Image forming device

Abstract

To perform lighting control of each light emitting element of an exposure device having a plurality of light emitting elements.SOLUTION: An image forming device 1 comprises: an exposure head (106) which has a photoreceptor (102) and a plurality of light emitting elements (602) and makes the plurality of light emitting elements expose the photoreceptor (102) to form an image; and an image controller 700 that performs lighting control of the plurality of light emitting elements. The image controller 700 comprises an image data processing part 703 that performs predetermined image processing to image data for forming the image to generate print image data, and a PG part 1316 for controlling light emission that generates PG pattern data for individually performing lighting control of the plurality of light emitting elements (602). The print image data are transmitted to the exposure head (106) in order to form the image, and the PG pattern data are transmitted to the exposure head (106) in order to confirm whether the plurality of light emitting elements (602) are operated normally or not.SELECTED DRAWING: Figure 15

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus equipped with an exposure device having a plurality of light-emitting elements. [Background technology]

[0002] Electrophotographic image forming apparatuses form images by using toner to develop an electrostatic latent image formed by exposing a rotating photosensitive member to light. Patent Document 1 discloses an image forming apparatus that employs a configuration in which an exposure device that exposes the photosensitive member is equipped with a plurality of light-emitting units, each equipped with a plurality of light-emitting elements. This image forming apparatus adjusts the illumination level of each light-emitting unit based on the results of reading, with a scanner, an image of a predetermined image density formed using the exposure device. An image formed to adjust the image density or geometric characteristics (position, shape, etc.) of the image is hereinafter referred to as an "adjustment image." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-118194 Summary of the Invention [Problem to be solved by the invention]

[0004] When using an exposure device with multiple light-emitting elements arranged in a plane, it is necessary to adjust the light intensity of each light-emitting element individually and check for lighting defects in order to stabilize the image quality. For this purpose, the on / off of each light-emitting element is controlled and the status at the time of control is checked. In such cases, an adjustment image is used to operate each light-emitting element.

[0005] Image data for forming an adjustment image is generated by a pattern generator during image processing performed during image formation. The pattern generator is used to debug and check the operation of modules that perform image processing during the manufacture of an image processing device. For this reason, the pattern generator is provided upstream of the modules that perform image processing. When adjusting image density or geometric characteristics, the image data generated by the pattern generator is processed by the modules, and then the adjustment image is formed.

[0006] The image data generated by the pattern generator may be processed by a downstream image processing module, which may change the image size and resolution. When controlling the on / off of multiple light-emitting elements, the image data is generated to individually control the on / off of the multiple light-emitting elements. However, this type of image processing makes it difficult to individually control the on / off of the light-emitting elements. For example, the image data may control the on / off of light-emitting elements that are different from the light-emitting elements targeted for on / off control. This makes it difficult to adjust the light intensity of the multiple light-emitting elements and check for lighting problems, which may result in a decrease in the quality of the generated image.

[0007] SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is a primary object of the present invention to provide an image forming apparatus that controls the lighting of each light-emitting element of an exposure device having a plurality of light-emitting elements. [Means for solving the problem]

[0008] The image forming apparatus of the present invention comprises a photosensitive member, an exposure means having a plurality of light-emitting elements and exposing the photosensitive member to the plurality of light-emitting elements to form an image, and a control means for controlling the lighting of the plurality of light-emitting elements, wherein the control means comprises: an image processing means for performing predetermined image processing on first image data for forming the image; a generation means provided downstream of the image processing means for generating second image data for individually controlling the lighting of the plurality of light-emitting elements; and a light-emitting control means for transmitting the first image data that has undergone the image processing to the exposure means when forming the image, and transmitting the second image data to the exposure means when checking whether the plurality of light-emitting elements are operating normally. [Effects of the Invention]

[0009] According to the present invention, it is possible to accurately control the lighting of each light-emitting element in an exposure apparatus having a plurality of light-emitting elements. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus. [Figure 2] 1A and 1B are explanatory diagrams of a photosensitive member and an exposure head. [Figure 3] (a) and (b) are explanatory diagrams of a printed circuit board. [Figure 4] FIG. [Figure 5] FIG. [Figure 6] Cross section AA of Figure 5. [Figure 7] FIG. 3 is a diagram illustrating the configuration of an image controller. [Figure 8] 10 is a timing chart for writing control data. [Figure 9] 10 is a timing chart for transmitting print image data. [Figure 10] Detailed functional diagram of one light-emitting chip. [Figure 11] FIG. [Figure 12]5A and 5B are explanatory diagrams of output control by a light emission control unit. [Figure 13] 5A and 5B are explanatory diagrams of output control by a light emission control unit. [Figure 14] FIG. 4 is an explanatory diagram of output control of a light emission control unit. [Figure 15] FIG. 2 is a detailed configuration diagram of an image controller. [Figure 16] FIG. 3 is a diagram illustrating the configuration of a light emission control unit. [Figure 17] 4 is a timing chart showing the transmission of print image data. [Figure 18] 4 is a timing chart showing the operation of the light emission control unit. [Figure 19] (a) and (b) are explanatory diagrams of the all-lights-off pattern. [Figure 20] (a) and (b) are explanatory diagrams of all lighting patterns. [Figure 21] FIG. 10 is an explanatory diagram of block lighting patterns. [Figure 22] (a) and (b) are explanatory diagrams of the lighting settings for the block lighting pattern. [Figure 23] FIG. [Figure 24] (a) and (b) are explanatory diagrams of lighting settings for arbitrary lighting patterns. [Figure 25] (a) and (b) are explanatory diagrams of lighting settings for arbitrary lighting patterns. [Figure 26] FIG. 4 is an explanatory diagram of each line lighting pattern. [Figure 27] (a) and (b) are example diagrams showing the settings for each line lighting pattern. [Figure 28] (a) and (b) are examples of setting an arbitrary lighting pattern. [Figure 29] FIG. 10 is a diagram showing the configuration of a PG unit for light emission control. [Figure 30] 10 is a flowchart showing a process for generating PG pattern data. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0012] (Image forming device) 1 is a diagram showing the configuration of an image forming apparatus according to this embodiment. Image forming apparatus 1 includes a reading unit 100, an image creating unit 103, a fixing unit 104, and a conveying unit 105. Reading unit 100 optically reads an original placed on a platen to generate read image data. Image creating unit 103 forms an image on a sheet based on the read image data generated by reading unit 100 or print image data acquired from an external device via a network. Such image forming apparatus 1 may be realized by, for example, a copier, a multifunction peripheral, or an MFP (Multi Function Peripheral).

