JP3478573B2 - Image recording method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording method and apparatus, for example, an ink jet type image recording method and apparatus for recording by ejecting ink from a recording head.

[0002]

2. Description of the Related Art Generally, an image output device such as a printer, a copying machine or a facsimile is constructed so as to record an image consisting of a dot pattern on a recording material such as paper or a plastic thin plate based on image information. Has been done. This type of recording apparatus can be classified into an inkjet type, a wire dot type, a thermal type, a laser beam type, and the like, depending on the recording method. Among them, the inkjet type (inkjet recording apparatus) uses ink ( A recording liquid) droplet is ejected and ejected, and the droplet is attached to a recording material for recording.

In recent years, many image output devices have been used, and high speed recording, high resolution, high image quality, low noise, etc. are required for these image output devices. As an example of a recording device that meets such a demand, the inkjet recording device can be cited. In the inkjet recording apparatus, since recording is performed by ejecting ink from the recording head, it is necessary to stabilize ink ejection to satisfy the above requirements. Conventionally, ink ejection is stabilized by the following means.

The ejection port of the recording head is provided with a cap, which is used when performing a suction recovery operation for sucking ink from the ejection port to eliminate ejection failure and for preventing ink from drying at the ejection port. Therefore, the discharge port was capped. In addition, as the ink is ejected, ink that bounces off the recording medium near the ejection port or mist that occurs during ejection is accumulated, and this accumulated ink is connected to the ejection port, causing ejection failure such as ejection failure or twisting. There are cases. In order to prevent this, the surface of the recording head (face surface) is wiped with a wiping member such as urethane rubber to wipe off the ink on the surface. The wiping performance of the wiping member depends on the material and mechanical setting conditions, but it is necessary to clean the surface of the wiping member itself in order to constantly maintain the performance. As a means for this, a cleaning mechanism that presses a wiping member against an absorber or the like to absorb the ink scraped by wiping is often provided.

However, although the ink jet recording apparatus attempts to stabilize the ink ejection as described above, the quality of an image to be recorded largely depends on the performance of the recording head alone. Small differences that occur during the manufacturing process of the recording head, such as the shape of the ejection port of the recording head and the variation of the electrothermal converter (ejection heater), affect the ejection amount and ejection direction of the ejected ink, respectively. Has caused deterioration of the image quality as uneven density of the formed image.

A specific example of image deterioration due to the above-mentioned slight difference in the recording head will be described below with reference to FIGS. 7 and 8. In FIG. 7, reference numeral 1101 denotes a multi-head of the inkjet recording apparatus, which has eight nozzles 110 for simplicity.
It is assumed to be composed of 2. Reference numeral 1103 denotes an ink drop ejected by the nozzle 1102.

As shown in FIG. 7, each ink drop 11 is ejected from each nozzle 1102 in the same direction and in the same direction.
Ideally, 03 is discharged. If (a) in FIG.
If the ideal ejection is performed as shown in FIG. 7, dots of uniform size are landed on the paper surface as shown in FIG. 7B, and an image without density unevenness is obtained as a whole. .
In this case, the density distribution of the landed dots in the nozzle arrangement direction is substantially uniform, as shown in FIG.

However, as described above, each nozzle actually has variations. An example thereof is shown in FIG. In FIG. 8, the reference numerals are the same as those in FIG. Actually, as shown in FIG. 8A, since the size and direction of the ink drop ejected from each nozzle 1102 varies, if the same printing as described above is performed as it is. On the paper surface, it is landed as shown in FIG. According to FIG. 8 (b), in the head main scanning direction, there are periodically blank areas that do not satisfy the area factor of 100%, and conversely, dots are overlapped more than necessary and black streaks occur. Or, a white streak as shown in the center of FIG. 8B is generated. In this case, the density distribution of the landed dots in the nozzle arrangement direction is as shown in FIG.

As a result of the above, in the conventional ink jet recording apparatus, the phenomenon shown in FIG. 8 is perceived as density unevenness as seen by human eyes. As a measure against the above-mentioned density unevenness, a method as described below has been conventionally devised, and the method will be described below with reference to FIGS. 9 and 10. FIG. 9 shows an example in which printing is executed by the multi-pass printing method described below using the multi-head 2001 having the variation shown in FIG.

FIG. 9A shows three scans by the multi-head 2001. In FIG. 9A, the reference numerals are the same as those in FIG. The print area is shown in FIGS.
9 (b), in order to complete as shown in FIG. 9 (b), the multi-head 2001 is set to 3 in FIG. 9 (a).
Although the scan is performed twice, the print area in units of 4 pixels, which is half of the multi-head 2001, is completed by two scans, that is, two passes.

In FIG. 9, the eight nozzles of the multi-head 2001 are divided into two groups of four nozzles at the top and four nozzles at the bottom, and the dots printed by one scan in one group are defined by prescribed image data. , Thinned out to about half. Then, at the time of the second scan, the dots of the other half of the image data are embedded, and the printing of the 4-pixel unit area is completed. The recording method as described above is hereinafter referred to as a multi-pass recording method.

