JP2014113708A - Image conversion device, image formation apparatus, image formation system, and producing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a density change of a printed image in a joint part and to improve image quality.SOLUTION: An image conversion device for converting image data per image unit output by being scanned by one or a plurality of recording heads includes an image data conversion unit that converts the image data so as to be able to form each pixel that forms a region in which end portions of the recording heads overlap in a case of scanning the image data so that the end portions of the recording heads overlap or that forms a region in which the end portions of the two adjacent recording heads overlap each other in a case in which the end portions of the two recording heads overlap each other by discharging ink at least twice using different nozzles.

Description

  The present invention relates to an image conversion apparatus, an image forming apparatus, an image forming system, and a production method.

  2. Description of the Related Art Conventionally, an image forming apparatus provided with an ink jet recording head can be configured at a relatively low cost, and is therefore used by various users regardless of personal or business use.

  In addition, there is a high demand for high-speed printing for users, and there is a printing mode (hereinafter referred to as a one-scan printing mode) in which printing for the recording head width is performed by one recording head scan in order to increase printing speed. In order to increase printing speed, a method of combining a plurality of recording heads (hereinafter referred to as a connecting head) is used in order to ensure a long recording width.

  High-speed printing and high-quality printing are in a trade-off relationship, and a technique for reducing image quality deterioration is used in the high-speed printing mode.

  In the one-scan printing mode, there is a technique (hereinafter, referred to as overlap between scans) in which the recording areas are partially overlapped for the purpose of reducing image quality deterioration at the boundary of the recording areas due to each scan of the recording head. In the connection head, a technique (hereinafter referred to as overlap between the heads) in which the ends of the recording head are overlapped by a predetermined nozzle width has been already used for the purpose of reducing image quality degradation at the end of the recording head. Are known.

  The area printed in the overlap area between scans and the area printed in the overlap area between nozzles are both printed with a predetermined number of nozzles, so both are not particularly distinguished. Also called.

  For example, when white stripes occur, the amount of ink discharged from the nozzles adjacent to the joints is increased, and when black stripes occur, the amount of ink discharged from the nozzles adjacent to the joints is increased or decreased. There is a technology (see, for example, Patent Document 1).

  In an image forming apparatus equipped with an ink jet recording head, a recording head is scanned to form an image of an area corresponding to the width of the recording head, and then a predetermined amount of recording paper is conveyed to form an image of the next area. I do. However, if the recording paper is not transported with high accuracy at this time, the relative positions of image formation in each scan of the recording head will not match, and a printed image will shift.

  In addition, when using the overlap between the heads in the connection head, if the positioning of the mounting positions of the recording heads is not performed with high accuracy, the relative positions of the nozzles between the recording heads will not match, and the ink landing position will not be correct. Will occur.

  The above-described print image shift and ink landing position shift are particularly noticeable in the one-scan print mode. When the amount of recording paper transport is large, or when the connecting head is mounted apart, the printed image becomes light (white stripes) at the connecting portion.

  In addition, when the amount of recording paper transport is small, and when the connecting head is attached close to the printed image, the printed image becomes dark (black stripes) at the connecting portion.

  Further, when the density change of the printed image at the joint portion as described above occurs, the image appears to be a band shape before and after the joint portion (banding), and the deterioration of the image quality becomes conspicuous.

  Further, in the technique in Patent Document 1, it can be said that the variation in the ink amount per area is reduced in an approximate range in which the entire connecting portion is regarded as the same region, and the variation in density is reduced from a macro viewpoint.

  However, if the region of the connecting portion and the front and back lines are considered as separate regions, a difference in density between the connecting portion and the region before and after the connecting portion may appear.

  Therefore, the conventional technique has a problem in that the deterioration of the image quality at the joint portion is not sufficiently improved due to the density change of the print image at the joint portion.

  Accordingly, an object of the present invention is to reduce the density change of a printed image at a joint portion and improve the image quality.

  An image conversion apparatus according to an aspect of the present invention is an image conversion apparatus that converts image data into image units to be output by scanning of one or a plurality of recording heads, and is scanned so that ends of the recording heads overlap. Each of the pixels forming the region where the ends of the recording heads overlap, or the region where the ends of the two adjacent recording heads overlap overlap each other with different nozzles. And an image data conversion unit that converts image data so as to be formed by at least two ink ejections.

  According to the present invention, it is possible to reduce the density change of the printed image in the joint portion and improve the image quality.

1 is a diagram illustrating a schematic configuration example of an image forming apparatus including an ink jet recording head according to Embodiment 1. FIG. The figure which shows an example of a structure of the mechanism regarding image formation. FIG. 3 is a diagram illustrating an example of a recording head. FIG. 3 is a block diagram illustrating an example of a configuration related to control of the image forming apparatus according to the first exemplary embodiment. The figure which shows an example of the overlap between nozzles. The figure which shows an example of the overlap between scans. FIG. 6 is a diagram for explaining image formation at a connecting portion in a comparative example. The figure explaining the subject of the image formation of the connection part by a comparative example. FIG. 5 is a diagram illustrating image formation at a connection portion in the embodiment. The figure which shows an example of an ink droplet size and an ink usage-amount. The figure which shows an example of the parameter of the data conversion of the connection part by an image data conversion part. The figure which shows the example of the image formation of the connection part at the time of using the conversion parameter shown in FIG. The figure which shows another example of the parameter of the data conversion of the connection part by an image data conversion part. The figure which shows an example of the pattern for a connection part adjustment. The figure which shows the example of the image formation of the connection part at the time of using the conversion parameter shown in FIG. The figure explaining the change of the ink usage-amount of an ink drop by the change of ambient temperature, and switching of the conversion parameter according to temperature. 5 is a flowchart illustrating an example of image conversion processing according to the first exemplary embodiment. FIG. 6 is a diagram illustrating line-type image formation. FIG. 4 is a diagram illustrating an example of an image forming system according to a second embodiment. FIG. 6 is a diagram illustrating a schematic configuration example of each unit according to the second embodiment. 10 is a flowchart illustrating an example of output product production processing according to the third embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
[Example 1]
<Configuration>
(overall structure)
FIG. 1 is a diagram illustrating a schematic configuration example of an image forming apparatus 100 including an ink jet recording head according to the first embodiment.

