present invention can be applied to a printer having an ejection drive element of a type in which a heater arranged in an ink passage is energized and ink is ejected by bubbles generated in the ink passage.

B. Adjustment of Recording Position in Embodiment: FIG. 9
FIG. 5 is an explanatory diagram showing a deviation of an ink droplet landing position in the main scanning direction which occurs during bidirectional printing when the recording position of the dot in the main scanning direction is not adjusted. The grid in FIG. 9 shows the boundaries of the pixel areas, and one rectangular area divided by the grid corresponds to an area for one pixel. The dots in each pixel area are recorded by ink droplets ejected by the print head 28 when the print head 28 (not shown) moves along the main scanning direction. In the example of FIG. 9, the odd-numbered raster lines L1, L3, and L5 are recorded on the outward path, and the even-numbered raster lines L2 and L4 are recorded on the backward path.
At this time, by adjusting the amount of ink to be ejected for each pixel, one of three types of dots having different sizes can be formed in the area of one pixel. That is, small dots can be formed by ejecting a relatively small amount of ink droplets into the area of one pixel, and medium dots can be formed by ejecting a relatively large amount of ink drops into the area of one pixel. be able to. In addition, a large dot can be formed by ejecting both an ink droplet for forming a small dot and an ink droplet for forming a medium dot into the area of one pixel. As a result, each pixel can be reproduced with four gradations (no dot, small dot, medium dot, large dot).

As can be seen from FIG. 9, in the bidirectional printing, the landing positions of the ink droplets in the main scanning direction are different between the forward path and the backward path. That is, a relatively small amount of ink droplet for recording a small dot lands on the left half of the pixel area on the outward path, and lands on the right half of the pixel area on the return path. Conversely, a relatively large amount of ink droplets for recording medium dots land on the right half of the pixel area on the outward path, and land on the left half of the pixel area on the return path.

FIG. 10 is an explanatory diagram showing the distribution of the deviation between the recording positions of the forward pass and the return pass for small dots and medium dots, respectively. FIG. 10 (a-1) shows the distribution in the main scanning direction of the deviation amount Δx of the small dot recording position. FIG.
0 (a-2) indicates the corresponding recording position of the forward path and the return path. FIG. 10B-1 shows the distribution in the main scanning direction of the shift amount Δx of the recording position of the medium dot.
(B-2) shows the recording positions of the forward path and the return path corresponding to this. In FIGS. 10 (a-2) and 10 (b-2), the vertical lines drawn by solid lines are ruled lines in the vertical direction (sub-scanning direction) recorded on the outward path and the return path. Note that the direction of the horizontal axis x is the direction of the outward path, which also corresponds to the digit direction of the printing paper. Hereinafter, the width of the printing paper along the main scanning direction is referred to as “main scanning width” or “main scanning range”.

As shown by the solid line in FIG. 10 (a-1), the deviation amount Δx between the forward and backward recording positions varies along the main scanning direction. This is shown in FIG.
The same is true for The reason why the shift amount Δx of the recording position changes along the main scanning direction is that the shift amount Δx also changes due to the warpage of the platen or the like. Note that the deviation amount Δx is defined as a value obtained by subtracting the recording position on the return path from the recording position on the outward path. In this example, the distribution of the deviation amount Δx in the main scanning direction for the small dots has a negative value, while the distribution of the deviation amount Δx for the medium dots in the main scanning direction has a positive value. Depending on the model of the bidirectional printing apparatus, the amount of deviation of small dots may be positive and the amount of deviation of medium dots may be negative, contrary to FIGS. 4 (a-1) and (b-1).

Since the distribution of the deviation amount Δx differs depending on the type of printing apparatus, the deviation amount Δx on the actual printed material differs depending on the type of printing apparatus.
Is measured. The distribution of the deviation amount Δx can be measured by various methods. For example, at the time of assembling the printer 22, the same pattern (for example, a black and white stripe pattern) is printed on each of the outward path and the return path, and the deviation amount Δx can be manually measured from the print result. Alternatively, the printer 22
Provided with an optical reading device such as a CCD camera
The deviation amount Δx may be automatically measured while printing the same pattern on the outward path and the return path. From the distribution of the deviation amount Δx thus obtained, the average value Δ of the deviation amount of the small dots is obtained.
xave.s and the average value Δxave.l of the shift amounts of the medium dots are calculated.

