JP5884331B2 - Image forming apparatus, image forming control method, and image forming control program - Google Patents

Description

  The present invention relates to an image forming apparatus, an image forming control method, and an image forming control program. More specifically, the present invention relates to an image forming apparatus, an image forming control method, and an image forming control program for recording an image by dividing a light writing light beam into a plurality of parts. .

  In an image forming apparatus such as a color composite apparatus or a large-sized image forming apparatus, there is a demand for high quality output images, and toners of four colors C (cyan), M (magenta), Y (yellow), and K (black) are used. In addition to (developer), special colors (hereinafter referred to as “special colors”) such as transparent toner and white toner are added to form images with 5 or more toners. By performing density printing using different toners, image quality is improved and corporate colors used for company logos are printed out.

  In order to perform such multi-color printing and light / dark printing at low cost, conventionally, a plurality of polygon mirrors are mounted on one polygon part, and a plurality of laser beams are incident and reflected light reflected by each polygon mirror. There is a polygon sharing technique that reduces the number of polygon parts used for scanning with polygon laser light that scans different photosensitive members. Further, conventionally, a laser beam modulated based on a plurality of image data is emitted from one semiconductor laser, the laser beam is divided by an optical device such as a beam splitter and the like, and each is scanned on a photoconductor to make a semiconductor. There is a beam division scanning technique for reducing the number of lasers (see Patent Document 1).

  Utilizing this conventional polygon sharing technology and beam division scanning technology, the polygon portion is shared and used, and the laser beam emitted from one semiconductor laser is divided into, for example, two laser beams to form a photosensitive member. When scanning, since the light transmittance in the optical path of each divided laser beam is different, there has been a problem that the maximum light amount of the laser beam scanned on the photosensitive member is changed and the image quality is deteriorated.

  And in patent document 1, in the Example, by making the light emission intensity | strength in a light source different when optically scanning a different photoreceptor surface, the light quantity which reaches | attains on a different photoreceptor surface is made equal, or one laser beam is emitted. The transmittance / reflectance of the half mirror in the half mirror prism divided into two is not set to 1: 1, but the ratio of the transmittance and the reflectance is adjusted to equalize the amount of light reaching the different photoreceptor surfaces. Have been described.

  However, in the prior art described in the above publication, the light emission intensity of the light source is different for each photoconductor, or the transmittance / reflectance of the half mirror of the half mirror prism that divides one laser beam is different. Although it is described that the light intensity on the photosensitive member irradiated with each of the divided laser lights emitted from the two laser light sources is the same, how to make the light intensity the same However, when the image is formed using the polygon sharing technique and the beam division scanning technique, the problem is that the maximum light amount on the photoconductor is different and the image quality deteriorates. In order to solve this problem, improvement was necessary.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve the image quality of an image formed by scanning a plurality of photosensitive members by dividing one writing light emitted from one light source into a plurality of divided writing lights. Yes.

In order to achieve the above object, the image forming apparatus according to the present invention divides the image data of a predetermined color into a plurality of divided image data having different shades according to a value indicating the density of the image data of the predetermined color. And one writing light modulated and emitted from one light source unit based on the plurality of divided image data having different shades and divided into divided writing light for each of the divided image data, and each of the divided writings Split scanning means for causing light to pass through the split scanning optical path and scanning the corresponding photosensitive member for a predetermined time , and the data splitting means is determined based on the light transmission efficiency of the split scanning optical path using the distribution parameter, the light source unit to adjust the data value of the plurality of the divided image data to be input by dividing in the allocation parameter, the density of the image data of the predetermined color I am characterized in that the information to specify a value indicative of the concentration of a different plurality of divided image data of the grayscale according to to the value.

  According to the present invention, it is possible to improve the image quality of an image formed by scanning a plurality of photosensitive members by dividing one writing light emitted from one light source into a plurality of divided writing lights.

1 is a block diagram of a main part of an image forming apparatus to which an embodiment of the present invention is applied. 1 is a schematic configuration diagram of a print engine. FIG. 2 is a main part configuration diagram of an optical scanning device. The figure which shows the scanning timing to the corresponding photoreceptor of the laser beam divided | segmented into two. Explanatory drawing of the light beam splitting process by a light beam splitting element. The figure which shows the light intensity on the photoconductor of the laser beam divided | segmented into two. The block block diagram of an image processing unit. The block block diagram of a color conversion unit. The figure which shows an example of a basic separation table. The figure which shows an example of the color separation table from which only dark black image data increases from K value smaller than a basic color separation table. FIG. 6 is a diagram illustrating an example of a separation table in which light black image data is saturated with a smaller K value than the basic separation table, and dark black image data increases from a smaller K value. The figure which shows an example of the color separation table which dark gray image data is a curve, and only dark black image data increases from K value smaller than a basic color separation table.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 12 are diagrams showing an embodiment of an image forming apparatus, an image forming control method, and an image forming control program according to the present invention. FIG. 1 is an image forming apparatus, an image forming control method, and an image according to the present invention. 1 is a block configuration diagram of an image forming apparatus 1 to which an embodiment of a formation control program is applied.

  In FIG. 1, an image forming apparatus 1 includes a controller 2, an operation panel 3 connected to the controller 2, a network I / F 5 connected to the controller 2 via a PCI (Peripheral Component Interconnect) bus 4, and a USB I / O. F6, IEEE (Institute of Electrical and Electronic Engineers) 1394 I / F7, engine unit 8 and the like.

  The controller 2 includes a CPU (Central Processing Unit) 11, a system memory (MEM-P) 12, a north bridge (NB) 13, a south bridge (SB) 14, an ASIC (Application Specific Integrated Circuit) 15, a local memory (MEM-C). ) 16 and a hard disk (HDD) 17, and the system memory 12 includes a ROM (Read Only Memory) 12 a and a RAM (Random Access Memory) 12 b.

  The operation panel 3 is connected to the ASIC 15 of the controller 2, and the PCIe bus 4 to which the network I / F 5, USB I / F 6, IEEE 1394 I / F 7 and engine unit 8 are connected is connected to the ASIC 15.

  The controller 2 includes a local memory 16 and a hard disk 17 connected to the ASIC 15, and the CPU 11 and the ASIC 15 are connected via the north bridge (NB) 13 of the CPU chipset. The north bridge (NB) 13 and the ASIC 15 Are connected not by a PCI bus but by an AGP (Accelerated Graphics Port) bus.

