JP2007152844A - Printer and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer which can flexibly carry out a plurality of kinds of mask processing to disperse effects of a nozzle characteristic, etc. while suppressing a scale of the apparatus small, and to provide its control method. <P>SOLUTION: The printer capable of executing the plurality of kinds of mask processing for dispersing image data in one raster to a plurality of scans of a printing head includes a mask table and a mask processing means. The mask table is divided to a plurality of regions and stores in each of the regions a plurality of kinds of mask data which are data for performing the mask processing and have mutually different attributes. The mask processing means executes the mask processing by using the mask data in the region of the mask table where the mask data according to the kind of mask processing to be executed is stored. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printing apparatus and a control method therefor, and more particularly, to a printing apparatus and a control method therefor that can perform a plurality of types of mask processing flexibly while keeping the scale of the apparatus small.

  In a printing apparatus such as an ink jet printer that performs printing while a head having a plurality of nozzles that eject ink scans the print medium, the hardware characteristics and ink ejection characteristics of each nozzle are concentrated on the image and the image quality deteriorates. In order to prevent this, some techniques for improving image quality have been introduced.

  For example, the following patent document 1 or patent document 2 discloses a technique called an interlace method. Further, Patent Document 3 and Patent Document 4 below disclose a technique called a single ring method or a multi-scan method.

  Furthermore, there is a technique called mask processing as a technique for dispersing the nozzle characteristics and the like on an image to be printed. Such processing is performed by masking image data of each dot used for printing by using a mask table containing data consisting of 0 and 1 data called mask data, and scanning the head once. The image data to be printed is distributed.

  There are also several types of mask processing. For example, in a nozzle row having a plurality of nozzles in the sub-scanning direction, the above mask processing is performed on image data printed by nozzles provided at the upper end and lower end thereof. There are a POL (part overlap) method for performing, a distributed method for performing processing over the entire area of the image, and the like.

Conventionally, when performing a plurality of types of mask processing, the mask table is provided for each type in order to obtain a sufficient dispersion effect suitable for each type. For example, a printing apparatus that performs the POL method and the distributed method includes two mask tables for preparing a mask table for each method.
US Pat. No. 4,198,642 Japanese Patent Laid-Open No. 53-2040 JP-A-3-207665 Japanese Patent Publication No. 4-19030

  However, as described above, in the method of providing a mask table for each type of mask processing, when the mask processing is implemented in hardware for speeding up the mask processing, each memory for each mask table is on the chip. Therefore, the physical occupation area is large, which becomes an obstacle to downsizing of the chip and increases the cost.

  In addition, when a mask table dedicated to each mask process is provided as a memory for each mask process, in the case where different types of mask processes using different mask data are newly performed on the same apparatus, the memory capacity, etc. Therefore, there is a case where existing memory cannot be used effectively, which is not flexible.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a printing apparatus and a control method thereof that can flexibly perform a plurality of types of mask processing for dispersing the influence of nozzle characteristics and the like while keeping the scale of the apparatus small.

  To achieve the above object, according to one aspect of the present invention, there is provided a printing apparatus capable of executing a plurality of types of mask processing for distributing image data in one raster to a plurality of scans of a print head. A plurality of types of mask data that is divided into a plurality of areas and stores a plurality of types of mask data having different attributes from each other in each area, and the mask process to be executed And a mask processing means for executing the mask processing using the mask data within the area of the mask table in which the mask data corresponding to the type is stored.

  Furthermore, in the above invention, a preferable aspect thereof is that the mask processing means is configured to determine the start position in a predetermined area of the mask table based on a type of the mask processing to be executed. And an execution unit that reads the mask data from the head position and executes the mask process using the read mask data.

  Furthermore, in the above invention, according to one aspect, the mask table can change a size of the area and mask data to be stored, and the control unit performs the mask process when the mask process is performed. The area for storing mask data to be used is specified for the execution unit.

  Furthermore, in the above-mentioned invention, a preferred aspect is characterized in that the determination of the head position by the control unit is performed based on a raster position and a color of image data to be masked.

  In order to achieve the above object, another aspect of the present invention provides a printing apparatus control capable of executing a plurality of types of mask processing for distributing image data in one raster to a plurality of scans of a print head. In the method, the printing apparatus is divided into a plurality of areas, and each mask area stores a plurality of types of mask data that are data for the mask processing and have different attributes from each other. And when the mask process is executed, the mask process is executed using the mask data in the area of the mask table in which the mask data corresponding to the type of the mask process to be executed is stored. Is to control.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a configuration diagram according to an embodiment of a printing apparatus to which the present invention is applied. The printer 1 in FIG. 1 is a printing apparatus to which the present invention is applied. The printer 1 includes one mask table shared by a plurality of types of mask processing using different mask data, and the different mask data are divided by dividing the mask table. When storing and masking, it is possible to increase the scale of the apparatus by instructing the mask data to be used in the area in the mask table where the mask data corresponding to the processing is stored. It tries to be flexible while keeping it small.

