JP7630963B2 - Image forming device - Google Patents

Description

An embodiment of the present invention relates to an image forming device.

The exposure head is an image forming member that selectively exposes the outer peripheral surface of a uniformly charged photosensitive drum to form an image. The exposure head is used in an image forming device that uses an electrophotographic process. Examples of image forming devices include printers, copiers, and multifunction peripherals (MFPs).

The exposure head has a row of light-emitting elements in which multiple light-emitting elements are arranged in one direction. The light-emitting elements are, for example, LEDs (Light Emitting Diodes). The light-emitting elements may also be, for example, OLEDs (Organic Light Emitting Diodes), that is, organic EL.

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. Depending on the accuracy of the head attachment part, the exposure head may be attached at an angle tilted in the sub-scanning direction with respect to the main scanning direction. In that case, an image is formed on the photosensitive drum that is tilted in the sub-scanning direction with respect to the main scanning direction. For this reason, it is necessary to correct the tilt of the image.

Conventionally, there is a method for correcting the tilt of an image by shifting the read address when reading image data expanded in main memory to match the tilt of the exposure head. However, this method requires frequent access to the main memory. This results in problems such as reduced data transfer efficiency and reduced processing power.

Another method involves first loading multiple lines of image data equivalent to the tilt from the main memory into high-speed memory, then delaying the output of the corresponding pixel data in accordance with the tilt of the exposure head. However, this method requires large memory resources, which results in increased costs.

JP 2009-223141 A JP 2001-352445 A

The problem that the embodiment of the present invention aims to solve is to provide an image forming device that can reduce the memory capacity required to correct the tilt of an image and suppress a decrease in processing power.

In one embodiment, the image forming apparatus includes an image carrier, an exposure head, a developer, a main memory, a memory control unit, a read-side buffer, and a correction control unit. The exposure head irradiates light from a plurality of light-emitting elements arranged in one direction onto the image carrier to form a latent image based on image data on the image carrier. The developer applies developer to the latent image on the image carrier to develop it. The main memory expands and stores the image data as a plurality of line data in a main scanning direction. The memory control unit divides the line data into block data whose number is one less than the number of lines, which is a shift amount in the sub-scanning direction according to an inclination of the 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. The read-side buffer stores the block data read by the read process. The correction control unit divides each block of data stored in the read-side buffer into first data consisting of pixels where line shift occurs due to tilt and the pixels before that, and second data consisting of pixels after the pixel where line shift occurs, stores the second data in the 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.

FIG. 1 is a schematic diagram showing a schematic configuration of a multifunction peripheral according to an embodiment. FIG. 2 is a schematic diagram showing a configuration of a main part of an image forming unit in the multifunction peripheral; FIG. 2 is a block diagram showing a main part of a circuit configuration in the multifunction peripheral. FIG. 4 is a circuit diagram for explaining a tilt correction function of image data provided in the multifunction peripheral. FIG. 4 is a schematic diagram for explaining the arrangement direction of light-emitting elements in the exposure head. FIG. 4 is a schematic diagram showing an example of image data before being written to a main memory. FIG. 4 is a schematic diagram showing an example of image data written to a main memory. FIG. 11 is a schematic diagram showing an example of image data corrected by a tilt correction function. 4 is a flowchart showing the main steps of a data write process related to a memory control unit. 4 is a flowchart showing the main steps of a data read process performed by a memory control unit. 11 is a flowchart showing the main steps of a data gradient adjustment process performed by a data conversion unit. 11 is a flowchart showing the main steps of a data inclination adjustment process related to a correction control unit.

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

FIG. 1 is a schematic diagram showing the general configuration of a multifunction device 1 according to this embodiment. The multifunction device 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 device 1 receives toner from a toner cartridge 2 and forms an image on the print medium P using the received toner. The toner is, for example, four color toners: 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.

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 unit 16, an image forming unit 17, a fixing unit 18, a scanner unit 19, and a control panel 20.

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, multiple paper trays 14, a transport unit 16, an image forming unit 17, and a fixing unit 18. Part of the top surface of the housing 11 serves as a paper output tray 15.

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 external devices. The external device is, for example, a higher-level device that has the 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, composed of a LAN connector. 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).

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 medium P. The print job may include information indicating whether color printing or monochrome printing is to be performed.

The system controller 13, which generates the print job, controls the operation of the transport unit 16, image forming unit 17, and 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.

