JP2006110795A - Image forming apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate irregular color due to difference in ink color impact order between going path scanning and returning path scanning. <P>SOLUTION: At first, writing data for a going path or writing data for a returning path being used for recording in the going path or the returning path of a recording head in the scanning direction is generated from inputted image data and stored in units of band. Subsequently, the scanning direction of the recording head and the writing data stored in units of band are detected, and an image is formed by selecting the writing data suitable for the scanning direction of the detected recording head. Since image recording suitable for the going path and returning path can be realized, irregular color due to difference in ink color impact order between the going path and returning path can be eliminated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that records a color image by discharging a plurality of colors of ink from a recording head having a plurality of discharge ports, and a control method therefor.

  For example, as information output devices in word processors, personal computers, facsimiles, and the like, recording devices that record information such as desired characters and images on a sheet-like recording medium such as paper or film are widely used.

  This recording apparatus is configured to record an image composed of a dot pattern on a recording material based on image information. Depending on the recording method, an ink jet type, a wire dot type, a thermal type, a laser type are used. The ink jet type is configured to eject ink droplets from a discharge port of a recording head and attach them to a recording material for recording. The ink jet method has been attracting particular attention in recent years because it can be non-contact recording on a recording medium such as paper, is easy to color, and is quiet, and its configuration is desirable. General in terms of low cost and easy miniaturization of serial recording systems that mount recording heads that eject ink according to recording information and perform recording while reciprocating scanning in the direction perpendicular to the feeding direction of recording media such as paper Widely used.

  In general, an ink jet recording apparatus includes a carriage on which recording means (recording head) and an ink tank are mounted, a transport means for transporting recording paper, and a control means for controlling them. Then, the recording head that discharges ink droplets from a plurality of ejection openings is serially scanned in the recording paper transport direction (sub-scanning direction) and the direction orthogonal to the main scanning direction (main scanning direction). Is intermittently conveyed. Further, in the case of a color inkjet recording apparatus, a color image is formed by superimposing ink droplets ejected by a recording head of a plurality of colors.

  This recording method is to record characters and figures by ejecting ink from the ejection port onto the recording medium as minute droplets according to the recording signal, and is non-impact so that there is less noise, Copiers used in combination with computers and word processors, or used alone because of the advantages such as low running cost, ease of miniaturization of the device, and easy colorization. It is widely used as an image forming means in recording apparatuses such as printers and facsimiles.

  A conventional serial ink jet recording apparatus is shown in FIG. In the figure, recording heads 1K, 1C, 1M, and 1Y are devices that have a plurality of nozzle rows and perform image recording by forming dots on a recording medium by ejecting ink droplets. Different color inks are ejected from different recording heads, and a color image is formed on the recording medium by mixing these ink droplets. The recording head arrays 1K (black), 1C (cyan), 1M (magenta), and 1Y (yellow) are mounted on the carriage 201, and ink is ejected in this order during one scan. For example, when making red (hereinafter referred to as R), magenta (hereinafter referred to as M) is first landed on the recording medium, and then yellow (hereinafter referred to as Y) is landed on the M dots so as to appear as red dots. In the same manner, in the case of green (hereinafter referred to as G), colors are formed in the order of C and Y, and in the case of blue (hereinafter referred to as B), colors are formed in the order of C and M, respectively. However, since the recording heads 1K, 1C, 1M, and 1Y are arranged at regular intervals (P1), for example, when printing G solid, printing of Y is performed with a delay of 2 * P1 after printing C. . That is, the Y solid is printed on the C solid. The carriage 201 moves on the sliding shaft by the power from the carriage drive motor 8 being transmitted by the belts 6 and 7. During this operation in the main scanning direction, printing in the digit (sub-scanning) direction is performed.

  The initial position of the carriage 201 is referred to as a home position (hereinafter referred to as HP). Normally, printing is performed by moving the carriage from this HP, and in this example, printing is performed from left to right in FIG. For feeding in the sub-scanning direction, the recording medium is fed by a paper feed motor (not shown). The direction C in the figure is the paper feed direction. Ink is supplied from the ink cassettes 10K, 10C, 10M, and 10Y to the recording heads 1Y, 1M, 1C, and 1K on the carriage by the supply tube row 9 for each color.

  FIG. 3 is a schematic diagram illustrating an example of a state in which an ejection port (hereinafter also referred to as a nozzle) provided in the recording head 1Y is viewed from the bottom z direction of the schematic diagram of FIG. In the drawing, # 1, # 2,..., # 1280 are 1280 nozzles arranged at a pixel density (1200 dpi) forming 1200 pixels per inch on each recording head. The recording heads 1M, 1C, and 1K have the same structure.

  The carriage 201 at the home position HP before the start of recording is arranged at a pixel density that forms 1200 pixels per inch of the recording head while moving in the x direction (main scanning direction) when a recording start command is issued. Recording with a width of 1280/1200 inches is performed on the paper surface by 1280 nozzles. When the recording to the edge of the sheet is completed, the carriage returns to the home position HP, and again moves for recording in the x direction (main scanning direction). Between the end of the first recording operation and the start of the second recording operation, a paper feed roller (not shown) rotates in the direction of the arrow, thereby 1280/1200 inches in the y direction (sub-scanning, direction C in FIG. 1). Feed the paper. In this way, by repeatedly performing 1280/1200 inch recording and paper feeding by the recording head for each main scan of the carriage 201, for example, a recorded image for one page can be completed. A recording mode in which one scanning recording area is sequentially formed by one scanning of the recording head in this way is hereinafter referred to as a one-pass recording mode. This one-pass recording mode is optimal when recording characters and graphic images at high speed.

  FIG. 4 is a schematic view when the carriage 201 is viewed from above the printer, and the recording heads 1Y, 1M, 1C, and 1K are sequentially arranged.

