JP2002331692A - Printing with plurality of pixels used as unit for gradation reproduction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of improving freedom of local gradation reproductivity by ink discharging. SOLUTION: Gradation reproduction with the same ink is carried out by (i) setting N pixels (N is an integer of 2 or more) disposed continuously along one of a main scanning direction and a sub scanning direction as a unit for the gradation reproduction, (ii) setting the ink amount dischargeable to the position of at least one of the N pixels at a value different from the ink amount dischargeable to the other pixel positions, and (iii) reproducing the M gradations (M is an integer of N+2 or more) per N pixels by adjusting the ink amount at each pixel position of the N pixels.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a printing technique for performing printing by discharging ink droplets.

[0002]

2. Description of the Related Art In recent years, as an output device of a computer,
Ink jet printers that eject ink from a head are widely used. Further, the conventional ink jet type printer can reproduce each pixel in binary of ON / OFF, but in recent years, a multi-value printer capable of reproducing three or more values in one pixel has been proposed. A multi-valued pixel can be reproduced, for example, by adjusting the size of a dot formed at each pixel position. When forming dots of a plurality of sizes, a drive signal having a complex waveform that can selectively eject a plurality of different amounts of ink is used. Then, by shaping the drive signal, the ejection amount of ink at each pixel position is adjusted.

[0003]

However, when one type of drive signal is used, the amount of ink discharged per pixel can be changed to at most three steps. For this reason, the local tone reproducibility for each pixel is also limited by this. In other words, the local tone reproducibility by adjusting the ink ejection amount at each pixel has a problem that the degree of freedom is considerably low. On the other hand, if the degree of freedom in local gradation reproducibility can be increased, there is a possibility that higher-quality printing or higher-speed printing can be achieved. Therefore, a technique that can increase the degree of freedom of local gradation reproducibility has been desired.

The present invention has been made to solve the above-mentioned problems in the prior art, and has as its object to provide a technique capable of increasing the degree of freedom of local gradation reproducibility by discharging ink. And

[0005]

In order to solve at least a part of the above-described problems, the present invention provides a printing apparatus that performs printing on a printing medium while performing main scanning. A print head having a plurality of nozzles for ejecting ink, and a plurality of ejection drive elements for ejecting ink droplets from the plurality of nozzles,
A main scanning drive unit that performs a main scan by moving at least one of the print medium and the print head; a sub scan drive unit that performs a sub scan by moving at least one of the print medium and the print head; A head drive unit that supplies a drive signal to each ejection drive element according to
A control unit that controls each of the units. The control unit performs the tone reproduction by the same ink by: (i) reproducing N pixels (N is an integer of 2 or more) continuous in one of the main scanning direction and the sub-scanning direction. (Ii) setting the amount of ink that can be ejected to at least one pixel position of the N pixels to a value different from the amount of ink that can be ejected to another pixel position; A first print mode is provided by reproducing M gradations (M is an integer of N + 2 or more) for each of the N pixels by adjusting the amount of ink at each pixel position of the N pixels.

In this printing apparatus, N gradations (M ≧ M) are used by using N pixels continuous in one direction as one unit of gradation reproduction.
Since (N + 2) is reproduced, there is a great degree of freedom regarding the amount of ink ejected to each of the N pixels. Therefore, it is possible to realize gradation reproducibility different from the conventional one.

[0007] During one main scan, the head drive section controls each main scan only at intermittent pixel positions among pixel positions on each main scan line scanned by the plurality of nozzles. The plurality of ejection drive elements are driven so as to eject a predetermined amount of ink droplets set in advance, and when a plurality of main scans are performed on each main scan line, the N
Ink droplets for reproducing M gradation for each pixel may be ejected from the print head.

As described above, when ink droplets are ejected only at intermittent pixel positions during one main scan, it is better to perform multi-valued tone reproduction with N pixels as one unit. The number of main scans can be reduced as compared with the case where multi-level tone reproduction is performed every time. Therefore, it is possible to improve the printing speed.

[0009] The head driving section may discharge ink in a plurality of main scans at a position of at least one pixel among the N pixels.
Further, at the pixel position where the ink is ejected in an overlapping manner, the amount of ink ejected in each main scan may be different from each other.

According to this configuration, it is possible to further increase the degree of freedom in reproducing a multi-level gradation in which N pixels are defined as one unit.

The head drive section is provided with a common drive signal generation section capable of selectively generating one of a plurality of types of common drive signals for each main scan, and a common drive signal generation section. A drive signal shaping unit that generates the drive signal to be applied to each of the ejection drive elements by shaping the common drive signal for each pixel according to the print signal may be provided. At this time, the head driver changes the amount of ink ejected from the plurality of nozzles by changing the waveform of the common drive signal.

According to this configuration, it is possible to easily change the ink discharge amount.

The integer N is 2 and the integer M
Is preferably 4 or more.

According to this configuration, it is possible to reproduce many gradations in units of two pixels.

It is preferable that the pixel pairs, which constitute one unit of the tone reproduction, are arranged in opposite directions on adjacent main scanning lines.

According to this configuration, there is an advantage that dots are not displaced even in a uniform printed image.

In the darkest gray scale among the M gray scales that can be reproduced by the N pixels, it is preferable that an ink amount capable of solid printing the printing area on the print medium with the same ink is ejected.

According to this configuration, N pixels are set to 1 for gradation reproduction.
Even if the unit is used, a solid image can be reproduced.

It is preferable that the M gradations reproducible by the N pixels are set such that the lightness levels are substantially equally spaced.

According to this configuration, smooth gradation reproduction can be realized.

The control unit further has a second print mode for performing printing at a print resolution higher than that of the first print mode.
It is preferable that the smallest amount of ink that can be ejected to the position of the pixel corresponds to the amount of ink that can print the printing area on the print medium with the same ink in the second print mode.

According to this configuration, the number of types of ink ejected from the nozzles can be reduced, so that there is an advantage that control for ejecting ink becomes easy.

The method for adjusting the displacement according to the present invention comprises the steps of (a)
With respect to two types of dots having different sizes formed at different pixel positions in the main scanning direction by ink droplets having different ink amounts, the two types of dots are substantially aligned in the sub-scanning direction. Printing a first test pattern to be recorded; and (b) printing the first test pattern.
Determining a relative correction value of the positional deviation in the main scanning direction for the two types of dots according to the test pattern of
(C) correcting the relative positions of the two types of dots using the relative correction value when forming the two types of dots at different pixel positions in the main scanning direction during the printing. , Is provided.