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.

Each of the multiple paper trays 14 is a cassette that stores print media P. The paper trays 14 are configured so that print media P can be supplied from outside the housing 11. For example, the paper trays 14 are configured so that they can be pulled out from the housing 11.

The 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.

The paper feed transport 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 transport path 31 has multiple pickup rollers 33 corresponding to each paper tray 14. Each pickup roller 33 takes in the print medium P from the paper tray 14 into the paper feed transport path 31.

The paper discharge transport path 32 is a transport 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 paper discharge transport path 32 is supported by the paper discharge tray 15.

The image forming unit 17 is configured to form an image on the print medium P. Details of the image forming unit 17 will be described later.

The fixing unit 18 has a heat roller 34 and a pressure roller 35. The fixing unit 18 heats the print medium P being transported along the paper discharge transport path 32 to a predetermined temperature with the heat roller 34, and then presses the print medium P with the pressure roller 35, thereby fixing the image transferred to the print medium P to the print medium P.

The scanner unit 19 is a device that reads documents and converts them into image data, and is installed at the top of the housing 11. The 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.

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

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 way, 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.

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 each of the color toners, yellow, magenta, cyan, and black. Each process unit 41 includes a toner cartridge 2 having a color toner of the corresponding color.

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

First, the toner cartridge 2 will be described. As shown in FIG. 2, the toner cartridge 2 includes a toner storage container 51, a toner delivery mechanism 52, and a memory 53.

The toner storage container 51 is a container that stores toner. The toner delivery mechanism 52 is a mechanism that delivers the toner in the toner storage container 51. The toner delivery mechanism 52 is, for example, a screw provided in the toner storage container 51. The toner in the toner storage container 51 is delivered by the rotation of the screw.

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

When the toner cartridge 2 is loaded into the loading section 60, the toner supply motor 61 is connected to the toner delivery mechanism 52 of the toner cartridge 2. The toner supply motor 61 drives the toner delivery mechanism 52 under the control of the system controller 13. When the toner supply motor 61 drives the toner delivery 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 toner has been supplied to the developing device 75 by driving the toner delivery mechanism 52, and the date and time of supply.

Next, the process unit 41 will be described. As shown in FIG. 2, the process unit 41 includes a photosensitive drum 71, a cleaner 72, a charging unit 73, an exposure head 74, and a developing device 75.

The photosensitive drum 71 is a photosensitive member that includes 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.

The cleaner 72 has a blade 721 that contacts 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.

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

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), or organic electroluminescence (OLED). 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.

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

The developing device 75 is a device that deposits toner onto the photosensitive drum 71 to form a toner image on the photosensitive drum. The developing device 75 includes a developer container 81, a stirring mechanism 82, a developing roller 83, a doctor blade 84, and an auto toner control (ATC) sensor 85.

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 stored in the developer container 81 when the developing unit 75 is manufactured.

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.

The ATC sensor 85 is, for example, a magnetic flux sensor that has a coil and detects the 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. In other words, 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 the 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.

As described above, when light is irradiated from the exposure head 74 onto the surface of the photosensitive drum 71, which has been 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. In other words, the exposure head 74 and the developing device 75 constitute the image forming unit 76.

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.

The transfer belt 91 is an endless belt wound around the secondary transfer opposing roller 92 and multiple winding rollers. The inner surface (back surface) of the transfer belt 91 contacts the secondary transfer opposing roller 92 and multiple winding rollers, and the outer surface (front surface) faces the photosensitive drum 71 of the process unit 41.

The secondary transfer opposing roller 92 rotates by the power transmitted from the drive mechanism, thereby transporting 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.

A plurality of primary transfer rollers 93 are provided for each process unit 41. The plurality of primary transfer rollers 93 are arranged to face the photosensitive drums 71 of the corresponding process units 41. Specifically, the plurality of primary transfer rollers 93 are arranged in 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 peripheral surface of the transfer belt 91, displacing the transfer belt 91 toward the photosensitive drum 71. This displacement causes the surface of the transfer belt 91 to come into contact with the photosensitive drum 71.

The secondary transfer roller 94 is disposed in a position opposite 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 around the circumferential surface of the secondary transfer opposing roller 92. This contact and pressure forms a transfer nip in which the secondary transfer roller 94 and the surface of the transfer belt 91 are in close contact with each other.