FIG. 11 is a block diagram showing the internal configuration of the drive signal generation circuit 44 in the embodiment. The drive signal generation circuit 44 includes an original drive signal generation circuit 102, a variable delay circuit 104, a delay amount setting circuit 106, and a programmable ROM (PROM) 108. The original drive signal generation circuit 102 generates an original drive signal ODRV having a waveform as shown in FIG. This original drive signal O
The DRV is delayed by the variable delay circuit 104 to become a drive signal DRV, and the drive signal DRV is supplied to the print head 28. The delay amount setting circuit 106 includes the variable delay circuit 1
04 has a function of setting the delay amount.

The variable delay circuit 104 and the delay amount setting circuit 106 function as a narrowly-defined recording position adjustment unit that changes the dot recording position by adjusting the original drive signal ODRV. Further, the PROM 108 functions as a memory for storing an adjustment amount for adjusting the recording position.

In the PROM 108, there are provided delay amount setting values ΔTS, ΔT for correcting the positional deviation between the small dot and the medium dot.
L is registered respectively. These delay amount setting values Δ
TS and ΔTL are, for example, as shown in FIGS.
These are set values for setting the delay amounts corresponding to the average shift amounts Δxave.s and Δxave.l shown in 1) in the variable delay circuit 104. That is, the delay amount setting values ΔTS, ΔTL
Is a delay amount Δxave.s / which is obtained by dividing the average deviation amounts Δxave.s and Δxave.l by the driving speed v of the print head in the main scanning direction.
v, Δxave.l / v are set values for setting in the variable delay circuit 104.

The adjustment of the delay amount of the original drive signal ODRV is performed on at least one of the forward path and the return path. For example, FIG.
When correcting the positional deviation of the small dots as shown in FIGS. 0 (a-1) and (a-2), the print head 2 is shifted by -Δxave.s / v later than the unadjusted state on the return path.
8 so that the original drive signal ODRV
Adjust the amount of delay. 10 (b-1), (b-
When correcting the misalignment of the medium dot as shown in 2), the original drive signal DRV is set so that the ink is ejected from the print head 28 at a timing earlier by Δxave.l / v than in the unadjusted state on the return path. Adjust the amount of delay. Since the timing of ink ejection in the forward path and the return path may be relatively adjusted, the delay amount is adjusted in both the forward path and the return path, and the difference between the printing positions due to the difference in the delay amounts is the position deviation. You may make it correspond to an appropriate correction amount.

As a correction amount of the positional deviation, a value other than the average value of the positional deviation amounts in the main scanning range can be used. For example, the average value of the maximum value and the minimum value of the position shift amount can be used as the position shift correction amount.

The delay amount setting circuit 106 reads the delay amount setting value ΔT (ΔTS or ΔTL) from the PROM 108 in response to the image type signal ITS indicating the type of image, and sets the delay amount in the variable delay circuit 104 accordingly. Set. Here, the image type refers to an image mainly composed of a natural image in which an image for one page recorded on printing paper includes a relatively large amount of “natural image”, or an image of a type other than the natural image (for example, a character or a graph) Is a non-natural image-based image containing a relatively large number of characters. Here, “natural image” means a photographic image. Since a small dot is often used in a natural image-based image, it is preferable to correct the reciprocal positional deviation of the small dot. On the other hand, for non-natural image-based images such as characters and graphs,
Since medium dots are often used, it is preferable to correct the reciprocal positional deviation of the medium dots. Note that FIG.
In the case of using three types of dots as described above, by correcting the reciprocal positional deviation for the medium dot, the reciprocal positional deviation for the large dot can be corrected at the same time.

