JP2009180920A - Image forming apparatus and data transfer method thereof - Google Patents

Abstract

An image forming apparatus that corrects a positional deviation of an image with respect to a recording material without increasing a line buffer.
The image forming apparatus performs image formation by reading out image data stored in a memory in the apparatus based on the deviation of the scanning line by the deflection scanning apparatus and transferring the read image data to the deflection scanning apparatus. . Specifically, when the image data of one scanning line is read, the image forming apparatus also reads the image data of other lines with respect to the image data at the position where the scanning line shift occurs. The read image data of the other lines are combined with the corresponding image data of the current line.
[Selection] Figure 3

Description

  The present invention uses an exposure unit that scans and exposes an image carrier, and a developing unit that visualizes an electrostatic latent image generated on the image carrier by exposure scanning from the exposure unit on a recording material. The present invention relates to an image forming apparatus that performs image formation based on the above and a data transfer method thereof.

  In recent years, in order to increase the image forming speed, an electrophotographic image forming apparatus includes the same number of developing devices and photosensitive drums as the number of color materials, and sequentially images of different colors on an image conveying belt or a recording material. The tandem method is used to transfer the image. In this tandem-type image forming apparatus, a plurality of factors that cause image misregistration with respect to a recording material are known, and various countermeasures have been proposed for each factor.

  For example, these factors include non-uniformity and attachment position deviation of the deflection scanning device lens, and assembly position displacement of the deflection scanning device to the image forming apparatus main body. Due to this factor, the scanning line is inclined or bent, and the degree of the change differs for each color, thereby causing a positional deviation of the image with respect to the recording material.

  As a method for coping with such a positional deviation of an image with respect to a recording material, Japanese Patent Laid-Open No. 2004-133830 discloses that a lens is mechanically measured by measuring the amount of bending of a scanning line using an optical sensor in an assembly process of a deflection scanning device. There has been proposed a method in which the rotation of the scanning line is adjusted by rotating and then fixing with an adhesive. Further, in Patent Document 2, in the process of assembling the deflection scanning device into the image forming apparatus main body, the magnitude of the inclination of the scanning line is measured using an optical sensor, and the deflection scanning device is mechanically tilted to adjust the scanning line. A method of assembling the image forming apparatus main body after adjusting the inclination has been proposed.

Furthermore, Patent Document 3 proposes a method of measuring the inclination of a scanning line and the amount of bending using an optical sensor, correcting bitmap image data so as to cancel them, and forming the corrected image. Has been. This method electrically corrects the positional deviation of the image with respect to the recording material by processing the image data.
JP 2002-116394 A JP 2003-241131 A JP 2004-170755 A

  However, the prior art has the following problems. In the methods described in Patent Document 1 and Patent Document 2, a mechanical adjustment member and an adjustment process at the time of assembly are necessary, which involves complicated operations and increases costs. On the other hand, the method described in Patent Document 3 eliminates the need for a mechanical adjustment member or an adjustment process during assembly, and thus is less expensive for recording materials than the methods described in Patent Document 1 and Patent Document 2. Image displacement can be eliminated.

  However, in the method of correcting bitmap image data described in Patent Document 3, it is necessary to provide a line buffer in order to perform the blending process of the upper and lower lines at the bent portion of the scanning line. The required capacity of the line buffer depends on the bending width of the scanning line. For example, if the scan line bend width is N lines of bitmap image data, a line buffer capable of storing N lines is required. Here, the value of N varies among image forming apparatuses. Therefore, the capacity of the line buffer actually mounted must correspond to the number of lines exceeding the maximum value of this variation. For this reason, the capacity of the line buffer is increased, the circuit scale for correcting the bitmap image data is increased, and the cost is increased.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that corrects a positional deviation of an image with respect to a recording material without increasing a line buffer.

  The present invention can be realized, for example, as an image forming apparatus including an exposure unit that exposes an image carrier and a shift amount detection unit that detects a shift amount of a scanning line by the exposure unit. The present image forming apparatus eliminates the deviation of the scanning line in the image data used for one scanning line from the image data stored in the image forming apparatus based on the amount of deviation of the scanning line. Designating means for designating a switching position for switching to image data of another line, reading means for reading out the image data corresponding to the designated image data and the switching position, and the vicinity of the switching position among the read image data A combination means for combining the image data of the other line with the image data of the other line and transferring it to the exposure means.

  In addition, the present invention can be realized as a data transfer method of an image forming apparatus including, for example, an exposure unit that exposes an image carrier and a shift amount detection unit that detects a shift amount of a scanning line by the exposure unit. The data transfer method is based on the amount of deviation of the scanning line, in order to eliminate the deviation of the scanning line in one scanning line from the image data used for one scanning line among the image data stored in the image forming apparatus. A switching position for switching to the image data of the line, a step for reading the image data corresponding to the specified image data and the switching position, and image data in the vicinity of the switching position among the read image data And a step of combining the image data of other lines and transferring the image data to the exposure means.

  The present invention can provide, for example, an image forming apparatus that corrects a positional deviation of an image with respect to a recording material without increasing a line buffer.

  An embodiment of the present invention is shown below. The individual embodiments described below will help to understand various concepts, such as superordinate concepts, intermediate concepts and subordinate concepts of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, with reference to FIG. 1A thru | or FIG. 5, the apparatus structure which implement | achieves each embodiment of this invention is demonstrated.

[Image forming apparatus]
FIG. 1A is a cross-sectional view illustrating an example of an image forming apparatus 100 according to the present embodiment. Here, only the main elements related to the present invention will be described. Hereinafter, an electrophotographic printer will be described as an application example of the image forming apparatus 100.

  The image forming apparatus 100 is a tandem color printer having a photosensitive drum 105 for each color of yellow (Y), magenta (M), cyan (Cy), and black (Bk) along the transfer belt 109. Here, an example using four color toners will be described, but of course, the present embodiment can also be described using a color printer of six colors or the like as an example. The image forming apparatus 100 includes a recording material cassette 101, a manual feed tray 102, a deflection scanning device 103, image forming units 104 a, b, c and d, a transfer belt 109, a fixing unit 110, and a registration detection sensor 111.

