JP2007261217A - Printer, device of optimizing pattern table and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve disorder of a tone which appears at a boundary part of head chips. <P>SOLUTION: A holding part and a switching part are mounted in the printer of an inkjet system in which a plurality of the head chips are mounted in an offset arrangement in a printing direction. (a) The holding part holds by an amount of several lines information on a pattern table selected about dots at a boundary position appearing first of each processing line in the head chip which forms dots precedently in time. (b) The switching part applies a pattern table sequentially selected in units of one dots or of a plurality of dots for the dots excluding the boundary part, applies a pattern table selected about the dots of the boundary position appearing first of the present processing unit for all of the dots of the boundary part formed precedently in time, and applies a pattern table selected only several lines before for the dots of the boundary part formed late in time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The invention proposed in the specification relates to an ink jet printing apparatus capable of forming one dot with a plurality of ink droplets.
The invention proposed by the inventor has aspects as a printing apparatus, a pattern table optimization apparatus, and a computer program.

Recent printing apparatuses are required to have high print quality simultaneously with high-speed printing. Along with this, a printing technique for forming one dot with a plurality of ink droplets has been proposed. In the case of this printing technique, a printed image can be expressed with a resolution higher than the dot density.
FIG. 1 shows an example of an ink jet printing apparatus that employs this type of printing technology. The printing apparatus 1 includes a multilevel error diffusion unit 3, a head controller 5, and a print head 7.

  The multi-level error diffusion unit 3 is a processing device that performs multi-level error diffusion processing on CMYK signals corresponding to ink colors (cyan, magenta, yellow, black) for each color. The multi-level error diffusion unit 3 converts the CMYK signal of 256 gradations into a 9-level quantization level and outputs it to the head controller 5 as multi-level quantization value data (4 bits).

At this time, the multi-level error diffusion unit 3 executes rearrangement processing of the multi-level quantized data output to the head controller 5 according to the arrangement of the head chips constituting the print head 7.
The multi-level quantized data is data that gives the number of ink droplets from 0 to 8 used for forming one dot.

The head controller 5 is a processing device that converts multilevel quantized data into dot pattern data that defines ejection timing. The head controller 5 includes a dot pattern converter 51, a random number generator 53, an output buffer 55, a write counter 57, and a read counter 59.
The dot pattern conversion unit 51 is a processing device that converts multi-level quantized data into a dot pattern using a pattern table selected by the random number generator 53 among the eight pattern tables. FIG. 2 shows an example of a pattern table.

Here, in each pattern table, nine levels of quantization levels that can be taken by the multilevel quantization data and dot patterns are stored in association with each other. Note that the eight pattern tables prepared in advance are different from each other in the correspondence between the quantization level and the dot pattern.
By using a pattern table randomly selected from the eight pattern tables, image quality degradation due to dot pattern regularity is reduced.

The random number generator 53 generates a random number for each dot or several dots according to the address generated by the write counter 57.
The output buffer 55 is a buffer memory having two storage areas for writing and reading. One of the two storage areas is used for writing a dot pattern, and the other is used for reading a dot pattern. The write counter 57 and the read counter 59 give this read / write address.

The print head 7 is a device that ejects ink droplets from corresponding nozzles according to a dot pattern read from the output buffer 55.
FIG. 3 shows a configuration example of the print head 7. FIG. 3 shows an example in which the print head 7 is a line head. The print head 7 is composed of 16 head chips 71 arranged one by one in a walking manner.

The step (offset amount) in the sheet feeding direction between the adjacent head chips 71 is assumed to be 4 lines (4 dots).
FIG. 3A shows a head structure corresponding to a certain color. Accordingly, the print head 7 using four color inks is equipped with four head structures shown in FIG.
Each head chip 71 has 320 nozzles formed in a line. The black circles in the figure correspond to individual nozzles.

Further, the head chip 71 employs a discharge mechanism corresponding to the ink droplet deflection discharge technology. In this example, it is assumed that ink droplets can be divided into four dot positions.
FIG. 4 shows an example of ink droplet sorting by deflection ejection. In the case of the ejection mechanism shown in FIG. 4A, the ejection direction (landing position) of the ink droplet 77 can be varied by controlling the balance of the amount of current flowing through the two left and right heaters 75 disposed at the bottom of the nozzle 73. Can do.

In this example, each nozzle 73 can land the ink droplet 77 at the four dot positions shown in FIG.
Using this deflection ejection technique, for four dots positioned at the boundary between two head chips 71, two adjacent head chips 71 form one dot pattern after a time difference of four lines.
JP 2005-81621 A

However, in the case of the above-described printing apparatus, there is a problem that the image quality (gradation) as shown in FIG.
Hereinafter, the cause of the appearance of image quality (gradation) disturbance will be described from the viewpoint of processing operation.
The multi-level error diffusion unit 3 described above outputs multi-level quantized data values having the same positional relationship as the head chip arrangement as serial data.
6 and 7 show examples of serial data output. Incidentally, the serial data is to be output in the order of arrangement in the right direction from the dot positions on the left side in FIG.