The image type signal ITS can be generated in various modes. For example, the operator specifies a natural image-based image or a non-natural image-based image on the print condition setting screen displayed on the computer 90, and supplies the image type signal ITS from the computer 90 to the printer 22 in response to the specification. May be performed.

Alternatively, the printer driver 96 may automatically determine the type of the image according to the print image data FNL (FIG. 2), generate an image type signal ITS, and supply this to the printer 22. Good. In a multi-value printer, print image data FNL for one color per pixel (hereinafter, referred to as “pixel value”) is composed of a plurality of bits. For example, when three types of dots can be printed as shown in FIG. 9, the pixel value is composed of 2 bits and can represent a value of 0 to 3. For example, a pixel value “0” indicates no dot, and “1”, “2”, and “3” indicate a small dot, a medium dot, and a large dot, respectively. The frequency of recording three types of dots in an image for one page is
Pixel values representing three types of dots (that is, 1 to 3) are 1
It can be easily determined by examining how many are included in the image of the page. When creating the print image data FNL, the printer driver 96 obtains the frequency of each pixel value in the image of one page. When the frequency of the pixel value corresponding to the small dot is the highest, the image type signal ITS is set to a level indicating that the image is a natural image main image. On the other hand, when the frequency of the pixel value corresponding to the medium dot or the large dot is the highest, the image type signal ITS is set to a level indicating that the image is a non-natural image main image. When the frequency of the pixel value corresponding to the large dot is the highest, the image type signal ITS is set to a level indicating that an intermediate delay amount between the small dot and the medium dot (that is, an intermediate positional shift correction amount) is used. May be set. In this case, PROM1
08, a delay amount setting value indicating the intermediate delay amount is registered in advance.

The ink for which the frequency of the pixel value is obtained may be limited to ink having a relatively high density. For example, if the printing device is dark cyan (DC), light cyan (L
C), dark cyan (DC), dark magenta (DM), light magenta (LM), yellow (Y), and black (K) if available.
, And black (K), only three color inks having relatively high densities can be selected as targets for the process of calculating the frequency of pixel values. Then, the sum of the frequencies of the pixel values for these three color inks is calculated, and the image type signal ITS can be generated according to the sum of the frequencies. in this way,
If the frequency of the pixel value is obtained only for the ink having a relatively high density, and the image type signal ITS is generated from the sum of these frequencies, it is possible to mainly eliminate the positional deviation of the dot that is conspicuous.

When determining the image type signal ITS based on the frequency of the pixel value, it is possible to use not only the frequency itself but also another statistical index value indicating the frequency.

As described above, in the above-described embodiment, an appropriate amount of positional deviation correction for small dots and medium dots is obtained, and one of them is selected to correct the recording positions of the forward and backward dots. Accordingly, it is possible to reduce the deviation of the recording position between the forward path and the backward path for the selected dot. That is, when many small dots are used, the recording position is corrected so as to reduce the positional deviation of the small dots, so that the image quality of an image having a relatively large number of small dots can be improved. Further, when medium dots are frequently used, the recording position is corrected so as to reduce the positional deviation of the medium dots, so that the image quality of an image having a relatively large number of medium dots can be improved.

In the above embodiment, the deviation of the dot recording position was corrected by adjusting the delay amount of the drive signal DRV. Instead, the original drive signal generation circuit 102
May be delayed in generating the original drive signal ODRV. Generally, the drive signal D is provided on at least one of the forward path and the return path so as to reduce the deviation of the recording position with respect to the selected one type of dot.
What is necessary is just to adjust the generation timing of the RV pulse.

C. Other Embodiment: Instead of delaying the drive signal DRV as in the above embodiment, adjusting the frequency of the drive signal DRV to adjust the generation timing of the pulse of the drive signal DRV to reduce the positional deviation of the dots. Is also possible. FIG. 12 is an explanatory diagram showing a method of reducing the dot displacement by adjusting the frequency of the drive signal DRV. FIG. 12A shows the distribution in the main scanning direction of the deviation amount Δx of the recording position when no correction is performed. FIG. 12B shows a corresponding shift in the recording position (pixel position) of the forward path and the return path.
In FIG. 12A, the distribution of the deviation amount Δx along the main scanning direction is upwardly convex, and has a positive value substantially at the center of the main scanning width Lmax and a negative value at both ends. Extreme cases are assumed.