  The recording material cassette 101 and the manual feed tray 102 are loaded with a recording material and feed the recording material placed in the image forming apparatus 100. The deflection scanning device 103 includes a plurality of laser light sources, and forms an electrostatic latent image by exposing the photosensitive drum 105 included in each of the image forming units 104 (104a to 104d). In the following, since each image forming unit 104 has the same configuration, the image forming unit 104a will be described as an example. The image forming unit 104 includes a photosensitive drum 105, a primary charger 106, a developing unit 107, and a cleaning unit 108. The image forming unit 104 may be configured as an exchange unit that can be attached to and detached from the image forming apparatus 100. The photosensitive drum 105 functions as an image carrier, is uniformly charged by the primary charger 106, and an electrostatic latent image is formed by the laser output of the deflection scanning device 103. The electrostatic latent image formed on the photosensitive drum 105 is developed by the developing unit 107. The developing unit 107 has different color toners in the respective image forming units 104. The toner image formed on the photosensitive drum 105 is transferred to a recording material conveyed on the transfer belt 109. The toner remaining on the photosensitive drum 105 after being transferred to the recording material is scraped off and discarded by a blade included in the cleaning unit 108. The toner images are transferred onto the recording material in the order of the image forming unit 104a to the image forming unit 104d. Thereafter, the transferred toner image is fixed on the recording material by the fixing unit 110.

  The registration detection sensor 111 functions as a deviation amount detection unit, and detects a positional deviation of the image transferred to the recording material. Specifically, the image forming apparatus 100 forms a patch for detecting an image position shift, and the registration detection sensor 111 detects the patch. Further, the image forming apparatus 100 compares the detected patch information with the position of the regular patch to calculate the shift amount. The image forming apparatus 100 according to the present embodiment uses this deviation amount to control the image data sent to the deflection scanning device 103 during image formation, thereby eliminating the deviation amount caused by the scanning of the deflection scanning device 103. To do. Although the image forming apparatus 100 includes the registration detection sensor 111, the image forming apparatus 100 may be configured without the registration detection sensor 111. In this case, the amount of deviation is not detected by the registration detection sensor 111, but when the image forming apparatus 100 is produced in the factory, the detection of registration may be performed using a dedicated detection device. Then, the shift amount detected using the dedicated detection device may be stored in the storage unit 126 as RegUpDown [i] (i = 0, 1, 2,...) Described later. The shift amount is a shift amount of a scanning line formed by laser light emitted from a laser light source with respect to a direction (circumferential direction) perpendicular to the axial direction of the photosensitive drum 105. That is, ideally, the direction of the scanning line of the laser beam should be parallel to the axial direction of the photosensitive drum 105, but it is not necessarily ideal due to the mounting error of the laser light source or the mounting error of the photosensitive drum 105. Therefore, the amount of deviation between the scanning direction of the laser beam and the axial direction of the photosensitive drum 105 is detected (or stored in advance), and the read address of the image data stored in the storage unit 126 is adjusted to record the image on the recording material. So that the offset is offset.

  FIG. 1B is a block diagram illustrating a configuration example of the image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 is realized by, for example, an MFP (Multi Function Peripheral) that is a multifunction machine that realizes a plurality of types of functions. The image forming apparatus 100 is connected to the network via the network I / F 128, and can exchange image data and apparatus information with an external apparatus using the network. Further, the image forming apparatus 100 includes a data processing unit 121, a display unit 122, an operation unit 124, an image reading unit 125, a storage unit 126, and a printing unit 127.

  The image reading unit 125 includes a document table and an auto document feeder (ADF). The image reading unit 125 irradiates a bundle or one document with a light source, and forms a document reflection image on a solid-state image sensor with a lens. As a result, the image reading unit 125 acquires a raster-like image reading signal from the solid-state imaging device as a raster image having a predetermined density (for example, 600 DPI). Hereinafter, a paper document will be described as an example of a printed material read by the image reading unit 125. However, a printed material made of a recording material other than paper (for example, an OHP sheet, a transparent original such as a film, a cloth, or the like) is read as an image. It may be read by the unit 125.

  The printing unit 127 prints an image corresponding to the image reading signal on a recording material. For example, when copying one original image, the image forming apparatus 100 performs image processing on the image reading signal by the data processing unit 121 to generate a recording signal, and the generated recording signal is printed on the recording material by the printing unit 127. To print. On the other hand, when copying a plurality of document images, the image forming apparatus 100 stores one recording signal in the storage unit 126, and then sequentially outputs the stored recording signal to the printing unit 127. To print. Various printing controls using the printing unit 127 are controlled by a printer controller 123 included in the data processing unit 121.

  The operation unit 124 receives an operator instruction to the image forming apparatus 100, and a series of these operations is controlled by the data processing unit 121. The display unit 122 displays the state of operation input and the image data being processed. Note that the image forming apparatus 100 implements a user interface that provides a user with various operations and displays for executing various processes to be described later, using the display unit 122 and the operation unit 124.

[Printer controller]
Next, a detailed configuration of the printer controller 123 will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration example of the printer controller 123 according to the present embodiment.

  The printer controller 123 includes an operation unit I / F 301, a host I / F unit 302, an image data generation unit 303, an image memory 304, a DMA controller (direct memory access controller) 305, a blend processing unit 306, and an engine I / F 307. Further, the printer controller 123 includes a CPU 308, a ROM 309, a RAM 310, and a system bus 311.

  The host I / F unit 302 is provided with an input buffer for inputting print data sent from the data processing unit 121 and settings for instructing operation of the apparatus. In addition, the host I / F unit 302 is provided with an output buffer that temporarily holds output data including signals to be sent to the data processing unit 121 and device information data. The host I / F unit 302 constitutes an input / output unit for signals and communication packets transmitted / received to / from the data processing unit 121 and performs communication control with the data processing unit 121.

  The print data input via the host I / F unit 302 is given to the image data generation unit 303. Here, the input print data is composed of, for example, PDL (page description language) data. The image data generation unit 303 analyzes the print data input based on a predetermined analysis unit (for example, PDL analysis processing), generates an intermediate language from the analysis result, and further the printing unit (printer engine) 107 Generate processable bitmap data.

  Specifically, the image data generation unit 303 analyzes the print data and creates intermediate language information by the analysis, and performs rasterization processing in parallel with the creation of the intermediate language information. In this rasterization process, there is a conversion from the display color RGB (additive color mixture) included in the print data to YMCK (subtractive color mixture) that can be processed by the printing unit 127. In addition, there is processing such as conversion from a character code included in print data into font data such as a pre-stored bit pattern and outline font. After that, in the rasterizing process, bitmap data is created in page units or band units, pseudo gradation processing using a dither pattern is performed on the bitmap data, and bitmap data that can be printed in the printing unit 127 is generated. To do.

