JP2006205616A - Image forming device, image processing method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which can form an image having high linearity at a peripheral edge thereof while suppressing banding. <P>SOLUTION: The image forming device comprises: a plurality of head blocks; a memory means for storing therein plotting data for designating a gradation value of each dot of a dot matrix; a plurality of nozzles arranged in the head blocks so as to form overlapping areas; a scanning means for changing relative locations of the head blocks with respect to a recording medium in upper and lower directions of an image; a first determining means for determining whether a processing objective dot falls in the overlapping area; a second determining means for determining whether the processing objective dot belongs to a right peripheral edge, a left peripheral edge, or a non-peripheral edge of the image, based on the gradation value of a peripheral dot of the processing objective dot; and a generating means for generating a nozzle control data for controlling operations of the plurality of nozzles, based on a result of the determination of the second determining means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an image forming apparatus having a print head formed by combining a plurality of head blocks, and an image processing method and program in the image forming apparatus.

An image forming apparatus having a droplet discharge mechanism such as an ink jet printer has a plurality of nozzles that discharge ink (droplets) in order to realize high-speed printing (image formation). The plurality of nozzles are mounted on the print head. Inkjet printers move paper (paper feed)
An image is formed on the paper by ejecting ink while scanning the print head in a direction perpendicular to the paper feed direction (such a printer is referred to as a “multi-pass printer”).
Multi-pass printers have a limitation in printing speed because they require scanning in two directions. Therefore, improvement in printing speed is desired.

As one means for increasing the printing speed, it is conceivable to set the scanning direction of the print head to one direction (only the paper feed direction). In order to perform printing only by scanning in one direction, the size of the print head needs to be equal to or larger than the width of the paper (recording material). Such a printer having a head having a size larger than the paper width is generally called a line head type printer. In a print head of a line head type printer, it is desirable that all nozzles are arranged in a line at regular intervals. However, the number of nozzles that can be mounted on one print head is limited from the viewpoint of cost and manufacturing technology. Therefore, in order to mount a large number of nozzles on the print head, a combination of a plurality of head members (hereinafter referred to as “head blocks”) having a certain number of nozzles is used. Thus, in the line head type printer, the size of the print head is expanded beyond the paper width by combining a plurality of head blocks.

However, the head block assembly (joining) accuracy is limited, and the distance between the nozzles at the joint of the two head blocks cannot be made completely constant. That is, the inter-nozzle distance at the joint between the two head blocks has a certain distribution. Here, when the inter-nozzle distance is long, a white streak that makes the ink thin is generated, and when the inter-nozzle distance is short, a dark streak is generated. Such occurrence of streaks is generally called “banding phenomenon”. In a multi-pass printer, since the head is scanned in a direction perpendicular to the paper feed direction, occurrence of banding in the paper feed direction can be suppressed. However, in the line head type printer, since scanning is performed in one direction (only in the paper feeding direction), banding may occur at the joint between the head blocks.

As a method of preventing the banding phenomenon, there is a method of providing an overlap portion between the head blocks. FIG. 8 is a schematic diagram showing the structure of the print head 100 having an overlap portion. The print head 100 includes two head blocks, a head block 110 and a head block 120. The head block 110 has eight nozzles 111 to 118, and the head block 120 has eight nozzles 121 to 128. The head block 110 and the head block 120 are joined so that the nozzle 118 and the nozzle 121 overlap (FIG. 8A: O portion). In order to avoid complication of the drawing, FIG. 8 shows an example in which the head blocks are joined so that one nozzle overlaps, but the head blocks may be joined so that a plurality of nozzles overlap. .
By providing the overlap portion in this way, it is possible to avoid an increase in the nozzle interval at the joint portion of the head block.

However, in the overlap portion, there are two nozzles corresponding to one dot in the data, so if no treatment is made, dots are hit from two nozzles for one dot in the data. (FIG. 8B: part O). Therefore, there is a problem that the banding phenomenon occurs because the color becomes darker in the overlap portion. As a technique for compensating for the banding phenomenon occurring in the overlap portion, there are techniques described in Patent Documents 1 and 2, for example. Patent Document 1 discloses a technique for controlling the nozzle so that dots are gradually reduced from one head block in the overlap portion and gradually increased from the other head block. Patent Document 2 discloses a technique for controlling a nozzle so that dots are randomly shot from two head blocks using a random number in an overlap portion. This prevents banding from occurring in the overlap portion (FIG. 8 (c): portion O).
Japanese Patent Laid-Open No. 5-57965 Japanese Patent Laid-Open No. 2004-50445

FIG. 9 is a diagram illustrating an example in which an edge (end portion) of an image to be printed covers an overlap portion. In any of the above-described techniques, as shown in FIG. 9, when the straight line portion of the image to be printed matches the overlap portion (for example, FIG. 9A: O portion), FIG. 9B )
As shown in the portion O, there is a problem that the linearity of the end portion of the figure is deteriorated, that is, the image quality is deteriorated.