However, as shown in FIG. 7, the serial data is multiplexed with multi-value quantization data for 4 dots located at the boundary between the head chips in addition to multi-value quantization data for 320 dots corresponding to each head chip. Inserted.
The data for four dots inserted after the data corresponding to the head chip 1 is the same as the data given to the first four dots of the head chip 2 that ejected ink droplets to the same dot four lines before.

  FIG. 8 shows a dot pattern example given as serial data. FIG. 8A is an example of a dot pattern given to a head chip (lagging head) that forms dots later than the other head chip. FIG. 8B is an example of a dot pattern given to a head chip (preceding head) that forms dots earlier than the other head chip.

The dot pattern in FIG. 8 is an example in which each dot can eject a maximum of eight ink droplets within a printing cycle with a time difference, and the ink droplet ejection control is performed in a time slot with a black circle. .
By the way, at the boundary portion, the ejection of ink droplets is allocated to the two head chips because of the time slot.
In the figure, the half-dotted portions are data positions that can be formed by the head chip 1 using the deflection discharge technique. The white portion is a data position that can be formed by the head chip 2 using the deflection ejection technique.

  However, the notation of FIG. 8 is an example in which the four dot positions that can be landed by one nozzle are indicated by the positional relationship shown in FIG. That is, with the nozzle as the reference position, four dots arranged in the right direction from the left end in FIG. 4B are represented as “No. 1 position”, “No. 2 position”, “No. 3 position”, and “No. 4 position”. Corresponds to the positional relationship. For reference, FIG. 10 illustrates the correspondence between each nozzle and the dot position. In FIG. 10, the dot position where the “1” nozzle can land the ink droplet is “1”, the dot position where the “2” nozzle can land the ink droplet is “2”, and the “3” nozzle is the ink A dot position where a droplet can be landed is indicated by “3”, and a dot position where a nozzle “4” can land an ink droplet is indicated by “4”. This positional relationship is consistent with the notation of FIG.

  Returning to the description of FIG. In the case of this example, the dot corresponding to the left end of the head chip 2 can be formed with ink droplets of the head chip 1 out of a maximum of eight. In addition, the dot corresponding to the second from the left end of the head chip 1 can form four out of a maximum of eight with the ink droplets of the head chip 1. In addition, the dot corresponding to the third from the left end of the head chip 1 can be formed with ink droplets of the head chip 1 out of a maximum of eight.

At this time, if the time difference between the head chips is ignored, the same value of multi-value quantized data is given to the same dot position. That is, in the case of FIG. 8, the same multi-value quantized data value as that when the head chip 2 (preceding head) forms dots four lines before is inserted into the subsequent stage of the head chip 1. That is, “2”, “2”, “4”, and “3” are given to the dots in the boundary portion in order from the left side in the figure.
Of course, if both the head chip 1 and the head chip 2 are operating according to the same dot pattern, the number of ink droplets that land on one dot should be the same as the multi-value quantization data value.

However, in the case of the printing apparatus described above, the selection of the pattern table referred to by the dot pattern conversion unit 51 depends on the random number generated at the time of printing. For this reason, even when converting the multivalued quantized data value of the same value into a dot pattern, a situation occurs in which the head chips 1 and 2 refer to different pattern tables.
For example, in the case of FIGS. 8A and 8B, different dot patterns are referenced in the “2” and “4” portions of the multilevel quantized data value.

As a result, as shown in FIG. 8C, a phenomenon in which the number of ink droplets is one more than the multi-value quantized data value occurs in the leftmost dot of the boundary portion, and the second dot from the left end of the boundary portion. Then, a phenomenon occurs in which the number of ink droplets is one less than the multi-value quantization data value.
In the third dot from the left end of the boundary portion, the number of ink droplets used for the formation coincides with the multi-value quantization data value. However, this is a coincidence and there is no guarantee that they will always coincide.
As described above, in the conventional printing apparatus, there is a possibility that a gradation disturbance appears at the boundary portion of the head chip.

Therefore, the inventor proposes a mechanism for holding the selection information of the pattern table at the boundary portion used by the preceding head at least until the use of the slow head.
Note that an inkjet printing apparatus includes a set of pattern tables in which a dot pattern that defines the relationship between nozzles that discharge ink droplets and discharge timing and multi-value quantization values are associated with each other, and the set of pattern tables. A case is assumed in which a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern with reference to a randomly selected pattern table is mounted.

A plurality of head chips constituting one line head or one print head are offset by several lines in the paper feed direction between the head chips adjacent in the line direction or the relative movement direction of the print head and the paper. It is assumed that it is arranged.
In addition, the dot corresponding to the boundary position between two adjacent head chips is formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines.