  In general, the color ink jet recording method realizes color recording using four color inks of black (K) added to three color inks of cyan (C), magenta (M), and yellow (Y). To do. In such a color ink jet recording apparatus, unlike a monochrome ink jet recording apparatus that prints only characters, various elements such as color development, gradation, and uniformity are required for recording a color image. It becomes.

  In addition, in the ink jet recording apparatus, in addition to the conventional four colors of cyan (C), magenta (M), yellow (Y), and black (K) in order to form a natural image with higher gradations and higher quality, Using 7-color ink with 3 colors of light C (LC), light M (LM), and light Y (LY) with low ink density, many of them have reduced graininess in highlight areas. Has been.

  However, the quality of the recorded image largely depends on the performance of the recording head alone. Slight differences in each nozzle that occur during the printhead manufacturing process, such as the shape of the printhead discharge ports and variations in the electrical / thermal converter (discharge heater), affect the amount of ink discharged and the direction of the discharge direction. As a result, the image quality deteriorates as density unevenness of the finally formed recorded image. As a result, there is a “white” portion that cannot periodically satisfy the area factor of 100% in the head main scanning direction, or conversely, dots overlap more than necessary or white streaks occur. It will be. These phenomena are usually perceived as uneven density by the human eye.

  Therefore, a multipass printing method has already been devised as a countermeasure against these uneven density, in which all pixels to be recorded in the same recording scan are divided into a plurality of groups and the same recording area is recorded little by little by a plurality of recording scans. Yes. (For example, refer to Patent Document 1.) By performing such multi-pass printing, all the recording pixels in the image area that can be recorded by one recording scan are displayed with dots of different colors in the forward printing and the backward printing. Since the recording is performed while weaving, the above-described adverse effects due to the order of color printing are eliminated. There is also an effect of recording while drying the ink little by little.

  However, recently, there has been a demand for higher-speed recording and higher image quality, and in the method of recording by simply dividing a plurality of times by multipass as described above, the time cost for recording is more than doubled. As such, this situation is not very favorable.

  In recent years, inks with little ink bleeding and media with good absorption have been developed one after another. Against this backdrop, the multi-pass printing method, which produced various effects at the expense of enormous time cost, now has a lot of time loss because it is going to be done only for printing unevenness, and round trips. Therefore, a high-speed printing method that performs a single scan is desired.

  The bi-directional printing method is becoming widespread because conventional two-scan printing can be performed by one reciprocation of the recording head. Before starting printing, when the carriage 201 at the home position receives a printing start command, the carriage 201 moves in the x-direction and moves by a width D (= 1280/1200 inch) on the paper surface by 1280 multi-nozzles on the recording head. Record. In this recording, the heating elements in the ink discharge nozzles are driven based on the recording signal in accordance with the read timing of the encoder, and ink droplets are discharged and adhered onto the recording material in the order of black K, cyan C, and magenta M. Is forming an image. When the data is completed up to the edge of the paper, printing is performed while moving in the -x direction (reverse scanning direction). The paper feed roller (not shown) rotates in the y direction by the width D from the end of the first print to the start of the second print. In this way, by repeatedly feeding the paper in the y direction by the recording head width D every time the carriage 201 is scanned, data printing on one sheet is completed.

  However, when printing is performed in both directions, the recording head is fixed in the recording scanning direction as shown in FIG. 4, so the order in which ink is printed in the forward path and the order in which ink is recorded in the backward path are Reverse. Therefore, the color of dots recorded in the forward path and the color of dots recorded in the backward path are different.

  For example, when forming a green (cyan + yellow) image in a certain area, if ink is applied in the order of cyan and yellow to each pixel, cyan absorbed first becomes the priority color, and cyan color A green image with a strong taste. However, on the contrary, when ink is printed in the order of yellow and cyan, a green image with a strong yellow tint can be obtained.

  In such a state, if paper feeding is performed by the head width D for each recording scan, two different types of color and density appear alternately for each head width, resulting in large unevenness as a whole. It had deteriorated.

  Patent Document 3 discloses a configuration in which parameters for converting an image signal into a drive signal for a recording head can be changed for the purpose of suppressing changes in color and density in such bidirectional recording. Yes.

  As a color ink jet recording apparatus, there is a so-called page printer that analyzes information including color multi-value information of a page description language method in units of pages and prints out in units of pages.

  With the advent of inexpensive personal computers recently, an environment has been set up that allows easy handling of full-color characters, graphics, and image data. As a result, color information is used in a wide range of fields such as documents using color, art, and design.

  When recording print data created by an application using such color information on the printing device, use the processing function of the host computer, and adjust the characters, images, and graphics on the host computer side to the resolution of the recording device. There is a so-called dumb printer or video printer in which the image is developed and then sent to a printing apparatus. This processing method is characterized in that the mechanism on the printer side is simplified and many processes are executed on the host computer side. However, when color information is handled, there is a problem that a large amount of data takes a lot of time for communication, and the throughput may be very low.

  On the other hand, a page description language (abbreviation of Page DesCription Language, hereinafter abbreviated as PDL) is sent from the host computer as characters, graphics, and images as languages, the PDL language is interpreted by the printing device, and various information is stored in the raster memory. There is also a processing method for generating a page image by performing scan conversion (scan conversion). In such a printer using the PDL language, print data for one page may be divided into a plurality of bands to save a memory, and bitmap development is performed for each band.

  The print data used in such a printing apparatus is composed of a plurality of objects with one graphic as one object. These objects are mainly fonts, bitmaps, etc., and are classified according to the difference in their development (hereinafter referred to as rendering) processing methods.

  Some have hardware rendering means for rendering at high speed. In this case, the PDL language received from the host computer is interpreted for each band, converted into an intermediate code (hereinafter referred to as a display list) for input to the hardware rendering means, developed by high-speed rendering hardware, and printed. It becomes the procedure of doing. Here, some advanced development processing that could not be supported by the hardware rendering means includes means for switching the display list to be rendered by software rendering (for example, see Patent Document 2).

