Image forming device

Abstract

To reduce memory capacities that are required for correcting an inclination of an image and suppress deterioration in processing capability.SOLUTION: A memory control part executes: writing-in processing in which line data are divided into a plurality of block data in accordance with an inclination of an image in a sub scanning direction with respect to a main scanning direction in a direction in which a plurality of light emitting elements are arranged and the plurality of block data are shifted by one line and then are written in a main memory; and reading-out processing in which the block data are read out from the main memory. A correction control part divides the block data read out in the reading-out processing into first data formed of pixels in which line shift is caused by the inclination and pixels ahead of such pixels and second data formed of pixels behind the pixels in which the line shift is caused, stores the second data in a correction buffer, and outputs the first data together with the second data ahead thereof by one block stored in the correction buffer to an exposing head.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] An embodiment of the present invention relates to an image forming apparatus. [Background technology]

[0002] The exposure head is an image forming member for selectively exposing the outer peripheral surface of a uniformly charged photosensitive drum to light to form an image. The exposure head is used in an image forming apparatus using an electrophotographic process. The image forming apparatus is, for example, a printer, a copier, a multifunction peripheral (MFP), etc.

[0003] The exposure head has a light emitting element row in which a plurality of light emitting elements are arranged in one direction. The light emitting elements are, for example, light emitting diodes (LEDs). The light emitting elements may be, for example, organic light emitting diodes (OLEDs), that is, organic electroluminescence (EL).

[0004] The exposure head is attached near the photosensitive drum so that the row of light emitting elements is arranged along the longitudinal direction of the photosensitive drum. The longitudinal direction of the photosensitive drum is the main scanning direction of image formation. The photosensitive drum rotates in the sub-scanning direction. Therefore, if the exposure head is attached parallel to the main scanning direction, an image is formed on the photosensitive drum parallel to the main scanning direction. However, the exposure head is not necessarily attached parallel to the main scanning direction. Due to the influence of the accuracy of the head attachment part, the exposure head may be attached at an angle inclined in the sub-scanning direction with respect to the main scanning direction. In that case, an image inclined in the sub-scanning direction with respect to the main scanning direction is formed on the photosensitive drum. For this reason, it is necessary to correct the inclination of the image.

[0005] Conventionally, there is a method for correcting the inclination of an image by shifting the read address when reading image data expanded on the main memory in accordance with the inclination of the exposure head. However, this method requires frequent access to the main memory, which results in a problem of reduced data transfer efficiency and reduced processing power.

[0006] Another method is to first load multiple lines of image data corresponding to the tilt from the main memory into a high-speed memory, and then delay the output of the corresponding pixel data according to the tilt of the exposure head. However, this method requires large memory resources, which increases costs. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2009-223141 A [Patent Document 2] JP 2001-352445 A Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved by the embodiments of the present invention is to provide an image forming apparatus capable of reducing the memory capacity required to correct the inclination of an image and suppressing a decrease in processing capacity. [Means for solving the problem]

[0009] In one embodiment, the image forming apparatus includes an image carrier, an exposure head, a developing unit, a main memory, and a memory control unit. A read-side buffer; and a correction control unit. The exposure head irradiates the image carrier with light from a plurality of light-emitting elements arranged in one direction to form a latent image on the image carrier based on image data. The developing unit develops the latent image on the image carrier by applying developer to the latent image. The main memory expands and stores the image data as a plurality of line data in the main scanning direction. The memory control unit adjusts the image data in accordance with the inclination of the arrangement direction of the plurality of light-emitting elements in the sub-scanning direction with respect to the main scanning direction. The number of blocks is one less than the number of lines, which is the amount of deviation in the sub-scanning direction. The line data is divided, and a write process is executed in which the plurality of block data are written into the main memory while being shifted by one line, and a read process is executed in which the block data is read from the main memory. The read-side buffer stores the block data read by the read process. The correction control unit is Each of the data stored in the read buffer The block data is divided into first data consisting of the pixel where line shift occurs due to tilt and the pixels before that pixel, and second data consisting of the pixels after the pixel where line shift occurs, the second data is stored in a correction buffer, and the first data is output to the exposure head together with the second data of the previous block stored in the correction buffer. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of a multifunction peripheral according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a configuration of a main part of an image forming unit in the multifunction peripheral; [Diagram 3] FIG. 2 is a block diagram showing a main part of a circuit configuration in the multifunction peripheral. [Figure 4] FIG. 4 is a circuit diagram for explaining a tilt correction function of image data provided in the multifunction peripheral. [Diagram 5] FIG. 4 is a schematic diagram for explaining the arrangement direction of light-emitting elements in the exposure head. [Figure 6] FIG. 4 is a schematic diagram showing an example of image data before being written to a main memory. [Figure 7] FIG. 4 is a schematic diagram showing an example of image data written to a main memory. [Figure 8] FIG. 11 is a schematic diagram showing an example of image data corrected by a tilt correction function. [Figure 9] 4 is a flowchart showing the main steps of a data write process related to a memory control unit. [Figure 10] 4 is a flowchart showing a main procedure of a data read process related to a memory control unit. [Figure 11] 11 is a flowchart showing the main steps of a data gradient adjustment process performed by a data conversion unit. [Figure 12] 11 is a flowchart showing the main steps of a data inclination adjustment process related to a correction control unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of an image forming apparatus will be described with reference to the drawings. In this embodiment, a multifunction peripheral using four color toners is taken as an example of an image forming apparatus.

[0012] FIG. 1 is a schematic diagram showing a schematic configuration of a multifunction machine 1 according to this embodiment. The multifunction machine 1 conveys a print medium P and forms an image on the print medium P by an electrophotographic process. The print medium P is also called a recording medium, a transfer medium, paper, etc. The multifunction machine 1 receives toner from a toner cartridge 2 and forms an image on the print medium P with the received toner. The toner is, for example, four color toners of yellow, magenta, cyan, and black. The combination of color toners is not limited to this. Other colors may be combined. Also, instead of combining multiple color toners, a single color toner may be used.

[0013] As shown in FIG. 1, the multifunction device 1 includes a housing 11, a communication interface 12, a system controller 13, multiple paper trays 14, a paper output tray 15, a conveying section 16, an image forming section 17, a fixing unit 18, a scanner section 19, and a control panel 20.

[0014] The housing 11 is the main body of the multifunction device 1. The housing 11 houses, for example, a communication interface 12, a system controller 13, a plurality of paper trays 14, a conveying unit 16, an image forming unit 17, and a fixing unit 18. A part of the upper surface of the housing 11 serves as a paper output tray 15.

[0015] The communication interface 12 is an interface for communicating with other devices connected via a network. The communication interface 12 is used for communication with an external device. The external device is, for example, a higher-level device having a function of generating print data. The multifunction device 1 forms an image on a print medium P according to the print data generated by the higher-level device. The communication interface 12 is, for example, configured with a LAN connector or the like. The communication interface 12 may be one that performs wireless communication with other devices according to standards such as Bluetooth (registered trademark) or Wi-fi (registered trademark).

[0016] The system controller 13 functions as a control unit of the multifunction device 1. The system controller 13 is connected to the communication interface 12. The system controller 13 generates a print job based on print data acquired from an external device via the communication interface 12, for example. The print job includes image data indicating an image to be formed on a print medium P. The image data may be data for forming an image on one sheet of print medium P, or may be data for forming an image on multiple sheets of print media P. The print job may include information indicating color printing or monochrome printing.