According to this method, when a plurality of types of dots having different sizes are recorded at different pixel positions in the main scanning direction using ink droplets having different ink amounts, the positions in the main scanning direction are matched. It is possible to perform the positional deviation adjustment so as to perform the adjustment.

This method of adjusting the position shift further includes (d)
(E) printing a second test pattern for adjusting a positional shift in the main scanning direction between a forward pass and a return pass during bidirectional printing with respect to a predetermined reference dot of the two types of dots; A step of determining a reference correction value for a positional shift in the main scanning direction during bidirectional printing on the reference dot in accordance with a second test pattern. At this time, in the step (c), when the printing is performed bidirectionally, the positions of the two types of dots in the main scanning direction according to the relative correction value in the first path of the forward path and the backward path are determined. And a step of correcting the positions of the two types of dots in the main scanning direction according to the relative correction value and the reference correction value in a second path of the forward path and the return path. Is preferred

With this configuration, it is possible to correct the positional deviation during bidirectional printing using the reference correction value for the reference dot, and to use the reference correction value and the relative correction value for the other dots. Deviation can be corrected. As a result, with respect to a plurality of types of dots, it is possible to properly adjust the respective positional deviations.

The present invention can be realized in various modes, for example, a printing method and a printing apparatus, a printing control method and a printing control apparatus, a method and an apparatus for adjusting dot misalignment, and a method or a method thereof. It can be realized in the form of a computer program for realizing the functions of the device, a recording medium on which the computer program is recorded, a data signal including the computer program and embodied in a carrier wave, and the like.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described based on examples in the following order. A. Overall configuration of device: First Embodiment: C. First Embodiment Other embodiments: E. Adjustment of dot displacement Modified example

A. FIG. 1 is a block diagram showing the configuration of a printing system as an embodiment of the present invention.
This printing system includes a computer 90 and a color printer 20. The 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 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 performing image retouching and the like performs desired processing on an image to be processed.
An image is displayed on the CRT 21 via the.

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. In the example shown in FIG. 1, a resolution conversion module 97, a color conversion module 98, a halftone module 99,
Rasterizer 100 and color conversion lookup table L
And a UT.

The resolution conversion module 97 serves to convert the resolution of the color image data formed by the application program 95 into a 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 six gradation values. The halftone module 99 performs a so-called halftone process to generate halftone image data. The halftone image data is rearranged by the rasterizer 100 in the data order to be transferred to the printer 20, and the final print data PD
Is output as Note that the print data PD includes raster data indicating a dot formation state during each main scan and data indicating a sub-scan feed amount.

The printer driver 96 corresponds to a program for realizing the function of generating the print data PD. A program for realizing the function of the printer driver 96 is supplied in a form recorded on 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 punched card, a printed matter on which a code such as a barcode is printed, and an internal storage device of a computer (such as a RAM or ROM). memory)
Various computer-readable media such as an external storage device and the like can be used.

The computer 90 having the printer driver 96 has a function as a print control device that generates print data PD and supplies the print data PD to the printer 20 to perform printing.

FIG. 2 is a schematic configuration diagram of the printer 20. The printer 20 includes a sub-scan feed mechanism that conveys the printing paper P in the sub-scan direction by the paper feed motor 22, and a carriage 30 that controls the carriage 30 by the carriage motor 24.
A main scanning feed mechanism for reciprocating in the axial direction (main scanning direction) of the print head unit 6 mounted on the carriage 30
And a control circuit 40 for controlling the exchange of signals between the paper feed motor 22, the carriage motor 24, the print head unit 60 and the operation panel 32. Have. The control circuit 40 is connected to the computer 90 via the connector 56.

The sub-scan feed mechanism for conveying the printing paper P is
A gear train (not shown) for transmitting the rotation of the paper feed motor 22 to the platen 26 and a paper transport roller (not shown) is provided. The main scanning feed mechanism for reciprocating the carriage 30 includes an endless drive belt 36 provided between the carriage motor 24 and a slide shaft 34 erected in parallel with the axis of the platen 26 and slidably holding the carriage 30. And a position sensor 39 for detecting the origin position of the carriage 30.

FIG. 3 is a block diagram showing the configuration of the printer 20 with the control circuit 40 at the center. Control circuit 40
Is a CPU 41 and a programmable ROM (PROM)
43, a RAM 44, and a character generator (CG) 45 storing a character dot matrix. This control circuit 4
Reference numeral 0 further denotes an I / F dedicated circuit 50 for exclusively interfacing with an external motor or the like, and a head drive circuit 52 connected to the I / F dedicated circuit 50 for driving the print head unit 60 to eject ink. And paper feed motor 2
2 and a motor drive circuit 54 for driving the carriage motor 24. The I / F dedicated circuit 50 has a built-in parallel interface circuit.
Print data P supplied from the computer 90 via the
D can be received. The printer 20 performs printing according to the print data PD. The RAM 44
Functions as a buffer memory for temporarily storing raster data.

The CPU 41 functions as a "control unit" in a narrow sense for controlling the printing operation. Further, since the CPU 41, the PROM 43, and the RAM 44 in the control circuit 40 and the computer 90 perform various controls of the printing operation, they can be entirely included in the "control unit" in a broad sense.

The print head unit 60, the print head 2
8 and an ink cartridge 70 (FIG. 2) can be mounted. The print head unit 60
Are attached to and detached from the printer 20 as one component. That is, when attempting to replace the print head 28 would replace the print head unit 60.

FIG. 4 is an explanatory diagram showing the nozzle arrangement on the lower surface of the print head 28. On the lower surface of the print head 28, a nozzle group for ejecting black ink K, a nozzle group for ejecting dark cyan ink C, a nozzle group for ejecting light cyan ink LC, and a dark magenta ink M , A nozzle group for discharging the light magenta ink LM, and a nozzle group for discharging the yellow ink Y. Each nozzle is provided with a piezo element (not shown) as a discharge drive element.

FIG. 5 is a block diagram showing the internal configuration of the head drive circuit 52 (FIG. 3). Head drive circuit 52
Includes a common drive signal generation circuit 110 and a drive signal shaping circuit 120.

The common drive signal generation circuit 110 stores an R signal for storing waveform data indicating the waveform of the common drive signal COM.
The AM 112 has a common drive signal CO having an arbitrary waveform by DA conversion of the waveform data.
Generate M. The drive signal shaping circuit 120 masks a part or all of the common drive signal COM in accordance with the value of the serial print signal PRT, and provides a plurality of analog switches (not shown) for generating a drive signal DRV for each nozzle. Have. The shaped drive signal DRV is supplied to a piezo element 130 which is a drive element for each nozzle. In the example of FIG. 3, the drive signals DRV (1) to DRV (48) are generated according to the print signals PRT (1) to PRT (48) for each of the forty-eight piezo elements 130. .

