JP4124074B2 - Discharge control device, liquid discharge device, discharge control method, recording medium, and program - Google Patents

Description

  The present invention relates to a droplet discharge device that discharges droplets and deposits them on an object, and a discharge control device that controls the discharge. The present invention also relates to a liquid ejection method and program for realizing the technology. The present invention also relates to a recording medium on which the program is recorded.

One of the head mechanisms of the liquid ejecting apparatus is a line head. The line head has a plurality of discharge ports (nozzles) arranged on one line, and can simultaneously draw the same number of pixels as the discharge ports.
International Publication No. 01/039981 Pamphlet JP 2003-226017 A

  By the way, a very large number of discharge ports are arranged in the line head. For this reason, an ejection port that cannot eject droplets may be found. In such a case, a method of correcting a defective portion using an ejection port adjacent to an ejection port that cannot eject droplets is employed. Specifically, the non-ejection location is made inconspicuous by correcting data given to other ejection ports that can eject droplets normally or by doubling the data of the non-ejection portion.

  These methods are effective when the ejection port is completely non-ejection. However, it is not effective when ejected to an incorrect position such as ejection bend.

  The present invention has been made in consideration of the above problems, and an object of the present invention is to propose a technique that can solve the problem of ejection failure with a simple configuration.

In order to realize such an object, the present invention proposes a discharge control device shown in FIG. 1 as a discharge control device that controls the discharge of droplets by the droplet discharge device. Note that a discharge control device having a discharge head that deflects and discharges droplets from one discharge port to a plurality of pixel regions is used.
The discharge control apparatus includes a determination unit 1 for determining a discharge position and a conversion unit 2 that converts gradation data into a discharge pattern using a correspondence table.

The determination unit 1 is for determining whether or not the gradation data to be converted is for a pixel affected by a droplet ejection failure. This is because different control is performed for pixels that are not affected by ejection failure and pixels that are affected by ejection failure.
In addition, the discharge ports having defects in discharge of droplets include discharge ports that do not discharge droplets at all, and discharge ports that have non-standard droplet discharge bends.

  The pixel affected by the ejection failure is a pixel that should eject a droplet if the ejection port where the malfunction is found in the ejection. Since the present invention is premised on deflected discharge, pixels corresponding to the number of deflected discharges correspond. For example, a pixel facing a defective ejection port with a deflection angle of zero, a pixel at a position where a deflected and ejected liquid droplet is suitable (here, a position where the liquid droplet is deposited when the deflection angle is not zero), Corresponds.

To explain with a specific example, the pixel areas in the positional relationship of N and N + 1 in FIG. 2 correspond. In FIG. 2, the ejection direction “without deflection” is represented by “0”, and the ejection direction “with deflection” is represented by “+1”.
In this case, if there is a discharge failure at the discharge port (nozzle) N, the pixel region N + 1 where a droplet from the discharge port can land also corresponds to a pixel affected by the discharge failure. FIG. 2 shows a case where a droplet is ejected to the right in the drawing by deflected discharge.

Of course, it is also possible to eject a droplet at a position two pixels or more away. Also, the discharge direction can be the left direction in the figure. In that case, the ejection direction can be expressed as “−1”. Of course, it is also possible to divide the droplets into both left and right.

The conversion unit 2 is provided to select one of two types of correspondence tables based on the determination result of the determination unit 1, and to convert the gradation data into an ejection pattern using the selected correspondence table.
Here, when the gradation data to be converted is for a pixel that is not affected by the ejection failure, the conversion unit 2 refers to the first correspondence table 3 for the pixel and ejects the gradation data. Convert to pattern.

  In addition, when the gradation data to be converted is for pixels affected by ejection failure, the conversion unit 2 arranges ejection data so that droplets are deflected and ejected only from ejection ports that operate normally. With reference to the second correspondence table, the gradation data is converted into an ejection pattern.

  That is, the conversion unit 2 is used for pixels that can be drawn only with normal ejection ports (hereinafter also referred to as “normal ejection ports”) and for pixels that are affected by ejection failures (hereinafter referred to as “related to ejection failures”). Gradation data is converted into a discharge pattern using different correspondence tables.

  At that time, the gradation data corresponding to the ejection port related to the ejection failure of the droplet is converted so that the droplet can be deflected and ejected only by the ejection port capable of normal ejection. As a result, it is possible to draw a pixel with the gradation required for the original position while removing the influence of the ejection failure.

  For example, in FIG. 2, when there is a discharge failure at the discharge port N, droplets are prevented from being discharged from the discharge port N to the pixel regions N and N + 1. That is, for the pixel region N, a predetermined gradation expression is realized by deflected discharge from the discharge port N-1. For the pixel region N + 1, a predetermined gradation expression is realized only by ejection from the ejection port N + 1.

The second correspondence table 4 includes a correspondence table 4A for discharge ports in which defective discharge is recognized, and a correspondence table 4B for discharge ports located in the direction of deflection control with respect to the discharge ports in which defective discharge is recognized. It is desirable to have two types.
In addition, when the first or second correspondence table includes a plurality of types of correspondence tables, the discharge control device selects any one of the plurality of types of correspondence tables for conversion of gradation data. It is desirable to have

  According to one aspect of the present invention, the droplets to be ejected from the ejection ports with defective ejection can be allocated to the ejection ports capable of ejecting normal droplets and deflected and ejected. Thereby, all the pixels can be drawn with the required gradation or with a practically sufficient quality.