  The created bitmap data is stored in the image memory 304. Reading of the bitmap data stored in the image memory 304 is controlled by the DMA controller 305. The reading control of the bitmap data from the image memory 304 by the DMA controller 305 is performed based on an instruction from the CPU 308 functioning as a designation unit.

  The bitmap data read from the image memory 304 is given to a blend processing unit (combining means) 306 that performs a blend process described later. Further, the bitmap data blended by the blend processing unit 306 is transferred to the printing unit 127 as a video signal via the engine I / F unit 307. The blending process will be described later with reference to FIGS.

  The engine I / F unit 307 is provided with an output buffer that temporarily holds a video signal to be transferred to the printing unit 127 and an input buffer that temporarily holds a signal sent from the printing unit 127. The engine I / F unit 307 constitutes an input / output unit for signals transmitted to and received from the printing unit 127 and performs communication control with the printing unit 127.

  Various instructions such as an instruction regarding mode setting issued by an operation input from the operation unit 124 are input to the CPU 308 via the operation unit I / F unit 301. That is, the operation unit I / F unit 301 constitutes an interface between the operation unit 124 and the CPU 308.

  The CPU 308 comprehensively controls each block described above according to the mode instructed from the operation unit 124 or the data processing unit 121. These controls are executed based on a control program stored in the ROM 309. The control program stored in the ROM 309 includes an OS (operating system) for performing time-sharing control in units of load modules called tasks according to the system clock. The control program includes a plurality of load modules that are executed and controlled in units of functions by the OS. The RAM 310 is used as a work area for arithmetic processing by the CPU 308. Each block described above is connected to the system bus 311. The system bus 311 includes an address bus and a system bus.

[DMA controller]
Next, the details of the DMA controller 305 will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration example of the DMA controller 305 provided in the printer controller 123 according to the present embodiment. The DMA controller 305 functions as a reading unit, and includes a register unit 501, an address generation unit 502, a bus interface 503, a FIFO 504, and a blend processing unit interface 505.

  The register unit 501 includes a plurality of registers. An instruction from the CPU 308 to the DMA controller 305 is performed by writing an appropriate value to each register of the register unit 501.

  The address generation unit 502 generates an address for reading bitmap data stored in the image memory 304 with reference to the contents of each register of the register unit 501. The address generation unit 502 requests an address signal (addr) and a length signal (length) indicating the length of reading from the address using a request signal (req) to the bus interface 503.

  The bus interface 503 receives the address signal and the length signal from the address generation unit 502 and issues a read transaction to the bus 311. For example, if the data bus width of the bus 311 is 32 bits, the address signal and the length signal are decomposed into a plurality of 32-bit accesses and a read transaction is issued. When the processing for one set of address signal and length signal is completed, the bus interface 503 notifies the address generation unit 502 of the completion of processing using a response signal (ack). Upon receiving the response signal, the address generation unit 502 can request the bus interface 503 for the next address signal and length signal.

  The bitmap data read from the image memory 304 is temporarily stored in a FIFO (First In First Out buffer) 504. The DMA controller 305 stores the bitmap data in the FIFO 504 even when there is a period in which the blend processing unit 306 cannot temporarily input data. Thereby, when the blend processing unit 306 can input data, the bitmap data can be immediately supplied from the FIFO 504 to the blend processing unit 306.

  The bus interface 503 monitors the FIFO full signal (full) output from the FIFO 504 and indicating that there is no space in the FIFO to write data. When the FIFO 504 is full, the bus interface 503 waits until the full state is released without issuing a read transaction.

  The blend processing unit interface 505 transmits the bitmap data stored in the FIFO 504 to the blend processing unit 306. The blend processing unit interface 505 monitors a FIFO empty signal (empty) output from the FIFO 504 and indicating that there is no data stored in the FIFO. If the FIFO 504 is not in an empty state and the blend processing unit 306 can input data, the blend processing unit interface 505 reads bitmap data from the FIFO 504 and transmits the data to the blend processing unit 306.

[Principle of registration deviation correction]
Next, with reference to FIG. 4 and FIG. 5, the principle of image misregistration correction with respect to the recording material will be described. Hereinafter, the positional deviation of the image with respect to the recording material is referred to as registration deviation. 4 and 5 are diagrams for explaining the principle of registration deviation correction according to the present embodiment.

  Reference numeral 401 shown in FIG. 4 indicates a scanning line of one scanning line that is bent and causes registration deviation. Reference numeral 402 denotes a state in which bitmap data is sent to the printing unit 127 while switching the line in accordance with the curve of the scanning line 401. In 402, the black portion indicates data sent to the printing unit 127 by one scanning line scan. In this way, if the bitmap data is sent to the printing unit 127 while switching the line according to the bending of the scanning line, the electrostatic latent image generated on the image carrier can be obtained even by the exposure scanning in which the bending occurs. Is undistorted.

  501 shown in FIG. 5 is an enlarged view of a part of the scanning line in which the bending has occurred, which causes the registration shift. Reference numeral 502 denotes a state in which bitmap data is sent to the printing unit 127 while switching the line in accordance with the curve of the scanning line 501. However, as indicated by 502, if the lines are simply switched and the bitmap data is sent to the printing unit 127, an unnatural step occurs in the switching portion. In order to eliminate the unnatural step and smooth the image, it is necessary to combine two lines before and after the switching portion as in 503.

  The DMA controller 305 of the present invention generates an address so that the line is switched according to the bending of the scanning line in order to eliminate the need for a line buffer. That is, the line buffer for temporarily storing the bitmap data for each line is omitted by accurately reading out the necessary bitmap data. Specifically, paying attention to the fact that the data required for the blending process is the data before and after the line switching, in addition to the black portion 504, the bitmap data of the shaded portion is sent to the printing unit 127. As a result, the image forming apparatus 100 does not need to include a line buffer in order to read out necessary bitmap data from the memory and supply the data to the blend processing unit 306.

  Next, the operation of the DMA controller 305 when transferring bitmap data to the blend processing unit 306 without being inverted in the main scanning direction or the sub-scanning direction will be described with reference to FIG. In the following, one line of bitmap data is considered divided equally. Hereinafter, this divided data is referred to as a segment (divided data).