The "common drive signal" means a drive signal commonly used for a plurality of nozzles. In the present embodiment, the same common drive signal COM is supplied to all of the six nozzle groups shown in FIG. However, a different common drive signal COM may be supplied for each nozzle group.

The common drive signal generation circuit 110 can select and generate one of a plurality of types of common drive signals having different waveforms for each main scan.
The formation of dots in each embodiment described below is performed using the function of the common drive signal generation circuit 110.

B. First Embodiment: FIGS. 6A to 6G
FIG. 4 is an explanatory diagram showing a drive signal waveform used in the first embodiment and how dots are formed. FIGS. 6A and 6B show a first common drive signal COM for forming a small dot SD.
1 shows the waveform of No. 1 and how small dots are formed.
Each rectangle in FIG. 6B represents one pixel, and here, four pixel positions P1 to P4 continuous on the main scanning line.
Is drawn. In this print mode, the print resolution in the main scanning direction is 360 dpi. First common drive signal C
OM1 is a signal in which a small dot pulse W1 is generated once for every other pixel. As shown in FIG. 6B, when forming a small dot SD, this pulse W1 is applied to the piezo element 130 (FIG. 5). On the other hand, when the small dots SD are not formed, the drive signal shaping circuit 120 (FIG. 5)
With this, the pulse W1 is masked. FIG. 6 (B)
In the example, small dots SD are formed at odd-numbered pixel positions P1 and P3. The ink amount of the small dot SD is 10 ng.

The reason why the pulse W1 for small dots is generated only every other pixel is that if the main scanning speed (carriage speed) is set to a high value to improve the printing speed, ink is ejected at all pixel positions. Because it is physically difficult. This will be described in more detail below. That is, the ink ejection frequency depends not only on the frequency of the drive signal but also on the mechanical natural frequency of the nozzle portion. Therefore, if the main scanning speed is set to a high value in order to improve the printing speed, the frequency of the pixels on the main scanning line during the main scanning becomes higher than the upper limit of the ink ejection frequency. In this case, since it is impossible to discharge ink at each pixel, ink is discharged every other pixel.

In order to improve the print quality, dot formation at all pixel positions on one main scan line is divided into several main scans rather than completed in one main scan. Is preferred. The reason for this is that, when the dot formation positions are shifted due to nozzle manufacturing errors, dot formation at all pixel positions on one main scanning line is performed with a plurality of nozzles rather than with only one nozzle. This is because the positional deviation of the dots is alleviated.

As can be understood from the above description, in each main scan, ink is ejected every other pixel on the main scan line, and dot formation on each main scan line is completed by a plurality of main scans. It is possible to improve both the printing speed and the printing quality.

FIGS. 6C and 6D show the waveform of the second common drive signal COM2 for forming the medium dot MD,
The state of formation of the medium dot MD is shown. The second common drive signal COM2 is also a signal in which a middle dot pulse W2 is generated once for every other pixel. However, medium dot MD
Are formed at even-numbered pixel positions P2 and P4. Medium dot MD
Is 20 ng.

FIGS. 6E and 6F show the waveform of the third common drive signal COM3 for forming the large dot LD.
This shows how large dots LD are formed. The third common drive signal COM3 is also a signal in which a large dot pulse W3 is generated once for every other pixel. Large dots LD are formed at even-numbered pixel positions P2 and P4. The ink amount of the large dot LD is 30 ng.

A small ink droplet for a small dot SD shown in FIG. 6B, a medium ink droplet for a medium dot MD shown in FIG. 6D, and a large ink droplet for a large dot LD shown in FIG. Ink droplets are ejected on the same main scanning line. On this main scan line, the first main scan for ejecting small ink droplets is called “pass 1”, the second main scan for ejecting medium ink droplets is “pass 2”, The third main scan for ejecting is referred to as “pass 3”. In addition, pass 1
And at least one sub-scan feed is performed between pass 2 and pass 2 and between pass 2 and pass 3, respectively. Therefore,
In three passes, different nozzles scan the same main scan line. However, it is also possible to execute each pass using the same nozzle without performing sub-scan feed.

On one main scanning line, small dots SD
Main scanning for ejecting small ink droplets is performed only once. Therefore, the small dots SD are formed only in one of two pixels. These two pixels are hereinafter referred to as “pixel pairs” or “pixel pairs”. In the examples of FIGS. 6A to 6G, pixel positions P1 and P2 form a pixel pair.
Pixel positions P3 and P4 also form a pixel pair. Small dot S
D is formed only at one specific pixel position in each pixel pair. Similarly, medium dot MD and large dot LD
Is formed only at a specific pixel position in any one of the pixel pairs.

FIG. 6 (G) shows small dots SD formed at odd-numbered pixel positions P1 and P3, respectively, and even-numbered pixel positions P2 and P3.
The state in which the large dots LD are formed at P4 is shown. In this state, a total of 40 ng of ink is ejected to the first pixel pair P1 and P2, and a total of 40 ng of ink is ejected to the second pixel pair P3 and P4. Note that the small dots SD are formed in pass 1, and the large dots LD are formed in pass 3.

When a total of 40 ng of ink is ejected to each pixel pair over a wide area as shown in FIG. 6G, a solid image is reproduced. FIG. 7 shows small dots SD and large dots L
FIG. 9 is an explanatory diagram showing a solid image reproduced by D. In the odd-numbered main scanning lines L1, L3, L5, small dots SD are formed at odd-numbered pixel positions P1, P3, and
Large dots LD are formed at even pixel positions P2 and P4. On the other hand, in the even-numbered main scanning lines L2 and L4, large dots LD are formed in odd-numbered pixel positions P1 and P3, and small dots SD are formed in even-numbered pixel positions P2 and P4. In other words, the small dots SD and the large dots LD are alternately formed in both the main scanning direction MS and the sub-scanning direction SS, and as a result, a solid image having no white portion is reproduced. In FIG. 7, for convenience of illustration, it appears that a gap remains between the small dot SD and the large dot LD, but there is no gap between them because ink actually spreads.

The arrangement of dots as shown in FIG. 7 is realized by arranging pixel pairs in opposite directions on adjacent main scanning lines. The use of such an arrangement has an advantage that a solid image can be easily reproduced. Further, in general, when a uniform print image is reproduced, dots are arranged almost uniformly without deviation, so that there is an advantage that image quality is improved.