(Mechanism 1)
As one mechanism, the inventor proposes a printing apparatus equipped with the following processing device.
(A) A boundary selection information holding unit that holds several lines of pattern table information selected for a dot at a boundary position that appears first in each processing line among head chips that form dots ahead of time ( b) A pattern table that is sequentially selected in units of one or a plurality of dots is applied to the dots excluding the boundary portion, and for all the dots in the boundary portion formed in advance in time, The pattern table selected for the dot at the boundary position that appears at the beginning of the current processing unit is applied, and the pattern table selected a few lines earlier for the dot at the boundary portion formed by delaying in time Selection information switching unit to apply

(Mechanism 2)
As one mechanism, the inventor proposes a printing apparatus equipped with the following processing device.
(A) Selection information for boundary that holds information of a pattern table selected for a dot at a boundary position that appears first in all processing lines among head chips that form dots ahead of time until the end of all processing lines (B) A pattern table that is sequentially selected in units of one or a plurality of dots is applied to dots excluding the boundary portion, and a boundary selection information holding unit is applied to dots located in the boundary portion Selection information switching unit that applies a pattern table of information held in

(Mechanism 3)
As one mechanism, the inventor proposes a printing apparatus equipped with the following processing device.
(A) Boundary selection information holding for holding a pattern table selected for each processing line boundary position that appears first in all processing lines among head chips that form dots ahead of time until the end of all processing lines Part (b) A pattern table that is sequentially selected in units of one or a plurality of dots is applied to dots other than the boundary part, and a dot located in the boundary part is applied to the boundary selection information holding part. Selection information switching unit that applies a pattern table of information held for each boundary position

  By adopting the mechanism proposed by the inventor, it is possible to eliminate the gradation disturbance at the joint portion of the head chip.

Hereinafter, exemplary embodiments of an ink jet printing apparatus according to the invention will be described.
In addition, the well-known or well-known technique of the said technical field is applied to the part which is not specifically illustrated or described in this specification.
The embodiment described below is one embodiment of the present invention and is not limited thereto.

(A) Basic principle In order to avoid gradation disturbance at the boundary caused by dot pattern mismatch, there is a mechanism for holding at least the offset of the pattern table selection history (ie, random number history), and at the time of printing the boundary portion. A mechanism that uses the same pattern table as the preceding head with reference to the selection history is required.
FIG. 11 shows a boundary range necessary for saving the selection history.

FIG. 11 shows the case where the ink colors are four colors Y, C, M, and K, and there are 16 head chips per color (N = 16).
In this case, when the number of pattern tables is eight and the offset between head chips is given by 4 dots, the storage capacity M necessary for storing the selection history is given by the following equation.
M = (number of colors) × (number of chip boundaries) × (number of table selection bits) × (number of dots between chips)
Therefore, in the case of the above-described conditions, the storage capacity M requires 720 (= 4 × 15 × 3 × 4) bits.

Of course, as the number of chip boundaries and the number of dots between chips increase, a larger amount of storage capacity is required.
Therefore, the inventor proposes a mechanism that enables the same effect with a smaller storage capacity.

(B) System example 1
FIG. 12 shows a functional configuration example of the printing system proposed by the inventor. In FIG. 12, the same reference numerals are given to the portions corresponding to FIG. 1.
The printing apparatus 100 includes a multi-value error diffusion unit 3, a head controller 501, and a print head 7. That is, the multi-value error diffusion unit 3 and the print head 7 are assumed to be the same as those in the conventional apparatus.

A head controller 501 having a characteristic configuration in this system example includes a random number memory 503 and a random number selector 505 in addition to a dot pattern conversion unit 51, a random number generator 53, an output buffer 55, a write counter 57, and a read counter 59. Constitute.
That is, a random number memory 503 and a random number selector 505 are newly added.

  The random number memory 503 is a head chip that forms dots by delaying in time a random number selected for a dot at a boundary position that appears first in each processing line among head chips that form dots in advance in time. In this embodiment, the storage area is held for the offset (4 lines) period of the head chip. The random number memory 503 corresponds to a “boundary selection information holding unit” in the claims.

FIG. 13 shows an example of a boundary position that appears first in each processing line (dot line corresponding to a nozzle group that ejects ink droplets at the same timing). As shown in FIG. 13, the number of boundaries that are the storage targets of the selection history is one regardless of the number of head chips.
Therefore, the storage capacity M1 of the random number memory 503 may be only 48 bits even under the same conditions as in the above example. The storage capacity M1 is calculated as (number of colors “4”) × (number of storage boundaries “1”) × (number of table selection bits “3”) × (number of dots between chips “4”).

The random number selector 505 is a processing device that supplies the dot pattern conversion unit 51 with either the random number given from the random number generator 53 or the random number before the offset given from the random number memory 503 according to the writing position. The random number selector 505 corresponds to a “selection information switching unit” in the claims.
The random number selector 505 selects the random number generated by the random number generator 53 for the dots excluding the boundary portion. The random number selector 505 selects random numbers stored in the random number memory 503 on the current processing line for all the boundary positions of the preceding head.