[0017] The system controller 13, which has generated the print job, controls the operations of the transport unit 16, the image forming unit 17, and the fixing unit 18 to form an image of the image data included in the print job on the print medium P. Specifically, the system controller 13 controls the transport of the print medium P by the transport unit 16, the formation of an image on the print medium P by the image forming unit 17, and the fixing of the image on the print medium P by the fixing unit 18. In this way, the system controller 13 also functions as an engine controller for the multifunction device 1.

[0018] The multifunction device 1 may be configured to include an engine controller separate from the system controller 13. In this case, the engine controller controls at least one of the following: transportation of the print medium P by the transport unit 16, image formation on the print medium P by the image forming unit 17, and fixing of the image on the print medium P by the fixing unit 18. The system controller 13 supplies the engine controller with information necessary for control in the engine controller.

[0019] Each of the multiple paper trays 14 is a cassette that stores print media P. The paper trays 14 are configured to be able to supply print media P from outside the housing 11. For example, the paper trays 14 are configured to be able to be pulled out from the housing 11.

[0020] The paper discharge tray 15 is a tray that receives the print medium P discharged from the multifunction device 1. The transport unit 16 is a mechanism that transports the print medium P within the multifunction device 1. As shown in FIG. 1, the transport unit 16 has multiple transport paths. Specifically, the transport unit 16 has a paper feed transport path 31 and a paper discharge transport path 32. The paper feed transport path 31 and the paper discharge transport path 32 are composed of multiple rollers, multiple guides, etc. The multiple rollers transport the print medium P by rotating due to power transmitted from the drive mechanism. The multiple guides control the transport direction of the print medium P transported by the rollers.

[0021] The paper feed conveying path 31 takes in the print medium P from the paper tray 14 and supplies the taken-in print medium P to the image forming unit 17. The paper feed conveying path 31 is provided with a plurality of pickup rollers 33 corresponding to each paper tray 14. Each pickup roller 33 takes in the print medium P from the respective paper tray 14 into the paper feed conveying path 31.

[0022] The discharge conveyance path 32 is a conveyance path that discharges the print medium P, on which an image has been formed by the image forming unit 17, from the housing 11. The print medium P discharged by the discharge conveyance path 32 is supported by the discharge tray 15.

[0023] The image forming unit 17 has a configuration for forming an image on the print medium P. The image forming unit 17 will be described in detail later.

[0024] The fixing unit 18 has a heat roller 34 and a pressure roller 35. The fixing unit 18 heats the print medium P transported through the paper discharge transport path 32 to a predetermined temperature with the heat roller 34, and further applies pressure with the pressure roller 35, thereby fixing the image transferred to the print medium P to the print medium P.

[0025] Scanner unit 19 is a device that reads a document and converts it into image data, and is installed on the upper part of housing 11. Scanner unit 19 is equipped with an automatic document feeder 21, and is also capable of reading documents transported by this automatic document feeder 21.

[0026] The control panel 20 includes a touch panel 22 and a keyboard 23. The touch panel 22 is formed by stacking a display such as a liquid crystal display or an organic EL display, and a touch sensor that detects touch input. On the display, information to be notified to the user of the multifunction device 1 is displayed, such as images for setting various functions of the multifunction device 1 and an image showing the remaining toner amount.

[0027] The keyboard 23 includes various keys for operation by the user of the multifunction device 1. For example, the keyboard 23 includes a numeric keypad, a power key, a paper feed key, function keys, etc. Each key may be referred to as a button. In this manner, the touch panel 22 and the keyboard 23 function as input devices for the multifunction device 1. The display included in the touch panel 22 functions as a display device for the multifunction device 1.

[0028] Next, the image forming unit 17 will be described. As shown in FIG. 1, the image forming section 17 includes a plurality of process units 41 and a transfer unit 42. Each process unit 41 is a unit for forming a toner image. Each process unit 41 is provided for each type of toner. For example, from the left in FIG. 1, each process unit 41 corresponds to a corresponding color toner, i.e., yellow, magenta, cyan, and black. Each process unit 41 includes a toner cartridge 2 having a corresponding color toner.

[0029] Fig. 2 is a schematic diagram showing the configuration of the main parts of the image forming section 17. Each toner cartridge 2 and each process unit 41 have the same configuration. Therefore, Fig. 2 shows one toner cartridge 2 and one process unit 41 as an example.

[0030] First, a description will be given of the toner cartridge 2. As shown in FIG.

[0031] The toner storage container 51 is a container that stores toner. The toner sending mechanism 52 is a mechanism that sends out the toner in the toner storage container 51. The toner sending mechanism 52 is, for example, a screw provided in the toner storage container 51. The toner in the toner storage container 51 is sent out by the rotation of the screw.

[0032] The toner storage container 51 is loaded into the loading unit 60. The loading unit 60 is a module into which the toner cartridge 2 filled with toner is attached. The loading unit 60 includes a toner supply motor 61. The loading unit 60 also includes a connector that connects the memory 53 of the toner cartridge 2 to the system controller 13.

[0033] When the toner cartridge 2 is loaded into the loading section 60, the toner supply motor 61 is connected to the toner sending mechanism 52 of the toner cartridge 2. The toner supply motor 61 drives the toner sending mechanism 52 under the control of the system controller 13. When the toner supply motor 61 drives the toner sending mechanism 52, the toner in the toner storage container 51 is supplied to the developing device 75 described below. The memory 53 of the toner cartridge 2 stores information such as the number of times that the toner has been supplied to the developing device 75 by driving the toner sending mechanism 52, and the date and time of supply.

[0034] Next, a description will be given of the process unit 41. As shown in FIG.

[0035] The photosensitive drum 71 is a photosensitive member including a cylindrical drum and a photosensitive layer formed on the outer peripheral surface of the drum. The photosensitive drum 71 rotates at a constant speed by power transmitted from a drive mechanism. The photosensitive drum 71 is an example of an image carrier.

[0036] The cleaner 72 has a blade 721 that comes into contact with the surface of the photosensitive drum 71. The cleaner 72 uses the blade 721 to remove toner remaining on the surface of the photosensitive drum 71.

[0037] The charging unit 73 is a device that uniformly charges the surface of the photosensitive drum 71. For example, the charging unit 73 applies a grid bias voltage output from a grid electrode 731 to the photosensitive drum 71, thereby charging the photosensitive drum 71 to a uniform negative potential. Such a charging unit 73 is also called a charging charger.

[0038] The exposure head 74 includes a plurality of light-emitting elements. The light-emitting elements are, for example, laser diodes (LD), light-emitting diodes (LED), organic electroluminescence (OLED), etc. The plurality of light-emitting elements are arranged in the main scanning direction, which is a direction parallel to the rotation axis of the photosensitive drum 71. Each light-emitting element is configured to irradiate light to one point on the photosensitive drum 71.

[0039] The exposure head 74 irradiates the surface of the charged photosensitive drum 71 with light from a plurality of light-emitting elements arranged in the main scanning direction, thereby forming a latent image of one line on the photosensitive drum 71. Furthermore, the exposure head 74 forms a latent image of multiple lines by continuously irradiating the rotating photosensitive drum 71 with light.

[0040] The developing device 75 is a device that forms a toner image on the photosensitive drum 71 by attaching toner to the photosensitive drum 71. The developing device 75 includes a developer container 81, a stirring mechanism 82, a developing roller 83, a doctor blade 84, an auto toner control (ATC) sensor 85, and the like.

[0041] The developer container 81 is a container that contains a developer containing toner and a carrier. The developer container 81 receives the toner sent out from the toner cartridge 2 by the toner sending mechanism 52. The carrier is contained in the developer container 81 when the developing unit 75 is manufactured.