Hereinafter, an embodiment of a droplet discharge device will be described using a printer that discharges ink droplets as an example. It should be noted that characteristics not particularly shown or described herein are selected from those known in the art.
In the following description, a case in which the preferred embodiment is realized as hardware will be described, but it can also be realized by software processing equivalent to such hardware.

When the present invention is implemented as a computer program, the program is stored in a computer-readable storage medium.
Examples of the storage medium include a magnetic storage medium such as a magnetic disk (flexible disk or hard disk) or magnetic tape, an optical storage medium such as an optical disk, an optical tape, or a machine-readable barcode, and a random access memory (RAM). In addition to semiconductor storage devices such as read only memory (ROM), other physical devices or media used to store computer programs are included.

Where the present invention is implemented in hardware, it may be implemented as an integrated circuit such as an application specific integrated circuit (ASIC) or other device known in the art.
Although the present invention is premised on a technique for deflecting and discharging droplets, an example of the technique is described in detail in the prior application of the present applicant. For example, it is described in detail in Japanese Patent Application No. 2002-320861, Japanese Patent Application No. 2002-320862, Japanese Patent Application No. 2003-037343, and the like. In the following description, only the relevant parts of the present invention will be described while avoiding redundant description of these deflecting discharge techniques.

(A) First Embodiment (a-1) Circuit Configuration FIG. 3 shows a configuration example of a droplet discharge device according to the first embodiment. This droplet discharge device can control the deflection of the droplet discharge direction by electrical control. In this example, as shown in FIG. 2, the one that can distinguish two pixel regions is used. Note that the direction of deflection control is the same for a plurality of discharge ports (nozzles) arranged on the line head.

  At this time, it is assumed that droplets are deflected and discharged in the same direction from all or one set of discharge ports within one discharge cycle which is the minimum unit of the drawing period of one pixel. In addition, the deflection direction in this example is alternately switched every discharge cycle.

A droplet discharge device that performs such deflection discharge is mainly composed of three functional units. The digital signal processing unit 11, the head controller 12, and the head chip 13 are provided.
The digital signal processing unit 11 is a functional unit that generates gradation data by multi-level error diffusion of image data. In this example, image data is input in 8 bits for each color. The digital signal processing unit 11 converts this into gradation data of 4 bits for each color and outputs it.

  “Gradation data” is data that defines the number of droplets that land on each pixel region. A method of expressing one pixel as a set of a plurality of droplets in this way is called a pulse number modulation method. Note that the value that the gradation data can take is determined according to the number of gradations to be expressed. In this example, one pixel is composed of a maximum of six droplets.

  The head controller 12 is a functional unit that converts gradation data into a corresponding ejection pattern and supplies it to the head chip 13 at a predetermined timing. The head controller 12 includes a pulse number conversion unit 12A, an ejection pattern storage unit 12B, a correspondence table selection unit 12C, an ejection position determination unit 12D, a buffer memory 12E, a writing counter 12F, and a reading counter 12G.

A pulse number modulation (PNM) unit 12A is a functional part that converts gradation data into an appropriate ejection pattern by referring to a correspondence table stored in the ejection pattern storage unit 12B. In this example, 4-bit gradation data is converted into an 8-bit ejection pattern.
The ejection pattern is data that defines the ejection timing of the droplet. Specifically, it consists of a sequence of ejection data indicating the presence or absence of ejection of a plurality of droplets.

  For example, if the discharge data indicating “discharge” is “1” and the discharge data indicating “no discharge” is “0”, the discharge pattern is given as a sequence of “1” and “0”. The length of the number sequence corresponds to the number of ejection cycles constituting the drawing period of one pixel. In the case of this example in which the drawing period of one pixel is composed of eight ejection cycles, the length of the number sequence constituting the ejection pattern is “8”. Each discharge data means whether or not to discharge droplets in a discharge cycle corresponding to the arrangement position.

FIG. 4 shows an example of the ejection pattern.
FIG. 4A shows an example of the ejection pattern PNM1 corresponding to the gradation data “1”. In the ejection pattern “1”, droplets are ejected only at one of the eight ejection cycles. There are eight possible pattern candidates for the ejection pattern “1” alone. The actual ejection period at which the liquid droplets are ejected depends on which of the pattern candidates is associated with the gradation data 1.

FIG. 4B shows an example of the ejection pattern PNM2 corresponding to the gradation data “2”. In the case of the ejection pattern PNM2, the droplets are ejected at two locations out of the eight ejection cycles. In this case, there are 28 pattern candidates. As shown in the figure, the ejection may be continuous or discontinuous. Also in this case, in which discharge cycle the liquid droplets are actually discharged depends on which of the pattern candidates is associated with the gradation data 2.
The same applies to other gradation data.

The ejection pattern storage unit 12B is a functional device that stores a plurality of types of correspondence tables in which gradation data and ejection patterns are associated with each other. In this example, two types for normal ejection and for ejection failure-related are stored.
The normal discharge correspondence table 12B1 stores only one type of correspondence table. That is, only one ejection pattern can be read for each gradation data.