  8 and 9 are block diagrams showing schematic configurations of the controller unit and the engine unit of the color PDL inkjet recording apparatus, respectively. First, the function and schematic operation of the controller unit will be described with reference to FIG.

  The CPU 2601 is connected to the host PC 2611 (or 2612) via the USB interface 2609 or the IEEE 1394 interface 2610. The RAM 2604 for storing command signals and image information received from the host PC 2611 (or 2612) is accessed, and the recording operation is controlled based on the information stored in these memories.

  Instruction information input from the keys of the operation panel 2614 is transmitted to the CPU 2601 via the operation panel interface 2613, and the LED lighting and the LCD display of the operation panel 2614 are similarly controlled via the operation panel interface 2613 according to commands from the CPU 2601. Is done. An expansion interface 2615 is an interface for performing function expansion by connecting an expansion card such as a LAN controller or an HDD. The data processing block 2616 interprets the PDL data received from the host PC, performs drawing processing, and further converts into image forming data of each ink color that conforms to the engine specifications, and then passes the engine (not (Shown). Similarly, various commands and status information are transmitted and received between the controller and the engine via the engine communication block 2618. A detailed data processing flow in the data processing block 2616 will be described later.

  Next, the function and operation outline of the printer engine unit will be described with reference to FIG. The printer engine unit is connected to a controller (not shown) via a band memory control block 2712. The CPU 2701 accesses a ROM 2703 that stores control programs, an EEPROM 2704 that stores updatable control programs and processing programs, various constant data, and a RAM 2702 that stores command signals and image information received from a controller (not shown). The recording operation is controlled based on the information stored in these memories. The carriage 2711 is moved by operating the carriage motor 1709 via the output port 2705 and the carriage motor control circuit 2707, and the paper feed paper feed motor 2708 is operated via the output port 2705 and the paper feed motor control circuit 2706. As a result, the paper transport mechanism 2710 such as a transport roller is operated. Further, the CPU 2701 can record a desired image on the recording medium by controlling the band memory control block 2712 and the recording head control block 2714 based on various information stored in the RAM 2702 and driving the recording head 2715. .

  Also, from a power supply circuit (not shown), a logic drive voltage VCC (for example, 3.3V) for operating the CPU and various control circuits, various motor drive voltages VM (for example, 24V), and a heat voltage for driving the recording head. Vh (for example, 12V) is output.

  Next, the data flow in the controller will be described in detail.

  There are two main methods for drawing PDL data. One is a method called contone rendering, in which rendering processing is executed with RGB multi-value data (in many cases, 8 bits for each color), and the output data format is also RGB multi-value data. The other is a method called halftone rendering, in which RGB multi-value data is added to the desired color ink of cyan (C), magenta (M), yellow (Y) and black (K). A display list converted into a color space is generated, and halftone processing is performed prior to rendering processing. The output data format of the halftone rendering method is KCMY data subjected to gradation conversion. It is also possible to perform halftone processing before the display list.

  In the former contone rendering method, KCMY conversion and halftone processing are performed on the raster image after rendering processing, and thus there is an advantage that the degree of freedom of the image processing configuration and flow is high. On the other hand, since the latter halftone rendering method performs color space conversion and halftone processing during display list generation or rendering processing, it has the advantage that various buffers can be configured with a smaller size than the contone rendering method. .

  FIG. 10 shows the flow of data processing in the controller. Here, the halftone rendering method is described.

  Various PDL data including RGB multi-value information received from the host computer 901 is input to the input buffer 904, and translation processing is performed. Subsequently, the intermediate code generation unit 905 converts the data into intermediate data (display list) for high-speed rendering processing. Here, conversion processing from the RGB color space to the KCMY color space is performed by the profile 906, and the generated display list is configured in a form corresponding to each KCMY plane and stored in the intermediate code memory 907. The renderer 908 realizes a conversion process to a raster image according to the display list generated and held. This rendering process is executed for each band having a smaller number of lines than one page.

In general, the drawing efficiency (processing speed) is increased by setting the band size large, but on the other hand, it requires a large amount of memory resources, which is a high cost factor. In addition, the renderer 908 performs gradation conversion by a multi-value dither method in parallel with the rendering process, and outputs a raster image of 4 bits of each KCMY color to the band memory 909. The dot data generating means 910 converts the KCMY color 4-bit data read from the band memory 909 into KCMY color 1-bit data of the image formation resolution (output resolution) using a halftone dot matrix. For example, dot data having an output resolution of 1200 dpi × 1200 dpi is generated using a 2 × 2 dot matrix for a rendering resolution of 600 dpi × 600 dpi. The rendering resolution and output resolution are determined according to the purpose (printing mode).
U.S. Pat. No. 4,748,453 Japanese Patent Application Laid-Open No. 07-137353 Japanese Patent Laid-Open No. 04-119856

  In color ink jet recording apparatuses, there is an increasing demand for higher speed as well as higher image quality.

  The main means for realizing high speed are (1) increase in the number of nozzles provided in the recording head, (2) improvement in carriage driving (main scanning) speed on which the recording head is mounted, and (3) recording in multi-pass recording. Reduction of the number of passes, (4) Implementation of bidirectional recording in which image formation is performed for both forward scanning and backward scanning.

  In realizing high speed, not only (1) and (2), but also (3) and (4), reduction in characteristic variation and improvement in yield due to enlargement of the recording head and high density mounting of the nozzles, Alternatively, there is a large part depending on the performance of the recording head itself, such as further improvement in basic performance such as high-speed response and reduction in deflection.

  However, by improving the nozzle manufacturing technology, even if the ink discharge amount and the ink discharge direction associated with the increase in the size of the recording head and the high density mounting of the nozzles are made constant, both (3) and (4) can be achieved. For this purpose, the following very large problems occur.