[0042] The stirring mechanism 82 is disposed inside the developer container 81. The stirring mechanism 82 stirs the toner and carrier inside the developer container 81. The developing roller 83 rotates within the developer container 81 to cause the developer to adhere to the surface of the roller. The doctor blade 84 is a member disposed at a predetermined distance from the surface of the developing roller 83. The doctor blade 84 removes a portion of the developer adhering to the surface of the rotating developing roller 83. As a result, a layer of developer is formed on the surface of the developing roller 83, the thickness of which corresponds to the distance between the doctor blade 84 and the surface of the developing roller 83.

[0043] The ATC sensor 85 is, for example, a magnetic flux sensor having a coil and detecting a voltage value generated in the coil. The detected voltage of the ATC sensor 85 changes depending on the density of the magnetic flux from the toner in the developer container 81. That is, the ATC sensor 85 detects a voltage corresponding to the concentration ratio of the toner to the carrier in the developer container 81. Such a concentration ratio is called a toner concentration. The system controller 13 can determine the toner concentration in the developer container 81 based on the detected voltage of the ATC sensor 85.

[0044] As described above, when light is irradiated from the exposure head 74 onto the surface of the photosensitive drum 71 charged by the charging unit 73, a latent image is formed. Thereafter, when the layer of developer formed on the surface of the developing roller 83 in the developing device 75 approaches the surface of the photosensitive drum 71, the toner contained in the developer adheres to the latent image formed on the surface of the photosensitive drum 71. As a result, a toner image is formed on the surface of the photosensitive drum 71. That is, the exposure head 74 and the developing device 75 constitute an image forming unit 76.

[0045] The transfer unit 42 is configured to transfer the toner image formed on the surface of the photosensitive drum 71 to the print medium P. As shown in Figures 1 and 2, the transfer unit 42 includes, for example, a transfer belt 91, a secondary transfer opposing roller 92, a plurality of primary transfer rollers 93, and a secondary transfer roller 94.

[0046] The transfer belt 91 is an endless belt wound around a secondary transfer opposing roller 92 and a plurality of winding rollers. The back surface of the transfer belt 91, which is the inner surface, contacts the secondary transfer opposing roller 92 and the plurality of winding rollers, and the front surface, which is the outer surface, faces the photosensitive drum 71 of the process unit 41.

[0047] The secondary transfer opposing roller 92 rotates by power transmitted from a drive mechanism to transport the transfer belt 91. The secondary transfer opposing roller 92 rotates counterclockwise in FIG. 1. This rotation transports the transfer belt 91, which is an endless belt, so that it rotates counterclockwise in FIG. 1. The multiple winding rollers are configured to be freely rotatable. The multiple winding rollers rotate in accordance with the movement of the transfer belt 91 by the secondary transfer opposing roller 92.

[0048] A plurality of primary transfer rollers 93 are provided for each process unit 41. The plurality of primary transfer rollers 93 are provided so as to face the photosensitive drums 71 of the corresponding process units 41, respectively. Specifically, the plurality of primary transfer rollers 93 are provided at positions facing the photosensitive drums 71 of the corresponding process units 41 with the transfer belt 91 interposed therebetween. The primary transfer rollers 93 come into contact with the inner circumferential surface side of the transfer belt 91, and displace the transfer belt 91 towards the photosensitive drum 71. This displacement causes the surface of the transfer belt 91 to come into contact with the photosensitive drum 71.

[0049] The secondary transfer roller 94 is provided at a position facing the secondary transfer opposing roller 92. The secondary transfer roller 94 contacts and applies pressure to the surface of the transfer belt 91 that is conveyed along the circumferential surface of the secondary transfer opposing roller 92. This contact and pressure forms a transfer nip where the secondary transfer roller 94 and the surface of the transfer belt 91 are in close contact with each other.

[0050] The secondary transfer roller 94 and the secondary transfer opposing roller 92 rotate to sandwich and transport the print medium P supplied from the paper feed transport path 31. As a result, the print medium P passes through the transfer nip. The secondary transfer roller 94 presses the print medium P passing through the transfer nip against the surface of the transfer belt 91.

[0051] In the transfer unit 42 configured as described above, when the surface of the transfer belt 91 comes into contact with the photosensitive drum 71, the toner image formed on the surface of the photosensitive drum 71 is transferred to the surface of the transfer belt 91. As shown in FIG. 1, when the image forming section 17 includes a plurality of process units 41, the toner images are transferred to the transfer belt 91 from the photosensitive drums 71 of the plurality of process units 41, respectively. The toner image transferred to the surface of the transfer belt 91 is transported to the transfer nip by the transfer belt 91. At this time, if a print medium P is present in the transfer nip, the toner image transferred to the surface of the transfer belt 91 is transferred to the print medium P at the transfer nip.

[0052] Next, the circuit configuration of the multifunction device 1 will be described. 3 is a block diagram showing the main parts of the circuit configuration of the multifunction device 1. As shown in the figure, the multifunction device 1 configures the circuit by connecting a system controller 13 with a communication interface 12, an image forming unit 17, a fixing unit 18, a scanner unit 19, a control panel 20, a motor 30, etc., via signal lines.

[0053] The system controller 13 includes a processor 131, a ROM (Read Only Memory) 132, a RAM (Random Access Memory) 133, and an auxiliary storage device 134. The system controller 13 configures a computer by connecting the processor 131, the ROM 132, the RAM 133, and the auxiliary storage device 134 with signal lines.

[0054] The processor 131 corresponds to the central part of the computer. The processor 131 controls each part to realize various functions of the multifunction device 1 according to an operating system or an application program. The processor 131 is, for example, a CPU (Central Processing Unit).

[0055] The ROM 132 and the RAM 133 correspond to the main memory of the computer. The ROM 132 is a non-volatile memory area, and the RAM 133 is a volatile memory area. The ROM 132 stores an operating system or an application program. The ROM 132 also stores data required for the processor 131 to execute processes for controlling each unit. The RAM 133 is used as a work area where data is appropriately rewritten by the processor 131.

[0056] The auxiliary storage device 134 corresponds to the auxiliary storage portion of the computer. As the auxiliary storage device 134, for example, a well-known storage device such as an EEPROM (Electric Erasable Programmable Read-Only Memory), an HDD (Hard Disc Drive), or an SSD (Solid State Drive) is used alone or in combination. The auxiliary storage device 134 stores data used by the processor 131 when performing various processes and data generated by the processes in the processor 131. The auxiliary storage device 134 may also store application programs.

[0057] The system controller 13 connects the toner cartridge 2, photosensitive drum 71, cleaner 72, charging unit 73, image forming unit (exposure head 74, developing device 75) 76, and transfer unit (transfer belt 91, secondary transfer opposing roller 92, primary transfer roller 93, and secondary transfer roller 94) 42 of the image forming section 17 with signal lines. The system controller 13 then controls the toner cartridge 2, photosensitive drum 71, cleaner 72, charging unit 73, and image forming unit 76 provided for each process unit 41, as well as the transfer unit 42 and fixing unit 18, to form an image on the print medium P.

[0058] The motor 30 includes a first motor used in a drive mechanism that drives the conveying unit 16, a second motor used in a drive mechanism that rotates the photosensitive drum 71, and a third motor used in a drive mechanism that rotates the secondary transfer opposing roller 92. A plurality of second motors are provided corresponding to the photosensitive drums 71 provided in the plurality of process units 41, respectively. The motor 30 may include a motor used in a drive mechanism other than the above-mentioned drive mechanisms. The motor 30 is, for example, a brushless motor. The motor 30 may be a brush motor.