The ink droplet for the small dot SD has an amount of ink capable of reproducing a solid image in a print mode with a print resolution of 720 dpi. Thus, 7
In the 20 dpi print mode (high-quality print mode), the solid image can be reproduced, but the ink amount is changed as shown in FIGS.
Print mode of 360 dpi (high-speed print mode)
Also, the configuration of the head drive circuit 52 (FIG. 5) can be simplified. In particular, the amount of data in the RAM 112 in the common drive signal generation circuit 110 can be reduced.

FIG. 8 is an explanatory diagram showing the ink ejection amount for each pixel pair in the first embodiment. The upper table in FIG.
The amount of ink droplets ejected in passes 1 to 3 and the pixel position where each ink droplet is ejected are shown. The lower table shows the relationship between the value of 3-bit halftone data and the total amount of ink ejected according to the halftone data. In this example, it can be understood that five gradations are reproduced in one pixel pair.

The "halftone data" is data obtained by the halftone processing in the halftone module 99 (FIG. 1), and is data representing the dot formation state for each ink color component. That is, the halftone data is data representing a local gradation with a pixel pair as one unit. The halftone data having one pixel pair as a unit is hereinafter referred to as “pixel pair halftone data”. In addition, halftone data in which one pixel is defined as one unit is referred to as “halftone data for one pixel”.

In this specification, the term “local gradation” means a gradation reproduced in a small local area of about one pixel to several pixels. On the other hand, a gray scale reproduced in a wide area including several tens to several hundreds of pixels is referred to as a “wide gray scale” or an “image gray scale”.

FIGS. 9A to 9C are explanatory diagrams showing the relationship between pixel pair halftone data, one-pixel halftone data, and dot formation. In this example, FIG.
As shown in (C), the dot formation state in each pixel pair is, in order from the left, no dot, only small dot SD,
Only medium dots MD, only large dots LD, small dots SD and large dots LD. The pixel pair halftone data shown in FIG. 9A also corresponds to this dot formation state. The pixel pair halftone data is shown in FIG.
The data is converted into three types of halftone data for one pixel shown in FIG. The halftone data for one pixel is 1-bit data indicating an on / off state for each pixel. This one
The pixel halftone data is supplied to the drive signal shaping circuit 120 as a serial print signal PRT (FIG. 5) for each pass.

The conversion from the pixel pair halftone data to the one pixel halftone data is performed by the printer 20.
Is performed by the CPU 41 in the control circuit 40 of FIG. However, the conversion between the halftone data may be performed by a dedicated hardware circuit, or may be performed in the printer driver 96 (FIG. 1). However, if the conversion between the halftone data is performed inside the printer 20, there is an advantage that the amount of data transfer from the computer 90 to the printer 20 can be reduced.

FIG. 10 is a flowchart showing the procedure of halftone processing using error diffusion. This procedure is executed by the halftone module 99 (FIG. 1) to perform the halftone processing on the odd-numbered main scanning lines L1, L3, and L5 in FIG.

In step S1, a pixel value Dodd at an odd pixel position is obtained. The pixel value Dodd is a value representing a gradation level of a specific ink, and has a value in the range of 0 to 255 in 8 bits, for example. In step S2, the pixel value Dodd is set to a first threshold value T for small dots.
Compare with h1. If the pixel value Dodd is equal to or greater than the first threshold value Th1, the formation state of the small dot SD at the odd pixel position is set to ON in step S3. In step S4, an error ΔD is obtained by subtracting the gradation level D (S-on) corresponding to the ON state of the small dot SD from the pixel value Dodd. On the other hand, the pixel value Dodd
Is less than the first threshold value Th1, the pixel value Dodd becomes the error ΔD as it is. Then, in step S5,
This error ΔD is diffused to surrounding pixels.

In step S6, a pixel value Deven at the next even pixel position is obtained. In step S7, the pixel value Deven is compared with the second threshold value Th2 for medium dots and the third threshold value Th3 for large dots. Pixel value D
If even is less than the second threshold value Th2, the pixel value Dev
en becomes the error ΔD as it is. On the other hand, when the pixel value Deven is equal to or more than the second threshold value Th2 and less than the third threshold value Th3, the formation state of the medium dot MD at the even pixel position is set to ON (step S8). , Medium dot M
An error ΔD is obtained by subtracting the gradation level D (M-on) corresponding to the ON state of D from the pixel value Deven (step S9). On the other hand, if the pixel value Deven is equal to or larger than the third threshold value Th3, the formation state of the large dot LD at the even pixel position is set to ON (step S1).
0) Further, an error ΔD is obtained by subtracting the gradation level D (L-on) corresponding to the ON state of the large dot LD from the pixel value Deven (step S11). Then, in step S12, the error ΔD is diffused to surrounding pixels.

When the dot formation state at the odd-numbered pixel position and the even-numbered pixel position forming the pixel pair is determined in this way, in step S13, the halftone data of the pixel pair is set according to the correspondence shown in FIG. You.

Incidentally, the even-numbered main scanning lines L in FIG.
In the halftone processing on L2 and L4, the pixel value Deven at the even pixel position is processed first, and then the pixel value Dodd at the odd pixel position is processed. Then, halftone data is set for a pixel pair composed of these two pixels.

As the halftone processing, processing methods other than error diffusion can be used. Further, in the example of FIG. 10, halftone data is obtained for each pixel pair after performing halftone processing for each pixel, but instead, halftone processing may be performed for each pixel pair. . However, if halftone processing is performed for each pixel and then halftone data is determined for each pixel pair as in the example of FIG. 10, it is expected that the gradation of an image can be reproduced more faithfully.

The main features of the first embodiment are as follows. (Feature 1) One unit of local tone reproduction is a pixel pair. (Feature 2) An ink droplet is ejected onto one of two pixel positions forming a pixel pair in an overlapping manner. (Feature 3) In one main scan, ink droplets are ejected only at intermittent pixel positions on the main scan line. (Characteristic 4) In one main scan, only a fixed amount of ink droplet set for each main scan can be ejected. (Feature 5) The ink droplet is ejected to approximately the center of each of two pixel positions forming a pixel pair.

The feature 1 means that the amounts of ink that can be ejected at two pixel positions forming a pixel pair are different from each other. On the other hand, in a conventional printing apparatus, 1
A pixel is used as one unit of local tone reproduction, and the amount of ink that can be ejected to each pixel is the same. According to the feature 1, the number of reproducible gradations can be increased as compared with the related art, and dots smaller than the related art can be used. Therefore, it is possible to improve the graininess of the image. Feature 2 has a function of increasing the number of reproducible tones in a pixel pair. Characteristic 3 is a constraint caused by increasing the main scanning speed as described above. Feature 4 has a function of facilitating control of ink ejection (particularly generation of a common drive signal). The feature 5 has a function of making it easy to match the positions of the dots in the main scanning direction in the forward path and the backward path in bidirectional printing, and as a result, it is possible to improve the image quality.