[0013] The image forming unit 103 has multiple image forming units 101a, 101b, 101c, and 101d, a transfer belt 111 that transports sheets, and an optical sensor 113. The image forming units 101a, 101b, 101c, and 101d are used to form toner images of black (K), yellow (Y), magenta (M), and cyan (C), respectively. The image forming units 101a, 101b, 101c, and 101d have the same configuration, and will hereinafter be collectively referred to as image forming unit 101.

[0014] The image forming unit 101 includes a photoconductor 102, a charger 107, an exposure head 106, and a developing unit 108. The photoconductor 102 is a drum-shaped image carrier having a photosensitive layer on its surface. The photoconductor 102 is driven to rotate clockwise in FIG. 1 around the drum axis. The charger 107 uniformly charges the surface of the rotating photoconductor 102 to a predetermined potential with a predetermined polarity. The exposure head 106 is an exposure device that exposes the uniformly charged surface of the photoconductor 102 to light to form an electrostatic latent image on the surface of the photoconductor 102. As will be described in detail later, the exposure head 106 of this embodiment has a configuration in which multiple light-emitting elements are arranged in a plane.

[0015] The developing unit 108 develops the electrostatic latent image formed on the photoconductor 102 with a developer (e.g., toner) to form a toner image on the surface of the photoconductor 102. The toner images formed on the surface of the photoconductor 102 are sequentially transferred to a sheet transported on a transfer belt 111. The toner images of the four photoconductors 102 are superimposed and transferred to the sheet. As a result, a color image containing four color components, black, yellow, magenta, and cyan, is formed on the sheet. The optical sensor 113 optically reads the adjustment image formed on the transfer belt 111 by the image forming unit 101.

[0016] The conveying unit 105 controls the feeding of sheets. Sheets can be fed from the internal storage units 109a and 109b, the external storage unit 109c, and the manual feed unit 109d. The conveying unit 105 feeds a sheet from any one of the internal storage units 109a and 109b, the external storage unit 109c, and the manual feed unit 109d to the conveying path. Registration rollers 110 are provided on the conveying path. The fed sheet is conveyed to the registration rollers 110.

[0017] Registration rollers 110 correct any skew of the sheet and transport the sheet onto transfer belt 111 at the appropriate timing so that the toner images on each photoconductor 102 are transferred to the predetermined positions on the sheet. As described above, the toner images are transferred onto the sheet while it is transported on transfer belt 111. Fixing unit 104 fixes the toner images onto the sheet by applying heat and pressure to the sheet onto which the toner images have been transferred. After the toner images have been fixed, the sheet is discharged outside image forming apparatus 1 by discharge rollers 112.

[0018] The image forming apparatus 1 includes an image controller (described later) that performs various image processing such as color space conversion, filtering, magnification, resolution conversion, and quantization on the scanned image data and print image data. The image controller processes the scanned image data and print image data to generate print image data (hereinafter, sometimes simply referred to as "image data") for image formation by the image creating unit 103. The image controller includes an image processing module that performs the various image processing described above. The image controller also includes a PG module that generates image data representing an adjustment image used for various adjustments of the image forming apparatus 1, and a PG module that generates image data representing an adjustment image for individually controlling each light-emitting element in the exposure head 106. The PG module is a pattern generator module.

[0019] Although a configuration has been described here in which a toner image is directly transferred from each photoconductor 102 to a sheet on the transfer belt 111, the toner image may also be indirectly transferred from each photoconductor 102 to a sheet via an intermediate transfer body. Also, although an example in which a color image is formed using toner of multiple colors has been described here, the technology according to this embodiment can also be applied to an image forming apparatus that forms a monochrome image using toner of a single color.

[0020] (Exposure head) 2 is an explanatory diagram of the photoconductor 102 and the exposure head 106. Fig. 2(a) is a perspective view of the photoconductor 102 and the exposure head 106. Fig. 2(b) is an explanatory diagram of the exposure position. The exposure head 106 has a light emitting element array 201 having a plurality of light emitting elements, a printed circuit board 202 on which the light emitting element array 201 is mounted, a rod lens array 203, and a housing 204 that holds the rod lens array 203 and the printed circuit board 202.

[0021] As described above, the photoconductor 102 has a drum shape. The exposure head 106 is disposed so that its longitudinal direction is parallel to the drum axis direction D1 of the photoconductor 102 and the mounting surface of the rod lens array 203 faces the surface of the photoconductor 102. While the photoconductor 102 rotates in the circumferential direction D2, the light-emitting element array 201 (light-emitting elements) of the exposure head 106 emits light, and the rod lens array 203 focuses the light on the surface of the photoconductor 102. The surface of the photoconductor 102 is uniformly charged by the charger 107, and the potential at the position where the light is focused is displaced. The position where the potential is displaced becomes an electrostatic latent image.