  That is, a small pass such as one-pass printing (recording an image of a predetermined area by one scan of the recording head) and 2,4-pass printing (recording an image of a predetermined area by two or four scans of the recording head) When multi-pass printing is performed by so-called bi-directional printing, in which image formation is performed for both forward scanning and backward scanning, periodic color unevenness occurs for each paper feed amount width and the image quality is greatly degraded. appear. The mechanism of this phenomenon will be described in detail below.

  2. Description of the Related Art A recording head in a recent ink jet recording apparatus has a mainstream configuration in which nozzle rows are arranged in the sub-scanning direction for each ink color and are arranged in the main scanning direction, for example, for the ink color. FIG. 3 shows the state of nozzle arrangement for each ink color. As shown in the figure, 1280 nozzles are mounted per row (color), and are arranged in the main scanning direction in the order of K, C, M, and Y as shown in FIG. When bidirectional recording is performed with such a recording head, as is apparent from FIG. 4, the ejected ink droplets land on the paper surface in the order of K, C, M, and Y in the forward scanning, and conversely in the backward scanning, Y , M, C, K, the ejected ink droplets land on the paper surface.

  FIG. 11A is a schematic cross-sectional view showing the state of ink permeation and fixing with respect to the recording paper when the M ink droplet arrives on the paper surface at a short time interval following the C ink droplet in forward scanning. It is. In general, ink droplets that are ejected later penetrate in the direction perpendicular to the paper surface and in the direction along the paper surface, but do not penetrate and fix so much in the region where the ink droplets that have landed earlier have penetrated. The ink droplets that are ejected later penetrate and fix further below the region where the ink droplets that have been impregnated earlier penetrate. That is, C permeates first and spreads on the surface and inside, and the next M that has landed enters under the C ink. When viewed from the surface, the M ink spreads outside the C ink with M.

  FIG. 11B is a schematic cross-sectional view showing the state of ink permeation and fixing with respect to the recording paper when the C ink droplet arrives on the paper surface after a short time interval following the M ink droplet in the backward scan. It is. Similarly, first, M permeates and spreads on the surface and inside, and then the landed C enters under the M ink. When viewed from the surface, the C ink spreads outside the M ink with C. When attention is paid to a single dot, the color of C appears stronger than the CM mixed color portion in forward scanning. In this way, even in the same C-M color mixture, the forward scanning and the backward scanning have completely different colors.

  The present invention has been made starting from solving the above-described problems of the prior art, and its purpose is to achieve a color difference due to a difference in the ink color landing order between the forward scan and the backward scan of the recording head. It is an object to provide an image forming apparatus capable of efficiently suppressing color unevenness for each paper conveyance width during bidirectional recording and causing high-speed and high-quality image formation, and a control method therefor.

  In order to achieve the above object, an image forming apparatus according to an embodiment of the present invention has the following arrangement. That is, a plurality of recording heads corresponding to different color inks are arranged along the main scanning direction, and ink is ejected from the plurality of recording heads while the plurality of recording heads are reciprocally scanned along the main scanning direction. An image forming apparatus for forming a color image on a recording medium by performing image processing on the image data in units of image data corresponding to a predetermined area on the recording medium, The same for the forward profile used for image processing when performing image formation in scanning in the forward direction of a plurality of recording heads, and for the backward profile used for image processing when performing image formation in scanning in the backward direction Image processing means for performing image processing on image data corresponding to the predetermined area, and image processing by the image processing means A memory for storing the image data, forward data after being processed according to the forward profile stored in the memory, and return data after being processed according to the return profile, Selecting means for selecting each time the predetermined area is recorded in correspondence with the scanning direction of the plurality of recording heads.

  Here, for example, the outward profile and the backward profile are preferably profiles used for image processing to match the colors of the image recorded during the forward scan and the image recorded during the backward scan.

  Here, for example, the image data is preferably data described in a page description language.

  Here, for example, the image processing unit further includes an intermediate code generation unit that generates an intermediate code according to the image data described in a page description language, and a rendering unit that expands the intermediate code into data to be recorded. Preferably, the image data is processed in the generation of the intermediate code.

  Here, for example, in the memory, data obtained by developing the intermediate code for forward scanning processed according to the outward profile, and data obtained by developing the intermediate code for backward scanning processed according to the backward profile It is preferable that the selection means selects either the forward scan data or the backward scan data after being developed in correspondence with the recording of the predetermined area.

  Here, for example, the memory stores the intermediate code for forward scanning processed according to the outward profile and the intermediate code for backward scanning processed according to the backward profile, and the selection means includes: The intermediate code for forward scanning and the intermediate code for backward scanning are selected in correspondence with the recording of the predetermined area, and the selected intermediate code is developed by the rendering means for recording. It is preferable.

  Here, for example, it is preferable that the predetermined area is an area recorded by one scan of the plurality of recording heads in the main scanning direction.

  Here, for example, it further has detection means for detecting whether the scanning direction of the plurality of recording heads is the forward direction or the backward direction when recording an image, and the selection means is detected by the detection means. It is preferable to make a selection according to the results.

  In order to achieve the above object, a control method of an image forming apparatus according to an embodiment of the present invention has the following configuration. That is, a plurality of recording heads corresponding to different color inks are arranged along the main scanning direction, and ink is ejected from the plurality of recording heads while the plurality of recording heads are reciprocally scanned along the main scanning direction. A method for controlling an image forming apparatus for forming a color image on a recording medium by performing image processing on the image data in units of image data corresponding to a predetermined area on the recording medium. Thus, the forward path profile used for image processing when image formation is performed in scanning in the forward direction of the plurality of recording heads, and the backward profile used for image processing when image formation is performed in scanning in the backward direction. An image processing step of performing image processing on image data corresponding to the same predetermined area, and image processing by the image processing step A storing step of storing the image data after being processed in a memory; data for the forward path after being processed according to the profile for the forward path stored in the memory; and for the return path after being processed according to the profile for the return path A selection step of selecting any of the data every time the predetermined area is recorded in correspondence with the scanning direction of the plurality of recording heads.