  The ROM 12 a of the system memory 12 stores a basic program as the image forming apparatus 1, an image formation control program for executing the image formation control method of the present invention, and necessary data. The CPU 11 is a north bridge (NB) 13. And a chip set including the system memory 12 and the south bridge (SB) 14, and are connected to other devices via the chip set. The CPU 11 uses the RAM 12b as a work memory based on a program stored in the ROM 12a of the system memory 12, and controls each part of the image forming apparatus 1 to execute basic processing as the image forming apparatus 1, and also performs image formation according to the present invention. Execute control processing. The RAM 12b is a memory that can be written and read and used as a memory for developing programs and data, an image drawing memory for image information processing, and the like.

  That is, the image forming apparatus 1 includes a ROM, an EEPROM (Electrically Erasable and Programmable Read Only Memory), an EPROM, a flash memory, a flexible disk, a CD-ROM (Compact Disc Read Only Memory), a CD-RW (Compact Disc Rewritable), a DVD. An image formation control program for executing the image formation control method of the present invention recorded on a computer-readable recording medium such as a (Digital Versatile Disk), an SD (Secure Digital) card, or an MO (Magneto-Optical Disc) is read. Thus, it is constructed as an image forming apparatus that executes an image forming control method for efficiently and rapidly identifying related information embedded in image data, which will be described later, by being introduced into the ROM 12a and the hard disk 17. This image formation control program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark), an object-oriented programming language, or the like, and is stored in the recording medium. Or distributed over a network.

  The image forming control program includes each part of the image forming apparatus 1 described later, that is, a color correction unit, a black generation unit, a UCR unit, a Dk / Lk color separation unit, a scanner γ correction unit, an input masking unit, a filter processing unit, and a selector. , A storage unit, a printer γ correction unit, a halftone processing unit, an output engine, and the like. As actual hardware, the CPU 11 reads out and executes an image formation control program from the ROM 12a, Each unit is loaded on the RAM 12b, and a color correction unit, black generation unit, UCR unit, Dk / Lk color separation unit, scanner γ correction unit, input masking unit, filter processing unit, selector, storage unit, printer γ correction unit, A halftone processing unit, an output engine, and the like are generated in the RAM 12b.

  The north bridge (NB) 13 is a bridge for connecting the CPU 11, the system memory 12, the south bridge (SB) 14, and the ASIC 15. The north bridge (NB) 13 includes a memory controller that controls reading and writing to the system memory 12, a PCI master, and an AGP target. doing.

  The south bridge (SB) 14 is a bridge for connecting the north bridge (NB) 13 to the PCI bus and peripheral devices, and the local memory 16 is a memory used as a copy image buffer and a code buffer.

  The ASIC 15 is an image processing application IC (Integrated Circuit) having hardware elements for image processing, and includes an image processing unit 50 (see FIG. 7), which will be described later, and an AGP and PCI bus. , A hard disk (HDD) 17 and a local memory 16 are connected to each other.

  The ASIC 15 includes a plurality of DMACs (Direct Memory Access Controllers: DMA) that perform image data rotation and the like by a PCI target and an AGP master, an arbiter (ARB) that forms the core of the ASIC 15, a memory controller that controls the local memory 16, hardware logic, and the like. The network I / F 5, USB I / F 6, and IEEE 1394 I / F 7 are connected between the controller) and the engine unit 8 via the PCI bus.

  The local memory 16 is a local memory used as a transmission image buffer and a code buffer, and a hard disk (HDD) 17 is a storage for storing image data, programs, font data, and forms. .

  The AGP is a bus interface for a graphics accelerator card proposed for speeding up graphics processing, and directly accesses the system memory 12 with high throughput to speed up the graphics accelerator card.

  The hard disk 17 is a storage for storing image data, document data, programs, font data, forms, and the like.

  The operation panel 3 includes various operation keys, a display, and the like, receives input operations from the various operation keys by the operator, and displays various information on the display to the operator.

  The network I / F 5 is connected to a network to which other network devices such as another composite device 1 and a host device such as a computer are connected. The network I / F 5 is connected to other network devices and host devices via the network. Communicate with other network terminals.

  A USB device such as a USB memory is detachably connected to the USB I / F 6, and the USB I / F 6 has a function for controlling a physical / electrical I / F and a USB protocol for communicating with the USB device. It has a function to control and communicates with the USB device.

  The IEEE 1394 I / F 7 communicates with a host device or the like by wire.

  The engine unit 8 forms a color image on a sheet (recording medium) P based on the image data from the scanner 8a that reads the image data of the document by main scanning and sub-scanning the document and the controller 2 shown in FIG. The print engine 20 or the like.

  As shown in FIG. 2, the print engine 20 includes Y (yellow), M (magenta), and C (cyan) along a conveyance belt 23 that is stretched between a pair of rollers 21 and 22 over a predetermined length. , S (special color) and six image forming portions 24Y, 24M, 24C, 24S, 24Lk, and 24Dk that form images of each color of Lk (light black) and Dk (dark black) are arranged at equal intervals. The sheet P is fed to the transport belt 23 after the timing is adjusted by a registration roller from a sheet feeding unit (not shown).

  Each of the image forming units 24Y, 24M, 24C, 24S, 24Lk, and 24Dk is centered around the photoreceptors 25Y, 25M, 25C, 25S, 25Lk, and 25Dk that are driven to rotate clockwise with the same diameter. As process members for forming an image according to the photographic process, charging chargers 26Y, 26M, 26C, 26S, 26Lk, 26Dk, optical scanning devices 27a, 27b, developing units 28Y, 28M, 28C, 28S, 28Lk, 28Dk, transfer charger 29Y 29M, 29C, 29S, 29Lk, 29Dk, cleaning units 30Y, 30M, 30C, 30S, 30Lk, 30Dk, and the like are sequentially arranged.

  The optical scanning device 27a includes Y, M, C, and S semiconductor lasers 31Y, 31M, 31C, and 31S, one polygon unit 32 having polygon mirrors 32u and 32l attached in two stages to one polygon motor, and the illustration. An optical system such as a mirror is provided, and each semiconductor laser 31Y, 31M, 31C, 31S emits laser light modulated based on image data of each color of Y, M, C, S to polygon mirrors 32u, 32l. Then, the laser beams reflected by the polygon mirrors 32u and 32l are scanned onto the photoconductors 25Y, 25M, 25C, and 25S through the optical system. At this time, in the optical scanning device 27a, the semiconductor laser 31M and the semiconductor laser 31C emit laser light to the upper polygon mirror 32u, and the semiconductor laser 31Y and the semiconductor laser 31S emit laser light to the lower polygon mirror 32l. To do.