The ejection failure-related correspondence table 12B2 employs an ejection pattern arranged so that ejection data indicating “ejection present” is not given to ejection ports where ejection failure is recognized. In this example, since the ejection direction is controlled in two directions, two types of correspondence tables 12B21 and 12B22 are stored.
One is a correspondence table 12B2 for an ejection port in which ejection failure is recognized. The other is a correspondence table 12B22 for discharge ports related to discharge failure.
The discharge port related to the discharge failure is a discharge port adjacent to the discharge port in which the discharge failure is recognized in the deflection discharge direction.

  This relationship will be described with reference to FIGS. FIG. 5 shows a state in which the converted ejection pattern is written in the buffer memory 12E. Each column address in FIG. 5 corresponds to a pixel area. For example, when there is no deflection control, droplets are ejected from the ejection port (nozzle) n corresponding to the column address n according to the ejection pattern “00001010”. Incidentally, the row address in FIG. 5 corresponds to eight ejection cycles.

  Note that the notation PNMi (i = 1 to 8) in FIG. 5 indicates a discharge pattern (discharge pattern in the line direction) for each discharge cycle. An arrow indicates the direction of deflected discharge. The direction of deflected discharge here is the same as the direction of deflected discharge shown in FIG. The notations “+1” and “0” represent the shift direction of the read address. This value coincides with the direction of deflection control, and the correspondence with the deflection direction is as shown in FIG.

In this way, in this example, the droplets ejected from one ejection port are deflection-controlled. For this reason, it is necessary to read out the ejection pattern from the ejection port (nozzle) in consideration of the deflection direction as shown by the shaded area in FIG. In the case of FIG. 5, droplets are discharged from the discharge port (nozzle) n according to the discharge pattern “00011110”.
That is, when there is a discharge failure in the discharge port (nozzle) n, it is necessary to determine the discharge pattern for the gradation data (for each pixel) so that all the discharge data in the shaded portion is “0”.

FIG. 6 is an example of a correspondence table for ejection failure in consideration of this deflection ejection. FIG. 6A corresponds to the correspondence table 12B21 for the discharge ports in which the discharge failure is recognized, and FIG. 6B corresponds to the correspondence table 12B22 for the discharge ports related to the discharge failure.
In FIG. 6, similarly to FIG. 5, the discharge cycle in which the discharge port (nozzle) n in which a discharge failure is recognized discharges droplets is shown by shading. As can be seen from the figure, all the discharge data in the shaded portion are set to “0”. On the other hand, the discharge data “1” is arranged in the discharge cycle other than the halftone so that the gradation expression according to the gradation data is possible.

It should be noted that the droplets can be discharged at any position as long as the discharge cycle is not shaded. In this example, the discharge data “1” can be arranged at any position within the four discharge cycles corresponding to half of the total eight discharge cycles.
Thus, the period that can be used for gradation expression is limited to half of the total ejection cycle. For this reason, when the gradation data exceeds the number of ejection cycles, the gradation that can be actually expressed is limited to the gradation that can be represented by a half cycle of the entire ejection cycle.

  The discharge pattern storage unit 12B generally uses a read only memory (ROM). However, a random access memory (RAM) or other semiconductor memory element can also be applied. When RAM is used, the correspondence table can be rewritten freely. That is, the discharge position can be changed to an arbitrary position. In addition, the storage unit can be a storage medium that can be detachably attached to the liquid ejection apparatus main body.

  The correspondence table selection unit 12C is a functional part that selects a correspondence table to be referred to by the pulse number conversion unit 12A according to the determination result of the ejection position determination unit 12D. This determination result is given as information indicating whether gradation data to be converted is ejected from a normal ejection port or ejected from an ejection port related to ejection failure.

  For example, in the case of gradation data corresponding to a pixel that is not affected by the ejection failure, the correspondence table selection unit 12C selects the correspondence table 12B1 for normal ejection. For example, in the case of gradation data corresponding to a pixel affected by ejection failure, the correspondence table selection unit 12C selects one of correspondence tables 12B21 and 12B22 for defective ejection.

In this example, the correspondence table 12B21 is selected first, and the correspondence table 12B22 is selected when the next gradation data is input. This is because, in the deflection direction of the present example, an ejection port in which ejection failure is recognized first appears, and then an ejection port affected by ejection failure appears.
Therefore, when the deflection direction is opposite to the present example, the selection of the correspondence table selection unit 12C is opposite to the present example.

The selection of the two correspondence tables 12B21 and 12B22 related to the ejection failure can be realized by, for example, a switch that performs a toggle operation. This switch is triggered by a determination result indicating that it is gradation data for a pixel affected by ejection failure.
Moreover, when the information about the content of the discharge failure is also given as the determination result of the discharge position determination unit 12D, either of the two correspondence tables can be selected based on the information. In this case, a switch for switching the selection destination based on the information may be prepared.

  The ejection position determination unit 12D is a functional part that determines whether or not the gradation data to be converted is a pixel affected by ejection failure based on the write address generated by the write counter 12F. FIG. 7 shows a configuration example of the discharge position determination unit 12D. In the case of this example, the ejection position determination unit 12D includes a defective position information storage unit 12D1 and a comparison unit 12D2. The defect position information storage unit 12D1 stores the position information of the pixel facing the discharge port where the discharge defect is recognized and the position information of the pixel affected by the discharge defect.