The present invention has been made in view of the above circumstances, and in an image forming apparatus having a line head in which a plurality of head blocks are combined, even when a linear portion of an image to be drawn coincides with an overlap portion of the head block, An object of the present invention is to provide an image forming apparatus capable of forming an image having a highly linear end portion while suppressing the occurrence of banding.

In order to solve the above-described problem, the present invention provides a first storage unit that stores a plurality of head blocks and drawing data indicating an image, the drawing data specifying the gradation value of each dot of the dot matrix. A plurality of nozzles formed on each of the plurality of head blocks for forming an image on a recording material, wherein some of the plurality of nozzles overlap at a joint portion between two adjacent head blocks. An area is formed, and in the overlap area, two nozzles correspond to one dot in the dot matrix, and relative positions of the plurality of head blocks with respect to the recording material Of the drawing data stored in the first storage unit and the scanning unit that changes the vertical direction, the processing target dot is the overlap region. And whether the processing target dot belongs to the right end portion, the left end portion, or the non-end portion of the image based on the gradation value of the surrounding dots of the processing target dot. When the determination result of the second determination means and the determination result of the first determination means are affirmative, nozzle control data for controlling the operation of the plurality of nozzles is generated according to the determination result of the second determination means An image forming apparatus is provided. According to this image forming apparatus, in the overlap region, the edge (
The nozzles are distributed according to the position of the edge portion, and the same nozzle is in charge of dot drawing at the end portion. Therefore, an image having an end portion with high linearity can be formed.

In a preferred aspect, when the second determination means has more than a predetermined number of dots having a predetermined gradation value on the left side of the dot to be processed in the dot matrix, the dot to be processed Is determined to be the right end of the image, and when the dot of the predetermined gradation value continues for a predetermined number or more on the right side of the dot to be processed in the dot matrix, the dot to be processed is an image. You may judge that it is the left end of.

In another preferred embodiment, the image forming apparatus stores a reference pattern having a size equal to or smaller than the size of the dot matrix, and storing a reference pattern indicating a dot pattern in which the processing target dot is the right end portion or the left end portion of the image. Storage means, and comparison means for comparing an area including the processing target dot and having the same size as the reference pattern with the reference pattern, and the second determination means is the comparison means. Thus, when the region including the processing target dot matches the pattern at the right end of the reference pattern, it may be determined as the right end, and when it matches the pattern at the left end, it may be determined as the left end.

In still another preferred aspect, when the processing target dot is the left end portion of the image, the generation unit discharges a droplet from a nozzle located on the right side of two nozzles corresponding to the processing target dot. Nozzle control data to be generated, and when the processing target dot is the right end portion of the image, a nozzle that discharges droplets from a nozzle located on the left side of two nozzles corresponding to the processing target dot Control data may be generated.

In another preferred aspect, the apparatus further comprises third determining means for determining whether the drawing data has an area corresponding to any one of a chart, a character, and a line drawing, and the second determining means includes the third determining means. The determination process may be performed when the determination result by the determination means is affirmative. According to this image forming apparatus, when the drawing data relates to an image whose image quality is improved by obtaining an end portion having high linearity such as a chart, a character, or a line drawing, the nozzle corresponding to the position of the end portion of the image Is distributed. Therefore, the processing load can be reduced.

In still another preferred aspect, when the generation unit determines that the processing target dot belongs to a non-end portion of the image by the second determination unit, a right side of two nozzles corresponding to the processing target dot Nozzle control data that causes droplets to be discharged alternately or randomly from the nozzle located at the left side and the nozzle located at the left side may be generated. According to this aspect, in the non-overlapping region, the nozzles are distributed so that no banding occurs.