  The optical scanning device (divided scanning means) 27b includes one semiconductor laser 33 and one polygon section 34 having polygon mirrors 34u and 34l attached in two stages to one polygon motor and an optical system (not shown). The semiconductor laser (light source) 33 emits one laser beam (writing light) modulated by the dark black image data dk having a high density and the light black image data lk having a low density toward the polygon portion 34, which will be described later. As described above, the divided laser beams (divided writing beams) Lku and Lkl obtained by dividing the single laser beam are reflected by the polygon mirrors 34u and 34l, and scanned on the photosensitive members 25Lk and 25Dk through the optical system. The optical scanning device 27b will be described later in detail.

  In the print engine 20, a fixing unit 35 is disposed on the downstream side in the rotation direction of the conveyance belt 23. The fixing unit 35 transfers the toner image by the image forming units 24Y, 24M, 24C, 24S, 24Lk, and 24Dk. The heated paper P is conveyed while being heated and pressurized to fix the toner image on the paper P, and sent to a subsequent stage such as a post-processing device that performs post-processing such as a paper discharge tray and stapling processing (not shown).

  The print engine 20 includes yellow (Y), magenta (M), magenta (M), and photoconductors 25Y, 25M, 25C, 25S, 25Lk, and 25Dk that are uniformly charged by the chargers 26Y, 26M, 26C, 26S, 26Lk, and 26Dk. Electrostatic scanning is performed by laser scanning of the laser beams by the respective optical scanning devices 27a and 27b based on the image signals of the respective colors for cyan (C), special color (S), light black (Lk), and dark black (Dk). A latent image is formed, and the electrostatic latent image is developed with toner of each color by the developing units 28Y, 28M, 28C, 28S, 28Lk, and 28Dk to form a toner image. The print engine 20 electrostatically attracts the toner images on the photoconductors 25Y, 25M, 25C, 25S, 25Lk, and 25Dk onto the conveyance belt 21 by the transfer chargers 29Y, 29M, 29C, 29S, 29Lk, and 29Dk. Then, the toner images are sequentially transferred onto the sheet P to be conveyed and superimposed, and a color toner image is transferred onto the sheet P. The print engine 20 conveys the paper P, which has been transferred, while being heated and pressurized by the fixing unit 35, fixes the color toner image on the paper P, and sends the paper P, on which the color toner image has been fixed, to the subsequent stage. The print engine 20 operates only the image forming units 24Y, 24M, 24C, 24S, 24Lk, and 24Dk of the colors to be used when forming images of several colors such as a single color mode or two colors and three colors. To form an image.

  As shown in FIG. 3, the optical scanning device 27b includes a timing adjustment unit 41, a semiconductor laser 33, a collimating lens 42, a light beam splitting optical element 43, an aperture 44, a pair of cylindrical lenses 45u and 45l, and a polygon mirror 34u. A polygon unit 34 provided with a polygon mirror 34l is provided.

  The timing adjustment unit 41 receives light black image data lk and dark black image data dk from an image processing unit 50 described later. The timing adjustment unit 41 adjusts the timing of the light black image data lk and dark black image data dk. And output to the semiconductor laser 33.

  The semiconductor laser 33 emits one laser beam Lk modulated based on the light black image data lk and the dark black image data dk to the collimating lens 42, and the collimating lens 42 has a luminous flux form suitable for the subsequent optical system ( The light beam is converted into a parallel light beam or a light beam having a weak divergence or a weak convergence property, and is emitted to the light beam splitting optical element 43. In the optical scanning device 27 b of this embodiment, the collimator lens 42 converts the laser light Lk incident from the semiconductor laser 33 into a parallel light beam and emits it to the light beam splitting optical element 43.

  As will be described later, for example, the light beam splitting optical element 43 uses a half mirror prism. The laser light Lk incident from the collimating lens 42 is converted into two laser lights Lku and Lkl in the vertical direction in FIG. Divide and output to the aperture 44.

  The aperture 44 has an opening that regulates the width of the laser beam, and the laser beams Lku and Lkl pass through the opening, so that the beam is shaped and incident on the cylindrical lenses 45u and 45l.

  The cylindrical lenses 45u and 45l condense the laser beams Lku and Lkl formed by the aperture 44 in the sub-scanning direction, and are long in the main scanning direction in the vicinity of the polygon mirror 34u of the polygon portion 34 and the deflection reflection surface of the polygon mirror 34l. It is formed as a line image.

  The polygon unit 34 has an upper polygon mirror 34u and a lower polygon mirror 34l mounted on a rotation shaft 34j in parallel at the top and bottom of FIG. 3, and the polygon mirror 34u and the polygon mirror 34l are combined into one polygon. Driven by a motor.

  Each of the polygon mirror 34u and the polygon mirror 34l is a polygon mirror having the same shape having four deflection reflection surfaces, and the deflection reflection of the lower polygon mirror 34l with respect to the deflection reflection surface of the upper polygon mirror 34u. The surface is formed in a state shifted by a predetermined angle: θ (= 45 degrees) in the rotation direction.

  The polygon section 34 scans the photoconductor 25Dk and the photoconductor 25Lk by polarizing the laser beams Lku and Lkl incident on the polygon mirror 34u and the polygon mirror 34l, which are rotationally driven from the cylindrical lenses 45u and 45l, in the main scanning direction, respectively. At the same time, the deflecting and reflecting surfaces of the polygon mirror 34u and the polygon mirror 34l are formed so as to be deviated by 45 degrees, so that the laser beams Lku and Lkl scanned on the photoreceptor 25Dk and the photoreceptor 25Lk are also scanned in the main scanning direction. Are separately scanned, and the two laser beams Lku and Lkl that optically scan the photoconductors 25Dk and 25Lk are individually detected, and the start of optical scanning can be synchronized for each of the laser beams Lku and Lkl.

  That is, since the deflection reflection surfaces of the upper polygon mirror 34u and the lower polygon mirror 34l of the polygon portion 34 are deviated from each other by 45 degrees in the rotation direction, as shown in FIG. 4, the deflection laser beam Lku by the polygon mirror 34u is obtained. When performing optical scanning (effective pixel scanning) of the photosensitive member 25Dk, the deflected laser light Lkl by the polygon mirror 34l is not guided to the photosensitive member 25Lk but becomes blank, and the deflected laser light Lkl by the polygon mirror 34l is used as the photosensitive member. When 25 Lk optical scanning (effective pixel scanning) is performed, the deflection laser light Lku from the polygon mirror 34 u is not guided to the photosensitive member 25 Dk, but is blank. In other words, the polygon unit 34 causes the laser beam Lku and the laser beam Lkl to pass through the photosensitive member 25Dk and the photosensitive member 25Lk, respectively, by the polygon mirror 34u and the polygon mirror 34l whose deflection reflection surfaces are deviated from each other by 45 degrees in the rotational direction. Are alternately shifted. In FIG. 4, the laser beams Lku and Lkl and the laser beams Lku and Lkl in the effective scanning area (the period during which the photosensitive members 25Dk and 25Lk are scanned) are arranged on the respective time axes. The laser beams Lku and Lkl scan the photoconductors 25Dk and 25Lk alternately with a time shift.