  According to the present invention, the color unevenness for each paper transport width during bidirectional printing caused by the difference in the color tone due to the difference in ink color landing order between the forward scan and the backward scan of the recording head is detected between the forward scan and the backward scan. Provided is an image forming apparatus and a control method therefor that can efficiently control high-speed and high-quality image formation by generating drawing data that can form optimum images using different color conversion profiles. be able to.

  Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  In the embodiments described below, a printer is taken as an example of a recording apparatus using an inkjet recording method.

  In this specification, “image formation” (sometimes referred to as “recording”, “drawing”, and “printing”) is not only for forming significant information such as characters and figures, but also for human beings regardless of significance. Regardless of whether or not the image is manifested so that it can be perceived visually, a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or the medium is processed is also shown.

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, etc. that can accept ink. Shall.

  Furthermore, “ink” (sometimes referred to as “liquid”) is to be interpreted broadly in the same way as the definition of “image formation (recording, drawing)”, and when applied to a recording medium, A liquid that can be used for formation of an image, a pattern, a pattern, or the like, processing of a recording medium, or ink processing (for example, solidification or insolubilization of a colorant in ink applied to the recording medium).

<First Embodiment>
In order to improve the image recording speed, when recording is performed using both the forward and backward paths in the scanning direction, as described above, the ink landing order due to the arrangement of the recording heads as shown in FIG. Inevitable color unevenness due to differences could not be avoided. The reason why this color unevenness cannot be avoided is that the drawing data created by using the controller unit shown in FIG. 10 is used without distinguishing between the forward path and the backward path in the scanning direction. Therefore, in the present embodiment, in order to avoid this color unevenness, an image forming apparatus having a controller unit that can generate drawing data capable of recording optimum images in the forward path and the backward path as shown in FIG. 1 is used. It was. The images formed in the forward and backward passes of the recording head using the drawing data created in FIG. 1 are subjected to image processing corresponding to the arrangement of the recording heads so that an optimum image is formed in each scanning direction. Generated using parameters. Therefore, even if the image created in the present embodiment is recorded on the recording medium sequentially in units of bands alternately with the forward path and the backward path, the conventional color unevenness does not occur. The image forming apparatus is capable of forming an image that does not cause color unevenness even when performing one-pass printing and multi-pass printing using the forward pass.

[Configuration of Recording Unit: FIG. 7]
FIG. 7 shows a configuration of a recording unit of the ink jet recording apparatus according to the present invention. Reference numeral 701 denotes a recording head, and ink tanks containing four color inks of black (K), cyan (C), magenta (M), and yellow (Y), respectively, and four independent ink tanks corresponding to the respective ink tanks. It is composed of a multi-head composed of two heads (FIG. 4). The number of nozzles for each color is 1280 nozzles. A carriage 702 supports the recording head 701 and moves them together with recording. The carriage 702 is at the home position HP shown in the drawing during standby such as a non-recording state. Reference numeral 703 denotes a paper feed roller that rotates while holding the recording paper 705 together with an auxiliary roller (not shown), and feeds the recording paper 705 in the Y direction as needed. Reference numeral 704 denotes a paper feed roller that feeds the recording paper 705 and plays a role of suppressing the recording paper 705 in the same manner as the paper feed roller 703 and the auxiliary roller. Here, the recording head 701 has 1280 nozzles arranged in the paper feed direction for each of the four colors K, C, M, and Y (FIG. 3).

  A basic bidirectional recording operation in the above configuration will be described. During the standby, the carriage 702 at the home position HP is moved in the X direction by a recording start command, and performs recording by ejecting ink onto the recording paper 705 according to the recording data by a plurality of nozzles of the recording head 701. When the recording of the recording data to the end of the recording paper 705 is completed, the paper feed roller 704 rotates in the direction of the arrow to feed the paper by a predetermined width in the Y direction, and then the carriage 702 moves in the −X direction while moving the ink. Recording is performed by discharging, and the carriage returns to the original home position HP. Data recording is realized by repeating such scanning operation and paper feeding operation.

  Note that the ink jet recording apparatus is a controller (FIG. 5) that includes an interface for exchanging image information and various control information with a host computer and the like, and a data processing block that generates image formation data based on PDL data. 8) and an engine (FIG. 9) that transports the recording paper and drives the carriage and controls the recording head to form an image.

[Data processing flow: Fig. 1]
Next, the flow of data processing will be described with reference to FIG. In FIG. 1, reference numeral 301 denotes a host that creates color information as a color application, converts color data corresponding to the color information into a PDL language format, and sends the converted PDL language data to the printing apparatus controller 302 of the printing apparatus. It is a computer. Here, PDL language data flows between the host computer 301 and the controller 302.

  There is no problem with the communication form of this PDL language data, such as serial, network, bus connection, etc., but a high-speed communication path is desirable in terms of performance. The PDL language data sent to the controller 302 is temporarily stored in the input buffer (data input buffer) 304. Intermediate code generation means 305 and 306 of the controller read and interpret the PDL language data in the input buffer, and generate an intermediate code (display list). Here, the intermediate code generation unit 305 generates an intermediate code for the forward path by using the profile A307 that performs image processing suitable for the print head arrangement K-> C-> M-> Y when the recording head moves in the forward direction. And stored in the intermediate code memory 309.

  Similarly, the intermediate code generation unit 306 outputs the intermediate code for the backward path to the print head arrangement Y-> M-> C-> K when moving in the backward direction (discharges ink in the order of Y, M, C, K). Is created using a profile B 308 that performs image processing suitable for the image processing, and is stored in the intermediate code memory 310.

  The image processing performed by the intermediate code generation means is normally used for the ink processing of the printer from the RGB (additive color mixing) RGB (additive color mixture) of the monitor color system used in the host computer to the yellow, magenta, cyan, black. Is converted to YMCK (subtractive color mixture). The parameters of the image processing are adjusted to the optimum values for the print head arrangement.