  The comparison unit 12D2 is a functional part that compares the position information generated by the write counter 12F with the defective position information. When both pieces of position information match, the comparison unit 12D2 determines that the gradation data is affected by ejection failure. On the other hand, when the two pieces of position information do not match, the comparison unit 12D2 determines that the gradation data is a pixel that can be normally drawn.

  When the correspondence table selection unit 12C regards the predetermined number of gradation data following the first ejection failure determination input as the gradation data of the pixels affected by the ejection failure, the failure position information storage unit 12D1 In this case, it is only necessary to store only the position information that is read out the fastest among the pixels affected by the ejection failure.

Thus, what is necessary is just to select a suitable thing according to the other process content and memory | storage content for the corresponding | compatible table selection part 12C and defect position information storage part 12D1.
The position information given from the write counter 12F to the comparison unit 12D2 has a phase with respect to the write address given to the buffer memory 12E so that the pulse number modulation unit 12A gives the pixel position of the gradation data to be processed. It is an advanced address.

  The buffer memory 12E is a functional part that temporarily stores the ejection pattern. The buffer memory 12E is composed of random access memories (RAM) 1 and 2. The random access memories 1 and 2 execute writing and reading of the ejection pattern in opposite phases, respectively. That is, one of the writing operations is during the other reading operation.

The write counter 12F is a functional part that generates a write address for the buffer memory 12E and position information for the comparison unit 12D2. The ejection pattern is written according to the generated writing address.
The read counter 12G is a functional part that generates a read address for the buffer memory 12E. The ejection data is read according to the generated read address. The reading of the discharge data here is executed every discharge cycle.

  The read counter 12G needs to generate a read address in consideration of deflection discharge from the discharge port. FIG. 8 shows a configuration example of the read counter 12G. As shown in FIG. 8, the read counter 12G includes a read address generation unit 12G1 and a read address shifting unit 12G2 that shifts the generated read address in conjunction with the direction of deflection control.

  Here, the read address shifting unit 12G2 has a value indicating the direction of deflection control in the column address among the read addresses input from the read address generating unit 12G1 (for example, “0” when there is no deflection and “+1” when there is deflection). ) And the addition result is given to the buffer memory 12C as a new column address. The row address is output as it is. FIG. 9 shows a configuration example of the read address shifting unit 12G2. The column address is changed by the adder 12G21.

In this way, the ejection data is read out from the buffer memory 12E in a zigzag manner as shown by hatching in FIG.
The head chip 13 discharges droplets from the corresponding discharge ports based on the discharge data read in this way. The discharge of the droplet is performed by the discharge driving unit 13A corresponding to the droplet discharge method.

(A-2) Processing Operation Next, the processing operation by the droplet discharge device shown in FIG. 3 will be described. First, in the digital signal processing unit 11, multilevel error diffusion processing is performed on 8-bit drawing data (including image data and character data) of each color. By this multilevel error diffusion processing, 8-bit drawing data is converted into 4-bit gradation data.

  The gradation data is given to the correspondence table selection unit 12C via the pulse number modulation unit 12A. At this time, the discharge position determination unit 12D determines whether the gradation data to be processed is not affected by the discharge failure or is affected by the discharge failure, and selects the determination result as a correspondence table. To part 12C.

  When the determination result is gradation data drawn only with a normal ejection port, the correspondence table selection unit 12C selects the correspondence table 12B1 and gives the ejection pattern read out to the pulse number conversion unit 12A.

  On the other hand, when the determination result is the gradation data for the pixel affected by the ejection failure, the correspondence table selection unit 12C first selects the correspondence table 12B21 and reads the corresponding ejection pattern. At this time, the ejection pattern shown in FIG. Following this reading, the correspondence table selection unit 12C selects the correspondence table 12B22 and reads the corresponding ejection pattern. At this time, the ejection pattern shown in FIG. 6B is read out.

That is, the gradation data of the pixels drawn only by the normally operating ejection ports are converted into ejection patterns using the normal operation correspondence table 12B1. In addition, the gradation data of the pixel affected by the ejection failure is converted into an ejection pattern using the two correspondence tables 12B21 and 12B22 for defective ejection.
Thus, all “0” ejection patterns are read from the buffer memory 12E to ejection ports having ejection defects. At this time, the ejection pattern is read out so that the gradation of the pixel given by the gradation data is maintained at the ejection outlet at the position following the ejection outlet having the ejection failure.

As described above, when the ejection ports having ejection failures are not continuous, it is possible to eject droplets so as to compensate for the failures. As a result, gradation can be expressed accurately.
A specific example is shown in FIG. FIG. 10 shows an example of the case where the ejection ports where ejection defects are recognized are continuously skipped in the line direction when there are two deflection ejection directions (when one pixel region is drawn by two ejection ports). is there.

In FIG. 10, the position of the ejection failure is indicated by a cross. Further, the shaded portion in the figure represents the ejection data read out to the ejection port where ejection failure is recognized. Discharge data “0” is given to the shaded portion.
In this way, even when one ejection failure continues by skipping, four pixels can be represented by a maximum of four droplets, as indicated by the ● marks in the figure. Of course, the droplet landing position is accurate. Therefore, if the maximum value of the gradation data is up to “4”, there is no deterioration of the drawing quality. Further, even when the maximum value of the gradation data exceeds 4, it is possible to realize drawing with almost the same gradation.