  The printer 1 according to the present embodiment is, for example, an inkjet printer that can print in color. As shown in FIG. 1, the I / F 2, CPU 3, image processing unit 4, memory 10, local bus 9, and DSP 11 are used. , And a head 12 (print head).

  A print request and its image data transmitted from the outside such as a host computer are stored in the memory 10 via the I / F 2. Thereafter, the received compressed image data is subjected to decompression processing, color conversion processing, binarization processing, and mask processing by the image processing unit 4, DSP 11, etc., and the processed data is stored in the head. 12 is output. The head 12 sequentially ejects ink based on the transferred image data and executes printing on the print medium. In this printer 1, it is assumed that printing is performed by ejecting four colors of ink of C (cyan), M (magenta), Y (yellow), and K (black).

  The I / F 2 is a part that controls an interface with the outside of the printer 1 such as a host computer, and the CPU 3 is a part that controls the various image processes. The memory 10 is an external memory provided outside the image processing unit 4 and stores each image data in a state received from the outside and in a state after the processing of each image processing described above in a predetermined area. Therefore, data after decompression processing, data after binarization processing, data after mask processing, and the like are stored in the memory 10, respectively. The mask processing unit 7, which is a feature of the printer 1, reads and processes the binarized data stored in the memory 10 and writes the processed data back to the memory 10.

  Next, as shown in FIG. 1, the image processing unit 4 includes a path control unit 5, a decompression unit 6, a mask processing unit 7, a head output unit 8, and the like, and specifically includes an ASIC. . The path control unit 5 is a part that performs transfer control of data input to the printer 1 via the I / F 2, and the decompression unit 6 is a part that performs the decompression process on the compressed image data.

  The mask processing unit 7 is a characteristic part of the printer 1 and performs mask processing for dispersing image data printed by one scan of the head 12 on the image data after binarization processing. The mask processing unit 7 includes one mask table 71 used for mask processing.

  FIG. 2 is a diagram illustrating the mask table 71. As shown in FIG. 2, the mask table 71 is composed of 256 “1” or “0” numbers, and these numbers are referred to as mask data. One mask data of “1” or “0” corresponds to 1-dot image data. Here, the mask table 71 of the printer 1 is divided into two areas (area A and area B), and each area stores mask data having different attributes.

  In this example, the area A contains the mask data in which the numbers “1” and “0” are regularly arranged, and the area B contains the numbers “1” and “0” irregularly. The arranged mask data is stored. The printer 1 can execute two types of mask processing (mask processing A and mask processing B). In the mask processing A, it is necessary to use the mask data stored in the area A. In the process B, it is necessary to use the mask data stored in the area B. For example, in the POL mask process described above, the nozzles used for one raster (one line in the main scanning direction in the print image) may be regularly dispersed. This case corresponds to the mask process A. Further, in the above-described dispersion type mask processing or the like, the nozzles to be used are irregularly dispersed, which corresponds to the mask processing B.

  As described above, the main feature of the printer 1 is that the provided one mask table 71 is divided into a plurality of areas, and mask data having different attributes are stored in the respective areas. Note that the mask table 71 is stored in a memory (not shown) included in the mask processing unit 7, and the size of the mask table 71 is an example, and other sizes may be used. In this example, the mask table 71 is divided into two areas, and half the capacity is allocated to each area. However, the number of areas and the capacity of each area may be changed as necessary.

  The specific processing content by the mask processing unit 7 will be described later.

  Next, the head output unit 8 is a part that reads the image data after the mask processing and sequentially outputs it to the head 12.

  The DSP 11 is a processor (Digital Signal Processor) that performs the above-described color conversion processing and binarization processing, reads predetermined image data stored in the memory 10, executes the processing, and stores the processed data again in the memory. Write back to 10.

  As shown in FIG. 1, each processing unit of the image processing unit 4 and the memory 10 are connected by a local bus 9 for performing high-speed data communication with the memory 10 necessary for each processing unit. The local bus 9 is a so-called data bus, and a CPU bus that connects each processing unit in the image processing unit 4 and the CPU 3 is not shown in the image processing unit 4.