  The image forming apparatus 100 includes a cutter 1, a conveyance roller 2, an air suction device 3, a carriage 4, a recording head 5, a guide rod 6, a platen 7, a carriage motor 8, a paper feed motor 9, a motor control unit 10, recording paper (recording) Medium) 11.

  The recording paper 11 is a paper tube wound in a roll shape. The conveyance roller 2 conveys the recording paper 11 in the sub scanning direction. The sub-scanning direction is the Y direction. The transport roller 2 is rotated by driving the paper feed motor 9. The paper feed motor 9 is controlled by the motor control unit 10.

  The platen 7 supports the recording paper 11 conveyed by the conveyance roller 2. The air suction device 3 is provided in the lower part of the platen 7 and sucks air from an air hole formed on the platen 7. Thereby, the recording paper 11 is conveyed on the platen 7 without being bent.

  The carriage 4 is scanned in the main scanning direction when the recording paper 11 is conveyed by a certain amount. The main scanning direction is the X direction. The guide rod 6 supports the carriage 4. The carriage 4 supports the recording head 5. The carriage 4 is driven in the main scanning direction by a carriage motor 8. The carriage motor 8 is controlled by the motor control unit 10.

  The motor control unit 10 controls the carriage motor 8 and the paper feed motor 9. At the same time as the carriage 4 scans in the main scanning direction, ink is ejected from a plurality of nozzles provided in the recording head 5 to form an image on the recording paper 11. By repeating the conveyance of the recording paper 11 and the scanning of the carriage 4, image formation is realized.

  When there is no more data to form an image on the recording paper 11, the image forming operation ends. The recording paper 11 is cut by the cutter 1 and discharged by the subsequent conveyance roller 2.

  In addition to the ink jet system shown in FIG. 1, it goes without saying that the present invention can be applied to a general ink jet image forming apparatus in which recording paper such as A3 or B5 is arranged in a paper feed mechanism.

(Structure of the mechanism related to image formation)
FIG. 2 is a diagram illustrating an example of a configuration of a mechanism relating to image formation. As shown in FIG. 2, the carriage 4 is supported by a guide rod 6, and the carriage 4 moves in the main scanning direction (X direction). The carriage 4 forms an image by ejecting minute ink droplets onto the recording paper 11 using a plurality of recording heads 5 while moving.

  The recording paper 11 is supported by the platen 7 and is conveyed in the sub-scanning direction (Y direction) at the start of the image forming operation. The conveyance of the recording paper 11 and the movement of the carriage 4 are repeated to realize an image forming operation. When there is no more data to be recorded on the recording paper 11, the image forming operation is finished and the recording paper 11 is discharged.

(Recording head)
FIG. 3 is a diagram illustrating an example of a recording head. The recording head 5 has a plurality of nozzles 12. The nozzles 12 are arranged in a direction (sub-scanning direction: Y direction) perpendicular to the moving direction of the carriage 4 (main scanning direction: X direction) to form a nozzle row.

  The nozzle array composed of n1, n3, n5,..., n19 and the nozzle array composed of n2, n4, n6,..., n20 can eject the same color or different colors. . Further, as shown in FIG. 2, an image is formed on the recording paper 11 by ejecting ink from each nozzle 12 row of each recording head 5 arranged in the carriage 4.

(Configuration related to control)
Next, a configuration related to control of the image forming apparatus 100 will be described. FIG. 4 is a block diagram illustrating an example of a configuration related to control of the image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 includes an image conversion unit 101, a CPU (Central Processing Unit) 102, an image forming unit 103, and an operation display unit 104. The CPU 102 may be inside an external information processing apparatus.

  The image conversion unit 101 performs image data conversion processing in accordance with the head configuration, and can be mounted on, for example, one substrate. The image conversion unit 101 is also referred to as an image conversion device. The image forming unit 103 outputs image data to the recording head 5, controls the conveyance of the recording paper 11 and the movement of the carriage 4, and can be mounted on, for example, one substrate. The operation display unit 104 is an operation panel, for example.

  The image conversion unit 101 includes a RAM 111, an image processing unit 112, an interface 115, and an image data conversion unit 116. The image conversion unit 101 converts image data into image units to be output by scanning with one or a plurality of recording heads, and performs ink ejection control based on the converted image data.

  The RAM 111 is storage means and stores multi-value image data, image data converted into image units for one scan, and the like.

  The image processing unit 112 converts multi-value image data stored in the RAM 111 into small-value image data. Multi-valued image data is converted into the number of gradations equal to the type of droplet to be ejected.

  The interface 115 communicates with the CPU 102 and the image forming unit 103. For example, the interface 115 outputs a signal for ejecting ink from the recording head 5 to the image forming unit 103 based on the data converted by the image data conversion unit 116.