[0022] The light emitting element array 201 has a plurality of light emitting elements arranged in a plane. The light emitting elements may be, for example, organic electroluminescence (EL) elements or light emitting diodes (LEDs). The drum axial direction D1 is the main scanning direction, and the circumferential direction D2 is the sub-scanning direction.

[0023] FIG. 3 is an explanatory diagram of the printed circuit board 202. A connector 305 and a light emitting element array 201 are mounted on different surfaces of the printed circuit board 202. FIG. 3(a) shows the surface of the printed circuit board 202 on which the connector 305 is mounted. FIG. 3(b) shows the surface of the printed circuit board 202 on which the light emitting element array 201 is mounted. The light emitting element array 201 includes a plurality of light emitting chips 400, each having a plurality of light emitting elements. In this embodiment, there are 20 light emitting chips 400 (light emitting chips 400-1 to 400-20). The light emitting chips 400-1 to 400-20 are arranged in a staggered pattern in the main scanning direction.

[0024] 3(b), the area occupied by all of the 20 light-emitting chips 400-1 to 400-20 in the main scanning direction is wider than the area occupied by the maximum width W0 of the image represented by the print image data. Therefore, some of the light-emitting elements located at both ends in the main scanning direction do not need to be used to expose the photosensitive element 102 unless image misalignment is detected. Each light-emitting chip 400 on the printed circuit board 202 is connected to an image controller (described later) via a connector 305.

[0025] For ease of explanation, the side with the smaller branch number of the light-emitting chips 400-1 to 400-20 arranged in the main scanning direction may be referred to as the "left" and the side with the larger branch number as the "right." For example, the light-emitting chip 400-1 is the leftmost light-emitting chip 400, and the light-emitting chip 400-20 is the rightmost light-emitting chip. In FIG. 4, the two rightmost light-emitting chips 400-n and 400-n+1 are illustrated.

[0026] FIG. 4 is an explanatory diagram of the light-emitting chip 400. The light-emitting element array 201 of this embodiment includes a plurality of light-emitting elements arranged in N columns in the main scanning direction and M rows in the sub-scanning direction as a whole. M and N are integers equal to or greater than 2. The number J (J=N / 20) of light-emitting elements 602 arranged in each row (main scanning direction) of one light-emitting chip 400 is, for example, 748 (J=748). The number M of light-emitting elements 602 arranged in each column (sub-scanning direction) of one light-emitting chip 400 is, for example, 4 (M=4). That is, in this example of this embodiment, the light-emitting chip 400 has 748 light-emitting elements 602 in the main scanning direction and 4 light-emitting elements in the sub-scanning direction, for a total of 2992 (=748×4) light-emitting elements 602.

[0027] The distance PC between the center points of adjacent light-emitting elements 602 in the sub-scanning direction is approximately 21.16 μm when the resolution is 1200 dpi, for example. The distance between the center points of adjacent light-emitting elements 602 in the main scanning direction is also approximately 21.16 μm, for example. In this case, the length of the 748 light-emitting elements 602 in the main scanning direction is approximately 15.8 mm.

[0028] 4 shows an example in which the light emitting elements 602 of each light emitting chip 400 are arranged in a complete grid pattern for convenience, but in reality, M (M=4) light emitting elements 602 in each row are arranged in a staircase pattern, as will be described later.

[0029] 5 is a plan view of the light-emitting chip 400. A plurality of light-emitting elements 602 are formed on a light-emitting substrate 402, which is, for example, a silicon substrate. A circuit unit 406 for driving the plurality of light-emitting elements 602 is mounted on the light-emitting substrate 402. The light-emitting substrate 402 is provided with pads 408-1 to 408-9 to which signal lines for communicating with an image controller, power lines for connecting to a power source, and ground lines for grounding are connected. The signal lines, power lines, and ground lines are wires made of, for example, Au.

[0030] Figure 6 is a cross-sectional view taken along the line AA in Figure 5. A plurality of lower electrodes 504 are formed on the light-emitting substrate 402. A gap of length d is provided between two adjacent lower electrodes 504. A light-emitting layer 506 is provided on the lower electrodes 504, and an upper electrode 508 is provided on the light-emitting layer 506. The upper electrode 508 is a common electrode for the plurality of lower electrodes 504.

[0031] When a potential difference occurs between the lower electrode 504 and the upper electrode 508, a current flows from the lower electrode 504 to the upper electrode 508, causing the light-emitting layer 506 to emit light. Therefore, one lower electrode 504 and a partial region of the light-emitting layer 506 and upper electrode 508 corresponding to that lower electrode 504 constitute one light-emitting element 602. In this way, a plurality of light-emitting elements 602 are formed on the light-emitting substrate 402.

[0032] The light-emitting layer 506 may be made of, for example, an organic EL film. The upper electrode 508 is made of, for example, a transparent electrode such as indium tin oxide (ITO) so as to transmit the wavelength of light (emission wavelength) emitted from the light-emitting layer 506. In this embodiment, the entire upper electrode 508 transmits the emission wavelength of the light-emitting layer 506, but it is not necessary for the entire upper electrode 508 to transmit the emission wavelength. Specifically, it is sufficient that a partial region through which light from each light-emitting element 602 passes transmits the emission wavelength.