Using the multi-pass printing method described above,
Even if a multi-head that is the same as the multi-head with variations shown in FIG. 8A is used, the effect of variations unique to each nozzle on the printed image is halved, so the printed image is shown in FIG. As shown in FIG. 8B, the black streak and the white streak as seen in FIG. 8B become less noticeable. Therefore, the density distribution of the landed dots in the nozzle array direction is
As shown in FIG. 9C, the density unevenness is considerably reduced compared to FIG. 8C.

When printing is performed by the multi-pass printing method as described above, in the first scan and the second scan, the image data is divided according to a predetermined array so as to fill each other. ), It is most common to use a zigzag pattern that exactly forms a zigzag pattern for each vertical and horizontal pixel as shown in FIG.

Therefore, the unit printing area (here, in units of 4 pixels) is completed by the first scan for printing the zigzag lattice and the second scan for printing the inverse zigzag lattice.
An example of printing by thinning out the zigzag pattern will be described in detail with reference to FIG. 10 (a), 10 (b), and 10 (c) show how the recording of a certain fixed area is completed when using the zigzag and inverse zigzag patterns, respectively. This is explained using a multi-head having eight nozzles 1102.

First, in the first scan shown in FIG. 10A, the lower four nozzles are used to form a zigzag pattern (marked with diagonal lines).
Record. Next, in the second scan shown in FIG. 10B, paper feeding is performed only for 4 pixels (1/2 of the head length), and an inverted zigzag pattern (white circle mark) is recorded. Furthermore, FIG.
In the third scan shown in 0 (c), the paper is fed again for only 4 pixels (1/2 of the head length), and the staggered pattern is printed again. In this manner, the paper feed in units of 4 pixels and the recording in the staggered and reverse zigzag patterns are alternately performed in this manner, thereby completing the recording area in units of 4 pixels for each scan.

Regarding the thinning-out using the above-mentioned houndstooth pattern, JP-A-60-214670, JP-A-60-214671 and U
It can be referred to in SP4622561, USP4963882, and USP4967203. An example of electrical control in the case of performing thinning printing using the above-mentioned houndstooth pattern will be described below with reference to FIGS. 11 and 12. FIG. 11 shows a control configuration for generating the above-mentioned zigzag and inverse zigzag patterns.
The head unit 900 transfers the print data Si to the 8-bit shift register 901 according to the print data synchronization clock CLKi.
Set to. Then, the LATCH * signal is output and the print data set in the shift register 901 is latched in the latch 902. After that, the BEi1 *, BEi2 *, BEi3 *, and BEi4 * signals are turned on to drive the transistor array 903 of the head unit 900, heat the heater 904, and perform printing. The CARESi * signal is a reset signal that clears the latch of the latch 902. One heat
Start with Heat Trigger signal, from pulse generator 905
Outputs BEi1 *, BEi2 *, BEi3 *, BEi4 * signals.

In order to perform thinning, the flip-flop 906 is hit with a Heat Trigger signal to change the masking signals (BEi1 * and BEi3 *) alternately for each heat.
A timing chart in the above control is shown in FIG. Actually, as shown in the timing chart of FIG. 12, the masked signal is controlled to be High / Low of the output signal DATAENB of the flip-flop 906. In Figure 12, when Heat Trigger signal is applied, BEi1 *, BEi2 *, BEi3
*, BEi4 * signal goes low and each nozzle heats up. The masked timing is written with a broken line in the figure and corresponds to the DATAENB signal. With EVEN signal
The ODD signal is a signal for initial mask pattern setting. For lines that you want to print in a zigzag pattern, if you send the EVEN signal before printing one line, the flip-flop is preset and the BEi1 * and BEi3 * signals are turned on first. Next, staggered printing becomes possible. Also, in the line where you want to print in the reverse zigzag pattern, if you send the ODD signal before printing one line, the flip-flop will be reset and the BEi2 *, BEi4 * signals will be turned on first to enable reverse zigzag printing.

As described above, in the ink jet recording apparatus, there has been conventionally known a technique of eliminating unevenness in printing density by a multi-pass recording method.

[0019]

However, even when the multi-pass printing as described above is performed, the density unevenness is not completely eliminated depending on the duty, or new density unevenness is confirmed especially in the halftone. The problem to do has occurred conventionally. The present invention has been made to solve this problem. Hereinafter, the problem that has occurred conventionally will be described in detail with reference to FIGS.

Generally, the image data received by the printer is already regularly arranged. On the recording device side, a certain amount of that data is accumulated in a buffer, and a new mask (image array pattern) of zigzag or inverse zigzag is applied as described above, and the pixels for which both the image data and the mask are in the ON state Only printing is supposed to be done.

Below, referring to FIGS.
Alternatively, a state of printing with an inverted zigzag mask will be described. Figure 1
In FIG. 3, 1710 is an example of pixels representing a part of the already arranged image data stored in the buffer, 1720 is a staggered pattern mask showing pixels that are allowed to be printed in the first pass, and 1730 is a second pass. It is a reverse zigzag pattern mask showing pixels that allow printing. 1740, and 1750
Represents pixels 1710 printed by the masks 1720 and 1730 in the first pass and the second pass, respectively.