  As shown in FIG. 5, the light beam splitting element 43 has a semi-transparent mirror 43 a and a reflecting surface 43 b in parallel with the sub-scanning direction which is the vertical direction in FIG. 5. 42 is incident. The beam splitting element 43 makes the laser beam Lk incident through the collimator lens 42 enter the semi-transparent mirror 43a, and partly transmits the laser beam Lku straightly through the semi-transparent mirror 43a to be emitted to the aperture 44 as the laser beam Lku. The remainder is reflected by the semi-transparent mirror 43a and enters the reflecting surface 43b. The reflection surface 43b of the light beam splitting element 43 totally reflects the laser light incident from the semi-transparent mirror 43a and outputs the laser light Lkl to the aperture 44.

  In the beam splitter 43, the semi-transparent mirror 43 a and the reflecting surface 43 b are parallel to each other, and the laser beam Lku and the laser beam Lkl that are parallel to each other are output to the aperture 44.

  The light beam splitting element 43 splits the laser light Lk emitted from the semiconductor laser 33 into two parallel laser lights Lku and laser light Lkl in the sub-scanning direction. The laser light Lku is transmitted light, and the laser light Lkl. Is a two-stage reflected light and, as shown in FIG. 6, there is a variation in transmittance and reflectance, so that the laser light Lku and the laser light Lkl have different light amounts. That is, as shown in FIG. 6, a laser beam Lk emitted from a semiconductor laser 33, which is one light source, is split into a laser beam Lku and a laser beam Lkl by a beam splitter 43 having parallel reflecting surfaces 43a and 43b. When writing an image on the photosensitive member 25Dk and the photosensitive member 25Lk, the semiconductor laser 33, which is a light source in the time region for writing an image on the photosensitive member 25Dk with the laser light Lku and the time region for writing the image on the photosensitive member 25Lk with the laser light Lkl. If the emission intensity is set to be the same, the number of the semiconductor lasers 33 is one. Therefore, in each optical path (divided scanning optical path) from the semiconductor laser 33 to the photoconductors 25Dk and 25Lk, the relative transmittance and reflectance of the optical element. Due to the difference, the light amounts of the laser light Lku and the laser light Lkl reaching the respective photosensitive members 25Dk and 25Lk are different. That the results become.

  The image forming apparatus 1 includes an image processing unit 50 as shown in FIG. 7 in the ASIC 15 of the controller 2. The image processing unit 50 includes a scanner γ correction unit 51, an input masking unit 52, and a filter processing unit 53. , A selector 54, a host I / F 55, an image development unit 56, a storage unit 57, a color conversion unit 58, a printer γ correction unit 59, a halftone processing unit 60, and the like.

  As the scanner 8a, for example, an image scanner using a CCD (Charge Coupled Device) or the like is used, and generally includes an ADF (Automatic Document Feeder). A plurality of originals are set in the ADF, and the ADF feeds the set originals one by one to the original reading position of the scanner 5. The scanner 8 a scans the document conveyed from the ADF, reads an image of the document with a predetermined resolution, and outputs digital r, g, and b image data to the scanner γ correction unit 51.

  The scanner γ correction unit 51 converts digital r, g, and b image data input from the scanner 8a from a reflectance linear signal to a density linear signal, and outputs the converted signal to the input masking unit 52 for input masking. The unit 52 converts the signal dependent on the input device input from the scanner γ correction unit 51 into a standard signal such as sRGB that does not depend on the device, and outputs the signal to the filter processing unit 53.

  The filter processing unit 53 corrects the spatial frequency characteristics for the image data input from the input masking unit 52. Specifically, the printer processing unit 53 sharply corrects an image with an edge enhancement filter for an image that requires sharpness such as characters, and for an image that requires smoothness such as a photograph. Then, the image is softly corrected by the smoothing filter and output to the selector 54.

  On the other hand, the host I / F 55 is an interface such as a Centronics I / F, a network I / F5, or a USB I / F6, and communicates with a host device such as a computer connected by a Centronics cable, a network, a USB cable, or the like. The image data and a page description language (PDL (Page Description Language) such as a printout command for the image data are received. The host I / F 55 outputs the page description language received from the host device to the image development unit 56.

  The image development unit 56 analyzes the page description language and develops it into image data. In this page description language, a special color (assumed to be transparent in the present embodiment) is also specified. The RGB image data is output to the selector 56. The transparent toner is used to control the gloss of the image output by the print engine 20 and gives an artistic effect.

  The selector 54 selects either RGB image data from the filter processing unit 53 or SRGB image data from the image development unit 56 and stores the selected data in the storage unit 57. The storage unit 57 uses the local memory 16 or the hard disk 17 and temporarily stores image data.

  The color conversion unit 58 uses the S, C, M, Y, and S, in order to form the RGB or SRGB image data of the storage unit 57 with the s, c, m, y, dk, and lk toners in the print engine 20. Color separation into six colors Dk and Lk is performed and output to the printer γ correction unit 59.

  The printer γ correction unit 59 performs γ characteristic conversion on S, C, M, Y, Dk, and Lk image data input from the color conversion unit 58 using a γ correction table (not shown), and performs halftone processing. To the unit 60.

  The halftone processing unit 60 performs a predetermined dither process on the S, C, M, Y, Dk, and Lk image data that has been γ-corrected by the printer γ correction unit 59 to obtain s, c, m, and y. , Dk, and lk are output to the optical scanning devices 27 a and 27 b of the print engine 20.

  As shown in FIG. 8, the color conversion unit 58 includes a color correction unit 71, a UCR unit 72, a black generation unit 73, a color separation unit 74, buffers 75a and 75b, and the like.

  The SRGB image data from the storage unit 57 is input to the color correction unit 71. The color correction unit 71 converts the RGB into CMY image data depending on the print engine 20 that is a device, and converts it into the UCR unit 72 and the color correction unit 71. The ink is output to the black generator 73. The color correction unit 71 outputs the special color S as it is and also outputs it to the UCR unit 72. Specifically, the color correction unit 71 performs a masking operation represented by the following equation (1) on the RGB image data to convert it into CMY image data.