  The interface 115 also functions as input means for inputting height information indicating the level of density for each pixel formed in the connecting portion, and as input means for inputting temperature information indicating the temperature around the recording head 5. Also works.

  The image data conversion unit 116 outputs an image that is output by one head scan (one scan) for each recording head 5 in accordance with the print mode given by the CPU 102 and the configuration of the recording head unit 136 via the interface 115. Converts small value image data into units. The converted image data is stored in the RAM 111.

  Note that the conversion by the print mode may be performed by the image processing unit 112, and only the conversion process related to the recording head 5 may be performed by the image data conversion unit 116. Further, the image processing unit 112 and the image data conversion unit 116 may be the same functional block.

  For example, the image data conversion unit 116 uses different nozzles for each pixel that forms an area (joint portion) where the ends of the recording head 5 overlap when scanning is performed so that the ends of the recording head 5 overlap. Then, the image data is converted so as to be formed by at least two ink ejections. Further, the image data conversion unit 116 uses different nozzles to form pixels that form areas (joining portions) where the ends of two recording heads overlap when the ends of two adjacent recording heads overlap. Image data is converted so as to be formed by at least two ink ejections.

  Accordingly, since all the nozzles are used as much as possible instead of using the nozzles of the recording head at the connection portion, the change in density at the connection portion can be easily reduced.

  Further, the image data conversion unit 116 performs image processing so that the amount of one ink droplet is smaller than the appropriate amount of the other ink in at least two ink ejections using different nozzles for each pixel forming the overlapping region. Data may be converted.

  Thereby, it is possible to reduce the ink amount of the pixels in the joint portion and maintain the density before conversion.

  Further, the image data conversion unit 116 may switch the image conversion method for each pixel that forms an overlapping region so as to change the ink droplet amount based on the height information input by the interface 115. The height information will be described later.

  Thereby, the conversion parameter can be switched according to the black stripe and the white stripe, and the image quality at the joint portion can be improved.

  Further, the image data conversion unit 116 may switch the image conversion method for each pixel that forms an overlapping region so as to change the ink droplet amount based on the temperature information input from the interface 115.

  As a result, the conversion parameter can be switched according to the temperature around the recording head 5 to improve the image quality at the joint.

  The CPU 102 notifies the image conversion unit 101 of the print mode set by the user or the like, or notifies the image forming unit 103 of the paper feed amount.

  The image forming unit 103 includes an interface 131, a recording head control unit 132, a RAM 133, a motor control unit 134, a temperature sensor 135, and a recording head unit 136.

  The image forming unit 103 receives image data from the image conversion unit 101 via the interface 131 and records it in the RAM 133.

  The motor control unit 134 (the motor control unit 10 shown in FIG. 1) controls the paper feed motor 9 according to the paper feed amount notified by the CPU 102. Thereby, the recording paper 11 is sent in the sub-scanning direction.

  The recording head control unit 132 transfers the image data stored in the RAM 133 to the recording head unit 136 and ejects ink. In synchronization with the transfer of the image data, the motor control unit 134 controls the carriage motor 8. Thereby, the carriage 4 including the recording head unit 136 moves in the main scanning direction.

  The recording head 5 of the recording head unit 136 ejects ink onto the recording paper 11 in accordance with the image data transferred from the recording head control unit 132 to form an image. At this time, each pixel formed by the connecting portion is formed by ejecting ink at least twice using different nozzles.

  The temperature sensor 135 acquires the temperature around the image forming unit 103, for example, the recording head 5, and notifies the CPU 102 of the temperature information.

  The operation display unit 104 includes a display unit 141, an input unit 142, and an interface 143.

  The display unit 141 displays image information, character information, and the like transferred from the CPU 102 via the interface 143.

  The input unit 142 is a means for the user of the image forming unit 103 to input various settings such as printing conditions. The operation display unit 104 can send the input information to the CPU 102 via the interface 143.

<Overlap area (overlapping area)>
Next, the overlap area will be described. First, the overlap between nozzles will be described. FIG. 5 is a diagram illustrating an example of the overlap between nozzles. As shown in FIG. 5, the recording head 5 </ b> A and the recording head 5 </ b> B are arranged so that a predetermined number of nozzles at the end overlap each other. A head configured in the arrangement shown in FIG. 5 is called a connecting head. A region where the end nozzles of the recording head 5 overlap is called an inter-nozzle connection portion ar101.

  When the connecting head discharges ink while scanning in the main scanning direction and forms an image on the recording paper 11, a part of the image forming areas of the recording head 5A and the recording head 5B overlap as shown in FIG. This overlapping area is called an inter-nozzle overlap part ar102.

  Ideally, the nozzle inter-nozzle connection part ar101 is arranged so that the sub-scanning (Y direction) positions of the nozzles of the recording head 5A and the recording head 5B coincide. However, if the assembly at the time of connecting the recording heads 5 is not performed with high accuracy, the relative positions of the nozzles may be displaced, and image streaks or unevenness may occur in the inter-nozzle overlap portion ar102.

  In the example shown in FIG. 5, an example in which the end nozzles are overlapped by three nozzles is shown, but the number of overlapping nozzles is not particularly limited in the embodiment.

  Next, the overlap between scans will be described. FIG. 6 is a diagram illustrating an example of overlap between scans. The recording head 5 shown in FIG. 6 ejects ink while scanning in the main scanning direction, and forms an image on the recording paper 11 (scan 1). Thereafter, the recording paper 11 is conveyed in the sub-scanning direction, and the recording head 5 forms an image again (scan 2).