In FIG. 13, when the already arranged image data is accumulated in the buffer as pixels occupying 25% of the entire area as shown in 1710, this 1
Consider printing the pixels in the area 710. In general, the pixel 1710 is arranged in a state in which the print data varies as much as possible in order to keep the density uniform in a specified fixed area. The arrangement of the pixels of 1710 depends on what kind of area gradation was performed in the image processing before being transferred to the printer body.

The pixel 1710 is an example of an image array in which the pixel occupies 25% of the area. For such image data, 1720 and 173, respectively.
When printing is performed with a mask of 0, the data is distributed and recorded in the first and second passes in the state where the data is equally divided, as indicated by 1740 and 1750. Next, in FIG. 14, when the image data that has already been arranged is accumulated in the buffer as pixels that occupy 50% of the entire area as shown in 1810, regarding printing of the pixels in the area of 1810 Think 1820 and 183 in FIG.
For 0, 1840, and 1850, 172 in FIG.
0, 1730, 1740, and 1750 are the same as those of the first embodiment, so description thereof will be omitted.

When printing image data in which pixels occupy 50% of the entire area as shown by 1810 in FIG. 14, when the pixels shown by 1810 are arranged in the most scattered state, a staggered pattern is formed. It can be easily imagined that the mask 1820 or the reverse zigzag pattern mask 1830 has a completely aligned arrangement. In FIG. 14, if the pixel 1810 matches the mask of either 1820 or 1830, printing of all the pixels is completed as shown by 1840 in the first pass, and 1850 is obtained in the second pass. No recording is done as shown. That is, all the pixels 1810 are printed by the same nozzle.

As described above, conventionally, 18 in FIG.
In the example of the pixel shown in FIG. 10, the influence of the nozzle variation is directly reflected on the density unevenness, and the original purpose of the division printing by the multi-pass printing method of the conventional example cannot be achieved. Further, in FIG. 15, when the already arranged image data is accumulated in the buffer as pixels exceeding 50% of the entire area as shown in 1910, about printing the pixels of the area of 1910 Think 1920, 1930, 194 in FIG.
For 0 and 1950, 1720 and 173 of FIG.
Since it is the same as 0, 1740, and 1750, respectively, description thereof will be omitted. The pixel shown in 1910 occupies 63% of the entire area.

That is, FIG. 15 shows a printing state when the image data 1910 in a state where the duty is further increased as compared with FIGS. 13 and 14 is input.
Also, as shown in 1940 and 1950, 1
It can be seen that there is a considerable difference in the number of prints between the second pass and the second pass. As described above, the density unevenness that has been improved by the conventional multi-pass printing method with high duty image data near 100%, but in the low duty image data around 50% or less, the nozzles used eventually deviate. As a result, the uneven density appears again.

Further, as shown in FIG. 10 described above, the multi-head always prints either a staggered pattern or a reverse staggered pattern using all nozzles. Therefore, FIG.
In the print area of 0, the upper half 4 pixels first land the staggered pattern, then the reverse zigzag pattern, but the lower half 4 pixels first land in the reverse zigzag pattern. After landing, the zigzag pattern will land next.

Therefore, in the case of printing in a state where the nozzles used are offset and the duty is increased as shown in FIG. 15, many dots land on the first pass and then a small amount on the second pass. A print area where dots land and a print area where a large number of dots land during the second pass, which do not land in the first pass, appear alternately by a half width of the multi-head.

Due to the above-mentioned phenomenon, there is an adverse effect as described below, particularly in the joint portion of the ink jet recording system. In the inkjet recording method, when another dot is superposed on a previously recorded dot, the dot that is printed later than the previously recorded dot tends to sink in the depth direction of the recording paper in the overlapping portion. It is in. Figure 1
6 is a schematic cross-sectional view of the recording paper surface. The first ink droplet is ejected in (a) of FIG. 16 and the first ink droplet is dyed in (b) of FIG. Then, the second ink droplet is ejected in (c) of FIG. 16 and (d) of FIG.
Then, the second ink droplet is dyed deeper than the dyeing of the first ink droplet.

In FIG. 16, pigments such as dyes in the ejected ink are physically and chemically bound to the recording medium, but the binding between the recording medium and the pigments is finite at this time. Therefore, as long as there is no great difference in the binding force depending on the type of pigment, the first ejected ink pigment ejected first remains on the surface of the recording medium in large amounts because the binding to the recording medium is prioritized.
It is considered that the second ink dye ejected later is difficult to bond on the surface of the recording medium, and therefore sinks in the depth direction of the paper and is dyed.

Further, considering the behavior of the ink at the fiber level inside the recording medium, the fiber once bound to the dye or the like in the ink is stronger in hydrophilicity than in the state where it is not bonded at all. Therefore, the ink droplet that has landed adjacent to the highly hydrophilic portion tends to be drawn in the direction in which the previous ink droplet has landed. Further, as the previous ink droplets are not sufficiently fixed, that is, as the water droplets are contained in a large amount, the hydrophilicity is strong, and the ink droplets that have landed adjacently are easily attracted.