C = α11 × R + α12 × G + α13 × B + α14 × S + β1
M = α21 × R + α22 × G + α23 × B + α24 × S + β2
Y = α31 × R + α32 × G + α33 × B + α34 × S + β3 (1)
Here, α11 to α34 and β1 to β3 are predetermined color correction coefficients, and CMYS also outputs 8-bit signals for RGBS 8-bit (0-255) image signals. It is.

  The black generation unit 73 performs a calculation of the following equation (2) on the CMY image data input from the color correction unit 71 to generate a K signal, and outputs the K signal to the UCR unit 72 and the color separation unit 74.

K = Min (C, M, Y) (2)
The UCR unit 72 is for improving the color reproducibility of the image data. Based on the CMY data input from the color correction unit 71 and the K data input from the black generation unit 73, the UCR unit 72 Thus, the black component is subtracted from CMYK, that is, UCR (Under Color Removal) processing is performed, and the C′M′Y ′ data is output to the printer γ correction arm 59.

C ′ = C−K
M ′ = M−K
Y ′ = Y−K (3)
A color separation unit (data division unit, image adjustment unit) 74 converts the K data generated by the black generation unit 73 into dark black image data (division image data) Dk based on a predetermined color separation table (distribution parameter). After being divided into light black image data (divided image data) Lk and temporarily stored in the buffer 75a and the buffer 75b, respectively, they are output to the printer γ correction unit 59.

  The separation unit 74 normally uses a separation table BT1 as shown in FIG. 9 as a separation table used in the separation process. In the separation table TB1, only the light black image data Lk gradually increases in the range of K values from “0” to “128”, and at “128”, the light black image data Lk is saturated. In the range of “128” to “255”, the dark black image data Dk gradually increases, and when K = 255, Lk = Dk = 255 is output.

  As the separation table, since the exposure light amount of the laser beam Lkl to the photosensitive member 25Lk is low, the image forming apparatus 1 of the present embodiment does not use the separation table TB1 shown in FIG. As shown, the value of the image data K at which the dark black image data Dk begins to increase gradually increases from the value (gradation value) smaller than “128” in the color separation table BT1 shown in FIG. A color separation table TB2 is used as dark black image data Dk2 in which the value of increases.

  Further, as shown in FIG. 11, since the exposure light amount of the laser beam Lkl to the photosensitive member 25 </ b> Lk is low as shown in FIG. 11, the exposure light amount of the laser beam Lku to the photosensitive member 25 </ b> Dk is “ Instead of the color separation table TB1 that gradually increases from “128” to “255”, the value at which the dark black image data Dk begins to increase is set to the dark black image data Dk2 that gradually increases from a value smaller than “128”. From the state Lk in which the light black image data Lk gradually increases from “0” to “255”, the point at which the increase (saturation point) is light black image data Lk2 having a value smaller than “128”. A plate table TB3 may be used.

  Further, as the separation table, since the exposure light amount of the laser light Lkl to the photosensitive member 25Lk is low, as shown in FIG. 12, the light black image data Lk2 is in the range of K values from “0” to “128”. Only gradually increases in a curve, and at “128”, the light black image data Lk2 is saturated, and when the value of K is in a range from a value smaller than “128” to “255”, the dark black image data Dk is The color separation table TB4 which is the dark black image data Dk2 that gradually increases in a curve and outputs Lk = Dk = 255 at K = 255 may be used.

  Next, the operation of this embodiment will be described. The image forming apparatus 1 according to the present embodiment also forms an image by dividing the laser beam Lk emitted from one semiconductor laser 33 into two laser beams Lku and Lkl and irradiating the two photosensitive members 25Dk and 25Lk. , Improve image quality.

  That is, the image forming apparatus 1 performs necessary image processing on the RGB image data or SRGB image data sent from the scanner 8a or the host device, and as s, c, m, y, dk, lk image data, Output to the optical scanning devices 27a and 27b of the print engine 20, and the optical scanning device 27a of the print engine 20 responds from the corresponding semiconductor lasers 31Y, 31M, 31C, and 31S based on the image data of s, c, m, and y. The image forming units 24Y, 24M, 24C, and 24S to be irradiated are irradiated with the photosensitive members 25Y, 25M, 25C, and 25S to form electrostatic latent images, and the optical scanning device 27b modulates the image data based on the dk and lk image data. One laser beam Lk is emitted from one semiconductor laser 33, and this laser beam Lk is divided into two laser beams Lku and Lkl on the way. Corresponding image forming unit 24Lk Te, photoreceptor 25Lk of 24Dk, to form an electrostatic latent image by irradiating the 25Dk. Each of the image forming units 24Y, 24M, 24C, and 24S develops the electrostatic latent images on the photoconductors 25Y, 25M, 25C, and 25S with a corresponding color toner to generate a toner image. The toner images on 25M, 25C, and 25S are sequentially superimposed and transferred onto the paper P conveyed on the conveying belt 23, and sent to the image forming unit 24Lk.

  The image forming unit 24Lk and the image forming unit 24Dk are toners corresponding to the electrostatic latent images formed on the photoconductor 25Lk and the photoconductor 25Dk by the laser beam Lk and the laser beam Dk irradiated from the optical scanning device 27b. Development is performed to generate a toner image, and the toner image is sequentially transferred while being superimposed on the paper P on which the toner image has already been transferred, which is sent from the image forming unit 24S.

  Then, as described above, the optical scanning device 27b uses the light beam splitting optical element 43 to darken one laser beam Lk modulated by one semiconductor laser 33 based on the dark black image data Dk and the light black image data Lk. The laser beam Lku based on the black image data Dk and the laser beam Lkl based on the light black image data Lk are divided, and the beam widths of the laser beams Lku and Lkl are shaped by the aperture 44 and incident on the cylindrical lenses 45u and 45l. 45l, the laser beams Lku and Lkl are condensed in the sub-scanning direction, and in the main scanning direction in the vicinity of the deflecting and reflecting surfaces of the polygon mirror 34u and the polygon mirror 34l attached in parallel to the rotation shaft 34j of the polygon part 34. To form a long line image.