  In order to realize the DMA operation (bitmap data read operation), the register unit 501 is provided with a plurality of registers in advance. Specifically, the register unit 501 includes a register (RegSegLen) that specifies the length of each segment. In addition, the register unit 501 designates whether to switch lines between adjacent segments, switch to the upper (previous) line, or switch to the lower (next) line according to the curve of the scanning line. (RegUpDown [i]) is included as many times as necessary. Since there are three possible values for this register group, for example, “00” or “01” is set when the line is not switched, “10” is switched when the line is switched, and “10” is switched when the line is switched to the lower line. “11” is assigned.

  The register unit 501 includes a register (RegOverwrapLen), a register (RegStartAddr), a register (RegLineLen), a register (RegLineOffset), and a register (RegBeams). In the register (RegOverwrapLen), when a line is switched between adjacent segments, a length for reading before and after the switching position (data in the vicinity of the switching position) is designated. This register (RegOverwrapLen) is the number of combinations in the main scanning direction. In the register (RegStartAddr), the top address of the bitmap data stored in the image memory 304 is designated. In the register (RegLineLen), the line length of the bitmap data is specified. In the register (RegLineOffset), an offset value of an address of an adjacent line of bitmap data is designated. The number of lines to be sent to the blend processing unit 306 is designated in the register (RegBeams). Furthermore, the register unit 501 includes an activation register for starting the DMA operation after the CPU 308 completes the register setting described above.

  FIG. 9 is a flowchart showing the operation of the address generation unit 502. Here, a DMA process (data transfer method) for suitably reading out bitmap data in order to eliminate scanning line distortion will be described.

  First, in step S900, when the DMA operation is started by an instruction from the CPU 308, the address generation unit 502 initializes the signal line_start_addr and the signal line_cnt. Specifically, the address generation unit 502 initializes a signal line_start_addr that stores the start address of each line with the value of RegStartAddr. In addition, the address generation unit 502 initializes a signal line_cnt indicating the number of lines sent to the blend processing unit 306 with zero.

  In step S901, the address generation unit 502 performs initialization for each line. Specifically, the address generation unit 502 initializes a signal seg_addr indicating the start address of the segment with the value of line_start_addr, and initializes a signal line_data_cnt that counts the processed amount in the line with zero. Further, the address generation unit 502 initializes a signal index indicating the index of the register group RegUpDown [i] to be referred to with 0.

  In step S902, the address generation unit 502 performs initialization for each segment. Specifically, the address generation unit 502 initializes signals (addr and length) indicating the address and length to be requested to the bus interface 503 with the signal seg_addr indicating the start address of the segment and the value of the register RegSegLen, respectively.

  In step S903, the address generation unit 502 makes a read request to the bus interface 503 with the signals addr and length. Note that the read request in step S903 is a request to read data while subtracting the address in the main scanning direction.

  In step S904, the address generation unit 502 updates the signal seg_addr indicating the start address of the segment to the start address of the next segment, so that the line switching signal RegUpDown [index] is provided on the rear side (next segment side) of the current segment. ] Is determined. When there is no line switching at the rear side of the segment, that is, when the value of the line switching signal RegUpDown [index] is “00” or “01”, the address generation unit 502 shifts the processing to step S907. Further, when switching to the upper line, that is, when the value of the line switching signal RegUpDown [index] is “10”, the address generating unit 502 shifts the processing to step S105. Further, when the line is switched to the lower line, that is, when the value of the line switching signal RegUpDown [index] is “11”, the address generation unit 502 shifts the processing to step S906.

  In step S905, the address generation unit 502 adds the value of the register RegLineOffset to the signal seg_addr in order to switch the segment start address to the upper line, and causes the process to transition to S907. The process of adding RegSegLen to this value as the start address of the next segment is performed in step S907 described later.

  In step S906, the address generation unit 502 subtracts the value of the register RegLineOffset from the signal seg_addr in order to switch the segment start address to the lower line, and causes the process to transition to S907. The process of adding RegSegLen to this value as the start address of the next segment is performed in step S907 described later.

  In step S907, the address generation unit 502 updates each signal for processing of the next segment. Specifically, the address generation unit 502 adds the value of the register RegSegLen to the segment start address signal seg_addr. The address generation unit 502 also adds the value of the register RegSegLen to the signal line_data_cnt that counts the processed amount in the line. Furthermore, the address generation unit 502 increments the signal index by 1 in order to advance the register RegUpDown [i] to be referred to by one.

  In step S908, the address generation unit 502 compares the value obtained by subtracting the value of line_data_cnt from the value of the register RegLineLen with the value of RegSegLen, and determines the end of the line. If the difference is larger than the value of RegSegLen, the address generation unit 502 has two or more segments to be processed. Therefore, the process returns to step S902, and the segment processing is repeated. On the other hand, if the difference is equal to or smaller than the value of RegSegLen, the address generation unit 502 proceeds to the process of step S909 in order to process the last segment in the line.

  In step S909, the address generation unit 502 updates each signal for processing of the next line. Specifically, the address generation unit 502 adds the value of the register RegLineOffset to the signal line_start_addr that stores the start address of each line, and updates the start address of each line so that it becomes the start address of the next line. The address generation unit 502 increments the signal line_cnt indicating the number of lines sent to the blend processing unit 306 by one.

  In step S910, the address generation unit 502 compares the signal line_cnt with the value of the register RegBeams and determines the end of the page. Specifically, if the value of the signal line_cnt is less than the value of the register RegBeams, the address generation unit 502 returns to the processing in step S901 because the line to be processed exists, and repeats the processing of the line. On the other hand, if the value of the signal line_cnt is greater than or equal to the value of the register RegBeams, the address generation unit 502 ends the DMA operation. When the DMA operation is completed, the DMA controller 305 sends an interrupt to the CPU 308. The CPU 308 detects the end of the DMA operation by detecting this interrupt.

  In the above description, the data transfer method according to the present invention is realized by the DMA controller 305. However, if the CPU 308 has a sufficient processing time, it may be realized by the CPU 308. Further, it may be realized by a second CPU (central processing unit) other than the CPU 308 or a DSP (digital signal processor).

  Furthermore, in the image forming apparatus, when the developing unit is composed of developing units corresponding to each of a plurality of colors (CYMK), the data transfer method according to the present invention is realized for each color, thereby registering each color. Color shift due to shift can be prevented.

[First Embodiment]
Hereinafter, the first embodiment will be described with reference to FIG. In this embodiment, the operation of the DMA controller 305 in the main scanning direction inversion method in which the bitmap data is inverted (mirror image) in the main scanning direction will be described. In the present embodiment, one line of bitmap data is considered to be divided equally. Hereinafter, this divided data is referred to as a segment (divided data).