The secondary transfer roller 94 and the secondary transfer counter roller 92 rotate to transport the print medium P supplied from the paper feed path 31 while sandwiching it between them. 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.

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 multiple process units 41, the toner images are transferred to the transfer belt 91 from the photosensitive drums 71 of the multiple 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.

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 communication interface 12, an image forming unit 17, a fixing unit 18, a scanner unit 19, a control panel 20, a motor 30, etc. to a system controller 13 via signal lines.

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.

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).

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

The auxiliary storage device 134 corresponds to the auxiliary memory portion of the computer. As the auxiliary storage device 134, for example, well-known storage devices such as an EEPROM (Electric Erasable Programmable Read-Only Memory), a HDD (Hard Disc Drive), or an SSD (Solid State Drive) are 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.

The system controller 13 connects the toner cartridge 2, photosensitive drum 71, cleaner 72, charging unit 73, image forming unit (exposure head 74, developer 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.

The motor 30 includes a first motor used in the drive mechanism that drives the conveying unit 16, a second motor used in the drive mechanism that rotates the photosensitive drum 71, and a third motor used in the 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 each of the plurality of process units 41. The motor 30 may include a motor used in a drive mechanism other than the drive mechanisms described above. The motor 30 is, for example, a brushless motor. The motor 30 may also be a brush motor.

Now, in each process unit 41, the exposure head 74 is attached by the head attachment part so that its light-emitting element row faces the photosensitive drum 71. In principle, the light-emitting element row is attached so that it is 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 that it is 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.

This embodiment provides a multifunction printer 1 that can form an image on a print medium P that is parallel to the main scanning direction H by using an image data tilt correction function, even if the light-emitting element row of the exposure head 74 is installed tilted in the secondary scanning direction with respect to the main scanning direction H of the photosensitive drum 71.

Next, the image data tilt correction function will be described. Note that the following will be an example of a case where the light-emitting element row of the exposure head 74 in one process unit 41 is installed tilted in the sub-scanning direction with respect to the main scanning direction H of the photosensitive drum 71. A similar approach can be taken when the light-emitting element row of the exposure head 74 in another process unit 41 is installed tilted.

Figure 4 is a circuit diagram for explaining the image data tilt correction function. This circuit is configured in the system controller 13. That is, the system controller 13 configures the main memory 201, work memory 202, write side buffer 203, read side buffer 204, and correction buffer 205 using the RAM 133. The system controller 13 also stores a control program in the ROM 132 or auxiliary storage device 134 so that the processor 131 has a configuration of 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.

The main memory 201 is an area for expanding and storing image data as multiple line data in the main scanning direction.

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.

The first setting area 221 is set to the number of lines LINE of one page of image data. The second setting area 222 is set to the number of pixels PIX of one line. Note that one pixel is 1 byte (8 bits). The third setting area 223 is set to the number of pixels WT of the write transfer unit. The fourth setting area 224 is set to the number of pixels RT of the read transfer unit. The fifth setting area 225 is set to the line shift amount LINEZ[i]. The sixth setting area 226 is set to the pixel number LINEP[k] of the line shift occurrence position. 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". The seventh setting area 227 is set to the start address STA. The eighth setting area 228 is set to the line addition address LINEAD. The items of each setting area 221 to 228 will be made clear in the operation explanation below.

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

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 multiple lines of data for each line of data.

The read buffer 204 is an area for storing image data read from the main memory 201. The read buffer 204 stores image data consisting of multiple lines of data for each line of data.

The correction buffer 205 is an area for temporarily storing data that is delayed by the tilt correction function. The delayed data will be described later.

In this configuration, the work memory 202, the light side buffer 203, and the memory control unit 211 are input with a light side main scanning signal WHDEN and a light side sub-scanning signal WVDEN. The light side buffer 203 is also input with image data WDATA. The memory control unit 211 and the data conversion unit 214 are input with a line reference signal HSYNC. The data conversion unit 214 also receives image data RDATA. The data conversion unit 214 outputs a read side main scanning signal RHDEN and a read side sub-scanning signal RVDEN to the exposure head 74. The selector 216 outputs image data PDATA to the exposure head 74.

Image data WDATA is image data before it is written to main memory 201. Image data RDATA is image data read from main memory 201. Image data PDATA is image data that has been corrected by the tilt correction function.