  The polygon mirror 34u and the polygon mirror 34l of the polygon part 34 are polyhedral mirrors having the same shape having four deflecting reflecting surfaces, and the deflecting reflecting surface of the polygon mirror 34l with respect to the deflecting reflecting surface of the polygon mirror 34u. However, when the deflected laser beam Lku by the polygon mirror 34u performs optical scanning (effective pixel scanning) of the photosensitive member 25Dk, as shown in FIG. When the deflection laser beam Lkl by the mirror 34l is blanked without being guided to the photosensitive member 25Lk, and the deflection laser beam Lkl by the polygon mirror 34l performs optical scanning (effective pixel scanning) of the photosensitive member 25Lk, the polygon mirror The deflected laser beam Lku by 34u is not guided to the photoconductor 25Dk, but becomes a blank.

  However, as described above, the beam splitter 43 divides the laser beam Lk emitted from the semiconductor laser 33 into two parallel laser beams Lku and Lkl in the sub-scanning direction, but transmits the laser beam Lku. The light and the laser light Lkl are two-stage reflected light, and as shown in FIG. 6, there are variations in the transmittance and the reflectance. Therefore, the light amounts of the laser light Lku and the laser light Lkl are different. That is, as shown in FIG. 6, the laser beam Lk emitted from the semiconductor laser 33, which is one light source, is split into the laser beam Lku and the laser beam Lkl by the beam splitter 43 having parallel reflecting surfaces 43a and 43b. Then, when writing the electrostatic latent image on the photosensitive member 25Dk and the photosensitive member 25Lk, the electrostatic latent image is written on the photosensitive member 25Dk with the laser beam Lkl and the time region for writing the electrostatic latent image on the photosensitive member 25Dk with the laser beam Lku. If the light emission intensity of the semiconductor laser 33 which is a light source in the time domain is set to be the same, there is one semiconductor laser 33. Therefore, in each optical path (divided scanning optical path) from the semiconductor laser 33 to the photoconductors 25Dk and 25Lk, an optical element is provided. The laser light Lku and the laser light Lk that reach the photoconductor 25Dk and the photoconductor 25Lk depending on the relative difference in transmittance and reflectance The amount of light becomes the different results of.

  Therefore, in the image forming apparatus 1 according to the present embodiment, the RGB image data or the SRGB image data is converted to the s, c, m, y, dk, and lk toners by the print engine 20 in the color conversion unit 58 of the image processing unit 50. In order to form an image, color separation into six colors S, C, M, Y, Dk, and Lk is performed, and the data of the dark black image data Dk and the light black image data Lk is considered in consideration of the difference in the amount of light. Adjust the value.

  Specifically, in the color conversion unit 58, the color correction unit 71 illustrated in FIG. 8 performs the masking operation of the above formula (1) on the SRGB image data, and depends on the print engine 20. The data is converted into data, the black generation unit 73 performs the calculation of the above equation (2) on the CMY image data generated by the color correction unit 71 to generate K data (K signal), and the UCR unit 72 In order to improve the color reproducibility of the image data, UCR processing for subtracting the black component from CMYK according to the above equation (3) based on the CMY data generated by the color correction unit 71 and the K data generated by the black generation unit 73 To output C′M′Y ′ data.

  In the color conversion unit 58, the color separation unit 74 separates the K data generated by the black color generation unit 73 into dark black image data Dk and light black image data Lk based on a predetermined color separation table. Are temporarily stored in the buffer 75a and the buffer 75b, respectively.

  The separation unit 74 uses separation tables TB2 to TB4 as shown in FIGS. 10 to 12 instead of the normal separation table BT1 shown in FIG. 9 as a separation table used in the separation process. .

  That is, in the normal color separation table BT1 shown in FIG. 9, only the light black image data Lk gradually increases when the value of K is in the range of “0” to “128”. When the image data Lk is saturated and the K value is in the range of “128” to “255”, the dark black image data Dk gradually increases, and when K = 255, Lk = Dk = 255 is output. ing.

  On the other hand, the color separation unit 74 now has a low exposure light amount of the laser light Lkl to the photosensitive member 25Lk, and therefore, as shown in FIG. 10, the value of the image data K at which the dark black image data Dk starts to increase. However, the dark black in which the value of the dark black image data Dk gradually increases linearly from a value smaller than “128”, which is the value in which the dark black image data Dk in the color separation table BT1 shown in FIG. 9 gradually increases. The K data is separated into dark black image data Dk and light black image data Lk using a color separation table TB2 that becomes image data Dk1.

  When the image data K is separated into the dark black image data Dk and the light black image data Lk by using such a color separation table BT2, the rate of using the dark black image data Dk increases. The image quality can also be improved when the exposure light amount of the laser light Lkl to the photosensitive member 25Lk is lower than the exposure light amount of the laser light Lku to the photosensitive member 25Dk by the dark black image data Dk.

  Further, as shown in FIG. 11, since the amount of exposure of the laser beam Lkl to the photosensitive member 25Lk is low, the plate separation unit 74 has the darkness of the plate separation table BT1 shown in FIG. The black image data Dk gradually increases from “128” to “255”, and the light black image data Lk gradually increases from “0” and is saturated at “128”, not the color separation table TB1, but a dark black image. The value at which the data starts increasing is the dark black image data Dk1 that gradually increases from a value smaller than “128”, and the light black image data starts increasing from “0” and is smaller than “128”. The K data may be separated into the dark black image data Dk and the light black image data Lk using the color separation table TB3 which is the light black image data Lk1 that is saturated at.

  When the image data K is separated into the dark black image data Dk and the light black image data Lk using the color separation table BT3, the exposure light amount of the photosensitive member 25Lk of the laser beam Lkl by the light black image data Lk is low. Accordingly, from the stage where the value of K is small, the amount of exposure of the laser beam Lku with the dark black image data Dk to the photosensitive member 25Dk can be increased, and the photosensitive member 25Lk of the laser beam Lkl with the light black image data Lk. It is possible to quickly saturate the amount of light exposed to the light and improve the image quality.

  Furthermore, since the light quantity of the laser beam Lkl to the photosensitive member 25Lk is low, the color separation unit 74 has a dark black image data Dk of “128” in the color separation table BT1 shown in FIG. 9, as shown in FIG. Not the separation table TB1 that gradually increases from “255” and the light black image data Lk gradually increases from “0” and is saturated at “128”, but a value at which the dark black image data starts to increase, The dark black image data Dk1 gradually increases in a curve from a value smaller than “128”, and the light black image data starts increasing gradually in a curve from “0” and is saturated at “128”. The K data may be separated into dark black image data Dk and light black image data Lk using a color separation table TB4 which is black image data Lk2. The light black image data Lk2 may be saturated with a smaller value instead of being saturated with “128”.