In yet another preferred embodiment, the image forming apparatus includes a third unit for storing image data.
Storage means, conversion means for converting the image data into image data having a resolution corresponding to the dot matrix, and 2 for the image data whose resolution has been converted by the conversion means.
You may further have a binarization means which performs a digitization process and produces | generates the said drawing data. According to this image forming apparatus, since nozzle control data can be generated from image data, it is not necessary to separately prepare an apparatus for performing image processing.

In the above aspect, the image forming apparatus may be a line head type ink jet printer. Thereby, it is possible to provide a line head type ink jet printer capable of forming an image having an end portion with high linearity while suppressing the occurrence of banding.

The present invention also provides a plurality of head blocks, first storage means for storing drawing data for designating the gradation value of each dot in the dot matrix, and a plurality of head blocks formed in each of the plurality of head blocks. A part of the plurality of nozzles forms an overlap region at a joint between two adjacent head blocks, and two nozzles correspond to one dot in the dot matrix in the overlap region. An image processing method in an image forming apparatus having a plurality of nozzles, wherein among the drawing data stored in the first storage unit, whether the processing target dot corresponds to the overlap region Based on the first determination step of determining and the continuity of gradation values in the surrounding dots of the processing target dot, the processing target A second determination step for determining whether the image belongs to a right end portion, a left end portion, or a non-end portion of the image; and if the determination result in the first determination step is affirmative, the second determination step And a generation step of generating nozzle control data for controlling the operation of the plurality of nozzles in accordance with the determination result in (1). According to this image processing method, the edge portion (
The nozzles are distributed according to the position of the edge portion, and the same nozzle is in charge of dot drawing at the end portion. Therefore, an image having an end portion with high linearity can be formed.

Furthermore, the present invention provides a plurality of head blocks, first storage means for storing drawing data for designating the gradation value of each dot in the dot matrix, and a plurality of head blocks formed in each of the plurality of head blocks. A part of the plurality of nozzles forms an overlap region at a joint between two adjacent head blocks, and two nozzles correspond to one dot in the dot matrix in the overlap region. In an image forming apparatus having a plurality of nozzles or a computer device connected to the image forming apparatus, among the drawing data stored in the first storage unit, the processing target dot is the overlap A first determination step of determining whether or not the region corresponds to a region, and a continuation of gradation values in peripheral dots of the processing target dot If the determination result in the second determination step for determining whether the processing target dot belongs to the right end portion, the left end portion, or the non-end portion of the image and the determination result in the first determination step is affirmative, There is provided a program for executing a generation step of generating nozzle control data for controlling the operation of the plurality of nozzles according to a determination result in the second determination step. According to this program, nozzles are distributed according to the position of the edge (edge) of the image to be formed in the overlap area, and the same nozzle is responsible for dot drawing at the edge. Therefore, an image having an end portion with high linearity can be formed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a functional configuration of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 converts the input image (RGB (red, green, blue) color multivalue) data into CMY.
This is an apparatus for converting to K (cyan, magenta, yellow, black) colors into nozzle control data for instructing ejection of ink from the nozzles, and ejecting ink according to the nozzle control data for printing. The resolution converter 11 converts the input color image data to a resolution that can be processed by the image forming apparatus 1. The color space conversion unit 12 converts RGB image data into CM.
Convert to image data in YK format. The quantization unit 13 converts the multivalued CMYK data into binary CMYK.
Convert to data. The nozzle distribution unit 14 performs a nozzle distribution process in the overlap portion of the head block. That is, as will be described later, in the overlap portion, there are two nozzles that can eject ink for one dot in the data. The nozzle distribution unit 14 determines which of the two nozzles ejects ink, and generates nozzle control data indicating whether or not ink ejection is necessary for each nozzle. Image forming unit 1
5 performs a printing process according to the nozzle control data.

FIG. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus 1. In the present embodiment, the image forming apparatus 1 is a line head type ink jet printer. CPU21 is
The print processing program stored in the ROM 22 is read and executed. The RAM 23
It functions as a work area when the CPU 21 executes the program. The I / F 24 is an interface for transmitting and receiving data and control signals to and from other devices. The image forming apparatus 1 can receive image data via an I / F 24 from an electronic device such as a personal computer (hereinafter “PC”) or a digital camera. RAM 23 is also I
Data received via / F24 is stored. The image forming unit 25 forms an image on a sheet according to the nozzle control data under the control of the CPU 21. The above components are connected to each other via a bus 26. When the CPU 21 executes the print processing program, the image forming apparatus 1 has functions corresponding to the functional components shown in FIG.