Next, another specific example will be described with reference to FIG. FIG. 11 is also common to the other examples in that there are two deflection ejection directions. The difference is that discharge ports where defective discharge is recognized are continuous in the line direction. In this case, correction similar to that in FIG. 10 can be performed only for the pixels at both ends of the three consecutive pixels. That is, if the maximum value of the gradation data is up to “4”, drawing can be performed without quality degradation.
However, for the pixel at the center of the three pixels, ejection data “0” is given for the entire ejection cycle, and correction of this pixel becomes impossible.

(A-3) Effects of the Embodiment If the droplet discharge device according to the present embodiment is used, even if there is an ejection port where ejection failure such as non-ejection or ejection bending is observed, the liquid can be accurately positioned at an appropriate gradation. Drops can be ejected.

(B) Second Embodiment (b-1) Circuit Configuration In this embodiment, as shown in FIG. 12, a case where droplets are deflected and discharged in three directions will be described. That is, a case will be described in which the direction of deflected discharge is changed to a total of three directions, two directions on the left and right.

  The basic configuration of the present embodiment is the same as the configuration shown in FIG. 3, and the read address shifting unit 12G2 adds “−1, 0, +1, − to the column address of the read address generated by the read address generating unit 12G1. “1, 0, +1, −1, 0” are added to realize deflection discharge of “left, straight, right, left, straight, right, left, straight”.

In the case of such deflection control, it is necessary to read out ejection data at the location indicated by hatching in FIG. That is, the discharge pattern “00100010” needs to be read.
As described above, when the nth discharge port is normal, there is no problem in such reading. However, if a discharge failure is recognized at the nth discharge port, all the discharge data in the shaded portion must be “0”.

FIG. 13 shows a correspondence table 12B2 for ejection failure specific to the present embodiment. The correspondence table 12B2 includes three types of correspondence tables 12B21, 12B22, and 12B23.
One is a correspondence table 12B21 for pixel positions facing an ejection port where ejection failure is recognized. FIG. 13B shows an example of the correspondence table 12B21. Here, the discharge data of the cycle in which the defective discharge port discharges droplets to the nth pixel is set to “0”. Specifically, the ejection data of the first bit, the fourth bit, and the seventh bit of the row address are set to “0”.

  Therefore, the gradation expression corresponding to each gradation data PNMi (i = 1, 2, 3, 4, 5) is realized by using the white portions in the drawing. In the case of FIG. 13B, the ejection of the droplet corresponding to the gradation data PNM1 is set at the 0th bit of the row address. In this example, since there are five white portions, the gradation of up to 5 drops can be expressed accurately.

  The remaining two correspondence tables will be described. First, the correspondence table 12B22 for the (n + 1) th pixel that is affected by the ejection failure will be described. FIG. 13C shows an example of the correspondence table 12B22. Here, the ejection data of the cycle in which the defective ejection port ejects droplets to the (n + 1) th pixel is set to “0”. Specifically, the ejection data of the second bit and the fifth bit of the row address are set to “0”.

  Also in this case, the expression of gradation according to each gradation data PNMi (i = 1, 2, 3, 4, 5) is realized using the white portions in the figure. In the case of FIG. 13C, the discharge of the droplet corresponding to the gradation data PNM3 is performed using the 0th bit, the 1st bit, and the 3rd bit of the row address. In this example, since there are six white portions, the gradation of up to six drops can be expressed accurately.

  Finally, the correspondence table 12B23 for the (n-1) th pixel that is affected by the ejection failure will be described. FIG. 13A shows an example of the correspondence table 12B23. Here, the ejection data of the cycle in which the defective ejection port ejects droplets to the (n−1) th pixel is set to “0”. Specifically, the discharge data of the 0th bit, the 3rd bit, and the 6th bit of the row address is set to “0”.

  Also in this case, the expression of gradation according to each gradation data PNMi (i = 1, 2, 3, 4, 5) is realized using the white portions in the figure. In the case of FIG. 13A, the droplets corresponding to the gradation data PNM2 are ejected using the first and second bits of the row address. In this example, since there are five white portions, the gradation of up to 5 drops can be expressed accurately.

(B-2) Processing Operation Next, the processing operation by the droplet discharge device shown in FIG. 3 will be described. The basic operation of the processing operation of this embodiment is the same as that of the first embodiment.
First, in the digital signal processing unit 11, multilevel error diffusion processing is performed on 8-bit drawing data (including image data and character data) of each color. By this multilevel error diffusion processing, 8-bit drawing data is converted into 4-bit gradation data.

  The gradation data is given to the correspondence table selection unit 12C via the pulse number modulation unit 12A. At this time, the ejection position determination unit 12D determines whether the gradation data to be processed corresponds to a pixel drawn only with a normal ejection port or a pixel affected by ejection failure. The determination result is given to the correspondence table selection unit 12C.

The correspondence table selection unit 12C selects the correspondence table 12B1 and gives the ejection pattern read by selecting the correspondence table 12B to the pulse number conversion unit 12A when the determination result means gradation data for a pixel drawn only with a normal ejection port. .
On the other hand, when the determination result means gradation data for a pixel affected by ejection failure, the correspondence table selection unit 12C first selects the correspondence table 12B23 and reads the corresponding ejection pattern. At this time, the ejection pattern shown in FIG.