  At this time, by reducing the transport amount of the recording paper 11 by a predetermined number of nozzles with respect to the sub-scanning width of the recording head 5, a part of the image area formed by the scan 1 and the scan 2 can be overlapped. it can. This overlapping area is called an inter-scan overlap part ar103.

  In the inter-scan overlap portion ar103, it is ideal that the end nozzles in the scan 1 and the scan 2 are arranged so that the sub-scanning (Y direction) positions coincide. However, if the paper is not transported with high accuracy, the relative positions of the nozzles may be shifted when forming an image of the inter-scan overlap part ar103, and image streaks or unevenness may occur.

  In the example shown in FIG. 6, an example in which the end nozzles are overlapped by three nozzles is shown, but the number of overlapping nozzles is not particularly limited in the embodiment.

  The overlap between scans causes the recording head 5 to scan in a direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording paper 11. The overlap between scans is used only in an image forming apparatus (serial inkjet printer) that performs image formation by repeatedly scanning the recording head 5 a plurality of times and conveying the recording paper a plurality of times.

  On the other hand, the overlap between nozzles is also used in an image forming apparatus (line head type ink jet printer) that has a recording head for a recording width and forms an image by conveying a sheet once.

  The area printed at the overlap portion between the scans and the area printed at the overlap portion between the nozzles are both printed with a predetermined number of nozzles, and are not particularly distinguished in image formation. In the present embodiment, when referred to as a connecting portion, it includes both the inter-scan overlap portion and the inter-nozzle overlap portion.

<Image formation by comparative example>
Here, in order to explain the difference between the present embodiment and the prior art, first, image formation at a joint portion in a comparative example of the prior art will be described.

  FIG. 7 is a diagram for explaining image formation at a joint portion in a comparative example. In the example shown in FIG. 7, the same image is formed by the nozzles with overlapping sub-scanning positions in the joint portion, but the ink is ejected in an overlapping manner as it is, and the image density becomes high. For this reason, the image data conversion unit of the image conversion unit controls the ink ejection of each nozzle of the joint unit to avoid the density becoming dark.

  In the example shown in FIG. 7, an example of ink ejection control of each nozzle in the comparative example is shown. As shown in FIG. 7, the upstream recording head and the downstream recording head divide the ink into a staggered pattern as shown in FIG.

  The upstream recording head and the downstream recording head include the relationship between the recording head 5A and the recording head 5B of the connecting head shown in FIG. 5, and the scan 1 and scan 2 of the overlap between scans shown in FIG. Including both of the relationships.

  The comparative example is a technique for reducing image quality deterioration due to a connecting head assembly error and a recording paper conveyance error. However, even in this case, the image quality deterioration cannot be sufficiently reduced.

  In the example shown in FIG. 7, an example is shown in which one dot is placed alternately in the main scanning direction and the sub-scanning direction, but the way of placement is not limited to this method. In addition, the above-described problem cannot be solved even when image formation is performed in the image forming area ar201 at the joint portion using only the upstream recording head or only the downstream recording head.

  Next, the problem in the comparative example will be described with reference to FIG. FIG. 8 is a diagram for explaining a problem of image formation at a joint portion according to a comparative example. Schematic diagrams ar211 to ar213 shown in FIG. 8 are schematic diagrams showing dot landing positions. Further, white circles in the schematic diagrams ar211 to ar213 shown in FIG. 8 represent ink landing positions by the upstream recording head, and black circles represent ink landing positions by the downstream recording head. . The size of the circle represents the size of the ink droplet, that is, the amount of ink used.

  Schematic diagrams ar221 to 223 shown in FIG. 8 are schematic diagrams in which the amount of ink used is converted into density in an area of one pixel unit, and is an image diagram of an actually printed image.

  FIG. 8A is a schematic diagram in a case where the nozzle arrangement of the connecting portion is ideally arranged without deviation. The dots are evenly arranged, and there is no deterioration in the image quality at the joint.

  FIG. 8B is a schematic diagram in the case where the nozzle of the joint portion is located in a direction approaching. At the end of the joint, the density between dots is narrowed, and the image density is high. This phenomenon causes a black streak image.

  At this time, in the comparative example, the ink discharge amount of the nozzle adjacent to the joint portion is reduced, and dots are divided at the joint portion. When the dot placement shown in FIG. 7 is used, a placement pattern appears in the connecting portion, and the image quality deteriorates.

  FIG. 8C is a schematic diagram in the case where the nozzle of the joint portion is located in a direction away from the nozzle. At the end of the joint portion, the density between dots is sparse and the image density is low. This phenomenon causes a white streak image.

  At this time, in the comparative example, the ink discharge amount of the nozzles adjacent to the joint portion is increased, and dots are divided at the joint portion. When the dot placement shown in FIG. 7 is used, a placement pattern appears in the image and the image quality deteriorates.

<Image Formation by Example>
Next, image formation according to the embodiment will be described. FIG. 9 is a diagram for explaining image formation at a joint portion in the embodiment.

  As described above, in the joint portion, the same image is formed by the nozzles having the overlapping sub-scanning positions. However, the ink is ejected in an overlapping manner as it is, and the image density becomes high. For this reason, the image data conversion unit 116 of the image conversion unit 101 controls the ink ejection of each nozzle in the connection unit to avoid the increase in density.