As shown in FIG. 2, the image forming unit 25 further has a configuration described below. The line head 31 is a print head having a plurality of nozzles that eject ink. The nozzle may be of any structure, such as a piezo type that discharges droplets with a piezoelectric body, or a heating type that discharges by heating. The line head 31 has a size equal to or larger than the maximum width of the paper that can be printed by the image forming apparatus 1. The ink tank 32 supplies ink to the nozzles, and is provided for each color of CMYK. The page buffer 37 is a memory that stores nozzle control data for one page of an image. The head drive circuit 33 outputs, to the line head 31, a control signal for causing ink droplets to be ejected from a specified nozzle among a plurality of nozzles mounted on the line head 31 under the control of the control unit 34. . In this way, ink droplets are ejected from the designated nozzle onto the paper. The ink droplets ejected from the nozzle
Form dots on the paper. Hereinafter, for convenience of description, discharging ink droplets from the nozzles is expressed as “dots on” and not discharging ink droplets from the nozzles as “dots off”. For example, “data for designating ON / OFF of dots” means data for designating whether or not to eject ink droplets for a designated nozzle.

Since the line head 31 has a size equal to or larger than the paper width, dots for one line can be formed. The motor 35 is a motor for moving the paper in a predetermined direction (paper feeding).
The motor drive circuit 36 outputs a drive signal to the motor under the control of the control unit 34. Motor 35
When the paper is moved by one line, the next line is drawn. In this way, the image forming apparatus 1 can form an image on one sheet only by scanning in one direction (paper feeding).

FIG. 3A is a schematic diagram showing the structure of the line head 31. The line head 31 includes a plurality of head blocks 41. FIG. 3 shows only two head blocks 41a and 41b in order to prevent the drawing from becoming complicated. Head block 4
Each of 1 has a plurality of nozzles 42. In order to prevent the nozzle interval in the direction orthogonal to the paper feed direction (A direction in FIG. 3) from expanding in the joining region of the adjacent head blocks 41, the two adjacent head blocks 41a and 41b are formed as shown in FIG. ) Are arranged alternately. Here, an overlap portion (FIG. 3A: O) where the nozzles 42 of the two head blocks 41 overlap is present at the joint between the head blocks 41a and 41b.

FIG. 3B is a diagram illustrating drawing data D for one line. FIG. 3C illustrates nozzle control data E for the drawing data D (nozzle control data Ea indicates control data for the nozzle 42a, and nozzle control data Eb indicates control data for the nozzle 42b). In the drawings and the following description, “0” means that no dot is formed.
“1” is data indicating formation of dots. “Dot” means an image formed on the paper by ink droplets ejected from the nozzle 42, but when used for data, it means a data unit for forming dots. Here, in the non-overlapping portion, it is a specific one nozzle that ejects ink onto the paper for the drawing data D of a certain dot. That is, in the non-overlapping portion, the drawing data D of a certain dot has a one-to-one correspondence with a specific nozzle. On the other hand, in the overlap portion (FIG. 3: O), one of the two overlapping nozzles discharges ink onto the paper for a certain dot drawing data. That is, in the overlap portion, there are two nozzles corresponding to the drawing data of a certain dot. Therefore,
It is necessary to perform a sorting process for determining which nozzle is to eject ink (in the example of FIG. 3C, the nozzles of the two head blocks are alternately distributed in the overlap region). This distribution process will be described later.

FIG. 4 is a flowchart showing the operation of the image forming apparatus 1. When a power source (not shown) of the image forming apparatus 1 is turned on, the CPU 21 reads a print processing program from the ROM 22 and executes it. When the print processing program is executed, the CPU 21 waits for input of image data. When the image data is received via the I / F 24, the CPU 21 converts the input image data to R
Store in the AM 23 (step S100). In this embodiment, the input image data is RG
B color multivalued image data. The image forming apparatus 1 is an ink jet printer that forms an image with CMYK four color inks. Therefore, the line head type image forming apparatus 1 needs to convert the color space of the image data from RGB to CMYK. The input image data has a gradation value for each pixel, but the ink ejected from the nozzles of the image forming apparatus 1 is dot ON / OFF (dots are not hit / not hit). An intermediate gradation cannot be expressed only by gradation. Therefore, in the image forming apparatus 1, an m × m dot matrix is associated with one pixel of image data, and gradation expression is performed by the number of dots drawn in the dot matrix. Therefore, it is necessary to convert the input image data into data that designates dot on / off. For this purpose, as will be described below, processing for converting the resolution of the image data into a resolution corresponding to the number of nozzles 42, and two gradations for specifying dot on / off for multi-gradation image data It is necessary to perform processing to convert to the data.