[0033] Although the light-emitting layer 506 of the present embodiment is formed as a single continuous light-emitting layer 506, a plurality of light-emitting layers 506 each having a width equal to the width W of the lower electrode 504 may be formed on the lower electrode 504, respectively. Furthermore, a first plurality of lower electrodes 504 of the lower electrodes 504 of each light-emitting chip 400 may be covered with a first light-emitting layer 506, and a second plurality of lower electrodes 504 may be covered with a second light-emitting layer 506. Furthermore, a first upper electrode 508 may be commonly formed corresponding to the first plurality of lower electrodes 504 of the lower electrodes 504 of each light-emitting chip 400, and a second upper electrode 508 may be commonly formed corresponding to the second plurality of lower electrodes 504. Even in such a configuration, one lower electrode 504 and the region of the light-emitting layer 506 and upper electrode 508 corresponding to the lower electrode 504 constitute one light-emitting element 602.

[0034] (Image controller of exposure head 106) 7 is a configuration diagram of an image controller that also controls the turning on and off of the light-emitting chip 400. The image controller 700 can communicate with the printed circuit board 202 via multiple signal lines (wires). The image controller 700 has a CPU (Central Processing Unit) 701, a clock generation unit 702, an image data processing unit 703, a register access unit 704, a light emission control unit 705, and a synchronization signal generation unit 706.

[0035] The light-emitting control unit 705, together with the exposure head 106, constitutes an exposure device. The light-emitting control unit 705 terminates the signal line between it and the printed circuit board 202. The n-th light-emitting chip 400-n on the printed circuit board 202 is connected to the light-emitting control unit 705 by a signal line DATAn and a signal line WRITEn. The signal line DATAn transmits print image data from the image controller 700 to the light-emitting chip 400-n. The signal line WRITEn is a signal line that allows the image controller 700 to write control data to a register of the light-emitting chip 400-n.

[0036] One signal line CLK, one signal line SYNC, and one signal line EN are further provided between the light-emitting control unit 705 and each light-emitting chip 400. The signal line CLK transmits a clock signal for data transmission via the signal lines DATAn and WRITEn. The clock generation unit 702 generates a reference clock signal and transmits it to each unit of the image controller 700. The light-emitting control unit 705 transmits a clock signal generated based on the reference clock signal obtained from the clock generation unit 702 to each light-emitting chip 400 via the signal line CLK.

[0037] The synchronization signal generation unit 706 generates and outputs a synchronization signal synchronized with the reference clock signal obtained from the clock generation unit 702. The synchronization signal is a reference signal for the output timing of print image data from the output unit in the image data processing unit 703, and serves as a reference signal for the timing of sending print image data from the light emission control unit 705 to each light-emitting chip 400. The synchronization signal generation unit 706 outputs print image data from the light emission control unit 705 while coordinating with the image formation operation by the image creation unit 103, and generates the synchronization signal based on an image formation operation start signal (referred to as a "TOP signal" in this embodiment) from the image creation unit 103.

[0038] The CPU 701 controls the overall operation of the image forming apparatus 1. The image data processing unit 703 performs predetermined image processing on read image data and print image data acquired from the reading unit 100 or an external device. By performing image processing, the image data processing unit 703 generates binary image data (print image data) for controlling the light emission of the light emitting element 602 of the light emitting chip 400 on the printed circuit board 202.

[0039] The image processing performed by the image data processing unit 703 includes, for example, raster conversion, tone correction, color conversion, and halftone processing. The image data processing unit 703 transmits the generated binary image data (print image data) to the light emission control unit 705. The register access unit 704 receives control data to be written to the register in each light-emitting chip 400 from the CPU 701 and transmits it to the light emission control unit 705.

[0040] The image forming apparatus 1 has an exposure head 106 in each of the image forming units 101a to 101d. That is, in this embodiment, four printed circuit boards 202 are provided. The image controller 700 is connected to these four printed circuit boards 202, and controls the lighting of the multiple light-emitting elements 602 mounted on each of the four printed circuit boards 202.

[0041] FIG. 8 is a timing chart when control data is written to the register of each light-emitting chip 400. FIG. 8 shows the transition of the signal level of each signal line when control data is written to the register of the light-emitting chip 400. An enable signal, which is at a high level during communication and indicates that communication is in progress, is transmitted to the signal line EN. The light-emitting control unit 705 transmits a start bit to the signal line WRITEn in synchronization with the rising edge of the enable signal. Next, the light-emitting control unit 705 transmits a write identification bit, which indicates a write operation, to the signal line WRITEn, and then transmits the address (4 bits in this case) of the register to which the control data is to be written and the control data (8 bits in this case). When writing to the register, the light-emitting control unit 705 sets the frequency of the clock signal transmitted on the signal line CLK to, for example, 3 MHz.

[0042] 9 is a timing chart illustrating the transition of the signal level of each signal line when print image data is transmitted to each light-emitting chip 400. A periodic line synchronization signal indicating the exposure timing of each line on the photosensitive element 102 is transmitted to the signal line SYNC. If the peripheral speed of the photosensitive element 102 is 200 [mm / s] and the peripheral resolution is 1200 [dpi] (approximately 21.16 [μm]), the line synchronization signal is output at a period of approximately 105.8 [μs].

[0043] The light emission control unit 705 transmits print image data via signal lines DATA1 to DATA20 in synchronization with the rising edge of the line synchronization signal. Since each light emitting chip 400 in this embodiment has 2992 light emitting elements 602, it is necessary to transmit print image data to each light emitting chip 400 within a cycle of approximately 105.8 [μs] to control the light emission (illumination) of each of the 2992 light emitting elements 602. Therefore, in this embodiment, as shown in FIG. 9, when transmitting print image data, the light emission control unit 705 sets the frequency of the clock signal transmitted via the signal line CLK to 30 [MHz].