  In order to realize the DMA operation (bitmap data read operation) according to the present embodiment, the register unit 501 includes a plurality of registers in advance. Specifically, the register unit 501 includes a register (RegSegLen) that specifies the length of each segment. In addition, the register unit 501 designates whether to switch lines between adjacent segments, switch to the upper (previous) line, or switch to the lower (next) line according to the curve of the scanning line. (RegUpDown [i]) is included as many times as necessary. Since there are three possible values for this register group, for example, “00” or “01” is set when the line is not switched, “10” is switched when the line is switched, and “10” is switched when the line is switched to the lower line. “11” is assigned.

  The register unit 501 includes a register (RegOverwrapLen), a register (RegStartAddr), a register (RegLineLen), a register (RegLineOffset), and a register (RegBeams). In the register (RegOverwrapLen), when a line is switched between adjacent segments, a length for reading before and after the switching position (data in the vicinity of the switching position) is designated. This register (RegOverwrapLen) is the number of combinations in the main scanning direction. In the register (RegStartAddr), the top address of the bitmap data stored in the image memory 304 is designated. In the register (RegLineLen), the line length of the bitmap data is specified. In the register (RegLineOffset), an offset value of an address of an adjacent line of bitmap data is designated. The number of lines to be sent to the blend processing unit 306 is designated in the register (RegBeams). Furthermore, the register unit 501 includes an activation register for starting the DMA operation after the CPU 308 completes the register setting described above.

  FIG. 6 is a flowchart showing the operation of the address generation unit 502 according to the first embodiment. Here, a DMA process (data transfer method) for suitably reading out bitmap data in order to eliminate scanning line distortion will be described.

  First, in step S100, when the DMA operation is started by an instruction from the CPU 308, the address generation unit 502 initializes the signal line_start_addr and the signal line_cnt. Specifically, the address generation unit 502 initializes a signal line_start_addr that stores the start address of each line with a value of RegStartAddr + (RegLineLen−1). In addition, the address generation unit 502 initializes a signal line_cnt indicating the number of lines sent to the blend processing unit 306 with zero.

  In step S101, the address generation unit 502 performs initialization for each line. Specifically, the address generation unit 502 initializes a signal seg_addr indicating the start address of the segment with the value of line_start_addr, and initializes a signal line_data_cnt that counts the processed amount in the line with zero. Further, the address generation unit 502 initializes a signal index indicating the index of the register group RegUpDown [i] to be referred to with 0.

  In step S102, the address generation unit 502 performs initialization for each segment. Specifically, the address generation unit 502 initializes signals (addr and length) indicating the address and length to be requested to the bus interface 503 with the signal seg_addr indicating the start address of the segment and the value of the register RegSegLen, respectively.

  In step S103, the address generation unit 502 makes a read request to the bus interface 503 with the signals addr and length. The read request in step S103 is a request for reading data while subtracting the address in the main scanning direction.

  In step S104, the address generation unit 502 updates the signal seg_addr indicating the start address of the segment to the start address of the next segment, so that the line switching signal RegUpDown [index] is provided on the rear side (next segment side) of the current segment. ] Is determined. When there is no line switching on the rear side of the segment, that is, when the value of the line switching signal RegUpDown [index] is “00” or “01”, the address generation unit 502 shifts the processing to step S107. Further, when switching to the upper line, that is, when the value of the line switching signal RegUpDown [index] is “10”, the address generating unit 502 shifts the processing to step S105. Further, when the line is switched to the lower line, that is, when the value of the line switching signal RegUpDown [index] is “11”, the address generation unit 502 shifts the processing to step S106.

  In step S105, the address generation unit 502 adds the value of the register RegLineOffset to the signal seg_addr in order to switch the segment start address to the upper line, and causes the process to transition to S107. The process of adding RegSegLen to this value as the start address of the next segment is performed in step S107 described later.

  In step S106, the address generation unit 502 subtracts the value of the register RegLineOffset from the signal seg_addr to switch the segment start address to the lower line, and shifts the process to S107. The process of adding RegSegLen to this value as the start address of the next segment is performed in step S107 described later.

  In step S107, the address generation unit 502 updates each signal for processing of the next segment. Specifically, the address generation unit 502 subtracts the value of the register RegSegLen from the start address signal seg_addr of the segment. The address generation unit 502 also adds the value of the register RegSegLen to the signal line_data_cnt that counts the processed amount in the line. Furthermore, the address generation unit 502 increments the signal index by 1 in order to advance the register RegUpDown [i] to be referred to by one.

  In step S108, the address generation unit 502 compares the value obtained by subtracting the value of line_data_cnt from the value of the register RegLineLen with the value of RegSegLen, and determines the end of the line. If the difference is larger than the value of RegSegLen, the address generator 502 has two or more segments to be processed. Therefore, the process returns to step S102 and repeats the segment processing. On the other hand, if the difference is equal to or smaller than the value of RegSegLen, the address generation unit 502 proceeds to the process of step S109 in order to process the last segment in the line.

  In step S109, the address generation unit 502 updates each signal for processing the next line. Specifically, the address generation unit 502 adds the value of the register RegLineOffset to the signal line_start_addr that stores the start address of each line, and updates the start address of each line so that it becomes the start address of the next line. The address generation unit 502 increments the signal line_cnt indicating the number of lines sent to the blend processing unit 306 by one.

  In step S110, the address generation unit 502 compares the signal line_cnt with the value of the register RegBeams and determines the end of the page. Specifically, if the value of the signal line_cnt is less than the value of the register RegBeams, the address generation unit 502 returns to the processing in step S101 because the line to be processed exists, and repeats the processing of the line. On the other hand, if the value of the signal line_cnt is greater than or equal to the value of the register RegBeams, the address generation unit 502 ends the DMA operation. When the DMA operation is completed, the DMA controller 305 sends an interrupt to the CPU 308. The CPU 308 detects the end of the DMA operation by detecting this interrupt.

  In the above description, the data transfer method according to the present invention is realized by the DMA controller 305. However, if the CPU 308 has a sufficient processing time, it may be realized by the CPU 308. Further, it may be realized by a second CPU (central processing unit) other than the CPU 308 or a DSP (digital signal processor).

  Furthermore, in the image forming apparatus, when the developing unit is composed of developing units corresponding to each of a plurality of colors (CYMK), the data transfer method according to the present invention is realized for each color, thereby registering each color. Color shift due to shift can be prevented.