The random number selector 505 selects, from the random number memory 503, random numbers used in the previous processing line by four lines for all boundary positions of the lagging head.
By sequentially executing this random number selection operation for all dots on the print page, the printing operation of the printing apparatus 100 proceeds.
FIG. 14 shows an example of a processing procedure executed by the head controller 501.
First, the head controller 501 inputs a multilevel quantized data value from the multilevel error diffusion unit 3 (S1).

At this time, the random number generator 53 generates a random number (S2). The generated random number is supplied to the random number memory 503 and the random number selector 505.
The random number memory 503 determines whether or not the nozzle to be processed is the first boundary of each processing line according to the writing address given from the writing counter 57 (S3). If it is determined that the boundary is the first boundary, the random number memory 503 stores the given random number as a random number for the corresponding line (S4).

The random number selector 505 reads the random number stored at the head position of the same processing line from the random number memory 503 when the multi-value quantized data value that drives the nozzle of the preceding head is a processing target, and selects the nozzle of the slow head. When the multi-value quantized data value to be driven is a processing target, the random number stored in the previous processing line by four lines is read from the random number memory 503 and output (S5).
If a negative result is obtained in step S3, the random number selector 505 outputs the random number given from the random number selector 505 as it is.

The dot pattern conversion unit 51 selects a pattern table based on the random number given from the random number selector 505 (S6), and converts it into a dot pattern corresponding to the corresponding multilevel quantized data (S7). The dot pattern conversion unit 51 writes the converted dot pattern in the output buffer 55 (S8).
This dot pattern is output to the print head 7 based on the read address given from the read counter 59, and a print image is formed on the print paper (S9).

  By adopting this printing apparatus 100, it is possible in principle to eliminate the possibility of gradation disturbance occurring at the boundary portion of the head chip. In the case of this boundary processing technique, only the boundary portion of the head chip is different from a random number in the strict sense of selection of the pattern table. However, since the boundary processing and the random number are inherently independent, there is no influence on the print quality, and improvement in image quality has been confirmed.

Also, with this boundary processing technology, the storage capacity M1 required for realizing this function is very small, about 720 dots (in the case of four-color ink, the number of head chips 16, the number of table selection bits 3, and the offset 4 dots). .
Therefore, it is advantageous when reducing the price of the printing apparatus. In particular, when the number of head chips constituting the line head is large, it is advantageous because the number of head chips does not lead to an increase in the storage capacity M1.

(C) System example 2
Next, another example of the printing system proposed by the inventor will be described. Here, an improvement example of the system example 1 will be described.
At the time of manufacturing the print head 7, the head chip is precisely positioned, but it is actually necessary to consider the occurrence of mounting errors.

For example, as shown in FIG. 15A, when the offset between the head chips 1 and 2 is defined as 4 dots, the offset may increase or decrease as shown in FIG. 15B. For example, the offset may be 2 dots (-2 dots) or 7 dots (+3 dots).
In this case, if the random number reading operation is continued on the assumption that the mounting error is 0 (zero), it is assumed that the dot formation at the boundary portion is not performed correctly.

Accordingly, in this system example, a printing apparatus 200 having the configuration shown in FIG. 16 is proposed. In FIG. 16, the same reference numerals are given to the portions corresponding to FIG. 12.
The difference between the system example 2 and the system example 1 described above is that the offset correction value memory 79 is mounted on the print head 7 and the offset correction value is referred to when the random number selector 505 reads the random number for the lagging head. Thus, the read address is optimized.

By installing this mechanism, it is possible to execute optimum boundary processing even when a head chip mounting error occurs.
However, in this system example, it is necessary to expand the storage capacity M2 within the correction range in preparation for a case where the interval between chips is widened due to an attachment error. Even in such a case, since the assumed capacity is small, an increase in the storage capacity necessary for storing the random numbers can be minimized.

(D) System example 3
Next, another example of the printing system proposed by the inventor will be described.
Here, a mechanism capable of minimizing the random number storage capacity M3 will be described. Note that the basic system configuration is the same as that of the system example 1, and thus the description thereof is omitted. Functions unique to the system example 3 are a random number recording method for the random number memory 505 and a random number selection method by the random number selector 505.

In the case of this system example 3, the random number memory 503 uses the random numbers selected according to the boundary positions of the processing lines appearing at the beginning of all the processing lines among the head chips that form dots ahead of time in the end of all the processing lines. Function as a storage area.
FIG. 17 shows a boundary position that appears first in all processing lines. As shown in FIG. 17, one random number is stored in one page.

In this case, the storage capacity M3 of the random number memory 503 may be only 12 bits even under the same conditions as in the above example. The storage capacity M3 is calculated as (number of colors “4”) × (number of storage boundaries “1”) × (number of table selection bits “3”).
The random number selector 505 functions as a processing device that supplies the dot pattern conversion unit 51 with either the random number given from the random number generator 53 or the random number given from the random number memory 503 according to the writing position.