Further, following this reading, the correspondence table selection unit 12C selects the correspondence table 12B21 and reads the corresponding ejection pattern. At this time, the ejection pattern shown in FIG. 13B is read. Further, after this reading, the correspondence table selection unit 12C selects the correspondence table 12B22 and reads the corresponding ejection pattern. At this time, the ejection pattern shown in FIG. 13C is read.

  That is, the gradation data of the pixels drawn only by the normally operating ejection ports are converted into ejection patterns using the normal operation correspondence table 12B1. In addition, the gradation data of the pixels from which droplets can be discharged from the defective discharge ports are converted into discharge patterns using the three correspondence tables 12B21 to 12B23 for defective discharge.

  Thus, all “0” ejection patterns are read from the buffer memory 12E to ejection ports having ejection defects. At this time, the ejection pattern is read out so that the gradation of the pixel given by the gradation data is maintained at the ejection ports located before and after the ejection port having ejection failure.

As described above, when the ejection ports having ejection failures are not continuous, it is possible to eject droplets so as to compensate for the failures. As a result, gradation can be expressed accurately.
A specific example is shown in FIG. FIG. 14 shows that when there are three directions of deflected discharge (when one pixel region is drawn with droplets from three discharge ports), two discharge ports in which defective discharge is recognized are continuously skipped in the line direction. This is an example of the case where it exists.

  In FIG. 14, the position of the defective ejection port is indicated by a cross. Further, the shaded portion in the figure represents the ejection data read out to the ejection port where ejection failure is recognized. Discharge data “0” is given to the shaded portion.

  In this way, even when two defective discharges are skipped, six pixels can be represented by a maximum of five or six droplets, as indicated by the ● marks in the figure. Of course, the droplet landing position is accurate. Therefore, if the maximum value of the gradation data is up to “5”, there is no deterioration in drawing quality in these six pixels. Also, even when the maximum value of the gradation data exceeds 5, some pixels can express gradations up to 6 drops, and a very high quality can be realized.

Next, another specific example is shown in FIG. FIG. 15 is also common to the other examples in that there are three deflection ejection directions. The difference is that one ejection port in which ejection failure is recognized continues in the line direction. In this case, it is possible to correct for five consecutive pixels. However, since the non-ejection period of the droplet is doubled for the central pixel, only a maximum of three droplets can be ejected to the pixel region.
However, other areas can be expressed by a maximum of 5 or 6 droplets, and sufficient quality can be ensured.

  The last specific example is shown in FIG. The case of FIG. 16 is also the same as the other examples in that there are three deflection ejection directions. The difference is that discharge ports where defective discharge is recognized are continuous in the line direction. In this case, it is possible to correct four consecutive pixels. However, the same gradation expression as the other is possible only for two pixels at both ends of the four pixels. The positions of both ends can be expressed by a maximum of 5 or 6 droplets.

However, for the two central pixels, only a maximum of two or three droplets can be ejected to the pixel region due to the non-ejection period. Even so, compared with the case where the liquid droplets cannot be discharged at all or when the liquid droplets are discharged to the wrong position, the liquid droplets can be discharged to an accurate position, but the deterioration in quality can be minimized.
However, if the maximum value of the gradation data in this pixel area is “2”, the required gradation expression can be completely realized.

(B-3) Effects of the Embodiment When the droplet discharge device according to the present embodiment is used, even when the discharge port has a discharge failure such as non-discharge or discharge bend, the liquid is accurately displayed at an appropriate gradation. Drops can be ejected.

(C) Third Embodiment Even in the case where there are four or more deflected discharge directions of droplets, the correspondence table for defective discharge ports is prepared as many as the number of deflected discharges as in the previous embodiments. The influence of ejection failure can be corrected. That is, the same correction effect can be realized when one pixel region is drawn with droplets ejected from four or more directions.

(D) Fourth Embodiment (d-1) Circuit Configuration FIG. 17 shows a configuration example of a droplet discharge device according to the fourth embodiment. Also in the case of this droplet discharge device, the basic circuit configuration and processing operation are the same as in the other embodiments.
As shown in FIG. 18, the characteristic configuration of this example includes a plurality of sets of correspondence tables 12B101 to 12B10N and 12B201 to 12B20N for each of the correspondence table 12B100 for normal ejection and the correspondence table 12B200 for ejection failure. Is a point.

  Each of the correspondence tables 12B101 to 12B10N and 12B201 to 12B20N is the same as the correspondence tables 12B1 and 12B2 in the first embodiment. In this embodiment, the correspondence table selection unit 12C selects any one of a plurality of correspondence tables, and then the selected correspondence tables 12B10i (i = 1 to N) and 12B20j (j = 1 to N). The same processing operation as in the other embodiments is executed.

  The normal ejection correspondence tables 12B101 to 12B10N are characterized in that at least one gradation data and the ejection pattern are associated with each other differently. The same applies to the correspondence tables 12B201 to 12B20N for defective ejection.

  In the case of the present embodiment, a method of converting the correspondence tables 12B101 to 12B10N and 12B201 to 12B20N randomly in units of pixels to convert even the same gradation data into different ejection patterns is adopted. By this method, even when the same gradation data is continuous, the ejection position (or ejection timing) is dispersed, and the influence on the refilling of the liquid after the liquid droplet is ejected, the influence of the casing vibration of the liquid ejection apparatus, etc. Can be reduced.