[0044] 10 is a detailed functional configuration diagram of one (n-th light-emitting chip 400-n) of the light-emitting chip 400. The circuit unit 406 includes a register 1102, a transfer unit 1103, latch units 1004-001 to 1004-748, and a current driver 1104.

[0045] As described in FIG. 5, the light-emitting chip 400 has nine pads 408-1 to 408-9. A power supply voltage VCC is applied to the pads 408-1 and 408-2 via a power supply line. The power supply voltage VCC is applied to each part of the circuit unit 406 of the light-emitting chip 400 via the pads 408-1 and 408-2. The pads 408-3 and 408-4 are grounded via a ground line. Each part of the circuit unit 406 and the upper electrode 508 are grounded via the pads 408-3 and 408-4.

[0046] The pad 408-5 is connected to a signal line CLK. The signal line CLK is connected to the transfer unit 1103, the register 1102, and the latch units 1004-001 to 1004-748 via the pad 408-5. The pad 408-6 is connected to a signal line SYNC. The pad 408-7 is connected to a signal line DATAn. The signal lines SYNC and DATAn are connected to the transfer unit 1103 via the pads 408-6 and 408-7. The pad 408-8 is connected to a signal line EN. The pad 408-9 is connected to a signal line WRITEn. The signal lines EN and WRITEn are connected to the register 1102 via the pads 408-8 and 408-9. The register 1102 stores control data indicating, for example, the light emission intensity of the light emitting element 602.

[0047] The transfer unit 1103 starts with a line synchronization signal obtained from the signal line SYNC, and synchronizes with a clock signal obtained from the signal line CLK to obtain print image data from the signal line DATAn, the print image data including a series of pixel values ​​each indicating the lighting or extinguishing of one light-emitting element 602. The transfer unit 1103 performs serial-to-parallel conversion on the series of pixel values ​​serially obtained from the signal line DATAn in units of M (for example, M=4).

[0048] For example, the transfer unit 1103 has four cascade-connected D flip-flops. The transfer unit 1103 parallelizes pixel values ​​DATA-1, DATA-2, DATA-3, and DATA-4 input over a period of four clocks and sequentially transmits them to the latch units 1004-001 to 1004-748. The transfer unit 1103 also has four D flip-flops for delaying the line synchronization signal. The transfer unit 1103 outputs a first latch signal to the latch unit 1004-001 via the signal line LAT1 with a delay of four clocks from the input of the line synchronization signal. The first latch signal is, for example, a signal obtained by delaying the line synchronization signal by four clocks.

[0049] The kth latch unit 1004-k (k is an integer from 1 to 748) latches four pixel values ​​DATA-1, DATA-2, DATA-3, and DATA-4 input from the transfer unit 1103 simultaneously with the input of the kth latch signal. Except for the last-stage latch unit 1004-748, the kth latch unit 1004-k delays the kth latch signal by four clocks and outputs the (k+1)th latch signal to the latch unit 1004-(k+1) via the signal line LAT(k+1). The kth latch unit 1004-k continues to output drive signals based on the four latched pixel values ​​to the current drive unit 1104 during the signal period of the kth latch signal.

[0050] For example, there is a delay of four clocks between the timing at which the first latch signal is input to latch unit 1004-001 and the timing at which the second latch signal is input to latch unit 1004-002. Therefore, latch unit 1004-001 outputs a drive signal based on the first to fourth pixel values ​​to current driver 1104, while latch unit 1004-002 outputs a drive signal based on the fifth to eighth pixel values ​​to current driver 1104.

[0051] Generally speaking, the latch unit 1004-k outputs drive signals based on the (4k-3)th to (4k)th pixel values ​​to the current driver 1104. Therefore, in Fig. 10, 748 latch units 1004-001 to 1004-748 output 2992 drive signals in approximately parallel to the current driver 1104 for controlling the driving of 2992 (=748 × 4) light-emitting elements 602. Each drive signal is a binary signal indicating a high or low level.

[0052] The current driver 1104 has 2992 light-emitting drive circuits corresponding to the 2992 light-emitting elements 602, each including a partial region of the light-emitting layer 506. Each light-emitting drive circuit applies a drive voltage corresponding to the light-emitting intensity indicated by the control data in the register 1102 to the light-emitting layer 506 of the corresponding light-emitting element 602 while the drive signal is at a high level, which means that the light-emitting element is on (lit). This causes a current to flow through the light-emitting layer 506, causing the light-emitting element 602 to emit light. The control data may indicate one individual light-emitting intensity for each light-emitting element 602, one light-emitting intensity for each group of light-emitting elements 602, or one light-emitting intensity common to all light-emitting elements 602.

[0053] (Multiple exposure control) 4 shows an example in which the light-emitting elements 602 of each light-emitting chip 400 are arranged in a grid pattern, but in reality, the M light-emitting elements 602 in each row are arranged in a stepped pattern at a constant pitch. Fig. 11 is an explanatory diagram of multiple exposure using the light-emitting elements 602 arranged in a stepped pattern. Fig. 11 partially illustrates an example of the arrangement of the light-emitting elements 602 of the light-emitting chip 400-1 when M=4.