  In the embodiment, an image is formed by using all the nozzles in the joint portion instead of ink separation by the nozzles in the joint portion. At this time, in the ink ejection control in the image data conversion unit 116, the droplet size of the connection part is changed so that the image density of the connection part does not change before and after the conversion. A specific example will be described later.

  The example shown in FIG. 9 shows an example of ink ejection control of each nozzle in the embodiment. As shown in FIG. 9, the upstream recording head and the downstream recording head change the droplet size as shown in FIG. 9 to form an image for the image forming area ar301 at the joint.

  As a result, the density change in the joint portion can be reduced and the black and white stripes can be made less noticeable. That is, it is possible to enhance the effect of reducing the image quality deterioration due to the connecting head assembly error and the recording paper conveyance error.

<Ink droplet size and ink consumption>
FIG. 10 is a diagram illustrating an example of ink droplet size and ink usage. FIG. 10 shows an example in which there are three types of droplet sizes ejected by the recording head 5: large droplets, medium droplets, and small droplets. The recording head 5 only needs to be able to form pixels with at least two types of ink droplet amounts.

  In the example shown in FIG. 10, the ink use amount ratio is large droplet: medium droplet: small droplet: no droplet = 12: 5: 2: 0.

  For example, when data for large droplet ejection is converted into data ejected by two nozzles by data conversion at the joint portion, the image data conversion unit 116 selects a combination with the smallest possible difference in ink usage before and after the conversion. For example, the image data conversion unit 116 can consider two patterns of printing with medium droplets + medium droplets or printing with large droplets + small droplets. In either case, the ink usage changes (large). Drop = 12, Medium drop + Medium drop = 10, Large drop + Small drop = 14).

  For this reason, the image data conversion unit 116 gives conversion parameters such that the amount of ink used per unit area does not change as much as possible. The conversion parameter will be described later.

  In the example shown in FIG. 10, an example in which the droplet size ejected by the recording head 5 is three types of large droplet, medium droplet, and small droplet is described, but in the embodiment, the number of droplet types is not limited to three. The same applies to the following embodiments.

  Further, when the amount of ink used for each droplet size changes due to an environmental change such as temperature or other factors, the image data conversion unit 116 may switch the conversion parameter according to the change in the amount of ink used.

<Conversion parameter>
FIG. 11 is a diagram illustrating an example of parameters for data conversion of the connection unit by the image data conversion unit 116. Hereinafter, this parameter is also referred to as a conversion parameter.

  FIG. 11A shows an example of conversion parameter information. The conversion parameter information holds the conversion parameter value in association with the droplet size to be converted when each value is set. The recording head at the connecting portion on the leading end side (coordinate 0 side) in the sub-scanning direction is called the upstream head, and the recording head at the connecting portion on the rear end portion is called the downstream head.

  FIG. 11B shows a conversion pattern p101 of conversion parameters for each nozzle output data of the head on the upstream side of the connecting portion. The first row shown in FIG. 11B is a parameter for the upper end nozzle of the upstream connection head section, the second row is a parameter for the second nozzle, and the third row is a parameter for the lower end nozzle.

  The column direction represents the main scanning position. Each time the main scanning position changes by one pixel, the conversion parameter is switched by one column. If the conversion parameters are switched for four columns, the process returns to the first column. That is, this conversion pattern p101 is repeated in the main scanning direction.

  FIG. 11C shows a conversion pattern p102 of conversion parameters for each nozzle output data of the head on the downstream side of the joint portion. The configuration of the conversion parameter shown in FIG. 11C is the same as the configuration shown in FIG.

  In this embodiment, the conversion pattern is obtained by alternately combining the case where the amount of ink used after conversion increases and the case where it decreases.

  The CPU 102 stores the upstream and downstream conversion patterns p101 and p102 in the internal recording area, and sets the upstream and downstream conversion patterns p101 and p102 in the image conversion unit 101 at the start of printing.

  In the present embodiment, an example in which the droplet size ejected by the recording head 5 is three types of large droplet, medium droplet, and small droplet is shown. However, in this embodiment, the number of droplet types is not limited to three. . The same applies to the following examples.

  FIG. 12 is a diagram illustrating an example of image formation at a connection portion when the conversion parameter illustrated in FIG. 11 is used. The effect of reducing the image quality degradation in the image at the joint shown in FIG. 12 will be described.

  Schematic diagrams ar401 and ar402 shown in FIG. 12 are schematic diagrams showing dot landing positions. The white circles shown in FIG. 12 represent ink landing positions by the upstream recording head, and the black circles represent ink landing positions by the downstream recording head. The size of the circle represents the size of the ink droplet.

  Schematic diagrams ar411 and ar412 are schematic diagrams in which the amount of ink used is converted into density in an area of one pixel unit, and is an image diagram of an actually printed image.

  FIG. 12A is a schematic diagram in the case where the nozzle of the joint portion is located in a direction approaching. When compared with the schematic diagram ar401 shown in FIG. 12A and the schematic diagram ar212 shown in FIG. 8B, the variation of the ink use amount per unit area is reduced.

  Thereby, the density change of the joint part of the printed image is reduced, and the black stripe can be made less noticeable.

  FIG. 12B is a schematic diagram in the case where the nozzle of the connecting portion is located in a direction away from the nozzle. As compared with the schematic diagram ar402 shown in FIG. 12B and the schematic diagram ar213 shown in FIG. 8C, the variation in the amount of ink used per unit area is reduced.

  Thereby, the density change of the joint part of a printed image can be reduced, and white stripes can be made less noticeable.