[0059] In each process unit 41, the exposure head 74 is attached by a head attachment part so that the light emitting element row faces the photosensitive drum 71. In principle, the light emitting element row is attached so as to be parallel to the main scanning direction H, which is the longitudinal direction of the photosensitive drum 71, as shown by the solid line La in FIG. 5. However, in reality, due to the accuracy of the head attachment part, the light emitting element row may be attached so as to be inclined in the sub scanning direction V, which is a direction perpendicular to the main scanning direction H, as shown by the dashed line Lb or dashed line Lc in FIG. 5. If the light emitting element row is inclined in the sub scanning direction V, the latent image formed line by line on the photosensitive drum 71 by the exposure head 74 is inclined in the sub scanning direction V. As a result, an image inclined in the sub scanning direction V with respect to the main scanning direction H is formed on the printing medium P.

[0060] This embodiment provides a multifunction printer 1 that can form an image on a printing medium P that is parallel to the main scanning direction H by using an image data inclination correction function, even if the light-emitting element row of the exposure head 74 is installed at an angle in the secondary scanning direction relative to the main scanning direction H of the photosensitive drum 71.

[0061] Next, the inclination correction function of the image data will be described. In the following, a case where the light emitting element row of the exposure head 74 is installed in one process unit 41 so as to be inclined in the sub scanning direction with respect to the main scanning direction H of the photosensitive drum 71 will be exemplified. A similar measure can be taken even when the light emitting element row of the exposure head 74 is installed in another process unit 41 so as to be inclined.

[0062] 4 is a circuit diagram for explaining the inclination correction function of image data. This circuit is configured in the system controller 13. That is, the system controller 13 configures a main memory 201, a work memory 202, a write side buffer 203, a read side buffer 204, and a correction buffer 205 using the RAM 133. The system controller 13 also stores a control program in the ROM 132 or the auxiliary storage device 134 so that the processor 131 has a configuration including a memory control unit 211, a write address generation unit 212, a read address generation unit 213, a data conversion unit 214, a correction control unit 215, and a selector 216.

[0063] The main memory 201 is an area for expanding and storing image data as a plurality of line data in the main scanning direction.

[0064] The work memory 202 has a first setting area 221, a second setting area 222, a third setting area 223, a fourth setting area 224, a fifth setting area 225, a sixth setting area 226, a seventh setting area 227, and an eighth setting area 228. The work memory 202 also has a first counter area 231, a second counter area 232, a third counter area 233, a fourth counter area 234, a fifth counter area 235, a sixth counter area 236, a seventh counter area 237, and an eighth counter area 238.

[0065] In the first setting area 221, the number of lines LINE of image data for one page is set. In the second setting area 222, the number of pixels PIX for one line is set. One pixel is 1 byte (8 bits). In the third setting area 223, the number of pixels WT for the write transfer unit is set. In the fourth setting area 224, the number of pixels RT for the read transfer unit is set. In the fifth setting area 225, the line shift amount LINEZ[i] is set. In the sixth setting area 226, the pixel number LINEP[k] of the line shift occurrence position is set. The pixel number is a consecutive number starting with the number of the first pixel of the line data as "0". Therefore, the pixel number of the last pixel of the line data is "PIX-1". In the seventh setting area 227, the start address STA is set. In the eighth setting area 228, the line addition address LINEAD is set. The items of the setting areas 221 to 228 will be made clear in the operation explanation described later.

[0066] A write side pixel counter WPCNT is set in the first counter area 231. A write side line counter WLCNT is set in the second counter area 232. A read side pixel counter RPCNT is set in the third counter area 233. A read side line counter RLCNT is set in the fourth counter area 234. A correction pixel counter PPCNT is set in the fifth counter area 235. A write time counter i is set in the sixth counter area 236. A read time counter j is set in the seventh counter area 237. A correction time counter k is set in the eighth counter area 238. The items in each counter area 231 to 238 will be made clear in the operation explanation given below.

[0067] The write-side buffer 203 is an area for storing image data before it is written to the main memory 201. The write-side buffer 203 stores image data consisting of a plurality of lines of data for each line of data.

[0068] The read buffer 204 is an area for storing image data read out from the main memory 201. The read buffer 204 stores image data consisting of a plurality of lines of data for each line of data.

[0069] The correction buffer 205 is an area for temporarily storing data delayed by the tilt correction function, which will be described later.

[0070] In this configuration, a right-side main scanning signal WHDEN and a right-side sub-scanning signal WVDEN are input to the work memory 202, the right-side buffer 203, and the memory control unit 211. Image data WDATA is also input to the right-side buffer 203. A line reference signal HSYNC is input to the memory control unit 211 and the data conversion unit 214. Image data RDATA is also input to the data conversion unit 214. A read-side main scanning signal RHDEN and a read-side sub-scanning signal RVDEN are output from the data conversion unit 214 to the exposure head 74. Image data PDATA is output from the selector 216 to the exposure head 74.

[0071] The image data WDATA is image data before being written to the main memory 201. The image data RDATA is image data read from the main memory 201. The image data PDATA is image data corrected by the tilt correction function.

[0072] The image data WDATA is included in the print job. The right side main scanning signal WHDEN, the right side sub-scanning signal WVDEN, the line reference signal HSYNC, the read side main scanning signal RHDEN, and the read side sub-scanning signal RVDEN are signals controlled by the processor 131 in accordance with the print job.

[0073] Next, the operation of the system controller 13 regarding the tilt correction function will be described with reference to FIGS. Fig. 6 is a schematic diagram showing an example of image data WDATA before being written to the main memory 201. Fig. 7 is a schematic diagram showing an example of image data RDATA written to the main memory 201. Fig. 8 is a schematic diagram showing an example of image data PDATA corrected by the tilt correction function. Fig. 9 is a flow chart showing the main steps of a process for writing data to the main memory 201. Fig. 10 is a flow chart showing the main steps of a process for reading data from the main memory 201. Figs. 11 and 12 are flow charts showing the main steps of a process for adjusting the tilt of data read from the main memory 201.

[0074] 6, the image data WDATA has a line count LINE of one page of "L" and a pixel count PIX of one line of "T." In this case, the line count LINE is set to "L" in the first setting area 221. The pixel count PIX is set to "T" in the second setting area 222.

[0075] As an example, assume that the light emitting element row of the exposure head 74 is tilted by five lines in the sub-scanning direction V, as shown by the dashed line Ld in Fig. 6. In this case, the memory control unit 211 limits the misalignment to four lines, one line less, and writes one line of data to the main memory 201. To achieve this, one line of image data is divided into four pieces of image data, each having at least the number of pixels "T / 4", and written to the main memory 201. Therefore, "T / 4" is set in the third setting area 223 as the number of pixels WT of the write transfer unit.

[0076] Further, the displacement amount LINEZ[0], displacement amount LINEZ[1], displacement amount LINEZ[2], and displacement amount LINEZ[3] of the image data divided into four by the number of pixels "T / 4" are set in the fifth setting area 225. The displacement amount is based on the image data including the first pixel. That is, in the fifth setting area 225, "0" is set as the displacement amount LINEZ[0], "1" is set as the displacement amount LINEZ[1], "2" is set as the displacement amount LINEZ[2], and "3" is set as the displacement amount LINEZ[3].

[0077] Furthermore, for each of the image data divided into four by the number of pixels "T / 4", pixel numbers LINEP[0], LINEP[1], LINEP[2], and LINEP[3] at positions where line deviation occurs are obtained and set in the sixth setting area 226. For example, in the sixth setting area 226, "a" is set as pixel number LINEP[0], "b" is set as pixel number LINEP[1], "c" is set as pixel number LINEP[2], and "d" is set as pixel number LINEP[3].