[0054] Rj_m (j = {0, 1, ..., 747}, m = {0, 1, 2, 3}) indicates the light-emitting element 602 that is in the jth column from the left in the main scanning direction and the mth row from the top in the sub-scanning direction. The pitch PC of the light-emitting elements in the sub-scanning direction is determined by the size of the light-emitting elements 602 and is, for example, approximately 21.16 μm as described above. The interval in the main scanning direction between two adjacent light-emitting elements of the M light-emitting elements in each column, i.e., the pitch PA of the light-emitting elements 602 in the main scanning direction, is, for example, approximately 5 μm in the case of a resolution of 4800 dpi.

[0055] By arranging the four light-emitting elements 602 in each column in a stepped manner in this way, any two adjacent light-emitting elements 602 of the four light-emitting elements 602 have areas that partially overlap in the main scanning direction. While the photoconductor 102 is rotating, the four light-emitting elements 602 in the column corresponding to each pixel position of the print image data sequentially emit light, forming spots corresponding to each pixel position on the surface of the photoconductor 102.

[0056] In the example of FIG. 11, when the pixel value at the left end of the ith line of the print image data indicates lighting (ON), light-emitting elements R0_0, R0_1, R0_2, and R0_3 sequentially emit light at the timings at which they respectively face line Li on the surface of the photoconductor 102. As a result, the spot area at the left end of line Li is multiply exposed to form spot SP0. Similarly, when the jth pixel value from the left of the ith line of the print image data indicates lighting (ON), light-emitting elements Rj_0, Rj_1, Rj_2, and Rj_3 sequentially emit light at the timings at which they respectively face line Li on the surface of the photoconductor 102. As a result, the jth spot area from the left of line Li is multiply exposed to form a corresponding spot SPj.

[0057] In this manner, in this embodiment, the light-emitting elements in two rows adjacent to each other in the fast scanning direction occupy areas that partially overlap in the fast scanning direction. Similarly, of the two light-emitting chips 400 adjacent to each other in the fast scanning direction, the light-emitting elements in the rightmost row of the left light-emitting chip 400 and the light-emitting elements in the leftmost row of the right light-emitting chip 400 also occupy areas that partially overlap in the fast scanning direction (see FIG. 3(b)).

[0058] The pitch PA of the light-emitting elements 602 in the main scanning direction is constant (approximately 5 μm) across all 20 light-emitting chips 400. When the four light-emitting elements in each row of these light-emitting chips 400 emit light sequentially at appropriate timing, a smooth line of an electrostatic latent image is formed on the surface of the photoconductor 102, consisting of a series of spots that partially overlap each other at regular intervals. When such lines are formed continuously in the sub-scanning direction, a two-dimensional electrostatic latent image is generated on the surface of the photoconductor 102.

[0059] Figures 12, 13, and 14 are explanatory diagrams of output control by the light emission control unit 705 based on print image data. Figures 12(a), 12(b), 13(a), and 13(b) each show a case where the line synchronization signal shown in Figure 9 is received four times, starting from the first line of print image data IM1. Figure 14 shows a case where a line synchronization signal for outputting the final line of print image data IM1 is received.

[0060] 12(a), 12(b), 13(a), and 14, the order in which the light emission control unit 705 reads out the print image data IM1 is indicated by dashed lines. Rj-m within the dashed lines indicates the print image data output to the light emitting elements shown in FIG. 11. The order in which the print image data is output is as shown in the timing chart in FIG. 9. The light emission control unit 705 sequentially outputs the print image data in the order R0-0 → R0-1 → R0-2 → R0-3 → R1-0 → R1-1.

[0061] The right sides of Figures 12(a), 12(b), 13(a), and 14 show a printout printed by the light emission control unit 705 sending the first four lines of the image of the print image data IM1 to the exposure head 106, where the printout is printed as a valid image. The shaded areas show the state where the image corresponding to the print image data IM1 is actually printed. The right sides of Figures 12(a), 12(b), 13(a), and 14 show that one line of image is formed by the light emission control unit 705 receiving the line synchronization signal four times.

[0062] 12(a), 12(b), 13(a), and 14, there are portions where there is no print image data IM1 to be output to the light-emitting element Rj_m. When there is no print image data IM1 corresponding to the image to be output, the light-emitting control unit 705 outputs "0" indicating "turn off."

[0063] (Image Controller) The image forming apparatus 1 of this embodiment described above uses binary print image data to control the on / off of each light-emitting element. In this embodiment, a case where an image with a resolution of 4800 dpi in the main scanning direction and 1200 dpi in the sub-scanning direction is formed will be described. Figure 15 shows a detailed configuration diagram of the image controller 700 for generating the binary print image data.

[0064] The image controller 700 acquires the read image data generated by the reading unit 100 and generates print image data through image processing by various image processing modules. Based on the print image data, the image controller 700 outputs a signal to the printed circuit board 202 in the exposure head 106 to control the on / off of light-emitting elements. Note that the image controller 700 may also generate print image data by similarly processing print image data acquired from an external device, and output a signal to control the on / off of light-emitting elements.

[0065] The image controller 700 executes internal processing operations in synchronization with a clock signal generated by a clock generation unit 702. For each image processing module in the image data processing unit 703, a synchronization signal input from a synchronization signal generation unit 706 serves as a reference signal for the timing of data input / output to / from each image processing module. The synchronization signal output from the synchronization signal generation unit 706 is also used as a timing signal when the light emission control unit 705 transmits print image data to each light-emitting chip 400. A register setting unit 1317 in the image data processing unit 703 is connected to the CPU 701 and each image processing module and PG module described below. The register setting unit 1317 stores and outputs settings of each image processing module and PG module in response to instructions from the CPU 701.