  When the image data K is separated into the dark black image data Dk and the light black image data Lk using the color separation table BT4, the exposure light amount of the laser light Lkl to the photosensitive member 25Lk by the light black image data Lk is low. However, from the earlier stage, the exposure light amount of the laser light Lku to the photosensitive member 25Dk by the dark black image data Dk can be increased, and the image quality can be improved.

  Then, the color conversion unit 58 temporarily stores the dark black image data Dk and the light black image data Lk separated by the color separation unit 74 in the buffers 75a and 75b, and then outputs them to the printer γ correction unit 59 for the printer γ correction. The unit 59 performs γ characteristic conversion on the S, C, M, Y, Dk, and Lk image data input from the color conversion unit 58 using the γ correction table, and outputs the converted image to the halftone processing unit 60. . The halftone processing unit 60 performs a predetermined dither process on the S, C, M, Y, Dk, and Lk image data that has been γ-corrected by the printer γ correction unit 59 to obtain s, c, m, and y. , Dk, and lk image data are output to the optical scanning devices 27a and 27b of the print engine 20, and the optical scanning device 27a forms laser light modulated by the YMCS image data by the semiconductor lasers 31Y, 31M, 31C, and 31S. The electrostatic latent images are formed by irradiating the photoconductors 25Y, 25M, 25C, and 25S of the portions 24Y, 24M, 24C, and 24S.

  As described above, in the image forming apparatus 1 according to the present exemplary embodiment, the color separation unit (data dividing unit) 74 of the color conversion unit 58 of the image processing unit 50 generates the predetermined color (in the present exemplary embodiment, generated by the black generating unit 73). K color) image data K is divided into dark black image data Dk and light black image data Lk, which are a plurality of (two in the present embodiment) divided image data having different shades, and an optical scanning device (divided scanning means). ) 27b converts one laser beam (writing beam) Lk emitted from one semiconductor laser (light source unit) 33 based on two image data Dk and Lk having different shades to the image data Dk and Lk. Each laser beam (divided writing beam) is divided into Lku and Lkl, and the respective laser beams Lku and Lkl are allowed to pass through the divided scanning optical path, and the corresponding photosensitive members 25Dk and 25Lk are not set for a predetermined time. Using the separation tables (distribution parameters) TB2, TB3, TB4 determined by the separation unit (image adjusting means) 74 based on the light transmission efficiency of the divided scanning optical path of the optical scanning device 27, Data values of grayscale image data Dk and Lk input to the semiconductor laser 33 are adjusted.

  Accordingly, the image data of a predetermined color (K color in this embodiment) is divided into two divided image data Dk and Lk having different shades, and one laser beam emitted from one semiconductor laser 33 is used as the optical scanning device 27b. When dividing the two laser beams Lku and Lkl and irradiating the corresponding photoreceptors 25Dk and 25Lk to form an image, the divided laser beams Lku and Lkl are divided according to the light transmission efficiency of the divided scanning light path. The data values of the divided image data Dk and Lk can be adjusted based on the plate tables TB2 to TB4, and a plurality (2 of laser beams Lk as one writing light emitted from the semiconductor laser 33 as one light source. To improve the image quality of an image formed by scanning the two photoconductors 25Dk and Lk by dividing them into laser beams Lku and Lkl, which are divided write lights. Kill.

  Further, the image forming apparatus 1 according to the present exemplary embodiment includes a data division processing step for dividing the image data K of a predetermined color (K color in the present exemplary embodiment) into two divided image data Dk and Lk having different shades. Laser light Lk, which is one writing light modulated and output based on two divided image data Dk and Lk having different shades from the semiconductor laser 33 which is a light source unit, is divided and written for each of the divided image data Dk and Lk. Division scan processing step of dividing the laser beams Lku and Lkl, which are light beams, and passing the laser beams Lku and Lkl through the divided scanning optical paths and scanning the corresponding photosensitive members 25Dk and 25Lk while shifting them for a predetermined time. And a separation table (distribution parameters) TB2 to TB4 determined on the basis of the light transmission efficiency of the divided scanning optical path, and input to the semiconductor laser 33 One of the divided image data Dk, running an image forming control method having an image adjustment processing step of adjusting the data values of Lk.

  Accordingly, the K-color image data is divided into two divided image data Dk and Lk having different shades, and one laser beam emitted from one semiconductor laser 33 is converted into two laser beams Lku and Lkl by the optical scanning device 27b. When an image is formed by irradiating the corresponding photosensitive members 25Dk and 25Lk and dividing, the divided laser beams Lku and Lkl are divided based on the separation tables TB2 to TB4 corresponding to the light transmission efficiency of the divided scanning optical path through which the divided laser beams Lku and Lkl pass. The data values of the image data Dk and Lk can be adjusted, and the laser light Lk which is one writing light emitted from the semiconductor laser 33 which is one light source is converted into the laser light Lku and Lkl which are two divided writing lights. It is possible to improve the image quality of an image formed by scanning the two photoconductors 25Dk and Lk.

  Further, the image forming apparatus 1 according to the present exemplary embodiment includes a data division process for dividing the K-color image data K into two divided image data Dk and Lk having different shades, and one light source unit. A laser beam Lk, which is one writing light modulated and output from the semiconductor laser 33 based on two divided image data Dk, Lk of different shades, is a divided writing light for each of the divided image data Dk, Lk. A divided scanning optical path that divides the light beams Lku and Lkl and causes the laser beams Lku and Lkl to pass through the divided scanning optical paths and scan the corresponding photosensitive members 25Dk and 25Lk while shifting them by a predetermined time; Two divided image data Dk input to the semiconductor laser 33 using the separation tables TB2 to TB4 determined based on the light transmission efficiency of Image adjustment processing and for adjusting the data value of Lk, are equipped with image formation control program for execution.

  Accordingly, the K-color image data is divided into two divided image data Dk and Lk having different shades, and one laser beam emitted from one semiconductor laser 33 is converted into two laser beams Lku and Lkl by the optical scanning device 27b. When an image is formed by irradiating the corresponding photosensitive members 25Dk and 25Lk and dividing, the divided laser beams Lku and Lkl are divided based on the separation tables TB2 to TB4 corresponding to the light transmission efficiency of the divided scanning optical path through which the divided laser beams Lku and Lkl pass. The data values of the image data Dk and Lk can be adjusted, and the laser light Lk which is one writing light emitted from the semiconductor laser 33 which is one light source is converted into the laser light Lku and Lkl which are two divided writing lights. It is possible to improve the image quality of an image formed by scanning the two photoconductors 25Dk and Lk.