In the first embodiment, due to such various features, three main scans are performed on each main scan line, so that five gradations from a paper white state (no dots) to a solid state can be obtained. It is possible to reproduce. Note that it is not necessary that all of the above characteristics are satisfied, and it is also possible to construct an embodiment that does not have one or more of the characteristics 2 to 5.

FIGS. 11A to 11E are explanatory views showing how dots are formed in the comparative example. This comparative example differs from the first embodiment in that each pixel has the same gradation reproducibility. In FIG. 11, the drive signal waveform is omitted for convenience of illustration.

The ejection of the ink droplet is performed in the same manner as in the first embodiment.
It is performed every pixel. More specifically, in pass 1, a very small dot VSD (5 ng) is formed at an odd pixel position, and in pass 2
In this example, a very small dot VSD is formed at an even pixel position. In pass 3, small dots SD (10 ng) are formed at odd pixel positions, and in pass 4, small dots SD are formed at even pixel positions. As shown in FIG. 11E, the amount of ink that can be ejected to one pixel is in four stages of 0 ng, 5 ng, 10 ng, and 15 ng. That is, in this comparative example, four gradations can be locally reproduced. If the ink ejection amount of 20 ng per pixel is required to reproduce a solid image, two more main scans are required.

As described above, in the comparative example, four or more passes are required on one main scanning line in order to reproduce four gradations for each pixel. On the other hand, in the first embodiment shown in FIG. 6, if three passes are performed on one main scanning line, five gradations can be reproduced. The reason for this is
This is mainly because in the first embodiment, a pixel pair is one unit of gradation reproduction. That is, in the first embodiment, by using the pixel pair as one unit of the tone reproduction, it is possible to realize the same or higher tone reproducibility with a smaller number of passes than in the comparative example. Generally, since the printing speed is inversely proportional to the number of passes, the printing speed of the first embodiment is higher than that of the comparative example. Further, the first embodiment has the same or higher gradation reproducibility as the comparative example.

Further, the first embodiment has a higher degree of freedom in selection in several points than the comparative example. Specifically, the amount of ink ejected in each pass, the position of a pixel to be ejected in each pass (for example, any of even / odd pixel positions), and dot formation on one main scan line are completed. The number of passes required for
The embodiment has a higher degree of freedom in selection. In other words, the first embodiment has an advantage that the degree of freedom in local gradation reproduction by ink ejection is high.

C. Another embodiment: FIGS. 12 (A) to 12 (G)
FIG. 7 is an explanatory diagram showing a drive signal waveform and a dot formation state used in the second embodiment, and corresponds to FIGS. 6A to 6G. In the second embodiment, in pass 1,
Small dots SD (10 ng) are formed at odd pixel positions (FIGS. 12A and 12B). In pass 2, small dots SD are formed at even pixel positions (FIG. 12C,
(D)). In pass 3, a medium dot MD (20 ng) is formed at an even pixel position (FIG. 12E,
(F)).

FIG. 12G shows four pixel positions P1 to P
4 shows a state in which ink droplets for small dots SD are respectively ejected, and ink droplets for medium dots MD are respectively ejected in even-numbered pixel positions P2 and P4. First pixel pair P
40 ng of ink is discharged to each of the first and second pixel pairs P3 and P4.

FIGS. 6A to 6G and FIGS.
As can be understood from comparison with (G), in the first embodiment, the ink amounts ejected in the three passes are different from each other.
In the second embodiment, the amount of ink ejected in pass 1 and pass 2 is the same. As in the second embodiment, even when the same amount of ink is ejected in some main scans among a plurality of main scans performed on one main scan line, the number of passes is the same as in the first embodiment. Can reproduce the same number of gradations. From this, it can be understood that the degree of freedom in local gradation reproducibility using a pixel pair is high.

FIG. 13 is an explanatory diagram showing the ink ejection amount for each pixel pair in the second embodiment. In the second embodiment as well, as in the first embodiment, 5
Two gradations can be reproduced.

FIG. 14 is an explanatory diagram showing the ink ejection amount for each pixel pair in the third embodiment. In the third embodiment,
Small dot SD (6 ng) at odd pixel position in pass 1
Are formed. In pass 2, medium dots MD (12 ng) are formed at even-numbered pixel positions, and in pass 3, large dots LD (22 ng) are formed at odd-numbered pixel positions. FIG.
As can be understood from the table below, in the third embodiment, it is possible to discharge ink amounts of 0 ng, 6 ng, 12 ng, 22 ng, and 40 ng per pixel pair.
Also in the third embodiment, as in the first embodiment, five gradations can be reproduced in one pixel pair. Further, it is possible to discharge an ink amount (40 ng per pixel pair) necessary for reproducing a solid image. The waveform of the common drive signal used in the third embodiment is not shown.

FIG. 15 is a graph showing the relationship between the ink ejection amount per pixel pair and the lightness level L of an image in the third embodiment. In the third embodiment, locally reproducible gradations are 0 ng, 6 ng, 12 ng, 22 ng, and 40 ng.
There are five gradations corresponding to five ink amounts of ng. The lightness PW when the ejection amount is 0 ng is the lightness of the print medium itself, and is called “paper white”. As can be understood from this figure, in the third embodiment, the lightness levels L of the five gradations reproducible by the pixel pair are set so as to be substantially equally spaced from each other. By setting the gradation at equal intervals in this way, smooth gradation reproduction is possible,
There is an advantage that the image quality is improved. In the present specification, “lightness is substantially equally spaced” means that the brightness interval ΔL is
It means that the average value is within the range of ± 20%. However,
When the lightness interval ΔL is in the range of the average value ± 10%, the lightness may be referred to as “substantially equal intervals”.

Incidentally, the second and third embodiments are also similar to the first embodiment.
It has the features 1 to 5 described in the embodiment. Therefore, similarly to the first embodiment, the second and third embodiments also have an advantage that it is possible to reproduce a tone equal to or higher than that of the comparative example with a smaller number of passes than the comparative example.
Further, there is an advantage that the degree of freedom of local gradation reproducibility due to ink ejection is high.