Here, the random number selector 505 selects the random number generated by the random number generator 53 for the dots excluding the boundary portion.
Further, the random number selector 505 selects only one random number stored in the random number memory 503 at the first boundary portion for one page for dots located at the boundary portion.
By sequentially executing this random number selection operation for all dots on the printed page, a printing operation that is simpler than that of the system example 1 proceeds.

FIG. 18 shows a processing procedure example executed by the head controller 501.
Also in this example, the head controller 501 inputs the multilevel quantized data value from the multilevel error diffusion unit 3 (S11).
At this time, the random number generator 53 generates a random number (S12). The generated random number is supplied to the random number memory 503 and the random number selector 505.

  The random number memory 503 determines whether or not the nozzle to be processed is a boundary according to the write address given from the write counter 57 (S13). When it is determined that it is a boundary (Yes in process S13), the random number memory 503 further determines whether or not the determined boundary is the first boundary of all process lines (S14). If a positive result is also obtained here, the random number memory 503 stores the random number generated by the random number generator 53 (S15).

After the random number is stored in the random number memory 503 or when a negative result is obtained in step S14, the random number selector 505 reads the random number stored in the random number memory 503 for dot conversion at the boundary portion (S16).
If a negative result is obtained in step S13, the random number selector 505 selects the random number given from the random number selector 505 and outputs it as it is.

The dot pattern conversion unit 51 selects a pattern table based on the random number given from the random number selector 505 (S17), and converts it into a dot pattern corresponding to the corresponding multilevel quantized data (S18). The dot pattern conversion unit 51 writes the converted dot pattern in the output buffer 55 (S19).
The dot pattern is output to the print head 7 based on the read address given from the read counter 59, and a print image is formed on the print paper (S20).

By adopting this printing apparatus, it is possible in principle to eliminate the possibility of gradation disturbance at the boundary between the head chips.
In addition, the storage capacity M1 required for realizing this function is about 12 dots (in the case of four-color ink, the number of head chips 16, the number of table selection bits 3, and the offset 4 dots). Further, since it is not necessary to consider the offset between the head chips, the processing itself is greatly simplified. As a result, it is advantageous for further cost reduction of the printing apparatus. Also, this boundary processing technique can be applied without considering the head chip mounting error.

(E) System example 4
Next, another example of the printing system proposed by the inventor will be described.
In this printing system example, a method of holding a set of random numbers selected at each boundary portion appearing in the first line of all the processing lines and using it in all subsequent processing lines will be described.
Also in the case of this system example, the basic system configuration is the same as that of the system example 1, and the description thereof is omitted. Functions unique to the system example 4 are a random number recording method for the random number memory 505 and a random number selection method by the random number selector 505.

In the case of this system example 4, the random number memory 503 functions as a storage area that holds the random numbers selected for the boundary positions of the processing lines that appear first in all the processing lines until the end of all the processing lines.
FIG. 19 shows a boundary position that appears in the first processing line among all the processing lines. In this case, a random number of N-1 head chips is stored.

Therefore, the storage capacity M4 of the random number memory 503 is 180 bits even under the same conditions as in the above example. The storage capacity M4 is calculated as (number of colors “4”) × (number of storage boundaries “15”) × (number of table selection bits “3”).
The random number selector 505 functions as a processing device that supplies the dot pattern conversion unit 51 with either the random number given from the random number generator 53 or the random number given from the random number memory 503 according to the writing position.

Here, the random number selector 505 selects the random number generated by the random number generator 53 for the dots excluding the boundary portion.
In addition, the random number selector 505 selects a random number at a corresponding position for each boundary position with respect to dots positioned at the boundary portion.
By sequentially executing this random number selection operation for all dots on the printed page, a printing operation that is simpler than that of the system example 1 proceeds.

FIG. 20 shows a processing procedure example executed by the head controller 501.
Also in this example, the head controller 501 inputs the multilevel quantized data value from the multilevel error diffusion unit 3 (S21).
At this time, the random number generator 53 generates a random number (S22). The generated random number is supplied to the random number memory 503 and the random number selector 505.

  The random number memory 503 determines whether the nozzle to be processed is a boundary in accordance with the write address given from the write counter 57 (S23). When it is determined that it is a boundary (positive result in processing S23), the random number memory 503 further determines whether or not the determined boundary is the first processing line of all processing lines (S24). If a positive result is also obtained here, the random number memory 503 stores the random number generated by the random number generator 53 for each boundary position (S25).

After storing the random number in the random number memory 503 or when a negative result is obtained in the process S24, the random number selector 505 reads the corresponding random number for each boundary position (S26).
If a negative result is obtained in step S23, the random number selector 505 selects the random number given from the random number selector 505 and outputs it as it is.

The dot pattern conversion unit 51 selects a pattern table based on the random number given from the random number selector 505 (S27), and converts it into a dot pattern corresponding to the corresponding multilevel quantized data (S28). The dot pattern conversion unit 51 writes the converted dot pattern in the output buffer 55 (S29).
The dot pattern is output to the print head 7 based on the read address given from the read counter 59, and a print image is formed on the print paper (S30).