  The image processing parameters suitable for each scanning in the forward direction and the backward direction are pre-created at the design stage so that the color and density of the pattern recorded in each scanning in the forward direction and the backward direction match. It is. As the image processing parameters, parameters used for processing such as generally known color conversion processing and gamma conversion processing are applied.

  An example of a method for creating image processing parameters is to record a plurality of patterns with different parameter values and set appropriate parameters at the design stage. A configuration in which the setting can be arbitrarily changed by the user in response to a change with time, or a configuration in which the setting can be changed depending on the number of services for maintenance work may be adopted. In this embodiment, the image processing parameters are stored in the apparatus. For example, the parameters stored in the host computer are transferred from the host computer to the printer when the printer is started. It may be configured to store in the printer. According to this configuration, it is possible to update the image processing parameter in accordance with the update of the printer driver.

  The renderers 311 and 312 perform color rendering processing with ASIC (application specific IC) hardware, perform rendering processing in real time in synchronization with video transfer to the printer engine 303, and perform banding with a small memory capacity. The process is realized.

  The band memories 313 and 314 are areas for storing images developed in the PDL language. In order to perform the banding process described above, the mechanism that can control the movement of the recording head, such as an inkjet printer, A minimum of two-band memory is sufficient.

  The renderers 311 and 312 may be realized by software instead of hardware for cost reduction. In FIG. 1, the renderer 311 interprets the intermediate code stored in the intermediate code memory 309 and develops it in the band memory 313. Similarly, the renderer 312 interprets the intermediate code stored in the intermediate code memory 310 and develops it in the band memory 314.

  In this way, bitmap data corresponding to forward direction printing of the same print area and bitmap data corresponding to backward direction printing are prepared from the PDL language data.

  Here, if the renderers 311 and 312 are operated in synchronization with the processing time of one scan of the recording head, the band memory width need only be the width of one scanning of the recording head. The band memories 313 and 314 may have a width of 640 lines when rendering at 600 dpi when, for example, a printing head having 1280 nozzles (1200 dpi) for each color is mounted to perform one-pass bidirectional printing.

  The head direction detection means 318 detects the current position of the recording head of the printer engine 303 with an encoder, a sensor, or the like, and determines the print direction of the next band together with the detection result of the 0 line detection means 315.

[Recording head movement: 1-pass bidirectional printing (FIGS. 5A to 5C)]
5A to 5C are schematic diagrams showing the movement of the recording head when one page is divided into a plurality of bands and printing is performed in one-pass bidirectional. FIG. 5A shows an example in which there are objects to be printed in band 1 and band 2, and printing is performed by the recording heads reciprocating alternately. In the figure, after printing in the A direction (outward path), the head direction detecting means 318 determines that the next printing direction is the B direction and performs printing in the B direction (return path). At this time, the 0-line detection unit 315 scans the band memory 313 or 314 to determine whether there is an object to be printed in the band to be printed next.

  The band memories 313 and 314 store the same object data in which the color conversion process is changed, so either of them may be searched to determine the presence or absence of an object. In the present embodiment, the method of determining the presence / absence of an object checks whether each bit of the band memory has image data (1) and none (0) in each line. In addition to this, there is a method in which the intermediate code stored in the intermediate code memory is examined and the determination is made from the print coordinate data of the object.

  In FIG. 5A, since there is an object to be printed in band 2 after printing in the A direction with band 1, the head direction detecting means 318 selects the band memory 314 on the opposite side of the forward path with the band memory selecting means 317, and further the printer. The engine 303 is instructed to print in the B direction.

  The dot data generation means 316 converts the KCMY color 4-bit data read from the selected band memory into KCMY color 1-bit data of the image formation resolution (output resolution) using a dot matrix. For example, dot data having an output resolution of 1200 dpi × 1200 dpi is generated using a 2 × 2 dot matrix for a rendering resolution of 600 dpi × 600 dpi.

  FIG. 5B shows an example of a page in which there are objects to be printed in band 1 and band 3, but there are no objects to be printed in the entire area (X) in band 2. In the figure, after printing in the A direction, the 0-line detecting means 315 scans the band memory 313 or 314 and informs the head direction detecting means 318 that there is no object to be printed in the band to be printed next. Instruct. The head direction detection unit 318 transmits this to the printer engine 303. The printer engine 303 feeds paper in the paper feed direction C by the width of the band 2 without performing printing with the position of the recording head as it is. At this time, the head direction detection means 318 selects the band memory 314 on the opposite side to the forward path by the band memory selection means 317. Subsequently, since there is an object to be printed in the band 3, the head direction detecting means 318 instructs the printer engine 303 to print in the B direction. In this way, when there is no object to be printed on the band, it is possible to realize high-speed and high-quality printing by skipping and selecting print data subjected to appropriate image processing.

  FIG. 5C shows an example in which there is no object to be printed in a partial area X of the band 2 and a partial area Y of the band 3. In the figure, after printing in the A direction with the band 1, the 0-line detecting means 315 scans the band memory 313 or 314, and there is an object to be printed on the front side in the printing direction B of the band 2. However, it detects that there is no object to be printed in the area X on the rear end side, and instructs the head direction detecting means 318. The head direction detection means 318 transmits this to the printer engine 303 and the band memory selection means 317 selects the band memory 314 on the side opposite to the forward path.

  The printer engine 303 prints in the B direction and stops until reaching an area X where there is no object to be printed. Here, the 0-line detection means 315 scans the band memory 313 or 314 and detects that there is no object to be printed in a partial area Y of the next band 3. The head direction detecting means 318 determines that the print direction is the B direction continuously because there is no object to be printed behind the main scanning position of the current recording head and there is an object to be printed ahead, and the printer engine 303 Instruct this. In this case, the band memory selection means 317 keeps selecting the same band memory 314 as that of band 2. The printer engine 303 feeds paper in the paper feed direction C by the width of the band 2 without changing the position of the recording head. Subsequently, in the band 3, the recording head is advanced to the object position to be printed in the B direction, and printing is started.