Therefore, as shown in FIG. 15, a printing area in which a large number of dots are landed in the first pass and a small number of dots are landed in the second pass, and almost no printing is made in the first pass and the second pass When the print areas where a large amount of dots land on the print head alternately appear at intervals of half the width of the multi-head, a large amount of ink is landed later on the area adjacent to the print area where a large amount of ink has landed. The pulling force works strongly on the dots. On the contrary, the pulling force works weakly on the dots that are landed later on the area adjacent to the printing area where a small amount of ink has landed.

Therefore, at the boundary between the print areas, there are dark areas and light areas, resulting in uneven density. Such density unevenness is particularly conspicuous in the halftone, and has a periodicity that appears alternately by a half width of the multi-head. Further, when thinning printing is performed using a specific mask pattern, the print data and the mask pattern may have the same cycle. In this case, the amplitude of the density due to the arrangement of the print pixel and the non-print pixel by the mask pattern and the amplitude of the print data overlap and resonate, and the dot array of the formed image has a certain directional pattern. Will end up. Generally, this phenomenon is called moire. This is conspicuous when the image using the same mask pattern is present in a plurality of lines, and is easily recognized by the user. This moire largely depends on the periodicity of the mask pattern.

Due to the problems described above, printing by the conventional multi-pass printing method, which was carried out to correct the nozzle variations and the like, still resulted in insufficient image quality in terms of density unevenness. Since the adverse effects of these density unevenness have the periodicity that alternately appears in the print area of a certain width, it is easy for human eyes to sufficiently recognize the density unevenness. Therefore, eliminating the periodicity of the density unevenness is one means for preventing the operator from recognizing such an adverse effect as deterioration of image quality.

Further, in other image recording systems, for example, in an image recording apparatus of a type using a plurality of recording elements,
After all, there is a similar problem. For example, even in the thermal transfer method or the like, the same problem may occur due to unevenness of heat dissipation or unevenness of the heating element itself.

[0036]

The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, pattern reference means for referencing a plurality of random mask patterns,
A plurality of random mask patterns referred to by the pattern reference means are different patterns. The printing means prints according to a plurality of random mask patterns referred to by the reference means for each scan.For example, the random mask pattern stored by the pattern storage means has a dot arrangement of each color in a color reproduction mask. The feature is that they are arranged three-dimensionally at random.

Further, it has a pattern generating means for generating a random mask pattern, a pattern referring means for referring to a plurality of random mask patterns, and a printing means for scanning a certain printing region by a plurality of scans, and the pattern generating means generates the pattern. In the random mask pattern, non-print pixels and print pixels are randomly arranged, and the printing unit prints according to the plurality of random mask patterns generated by the pattern generation unit for each of a plurality of ink types.

For example, the printing means is characterized by ejecting ink to record an image, and the printing means is characterized by ejecting ink using thermal energy to record an image.

[0039]

With the above arrangement, in the multi-pass printing method in which printing is performed in the printing area by a plurality of printing scans, the non-printing pixels and the printing pixels are randomly arranged for each printing area and each ink type. By performing printing using different random mask patterns, the thinning array does not have a pattern period, and even in the image to be formed, the periodicity of density unevenness that has conventionally occurred is eliminated, and high-quality printing is achieved. Image formation becomes possible.

Further, for multi-value recording of the multi-drop method, by randomizing the three-dimensional color reproduction mask,
There is a unique effect that it is possible to further improve multi-value gradation reproducibility by making the formed image density macroscopically uniform and applying a multi-pass printing method.

[0041]

Embodiments of the image recording method and apparatus of the present invention will be described below in detail with reference to the drawings. <First Embodiment> FIG. 1 is a block diagram of an image recording apparatus of the present embodiment. In FIG. 1, reference numeral 10 denotes the main body of the image recording apparatus (printer) of this embodiment, and the image data sent from the host computer 1 together with the command is stored in the reception buffer 3 of the image recording apparatus 10 via the interface 2. The reception buffer 3 has a capacity of several k to several tens of kbytes. Next, in the command analysis unit 4, the reception buffer 3
Command analysis is performed on the command sent with the image data stored in the image data, and the image data is sent to the text buffer 5. In the text buffer 5, the image data is held as an intermediate format for one line, and the processing of adding the printing position of each character, the type of modification, the size, the character (code), the address of the font, etc. is performed according to the command analysis result. . The capacity of the text buffer 5 differs depending on each model, and has a capacity of several lines in the case of a serial printer and a capacity of one page in the case of a page printer.
Further, the image data stored in the text buffer 5 is expanded by the expansion unit 6 and stored in the print buffer 7 in a binarized state. Then, the developed binary image data is sent to the recording head 8 and printed.

In this embodiment, the binarized image data stored in the print buffer 7 is thinned by a random mask pattern and then sent to the recording head 8. Therefore, it is possible to set a random mask pattern depending on the state of the print data stored in the print buffer 7. Depending on the type of image recording device, the text buffer 5 may not be provided and the recording data accumulated in the reception buffer 3 may be expanded in the expansion unit 6 immediately after the command analysis by the command analysis unit 4 and written in the print buffer 7. There is also.

The image recording apparatus of this embodiment described above will be described in detail below. In this embodiment, 4-pass multi-pass printing is performed, a random mask pattern is set for each print area, and a different random mask pattern for each pass and each color is used for printout. In Figure 2,
An example of a memory configuration for generating a random mask pattern used in this embodiment is shown.