FIG. 12C shows an ideal distribution of the correction amount δ for correcting the shift amount shown in FIG.
FIG. 12D shows the recording positions of the forward path and the backward path when the deviation amount Δx is corrected to be substantially zero. The ideal correction amount δ is obtained by inverting the positive and negative signs of the distribution of the deviation amount Δx shown in FIG.

FIG. 12E shows a change in the frequency fDRV of the drive signal DRV used for correcting the deviation of the recording position in the present embodiment. The main scanning width Lmax is
It is divided into five regions R1 to R5 at substantially equal intervals,
The value of the frequency fDRV of the drive signal DRV is individually set for each region. Note that L1 to L4 indicate the positions of the boundaries of the areas. In the regions R2 and R4 where the correction amount δ is close to zero in FIG. 12C, the frequency fDRV is set to the standard value f2. In the region R3 where the correction amount δ is negative, the frequency fDRV becomes a value f3 larger than the standard value f2. In the regions R1 and R5 where the correction amount δ is positive, the frequency fDRV is set to a value f1 smaller than the standard value f2. The ejection timing of the ink in the print head 28 depends on the frequency of the drive signal DRV. Therefore, the higher the frequency fDRV is, the shorter the period of ink ejection becomes, and the shorter the distance between dots in the main scanning direction becomes. The relationship between the change in the dot recording position due to the change in the frequency fDRV and the correction of the positional deviation will be described later.

As shown in FIG. 12E, if the frequency fDRV of the drive signal DRV is individually set for each of a plurality of areas which divide the main scanning range, the ideal correction amount δ is approximately realized. can do. The drive signal generation circuit 44
If the capability of FIG. 3 permits, the frequency of the drive signal DRV may be changed almost continuously. However, FIG.
As shown in (e), changing the frequency fDRV stepwise has the advantage that the circuit configuration becomes simpler.

The change in frequency Δx shown in FIG. 12 (e) is applied to the return path, and the frequency fDRV is kept at a constant value (for example, the standard value f2) on the outward path.
Can be corrected so that is substantially zero. Alternatively, the frequency fDRV may be adjusted on the outward path, and the frequency fDRV may be kept constant on the return path. Further, the frequency may be adjusted in both the forward path and the return path. That is, in general, the frequency fDRV of the drive signal DRV may be adjusted in at least one of the forward path and the return path.

The frequency of the main scanning drive signal for driving the carriage motor 24 is maintained at the same constant value in the forward path and the return path. Therefore, if the frequency fDRV of the drive signal DRV of the print head 28 is changed as shown in FIG. 12E, the recording position (ink ejection position) in the main scanning direction is correspondingly changed.
Changes. However, it is also possible to correct the deviation of the recording position in bidirectional printing by changing the frequency of the main scanning drive signal.

The relationship between the change in the dot recording position due to the change in the frequency fDRV and the correction of the positional deviation is as follows. As described above, the higher the frequency fDRV, the smaller the distance between dots. Since the frequency fDRV is relatively low in the first and fifth regions R1 and R5 in FIG. 12E, the distance between dots is relatively large, and the recording position on the return path is minus x compared to FIG. Direction. On the other hand, in the third region R3, the frequency fDRV
Is relatively high, the distance between the dots is relatively small, and the recording position on the return path is shifted in the plus x direction as compared with FIG. 12B. As a result, as shown in FIG. 12D, the recording position on the return path is corrected so that the recording positions on the outward path and the return path substantially match. In the case where the frequency fDRV is adjusted on the outward path, the frequency fDRV may be changed in the same distribution as in FIG.

