Abstract:
A recording apparatus using a recording head having a first recording element array and a second recording element array for one color component includes a first memory configured to store a plurality of first patterns which correspond to first, second, and third gradation values and in which dot data is allocated to the first recording element array or the second recording element array, a second pattern which corresponds to fourth gradation value and in which dot data is allocated to the first recording element array, and a third pattern corresponds to fifth gradation value and in which dot data is allocated to the second recording element array, a data acquisition unit configured to acquire multi-valued data at the first, the second, the third, the fourth and the fifth gradation value, a generation unit configured to generate dot data based on the multi-valued data generated by the acquisition unit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a circuit configured to generate binary data from multi-valued data, and also to a recording apparatus including the circuit. 
     2. Description of the Related Art 
     Japanese Patent Application Laid-Open No. 10-81025 discusses a technique for receiving multi-valued data representing a gradation level from a host apparatus, and generating binary data from the multi-valued data by referring to a table of dot placement patterns. 
     A printer equipped with a full line type recording head prints check patterns for checking a preliminary discharge operation and for checking actual discharge between image regions to be recorded based on multi-valued data during a printing operation. Therefore, the printer needs to have a data generation circuit for generating not only image data for the printing operation but also a preliminary discharge pattern and a discharge check pattern. As the number of recording elements in the recording head increased, it is required that the preliminary discharge pattern and the discharge check pattern are generated more quickly. On the other hand, there is a demand for suppression of increase in a circuit size and complexity of a data processing circuit. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, a recording apparatus for performing recording based on dot data using a recording head having a first recording element array and a second recording element array for one color component includes an input unit configured to input image data from outside, a first memory configured to store a table which includes a plurality of first dot patterns which correspond to at least each of first, second, and third gradation values and in which dot data included in a plurality of pieces of dot data is allocated to the first recording element array or the second recording element array, a second dot pattern which corresponds to fourth gradation value and in which a plurality of dot data is allocated to the first recording element array, and a third dot pattern corresponds to fifth gradation value and in which a plurality of dot data is allocated to the second recording element array, a first data acquisition unit configured to acquire multi-valued image data at the first, the second, and the third gradation values based on the image data input by the input unit, a second acquisition unit configured to acquire multi-valued image data at the fourth gradation value and the fifth gradation value, a second memory configured to store pieces of data generated by the first data acquisition unit and the second data acquisition unit, a generation unit configured to generate dot data based on the multi-valued image data stored in the second memory and the table, and a transfer unit configured to transfer the dot data generated by the generation unit to a recording head. 
     Further features of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic diagram illustrating an internal configuration of a printer (a recording apparatus) according to an exemplary embodiment of the present invention. 
         FIG. 2  illustrates a layout of print heads and recording elements. 
         FIG. 3  illustrates how data is printed to a sheet. 
         FIG. 4  is a control block diagram of a recording apparatus. 
         FIG. 5  is a conceptual diagram illustrating a placement of dot patterns used for converting the density data (multi-valued image data) stored in the print buffer into dot data. 
         FIG. 6  illustrates a configuration of a data generation circuit. 
         FIGS. 7A ,  7 B, and  7 C illustrate how dot data is allocated to a nozzle array (a recording element array). 
         FIG. 8  is a flowchart illustrating an operation sequence executed by the data generation circuit. 
         FIG. 9  illustrates how data is printed to a sheet. 
         FIG. 10  illustrates how data is printed to a sheet. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Various exemplary embodiments, features, and aspects of the invention will be described in detail below with reference to the drawings. 
       FIG. 1  is a schematic diagram illustrating an internal configuration of a printer (a recording apparatus) according to a first exemplary embodiment of the present invention. The printer includes a sheet feeding unit  101 , a printing unit, and a discharging unit  102 . The sheet feeding unit  101  stores and supplies a sheet (recording medium) wound in a roll. The printing unit includes print heads  105  to  108 , and records an image on the sheet being conveyed. The printing unit also includes a plurality of conveyance rollers  103  and  104  that convey the sheet. 
     The print head is a line type print head equipped with recording elements arranged in a range to cover a maximum width of sheet assumed to be used. Each print head has four rows, that is, row A, row B, row C, and row D, of recording elements (nozzle arrays) in which a plurality of recording elements (nozzles) are aligned. More specifically, one print head for one color has four recording element arrays. 