Subsequently, the CPU 21 determines the resolution of the input image data. When the resolution of the input image data is different from the resolution that can be processed by the image forming apparatus 1, the CPU 21
Resolution conversion processing is performed to obtain a resolution that can be processed by the image forming apparatus 1 (step S110).
The CPU 21 stores image data after resolution conversion (hereinafter referred to as “image data A”) in the RAM 2.
3 is stored. Subsequently, the CPU 21 converts the RGB image data into CMYK image data in order to adapt the image data A to the color space of the image forming apparatus 1 (step S120).
The CPU 21 stores image data after color conversion (hereinafter referred to as “image data B”) in the RAM 23. Subsequently, the CPU 21 performs nozzle control data generation processing described below on the image data B (step S130).

FIG. 5 is a flowchart showing details of the nozzle control data generation process. First, the CPU 21 binarizes the image data B by a technique such as an error diffusion method or a dither matrix method (step S131). The CPU 21 uses the binarized data as the drawing data D to generate the RA.
Store in M23. Next, the CPU 21 determines whether a drawing, character, or line drawing area (hereinafter simply referred to as “line drawing area” for simplicity) exists in the drawing data D (step S13).
2). This determination is performed as follows, for example. The RAM 23 or ROM 22 stores at least one basic pattern corresponding to a chart, character, or line drawing. This basic pattern is a pattern composed of a dot matrix of a certain size. The CPU 21 performs matching between the basic pattern and the drawing data D, and determines whether the drawing data D has an area that matches the basic pattern. When the drawing data D has an area that matches the basic pattern,
The CPU 21 determines that a line drawing area exists in the drawing data D.

When it is determined that a line drawing area exists in the drawing data D (step S132: YES),
The CPU 21 performs processing in steps S133 and S134 described later. If it is determined that no line drawing area exists in the drawing data D (step S132: NO), the CPU 21 advances the process to step S136.

Hereinafter, the CPU 21 performs the following processing on the drawing data in order of one dot.
First, the CPU 21 determines whether or not the processing target dot in the drawing data D belongs to the overlap region (step S133). This is performed, for example, as follows. The ROM 22 or RAM 23 stores information Q for specifying the overlap area. The information Q is, for example, the coordinates of the vertices of a polygon surrounding the overlap area in the dot matrix of the printable area. When there are a plurality (m) of overlap areas, ROM 22 or RAM
23 stores Q ₁ , Q ₂ ,..., Q _m and m pieces of information. The CPU 21 determines whether the processing target dot is located in the overlap region based on the coordinates of the processing target dot in the dot matrix and the information Q. When it is determined that the processing target dot is not included in the overlap area (step S133: NO), the CPU 21 advances the process to step S136. When it is determined that the processing target dot is included in the overlap region (step S133)
: YES), CPU21 advances a process to step S134.

FIG. 6 is a flowchart showing details of the nozzle distribution process in step S134. First, the CPU 21 determines the end (edge) direction of the processing target dot in the drawing data D (step S201). This process is performed as follows, for example. CPU2
First, it is determined whether the processing target dot is an on dot or an off dot. When the processing target dot is an off dot, the nozzle distribution process is not necessary. CPU
21 advances the processing to step S135 in FIG. When the processing target dot is an on dot, the end direction of the processing target dot is determined.

The CPU 21 determines that the processing target dot is the left end when the dot adjacent to the left of the processing target dot is an off dot and a predetermined number of on dots continue to the right of the processing target dot ( Step S201: Left). In this case, for the two nozzles corresponding to the processing target dot, the CPU 21 performs a process of distributing the nozzle control data to the nozzle located on the right side (step S202). This process is performed as follows. For example, the head block 41
Each is assigned an identification number in order from the left one. The CPU 21 refers to the identification number of the head block 41 to which the problematic nozzle is attached, sets the nozzle control data of the nozzle 42 of the head block 41 located on the left to “0”, and the nozzle 42 of the head block 41 located on the right. The nozzle control data is set to “1” and stored in the RAM 23. Alternatively, a database that records the relative positional relationship of the head blocks may be stored in the ROM 22 or the RAM 23, and the CPU 21 may assign nozzle control data with reference to this database. When the process is completed, the CPU 21 performs the process in step S135 (FIG. 5).
).