FIG. 13 is a block diagram showing a configuration of a circuit for generating a clock signal used when generating original drive signal ODRV. This clock signal generation circuit 46
A reference clock generation circuit 112, a frequency divider 114, a parameter setting circuit 118, and a PROM 120 are provided. The reference clock signal RCLK generated by the reference clock generation circuit 112 is frequency-divided by the frequency divider 114 into 1 / n to become a clock signal CLK. Original drive signal generation circuit 10
2 generates an original drive signal ODRV having a waveform as shown in FIG. 8 in synchronization with the clock signal CLK.
Therefore, by adjusting the frequency of the clock signal CLK, the frequencies of the original drive signal ODRV and the drive signal DRV can be adjusted.

The PROM 120 stores the value of the frequency division ratio n in each of the regions R1 to R5 and the positions L1 to Lmax of the boundaries between the regions.
(Or the width of each area). The parameter setting circuit 118 implements the frequency change shown in FIG. 12E by changing the setting of the frequency division ratio n in the frequency divider 114. The parameter setting circuit 118 controls the frequency divider 1
And a counter (not shown) for counting the number of pulses of the clock signal CLK output from the counter 14. The count value of this counter is compared with the positions L1 to Lmax of boundaries between regions (or the count value and the width of each region). ), It is determined which of the five regions R1 to R5 the current main scanning position of the carriage 31 is. Note that the origin position of the carriage 31 is determined in advance by a signal supplied from the position detection sensor 39 (FIG. 3) to the control circuit 40. Parameter setting circuit 118
Reads the frequency division ratio n corresponding to the area including the main scanning position of the carriage 31 from the PROM 120, and
Set to.

The parameters n and L1 to Lmax are predetermined for small dots and medium dots, respectively.
It is stored in the ROM 120. The parameter setting circuit 118 reads one of the parameters of the small dot and the medium dot in accordance with the image type signal ITS, and sets the frequency dividing ratio n in the frequency divider 114 in accordance with the parameter.

As described above, in the clock generation circuit 46, only by changing the frequency division ratio n for dividing the reference clock signal RCLK for each region, the clock signal CLK having a frequency suitable for each region is generated. Can be easily obtained,
A drive signal DRV having the same frequency as the clock signal CLK can be generated.

It should be noted that the present invention is not limited to the above examples and embodiments, but can be implemented in various modes without departing from the gist thereof.
For example, the following modifications are possible.

(1) In the example of FIG. 8, the waveforms of the drive signals for recording the small dot and the medium dot are different. For example, by generating the waveform of the small dot twice consecutively, May be recorded.

(2) In the above embodiment, the adjustment amount for correcting the positional deviation is determined for each of the two types of dots, the small dot and the medium dot, and one of them is used for the forward and backward dots. Has been corrected, the position deviation may be corrected for three or more types of dots. For example, as shown in FIG. 9, when three types of dots having different sizes can be printed, the adjustment amounts for correcting the positional deviation are determined for each of these three types of dots, and one of them is determined. One of them may be selected and used. In general, when one of a plurality of types of dots having different sizes can be recorded in one pixel area, an adjustment amount for correcting a positional deviation should be set for at least two types of dots.

(3) The present invention is not limited to the method and apparatus for ejecting ink droplets, but is also applicable to the method and apparatus for recording dots by other means. That is, the present invention provides a method and apparatus in which each nozzle can selectively print any one of a plurality of types of dots having different sizes in each pixel area on a main scanning line during one main scan. Applicable to Here, each of the forward main scan and the return main scan is defined as one main scan.

(4) In the above embodiment, part of the configuration realized by hardware may be replaced by software, and conversely, part of the configuration realized by software may be replaced by hardware. You may do so. For example, a part of the function of the drive signal generation circuit 44 shown in FIG. 11 can be realized by software.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a bidirectional printing apparatus according to an embodiment.

FIG. 2 is an explanatory diagram showing a configuration of software.

FIG. 3 is a schematic configuration diagram of a printer according to the embodiment.

FIG. 4 is an explanatory diagram illustrating a schematic configuration of a dot recording head of the printer according to the embodiment.