The image data WDATA is included in the print job. The light side main scanning signal WHDEN, the light 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.

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 data writing process to the main memory 201. Fig. 10 is a flow chart showing the main steps of a data reading process from the main memory 201. Figs. 11 and 12 are flow charts showing the main steps of a tilt adjustment process for data read from the main memory 201.

As shown in FIG. 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.

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 Figure 6. In this case, the memory control unit 211 limits the misalignment to four lines, one less than the other, and writes one line of data to the main memory 201. To do this, one line of image data is divided into four image data pieces with at least "T/4" pixels and written to the main memory 201. Therefore, "T/4" is set in the third setting area 223 as the number of pixels WT per write transfer unit.

In addition, the shift amount LINEZ[0], shift amount LINEZ[1], shift amount LINEZ[2], and shift 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 shift amount is based on the image data including the first pixel. That is, in the fifth setting area 225, "0" is set as the shift amount LINEZ[0], "1" is set as the shift amount LINEZ[1], "2" is set as the shift amount LINEZ[2], and "3" is set as the shift amount LINEZ[3].

Furthermore, for each of the image data divided into four by the number of pixels "T/4", pixel number LINEP[0], pixel number LINEP[1], pixel number LINEP[2], and pixel number LINEP[3] at the positions where line shift occurs are calculated 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].

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 it is divided into two parts and read out, one line of image data can be read out from the main memory 201 as image data of at least "T/2" pixels. Therefore, "T/2" is set in the fourth setting area 224 as the number of pixels RT of the read transfer unit. In other words, the number of pixels RT is the number of pixels of the image data read out in one time.

In addition, the start address STA of the main memory 201 is set in the seventh setting area 227, and the line addition address LINEAD of the main memory 201 is set in the 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". In addition, the number of pixels WT in the write transfer unit is set to "100", and the number of pixels RT in the read transfer unit is set to "200".

In this way, when the data required for correction is set in the first to eighth setting areas 221 to 228 and the image data WDATA included 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 in Figure 9.

In the following, image data obtained by dividing one line of image data by the number of pixels "T/4" will be referred to as block data. Therefore, the number of pixels WT in a write transfer unit can also be referred to as the number of pixels in block data.

The memory control unit 211 waits for the right-side sub-scanning signal WVDEN to become valid in ACT 1. 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" in ACT 2. The memory control unit 211 resets the write-time counter i to "0" in ACT 3. The memory control unit 211 resets the right-side pixel number counter WPCNT to "0" in ACT 4.

The memory control unit 211 waits for the right-side main scanning signal WHDEN to become valid in ACT 5. When the right-side main scanning signal WHDEN becomes valid, the memory control unit 211 calculates the write address WADR in ACT 6. The write address WADR is calculated by the following equation (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 in the write transfer unit WT, and the write-time counter i.

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 ACT 7. The memory control unit 211 checks whether the write-side pixel counter WPCNT has reached the number of pixels PIX of one line in ACT 8. 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 has matched the multiple [(i+1)*WT] of the number of pixels WT of the write transfer unit in ACT 9. 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 ACT 7. 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.

In ACT 9, when the write-side pixel counter WPCNT matches the multiple [(i+1)*WT] of the pixel count WT of the write transfer unit, the memory control unit 211 writes the image data of the pixel count [(i+1)*WT] input to the write-side buffer 203, that is, the block data, to the area specified by the write address WADR of the main memory 201 in ACT 10. The memory control unit 211 counts up the write time counter i by "1" in ACT 11. Then, the memory control unit 211 returns to ACT 6 and executes the processes from ACT 6 onwards in the same manner as described above.

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 the 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 the 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 the 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 counter WPCNT reaches the number of pixels PIX in one line.

When the memory control unit 211 confirms in ACT 8 that the right-side pixel counter WPCNT has reached the number of pixels PIX for one line, it writes the remaining data of one line of data input to the right-side buffer 203 to the write address WADR area of the main memory 201 in ACT 12. 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.

In ACT 13, 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. 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 ACT 14. Then, the memory control unit 211 returns to ACT 3 and executes the processes from ACT 3 onwards in the same manner as described above.

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

Then, 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 ACT 13, 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 procedure shown in the flowchart of FIG. 9.

By the above processing, the image data shown in FIG. 6 is divided into four block data for each line as shown in FIG. 7, and each block data is stored in the main memory 201 shifted by one line across four lines. Therefore, one page of image data with "L" lines is converted into line data with "L+3" lines and stored in the main memory 201.