  In this way, even when the printing direction of the recording head changes according to the position of the object to be printed and the reciprocating movement of the recording head is not performed alternately, a band memory that has been subjected to correct image processing can be selected. . FIG. 5 shows an example, and there are various patterns depending on the position of the object to be printed.

[Flow of print control processing: FIG. 6]
Hereinafter, the flow of the print control process in the first embodiment will be described with reference to the flowchart of FIG. First, in step S601, the host computer 301 waits for transmission of PDL language data. When the PDL language data is transmitted, an intermediate code is created in step S602. Here, intermediate codes for the forward path and the backward path are created using the forward path 307 profile and the backward path profile 308 of FIG. 1 and stored in the two intermediate code memories 309 and 310, respectively.

  In step S603, rendering for one band is performed. Steps S603 to S607 are performed for each band. In step S603, the renderers 311 and 312 in FIG. 1 perform rendering from the intermediate codes stored in the intermediate code memories 309 and 310, and develop them in the band memories 313 and 314.

  In step S604, the printing direction for the next band is determined. The 0-line detection unit 315 and the head direction detection unit 318 in FIG. 1 determine the printing direction for the next band. In the case of printing in the forward direction, the process proceeds to step S605, and in the case of printing in the backward direction, the process proceeds to step S606.

  In step S605, the band memory selection unit 317 in FIG. 1 selects the band memory 313, and the dot data generation unit 316 generates dot data from the rendering output read from the selected band memory. Further, it instructs the printer engine 303 to print in the forward direction.

  In step S606, the band memory selection unit 317 in FIG. 1 selects the band memory 314, and the dot data generation unit 316 generates dot data from the rendering output read from the selected band memory. Further, the printer engine 303 is instructed to print in the backward direction.

  In step S607, printing for one band is performed, and then the recording medium is transported for one band in the transport direction.

  Finally, in step S608, it is determined whether printing of all the bands on one page has been completed. If there is still a remainder, the next band printing process is repeated from step S603. When all the operations are completed in step S608, the process returns to step S601 to wait for data reception.

  In the above-described configuration, data (intermediate code) of the same band is created corresponding to each of the forward path and the backward path, and one of the data is selected according to the scanning direction. Since the data corresponding to the scanning direction is stored in the band memories 313 and 314, the data suitable for the scanning direction can be used simply by selecting the memory for reading the data used in the next scanning according to the scanning direction. Can be recorded. If the memories 313 and 314 are set to have different memory spaces on the same memory, the memory is selected by changing the designated address.

  As described above, in the present embodiment, (1) the forward drawing data or the backward drawing data used for printing in the forward and backward passes in the scanning direction of the recording head is generated from the input image data, and is generated in band units. (2) Detecting the scanning direction of the recording head and the presence or absence of drawing data stored in band units, and selecting the drawing data suitable for the detected scanning direction of the recording head to form an image. For this reason, since image recording suitable for the forward path and the backward path can be realized, it is possible to eliminate color unevenness caused by a difference in the ink color landing order between the forward path and the backward path, which has been a problem in the past.

<Second Embodiment>
In the first embodiment described above, the drawing data for the forward path and the backward path are created, the object developed in the band memory is inspected in the scanning direction of the recording head, and the scanning direction of the recording head is detected. Based on the detected scanning direction of the recording head and the drawing data recorded in the band memory, print data to be used for printing the next band is selected. Similar effects can be obtained by the method of the second embodiment described below.

  Next, the flow of data processing will be described with reference to FIG. In FIG. 12, a host 1201 creates color information as a color application, converts color data corresponding to the color information into a PDL language format, and sends the converted PDL language data to the printing device controller 1202 of the printing device. It is a computer. Here, PDL language data flows between the host computer 1201 and the controller 1202. The PDL language data sent to the controller 1202 is temporarily stored in an input buffer (data input buffer) 1204.

  Intermediate code generation means 1205 and 1206 of the controller read and interpret the PDL language data in the input buffer, and generate an intermediate code (display list). Here, the intermediate code generation unit 1205 generates an intermediate code for the forward path by using the profile A 1207 for performing image processing suitable for the print head arrangement K-> C-> M-> Y when the recording head moves in the forward direction. And stored in the intermediate code memory 1209.

  Similarly, the intermediate code generation unit 1206 generates an intermediate code for the backward path using a profile B1208 that performs image processing suitable for the print head arrangement Y-> M-> C-> K when moving in the backward direction. Stored in the intermediate code memory 1210.

  The image processing performed by the intermediate code generation means is normally used for the ink processing of the printer from the RGB (additive color mixing) RGB (additive color mixture) of the monitor color system used in the host computer to the yellow, magenta, cyan, black. Is converted to YMCK (subtractive color mixture). The parameters of the image processing are adjusted to the optimum values for the print head arrangement.

  The renderer 1212 reads the intermediate code selected by the intermediate code memory selection unit 1211 and executes color rendering processing with ASIC (application-specific IC) hardware, so that the renderer 1212 can execute the image in synchronization with the video transfer to the printer engine 1203. Rendering processing is performed in time, and banding processing with a small memory capacity is realized.

  The band memory 1213 is an area for storing an image developed in the PDL language. In order to perform the banding process described above, the band memory 1213 has two bands when the controller can control the movement of the recording head, such as an ink jet printer. The minimum memory is sufficient.

  The renderer 1212 may be realized by software instead of hardware for cost reduction. In FIG. 12, the renderer 1212 interprets the intermediate code stored in the intermediate code memory selected by the intermediate code memory selection means 1211 and develops it in the band memory 1213.

  The head direction detecting means 1216 detects the current position of the recording head of the printer engine 1203 with an encoder, a sensor or the like, and determines the print direction of the next band in accordance with the detection result of the 0 line detecting means 1215.