By adopting this printing apparatus, it is possible in principle to eliminate the possibility of gradation disturbance at the boundary between the head chips.
In addition, the storage capacity M4 required for realizing this function is about 180 dots (in the case of four-color ink, the number of head chips 16, the number of table selection bits 3, and the offset 4 dots). Also in this case, since it is not necessary to consider the offset between the head chips, the processing itself is greatly simplified. As a result, it is advantageous for further cost reduction of the printing apparatus.

(C) Other Embodiments (a) In the above-described embodiment, the case where four-color ink, the number of head chips is 16, the number of table selection bits is 3, and the chip offset is 4 dots has been described.
However, it can be applied to any case where other numerical values are adopted. For example, the present invention can be applied to the case where the number of inks is six, the number of head chips is 20, the number of table selection bits is 5, and the chip offset chip is 10 dots. In any case, it is possible to effectively reduce the increase in storage capacity necessary for configuring the system under the same conditions.

(B) In the above-described embodiment, a case has been described in which one nozzle can distinguish four dot positions by adopting the deflection discharge technique.
Of course, this is an example, and the number of dot positions that can be sorted may be two, three, or five or more.

(C) In the above-described embodiment, the case where the print head is equipped with the ink droplet deflecting and discharging mechanism has been described.
However, the boundary processing technique described above can also be applied to a print head that does not include an ink droplet deflecting and discharging mechanism.

  In this case, as shown in FIG. 21A, the head chips 71 constituting the print head 700 are arranged so that the end portions thereof overlap with the end portions of the adjacent head chips 71, and the head chips 71 located at the overlapping portions are arranged. A printing method is adopted in which the nozzles share a single dot pattern. Also in this case, the same pattern table can be assigned to each nozzle of different head chips that share the boundary portion.

(D) In the above-described embodiment, a printing apparatus equipped with a line head has been described. However, the invention proposed by the inventor can be applied to a printing apparatus equipped with a print head other than the line head as long as the printing apparatus is equipped with a print head composed of a plurality of head chips. For example, the present invention can be applied to a printing apparatus equipped with a serial head.

  When applied to a printing apparatus equipped with a serial head, the random number memory 503 described above is selected for the dot at the boundary position that appears first in each processing line among the head chips that form dots ahead of time. A random number is used as a storage area for holding a dot until a dot is formed by a head chip that delays in time and forms a dot.

In this case, not only a method for ejecting ink droplets by the expansion force of bubbles grown by heating of the heater but also other methods can be used for the ink droplet ejection mechanism.
For example, a system using pressure due to deformation of a variable element arranged at the bottom of the nozzle or the ink flow path can be used.

(E) The above-described embodiment can be applied regardless of whether the printing apparatus is for business use or personal use. For example, the present invention can be applied to office printing machines, medical printing machines, photo printing machines, copying machines, fax machines, general-purpose printing machines, video printing machines, and the like.
Note that the printing apparatus may include devices other than the printing function, such as a display device and a scanner.
Further, the printing apparatus may be equipped with a mass storage device for storing image data. For the mass storage device, for example, a hard disk drive, a semiconductor memory, an optical storage medium, or the like is used.

(F) Of the above-described techniques, the function of matching the pattern tables of different head chips at the boundary part can be realized as hardware or software.
Further, not only all of these processing functions are realized by hardware or software, but some of them may be realized by using hardware or software. That is, a combination of hardware and software may be used.
(G) Various modifications can be considered for the above-described embodiments within the scope of the gist of the invention. Various modifications and application examples created based on the description of the present specification are also conceivable.

It is a figure which shows the prior art structural example of a printing apparatus. It is a figure which shows the example of a pattern table. It is a figure which shows the example of arrangement | positioning of the head chip which comprises a printing head. It is a figure explaining the deflection | deviation discharge technique of an ink droplet. It is a figure explaining the disturbance of the gradation which generate | occur | produces in the boundary of a head chip. It is a figure explaining the example of an output of serial data. It is a figure explaining the structural example of serial data. It is a figure explaining the principle which disturbance of a gradation generate | occur | produces in a boundary part. It is a figure which shows the relationship between the nozzle on description, and the landing position of an ink drop. It is a figure which shows the relationship between the nozzle on description, and the landing position of an ink drop. It is a figure explaining the example of the preservation | save range of the random number selection log | history required in order to avoid the disorder of the gradation of a boundary part. It is a figure which shows the example of a form of a printing apparatus. It is a figure explaining the preservation | save position of a random number selection log | history. It is a figure which shows the example of a process sequence of a head controller in the case of preserve | saving the random number only of the boundary located in the head of each process line. It is a figure explaining the case where a mounting error generate | occur | produces in a head chip. It is a figure which shows the example of a form of a printing apparatus. It is a figure explaining the preservation | save position of a random number selection log | history. It is a figure which shows the example of a process sequence of a head controller in the case of preserve | saving only the boundary random number located in the head of all the process lines. It is a figure explaining the preservation | save position of a random number selection log | history. It is a figure which shows the example of a process sequence of a head controller in the case of preserve | saving a random number according to the boundary position which appears in the process line located in the head among all the process lines. It is a figure explaining the other structural example of a print head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printing apparatus 3 Multi-value error diffusion part 5 Head controller 7 Print head 51 Dot pattern conversion part 53 Random number generator 71 Head chip 73 Nozzle 75 Heater 53 Random number generator 55 Random number selector 100 Printing apparatus 200 Printing apparatus 501 Head controller 503 Random number Memory 505 Random number selector 511 Head controller