Similarly, the CPU 21 determines that the processing target dot is the right end when the dot on the right of the processing target dot is an off dot and a predetermined number of on dots are continuous to the left of the processing target dot. Judgment is made (step S201: right). In this case, for the two nozzles corresponding to the processing target dot, the CPU 21 performs a process of distributing the nozzle control data to the nozzle located on the left side (step S204). The process of step S204 may be performed in the same manner as the process of step S202 with the left and right reversed. When the process is completed, the CPU 21 advances the process to step S135 (FIG. 5).

When the processing target dot is neither the right end nor the left end, the CPU 21 determines that the processing target dot is not an end (step S201: NO). In this case, the CPU 21
For the nozzle corresponding to the processing target dot, a process of alternately distributing the discharge control data to the left and right nozzles is performed (step S203). That is, the CPU 21 starts from the RAM 23.
The nozzle control data of the two nozzles corresponding to the dot on one line of the processing target dot (this dot is also located in the overlap region) is read. The CPU 21 sets “1” when the read nozzle control data is “0”, and “0” when the read nozzle control data is “1”. Is stored in the RAM 23 as nozzle control data. As a result, the nozzle allocation for the processing target dots is opposite to the nozzle allocation for the line immediately above the processing target dots. That is, they are distributed alternately left and right. When the process is completed, the CPU 21 advances the process to step S135 (FIG. 5).

A description will be given with reference to FIG. 5 again. Step S136 defines the processing when the processing target dot is not included in the overlap region. In this case, the CPU 21 copies the data of the processing target dot and stores it in the RAM 23 as the nozzle control data of the processing target dot.

Subsequently, the CPU 21 determines whether the processing has been completed for all the dots of the drawing data D (step S135). When processing has not been completed for all dots (step S135: N)
In O), the CPU 21 changes the process target dot and repeatedly executes the processes of steps S133 to S134. When processing is completed for all dots (step S135: YES),
The CPU 21 ends the binarization process. Further, the CPU 21 performs the above processing on the data of each color of CMYK.

FIG. 7 shows nozzle control data E generated by the nozzle distribution process according to the present embodiment.
FIG. The nozzle control data Ea is control data for the head block 41a, and the nozzle control data Eb is control data for the head block 41b. CP
U 21 stores the generated nozzle control data E in the RAM 23.

A description will be given with reference to FIG. 4 again. The CPU 21 outputs the nozzle control data E stored in the RAM 23 (step S140). That is, the CPU 21 outputs a print command for instructing a printing process and at least a part of the nozzle control data E to the image forming unit 25. The image forming unit 25 performs nozzle control and motor control according to the nozzle control data E. That is, ink droplets are ejected onto the paper while feeding the paper, and an image for one page is formed on the paper.

By performing image formation as described above, while suppressing the occurrence of banding phenomenon,
The linearity of the image edge can be enhanced. That is, the image quality of the print image can be improved. For example, since the line head type ink jet printer has a head block for one line for each color of CMYK, the overlap area increases accordingly. Further, in order to improve the image quality, there are cases where multicolor inks such as six colors and seven colors are used, and the possibility that the edge of the image is applied to the overlap region is further increased. Furthermore, to increase the resolution,
In some cases, two-line head blocks are used for each color, and in that case, the possibility of the edge of the image being applied to the overlap region is doubled. As described above, as the performance of the ink jet printer such as the number of colors and the resolution is improved, the possibility of applying the present invention increases.

<Modification>
The present invention is not limited to the above-described embodiment, and various modifications can be made.
In the above-described embodiment, the image forming apparatus 1 performs resolution conversion processing, color space conversion processing, quantization processing, and nozzle distribution processing on the input image. You may do it with equipment. For example, a PC may be connected to the image forming apparatus 1 via a wired or wireless network or directly, and an image processing program operating on the PC may perform these processes. For example, the PC performs resolution conversion processing, color space conversion processing, and quantization processing on the image data, and outputs image data B (CMYK color binary data) to the image forming apparatus 1. The image forming apparatus 1 performs the nozzle distribution process described in the above embodiment on the image data B. Alternatively, the PC may generate nozzle control data E from the image data and output it to the image forming apparatus 1.