In this embodiment, as shown in FIG. 2, a random mask pattern is generated using a memory of 32 Kbytes (raster direction: 4 bytes × column direction: 8 Kbytes). Since the random mask pattern requires four passes in the example, the memory shown in FIG. 2 is divided into areas A, B, C, and D, respectively, but the four areas are continuous. And 8 of 1-8 for each area
The mask indicated by one start pointer is stored.

The memory area shown in FIG. 2 is recorded in the RAM of the apparatus of this embodiment, the position (start pointer) to be read can be freely set, and the start pointer can be shifted for each print area. Can refer to the memory. The random mask pattern stored in the memory area shown in FIG. 2 is preliminarily created using random numbers.

An example of using the random mask pattern in this embodiment will be described below with reference to FIGS. 3 and 4. FIG. 3 shows an example of the print head for each print area and its scan, and FIG. 4 shows an example of the random mask pattern used in each scan. In FIG. 3, in the first print scan, the first
Printing is performed on the print area through the mask A-1, and the first print area is masked by the mask A-1,
Printing through A-2, A-3, and A-4 is repeated,
Printing is completed. The mask A-1 is indicated by A in FIG.
Represents the mask referenced by the start pointer at the position of 1, and the masks B-1, C-1, D-1.
Are masks in which the position of the start pointer is referred to by 1 in each area.

In FIG. 3, the mask A-2 is referred to for the first print area in the second print scan. The mask A-2 is referred to by shifting the start pointer, which was the position 1 at the time of the first printing scan, to the position 2 in the area A of FIG. Similarly, the masks B-2, C-2, and D-2 are also referred to by shifting the position of the start pointer with respect to the mask referred to in the immediately preceding print scan.

The amount by which the start pointer is shifted can be set arbitrarily, but in the present embodiment, it is constructed such that it shifts by 256 columns in one area.
Therefore, the start pointer comes to the same position in the ninth scanning scan. Therefore, in the adjacent print areas, it looks as if different random mask patterns are used.

As described above, by shifting the start pointer with respect to the random mask pattern stored in the RAM, it is possible to refer to a plurality of different random mask patterns from one memory area, and there is little density unevenness. Printing with the multi-pass printing method is possible. As described above, according to the present embodiment, in the printing by the multi-pass printing method, a configuration in which a different random mask pattern is referred to for each printing scan is realized, and the synchronization between the print data and the random mask pattern is suppressed as much as possible. It becomes possible. Therefore, it is possible to reduce unevenness in the density of the output image due to nozzle variations and the like.

<Second Embodiment> The above description has been made in consideration of the case of monochrome printing, but the present invention is not limited to the above example and can be applied to the case of color printing. Next, a case where the present invention is applied to color printing will be described. In the second embodiment, in addition to the method of making the random mask pattern different for each printing scan of the first embodiment described above, the random mask pattern is made different between the respective colors so that pseudo printing is possible in the overlapping printing between the respective colors. Consideration is given so that the random mask pattern is not synchronized with the image data, which is a random number defect.

A method of forming a random mask pattern at the time of color printing in the second embodiment will be described with reference to FIG. FIG. 5 is a block diagram showing how a random mask pattern is created during color printing in the second embodiment. In the second embodiment, the case of 4-pass multi-pass printing as described above will be described.

In FIG. 5, first, an image area of a specific size is set, and the same number of four parameters (a,
b, c, d). Then, two parameters are randomly selected from the parameters, and they are exchanged with each other. By performing this process a plurality of times, a mask pattern in which each parameter is randomly arranged is created. The number of times of replacement is arbitrary as long as the mask has randomness, but in the second embodiment, it is 25000 × 15.
I've been there.

The state of the parameters of the random array created as described above is stored in the ROM. Then, each thinning mask is created. For example, four parameters a, b, c, d are four masks A,
Corresponding to B, C, and D, a bit is set only at a certain position of each parameter and each mask pattern is created.

Since the positions of the respective parameters are randomly arranged, the created mask also has a random mask pattern having a random arrangement. Furthermore, the created random mask pattern is initially one image area, and is created from there, so the original image is always 100
% It becomes a random mask pattern that can be interpolated. The random mask pattern creation process described above is performed by the CPU, and the created random mask pattern is stored in the RAM for use. FIG. 6 shows C at the time of creating a random mask pattern.
The relationship between PU, ROM, and RAM is shown.

For example, when a random mask pattern is created in the printer main body, data of a random array is stored in advance in a ROM or the like, and the above random mask pattern is created at the timing of turning on the power, etc. The completed mask pattern is stored in the RAM or the like. Then, when actually referring to the random mask pattern, the random mask pattern is read from the RAM at the time of the ramp-up of the carriage for each print scan, and is ANDed with the print data stored in the print buffer to perform printing. To do.

Therefore, it is possible to change the random mask pattern in accordance with the print mode at the timing of creating the random mask pattern. For example, it is possible to create a random mask pattern for 2-pass printing, 4-pass printing, 8-pass printing from the same random mask pattern. This is determined by the number of parameters used when creating the random mask pattern. If there are 24 types (for example, parameters 0 to 23) of parameters, make them correspond to divisors of the divisor. Can
That is, it is possible to support 2, 3, 4, 6, 8, 12, and 24 paths. Further, instead of associating one parameter with one mask pattern, by associating a plurality of parameters with one mask pattern, 100%
The above-described interpolation, that is, double printing can be performed at a specific ratio, and the ratio can be arbitrarily set by the number of parameters to be set.