[0078] On the other hand, when the memory control unit 211 reads one line of data from the main memory 201, it reads it out fewer times than when writing. For example, if the data is divided into two parts and read out, one line of image data may be read out from the main memory 201 as image data of at least the number of pixels "T / 2". Therefore, in the fourth setting area 224, the number of pixels RT of the read transfer unit is set to "T / 2". In other words, the number of pixels RT is the number of pixels of the image data read out in one time.

[0079] In addition, a start address STA of the main memory 201 is set in a seventh setting area 227, and a line addition address LINEAD of the main memory 201 is set in an eighth setting area 228. The start address STA and the line addition address LINEAD are arbitrary. In the following, the start address STA is set to "10000", and the line addition address LINEAD is set to "1000". Furthermore, the number of pixels WT in a write transfer unit is set to "100", and the number of pixels RT in a read transfer unit is set to "200".

[0080] In this manner, when the data required for correction is set in the first to eighth setting areas 221 to 228 and the image data WDATA contained in the print job is input to the write-side buffer 203, the memory control unit 211 starts information processing according to the procedure shown in the flowchart of FIG. 9.

[0081] In the following, image data obtained by dividing one line of image data by the number of pixels “T / 4” is referred to as block data. Therefore, the number of pixels WT in the write transfer unit can also be referred to as the number of pixels in block data.

[0082] The memory control unit 211 waits for the right-side sub-scanning signal WVDEN to become valid as ACT1. When the right-side sub-scanning signal WVDEN becomes valid, the memory control unit 211 resets the right-side line number counter WLCNT to "0" as ACT2. The memory control unit 211 resets the write-time counter i to "0" as ACT3. The memory control unit 211 resets the right-side pixel number counter WPCNT to "0" as ACT4.

[0083] The memory control unit 211 waits for the right side main scanning signal WHDEN to become valid as ACT5. When the right side main scanning signal WHDEN becomes valid, the memory control unit 211 calculates the write address WADR as ACT6. The write address WADR is calculated by the following arithmetic expression (1) using the start address STA, the line addition address LINEAD, the right side line number counter WLCNT, the deviation amount LINEZ[i] corresponding to the write time counter i, the number of pixels WT in the write transfer unit, and the write time counter i.

[0084] WADR=STA+LINEAD*(WLCNT+LINEZ(i))+WT*i …(1) The memory control unit 211 counts up the write-side pixel counter WPCNT by "1" in ACT7. The memory control unit 211 checks whether the write-side pixel counter WPCNT reaches the number of pixels PIX of one line in ACT8. If the write-side pixel counter WPCNT has not reached the number of pixels PIX of one line, the memory control unit 211 checks whether the write-side pixel counter WPCNT matches the multiple [(i+1)*WT] of the number of pixels WT of the write transfer unit in ACT9. If the write-side pixel counter WPCNT does not match the multiple [(i+1)*WT] of the number of pixels WT of the write transfer unit, the memory control unit 211 returns to ACT7. That is, the memory control unit 211 counts up the write-side pixel counter WPCNT by "1". Then, the memory control unit 211 checks whether the write side pixel counter WPCNT has reached the number of pixels PIX in one line, and if not, whether it matches a multiple [(i+1)*WT] of the number of pixels WT in the write transfer unit.

[0085] In ACT9, when the write-side pixel counter WPCNT matches the multiple [(i+1)*WT] of the pixel number WT of the write transfer unit, the memory control unit 211 writes the image data of the pixel number [(i+1)*WT] input to the write-side buffer 203, that is, the block data, to an area specified by the write address WADR of the main memory 201 in ACT10. The memory control unit 211 counts up the write time counter i by "1" in ACT11. Then, the memory control unit 211 returns to ACT6, and executes the processes from ACT6 onwards in the same manner as described above.

[0086] As a result, first, the first block data [1-1] of the four divisions of the line data of the first line is stored in an area specified by the write address WADR=10000+1000*(0+0)+100*0=10000 of the main memory 201. Next, the second block data [1-2] of the first line is stored in an area specified by the write address WADR=10000+1000*(0+1)+100*1=11100 of the main memory 201. Next, the third block data [1-3] of the first line is stored in an area specified by the write address WADR=10000+1000*(0+2)+100*2=12200 of the main memory 201. After this, the right side pixel number counter WPCNT reaches the number of pixels PIX of one line.

[0087] When the memory control unit 211 confirms in ACT8 that the write-side pixel counter WPCNT has reached the number of pixels PIX of one line, it writes the remaining data of the one line data input to the write-side buffer 203 in ACT12 to the area of ​​the write address WADR of the main memory 201. As a result, the fourth block data [1-4] of the first line is stored in the area specified by the write address WADR=10000+1000*(0+3)+100*3=13300 of the main memory 201.

[0088] The memory control unit 211 checks whether the write side line number counter WLCNT is smaller than the value (LINE-1) obtained by subtracting "1" from the line number LINE in ACT13. If the write side line number counter WLCNT is smaller than the value (LINE-1), the memory control unit 211 counts up the write side line number counter WLCNT by "1" in ACT14. Then, the memory control unit 211 returns to ACT3, and executes the processes from ACT3 onwards in the same manner as described above.

[0089] As a result, the first block data [2-1] of the four divisions of the line data of the second line is stored in an area specified by the write address WADR=10000+1000*(1+0)+100*0=11000 of the main memory 201. Next, the second block data [2-2] of the second line is stored in an area specified by the write address WADR=10000+1000*(1+1)+100*1=12100 of the main memory 201. Next, the third block data [2-3] of the second line is stored in an area specified by the write address WADR=10000+1000*(1+2)+100*2=13200 of the main memory 201. Next, the fourth block data [2-4] of the second line is stored in an area of ​​the main memory 201 specified by the write address WADR=10000+1000*(1+3)+100*3=14300.

[0090] Thereafter, the line data from the third line onwards is similarly divided into four, and the four block data are stored in an area specified by the write address WADR of the main memory 201. Then, in ACT13, when it is confirmed that the write side line number counter WLCNT has reached the value (LINE-1), the memory control unit 211 ends the information processing of the procedure shown in the flowchart of FIG.

[0091] 6 is divided into four block data for each line as shown in Fig. 7, and each block data is shifted by one line across four lines and stored in the main memory 201. Therefore, one page of image data having "L" lines is converted into line data having "L+3" lines and stored in the main memory 201.

[0092] When one page of image data WDATA is written to the main memory 201 in this manner, the memory control unit 211 starts information processing according to the procedure shown in the flowchart of FIG. The memory control unit 211 waits for the line reference signal HSYNC to become valid as ACT21. When the line reference signal HSYNC becomes valid, the memory control unit 211 resets the read side line number counter RLCNT to "0" as ACT22. The memory control unit 211 resets the read time counter j to "0" as ACT23. The memory control unit 211 resets the read side pixel number counter RPCNT to "0" as ACT24.

[0093] The memory control unit 211 calculates the read address RADR as ACT 25. The read address RADR is calculated by the following arithmetic expression (2) using the start address STA, the line addition address LINEAD, the read side line number counter RLCNT, the read transfer unit, and the read time counter j. WADR=STA+LINEAD*RLCNT+RT*j …(2) The memory control unit 211 reads out image data of the number of pixels RT from the read address RADR of the main memory 201 as ACT 26 , and transfers it to the read buffer 204 .