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 in ACT 21. When the line reference signal HSYNC becomes valid, the memory control unit 211 resets the read side line number counter RLCNT to "0" in ACT 22. The memory control unit 211 resets the read time counter j to "0" in ACT 23. The memory control unit 211 resets the read side pixel number counter RPCNT to "0" in ACT 24.

The memory control unit 211 calculates the read address RADR in 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 the image data of the pixel count RT from the read address RADR of the main memory 201 in ACT 26 , and transfers it to the read buffer 204 .

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.

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. The memory control unit 211 then returns to ACT 25 and executes the processes from ACT 25 onwards in the same manner as described above.

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

When the memory control unit 211 confirms in ACT 28 that the read side pixel counter RPCNT has reached the number of pixels PIX in one line, it checks in ACT 30 whether the read side line counter RLCNT is smaller than the number of lines LINE plus "3" (LINE+3).

As mentioned 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 count counter RLCNT is smaller than the line count LINE plus "3" (LINE+3), there is line data remaining that has not yet been transferred to the main memory 201. Therefore, in ACT 30, it is checked whether the read side line count counter RLCNT is smaller than the line count LINE plus "3" (LINE+3).

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 ACT 31. Then, the memory control unit 211 returns to ACT 23 and executes the processes from ACT 23 onwards in the same manner as described above.

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

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

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

After that, in the same manner, image data with pixel count RT is sequentially transferred from the main memory 201 to the read side buffer 204. Then, in ACT 30, when the memory control unit 211 confirms that the read side line count counter RLCNT has reached a value (LINE+3), it ends the information processing procedure shown in the flowchart of FIG. 10.

Meanwhile, 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 in ACT 41. 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 in ACT 42. In addition, the data conversion unit 214 resets the correction pixel number counter PPCNT to "0" in ACT 43.

The data conversion unit 214 waits for the line reference signal HSYNC to become valid (ACT 44). When the line reference signal HSYNC becomes valid, the data conversion unit 214 enables the read side main scanning signal RHDEN (ACT 45).

The data conversion unit 214 reads one line of block data transferred to the read side buffer 204 in ACT 46. The data conversion unit 214 outputs one pixel data Px from the first pixel of the one line of block data to the selector 216 and the correction buffer 205 in ACT 47. Then, each time one pixel data Px is output, the data conversion unit 214 counts up the correction pixel counter PPCNT by "1" in ACT 48.

In ACT 49, the data conversion unit 214 checks whether the correction pixel number counter PPCNT has reached the number of pixels PIX in one line. If the correction pixel number counter PPCNT has not reached the number of pixels PIX in one line, the data conversion unit 214 returns to ACT 47. 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 number counter PPCNT by "1".

In ACT 49, when the correction pixel number counter PPCNT reaches the number of pixels PIX in one line, the data conversion unit 214 disables the read side main scanning signal RHDEN in ACT 50. Then, in ACT 51, the data conversion unit 214 checks whether the read side line number counter RLCNT has counted up. If the read side line number counter RLCNT has counted up, the data conversion unit 214 returns to ACT 43. Then, the data conversion unit 214 executes the processes from ACT 43 onwards in the same manner as described above.

When the reading and transfer of one page of image data WDATA is completed, the read side line number counter RLCNT stops counting up. If the read side line number counter RLCNT has not been counted up in ACT 51, the data conversion unit 214 disables the read side sub-scan signal RVDEN in ACT 52. With this, the data conversion unit 214 ends the information processing of the procedure shown in the flowchart of FIG. 11.

Here, the data conversion unit 214 has the function of converting the block data stored in the read-side buffer 204 into pixel-unit data and outputting it.

The correction control unit 215 executes information processing according to the procedure shown in the flow chart of FIG. 12. That is, the correction control unit 215 resets the correction time counter k to "0" in ACT 61. In addition, the correction control unit 215 initializes the address BADR of the correction buffer 205 to "0" in ACT 62.

The correction control unit 215 waits for the correction pixel number counter PPCNT to count up in ACT 63. When one pixel data Px is output from the data conversion unit 214, the correction pixel number counter PPCNT counts up. When the correction pixel number counter PPCNT counts up, the correction control unit 215 checks whether the correction pixel number counter PPCNT has exceeded the pixel number LINEP[k] of the position where the line shift occurred corresponding to the correction time counter k in ACT 64.