  As described above, the image forming apparatus according to the present embodiment reads the image data stored in the memory in the apparatus based on the deviation of the scanning line by the deflection scanning apparatus 103 and transfers it to the deflection scanning apparatus 103. By doing so, image formation is performed. Specifically, when the image data of one scanning line is read, the image forming apparatus also reads the image data of other lines with respect to the image data at the position where the scanning line shift occurs. The read image data of the other lines are combined with the corresponding image data of the current line. As described above, the image forming apparatus can provide only necessary image data to the blend processing unit 306 that combines the above-described image data. Therefore, this image forming apparatus does not need to prepare a plurality of line buffers as in the prior art, and can reduce cost and circuit scale. As described above, it is possible not only to switch the lines at the position where the scanning line is displaced, but also to combine the plurality of image data to suppress the occurrence of an unnatural step in the formed image.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the image forming apparatus may specify the number of other lines and the number of combinations in the main scanning direction when specifying the image data of the other lines. Thus, the image forming apparatus can provide only necessary image data to the blend processing unit 306 with higher accuracy. The number of combinations in the main scanning direction may be information indicating the number of pixels (number of dots) before and after the switching position at which switching to another line is performed during scanning of one line.

  In addition, the image forming apparatus may read image data by further specifying whether the other line is the previous line or the next line with respect to the current line. As a result, the image forming apparatus can change the combined line according to the inclination of the shift of the scanning line, and can form a more accurate image. In addition, the image forming apparatus divides the image data of one scanning line into equal parts, and specifies whether to switch to the previous line, to the next line, or no switching for each divided data. Then, the image data may be read out.

  Furthermore, it is desirable that the above-described read control is performed line by line. As a result, necessary image data can be sequentially read out, and there is no need to prepare a plurality of line buffers as in the prior art.

[Second Embodiment]
Next, a second embodiment will be described with reference to FIG. In the present embodiment, unlike the first embodiment, the operation of the DMA controller 305 in the case of a sub-scanning direction inversion method in which bitmap image data is inverted (mirror image) in the sub-scanning direction will be described. In the present embodiment, one line of bitmap data is considered to be divided equally. Hereinafter, this divided data is referred to as a segment.

  In order to realize the DMA operation according to the present embodiment, the register unit 501 is provided with a plurality of registers in advance. Specifically, the register unit 501 includes a register (RegSegLen) that specifies the length of each segment. The register unit 501 also registers (RegUpDown [i]) that specifies whether the line is not switched between adjacent segments, the upper line, or the lower line in accordance with the curve of the scanning line. Is included as many times as necessary. Since there are three possible values for this register group, for example, “00” or “01” is set when the line is not switched, “10” is switched when the line is switched, and “10” is switched when the line is switched to the lower line. “11” is assigned.

  The register unit 501 includes a register (RegOverwrapLen), a register (RegStartAddr), a register (RegLineLen), a register (RegLineOffset), and a register (RegBeams). The register (RegOverwrapLen) is designated with a length that leads before and after the switching position when a line is switched between adjacent segments. This register (RegOverwrapLen) is the number of combinations in the main scanning direction. In the register (RegStartAddr), the top address of the bitmap data stored in the image memory 304 is designated. In the register (RegLineLen), the line length of the bitmap data is specified. In the register (RegLineOffset), an offset value of an address of an adjacent line of bitmap data is designated. The number of lines to be sent to the blend processing unit 306 is designated in the register (RegBeams). Furthermore, the register unit 501 includes an activation register for starting the DMA operation after the CPU 308 completes the register setting described above.

  FIG. 7 is a flowchart showing the operation of the address generation unit 502 according to the second embodiment. Here, a DMA process (data transfer method) for suitably reading out bitmap data in order to eliminate scanning line distortion will be described.

  First, in step S200, when the DMA operation is started by an instruction from the CPU 308, the address generation unit 502 initializes the signal line_start_addr and the signal line_cnt. Specifically, the address generation unit 502 initializes a signal line_start_addr that stores the start address of each line with a value of RegStartAddr + RegLineOffset * (RegBeams−1). In addition, the address generation unit 502 initializes a signal line_cnt indicating the number of lines sent to the blend processing unit 306 with zero.

  In step S201, the address generation unit 502 performs initialization for each line. Specifically, the address generation unit 502 initializes a signal seg_addr indicating the start address of the segment with the value of line_start_addr, and initializes a signal line_data_cnt that counts the processed amount in the line with zero. Further, the address generation unit 502 initializes a signal index indicating the index of the register group RegUpDown [i] to be referred to with 0.

  In step S202, the address generation unit 502 performs initialization for each segment. Specifically, the address generation unit 502 initializes signals (addr and length) indicating the address and length to be requested to the bus interface 503 with the signal seg_addr indicating the start address of the segment and the value of the register RegSegLen, respectively.

  In step S203, the address generation unit 502 makes a read request to the bus interface 503 with the signals addr and length.

  In step S204, the address generation unit 502 determines the value of the line switching signal RegUpDown [index] behind the current segment in order to update the signal seg_addr indicating the start address of the segment to the start address of the next segment. . When there is no line switching on the rear side of the segment, that is, when the value of the line switching signal RegUpDown [index] is “00” or “01”, the address generation unit 502 shifts the processing to step S207. Further, when switching to the upper line, that is, when the value of the line switching signal RegUpDown [index] is “10”, the address generation unit 502 shifts the process to step S205. Further, when the line is switched to the lower line, that is, when the value of the line switching signal RegUpDown [index] is “11”, the address generation unit 502 shifts the processing to step S206.

  In step S205, the address generation unit 502 adds the value of the register RegLineOffset to the signal seg_addr to switch the segment start address to the upper line, and causes the process to transition to S207. The process of adding RegSegLen to this value for the start address of the next segment is performed in step S207 described later.

  In step S206, the address generation unit 502 subtracts the value of the register RegLineOffset from the signal seg_addr to switch the segment start address to the lower line, and shifts the process to S207. The process of adding RegSegLen to this value for the start address of the next segment is performed in step S207 described later.

  In step S207, the address generation unit 502 updates each signal for processing of the next segment. Specifically, the address generation unit 502 adds the value of the register RegSegLen to the segment start address signal seg_addr. The address generation unit 502 also adds the value of the register RegSegLen to the signal line_data_cnt that counts the processed amount in the line. Furthermore, the address generation unit 502 increments the signal index by 1 in order to advance the register RegUpDown [i] to be referred to by one.