Even when the image forming apparatus 1 performs the above-described processing, the division of roles between the CPU 21 and the control unit 34 is not limited to that described in the above-described embodiment. For example, the CPU 21 may perform resolution conversion processing to quantization processing, and the back control unit 34 may perform nozzle control data generation processing (nozzle distribution processing).

In the above-described embodiment, the processing is performed in the order of resolution conversion processing, color space conversion processing, quantization processing, and nozzle control data generation processing, but the processing order is not limited to this.
For example, the processing may be performed in the order of color space conversion processing, resolution conversion processing, quantization processing, and nozzle control data generation processing.
Further, the color space conversion process may be a color space conversion process other than the conversion from RGB to CMYK. For example, in an image forming apparatus using seven color inks of black, cyan, magenta, yellow, light cyan, light magenta, and dark yellow, RGB format data is converted into image data for each of the seven colors.
In the image forming apparatus 1, the print head is fixed, and the paper is transported by the motor 35 to scan the head. However, scanning may be performed by fixing the paper and moving the print head.
The present invention may be applied not only to a line head type ink jet printer but also to a multi-pass type ink jet printer.

In the above-described embodiment, whether or not a line drawing area exists is determined by pattern matching in step S132, but the method for confirming the existence of a line drawing area is not limited to this. For example, the presence of the line drawing area may be determined by performing Fourier transform on the image data and determining whether or not a frequency component peculiar to the line drawing area has a predetermined intensity. Alternatively, a data format in which information indicating the presence or absence of a line drawing area is added in advance as the data format (format) of the image data, and the CPU 21 determines the presence or absence of the line drawing area based on the information added to the image data. May be. Further, the processing of steps S133 to S135 in FIG. 5 may be performed on all the image data without determining whether or not the line drawing area exists.

In the above-described embodiment, in step S201, the edge portion determination is performed based on the drawing data value of the dot adjacent to the processing target dot. However, the edge determination method is not limited to this. For example, a basic pattern for performing edge determination may be stored in the ROM 22 or the RAM 23, and the edge determination may be performed by matching an area including the processing target dot with the basic pattern. That is, the ROM 22 or the RAM 23 stores at least one reference pattern at the right end and at least one reference pattern at the left end.
When the region including the processing target dot matches the reference pattern at the right end, the processing target dot is determined to be the right end, and when it matches the reference pattern at the left end, the processing target dot is determined to be the left end.

In the above-described embodiment, the mode in which the nozzle control data is alternately distributed to the left and right nozzles in step S203 has been described. However, the nozzle distribution method when the processing target dot is not the edge of the image is not limited to this. For example, nozzle control data may be randomly distributed to the left and right nozzles using random numbers.

1 is a block diagram showing a functional configuration of an image forming apparatus 1 according to an embodiment of the present invention. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus 1. FIG. 3 is a schematic diagram showing the structure of a line head 31. FIG. 3 is a flowchart showing an operation of the image forming apparatus 1. It is a flowchart which shows the detail of a binarization process. It is a flowchart which shows the detail of a nozzle distribution process. It is a figure which illustrates nozzle control data E. It is a schematic diagram which shows the structure of the print head 100 which has an overlap part. It is a figure which shows the example which the edge part of the image printed prints on an overlap part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 11 ... Resolution conversion part, 12 ... Color space conversion part, 13 ... Quantization part, 14 ...
Nozzle sorting unit, 15 ... image forming unit, 21 ... CPU, 22 ... ROM, 23 ... RAM, 2
4 ... I / F, 25 ... Image forming unit, 26 ... Bus, 31 ... Line head, 31 ... Control unit, 32
DESCRIPTION OF SYMBOLS ... Ink tank, 33 ... Head drive circuit, 34 ... Control part, 35 ... Motor, 36 ... Motor drive circuit, 37 ... Page buffer, 41 ... Head block, 42 ... Nozzle, 100 ... Print head, 110 ... Head block, 111 -118 ... Nozzle, 120 ... Head block, 1
21-128 ... Nozzle

Claims (10)