FIG. 5 is an explanatory diagram showing a dot formation principle in the printer of the embodiment.

FIG. 6 is an explanatory diagram showing an example of nozzle arrangement in the printer of the embodiment.

FIG. 7 is an enlarged view of a nozzle arrangement in the printer of the embodiment and an explanatory diagram showing a relationship with a formed dot.

FIG. 8 is an explanatory diagram for explaining the principle of forming dots having different diameters.

FIG. 9 is an explanatory diagram showing a displacement of an impact position of an ink droplet which occurs during bidirectional printing when the position adjustment is not performed.

FIG. 10 is an explanatory diagram showing a distribution of deviations of recording positions of a forward pass and a return pass for small dots and medium dots.

FIG. 11 is a block diagram showing an internal configuration of a drive signal generation circuit 44.

FIG. 12 is an explanatory diagram showing a method of adjusting the dot recording position in the main scanning direction by adjusting the frequency of a drive signal DRV.

FIG. 13 is a block diagram showing a configuration of a clock signal generation circuit used in the original drive signal generation circuit 102.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 ... Scanner 14 ... Keyboard 15 ... Flexible drive 16 ... Hard disk 18 ... Modem 21 ... CRT display 22 ... Color printer 23 ... Paper feed motor 24 ... Carriage motor 26 ... Platen 28 ... Print head 31 ... Carriage 32 ... Operation panel 34 ... Slider Driving shaft 36 Drive belt 38 Pulley 39 Position detection sensor 40 Control circuit 44 Drive signal generation circuit 46 Clock signal generation circuit 61-66 Ink ejection head 67 Introduction pipe 68 Ink passage 71, 72 Ink cartridge 80 Bus 81 CPU 82 ROM 83 RAM 84 Input interface 85 Output interface 86 CRTC 88 SIO 90 Computer 91 Video driver 95 Application program 96 Printer driver 97 Resolution conversion module 98 Color correction module 99 Halftone module 100 Rasterizer 102 Original drive signal generation circuit 104 Variable delay circuit 106 Delay setting circuit 108 PROM 112 Reference clock generation circuit 114 Minute Circuit 118: Parameter setting circuit 120: PROM

Claims (15)