Generally, in a binary printer, it is rare that the dots are shifted for each color in the color reproduction mask, that is, the color reproduction mask is small and the output image is composed of dot-on dots. In many cases, there is no problem even if the same mask pattern is applied for each color. However, at least a part of the output image may be formed with dots on dots, and in such a case, the second embodiment is particularly effective.

The second embodiment is also effective in the case of outputting a grayscale image as well as between colors, as in the above case. Further, the present embodiment can be applied to an image recording apparatus of a multi-dot type having a substantially dot-on-dot configuration. In the case of color printing, when the recording heads are arranged side by side, the pointer position of the random mask to be used may be displaced by the distance itself where the positions of the recording heads are displaced, or a fixed value shift of at least 1 dot or more may be used. May be given between colors, or the amount of deviation itself may be randomized.

As described above, according to the second embodiment,
In the case of color printing as well, by referring to a different random mask pattern for each color, it is possible to reduce the density unevenness of the output image, similar to the effect of the first embodiment described above. <Third Embodiment> A third embodiment of the present invention will be described below.

In the third embodiment, multi-value recording by the multi-drop method to which the multi-pass recording method is applied will be described. Generally, in the multi-drop method, color reproduction of 256 gradations is performed by using a color reproduction mask of about 2 × 2 in overprinting with dot-on-dots of about four values, but density unevenness of an output image due to variations in print heads. In order to eliminate the problem, it is possible to apply the multi-pass printing method in which the printing nozzles are shifted for each pass even in the multi-drop method.

Generally, in a multi-drop type image recording apparatus to which a multi-pass recording method is applied, since multi-value recording is performed, it is possible to print on special paper typified by coated paper having good color reproducibility and less color mixture. Since it is configured in the center, the above-mentioned characteristic of the adjacent dots penetrating into the recording paper is not taken into consideration. However, even in the multi-drop method, it is naturally necessary to consider the color reproducibility, and in consideration of the uniformity of the color reproducibility in the multi-drop method, attention must be paid to a combination such as the order in which each color is printed. For example, even when reproducing the same green color, Y, Y, Y, C
The hue may be slightly different between the case of drawing in the order of C and the case of drawing in the order of C, Y, Y, and Y.

As described above, when dots are printed by superimposing them on previously printed dots, the ink of the dots printed afterwards sneak in under the ink of the dots printed earlier. This is due to the property of being lost. This property depends on the property of the recording medium, but in general, this property is often strong. Therefore, in the third embodiment, the order in which the colors are printed is randomized to make the output image densities macroscopically uniform. That is, in the three-dimensional color reproduction mask, which is a multi-valued expression space, the order of color imprinting is randomized and printing is executed.

Further, in the case of reciprocal printing using the recording heads arranged side by side, the order in which the colors are imprinted is opposite between the forward pass and the backward pass. Therefore, when it is desired to switch the order in which the colors are impressed, the scanning and the backward pass for printing are performed. By randomly changing the combination of scans to be printed in, it is possible to make the output image densities macroscopically uniform. The same applies to the case of the dark and light print recording method. When performing drawing by combining a plurality of types of dark ink and light ink, by changing the combination of a plurality of types of ink at random as in the above, the output image density Can be made macroscopically uniform.

As described above, according to the third embodiment,
Even in the multi-drop method, it is possible to make the color reproducibility of the output image macroscopically uniform. <Fourth Embodiment> In the fourth embodiment, a case will be described in which the multi-drop method of the third embodiment is combined with the multi-pass method with a thinning process further added.

In the following, in the fourth embodiment, in the case of overlapping printing of four-valued dots-on-dots, while performing thinning processing on a 2 × 2 color reproduction mask, printing is performed by a multi-pass method of four or more passes. explain. In the fourth embodiment, in the case of color printing as in the second embodiment described above,
Printing is executed with reference to the random mask pattern interpolated so that the total of a plurality of parameters when creating the random mask pattern becomes 100%.

Generally, in the multi-drop method, if four colors are superimposed without thinning processing, it is conceivable that printing is performed at a recording frequency relatively high with respect to the movement of the carriage by printing from four passes to one pass. However, in the fourth embodiment, when the number of passes is more than that, the thinning processing is further added and printing is performed. By increasing the number of passes and performing thinning processing to draw a predetermined number of dots, blurring between adjacent dots is improved, and gradation reproducibility of a portion where dots are overlapped is also significantly improved.

Generally, in multi-value printing by superimposing dots,
There was a problem that the gradation reproducibility saturates quickly.The cause of this is that if the dots are continuously ejected during multi-valued printing as described above, the ink of the previously ejected dots will not be fixed. In addition, since the subsequent dots are printed, the dye of the ink sinks in the depth direction of the recording paper and also spreads in the lateral direction, which reduces the linearity of the density gradation. To get up.