  Further, in the image forming apparatus 1 according to the present embodiment, the optical scanning device (divided scanning unit) 27b performs the division with the high density of the two divided image data Dk and Lk with respect to the divided scanning optical path with high light transmission efficiency. A separation table TB2 in which the divided writing light Lku based on the image data Dk is allowed to pass and the separation unit 74 has a higher data value for the image data Dk corresponding to the laser light Lku that passes through the divided scanning light path with higher light transmission efficiency. TB4.

  Therefore, the divided image data Dk corresponding to the divided writing light Lku having a higher density that passes through the divided scanning optical path having a high light transmission efficiency can have a higher data value, and the density of the solid image can be appropriately maintained to improve the image quality. Can be improved.

  Furthermore, in the image forming apparatus 1 of the present embodiment, the image separation unit 74 has a darker image of two image data Dk and Lk having different shades as the difference in light transmission efficiency between the two divided scanning light paths is larger. Separation tables BT2 to BT4 having small gradation values for starting output of data Dk are used.

  Therefore, even when the solid density of the light density toner cannot be maintained, it can be compensated with the dark density toner, and the image quality can be improved.

  In the image forming apparatus 1 according to the present exemplary embodiment, the gradation value at which the color separation unit 74 starts to output the divided image data Dk having a high density is the gradation value at which the output of the divided image data Lk having the low density is saturated. The color separation tables BT2 to BT4, which have a small gradation value, are used.

  Therefore, an image with a light density can be appropriately compensated with an image with a high density, and the image quality can be improved.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Controller 3 Operation panel 4 PCI bus 5 Network I / F
6 USB I / F
7 IEEE1394 I / F
8 Engine part 8a Scanner 11 CPU
12 System memory (MEM-P)
13 North Bridge (NB)
14 South Bridge (SB)
15 ASIC
16 Local memory (MEM-C)
17 Hard disk (HDD)
12a ROM
12b RAM
20 Print engine 21, 22 Roller 23 Conveyor belt 24Y, 24M, 24C, 24S, 24Lk, 24Dk Image forming unit 25Y, 25M, 25C, 25S, 25Lk, 25Dk Photoconductor 26Y, 26M, 26C, 26S, 26Lk, 26Dk Charger 27a, 27b Optical scanning device 28Y, 28M, 28C, 28S, 28Lk, 28Dk Developing unit 29Y, 29M, 29C, 29S, 29Lk, 29Dk Transfer charger 30Y, 30M, 30C, 30S, 30Lk, 30Dk Cleaning unit 31Y, 31M, 31C , 31S Semiconductor laser 32u, 32l Polygon mirror 33 Semiconductor laser 34 Polygon part 34j Rotating shaft 34u, 34l Polygon mirror 35 Fixing part 41 Timing adjustment part 42 Collimating lens 43 Beam splitting Scientific element 43a Semi-transparent mirror 43b Reflecting surface 44 Aperture 45u, 45l Cylindrical lens lk Light black image data dk Dark black image data Lku, Lkl Laser light 50 Image processing unit 51 Scanner gamma correction unit 52 Input masking unit 53 Filter processing unit 54 Selector 55 Host I / F
56 Image development unit 57 Storage unit 58 Color conversion unit 59 Printer gamma correction unit 60 Halftone processing unit 71 Color correction unit 72 UCR unit 73 Black generation unit 74 Separation unit 75a, 75b Buffer

Japanese Patent Laying-Open No. 2005-092129

Claims (6)

Data dividing means for dividing image data of a predetermined color into a plurality of divided image data having different shades according to a value indicating the density of the image data of the predetermined color ;
One writing light modulated and emitted from one light source unit based on a plurality of divided image data having different shades is divided into divided writing light for each divided image data, and each divided writing light is divided. Split scanning means that passes on the scanning optical path and scans the corresponding photosensitive member by shifting for a predetermined time ,
The data dividing means adjusts and divides the data values of the plurality of divided image data input to the light source unit using a distribution parameter determined based on the light transmission efficiency of the divided scanning light path ,
The image forming apparatus according to claim 1, wherein the distribution parameter is information for designating a value indicating the density of the plurality of divided image data having different shades according to a value indicating the density of the image data of the predetermined color . The divided scanning means includes
The divided scanning light path having a higher light transmission efficiency allows the divided writing light by the divided image data having a higher density among the plurality of divided image data to pass therethrough,
The distribution parameter is:
The image forming apparatus according to claim 1, wherein the divided image data corresponding to the divided writing light that passes through the divided scanning optical path having a high light transmission efficiency is a distribution parameter that increases a data value. The distribution parameter is:
The distribution parameter is such that the larger the difference in the light transmission efficiency between the plurality of divided scanning optical paths, the smaller the gradation value at which the output of the divided image data having a high density among the plurality of divided image data having different shades is started. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The distribution parameter is:
The gradation value at which the output of the divided image data with low density is saturated is a gradation value as small as the gradation value at which the output of the divided image data with high density is started. Item 4. The image forming apparatus according to Item 3. A data division processing step for dividing image data of a predetermined color into a plurality of divided image data having different shades according to a value indicating the density of the image data of the predetermined color ;
One writing light modulated and output based on a plurality of divided image data of different shades from one light source unit is divided into divided writing light for each divided image data, and each divided writing light is divided. Divided scanning processing steps that pass on the scanning optical path and scan the corresponding photoreceptors for a predetermined time , and
The data dividing processing step, by using the distribution parameter determined based on the light transmission efficiency of the divided scanning beam path, in the step of dividing by adjusting the data value of the plurality of the divided image data to be input to the light source unit Yes,
The image forming control method , wherein the distribution parameter is information for designating a value indicating the density of the plurality of divided image data having different shades according to a value indicating the density of the image data of the predetermined color . On the computer,
A data division process for dividing image data of a predetermined color into a plurality of divided image data having different shades according to a value indicating the density of the image data of the predetermined color ;
One writing light modulated and output based on a plurality of divided image data of different shades from one light source unit is divided into divided writing light for each divided image data, and each divided writing light is divided. An image formation control program that executes a divided scanning process that scans a predetermined time period on a corresponding photosensitive member by passing through a scanning optical path ;
The data dividing process is a process of adjusting and dividing the data values of the plurality of divided image data input to the light source unit using a distribution parameter determined based on the light transmission efficiency of the divided scanning light path . ,
The distribution parameter is information for designating a value indicating the density of the plurality of divided image data having different shades according to a value indicating the density of the image data of the predetermined color .

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