[0094] The memory control unit 211 adds the number of pixels RT of the read transfer unit to the read side pixel counter RPCNT in ACT 27. Then, the memory control unit 211 checks whether the read side pixel counter RPCNT has reached the number of pixels PIX of one line in ACT 28.

[0095] If the read-side pixel counter RPCNT has not reached the number of pixels PIX in one line, the memory control unit 211 counts up the read-time counter j by "1" in ACT 29. Then, the memory control unit 211 returns to ACT 25 and executes the processes from ACT 25 onwards in the same manner as described above.

[0096] As a result, first, image data of pixel number RT, that is, block data [1-1], is read from an area specified by read address RADR=10000+1000*0+200*0=10000 in main memory 201, and transferred to read side buffer 204. Next, image data of pixel number RT is read from an area specified by read address RADR=10000+1000*0+200*1=10200 in main memory 201, and transferred to read side buffer 204. Note that since no image data is stored at read address RADR=10200, there is no image data to be transferred to read side buffer 204. Then, after this, read side pixel counter RPCNT reaches the number of pixels PIX for one line.

[0097] When the memory control unit 211 confirms in ACT28 that the read side pixel counter RPCNT has reached the number of pixels PIX in one line, it checks in ACT30 whether the read side line counter RLCNT is smaller than the number of lines LINE plus "3" (LINE+3).

[0098] As described above, one page of image data with a line count of "L" is converted into line data with a line count of "L+3" and stored in the main memory 201. Therefore, if the read side line number counter RLCNT is smaller than the value (LINE+3) obtained by adding "3" to the line count LINE, there remains line data that has not yet been transferred to the main memory 201. Therefore, in ACT30, it is confirmed whether the read side line number counter RLCNT is smaller than the value (LINE+3) obtained by adding "3" to the line count LINE.

[0099] If the read side line number counter RLCNT is smaller than the value (LINE+2), the memory control unit 211 counts up the read side line number counter RLCNT by "1" in ACT31. Then, the memory control unit 211 returns to ACT23 and executes the processes from ACT23 onwards in the same manner as described above.

[0100] As a result, image data with pixel count RT, that is, block data [2-1] and block data [1-2], are read from an area specified by read address RADR=10000+1000*1+200*0=11000 in main memory 201, and transferred to read side buffer 204. Next, image data with pixel count RT is read from an area specified by read address RADR=10000+1000*1+200*1=11200 in main memory 201, and transferred to read side buffer 204. Note that no image data is stored at read address RADR=11200, so no data is transferred to read side buffer 204.

[0101] Next, image data with pixel count RT, that is, block data [3-1] and block data [2-2], is read from an area specified by a read address RADR=10000+1000*2+200*0=12000 in the main memory 201, and transferred to the read side buffer 204. Next, image data with pixel count RT, that is, block data [1-3], is read from an area specified by a read address RADR=10000+1000*2+200*1=12200 in the main memory 201, and transferred to the read side buffer 204.

[0102] Next, image data with pixel count RT, that is, block data [4-1] and block data [3-2], is read from an area specified by a read address RADR=10000+1000*3+200*0=13000 in the main memory 201, and transferred to the read side buffer 204. Next, image data with pixel count RT, that is, block data [2-3] and block data [1-4], is read from an area specified by a read address RADR=10000+1000*3+200*1=13200 in the main memory 201, and transferred to the read side buffer 204.

[0103] Thereafter, in the same manner, image data of pixel count RT is sequentially transferred from the main memory 201 to the read side buffer 204. Then, when the memory control unit 211 confirms in ACT30 that the read side line number counter RLCNT has reached a value (LINE+3), it ends the information processing procedure shown in the flowchart of FIG.

[0104] On the other hand, the data conversion unit 214 executes information processing according to the procedure shown in the flow chart of Fig. 11. That is, the data conversion unit 214 waits for the read side line number counter RLCNT to count up as ACT41. When one line of block data is transferred to the read side buffer 204, the read side line number counter RLCNT counts up. When the read side line number counter RLCNT counts up, the data conversion unit 214 enables the read side sub-scanning signal RVDEN as ACT42. Also, the data conversion unit 214 resets the correction pixel number counter PPCNT to "0" as ACT43.

[0105] The data conversion unit 214 waits for the line reference signal HSYNC to become valid as ACT44. When the line reference signal HSYNC becomes valid, the data conversion unit 214 makes the read side main scanning signal RHDEN valid as ACT45.

[0106] The data conversion unit 214 reads one line of block data transferred to the read buffer 204 as ACT46. The data conversion unit 214 outputs one pixel data Px for that one line of block data, starting from the top pixel, to the selector 216 and the correction buffer 205 as ACT47. Then, every time one pixel data Px is output, the data conversion unit 214 counts up the correction pixel counter PPCNT by "1" as ACT48.

[0107] The data conversion unit 214 checks whether the correction pixel counter PPCNT has reached the number of pixels PIX in one line in ACT49. If the correction pixel counter PPCNT has not reached the number of pixels PIX in one line, the data conversion unit 214 returns to ACT47. That is, the data conversion unit 214 outputs the next pixel data Px to the selector 216 and the correction buffer 205. Then, the data conversion unit 214 counts up the correction pixel counter PPCNT by "1".

[0108] In ACT49, when the correction pixel number counter PPCNT reaches the number of pixels PIX of one line, the data conversion unit 214 disables the read side main scanning signal RHDEN in ACT50. Then, the data conversion unit 214 checks whether the read side line number counter RLCNT has counted up in ACT51. If the read side line number counter RLCNT has counted up, the data conversion unit 214 returns to ACT43. Then, the data conversion unit 214 executes the processes from ACT43 onwards in the same manner as described above.

[0109] When the reading and transfer of one page of image data WDATA is completed, the read side line number counter RLCNT is no longer counted up. If the read side line number counter RLCNT is not counted up in ACT51, the data conversion unit 214 disables the read side sub-scanning signal RVDEN in ACT52. With this, the data conversion unit 214 ends the information processing of the procedure shown in the flowchart of FIG.

[0110] The data conversion unit 214 has a function of converting the block data stored in the read buffer 204 into pixel-unit data and outputting it.

[0111] The correction control unit 215 executes information processing according to the procedure shown in the flowchart of Fig. 12. That is, the correction control unit 215 resets the correction time counter k to "0" in ACT61. Also, the correction control unit 215 initializes the address BADR of the correction buffer 205 to "0" in ACT62.

[0112] The correction control unit 215 waits for the correction pixel counter PPCNT to count up as ACT63. When one pixel data Px is output from the data conversion unit 214, the correction pixel counter PPCNT counts up. When the correction pixel counter PPCNT counts up, the correction control unit 215 checks whether the correction pixel counter PPCNT has exceeded the pixel number LINEP[k] of the line shift occurrence position corresponding to the correction time counter k as ACT64.

[0113] When the one pixel data Px is the pixel with pixel number LINEP[k] or an earlier pixel, the correction pixel counter PPCNT is equal to or smaller than the pixel number LINEP[k]. In this case, the correction control unit 215 selects the one pixel data Px output from the data conversion unit 214 as ACT65, and controls the selector 216 to output it as image data PDATA.

[0114] On the other hand, when the correction pixel number counter PPCNT exceeds the pixel number LINEP[k], the correction control unit 215 controls the selector 216 to select one pixel data Py stored in the address BADR of the correction buffer 205 as ACT66 and output it as image data PDATA. The correction control unit 215 also updates the address BADR of the correction buffer 205 by "1" as ACT67. Then, the correction control unit 215 stores one pixel data Px output from the data conversion unit 214 in the address BADR of the correction buffer 205 as ACT68.