  In step S208, the address generation unit 502 compares the value obtained by subtracting the value of line_data_cnt from the value of the register RegLineLen with the value of RegSegLen, and determines the end of the line. If the difference is larger than the value of RegSegLen, the address generator 502 has two or more segments to be processed. Therefore, the process returns to step S202, and the segment processing is repeated. On the other hand, if the difference is equal to or less than the value of RegSegLen, the address generation unit 502 proceeds to the process of step S209 in order to process the last segment in the line.

  In step S209, the address generation unit 502 updates each signal for processing of the next line. Specifically, the address generation unit 502 subtracts the value of the register RegLineOffset from the signal line_start_addr that stores the start address of each line, and updates it so that the start address of each line becomes the start address of the next line. The address generation unit 502 increments the signal line_cnt indicating the number of lines sent to the blend processing unit 306 by one.

  In step S210, the address generation unit 502 compares the signal line_cnt with the value of the register RegBeams and determines the end of the page. Specifically, if the value of the signal line_cnt is less than the value of the register RegBeams, the address generation unit 502 returns the process to step S201 because the line to be processed exists, and repeats the process of the line. On the other hand, if the value of the signal line_cnt is greater than or equal to the value of the register RegBeams, the address generation unit 502 ends the DMA operation. When the DMA operation is completed, the DMA controller 305 sends an interrupt to the CPU 308. The CPU 308 detects the end of the DMA operation by detecting this interrupt.

  In the above description, the data transfer method according to the present invention is realized by the DMA controller 305. However, if the CPU 308 has a sufficient processing time, it may be realized by the CPU 308. Further, it may be realized by a second CPU other than the CPU 308 or a DSP (digital signal processor).

  Further, in the color image forming apparatus, when the developing unit is composed of developing units corresponding to each color of a plurality of colors (CYMK), the data transfer method of the present invention is realized for each color, thereby registering each color. Color misregistration due to misregistration can be prevented.

  As described above, the image forming apparatus according to the present embodiment can realize the same control as the first embodiment and obtain the same effect even in the transfer method using the sub-scanning direction inversion method. it can.

[Third Embodiment]
Hereinafter, a third embodiment will be described with reference to FIG. In the present embodiment, the operation of the DMA controller 305 in the case of a 180-degree rotation method that rotates bitmap image data by 180 degrees will be described. In the present embodiment, one line of bitmap data is considered to be divided equally. Hereinafter, this divided data is referred to as a segment.

  In order to realize the DMA operation (bitmap data read operation) according to the present embodiment, the register unit 501 includes a plurality of registers in advance. Specifically, the register unit 501 includes a register (RegSegLen) that specifies the length of each segment. In addition, the register unit 501 registers (RegUpDown [i]) that specifies whether to switch the line between adjacent segments, switch to the upper line, or switch to the lower line in accordance with the curve of the scanning line. Is included as many times as necessary. Since there are three possible values for this register group, for example, “00” or “01” is set when the line is not switched, “10” is switched when the line is switched, and “10” is switched when the line is switched to the lower line. “11” is assigned.

  The register unit 501 includes a register (RegOverwrapLen), a register (RegStartAddr), a register (RegLineLen), a register (RegLineOffset), and a register (RegBeams). The register (RegOverwrapLen) is designated with a length that leads before and after the switching position when a line is switched between adjacent segments. This register (RegOverwrapLen) is the number of combinations in the main scanning direction. In the register (RegStartAddr), the top address of the bitmap data stored in the image memory 304 is designated. In the register (RegLineLen), the line length of the bitmap data is specified. In the register (RegLineOffset), an offset value of an address of an adjacent line of bitmap data is designated. The number of lines to be sent to the blend processing unit 306 is designated in the register (RegBeams). Furthermore, the register unit 501 includes an activation register for starting the DMA operation after the CPU 308 completes the register setting described above.

  FIG. 8 is a flowchart showing the operation of the address generation unit 502 according to the third embodiment. Here, a DMA process (data transfer method) for suitably reading out bitmap data in order to eliminate scanning line distortion will be described.

  First, in step S300, when the DMA operation is started by an instruction from the CPU 308, the address generation unit 502 initializes the signal line_start_addr and the signal line_cnt. Specifically, the address generation unit 502 initializes a signal line_start_addr that stores the start address of each line with a value of RegStartAddr + (RegLineLen−1) + RegLineOffset * (RegBeams−1). In addition, the address generation unit 502 initializes a signal line_cnt indicating the number of lines sent to the blend processing unit 306 with zero.

  In step S301, the address generation unit 502 performs initialization for each line. Specifically, the address generation unit 502 initializes a signal seg_addr indicating the start address of the segment with the value of line_start_addr, and initializes a signal line_data_cnt that counts the processed amount in the line with zero. Further, the address generation unit 502 initializes a signal index indicating the index of the register group RegUpDown [i] to be referred to with 0.

  In step S302, the address generation unit 502 performs initialization for each segment. Specifically, the address generation unit 502 initializes signals (addr and length) indicating the address and length to be requested to the bus interface 503 with the signal seg_addr indicating the start address of the segment and the value of the register RegSegLen, respectively.

  In step S303, the address generation unit 502 makes a read request to the bus interface 503 with the signals addr and length. Note that the read request in step S303 is a request to read data while subtracting the address in the main scanning direction.

  In step S304, the address generation unit 502 determines the value of the line switching signal RegUpDown [index] behind the current segment in order to update the signal seg_addr indicating the start address of the segment to the start address of the next segment. . When there is no line switching at the rear side of the segment, that is, when the value of the line switching signal RegUpDown [index] is “00” or “01”, the address generation unit 502 shifts the processing to step S307. Further, when switching to the upper line, that is, when the value of the line switching signal RegUpDown [index] is “10”, the address generation unit 502 shifts the processing to step S305. Furthermore, when the line is switched to the lower line, that is, when the value of the line switching signal RegUpDown [index] is “11”, the address generation unit 502 shifts the processing to step S306.

  In step S305, the address generation unit 502 adds the value of the register RegLineOffset to the signal seg_addr to switch the segment start address to the upper line, and causes the process to transition to S307. The process of adding RegSegLen to this value as the start address of the next segment is performed in step S307 described later.

  In step S306, the address generation unit 502 subtracts the value of the register RegLineOffset from the signal seg_addr to switch the segment start address to the lower line, and causes the process to transition to S307. The process of adding RegSegLen to this value as the start address of the next segment is performed in step S307 described later.