[Claims] 1. A bidirectional printing apparatus having a bidirectional printing function of printing an image on a print medium in accordance with a print image signal while performing bidirectional main scanning in a reciprocating manner. A print head capable of recording a plurality of types of dots having different sizes in a pixel area; and a main scanning drive unit performing bidirectional main scanning by moving at least one of the print medium and the print head. A sub-scanning drive unit that performs sub-scanning by moving at least one of the print medium and the print head; a head drive unit that supplies a drive signal to the print head to perform printing on the print medium; A control unit that controls each of the units, wherein the control unit determines a recording position in at least two types of dots among the plurality of types of dots in a main scanning direction in a forward scan and a return scan. And a memory for storing adjustment values for reducing the deviation of the plurality of dots in forward and backward passes of the plurality of types of dots by using the adjustment values for one type of dot selected from the at least two types of dots. A bidirectional printing apparatus comprising: a recording position adjustment unit that adjusts a recording position in the main scanning direction. 2. The bidirectional printing apparatus according to claim 1, wherein the recording position adjustment unit is configured to reduce a deviation of a recording position of the selected one type of dot in a main scanning direction on a forward path and a return path. A bidirectional printing apparatus that adjusts a timing of generating the pulse of the drive signal in at least one of a forward path and a return path. 3. The bidirectional printing apparatus according to claim 2, wherein the recording position adjustment section delays the drive signal in at least one of a forward pass and a return pass to adjust a timing of generating a pulse of the drive signal. Coordinate, bidirectional printing device. 4. The bidirectional printing apparatus according to claim 2, wherein the recording position adjustment unit changes the frequency of the drive signal in at least one of a forward path and a backward path along a main scanning direction, thereby changing the frequency of the driving signal. A bidirectional printing apparatus that adjusts the timing of generating drive signal pulses. 5. The bidirectional printing apparatus according to claim 1, wherein the recording position adjustment unit is configured to perform the recording position adjustment in accordance with image type information indicating a type of an image represented by the print image signal. A bidirectional printing apparatus that selects one type of dot from the at least two types of dots and uses the adjustment value for the selected one type of dot. 6. The bidirectional printing apparatus according to claim 5, wherein the image type information includes a natural image main image mainly including a natural image in one page and an image other than the natural image in one page. The control unit includes at least information for discriminating between a non-natural image main image included as a main image and a non-natural image main image, wherein the control unit is configured to reduce a deviation of a recording position of a relatively small dot when recording the natural image main image. In addition to adjusting the recording positions of the various types of dots in the main scanning direction, the main scanning direction of the plurality of types of dots is adjusted so as to reduce the deviation of the recording position for relatively large dots when recording the non-natural image main image. Bi-directional printing device that adjusts the recording position of 7. The bidirectional printing apparatus according to claim 5, wherein the image type information is determined according to a statistical index value indicating a frequency of the plurality of types of dots recorded in one page. A bidirectional printing device. 8. Using a print head capable of recording a plurality of types of dots having different sizes in each pixel area on a print medium, a print image signal is printed while bidirectionally performing main scanning in a reciprocating manner. A bi-directional printing method for printing an image on the print medium according to the following, wherein at least two types of dots among the plurality of types of dots are reduced in a deviation of a recording position in a main scanning direction in a forward pass and a return pass. Adjustment values are set in advance, and using the adjustment values for one type of dot selected from the at least two types of dots, the plurality of types of dots in the main scanning direction in the forward pass and the return pass of the dots are used. A bidirectional printing method characterized by adjusting a recording position. 9. The bidirectional printing method according to claim 8, wherein at least one of the forward path and the return path is configured to reduce the deviation of the recording position of the selected one type of dot in the main scan direction between the forward path and the return path. On the other hand, a bidirectional printing method for adjusting the generation timing of the pulse of the drive signal. 10. The bidirectional printing method according to claim 9, wherein a timing of generating a pulse of the drive signal is adjusted by delaying the drive signal in at least one of a forward pass and a return pass. . 11. The generation method of a pulse of the drive signal according to claim 9, wherein a frequency of the drive signal is changed in at least one of a forward path and a return path along a main scanning direction. Adjust the bidirectional printing method. 12. The bidirectional printing method according to claim 8, wherein the at least two types of dots are provided in accordance with image type information indicating a type of an image represented by the print image signal. A two-way printing method, wherein one type of dot is selected from the following, and the adjustment value for the selected one type of dot is used. 13. The bidirectional printing method according to claim 12, wherein the image type information includes a natural image main image mainly including a natural image in one page, and an image other than the natural image in one page. A non-natural image-based image that is included as a main image and at least information for distinguishing between the main image and the non-natural image-based image. In addition to adjusting the recording position in the scanning direction, the recording position in the main scanning direction of the plurality of types of dots is adjusted so as to reduce the deviation of the recording position for a relatively large dot when recording the non-natural image main image. You want a two-way printing method. 14. The bidirectional printing method according to claim 12, wherein the image type information is determined according to a statistical index value indicating a frequency of the plurality of types of dots recorded in one page. , Bidirectional printing method. 15. A computer equipped with a printing device capable of recording a plurality of types of dots having different sizes in each pixel area on a print medium, and performs a main scan in a reciprocating manner and a print image. A computer-readable recording medium recording a computer program for printing an image on the print medium in response to a signal, wherein at least two types of dots among the plurality of types of dots are mainly used in an outward path and a return path. Among the adjustment values set in advance to reduce the deviation of the recording position in the scanning direction,
Selecting the adjustment value for one type of dot selected from the at least two types of dots; and using the selected adjustment value to determine the recording position of the plurality of types of dots in the main scanning direction in the forward path and the return path. A computer-readable recording medium on which a computer program for causing the computer to implement the adjusting function is recorded.