  As described above, in the configuration of the second embodiment, the scanning direction of the recording head is detected as in the first embodiment, the object developed in the band memory is inspected, and the detected scanning direction and By controlling the intermediate code memory selection unit 1211 based on the drawing data recorded in the band memory, the same effect as in the first embodiment can be obtained.

[Other Embodiments]
The present invention can take the form of, for example, an apparatus, a method, a program, or a storage medium. Specifically, a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) The present invention may be applied to a system configured from the above, or may be applied to an apparatus (for example, a copier, a facsimile machine, etc.) including one device.

  Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is based on the instruction of the program code. It goes without saying that the CPU or the like provided in the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing. When the present invention is applied to the above-described storage medium, the storage medium stores a program that realizes the processing illustrated in FIGS. 2A to 4 described above.

It is a block diagram which shows the basic composition of the data processing of the 1st Embodiment of this invention. It is a perspective view which shows the inkjet recording device of a prior art example. FIG. 4 is a schematic diagram illustrating ejection ports arranged in a recording head. FIG. 4 is a diagram illustrating an arrangement of recording heads on a carriage. FIG. 6 is a schematic diagram illustrating the movement of the recording head when one page is divided into a plurality of bands and printing is performed in one-pass bidirectional. FIG. 6 is a schematic diagram showing the movement of the recording head (when skipping is included) when one page is divided into a plurality of bands and printed in one-pass bidirectional. FIG. 6 is a schematic diagram illustrating the movement of the recording head when one page is divided into a plurality of bands and printing is performed in one-pass bidirectional (when the recording head is stopped and skipped halfway). 6 is a flowchart illustrating a flow of print control processing in the embodiment. It is the schematic which shows the recording part in embodiment. It is a schematic block diagram of the controller part in an inkjet recording device. 2 is a schematic block diagram of a printer engine unit in the ink jet recording apparatus. FIG. It is a figure explaining the data processing flow in a prior art example controller. A description will be given of how ink penetrates and fixes on the recording paper when landing on the recording paper in the order of CM in the forward scanning, and recording paper of ink when landing on the recording paper in the order of MC on the backward scanning. FIG. It is a block diagram which shows the basic composition of the data processing of the 2nd Embodiment of this invention.

Explanation of symbols

301 Host computer 302 Controller 303 Printer engine 304 Input buffer 305 Intermediate code generation means (for forward path)
306 Intermediate code generation means (for return trip)
307 Profile A
308 Profile B
309 Intermediate code memory 310 Intermediate code memory 311 Renderer 312 Renderer 313 Band memory 314 Band memory 315 0 line detection means 316 Dot data generation means 317 Band memory selection means 318 Head direction detection means

Claims (9)

A plurality of recording heads corresponding to different color inks are arranged along the main scanning direction, and ink is ejected from the plurality of recording heads while the plurality of recording heads are reciprocally scanned along the main scanning direction. An image forming apparatus for forming a color image on a recording medium by:
Image processing means for performing image processing on the image data in units of image data corresponding to a predetermined area on a recording medium, and an image when performing image formation in scanning in the forward direction of the plurality of recording heads Image processing means for performing image processing on image data corresponding to the same predetermined area by a forward path profile used for processing and a backward path profile used for image processing when performing image formation in scanning in the backward direction When,
A memory for storing image data after being subjected to image processing by the image processing means;
Corresponding to the scanning direction of the plurality of recording heads, either the outbound data after being processed according to the outbound path profile stored in the memory or the inbound data after being processed according to the outbound path profile And selecting means for selecting each time the predetermined area is recorded,
An image forming apparatus comprising:   2. The profile according to claim 1, wherein the outward profile and the backward profile are profiles used for image processing for matching colors of an image recorded during forward scanning and an image recorded during backward scanning. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the image data is data described in a page description language. Intermediate code generating means for generating an intermediate code according to the image data described in a page description language;
Rendering means for expanding the intermediate code into data to be recorded;
Further comprising
The image forming apparatus according to claim 3, wherein the image processing unit performs processing on the image data in generating the intermediate code. The memory stores data obtained by developing the intermediate code for forward scanning processed according to the outward profile and data obtained by developing the intermediate code for backward scanning processed according to the backward profile,
5. The image according to claim 4, wherein the selection unit selects one of the forward scan data and the backward scan data after being developed in correspondence with the recording of the predetermined area. Forming equipment. The memory stores the intermediate code for forward scanning processed according to the outward profile and the intermediate code for backward scanning processed according to the backward profile,
The selecting means selects either the intermediate code for forward scanning or the intermediate code for backward scanning in correspondence with recording of the predetermined area,
The image forming apparatus according to claim 4, wherein the selected intermediate code is expanded and recorded by the rendering unit.   The image forming apparatus according to claim 1, wherein the predetermined area is an area recorded by one scanning in the main scanning direction of the plurality of recording heads. A detection means for detecting whether a scanning direction of the plurality of recording heads is an outward direction or a backward direction when recording an image;
The image forming apparatus according to claim 1, wherein the selection unit performs selection according to a detection result by the detection unit. A plurality of recording heads corresponding to different color inks are arranged along the main scanning direction, and ink is ejected from the plurality of recording heads while the plurality of recording heads are reciprocally scanned along the main scanning direction. A method for controlling an image forming apparatus for forming a color image on a recording medium by:
An image processing step of performing image processing on the image data in units of image data corresponding to a predetermined area on a recording medium, and an image when performing image formation in scanning in the forward direction of the plurality of recording heads An image processing step of performing image processing on image data corresponding to the same predetermined area by an outward profile used for processing and a backward profile used for image processing when image formation is performed in scanning in the backward direction When,
A storage step of storing the image data after the image processing is performed in the image processing step in a memory;
Corresponding to the scanning direction of the plurality of recording heads, either the outbound data after being processed according to the outbound path profile stored in the memory or the inbound data after being processed according to the outbound path profile And a selection step of selecting each time recording of the predetermined area;
A control method comprising:

Images