  By performing printing using all the nozzles as much as possible as in the above example, image deterioration due to the displacement of the nozzle position of the joint portion can be reduced.

  FIG. 13 is a diagram illustrating another example of parameters for data conversion of the connecting portion by the image data conversion unit 116.

  The diagram shown in FIG. 13 shows an example in which the conversion parameter of the joint portion data is switched when the nozzle of the joint portion is located in the approaching direction or away from the nozzle, that is, when the black stripe is generated and when the white stripe is generated. .

  The CPU 102 stores conversion patterns p111, p112, p121, and p122 in addition to the conversion patterns p101 and p102 in the internal recording area.

  Before printing, the user prints a pattern for adjusting the connecting part, and the image printed in the overlap part between nozzles and the overlap part between scans has black stripes, white stripes, or no stripes. Determine. Information (high / low information) indicating black streak, white streak or no streak is provided for each of the overlap portion between nozzles and the overlap portion between scans via the input unit 142 of the operation display unit 104 and image formation. Set in the section 103.

  The CPU 102 acquires information on black stripes, white stripes, and no stripes set by the user via the interface 143 of the operation display unit 104 and records the information in a recording area inside the CPU 102.

  The CPU 102 sets the conversion parameter of the connection portion data in the image conversion unit 101 at the time of printing in accordance with the information on the black stripe, the white stripe, and no stripe recorded in the internal recording area.

  When black streaks occur, conversion patterns p111 and p112 are set in the image conversion unit 101.

  When black streaks occur, the weight of ink droplets output from the lower end nozzle of the upstream head and the upper end nozzle of the downstream nozzle is reduced, and the density at the end of the joint portion is reduced.

  When white stripes occur, the conversion patterns p121 and p122 are set in the image conversion unit 101.

  When white streaks occur, the weight of the ink droplets output from the upper end nozzle of the upstream head and the lower end nozzle of the downstream nozzle is increased to increase the density at the end of the joint.

  When there is no streak, the conversion patterns p101 and p102 are set in the image conversion unit 101.

(Pattern adjustment pattern)
Here, the pattern for adjusting the connecting portion will be described. FIG. 14 is a diagram illustrating an example of a pattern for adjusting a connecting portion. The user selects printing of the pattern for adjusting the connecting portion via the input unit 142 of the operation display unit 104. After the user's selection, printing of the pattern of the recording head 5 shown in FIG. 14 is executed.

  At the time of printing this pattern, the image conversion unit 101 generates image data that prints the entire surrounding area including the joint portion with the same droplet.

  The CPU 102 sets, in the image conversion unit 101, patterns p131 and p132 for connecting portion adjustment that use all the nozzles of the upstream recording head and do not use all the nozzles of the downstream recording head.

  The user visually confirms the printed images i101 and i102, and compares the surrounding density with the density in the central portion.

  The user compares the surrounding density of the image i101 with the density of the central part, and the density of the central part is high, light, or the same is sent to the image conversion unit 101 via the input unit 142 of the operation display unit 104. Set. This setting result becomes information on black stripes, white stripes, and no stripes in the overlap portion between nozzles.

  The user compares the surrounding density of the image i102 with the density of the central part, and the central density is dark, light, or the same is sent to the image conversion unit 101 via the input unit 142 of the operation display unit 104. Set. This setting result becomes information of black stripes, white stripes, and no stripes in the overlap portion between scans.

  FIG. 15 is a diagram illustrating an example of image formation at a connection portion when the conversion parameter illustrated in FIG. 13 is used. The effect of reducing the image quality deterioration in the image at the joint shown in FIG. 15 will be described.

  Schematic diagrams ar501 and ar502 shown in FIG. 15 are schematic diagrams showing dot landing positions. The white circles shown in FIG. 15 represent the ink landing positions by the upstream recording head, and the black circles represent the ink landing positions by the downstream recording head. The size of the circle represents the size of the ink droplet.

  Schematic diagrams ar511 and ar512 are schematic diagrams in which the amount of ink used is converted into density in an area of one pixel unit, and is an image diagram of an actually printed image.

  FIG. 15A is a schematic diagram in the case where printing is performed using the conversion patterns p111 and p112 when the nozzles at the joint portion are located in the approaching direction, that is, when black stripes are generated. Comparing FIG. 15 (A) with FIG. 8 (B) and FIG. 12 (A), it can be seen that the density difference at the joint portion is further reduced.

  FIG. 15B is a schematic diagram when printing is performed using the conversion patterns p121 and p122 when the nozzles at the joint portion are located in the direction away from the nozzle, that is, when white stripes are generated. Compared to FIG. 15B, FIG. 8C, and FIG. 12B, it can be seen that the density difference at the joint portion is further reduced.

  The image data conversion unit 116 can further enhance the effect of reducing the image quality degradation by switching the conversion parameter of the connection portion data according to the information on the occurrence of black stripes and white stripes, that is, switching the image conversion method.

  In the present embodiment, a method of changing the coefficient of the conversion parameter of the joint data in two patterns at the time of occurrence of black stripes and at the time of occurrence of white stripes is shown. In addition, it is apparent that a higher effect can be obtained by changing the weight of the conversion parameter of the joint data under more detailed conditions from the density of black stripes and white stripes.

  Next, switching of conversion parameters based on temperature changes will be described. FIG. 16 is a diagram for explaining a change in ink usage of ink droplets due to a change in ambient temperature and switching of conversion parameters according to the temperature.