D. Dot Position Displacement Adjustment In the various embodiments described above, each dot is assumed to be correctly formed at the center of a pixel. However, in practice, the positions of dots having different sizes in the main scanning direction are different from each other.
There may be a relative deviation. FIG. 16A shows a state where the relative positions of the large dot LD and the small dot SD are shifted from the normal state. In FIG. 16A, a grid that divides pixels based on the position of the large dot LD is drawn, and it can be understood that the position of the small dot SD is slightly shifted to the right from the center of the pixel. However, in this case as well, FIG.
As shown in FIGS. 6 (B) and 6 (C), the waveforms of the respective drive signals are generated at regular timings. FIG. 16 (A)
The reason why the positions of the dots are shifted as described above is that the ejection speed and the ejection direction of the ink droplets are slightly shifted due to a manufacturing error of the nozzle or the like.

When the relative positions of the large dot LD and the small dot SD are shifted in this way, for example, as shown in FIG. 16D, the timing of generating the drive signal for the small dot is adjusted by an appropriate correction value ΔT. Correct it. As described in FIGS. 6A to 6G, dots of different sizes are formed in different passes. Therefore, for example, in the path for forming the small dot SD, the drive signal generation timing is changed as shown in FIG.
By adjusting as described above, the relative positional deviation can be reduced.

FIG. 17 shows an example of a test pattern for adjusting the relative positional deviation between the large dot LD and the small dot SD. This test pattern includes five linear sub-patterns. Each sub-pattern is recorded in a state in which large dots LD and small dots SD are alternately arranged substantially in a line along the sub-scanning direction SS.
Both the large dot LD and the small dot SD are formed on the outward path. In the five sub-patterns, small dots S
The ink ejection timing for D differs by a fixed amount δ, and the relative positions of the large dot LD and the small dot SD are slightly shifted accordingly. Under each sub-pattern, values 1 to 5 of the relative position adjustment number Vrel are printed. The values 1 to 5 of the relative position adjustment numbers Vrel are relative correction values ΔT (1) to ΔT of the positional deviation of the small dots SD.
(5) is associated in advance. Note that the relative position adjustment number Vrel is actually printed as a large character having several tens of dots on one side, but is drawn with a small number in FIG. 17 for convenience of illustration.

When adjusting the relative positional deviation, such a test pattern is printed by the printer 20, and the user selects and sets the relative position adjustment number Vrel indicating the most appropriate adjustment state in the printer 20. FIG. 18 is an explanatory diagram showing the relationship between the relative position adjustment number Vrel selected in the test pattern and the positional deviation correction at the time of printing. In this example,
As shown in FIG. 18A, when the value of the relative position adjustment number Vrel is 4, the relative positions of the large dot LD and the small dot SD match. However, in the test pattern, the large dots LD and the small dots SD are arranged along the sub-scanning direction, whereas during actual printing, the large dots LD and the small dots SD are arranged as shown in FIG. It is formed at an adjacent pixel position (see also FIG. 6G). Therefore, at the time of actual printing, as shown in FIG. 18B, the timing of the small dot SD is determined by the correction value T obtained by adding the reference deviation amount T0 for one pixel and the relative correction value ΔT (4). Adjusted. By doing so, it is possible to match the positions of the large dots LD and the small dots SD in the main scanning direction.

In the example described above, the position of the small dot SD is corrected, but the position of the large dot LD may be corrected instead. It is preferable that the relative positions of the medium dot MD and the large dot LD or the small dot SD are matched by the same procedure.

When the printer 20 performs the bidirectional printing, the positional deviation caused by the bidirectional printing is adjusted.
FIG. 19 is a flowchart showing the procedure for adjusting the dot misalignment during bidirectional printing. In step S21, a test pattern for adjusting the relative position deviation is printed on the forward path and the return path, respectively. In step S22, an appropriate relative position adjustment number is input to the printer 20. The test pattern for adjusting the relative displacement is the same as that shown in FIG. However, at the time of bidirectional printing, since printing is performed on both the forward path and the backward path, a test pattern is printed for each of the forward path and the backward path, and the relative position adjustment number Vrel (that is, the relative correction value) is also determined for each of the forward path and the backward path. Is done. Instead of printing a test pattern on both the forward path and the return path to set the relative correction value, it is also possible to use the relative correction value on the forward path for the return path. However, the positive and negative signs of the relative correction value are reversed between the forward path and the return path.

In step S23, a test pattern for adjusting the reference position deviation during bidirectional printing is printed. FIG.
FIG. 4 is an explanatory diagram illustrating an example of a test pattern for adjusting a reference position shift. This test pattern includes five linear sub-patterns formed only by the large dots LD. Each sub-pattern has an upper straight part U recorded on the outward path.
L, and a lower straight line portion LL recorded on the return path. In the five sub-patterns, the timing of ink ejection for the large dots LD forming the lower linear portion LL differs by a fixed amount, and accordingly, the upper linear portion UL
And the relative position between the lower straight portion LL and the lower straight portion LL are slightly shifted. Below each linear pattern is a reference position adjustment number Vre
The values 1 to 5 of f are printed. Each reference position adjustment number V
The values 1 to 5 of rel are previously associated with the reference correction values.

Reference position adjustment number Vref for bidirectional printing
Is determined for one reference dot (large dot LD in the example of FIG. 20) among a plurality of dots having different sizes. With respect to the reference dot LD, the positional deviation in the main scanning direction during bidirectional printing is corrected with a reference correction value corresponding to the reference position adjustment number Vref. Other dots (Medium dot MD
And small dot SD), this reference correction value and
The relative correction values determined in steps S21 and S22 are added to determine a correction value for bidirectional printing.

After the relative correction value and the reference correction value are determined in this way, when the user instructs to execute printing in step S25, printing is performed while performing positional deviation correction in step S26. Specifically, on the outbound route,
Using only the relative correction value, the positional deviation in the main scanning direction between a plurality of types of dots having different sizes is corrected.
The positional deviation is corrected using the relative correction value and the reference correction value. However, conversely, the position deviation correction may be performed using the relative correction value and the reference correction value on the outward path, and the position deviation adjustment may be performed using only the reference correction value on the return path.

The setting of the relative correction value and the reference correction value according to the procedure shown in FIG. 19 may be performed at the time of assembling the printer 20, or may be performed by the user of the printer 20. Good. Alternatively, one of the relative correction value and the reference correction value may be performed at the time of assembling the printer 20, and the other may be performed by the user.