Claims (13)

Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables In an inkjet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
A plurality of head chips constituting one line head are arranged by offsetting several lines in the paper feeding direction between the head chips adjacent in the line direction, corresponding to the boundary position between two adjacent head chips. When forming the dots to be formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines,
A boundary selection information holding unit that holds information of the pattern table selected for the dot at the boundary position that appears first in each processing line among the head chips that form dots ahead of time,
A pattern table that is sequentially selected in units of one or a plurality of dots is applied to dots excluding the boundary portion, and the current processing is applied to all the dots in the boundary portion that are formed in advance in time. The selected pattern table is applied to the dot at the boundary position that appears at the beginning of the unit, and for the dot at the boundary portion that is formed with a delay in time, the pattern table selected before the several lines is used. And a selection information switching unit to be applied. The printing apparatus according to claim 1,
A printing apparatus characterized in that a single dot is formed by overprinting a plurality of ink droplets using a deflection ejection technique capable of landing ink droplets from a single nozzle to a plurality of dot positions. The printing apparatus according to claim 1,
A printing apparatus comprising: a plurality of ink droplets that are landed from the same nozzle on one dot. A pattern table used for forming each dot subjected to multi-tone quantization encoding is randomly selected in units of one or a plurality of dots, and ink is selected according to a pattern corresponding to the quantized value of each dot in the selected pattern table. In an inkjet printing apparatus equipped with a discharge control unit for controlling the discharge nozzle and discharge timing of droplets,
One line head used for forming each dot is composed of a plurality of head chips, and the formation of dots located near the boundary between two adjacent head chips is discharged from the two head chips. When it is formed with a time difference of several lines due to overprinting of ink droplets,
A boundary selection information holding unit that holds information of a pattern table selected for a dot at a boundary position that appears first in all processing lines among head chips that form dots ahead of time, until the end of all processing lines; ,
A pattern table that is sequentially selected in units of one or a plurality of dots is applied to dots excluding the boundary portion, and information held in the boundary selection information holding unit for dots located in the boundary portion And a selection information switching unit to which the pattern table is applied. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables In an inkjet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
A plurality of head chips constituting one line head are arranged by offsetting several lines in the paper feeding direction between the head chips adjacent in the line direction, corresponding to the boundary position between two adjacent head chips. When forming the dots to be formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines,
A boundary selection information holding unit that holds a pattern table selected according to the boundary position of the processing line that appears at the beginning of all the processing lines among the head chips that form dots ahead of time, and until the end of all the processing lines,
A pattern table that is sequentially selected in units of one or a plurality of dots is applied to dots excluding the boundary portion, and for the dots located in the boundary portion, the boundary selection information holding unit is classified according to the boundary position. And a selection information switching unit that applies a pattern table of information to be held. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables In an inkjet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
A plurality of head chips constituting one print head are arranged adjacent to each other in the relative direction of movement of the print head and the paper by being offset by several lines in the paper feed direction. When the formation of dots corresponding to the boundary position of two head chips is formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines,
A boundary selection information holding unit that holds information of the pattern table selected for the dot at the boundary position that appears first in each processing line among the head chips that form dots ahead of time,
A pattern table that is sequentially selected in units of one or a plurality of dots is applied to dots excluding the boundary portion, and the current processing is applied to all the dots in the boundary portion that are formed in advance in time. The selected pattern table is applied to the dot at the boundary position that appears at the beginning of the unit, and for the dot at the boundary portion that is formed with a delay in time, the pattern table selected before the several lines is used. And a selection information switching unit to be applied. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables In a pattern table optimizing device for an ink jet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
A plurality of head chips constituting one line head are arranged by offsetting several lines in the paper feeding direction between the head chips adjacent in the line direction, corresponding to the boundary position between two adjacent head chips. When forming the dots to be formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines,
A boundary selection information holding unit that holds information of the pattern table selected for the dot at the boundary position that appears first in each processing line among the head chips that form dots ahead of time,
A pattern table that is sequentially selected in units of one or a plurality of dots is applied to the dots excluding the boundary portion, and the dots in the current processing unit are applied to the dots in the boundary portion formed in advance in time. The selected pattern table is applied to the dot at the boundary position that appears first, and the pattern table selected before the several lines is applied to the dot at the boundary portion formed with a delay in time. A pattern table optimizing device comprising: a selection information switching unit. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables In a pattern table optimizing device for an ink jet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
One line head used for forming each dot is composed of a plurality of head chips, and the formation of dots located near the boundary between two adjacent head chips is discharged from the two head chips. When it is formed with a time difference of several lines due to overprinting of ink droplets,