     As illustrated in  FIG. 2 , the print heads  105  to  108  are arranged in the X-direction. In each recording element array, a plurality of recording elements is aligned in the Y-direction. In the present exemplary embodiment, four print heads are arranged in the order of K (black), C (cyan), M (magenta), and Y (yellow) from an upstream side of a sheet conveyance direction. The number of colors and the print heads is not limited to four. The print head may be formed by arranging a plurality of chips on which a plurality of the nozzle arrays is arranged in a staggered pattern. 
     In the present exemplary embodiment, a type of the recording element is a heating element. However, the recording element may be any type using, for example, a piezoelectric element, an electrostatic element, and a microelectromechanical system (MEMS) element. Ink of each color is supplied to a corresponding print head through an ink tube from an ink tank, not illustrated. The sheet discharging unit  102  includes a cutter (not illustrated), and conveys a sheet cut by the cutter. Further, the sheet discharging unit  102  sorts the printed sheets into groups and discharges the groups of sheets into a plurality of trays (not illustrated) if necessary. A control unit  109  controls operations of the printer. 
       FIG. 3  illustrates a printing operation to a sheet of paper. The printer performs preliminary discharge between images  2  and  3 , and further performs preliminary discharge or discharge for a nozzle check between images  4  and  5 . 
       FIG. 4  illustrates a control block of the recording apparatus. A host apparatus  210  specifies an image to be printed and transmits a print start command to the recording apparatus. Image data is transmitted via an interface circuit  204  and stored in a reception buffer in a random access memory (RAM)  203 . 
     The image data in this case is red-green-blue (RGB) luminance data which has resolution of 600 dpi (X-direction)×600 dpi (Y-direction) and is represented by 8 bits (256 gradations) for each pixel. When the image data of a predetermined amount is stored in the RAM  203 , the image processing circuit  216  starts to operate, converts the RGB image data into multi-valued density data corresponding to color components (such as cyan (C), magenta (M), yellow (Y), and black (K)), and stores the density data in a print buffer in the RAM  203 . 
     As described above, the image processing circuit  216  generates density data (multi-valued data). The density data is 4-bit data that can be processed by a data generation circuit  213 . Maintenance patterns (a preliminary discharge pattern, a nozzle check pattern), which are described below, are transmitted from the host apparatus and processed in a manner similar to the image data, and stored in the print buffer. 
     In addition to inputting from an external apparatus, such as the host apparatus, the maintenance patterns may be stored in a read-only memory (ROM)  201  and processed by the print data generation circuit (print data generation unit)  213  or the image processing circuit  216  to generate density data in response to an instruction from an operation unit of the recording apparatus or a command from a control program of a printing operation. The generated density data may be stored in the print buffer. 
       FIG. 5  is a conceptual diagram illustrating a placement of dot patterns used for converting the density data stored in the print buffer into dot data. When the density data of a predetermined amount is stored in the print buffer, the print data generation unit  213  generates binary data (dot data) from the density data. The data generation operation is synchronized with a conveyance operation of a sheet. The print data generation unit  213  stores the dot data in an intermediate buffer (a transfer buffer, a second buffer)  214 . A transfer unit reads the dot data stored in the intermediate buffer, and transfers the dot data to a recording head. The recording head is driven by a signal from a head drive unit and discharges ink. 
       FIG. 6  illustrated a configuration of the print data generation unit  213 . As illustrated in  FIG. 5 , a direct memory access (DMA) controller  602  reads density data from a print buffer  601  in the RAM  203 , and transfers the density data to a pattern selection unit  604 . The pattern selection unit  604  selects dot patterns from a table  605  based on position information from a position information generation unit  603 . The table  605  has 8 dot patterns (pat 0  to pat 7 ) at each gradation level for 8 gradations (8-step density levels from level  0  (value  0 ) to level  7  (value  7 )) of multi-valued data. A first range (area) is defined between value  0  to value  7  of the multi-valued data. 
     Therefore, by referring to the table, a dot pattern of 1200 dpi (X-direction)×1200 dpi (Y-direction) can be obtained from a piece of multi-valued data. In other words, four dot patterns are generated from a piece of density data (multi-valued data). The pattern selection unit  604  can obtain different patterns (binary data placements) even from data at the same gradation. The pattern is formed by binary data (dot data) allocated to the row A to the row D. 
     For example, in  FIG. 6 , one black dot is allocated to each of the row A, the row B, and the row D, and no dot is allocated to the row C. The black dot indicates a pixel to be recorded by a recording element. A pixel without the black dot indicates the pixel not recorded by the recording element. 