  In step S307, the address generation unit 502 updates each signal for processing the next segment. Specifically, the address generation unit 502 subtracts the value of the register RegSegLen from the start address signal seg_addr of the segment. The address generation unit 502 also adds the value of the register RegSegLen to the signal line_data_cnt that counts the processed amount in the line. Furthermore, the address generation unit 502 increments the signal index by 1 in order to advance the register RegUpDown [i] to be referred to by one.

  In step S308, the address generation unit 502 compares the value obtained by subtracting the value of line_data_cnt from the value of the register RegLineLen with the value of RegSegLen, and determines the end of the line. If the difference is larger than the value of RegSegLen, the address generator 502 has two or more segments to be processed. Therefore, the process returns to step S102 and repeats the segment processing. On the other hand, if the difference is equal to or smaller than the value of RegSegLen, the address generation unit 502 proceeds to the process of step S309 in order to process the last segment in the line.

  In step S309, the address generation unit 502 updates each signal for processing of the next line. Specifically, the address generation unit 502 subtracts the value of the register RegLineOffset from the signal line_start_addr that stores the start address of each line, and updates it so that the start address of each line becomes the start address of the next line. The address generation unit 502 increments the signal line_cnt indicating the number of lines sent to the blend processing unit 306 by one.

  In step S310, the address generation unit 502 compares the signal line_cnt with the value of the register RegBeams and determines the end of the page. Specifically, if the value of the signal line_cnt is less than the value of the register RegBeams, the address generation unit 502 returns to the process in step S301 because the line to be processed exists, and repeats the process of the line. On the other hand, if the value of the signal line_cnt is greater than or equal to the value of the register RegBeams, the address generation unit 502 ends the DMA operation. When the DMA operation is completed, the DMA controller 305 sends an interrupt to the CPU 308. The CPU 308 detects the end of the DMA operation by detecting this interrupt.

  In the above description, the data transfer method according to the present invention is realized by the DMA controller 305. However, if the CPU 308 has a sufficient processing time, it may be realized by the CPU 308. Further, it may be realized by a second CPU other than the CPU 308 or a DSP (digital signal processor).

  Further, in the color image forming apparatus, when the developing unit is composed of developing units corresponding to each color of a plurality of colors (CYMK), the data transfer method of the present invention is realized for each color, thereby registering each color. Color misregistration due to misregistration can be prevented.

  As described above, the image forming apparatus according to the present embodiment can realize the same control as in the first embodiment even in the transfer method using the 180-degree rotation method, and can obtain the same effect. .

1 is a cross-sectional view illustrating an example of an image forming apparatus 100 according to an embodiment. 1 is a block diagram illustrating a configuration example of an image forming apparatus 100 according to an embodiment. 3 is a block diagram illustrating a configuration example of a printer controller 123 according to the present embodiment. FIG. 3 is a block diagram illustrating a configuration example of a DMA controller 305 provided in the printer controller 123 according to the present embodiment. FIG. It is a figure for demonstrating the principle of the registration deviation correction which concerns on this embodiment. It is a figure for demonstrating the principle of the registration deviation correction which concerns on this embodiment. 6 is a flowchart illustrating an operation of an address generation unit 502 according to the first embodiment. 10 is a flowchart illustrating an operation of an address generation unit 502 according to the second embodiment. It is a flowchart which shows operation | movement of the address generation part 502 which concerns on 3rd Embodiment. 5 is a flowchart showing an operation of an address generation unit 502.

Explanation of symbols

100: image forming apparatus 121: data processing unit 122: display unit 123: printer controller 124: operation unit 125: image reading unit 126: storage unit 127: printing unit 128: network I / F
301: Operation unit I / F unit 302: Host I / F unit 303: Image data generation unit 304: Image memory 305: DMA controller 306: Blend processing unit 307: Engine I / F unit 308: CPU
309: ROM
310: RAM
501: Register unit 502: Address generation unit 503: Bus interface 504: FIFO
505: Blend processing unit interface

Claims (8)

Exposure means for exposing the image carrier;
Of the image data stored in the image forming apparatus, the image data used for one scan line based on the amount of deviation of the scan line formed by exposure by the exposure means with respect to the image carrier, Designating means for designating a switching position for switching to image data of another line in order to eliminate the deviation of the scanning line,
Reading means for reading out the corresponding image data according to the designated image data and the switching position;
Among the read image data, the image data in the vicinity of the switching position is combined with the image data of another line, the combination means for transferring to the exposure means,
The designation means is:
As a method for reading out image data stored in the image forming apparatus and transferring it to the exposure means, further designate any one of a transfer method of a main scanning direction inversion method, a sub-scanning direction inversion method, or a 180 degree rotation method,
The image forming apparatus, wherein the reading unit reads image data in the order according to the transfer method. The designation means is:
Further specifying the number of other lines combined by the combination means and the number of combinations in the main scanning direction;
The reading means includes
The image forming apparatus according to claim 1, wherein image data of another line corresponding to the number of lines and the number of combinations in the main scanning direction is read together with the image data of the one scanning line.   The image forming apparatus according to claim 2, wherein the number of combinations in the main scanning direction is information indicating the number of pixels from the switching position to the front and rear. The designation means is:
The image forming apparatus according to claim 2, further specifying whether the other line is a previous line or a next line with respect to a current line. The designation means is:
The switching position is divided by equally dividing the image data of the one scanning line, and for each of the divided divided data, switching to the previous line, switching to the next line, or no switching is performed. The image forming apparatus according to claim 2, wherein the image forming apparatus is designated. The reading means includes
6. The image forming apparatus according to claim 1, wherein reading of the next line is started when reading of the one scanning line is completed. The designation means is a central processing unit provided in the image forming apparatus, or a digital signal processor,
The image forming apparatus according to claim 1, wherein the reading unit is a direct memory access controller. A data transfer method for an image forming apparatus comprising an exposure means for exposing an image carrier,
Of the image data stored in the image forming apparatus, the image data used for one scan line based on the amount of deviation of the scan line formed by exposure by the exposure means with respect to the image carrier, And a switching position for switching to image data of another line in order to eliminate the shift of the scanning line,
Reading out the corresponding image data according to the designated image data and the switching position;
A step of combining image data of another line with image data in the vicinity of the switching position among the read image data, and transferring the image data to the exposure unit;
The specifying step includes:
As a method for reading out image data stored in the image forming apparatus and transferring it to the exposure means, further designate any one of a transfer method of a main scanning direction inversion method, a sub-scanning direction inversion method, or a 180 degree rotation method,
The data reading method characterized in that the reading step reads image data in the order according to the transfer method.

Images