A boundary selection information holding unit that holds information of a pattern table selected for a dot at a boundary position that appears first in all processing lines among head chips that form dots ahead of time, until the end of all processing lines; ,
A pattern table that is sequentially selected in units of one or a plurality of dots is applied to dots excluding the boundary portion, and information held in the boundary selection information holding unit for dots located in the boundary portion A pattern table optimizing device, comprising: a selection information switching unit that applies the pattern table. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables In a pattern table optimizing device for an ink jet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
A plurality of head chips constituting one line head are arranged by offsetting several lines in the paper feeding direction between the head chips adjacent in the line direction, corresponding to the boundary position between two adjacent head chips. When forming the dots to be formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines,
A boundary selection information holding unit that holds a pattern table selected according to the boundary position of the processing line that appears at the beginning of all the processing lines among the head chips that form dots ahead of time, and until the end of all the processing lines,
A pattern table that is sequentially selected in units of one or a plurality of dots is applied to dots excluding the boundary portion, and for the dots located in the boundary portion, the boundary selection information holding unit is classified according to the boundary position. A pattern table optimizing device comprising: a selection information switching unit that applies a pattern table of information to be held. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables A computer program for controlling the optimization operation of the pattern table in the ink jet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
A plurality of head chips constituting one line head are arranged by offsetting several lines in the paper feeding direction between the head chips adjacent in the line direction, corresponding to the boundary position between two adjacent head chips. When forming the dots to be formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines,
A process of holding the information of the pattern table selected for the dot at the boundary position that appears first in each processing line among the head chips that form dots ahead of time, for the several lines,
A process of applying a pattern table that is sequentially selected in units of one or a plurality of dots for dots excluding the boundary portion;
A process of applying the pattern table selected for the dot at the boundary position that appears first in the current processing unit to the dot at the boundary part formed in advance in time;
A computer program for causing a computer to execute a process of applying a pattern table selected a few lines earlier to a dot in a boundary portion formed with a delay in time. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables A computer program for controlling the optimization operation of the pattern table in the ink jet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
One line head used for forming each dot is composed of a plurality of head chips, and the formation of dots located near the boundary between two adjacent head chips is discharged from the two head chips. When it is formed with a time difference of several lines due to overprinting of ink droplets,
A process of holding the information of the pattern table selected for the dot at the boundary position that appears first in all the processing lines among the head chips that form dots ahead of time, until the end of all the processing lines,
A process of applying a pattern table that is sequentially selected in units of one or a plurality of dots for dots excluding the boundary portion;
A computer program for causing a computer to execute a process of applying a pattern table of information held in the boundary selection information holding unit to dots located at a boundary portion. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables A computer program for controlling the optimization operation of the pattern table in the ink jet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
A plurality of head chips constituting one line head are arranged by offsetting several lines in the paper feeding direction between the head chips adjacent in the line direction, corresponding to the boundary position between two adjacent head chips. When forming the dots to be formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines,
A process of holding the pattern table selected by the boundary position of the processing line that appears at the beginning of all the processing lines among the head chips that form dots ahead of time until the end of all the processing lines;
A process of applying a pattern table that is sequentially selected in units of one or a plurality of dots for dots excluding the boundary portion;
A computer program for causing a computer to execute a process of applying a pattern table of information held by boundary position to the boundary selection information holding unit for dots located at a boundary portion. Refers to a set of pattern tables that correlate dot patterns that define the relationship between nozzles that eject ink droplets and ejection timing and multi-value quantization values, and a pattern table that is randomly selected from the set of pattern tables A computer program for controlling the optimization operation of the pattern table in the ink jet printing apparatus equipped with a dot pattern conversion unit that converts a multi-value quantization value corresponding to each dot into a dot pattern,
A plurality of head chips constituting one print head are arranged adjacent to each other in the relative direction of movement of the print head and the paper by being offset by several lines in the paper feed direction. When the formation of dots corresponding to the boundary position of two head chips is formed by overstrike of ink droplets ejected from the two head chips after a time difference of several lines,
A process of holding the information of the pattern table selected for the dot at the boundary position that appears first in each processing line among the head chips that form dots ahead of time, for the several lines,
A process of applying a pattern table that is sequentially selected in units of one or a plurality of dots for dots excluding the boundary portion;
A process of applying the pattern table selected for the dot at the boundary position that appears first in the current processing unit to the dot at the boundary part formed in advance in time;
A computer program for causing a computer to execute a process of applying a pattern table selected a few lines earlier to a dot in a boundary portion formed with a delay in time.

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