[0115] After completing the process of ACT65 or ACT68, the correction control unit 215 checks whether the correction pixel counter PPCNT has reached the number of pixels PIX in one line in ACT69. If the correction pixel counter PPCNT has not reached the number of pixels PIX in one line, the correction control unit 215 checks whether the correction pixel counter PPCNT is equal to the pixel number LINEP[k] of the line deviation occurrence position corresponding to the correction time counter k in ACT70.

[0116] If the correction pixel counter PPCNT is not equal to the pixel number LINEP[k], the correction control unit 215 returns to ACT63. That is, the correction control unit 215 waits for the correction pixel counter PPCNT to count up. When the correction pixel counter PPCNT counts up, the correction control unit 215 executes the process from ACT64 onwards in the same manner as described above.

[0117] If the correction pixel counter PPCNT is equal to the pixel number LINEP[k], the correction control unit 215 counts up the correction time counter k by "1" in ACT71. Then, the correction control unit 215 returns to ACT63. That is, the correction control unit 215 waits for the correction pixel counter PPCNT to be counted up. When the correction pixel counter PPCNT is counted up, the correction control unit 215 executes the process from ACT64 onwards in the same manner as described above. At this time, since the correction time counter k is counted up, the value of the pixel number LINEP[k] at the line deviation occurrence position compared with the correction pixel counter PPCNT has changed from "a" of LINEP[0] to "b" of LINEP[1], or from "b" of LINEP[1] to "c" of LINEP[2], or from "c of LINEP[2]" to "d" of LINEP[3].

[0118] Then, in ACT69, when the correction pixel number counter PPCNT reaches the number of pixels PIX in one line, the correction control unit 215 ends the information processing of the procedure shown in the flowchart of FIG.

[0119] By the above process, the image data stored in the main memory 201 as shown in Fig. 7 is corrected as shown in Fig. 8 and output to the exposure head 74. That is, the first block data [1-1] of the first line is divided into first data [1-11] of a number of pixels a from the first pixel to pixel number LINEP[0] of the line shift occurrence position, and second data [1-12] of a number of pixels (T / 4-a) from the pixel after pixel number LINEP[0] of the line shift occurrence position to the final pixel of the block data [1-1]. The first data [1-11] is selected by the selector 216, and the second data [1-12] is stored in the correction buffer 205.

[0120] The second block data [1-2] of the first line is divided into first data [1-21], which is the number of pixels (bT / 4) from the first pixel to pixel number LINEP[1] of the line shift occurrence position, and second data [1-22], which is the number of pixels (2T / 4-b) from the pixel after pixel number LINEP[1] of the line shift occurrence position to the last pixel of the block data [1-2]. The first data [1-21] is selected by the selector 216, and the second data [1-22] is stored in the correction buffer 205.

[0121] The third block data [1-3] of the first line is divided into first data [1-31], which is the number of pixels (c-2T / 4) from the first pixel to pixel number LINEP[2] at the line shift occurrence position, and second data [1-32], which is the number of pixels (3T / 4-c) from the pixel after pixel number LINEP[2] at the line shift occurrence position to the last pixel of the block data [1-3]. The first data [1-31] ​​is selected by the selector 216, and the second data [1-32] is stored in the correction buffer 205.

[0122] The fourth block data [1-4] of the first line is divided into first data [1-41], which is the number of pixels (d-3T / 4) from the first pixel to pixel number LINEP[3] at the line shift occurrence position, and second data [1-42], which is the number of pixels (3T / 4-d) from the pixel after pixel number LINEP[3] at the line shift occurrence position to the last pixel of the block data [1-4]. The first data [1-41] is selected by the selector 216, and the second data [1-42] is stored in the correction buffer 205.

[0123] The second data stored in the correction buffer 205 is selected by the selector 216 when another second data is stored in the correction buffer 205 . Thereafter, the line data for the second and subsequent lines are processed in the same manner as for the first line. As a result, the selector 216 first outputs the first data [1-11] of the first block data [1-1] of the first line as the image data PDATA for the first line.

[0124] Next, as image data PDATA for the second line, the first data [2-11] of the first block data [2-1] of the second line, the second data [1-12] of the first block data [1-1] of the first line, and the first data [1-21] of the second block data [1-2] of the first line are output.

[0125] Next, as image data PDATA for the third line, the first data [3-11] of the first block data [3-1] of the third line, the second data [2-12] of the first block data [2-1] of the second line, the first data [2-21] of the second block data [2-2] of the second line, the second data [1-22] of the second block data [1-2] of the first line, and the first data [3-21] of the third block data of the first line are output.

[0126] Next, as image data PDATA for the fourth line, the first data [4-11] of the first block data on the fourth line, the second data [3-12] of the first block data on the third line, the first data [3-21] of the second block data on the third line, the second data [2-22] of the second block data on the second line, the first data [2-21] of the third block data on the second line, the second data [1-32] of the third block data [1-3] on the first line, and the first data [1-41] of the fourth block data [1-4] on the first line are output.

[0127] Next, as the image data PDATA for the fifth line, the first data [5-11] of the first block data [5-1] on the fifth line, the second data [4-12] of the first block data [4-1] on the fourth line, the first data [4-21] of the second block data [4-2] on the fourth line, the second data [3-22] of the second block data [3-2] on the third line, the first data [3-31] of the third block data [3-3] on the third line, the second data [2-32] of the third block data [2-3] on the second line, the first data [2-41] of the fourth block data [2-4] on the second line, and the second data [1-42] of the fourth block data [1-4] on the first line are output.

[0128] Thereafter, the sixth line and onwards are processed in the same manner. When the second data [4-42] of the fourth block data [L-4] of the Lth line is output as the image data PDATA of the L+4th line, the output of the image data WDATA for one page written in the main memory 201 to the exposure head 74 is completed. As a result, the light is irradiated from the light emitting element row of the exposure head 74 onto the surface of the photosensitive drum 71, and an electrostatic latent image for one page is formed on the photosensitive drum 71. Here, the light emitting element row is shifted by five lines in the sub-scanning direction V with respect to the main scanning direction H, but an electrostatic latent image parallel to the main scanning direction H is formed on the photosensitive drum 71 by the data correction function described above. Therefore, the inclination of the image caused by the inclination of the light emitting element row can be corrected.

[0129] In this embodiment, for example, assuming that the light emitting element row of the exposure head 74 is tilted by five lines in the sub-scanning direction V, one line of image data is divided into four and written to the main memory 201. Therefore, the storage capacity of the main memory 201 needs only to be a size obtained by adding three lines to the number of lines of image data for one page. Also, the write side buffer 203 and the read side buffer 204 only need to have an area capable of storing at least one line of image data. Also, the correction buffer 205 only needs to have an area capable of storing at least block data obtained by dividing one line. Therefore, the memory capacity required to correct the tilt of an image can be reduced. This allows the cost of the product to be reduced.

[0130] Moreover, access to the main memory 201 by the memory control unit 211 is limited to when writing block data obtained by dividing one line of image data into four, and when reading out the block data. In this way, by increasing the amount of data in one access and improving the data transfer efficiency, access to the main memory 201 does not occur frequently. As a result, the processing capacity of the processor 131 can be maintained high.

[0131] In this embodiment, the memory control unit 211 reads block data from the main memory 201 and transfers it to the read buffer 204. The data conversion unit 214 converts the block data stored in the read buffer 204 into pixel-unit data and outputs it. Therefore, the storage capacity of the read buffer 204 only needs to be the number of pixels of the block data. This makes it possible to further reduce memory capacity.