The selection of the correspondence table is executed by the correspondence table selection unit 12C. In this embodiment, the random number generator 12C1 is used to select one correspondence table based on the generated random number.
However, a correspondence table for correspondence table selection that associates the pixel positions with the correspondence tables 12B101 to 12B10N and 12B201 to 12B20N may be provided in the correspondence table selection unit 12C, and different correspondence tables may be selected for each pixel position.

In this case, as in the above-described embodiment, pixel position information may be input from the writing counter. For reference, an example of a correspondence table for selecting a correspondence table is shown in FIG. FIG. 19A is an example of a correspondence table having 2 rows and 2 columns. FIG. 19B is an example of a correspondence table having 3 rows and 3 columns.

(D-2) Processing Operation Next, the processing operation by the droplet discharge device shown in FIG. 17 will be described. First, in the digital signal processing unit 11, multilevel error diffusion processing is performed on 8-bit drawing data (including image data and character data) of each color. By this multilevel error diffusion processing, 8-bit drawing data is converted into 4-bit gradation data.

  The gradation data is given to the correspondence table selection unit 12C via the pulse number modulation unit 12A. At this time, the ejection position determination unit 12D determines whether the gradation data to be processed corresponds to a pixel drawn only with a droplet from a normal ejection port or a pixel affected by ejection failure. The determination result is given to the correspondence table selection unit 12C.

  In parallel with this, the correspondence table selection unit 12C, based on the random number generated by the random number generator 12C1, uses the correspondence tables 12B10i (i = 1 to N) and 12B20j (j = 1) used for conversion of the gradation data. -N) is selected one by one. One random number can be generated for each normal ejection correspondence table and one for the defective ejection correspondence table. Here, one correspondence table for normal ejection and one correspondence table for defective ejection are selected one by one based on one random number.

After the selection of the correspondence table, the correspondence table selection unit 12C refers to the correspondence table indicated by the determination result, and reads the ejection pattern corresponding to the gradation data. As described above, the ejection pattern read in this way is written into the buffer memory 12E via the pulse number conversion unit 12A.
Also in this case, an ejection pattern of “0” is read out to all ejection ports having ejection defects. In addition, the discharge pattern is read out so as to maintain the gradation of the pixel given by the gradation data at the discharge ports located before and after the discharge port having the discharge failure.

(D-3) Effects of Embodiment In the case of this embodiment, in addition to the effects of the above-described embodiments, it is possible to eliminate the unevenness of the discharge pattern. Thereby, it is possible to prevent the deterioration of the drawing quality due to the insufficient refilling after the liquid discharge. Further, even if the displacement of the ejection direction due to the housing vibration occurs, the displacement of the drawing position can be made inconspicuous by dispersing the ejection positions.

The present invention can be applied to a head portion of a printer that ejects ink droplets from a head. Further, the present invention can be applied to a signal processing circuit of the head unit. Further, the present invention can be applied to a printer having the head portion and other electric devices. The drawing target of the printer is not limited to paper, and may be a plastic member, a metal material, or other objects.
In addition, the present invention can be applied to an inspection apparatus that discharges an inspection sample as droplets.

It is a figure which shows the functional block structure of one invention. It is a figure which shows the positional relationship of the nozzle and pixel area | region at the time of performing deflection | deviation discharge (2 directions). It is a figure which shows the embodiment example of a liquid discharge apparatus. It is a figure which shows the relationship between gradation data and the discharge pattern which can respond | correspond to this. It is a figure which shows the reading method of the discharge data when a deflection direction is possible to 2 directions. It is a figure which shows the correspondence table for defective discharge ports, and the correspondence table for discharge ports affected by defective discharge. It is a figure which shows the structural example of a discharge position determination part. It is a figure which shows the structural example of a reading counter. It is a figure which shows the structural example of a read address shift part. It is a figure which shows the example of discharge when one defective discharge port exists in a skip. It is a figure which shows the example of discharge when a defective discharge port exists continuously. It is a figure which shows the reading method of the discharge data when a deflection direction is possible in 3 directions. It is a figure which shows the correspondence table for defective discharge ports, and the correspondence table for discharge ports affected by defective discharge. It is a figure which shows the example of a discharge when two defective discharge ports exist in a skip. It is a figure which shows the example of discharge when one defective discharge port exists in a skip. It is a figure which shows the example of discharge when a defective discharge port exists continuously. It is a figure which shows the other embodiment example of a liquid discharge apparatus. It is a figure which shows the case where the correspondence table for normal discharge and the correspondence table for discharge failure are comprised by the multiple correspondence table which can be selected, respectively. It is a figure which shows an example of the correspondence table for correspondence table selection.