  The table shown in FIG. 16A shows the amount of ink used for large drops, medium drops, and small drops at each temperature. In the table shown in FIG. 16A, the amount of ink used varies depending on the ambient temperature.

  The amount of ink used varies depending on the ambient temperature, and the rate of change in the amount of ink used for large, medium, and small droplets varies. . In accordance with this change, conversion parameters in the connection part are created in advance, and the image data conversion unit 116 changes the conversion parameter in accordance with the ambient temperature, that is, switches the image conversion method, so that the connection part can be converted with higher accuracy. Image degradation can be reduced.

  The table shown in FIG. 16B shows an example of conversion parameters in the connection portion according to the ambient temperature. The CPU 102 stores conversion parameters (patterns 0A to 20C) of the connecting portions corresponding to the respective temperatures in advance in an internal recording area.

  At the start of image recording, the CPU 102 acquires temperature information acquired by the temperature sensor 135 of the image forming unit 103 from the image forming unit 103 via the interface 131. In the CPU 102, the conversion parameter of the connection unit corresponding to each temperature is set in the image conversion unit 101 according to the ambient temperature.

<Operation>
FIG. 17 is a flowchart illustrating an example of image conversion processing according to the first embodiment. The process shown in FIG. 17 is a flow in which the image conversion unit 101 processes data for image formation from multi-value print image data.

  In step S101, the image conversion unit 101 performs image processing in the image processing unit 112 when image formation is started. Here, the image processing unit 112 performs image processing on multi-valued image data that is a print image, and converts it into small-valued image data.

  The small-value image data is data corresponding to the droplet size ejected by the recording head 5. For example, if there are three types of droplet sizes, large droplets, medium droplets, and small droplets, no droplet (no ejection) data is obtained. It is converted into four-value data.

  In step S <b> 102, the image data conversion unit 116 performs image conversion processing for each image unit in which small-value image data is recorded (ink ejected) in the next one scan. Here, the image data conversion unit 116 converts the data into data that matches the configuration of the recording head 5, and converts the data into data to be recorded by each nozzle of the recording head.

  In step S <b> 103, when the image data conversion unit 116 starts the ink ejection control based on the image converted data, the image data conversion unit 116 determines whether or not the image converted data is an image of a joint portion. If it is an image at the joint (step S103-YES), the process proceeds to step S104, and if it is not an image at the joint (step S103-NO), the image conversion process ends.

  In step S <b> 104, the image data conversion unit 116 performs data conversion processing on the image at the joint portion. In this data conversion process, five data of the recording head 5 upstream of the joint portion and the recording head downstream of the joint portion are converted, and the droplet size of the dots ejected from the joint portion is converted.

  The image data conversion unit 116 performs the droplet size conversion in accordance with the conversion parameter given from the CPU 102 via the interface 115.

  By performing the above processing, an image is formed by using as many nozzles as possible in the joint portion, so that density change in the joint portion can be reduced and black stripes and white stripes can be made less noticeable.

  In the above example, the serial type image forming apparatus has been described as an example. However, the same method can be implemented in a line type image forming apparatus.

  FIG. 18 is a diagram illustrating line-type image formation. In the example shown in FIG. 18, the head fixing member 30 is fixed so as to be spanned from end to end in the main scanning direction (X) orthogonal to the sheet material (recording paper) 11 conveyance direction (Y).

  The head fixing member 30 is a member that fixes the recording head 5 from above, and the recording paper 11 is conveyed under the recording head 5. The head fixing member 30 is provided with KCMY ink recording heads 5 in the main scanning direction from the upstream side.

  The recording heads 5 for each color are arranged so that the end portions of the recording heads overlap each other. Ink is ejected from each recording head to form a color image. Even in the line type image forming apparatus, the overlap between the heads is used, and unless the positioning of the mounting position of the recording head 5 is performed with high accuracy, the relative position of image formation in each scanning of the recording head 5 is not aligned. Therefore, even in the line system, there is a problem that a printed image shift occurs in the joint portion. Therefore, the processing of the embodiment can be applied also to the line system image forming apparatus.

  As described above, according to the first embodiment, it is possible to reduce the density change of the print image in the joint portion and improve the image quality.

[Example 2]
Next, an image forming system in Embodiment 2 will be described. FIG. 19 is a diagram illustrating an example of the image forming system 150 according to the second embodiment. An image forming system 150 shown in FIG. 19 is connected so that data communication can be performed between a serial image forming apparatus 100 and a server (DFE: Digital Front End) 200 that is an information processing apparatus.

  Since the configuration of the image forming apparatus 100 is substantially the same as that of the first embodiment, the same reference numerals are given. The difference from the first embodiment is that the server 200 includes the configuration of the image conversion unit 101.

  The image forming system 150 is configured to perform image conversion processing in the server 200 so that the image forming apparatus 100 acquires data after image conversion and forms an image.

  FIG. 20 is a diagram illustrating a schematic configuration example of each unit in the second embodiment. A server 200 shown in FIG. 20 is connected to each PC (Personal Computer) so that data communication with the image forming apparatus 100 is possible.

  The server 200 includes a control unit 201, a main storage unit 202, an auxiliary storage unit 203, an I / F (interface) unit 204, and a network I / F unit 205.

  The control unit 201 is a CPU that controls each device, calculates data, and processes in the server 200. The control unit 201 is an arithmetic device that executes a program stored in the main storage unit 202. The control unit 201 receives data from the input device or the storage device, calculates and processes the data, and outputs the data to the output device or the storage device. The control unit 201 executes an image conversion program and executes the above-described image conversion process (the process of the image conversion unit 101).