[0132] In this embodiment, the memory control unit 211 reads out two or more pieces of block data at a time and transfers them to the read-side buffer 204. Therefore, compared to reading out the block data one by one, the number of accesses to the main memory 201 is reduced, and the processing capacity of the processor 131 can be further improved.

[0133] In this embodiment, the write address generation unit 212 generates a write address WADR of the main memory 201 based on the start address STA of the main memory 201, the line addition address LINEAD of the main memory 201, the number of written block data [LINEAD*(WLCNT+LINEZ(i))], and the number of pixels of the block data [WT*i]. Then, the memory control unit 211 writes the block data to an area of ​​the main memory 201 specified by the write address WADR generated by the write address generation unit 212. Therefore, as long as an appropriate number of pixels WT is set according to the degree of inclination of the light-emitting element row of the exposure head 74, the write address WADR for the main memory 201 is automatically generated, making setting easy.

[0134] Similarly, in this embodiment, the read address generation unit 213 generates a read address RADR of the main memory 201 based on the start address ST of the main memory 201, the line addition address LINEAD of the main memory 201, the number of read line data RLCNT, and the number of pixels RT*j of image data read at one time. Then, the memory control unit 211 reads block data from an area of ​​the main memory 201 specified by the read address RADR generated by the read address generation unit 213. Therefore, as long as an appropriate number of pixels RT is set according to the degree of inclination of the light emitting element row of the exposure head 74, the read address RADR for the main memory 201 is also automatically generated, making setting easy.

[0135] Although one embodiment of the image forming apparatus has been described above, the embodiment is not limited to this.

[0136] In the above embodiment, a case where the light emitting element row of the exposure head 74 is tilted by five lines in the sub-scanning direction V has been exemplified. For example, even if the light emitting element row is tilted by six or more lines, the above embodiment can be applied as is by dividing one line of image data into block data whose number is one less than the number of lines, which is the amount of deviation, and setting the pixel numbers WT, RT, etc. accordingly. The same applies when the amount of deviation of the light emitting element row is four lines or less.

[0137] In the above embodiment, the memory control unit 211 divides one line of image data into two parts and reads it out. The number of divisions when reading out image data is not limited to two parts. However, a smaller number of divisions reduces the number of accesses to the main memory 201, thereby improving data transfer efficiency and enhancing processing capacity. Therefore, one line of image data may be read out in one division without dividing it.

[0138] Although several other embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope of the invention and the scope of the invention and its equivalents described in the claims. The following is an appended summary of the contents of the claims as originally filed. [1] An image carrier; an exposure head that irradiates light onto the image carrier from a plurality of light-emitting elements arranged in one direction to form a latent image on the image carrier based on image data; a developing device that develops the latent image on the image carrier by applying a developer thereto; a main memory for expanding and storing the image data as a plurality of line data in a main scanning direction; a memory control unit that divides the line data into a plurality of block data according to an inclination of an arrangement direction of the plurality of light-emitting elements in a sub-scanning direction with respect to the main scanning direction, and executes a write process of writing the plurality of block data into the main memory by shifting the plurality of block data by one line, and a read process of reading the block data from the main memory; a correction control unit that separates the block data read by the read process into first data consisting of a pixel where line deviation occurs due to the tilt and pixels preceding that pixel, and second data consisting of pixels following the pixel where line deviation occurs, stores the second data in a correction buffer, and outputs the first data to the exposure head together with the second data of the previous block stored in the correction buffer; An image forming apparatus comprising: [2] a read buffer for storing the block data read by the read process; and a data conversion unit for converting the block data stored in the read buffer into pixel-unit data and outputting the pixel-unit data. Further comprising: The image forming apparatus according to [1], wherein the correction control unit processes the first data and the second data based on the pixel-by-pixel data output from the data conversion unit. [3] The image forming apparatus according to [2], wherein the memory control unit reads out the block data in two or more batches and transfers them to the read-side buffer. [4] a write address generation unit that generates a write address of the main memory based on a start address of the main memory, a line addition address of the main memory, the number of the written block data, and the number of pixels of the block data; Further comprising: The image forming apparatus according to [1], wherein the memory control unit writes the block data to the main memory according to the write address generated by the write address generation unit. [5] a read address generation unit that generates a read address of the main memory based on a start address of the main memory, a line addition address of the main memory, the number of read line data, and the number of pixels of image data to be read at one time; Further comprising: The image forming apparatus according to [1], wherein the memory control unit reads block data from the main memory according to the read address generated by the read address generation unit. [Explanation of symbols]

[0139] 1...multifunction device, 2...toner cartridge, 11...casing, 12...communication interface, 13...system controller, 14...paper tray, 15...output tray, 16...conveyor, 17...image forming section, 18...fixing unit, 19...scanner section, 20...control panel, 21...automatic document feeder, 22...touch panel, 23...keyboard, 30...motor, 41...process unit, 42...transfer unit, 71...photosensitive drum, 72...cleaner, 73...charging unit, 74...exposure head, 75...developer, 76...image forming forming unit, 91...transfer belt, 92...secondary transfer opposing roller, 93...primary transfer roller, 94...secondary transfer roller, 131...processor, 132...ROM, 133...RAM, 134...auxiliary storage device, 201...main memory, 202...work memory, 203...write side buffer, 204...read side buffer, 205...correction buffer, 211...memory control unit, 212...write address generation unit, 213...read address generation unit, 214...data conversion unit, 215...correction control unit, 216...selector, P...printing medium.

Claims

1. An image carrier; an exposure head that irradiates light onto the image carrier from a plurality of light-emitting elements arranged in one direction to form a latent image on the image carrier based on image data; a developing device that develops the latent image on the image carrier by applying a developer thereto; a main memory for expanding and storing the image data as a plurality of line data in a main scanning direction; a memory control unit that divides the line data into block data whose number is one less than the number of lines that is a shift amount in the sub-scanning direction corresponding to an inclination of an arrangement direction of the plurality of light-emitting elements in the sub-scanning direction with respect to the main scanning direction, and executes a write process of writing the plurality of block data into the main memory by shifting the plurality of block data by one line, and a read process of reading the block data from the main memory; a read-side buffer for storing the block data read by the read process; a correction control unit that divides each block of data stored in the read-side buffer into first data consisting of a pixel where line deviation occurs due to the inclination and pixels preceding that pixel, and second data consisting of pixels following the pixel where line deviation occurs, stores the second data in a correction buffer, and outputs the first data to the exposure head together with the second data of the previous block stored in the correction buffer; An image forming apparatus comprising:

2. A data conversion unit that converts the block data stored in the read-side buffer into pixel-unit data and outputs the pixel-unit data; Further comprising: The correction control unit processes the first data and the second data based on the pixel-by-pixel data output from the data conversion unit.

2. The image forming apparatus according to claim 1.

3. the memory control unit reads out the block data in two or more chunks and transfers them to the read-side buffer; 3. The image forming apparatus according to claim 2.

4. a write address generation unit that generates a write address of the main memory based on a start address of the main memory, a line addition address of the main memory, the number of the written block data, and the number of pixels of the block data; Further comprising: the memory control unit writes the block data into the main memory in accordance with the write address generated by the write address generation unit; 2. The image forming apparatus according to claim 1.

5. a read address generation unit that generates a read address of the main memory based on a start address of the main memory, a line addition address of the main memory, the number of read line data, and the number of pixels of image data to be read at one time; Further comprising: the memory control unit reads the block data from the main memory in accordance with the read address generated by the read address generation unit; 2. The image forming apparatus according to claim 1.

Images