Explanation of symbols

1 Judgment unit 2 Conversion unit 3 Correspondence table (for normal discharge)
4 Correspondence table (for defective ejection)
12 Head controller 12A Pulse number conversion unit 12B Discharge pattern storage unit 12B1 Correspondence table (for normal discharge)
12B2 correspondence table (for defective ejection)
12B21 Correspondence table (for discharge ports with defective discharge)
12B22 correspondence table (for discharge ports related to discharge failure)
12B100 correspondence table (for normal discharge)
12B200 correspondence table (for defective ejection)
12C Correspondence table selection unit 12C1 Random number generator 12D Discharge position determination unit 12D1 Defective position information storage unit 12D2 Comparison unit 12G Read counter 12G1 Read address generation unit 12G2 Read address shift unit

Claims (7)

An ejection control device that controls ejection of droplets by a droplet ejection device having an ejection head that deflects and ejects droplets from one ejection port to a plurality of pixel regions,
A determination unit that determines whether or not the gradation data that defines the number of droplets to be deposited on each pixel region is for a pixel affected by ejection failure;
When the gradation data to be converted is for a pixel that is not affected by the ejection failure, the ejection cycle linked to the deflection cycle and the presence or absence of ejection are referred to by referring to the first correspondence table for the pixel area. If the gradation data is converted into a discharge pattern for each pixel area associated with the pixel area, and the gradation data to be converted is for a pixel affected by a discharge defect, the second correspondence for the pixel area Referring to the table, the gradation data is converted into a discharge pattern for each pixel region in which the discharge cycle linked to the deflection cycle and the presence / absence of discharge are associated with each other so that droplets are deposited only from the normally operating discharge ports. ejection exit control device that having a conversion unit. In the discharge control device according to claim 1,
The second correspondence table includes a correspondence table for a pixel region facing an ejection port in which ejection failure is recognized, and a correspondence table for a pixel region located in the direction of deflection control with respect to the ejection port in which ejection failure is recognized. ejection out of the control device that having a two. In the discharge control device according to claim 1,
The first or second correspondence table, that if made of a plurality kinds of correspondence tables, further having a selector for selecting one of the plurality of types of correspondence tables for conversion of the gradation data ejection Out control device. A droplet discharge apparatus having a discharge head for deflecting and discharging droplets from one discharge port to a plurality of pixel regions,
Gray-scale data defining the number of droplets to be dripping in each pixel region, and determining whether the determination unit that the pixel influence of discharging failure range,
When the gradation data to be converted is for a pixel that is not affected by the ejection failure, the ejection cycle linked to the deflection cycle and the presence or absence of ejection are referred to by referring to the first correspondence table for the pixel area. If the gradation data is converted into a discharge pattern for each pixel area associated with the pixel area, and the gradation data to be converted is for a pixel affected by a discharge defect, the second correspondence for the pixel area Referring to the table, the gradation data is converted into a discharge pattern for each pixel region in which the discharge cycle linked to the deflection cycle and the presence / absence of discharge are associated with each other so that droplets are deposited only from the normally operating discharge ports. A conversion unit;
Than one ejection head for deflecting discharging droplets to a plurality of pixel areas from the discharge port, the liquid material discharge device that have a and a discharge driving unit for discharging droplets on the basis of the discharge pattern. A discharge control method for controlling the discharge of droplets by a droplet discharge device having a discharge head that deflects and discharges droplets from one discharge port to a plurality of pixel regions,
Determining whether the gradation data defining the number of droplets to be deposited on each pixel region is for a pixel affected by ejection failure;
When the gradation data to be converted is for a pixel that is not affected by the ejection failure, the ejection cycle linked to the deflection cycle and the presence or absence of ejection are referred to by referring to the first correspondence table for the pixel area. If the gradation data is converted into a discharge pattern for each pixel area associated with the pixel area, and the gradation data to be converted is for a pixel affected by a discharge defect, the second correspondence for the pixel area Referring to the table, the gradation data is converted into a discharge pattern for each pixel region in which the discharge cycle linked to the deflection cycle and the presence / absence of discharge are associated with each other so that droplets are deposited only from the normally operating discharge ports. ejection out of control how and having a step. On the computer,
A function for determining whether or not the gradation data defining the number of droplets to be deposited on each pixel region is for a pixel affected by ejection failure;
When the gradation data to be converted is for a pixel that is not affected by the ejection failure, the ejection cycle linked to the deflection cycle and the presence or absence of ejection are referred to by referring to the first correspondence table for the pixel area. If the gradation data is converted into a discharge pattern for each pixel area associated with the pixel area, and the gradation data to be converted is for a pixel affected by a discharge defect, the second correspondence for the pixel area Referring to the table, the gradation data is converted into a discharge pattern for each pixel region in which the discharge cycle linked to the deflection cycle and the presence / absence of discharge are associated with each other so that droplets are deposited only from the normally operating discharge ports. A computer-readable recording medium that records a program for executing the functions. On the computer,
A function for determining whether or not the gradation data defining the number of droplets to be deposited on each pixel region is for a pixel affected by ejection failure;
When the gradation data to be converted is for a pixel that is not affected by the ejection failure, the ejection cycle linked to the deflection cycle and the presence or absence of ejection are referred to by referring to the first correspondence table for the pixel area. If the gradation data is converted into a discharge pattern for each pixel area associated with the pixel area, and the gradation data to be converted is for a pixel affected by a discharge defect, the second correspondence for the pixel area Referring to the table, the gradation data is converted into a discharge pattern for each pixel region in which the discharge cycle linked to the deflection cycle and the presence / absence of discharge are associated with each other so that droplets are deposited only from the normally operating discharge ports. A program for executing functions and.

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