  Finally, the head 12 has a nozzle row 121 for each ink color (for each CMYK), and prints by sequentially ejecting ink according to the image data of each color transferred from the head output unit 8 while moving in the main scanning direction. This is the part that prints on the medium. FIG. 3 is a diagram schematically showing the nozzle row 121 provided in the head 12.

  As shown in FIG. 3, each color nozzle row 121 has 256 nozzles 122 (for example, C colors are C1 to C256) in the sub-scanning direction, and the four nozzle rows 121 as a whole are in the main scanning direction. Ink is discharged while moving to the position. The number 256 of nozzles 122 provided is an example, and other numbers may be used.

  As described above, the printer 1 having the above-described configuration has a feature with respect to the mask processing. Hereinafter, specific processing contents of the mask processing will be described. FIG. 4 is a flowchart illustrating an example of a mask processing procedure for image data. FIG. 4 shows a case where a certain type of mask processing is performed on one raster image data (one color), which is a processing unit of mask processing in the printer 1.

  First, the CPU 3 determines the type of mask processing to be performed on the image data (raster) to be processed (step S1). In the present embodiment, as described above, the mask process A and the mask process B are performed, so which process is determined in the current process. This determination is made based on the position of the nozzle 122 that prints the image data, the processing history so far, and the like.

  Next, the CPU 3 determines a head position on the mask table 71 in order to designate mask data used for the mask processing (step S2). This head position is the position of the data read pointer on the mask table 71, and means that the data stored in the mask table 71 are read in order from this position and used for mask processing.

  The determination of the head position is first performed in the area of the mask table 71 corresponding to the determined mask processing type. That is, when the mask process A is performed, the head position is determined in the area A storing the mask data for that purpose, and when the mask process B is performed, the head position is determined within the area B where the mask data is stored. Is determined.

  In addition, the position in each area is determined based on the raster position and color of the processing target data. In particular, in the area B where data is irregularly arranged, for the neighboring raster, The mask data used in the mask processing performed for different colors of the same raster is performed so that the position on the mask table 71 is sufficiently separated. For example, for different colors of the same raster, the head position is determined as a position shifted vertically and horizontally from other colors in the region. Further, an arbitrary position in the region may be determined at random for each raster position and color.

  When the head position is determined in this way, the CPU 3 instructs the mask processing unit 7 to perform mask processing on the image data (step S3). Specifically, the mask processing unit 7 is notified of the raster position to be processed, the type of the determined mask process, and the determined start position together with the execution instruction of the process. The head position is indicated by the position (address) from the head of the mask table 71 (upper left of the table shown in FIG. 2) or the position (address) in the area to be used.

  The mask processing unit 7 that has received the instruction first reads image data of the raster to be processed from the memory 10 (step S4). 5 and 6 are diagrams for explaining the mask process B and the mask process A, respectively. (A) of FIG. 5 schematically shows image data for one surface of the print medium. As shown in the figure, the image data of the raster (i) is sequentially from the left in the main scanning direction. I1, i2,... Are arranged for each dot. In reading the image data, for example, the image data of the raster (i) is read.

  Next, the mask processing unit 7 reads the mask data from the instructed head position of the mask table 71 provided in itself (step S5). FIG. 5B illustrates the designated head position. FIG. 5 shows only the region B in the mask table 71 because the type of processing is the mask processing B. The position indicated by the upward arrow in the figure is, for example, the head position, which is read rightward from the data “1” stored in this position (the part surrounded by the bold line in the figure). Used as mask data. That is, in this example, data “1, 1, 0, 0, 1,...” Is read from the head position. The order of reading data from the head position on the mask table 71 will be described later.

  FIG. 6 illustrates the case of the mask processing A as described above. In this case, for example, the image data of the raster (j) shown in FIG. And it is regularly arranged “0, 1, 0, 1,...” From the head position (position indicated by the upward arrow in the figure) in the area A shown in FIG. Mask data is read out.

  Next, the mask processing unit 7 performs multiplication of the read image data and the read mask data (step S6). Specifically, a process is performed in which image data and mask data are taken out one by one in order and multiplied. In the example of FIG. 5, raster (i) image data shown in (a) of FIG. 5, i1, i2, i3, i4, i5, and mask data from the head position shown in (b) of FIG. , “1, 1, 0, 0, 1,...” Are multiplied one by one in order. The result of such multiplication is shown in FIG. That is, the image data i1 is multiplied by the first mask data “1” and remains as it is, and the image data i2 is multiplied by the second mask data “1”, which is also the data as it is. The remaining image data i3 is multiplied by the third mask data “0” to obtain a calculation result of 0.