FIG. 21 is a block diagram showing a main configuration relating to misalignment adjustment during bidirectional printing. Printer 20
In the PROM 43, the reference position adjustment number Vref, the relative position adjustment number Vrel, and the reference correction value table 204 are stored.
And a relative correction value table 206 are stored. The adjustment numbers Vref and Vrel are calculated in steps S22 and S22 in FIG.
24. Reference correction value table 20
4 is a table storing the relationship between the reference position adjustment number Vref and the reference correction value. Relative correction value table 206
Is a table showing the relationship between the relative position adjustment number Vrel and the relative correction value.

The RAM 44 in the printer 20 stores a computer program having a function as a position shift correction execution unit (adjustment value determination unit) 210 for correcting a position shift of a dot in the main scanning direction. The position shift correction execution unit 210 supplies a timing adjustment value T corresponding to the relative correction value to the head drive circuit 52 on the outward path, and adjusts the timing adjustment value based on both the relative correction value and the reference correction value on the return path. The value T is supplied to the head drive circuit 52. The timing of generating the drive signal is determined based on the origin position of the carriage detected by the position sensor 39. Further, the timing adjustment value T in each pass is determined according to the type of dot recorded in that pass. The head drive circuit 52 corrects the generation timing of the drive signal in each path according to the timing adjustment value T.

As described above, in the procedure shown in FIG. 19, the positional deviation of the reference dots LD in the main scanning direction during the main scanning printing is corrected by the reference correction value.
Since the positional deviation between the dot and the other dots SD and MD is corrected by the relative correction value, it is possible to match the positions of the dots during bidirectional printing. As described with reference to FIGS. 18A and 18B, the large dot LD and the small dot SD are recorded at different positions along the main scanning direction during actual printing, but the relative correction value is determined. In this case, recording is performed substantially in a line along the sub-scanning direction so as to take the same main scanning position.
This has an advantage that an appropriate relative correction value can be easily determined.

Although the large dot LD is used as the reference dot in the above-described example, the medium dot MD and the small dot SD can be used as the reference dot.

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

E1. Modified Example 1: In each of the above embodiments, the ejection of ink droplets on one main scanning line is completed by three main scans, but the number of main scans performed on one main scanning line is three. The number is not limited to four and may be four or more.

E2. Modification Example 2 In each of the above embodiments, the pixel pair is configured by pixels that are continuous in the main scanning direction. However, the pixel pair may be configured by pixels that are continuous in the sub-scanning direction. In each of the above embodiments, a pixel pair is used as one unit of local tone reproduction. However, three or more consecutive pixels can be used as one unit of local tone reproduction. In general, N pixels (N is an integer of 2 or more) continuous in one of the main scanning direction and the sub-scanning direction may be set as one unit of tone reproduction. At this time, the amount of ink that can be ejected to at least one pixel position of the N pixels is set to a value different from the amount of ink that can be ejected to other pixel positions.

In each of the above embodiments, the number of locally reproducible tones is set to 5. However, the number of tones may be set to 4, or may be set to 6 or more. In general,
By adjusting the amount of ink at each pixel position of the N pixels, M gradations (M is an integer of N + 2 or more) may be reproduced by the N pixels.

E3. Modification 3: The present invention is also applicable to a drum scan printer. In a drum scan printer, the drum rotation direction is the main scanning direction, and the carriage traveling direction is the sub scanning direction. In addition, the present invention can be applied not only to an ink jet printer but also to a printing apparatus that generally prints on the surface of a print medium using a print head having a plurality of nozzles. Such printing devices include, for example, facsimile machines and copy machines.

E4. Modification 4: In the above embodiment, a part of the configuration realized by hardware may be replaced by software, and conversely, a part of the configuration realized by software may be replaced by hardware. You may. For example, the control circuit 40
A part of the functions shown in FIG. 2 may be executed by the host computer 90.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram illustrating a configuration of a printer.

FIG. 3 is a block diagram showing a configuration of a control circuit 40 in the printer 20.

FIG. 4 is an explanatory diagram showing a nozzle arrangement on a lower surface of a print head.

FIG. 5 is a block diagram showing an internal configuration of a head drive circuit 52 (FIG. 2).

FIG. 6 is an explanatory diagram showing a drive signal waveform used in the first embodiment and how dots are formed.

FIG. 7 is an explanatory diagram showing a solid image reproduced by a small dot SD and a large dot LD.

FIG. 8 is an explanatory diagram showing an ink ejection amount for each pixel pair in the first embodiment.

FIG. 9 is an explanatory diagram showing a relationship between pixel pair halftone, one-pixel halftone data, and dot formation.

FIG. 10 is a flowchart illustrating a procedure of a halftone process.

FIG. 11 is an explanatory diagram showing how dots are formed in a comparative example.

FIG. 12 is an explanatory diagram showing a drive signal waveform used in the second embodiment and how dots are formed.

FIG. 13 is an explanatory diagram showing an ink ejection amount for each pixel pair in the second embodiment.

FIG. 14 is an explanatory diagram showing an ink ejection amount for each pixel pair in the third embodiment.

FIG. 15 is a graph showing a relationship between an ink ejection amount per pixel pair and a lightness level L of an image in the third embodiment.

FIG. 16 is an explanatory diagram showing a state in which the relative positions of large dots and small dots are shifted.

FIG. 17 is an explanatory diagram showing a test pattern for adjusting the relative positional deviation between large dots and small dots.

FIG. 18 is an explanatory diagram showing a relationship between a relative position adjustment number and a position shift correction during printing.

FIG. 19 is a flowchart showing a procedure for adjusting dot displacement during printing.

FIG. 20 is an explanatory diagram showing a test pattern for adjusting a reference position shift.

FIG. 21 is a block diagram illustrating a main configuration related to positional deviation adjustment during bidirectional printing.