Multiple head blocks;
First storage means for storing drawing data representing an image, the drawing data specifying the gradation value of each dot of the dot matrix;
A plurality of nozzles formed on each of the plurality of head blocks for forming an image on a recording material, wherein a part of the plurality of nozzles has an overlap region at a joint portion between two adjacent head blocks. A plurality of nozzles, wherein two nozzles correspond to one dot in the dot matrix in the overlap region;
Scanning means for changing the relative position of the plurality of head blocks with respect to the recording material in the vertical direction of the image;
First determination means for determining whether a processing target dot corresponds to the overlap area among the drawing data stored in the first storage means;
Second determination means for determining whether the processing target dot belongs to a right end portion, a left end portion, or a non-end portion of the image, based on gradation values in peripheral dots of the processing target dot;
An image forming apparatus comprising: generating means for generating nozzle control data for controlling the operation of the plurality of nozzles according to the determination result of the second determination means when the determination result of the first determination means is affirmative . The second determination means is
In the dot matrix, it is determined that the processing target dot is the right end of the image when a predetermined number of dots having a predetermined gradation value continue on the left side of the processing target dot.
In the dot matrix, it is determined that the processing target dot is the left end of the image when a predetermined number of dots having a predetermined gradation value continue on the right side of the processing target dot. The image forming apparatus according to claim 1. Second storage means for storing a reference pattern having a size equal to or smaller than a size of the dot matrix and indicating a dot pattern in which the processing target dot is a right end portion or a left end portion of an image;
A comparison unit that compares the reference pattern with a region that includes the processing target dot and has the same size as the reference pattern;
When the second determination unit determines that the region including the processing target dot matches the right end pattern of the reference pattern by the comparison unit, the second determination unit determines the right end portion and matches the left end pattern. The image forming apparatus according to claim 1, wherein is determined to be a left end portion. The generating means
When the processing target dot is the left end of the image, 2 corresponding to the processing target dot
Generate nozzle control data to discharge droplets from the nozzle located on the right side of the two nozzles,
When the processing target dot is the right end of the image, 2 corresponding to the processing target dot
The image forming apparatus according to claim 1, wherein nozzle control data for causing droplets to be ejected from a nozzle located on the left side of the two nozzles is generated. A third determining means for determining whether the drawing data has a region corresponding to any of a chart, a character, and a line drawing;
The image forming apparatus according to claim 1, wherein the second determination unit performs a determination process when a determination result by the third determination unit is positive. The generating means
When the second determination unit determines that the processing target dot belongs to the non-end portion of the image, the nozzle located on the right side and the nozzle located on the left side are alternately selected from the two nozzles corresponding to the processing target dot. 2. The image forming apparatus according to claim 1, wherein nozzle control data for causing droplets to be discharged at random or randomly is generated. Third storage means for storing image data;
Conversion means for converting the image data into image data having a resolution corresponding to the dot matrix;
The image forming apparatus according to claim 1, further comprising: binarization processing that performs binarization processing on the image data whose resolution is converted by the conversion device and generates the drawing data. The image forming apparatus according to claim 1, wherein the image forming apparatus is a line head type ink jet printer. A plurality of head blocks; a first storage means for storing drawing data for designating a gradation value of each dot of the dot matrix; and a plurality of nozzles formed in each of the plurality of head blocks, and adjacent to each other A part of the plurality of nozzles forms an overlap region in the joint portion of the two head blocks, and two nozzles correspond to one dot in the dot matrix in the overlap region. An image processing method in an image forming apparatus having a plurality of nozzles,
A first determination step of determining whether a processing target dot corresponds to the overlap region among the drawing data stored in the first storage unit;
A second determination step of determining whether the processing target dot belongs to a right end portion, a left end portion, or a non-end portion of the image based on continuity of gradation values in peripheral dots of the processing target dot;
An image processing method comprising: a generation step of generating nozzle control data for controlling the operation of the plurality of nozzles according to the determination result in the second determination step when the determination result in the first determination step is affirmative . A plurality of head blocks; a first storage means for storing drawing data for designating a gradation value of each dot of the dot matrix; and a plurality of nozzles formed in each of the plurality of head blocks, and adjacent to each other A part of the plurality of nozzles forms an overlap region in the joint portion of the two head blocks, and two nozzles correspond to one dot in the dot matrix in the overlap region. In an image forming apparatus having a plurality of nozzles or a computer device connected to the image forming apparatus,
A first determination step of determining whether a processing target dot corresponds to the overlap region among the drawing data stored in the first storage unit;
A second determination step of determining whether the processing target dot belongs to a right end portion, a left end portion, or a non-end portion of the image based on continuity of gradation values in peripheral dots of the processing target dot;
When the determination result in the first determination step is affirmative, a program for executing a generation step of generating nozzle control data for controlling the operation of the plurality of nozzles according to the determination result in the second determination step.

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