  In the example of FIG. 6, the image data of the raster (j) shown in FIG. 6A, j1, j2, j3, j4, j5, and the start position shown in FIG. The mask data “0, 1, 0, 1, 0,...” Are multiplied one by one in order. Similarly, the result of such multiplication is as shown in FIG.

  In this way, by multiplying the image data by the mask data, the image data corresponding to the mask data of “0” becomes a value of 0 regardless of the original value, and the ink in the head 12 corresponding to the image data. The discharge is not performed. Accordingly, these image data are masked, and are processed so as to be the target of ink ejection in the second process for the raster, which will be described later. Note that the image data i1, i2, and j1, j2,... May be 1-bit data or 2-bit data. In the case of 1-bit data, the DSP 11 outputs 1-bit data per dot when the binarization is performed, but in the case of 2-bit data, the DSP 11 similarly outputs 2-bit data per dot during processing. . For simplicity, the data after processing by the DSP 11 is collectively referred to as the data after binarization.

  Next, the mask processing unit 7 writes the calculated image data back to the memory 10 (step S7). In the example of FIGS. 5 and 6, the data shown in FIG. 5C and FIG. 6C is written back. Thereafter, the rewritten image data is transferred to the head 12 via the head output unit 8, and ink is ejected based on the image data. For example, when the image data subjected to the masking process is C color data, the C image data of the raster is printed by the nozzle 122 of C1, for example.

  This completes the masking process for each processing unit. However, as described above, the masked portion remains in the image data of the raster, so that the entire raster is printed in the current printing. Instead, the process of the masked part will be performed later.

  The latter half of the process is performed when various processes in the printer 1 are changed and the same type of mask process is again performed on the image data of the same color of the raster at a predetermined timing. In the example of FIGS. 5 and 6, the second mask process is performed on the image data of the raster (i) and the raster (j) shown in FIGS. 5 (a) and 6 (a).

  In this process, the same process as the first process described with reference to FIG. 4 is performed, but the head position determined in the first process is stored by the CPU 3, and the stored head position is the corresponding one. It is also used for the second processing. Also, in the multiplication (S6) of the image data and the mask data, unlike the first time, the image data is multiplied after the read mask data is inverted. That is, multiplication is performed with “0” when the read mask data is “1” and with “1” when the read mask data is “0”.

  In the example of FIG. 5, as described above, the mask data “1, 1, 0, 0, 1,...” Is read and “0, 0, 1, 1, 0,. Inverted and multiplied with the image data, i1, i2, i3, i4, i5,.

  FIG. 5D shows the calculation result. This time, image data such as i3 and i4 is left, and i1, i2 and the like are masked. This also applies to the example shown in FIG. 6, and the result of multiplication is as shown in FIG. 6 (d).

  Thereafter, the result is written back to the memory 10, and then the written image data is transferred to the head 12 via the head output unit 8 and ink ejection based on the image data is performed as in the first time. Will be made.

  The ink ejection of this time is naturally performed by a pass (scanning) of the head 12 different from the first time, but is performed by the nozzle 122 different from the first time in order to obtain the effect of the mask process. For example, when the image data is C color data, the first ink discharge is performed by the nozzle 122 of the C1, and the second time is performed by the C226.

  In this way, one type of mask processing for the image data of one color of the raster focused this time is completed, and the image data of the raster is divided by two different nozzles 122. Accordingly, the influence of each nozzle characteristic is dispersed in the raster.

  As described above, in the description based on FIG. 4, the mask processing is performed in units of one raster image data. However, the processing unit of this mask processing is changed in relation to other processing in the image processing unit 4. It doesn't matter. For example, four color rasters may be processed together for one color image data. Even in such a case, if attention is paid to one raster, the mask process is performed in the same manner as the process described with reference to FIG.

  In the mask processing described above, the mask data is read out from the head position in the right direction of the mask table 71 and used, and the number of image data included in one raster is large, and the mask data included in the row of the mask table 71 is If it is exhausted, the data in the lower row can be used sequentially. FIG. 7 is a diagram exemplifying the data use order in the mask table 71.

  The example shown in FIG. 7 is a case where the data in the lower row is used sequentially from the left end to the right end when the data for the head position row is exhausted as described above. Since it is not preferable to use the data, data is used in each area as shown in the figure. That is, in the mask process A, the mask data to be used moves to the upper left of the area A after reaching the lower right of the area A. Similarly, the mask data used in the mask process B shifts to the upper left of the area B after reaching the lower right of the area B.

  Unlike the method shown in FIG. 7, when data is exhausted for the row at the top position, it is possible to return to the left end of the row and use the order of circulation in the row, but the circulation shown in FIG. By adopting the method, in the mask process B, the appearance cycle of the same pattern of the mask data becomes long, and the effect of dispersion can be improved.