[0066] The image processing modules included in the image data processing unit 703 include a page data storage unit 1301, an MTF (Modulation Transfer Function) correction unit 1303, and a scanner color correction unit 1304. The image processing modules included in the image data processing unit 703 also include a color space conversion unit 1305, a scaling processing unit 1307, a printer color correction unit 1308, a quantization processing unit 1309, and an exposure conversion unit 1311. The image processing modules included in the image data processing unit 703 also include a left edge skew correction unit 1312, a shading processing unit 1313, a resolution conversion unit 1314, and an image position control unit 1315. The PG modules included in the image data processing unit 703 include an RGB-PG unit 1302, a CMYK-PG unit 1306, a binary data PG unit 1310, and a light emission control PG unit 1316.

[0067] The page data storage unit 1301 acquires read image data from the reading unit 100. The page data storage unit 1301 has a memory capacity for saving read image data for one page. For this purpose, the page data storage unit 1301 stores the read image data for one page acquired from the reading unit 100. The MTF correction unit 1303 performs filtering processing on the read image data stored in the page data storage unit 1301 in accordance with the characteristics of the reading sensor of the reading unit 100. This makes the resolution of each individual reading sensor of the reading unit 100 uniform. Note that the read image data generated by the reading sensor of the reading unit 100 is RGB image data including R (red), G (green), and B (blue) color components.

[0068] The scanner color correction unit 1304 performs processing such as table conversion and arithmetic processing to correct the color of the read image data (RGB image data) output from the MTF correction unit 1303. Through such correction processing, the scanner color correction unit 1304 adjusts the characteristics of the reading sensor of the reading unit 100, which vary from one unit to another, to common color and image density for subsequent processing. The color space conversion unit 1305 performs processing such as table conversion and arithmetic processing on the RGB image data processed by the scanner color correction unit 1304, converting the RGB color space into the CMYK color space, which is the color space for print output.

[0069] The scaling processor 1307 performs scaling processing on the read image data (CMYK image data) converted to the CMYK color space by the color space converter 1305, to match the scaling factor at the time of printout. For example, if the document read by the reading unit 100 is A4 size and the sheet at the time of printout is A3 size, the scaling processor 1307 performs scaling processing to obtain an image 1.41 times larger in size through interpolation processing in both the main scanning direction and the sub-scanning direction. Also, if the document read by the reading unit 100 is A4 size and the sheet at the time of printout is A5 size, the scaling processor 1307 performs scaling processing to obtain an image 0.71 times larger in size through thinning processing in both the main scanning direction and the sub-scanning direction.

[0070] In this embodiment, the resolution in the main scanning direction during print output is 4800 dpi and the resolution in the sub-scanning direction is 1200 dpi. However, the scanned image data generated by the scanning unit 100 has a resolution in the main scanning direction of 600 dpi to 2400 dpi and a resolution in the sub-scanning direction of 600 dpi. The scaling processor 1307 processes the scanned image data at an image size based on the resolution. This reduces the load on subsequent processes in this module and on storing the image data in memory during processing. To achieve this, the scaling processor 1307 performs interpolation in the main scanning direction to supplement the number of pixels. In this embodiment, the resolution conversion unit 1314 converts the image data to the resolution required for image formation by the image forming unit 103.

[0071] A printer color correction unit 1308 performs color correction by performing table conversion, arithmetic processing, etc. on the CMYK image data output from the scaling processing unit 1307. Through such correction processing, the printer color correction unit 1308 matches the print density and color characteristics in the image forming unit 103, which differ for each individual, to a consistent color for the print output.

[0072] The quantization processing unit 1309 performs quantization processing in accordance with the output of the print engine of the image forming unit 103. In this embodiment, exposure control is performed using a binary signal that indicates the on / off state of the light emitting element 602 in the image forming unit 103. To achieve this, the quantization processing unit 1309 performs binarization processing using dither processing, error diffusion processing, or the like on each piece of multi-valued data of the color-corrected CMYK image data. The quantization processing unit 1309 generates binary image data through binarization processing.

[0073] In order to control the reproducibility of outlines and thin lines of characters, etc., the exposure conversion unit 1311 performs filter processing on the binary image data generated by the quantization processing unit 1309, converts the data into multi-value data, and performs correction using table conversion, etc. After that, the exposure conversion unit 1311 returns the corrected data to binary image data by performing quantization processing such as error diffusion again.

[0074] The left edge skew correction unit 1312 shifts the binary image data in the main scanning direction, taking into account the position in the sub-scanning direction, according to the characteristics of the skew amount when the sheet is conveyed by the conveyance unit 105. The shading processing unit 1313 corrects the binary image data to equalize the individual light intensity states of each device, such as unevenness in the lens period caused by the arrangement and inclination of the rod lens array 203 in the exposure head 106, and unevenness in the light intensity. The left edge skew correction unit 1312 and the shading processing unit 1313 enable image formation according to the characteristics of the sheet skew and the exposure head 106.

[0075] The resolution conversion unit 1314 performs processing to adjust the resolution of the binary image data output from the shading processing unit 1313 to the resolution at the time of printout. In this embodiment, the resolution of the read image data generated by the reading unit 100 is 600 [dpi] in the main scanning direction and 600 [dpi] in the sub-scanning direction. The read image data is converted by the magnification processing unit 1307 to a resolution of 2400 [dpi] in the main scanning direction and 600 [dpi] in the sub-scanning direction. If the resolution at the time of printout is 4800 [dpi] in the main scanning direction and 1200 [dpi] in the sub-scanning direction, the resolution conversion unit 1314 doubles the resolution in the main scanning direction and the sub-scanning direction by simple interpolation. The image position control unit 1315 performs processing to allocate the binary image data after resolution conversion to one of the light-emitting chips 400-1 to 400-20 to which the binary image data should be sent.