As described above, according to the fourth embodiment,
In the multi-drop multi-value recording shown in the third embodiment, the thinning process is performed by referring to the plurality of random mask patterns capable of 100% interpolation shown in the second embodiment, and the number of passes is determined. By increasing the number of prints, it is possible to output an image with excellent gradation reproducibility. As the thinning mask used in each of the embodiments, a random number pattern using random numbers has been mainly described, but the present invention can also be applied to a fixed pattern. However, if thinning or the like is performed using a fixed pattern, moire may occur as described above, so it is desirable to use a random number pattern created using random numbers as a thinning mask.

Further, although the ink jet printer has been mainly described in the above-mentioned first to fourth embodiments, the present invention is not limited to this, and for example, a laser beam printer, a thermal transfer printer, a bubble jet printer or the like. The same applies to other types of copying machines such as printers. The present invention is provided with a means (for example, an electrothermal converter or a laser beam) that generates thermal energy as energy used for ejecting ink, particularly in the inkjet recording system, and the state of the ink is determined by the thermal energy. Although the printing apparatus of the type that causes a change has been described, such a method can achieve high density and high definition of recording.

Regarding its typical structure and principle, see, for example, US Pat. Nos. 4,723,129 and 4740.
What is done using the basic principles disclosed in 796 is preferred. This method can be applied to both the so-called on-demand type and continuous type, but especially in the case of the on-demand type, liquid (ink)
By applying at least one drive signal to the electrothermal transducer arranged corresponding to the sheet or liquid path in which the liquid crystal is held, which corresponds to the recorded information and gives a rapid temperature rise exceeding the film boiling. Since the electrothermal converter is caused to generate heat energy to cause film boiling on the heat-acting surface of the recording head, as a result, bubbles in the liquid (ink) corresponding to the drive signal in a one-to-one relationship can be formed. It is valid. The liquid (ink) is ejected through the ejection openings by the growth and contraction of the bubbles to form at least one droplet. It is more preferable to make this drive signal in a pulse shape, because bubbles can be grown and contracted immediately and appropriately, and thus a liquid (ink) with excellent responsiveness can be achieved.

As the pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. If the conditions described in US Pat. No. 4,313,124 of the invention relating to the rate of temperature rise on the heat acting surface are adopted, more excellent recording can be performed. As the structure of the recording head, in addition to the combination structure (straight liquid flow path or right-angled liquid flow path) of the ejection port, the liquid path, and the electrothermal converter as disclosed in the above-mentioned specifications, a heat acting surface is also provided. A configuration using US Pat. No. 4,558,333 and U.S. Pat. No. 4,459,600, which disclose a configuration in which is arranged in a bending region, is also included in the present invention. In addition, Japanese Unexamined Patent Application Publication No. Sho 5-5 discloses a configuration in which a common slot for a plurality of electrothermal converters is used as a discharge portion of the electrothermal converters.
Japanese Patent Application Laid-Open No. 9-123670 and Japanese Patent Application Laid-Open No. Sho 5 (1993) -58
The configuration may be based on Japanese Patent Publication No. 9-138461.

Further, as a full line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length can be increased by combining a plurality of recording heads as disclosed in the above-mentioned specification. Either of the structure satisfying the requirement or the structure as one recording head integrally formed may be used. In addition, the ink is integrated into the replaceable chip-type recording head, or the recording head itself, which can be electrically connected to the apparatus main body and can supply ink from the apparatus main body by being attached to the apparatus main body. A cartridge-type recording head provided with a tank may be used.

Further, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc., which are provided as a configuration of the recording apparatus of the present invention, because the effect of the present invention can be further stabilized. . Specific examples thereof include capping means, cleaning means, pressurizing or suctioning means for the recording head, preheating means using an electrothermal converter or another heating element or a combination thereof, and recording. It is also effective to perform a stable recording by performing a preliminary discharge mode in which another discharge is performed.

Further, the recording mode of the recording apparatus is not limited to the recording mode of only the mainstream color such as black, but the recording head may be integrally formed or a plurality of combinations may be used. Alternatively, the device may be provided with at least one of full-color mixed colors. In the embodiments of the present invention described above, the ink is described as a liquid, but an ink that solidifies at room temperature or lower, or one that softens or liquefies at room temperature may be used, or an ink jet system may be used. Generally, the temperature of the ink itself is adjusted within the range of 30 ° C to 70 ° C to control the temperature of the ink so that the viscosity of the ink is within the stable ejection range. Anything can be used.

In addition, in order to positively prevent the temperature rise due to thermal energy from being used as energy for changing the state of the ink from the solid state to the liquid state,
Alternatively, in order to prevent the ink from evaporating, an ink that solidifies in a standing state and liquefies by heating may be used. In any case, by applying heat energy, such as ink that is liquefied by applying heat energy according to the recording signal and liquid ink is ejected, or that begins to solidify when it reaches the recording medium. The present invention can be applied to the case where an ink having a property of being liquefied for the first time is used. In such a case, the ink is retained as a liquid or solid in the recesses or through holes of the porous sheet as described in JP-A-54-56847 or JP-A-60-71260. It may be configured to face the electrothermal converter. In the present invention, the most effective one for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as a form of the recording apparatus according to the present invention, in addition to one provided integrally or separately as an image output terminal of information processing equipment such as a computer, a copying apparatus combined with a reader or the like, and further transmission / reception It may take the form of a facsimile machine having a function. The present invention may be applied to a system including a plurality of devices or an apparatus including one device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0077]

As described above, according to the present invention, in the multi-pass printing method in which printing is performed on a printing area by a plurality of printing scans,
By performing printing using different random mask patterns in which the non-printing pixels and the printing pixels are randomly arranged, without giving the thinning array a pattern period,
Also in the formed image, it is possible to eliminate the periodicity of density unevenness that has occurred conventionally and form a high-quality image.