  In the above description, the mask table 71 (memory for storing the mask table 71) is divided into a predetermined area size. However, this area size, that is, the way of division does not need to be fixed, and when necessary. Alternatively, it may be possible to change to a different area size. In this case, the CPU 3 rewrites the mask table 71 at a necessary timing so that desired mask data can be stored in a desired area size. In the mask process, the CPU 3 also transmits information on the area containing the mask data used this time in response to an instruction to the mask processing unit 7 (step S3 in FIG. 4). For example, the mask data is instructed to be used in the area from the top (from the beginning) to the 80th line (row) in the entire area of the mask table 71. In response to the instruction, the mask processing unit 7 performs processing so that the mask data is used from the head position instructed in the area.

  In the above example, the case where two types of mask processing are performed has been described, but three or more types of mask processing may be performed. In this case as well, the mask table 71 stores the mask data for each type. Are divided into a plurality of areas, and mask data is used in an area corresponding to the type of processing. Further, it is not necessary to limit the area of the mask data to be used for all mask processes that can be executed by the printer 1. For example, for the mask process A, data is used only in the area A of the mask table 71, but for the mask process B, data of the entire area of the mask table 71 may be used.

  As described above, in the printer 1 according to the present embodiment, one mask table is shared for a plurality of types of mask processing using different mask data, and the different mask data is stored in the first mask table. Is stored in each divided area. In the mask process, control is performed so that the mask data is used in an area in which mask data corresponding to the mask process is stored. Accordingly, even when a plurality of types of mask processing using different mask data are performed, only one mask table 71 is required, and when the portion to be masked is hardwareized, it contributes to downsizing of the apparatus. it can.

  The use start position of the mask data in each area is determined based on the raster position and color of the data to be processed. In particular, in the area where the mask data is irregularly arranged, the raster data in the vicinity is displayed. On the other hand, the position on the mask table 71 is determined to be sufficiently separated for different colors of the same raster. Therefore, even if the amount of mask data is not large, a sufficient dispersion effect can be obtained, the mask table itself can be reduced, and further, the apparatus can be reduced in size.

  Furthermore, if the mask table 71 can be rewritten as described above and the mask data area used when instructing the mask process is also designated, different mask processes can be executed by the same apparatus. It is possible to provide a flexible and highly flexible printing apparatus.

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

1 is a configuration diagram according to an embodiment of a printing apparatus to which the present invention is applied. It is the figure which illustrated the mask table 71. FIG. 3 is a diagram schematically illustrating a nozzle row 121 provided in the head 12. It is the flowchart which illustrated the procedure of the mask process with respect to image data. It is a figure for demonstrating the mask process B. FIG. It is a figure for demonstrating the mask process A. FIG. It is the figure which illustrated the use order of the data in the mask table.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Printer, 2 I / F, 3 CPU (mask processing means, control part), 4 Image processing unit, 5 Pass control part, 6 Decompression part, 7 Mask processing part (Mask processing means, execution part), 8 Head output part , 9 local bus, 10 memory, 11 DSP, 12 heads, 71 mask table, 121 nozzle row, 122 nozzle

Claims (5)

A printing apparatus capable of executing a plurality of types of mask processing for distributing image data in one raster to a plurality of scans of a print head,
One mask table that is divided into a plurality of areas and stores a plurality of types of mask data that are data for the mask processing and have different attributes from each other in each of the areas;
And a mask processing means for executing the mask processing using the mask data within the area of the mask table in which the mask data corresponding to the type of the mask processing to be executed is stored. apparatus. In claim 1,
The mask processing means includes
Based on the type of mask processing to be executed, a control unit that determines a head position in a predetermined area of the mask table;
A printing apparatus comprising: an execution unit that reads the mask data from the determined head position and executes the mask process using the read mask data. In claim 2,
The mask table can change the size of the area and the mask data to be stored,
The control unit designates the area in which mask data to be used is stored for the execution unit when executing the mask process. In claim 2 or claim 3,
The printing apparatus according to claim 1, wherein the determination of the head position by the control unit is performed based on a raster position and a color of image data to be masked. A printing apparatus control method capable of executing a plurality of types of mask processing for dispersing image data in one raster to a plurality of scans of a print head,
The printing apparatus is provided with one mask table that is divided into a plurality of areas, and stores a plurality of types of mask data that are data for the mask processing and have different attributes in each area.
When executing the mask processing, the mask processing is executed using the mask data in the area of the mask table in which the mask data corresponding to the type of the mask processing to be executed is stored. A method for controlling a printing apparatus, comprising: controlling the printing apparatus.

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