When the one pixel data Px is the pixel with pixel number LINEP[k] or an earlier pixel, the correction pixel number counter PPCNT is equal to or less than 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 ACT 65, and controls the selector 216 to output it as image data PDATA.

In contrast, when the correction pixel number counter PPCNT exceeds the pixel number LINEP[k], the correction control unit 215 selects one pixel data Py stored in the address BADR of the correction buffer 205 in ACT 66, and controls the selector 216 to output it as image data PDATA. The correction control unit 215 also updates the address BADR of the correction buffer 205 by "1" in ACT 67. 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 in ACT 68.

After completing the processing in ACT 65 or ACT 68, the correction control unit 215 checks whether the correction pixel counter PPCNT has reached the number of pixels PIX in one line in ACT 69. 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 position where the line shift occurred corresponding to the correction time counter k in ACT 70.

If the correction pixel number counter PPCNT is not equal to the pixel number LINEP[k], the correction control unit 215 returns to ACT 63. That is, the correction control unit 215 waits for the correction pixel number counter PPCNT to count up. When the correction pixel number counter PPCNT counts up, the correction control unit 215 executes the processing from ACT 64 onwards in the same manner as described above.

When 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 ACT 71. Then, the correction control unit 215 returns to ACT 63. 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 ACT 64 onwards in the same manner as described above. At this time, since the correction time counter k has been counted up, the value of the pixel number LINEP[k] at the position where the line shift occurs, which is 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].

Then, in ACT 69, 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 procedure shown in the flowchart of Figure 12.

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], which is a number of pixels from the first pixel to pixel number LINEP[0] where the line shift occurs, and second data [1-12], which is (T/4-a) number of pixels from the pixel after pixel number LINEP[0] where the line shift occurs 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.

The second block data [1-2] of the first line is divided into first data [1-21], which is the number of pixels (b-T/4) from the first pixel to pixel number LINEP[1] at the position where the line shift occurred, and second data [1-22], which is the number of pixels (2T/4-b) from the pixel after pixel number LINEP[1] at the position where the line shift occurred to the final 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.

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] where the line shift occurred, and second data [1-32], which is the number of pixels (3T/4-c) from the pixel after pixel number LINEP[2] where the line shift occurred to the final 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.

The fourth block data [1-4] on 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] where the line shift occurred, and second data [1-42], which is the number of pixels (3T/4-d) from the pixel after pixel number LINEP[3] where the line shift occurred to the final 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.

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.

Next, as the 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.

Next, as the 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.

Next, as the 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.

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

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 one page of image data WDATA written in the main memory 201 to the exposure head 74 is completed. As a result, 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 from 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.

In this embodiment, for example, if it is assumed that the row of light emitting elements 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 equal to the number of lines of image data for one page plus three lines. Furthermore, 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. Furthermore, the correction buffer 205 only needs to have an area capable of storing block data obtained by dividing at least 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.

In addition, 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 that 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 power of the processor 131 can be maintained high.

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.

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

In this embodiment, the write address generation unit 212 generates a write address WADR for 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 block data written [LINEAD*(WLCNT+LINEZ(i))], and the number of pixels of the block data [WT*i]. The memory control unit 211 then 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.

Similarly, in this embodiment, the read address generation unit 213 generates a read address RADR for 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 line data read out RLCNT, and the number of pixels RT*j of the image data read out at one time. The memory control unit 211 then reads block data from the 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 it easy to set.

The above describes one embodiment of an image forming device, but the embodiment is not limited to this.

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 is 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.

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

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 any one of claims 1 to 5, 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 claim 2, wherein the memory control unit reads out the block data in two or more chunks 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 any one of claims 1 to 5, wherein the memory control unit writes the block data to the main memory in accordance with 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 any one of claims 1 to 5, wherein the memory control unit reads block data from the main memory in accordance with the read address generated by the read address generation unit.

1...Multifunction device, 2...Toner cartridge, 11...Housing, 12...Communication interface, 13...System controller, 14...Paper tray, 15...Paper output tray, 16...Transport unit, 17...Image forming unit, 18...Fuser unit, 19...Scanner unit, 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...Developing unit, 76...Image forming unit 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 (5)

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: 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. 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. 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. a read address generating 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.