Further, for multi-valued multi-valued printing, the image density to be formed is made macroscopically uniform by randomizing the order in which the colors of the three-dimensional color reproduction mask are printed, and the multi-pass printing method is also adopted. By applying it, it is possible to further improve multi-value gradation reproducibility, which is a unique effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a flow of image data in a first embodiment according to the present invention.

FIG. 2 is a diagram showing an example of a random mask pattern in the present embodiment.

FIG. 3 is a diagram showing an example of a recording head and its scanning for each print area in the present embodiment.

FIG. 4 is a diagram showing an example of a random mask pattern in the present embodiment.

FIG. 5 is a diagram showing how a random mask pattern is created in the case of color printing according to the second embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a CPU, a ROM, and a RAM when creating a random mask pattern in the second embodiment according to the present invention.

FIG. 7 is a diagram showing an ideal printing state in a conventional inkjet printer.

FIG. 8 is a diagram illustrating a printing state in which density unevenness occurs in a conventional inkjet printer.

FIG. 9 is a diagram illustrating a printing state of multi-pass printing in the conventional inkjet printer.

FIG. 10 is a diagram illustrating a printing process of multi-pass printing in the conventional inkjet printer.

FIG. 11 is a configuration diagram for generating a staggered pattern and an inverted zigzag pattern of a conventional example.

FIG. 12 is a timing chart when generating a staggered pattern and an inverse zigzag pattern of a conventional example.

FIG. 13 is a diagram illustrating 25% data and print dots in conventional multi-pass printing.

FIG. 14 is a diagram illustrating 50% data and print dots in conventional multi-pass printing.

FIG. 15 is a diagram illustrating 63% data and print dots in conventional multi-pass printing.

FIG. 16: 2 in the conventional inkjet printer
It is a figure showing the cross section of a recording paper in the case of one dot impact.

[Explanation of symbols]

1 Host computer 2 interfaces 3 Receive buffer 4 Command analysis part 5 text buffer 6 Development Department 7 print buffer 8 recording head

─────────────────────────────────────────────────── ─── Continued front page (72) Toshiharu Inui, 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Isao Ebisawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Atsushi Arai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Nao Yaegashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Nobuyuki Kuwahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kei Iwasaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Kanematsu Daigoro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP-A-5-169681 (JP, A) JP-A-5-31922 (J P, A) JP 5-155040 (JP, A) JP 5-167838 (JP, A) JP 5-278232 (JP, A) JP 7-52389 (JP, A) JP Flat 7-52390 (JP, A) JP 7-52391 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/01 B41J 2/21 B41J 2/485 B41J 2 / 52 B41J 2/525

Claims (8)

(57) [Claims] 1. A pattern reference step of referring to a plurality of random mask patterns, and a printing step of printing one dot or more for one print point by a plurality of scans in a predetermined print area, the pattern reference The plurality of random mask patterns referred to by the steps are different patterns, and the printing step prints according to the plurality of random mask patterns referred to by the reference step for each scan. 2. A pattern generation step of generating a random mask pattern, a pattern reference step of referring to a plurality of the random mask patterns, and a printing step of printing a predetermined print area by a plurality of scans. The non-printed pixels and the printed pixels are randomly arranged in the random mask pattern generated by the process, and the printing process prints according to the plurality of random mask patterns generated by the pattern generation process for each of a plurality of ink types. An image recording method characterized by: 3. The image recording method according to claim 2, wherein in the pattern generating step, a random mask pattern is generated by reading from a pattern stored in a memory. 4. The image recording method according to claim 3, wherein in the pattern generation step, a read position of the memory is made variable. 5. A pattern reference unit for referring to a plurality of random mask patterns, and a printing unit for printing one dot or more for one printing point by a plurality of scans in a certain printing region, the pattern reference unit. The image recording device is characterized in that the plurality of random mask patterns referred to by are different patterns, and the printing unit prints according to the plurality of random mask patterns referred to by the reference unit for each scan. 6. A pattern generating means for generating a random mask pattern includes a pattern reference unit for multiple reference to a random mask pattern, and a printing means for printing a certain printing area by a plurality of scanning by said pattern generating means In the generated random mask pattern, non-printing pixels and printing pixels are randomly arranged, and the printing unit prints according to the plurality of random mask patterns generated by the pattern generating unit for each of a plurality of ink types. An image recording device characterized by. 7. The image recording apparatus according to claim 5, wherein the printing unit ejects ink to record an image. 8. The printing means records an image by ejecting ink using thermal energy.
7. The image recording device described in 7 .