       FIG. 7A  illustrates of allocation of dots to nozzle arrays taking gradation levels (level  0  to level  7 ) of the multi-valued data for example. For example, in a level  1 , each pattern is for recording one dot by four nozzle arrays. In a level  2 , each pattern is for recording two dots by four nozzle arrays. 
     In  FIG. 7B , predetermined patterns are provided for density data corresponding to a level  8  (value  8 ) to a level  11  (value  11 ). A second range (area) in table 605  ( FIG. 6 ) is defined between value  8  to value  11  of the density data. The values  8  to  11  of the density data is not related to density levels, and are treated as information for specifying a recording element array to be allocated. 
     For example, in  FIG. 7B , in the level  8 , dots are allocated to the row A (null data is allocated to the other nozzle arrays). In the level  9 , dots are allocated to the row B (null data is allocated to the other nozzle arrays). Similarly, in the level  10 , dots are allocated to the row C, and in the level  11 , dots are allocated to the row D. 
       FIG. 8  is a flowchart illustrating a sequence executed when the print data generation unit  213  generates dot data. In step S 1 , when a sheet is conveyed, an encoder mounted to a conveyance unit generates a pulse signal synchronized with the conveyance. When the sheet is conveyed to a predetermined position (YES in step S 1 ), then in step S 2 , a predetermined amount of density data (multi-valued data) is read from the print buffer. 
     In step S 3 , it is determined whether a value of the read density data is within the first range (area). If the density data is within the first range (YES in step S 3 ), in step S 4 , position information is obtained. Then in step S 5 , a dot placement pattern is obtained based on the position information and the value of density data. 
     On the other hand, if the density data is in the second range (area) (NO in step S 3 ), then in step S 6 , a pattern of nozzle arrays corresponding to the value of density data is obtained. 
     Then in step S 7 , binary data (dot data) corresponding to the obtained pattern is stored in the intermediate buffer. In this case, as for processing to different column positions, if a raster position (X-position) is the same, it is only necessary to perform processing to store the same data. 
     As described above, if the density data is in the second range (area), the dot data is allocated selectively to each recording element array. The intermediate buffer has a buffer corresponding to each nozzle array, and the print data generation unit  213  stores the binary data to each buffer. 
       FIG. 9  illustrates a correspondence relation among an area to be recorded on a sheet, an address area where multi-valued data corresponding to the record area is stored in the print buffer, and a position of dot data generated according to density data. 
       FIG. 9  also illustrates how an image  1 , an image  2 , a nozzle check pattern, and an image  3  are recorded in sequence on a sheet. In recording of the nozzle check pattern, a row-A check pattern, a row-B check pattern, a row-C check pattern, and a row-D check pattern are recorded in this order. For example, the print buffer stores density data of value  8  for the row-A check pattern, and multi-valued data of value  9  for the row-B check pattern. 
     In the first exemplary embodiment described above, a second area pattern in the table illustrated in  FIG. 6  is not limited to the patterns illustrated in  FIG. 7B , and may be a pattern for preliminary discharge illustrated in  FIG. 7C . 
     In the patterns in  FIG. 7C , in the case of density data in a level  8 , predetermined patterns are allocated to two recording element arrays (row A and row B). In the case of density data in a level  9 , predetermined patterns are allocated to two recording element arrays (row C and row D).  FIG. 10  illustrates an example using patterns in  FIG. 7C .  FIG. 10  is similar to  FIG. 9 . 
     In the sequence in which the print data generation unit  213  generates dot data as described referring to  FIG. 8 , when the value of the read density data is determined, a dot placement pattern maybe obtained based on position information and the value of the density data without determining the range (area) of the density data. 
     The values used in description of the present invention are not limited to those described in the first exemplary embodiment. The number of the recording element arrays in the recording head is not limited to four, and at least two or more recording element arrays may be used. 
     In addition, the number of bits of multi-valued data or the number of gradations are not limited. For example, gradation values of the density data has only to be at least three values ( 0 ,  1 , and  2 , for example). In this case, if the recording head includes two recording element arrays, as for the gradation values of nozzle check patterns, the gradation value corresponding to the first recording element array may be three, and the gradation value corresponding to the second recording element array may be four. 
     Moreover, there are no limitations to a size of a dot pattern and resolution of data. The resolution may be 300 dpi or 2400 dpi, for example. The table may include an area corresponding to a check pattern and a pattern for preliminary discharge, and may also include other patterns. Further, the patterns in  FIGS. 7B and 7C  may be set in the second range by determining a level. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions. 
     This application claims priority from Japanese Patent Application No. 2010-118543 filed May 24, 2010, which is hereby incorporated by reference herein in its entirety.