  The main storage unit 202 is a ROM (Read Only Memory), a RAM (Random Access Memory), or the like, and a storage device that stores or temporarily stores programs and data such as an OS and application software that are basic software executed by the control unit 201. It is.

  The auxiliary storage unit 203 is an HDD (Hard Disk Drive) or the like, and is a storage device that stores data related to application software and the like. The auxiliary storage unit 203 stores a program for executing the above-described image conversion processing, and is managed by functions such as a database (DB: DataBase) and a file system (FS: File System).

  The I / F unit 204 is an interface that communicates with the image forming apparatus 100, and transmits data after image conversion to the image forming apparatus 100.

  The network I / F unit 205 has a communication function connected via a network such as a LAN (Local Area Network), a WAN (Wide Area Network), or a FAX constructed by a data transmission path such as a wired and / or wireless line. It is an interface such as each PC having.

  The image forming apparatus 100 includes a control unit (CPU) 102, an image forming unit 103, an operation display unit 104, and an I / F unit 105. In the configuration of the second embodiment, the same components as those of the first embodiment are denoted by the same reference numerals.

  The I / F unit 105 is an interface for communicating with the server 200. The I / F unit 105 acquires the image-converted data from the server 200 and outputs it to the image forming unit 103.

  As described above, according to the second embodiment, by providing the image conversion unit 101 in the external server 200 of the image forming apparatus 100, the same effect as that of the first embodiment can be obtained as the image forming system.

[Example 3]
Next, a method for producing an output product in Example 3 will be described. In the third embodiment, a method for producing an output product by performing image formation in the first and second embodiments on a recording paper (recording medium) will be described.

  The output in Example 3 is produced using ink and a recording medium. FIG. 21 is a flowchart illustrating an example of an output product production process according to the third embodiment.

  In step S <b> 201 shown in FIG. 21, the image conversion unit 101 performs the following conversion processing when converting image data into image units to be output in one scan of one or a plurality of recording heads.

  When the image conversion unit 101 performs scanning so that the end portions of the recording head overlap, each image forming region where the end portion of the recording head overlaps is ejected at least twice using different nozzles. The image data is converted so as to be formed by the above. Alternatively, the image conversion unit 101 uses each nozzle to form each pixel forming a region where the ends of the two adjacent recording heads overlap at least twice using different nozzles. The image data is converted so as to be formed by ink ejection.

  In step S202, the image forming unit 103 forms each pixel forming an overlapping region on the recording medium by using at least two ink ejections using different nozzles based on the image data subjected to the image conversion. As a result, an output product is produced.

  The processing of the image conversion unit 101 using the height information and temperature information described in the first embodiment is performed, and ink is ejected to the recording medium based on the processing, thereby generating an output product. Also good.

  The embodiments of the image conversion apparatus, the image forming apparatus, the image forming system, and the output production method have been described in detail above, but the present invention is not limited to the specific embodiments. Further, various modifications and changes other than the above-described embodiments are possible within the scope of the gist of the present invention described in the claims.

4 Carriage 5 Recording Head 8 Carriage Motor 9 Paper Feed Motor 10 Motor Control Unit 101 Image Conversion Unit 102 CPU
103 Image forming unit 111 RAM
112 Image processing unit 115 Interface 116 Image data conversion unit 131 Interface 132 Recording head control unit 133 RAM
134 Motor controller

JP 2010-260338 A

Claims (7)

An image conversion apparatus that converts image data into image units to be output by scanning one or more recording heads,
An area where the ends of the recording head overlap when scanned so that the ends of the recording head overlap, or the ends of the two recording heads when the ends of two adjacent recording heads overlap An image conversion apparatus comprising: an image data conversion unit that converts image data so that each pixel forming a region where the two overlap each other is formed by at least two ink ejections using different nozzles. The recording head can form pixels with at least two types of ink droplet amounts,
The image data converter is
2. The image conversion apparatus according to claim 1, wherein image data is converted so that one of the two ink ejections has an ink droplet amount smaller than an appropriate ink amount for each pixel forming the overlapping region. Input means for inputting high and low information indicating the level of density for each pixel formed in the overlapping region;
The recording head can form pixels with at least two types of ink droplet amounts,
The image data converter is
The image conversion apparatus according to claim 1, wherein an image conversion method for each pixel forming the overlapping region is switched so as to change an ink droplet amount based on height information input by the input unit. The input means includes
Input temperature information indicating the temperature around the recording head,
The image data converter is
The image conversion apparatus according to claim 3, wherein an image conversion method for each pixel forming the overlapping region is switched based on the temperature information so as to change an ink droplet amount. An image conversion apparatus according to claim 1;
An image forming unit having the one or more recording heads;
An image forming apparatus comprising: An information processing apparatus having the image conversion apparatus according to claim 1;
An image forming system comprising: an image forming apparatus connected to the information processing apparatus so as to perform data communication. A method for producing an output product that uses ink and a recording medium to produce an output product,
When image data is converted into image units to be output by scanning of one or a plurality of recording heads, an area where the end portions of the recording heads overlap or adjacent when scanning is performed so that the end portions of the recording heads overlap When the ends of the two recording heads overlap each other, each pixel forming an area where the ends of the two recording heads overlap is formed by ejecting ink at least twice using different nozzles. An image data conversion step for converting data;
An image forming step of forming each pixel forming the overlapping area on the recording medium by the two ink ejections based on the image data converted by the image data converting step;
Production method.