[Explanation of symbols]

 Reference Signs List 20 color printer 21 CRT 22 paper feed motor 24 carriage motor 26 platen 28 print head 30 carriage 32 operation panel 34 sliding shaft 36 drive belt 38 pulley 39 position sensor 40 control circuit 41 ... CPU 43 ... PROM 44 ... RAM 50 ... I / F exclusive circuit 52 ... Head drive circuit 54 ... Motor drive circuit 56 ... Connector 60 ... Print head unit 70 ... Ink cartridge 90 ... Computer 91 ... Video driver 95 ... Application program 96 ... Printer driver 97 ... Resolution conversion module 98 ... Color conversion module 99 ... Half tone module 100 ... Rasterizer 110 ... Common drive signal generation circuit 112 ... RAM 120 ... Drive signal shaping circuit 130 ... Piezo element 204 ... Reference correction value table 206 ... Relative correction value table 210 ... Position shift correction execution unit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04N 1/23 101 F term (reference) 2C056 EA04 EB27 EC35 EC77 EC78 EC80 ED01 ED02 ED03 ED07 ED09 FA04 FA11 HA58 2C057 AF30 AF32 AF39 AG12 AL36 AM16 AN02 AR08 BA03 BA14 CA01 CA04 CA07 CA09 5B021 AA01 BB00 LG08 5C074 AA05 BB16 DD05 DD15 EE04 GG09

Claims (13)

[Claims] 1. A printing apparatus for performing printing on a print medium while performing main scanning, comprising: a plurality of nozzles for discharging the same ink; and a plurality of nozzles for discharging ink droplets from the plurality of nozzles. A main scanning drive unit that performs main scanning by moving at least one of the printing medium and the printing head; and a sub-scanning unit that moves at least one of the printing medium and the printing head. A sub-scanning drive unit that performs scanning, a head drive unit that supplies a drive signal to each ejection drive element in accordance with a print signal, and a control unit that controls each of the units. Tone reproduction by ink
(I) N pixels (N is an integer of 2 or more) continuous along one of the main scanning direction and the sub-scanning direction are set as one unit of gradation reproduction, and (ii) of the N pixels Setting the amount of ink that can be ejected to at least one pixel position to a value different from the amount of ink that can be ejected to another pixel position; (ii)
i) having a first print mode performed by reproducing M gradations (M is an integer of N + 2 or more) for each of the N pixels by adjusting the amount of ink at each pixel position of the N pixels. Characteristic printing device. 2. The printing apparatus according to claim 1, wherein the head driving unit is configured to output a plurality of nozzles from one of the pixel positions on each main scan line scanned by the plurality of nozzles during one main scan. Driving the plurality of ejection driving elements so as to eject a predetermined amount of ink droplets preset for each main scan only at intermittent pixel positions, and performing multiple main scans on each main scan line A printing apparatus for discharging, from the print head, ink droplets for reproducing M gradations for each of the N pixels when the above is performed. 3. The printing apparatus according to claim 2, wherein the head driving unit is configured to control at least one of the N pixels.
A printing apparatus that ejects ink in a plurality of main scans at one pixel position in a superimposed manner. 4. The printing apparatus according to claim 3, wherein the amount of ink ejected in each main scan is different from each other at pixel positions where the ink is ejected in a superimposed manner. 5. The printing apparatus according to claim 4, wherein the head drive section generates a common drive signal capable of selectively generating any one of a plurality of types of common drive signals for each main scan. Drive signal shaping for generating the drive signal given to each of the ejection drive elements by shaping the common drive signal supplied from the common drive signal generation unit for each pixel according to the print signal. A printing device, comprising: a head drive unit that changes an amount of ink ejected from the plurality of nozzles by changing a waveform of the common drive signal. 6. The printing apparatus according to claim 1, wherein the integer N is 2 and the integer M is 4 or more. 7. The printing apparatus according to claim 6, wherein the pixel pairs as one unit of the tone reproduction are arranged in an opposite direction on an adjacent main scanning line. 8. The printing apparatus according to claim 1, wherein a print area on the print medium is set at a darkest gray level among M gray levels that can be reproduced by the N pixels. A printing apparatus that discharges an ink amount that can be solid printed with the same ink. 9. The printing apparatus according to claim 1, wherein the M gradations reproducible by the N pixels are set such that lightness levels are substantially equally spaced. apparatus. 10. The printing apparatus according to claim 1, wherein the control unit further includes a second print mode for performing printing at a print resolution higher than the first print mode. The least ink amount that can be ejected to the position of the N pixel in the first print mode is that the same ink can be used to solidly print a print area on the print medium in the second print mode Printing device equivalent to a large amount of ink. 11. Performing main scanning using a print head having a plurality of nozzles for ejecting the same ink and a plurality of ejection drive elements for ejecting ink droplets from the plurality of nozzles, respectively. A printing method for printing on a print medium, comprising: (i) N pixels (N is 2 or more) continuous in one of the main scanning direction and the sub-scanning direction, (Ii) is set as one unit of tone reproduction, and (ii) the amount of ink that can be ejected to at least one of the N pixels is different from the amount of ink that can be ejected to other pixel positions. (Iii) adjusting the amount of ink at each pixel position of the N pixels to reproduce M gradations (M is an integer of N + 2 or more) for each of the N pixels. The printing method you want. 12. While performing main scanning using a print head having a plurality of nozzles for ejecting the same ink and a plurality of ejection drive elements for ejecting ink droplets from the plurality of nozzles, respectively. When printing on a print medium, a method for adjusting the positional deviation in the main scanning direction of two types of dots having different sizes formed by ink droplets having different ink amounts, wherein the printing is performed using the same printing method. Tone reproduction by ink
(I) N pixels (N is an integer of 2 or more) continuous along one of the main scanning direction and the sub-scanning direction are set as one unit of gradation reproduction, and (ii) of the N pixels Setting the amount of ink that can be ejected to at least one pixel position to a value different from the amount of ink that can be ejected to another pixel position; (ii)
i) adjusting the amount of ink at each pixel position of the N pixels to reproduce M gradations (M is an integer of N + 2 or more) for each of the N pixels; The ejection drive elements are preset for each main scan only at intermittent pixel positions among pixel positions on each main scan line scanned by the plurality of nozzles during one main scan. The displacement adjustment method is as follows: (a) two ink droplets having different sizes formed at different pixel positions in the main scanning direction by ink droplets having different ink amounts; Printing a first test pattern recorded in a state where the two types of dots are substantially aligned in a sub-scanning direction with respect to the types of dots; and (b) the first test pattern Determining a relative correction value of the positional deviation in the main scanning direction with respect to the two types of dots according to (c) forming the two types of dots at different pixel positions in the main scanning direction during the printing Correcting the relative positions of the two types of dots using the relative correction value. 13. The dot displacement adjusting method according to claim 12, further comprising: (d) determining a predetermined reference dot of the two types of dots in a forward pass and a return pass in bidirectional printing. A step of printing a second test pattern for adjusting the positional deviation in the scanning direction; and (e) a reference for a positional deviation in the main scanning direction during bidirectional printing on the reference dot in accordance with the second test pattern. Determining a correction value. The step (c) includes the step of determining the two types according to the relative correction value in a first path of the forward path and the return path when the printing is performed in two directions. Correcting the position of the dot in the main scanning direction, and in the second path of the forward path and the return path, the position of the two types of dots in the main scanning direction according to the relative correction value and the reference correction value. Correct And adjusting the dot misalignment.