[0076] The image data processing unit 703 performs processing using the various image processing modules described above, and converts the read image data, which is RGB multi-value data acquired from the reading unit 100, into print image data, which is CMYK binary data. This conversion process converts the resolution of the read image data, which is 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction, into the resolution of the print image data, which is 4800 dpi in the main scanning direction and 1200 dpi in the sub-scanning direction.

[0077] The RGB-PG unit 1302 is a pattern generator that generates output data similar to the read image data acquired from the reading unit 100. In this embodiment, the RGB-PG unit 1302 generates and outputs output data that is RGB multi-value data with a resolution of 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction. This output data is used for debugging each image processing module connected downstream, checking its operation, and generating image data for generating an adjustment image for color adjustment in the reading unit 100 or the image creating unit 103.

[0078] The CMYK-PG unit 1306 is a pattern generator that generates output data similar to the CMYK image data output from the color space conversion unit 1305. In this embodiment, the CMYK-PG unit 1306 generates and outputs output data that is CMYK multi-value data with a resolution of 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction. This output data is used for debugging each image processing module connected downstream, checking operation, generating image data for generating an adjustment image for color adjustment in the reading unit 100 or the image creating unit 103, etc.

[0079] The binary data PG unit 1310 is a pattern generator that generates output data similar to the binary image data output from the quantization processing unit 1309. In this embodiment, the binary data PG unit 1310 generates and outputs output data that is CMYK binary data with a resolution of 2400 dpi in the main scanning direction and 600 dpi in the sub-scanning direction. This output data is used for debugging each image processing module in the subsequent stage, checking operation, and generating image data for generating an adjustment image for color adjustment in the reading unit 100 and the imaging unit 103.

[0080] The light emission control PG unit 1316 is a pattern generator that generates output data for individually controlling the on / off of each light emitting element in the exposure head 106. In this embodiment, the light emission control PG unit 1316 generates and outputs output data consisting of CMYK binary data with a resolution of 4800 [dpi] in the main scanning direction and 1200 [dpi] in the sub-scanning direction.

[0081] 16 is a configuration diagram of the light emission control unit 705 in the image controller 700. The light emission control unit 705 executes the processing operations of each internal unit in synchronization with the clock signal input from the clock generation unit 702. Each unit in the light emission control unit 705 uses the synchronization signal input from the synchronization signal generation unit 706 as the reference for the input / output timing of image data. The light emission control unit 705 also uses the synchronization signal as a timing signal for transmitting image data to each light emitting chip 400 on the printed circuit board 202. The light emission control unit 705 includes an image data storage unit 1401, an image data reading unit 1402, an image data output unit 1403, and a register access signal output unit 1404.

[0082] The image data storage unit 1401 is a memory having a capacity for storing two lines of binary image data. The image data storage unit 1401 stores binary image data acquired from the image data processing unit 703. The image data reading unit 1402, under the control of the CPU 701, reads the binary image data from the image data storage unit 1401 and transmits it to the image data output unit 1403.

[0083] The image data output unit 1403 outputs a clock, a line synchronization signal, and a DATAn signal (n is 1 to 20) based on binary image data to each light-emitting chip 400 on the printed circuit board 202. The image data output unit 1403 has n buffer memories (BAFF-DATAn) for storing binary image data to be output to each light-emitting chip 400. The image data output unit 1403 sorts the binary image data acquired from the image data processing unit 703 according to the destination of each light-emitting chip 400 and stores the data in the buffer memories.

[0084] The register access signal output unit 1404 is a signal conversion unit that outputs a signal conforming to a format for writing data to a specific address of the register 1102 in each light-emitting chip 400, based on the signal acquired from the register access unit 704. The register access signal output unit 1404 receives a 5-bit CHIPE signal, a 4-bit address signal, and an 8-bit data signal, which indicate which chip of the light-emitting chip 400-n the address and data are for, from the register access unit 704. For example, when the CHIPE signal is "1", it indicates that the address and data are for the light-emitting chip 400-1, and when it is "2", it indicates that the address and data are for the light-emitting chip 400-2.

[0085] The register access signal output unit 1404 receives a 5-bit CHIPE signal, a 4-bit address signal, and an 8-bit data signal, and converts each piece of data into an output signal for writing control data to the register 1102 of the light-emitting chip 400.

[0086] The light emission control unit 705 configured as described above switches between binary image data and register access, and outputs various signals to the printed circuit board 202. This controls the on / off of light-emitting elements in the light-emitting chip 400 on the printed circuit board 202, and processing by the image forming unit 103 is performed.

[0087] 17 illustrates a timing chart of transmission of binary image data to each light-emitting chip 400. A periodic line synchronization signal indicating the exposure timing of one line of an image on the photosensitive element 102 is transmitted to the signal line SYNC. In this embodiment, the peripheral speed of the photosensitive element 102 is set to 200 [mm / s], and the resolution in the sub-scanning direction is set to 1200 [dpi] (approximately 21.16 [μm]), and the line synchronization signal is transmitted at a period of approximately 105.8 [μs].

[0088] The light-emission control unit 705 transmits binary image data to signal lines DATAn (n: 1 to 20) in synchronization with the rising edge of the line synchronization signal. In this embodiment, each light-emitting chip 400 has 2992 light-emitting elements 602. The light-emission control unit 705 needs to transmit binary image data indicating the on / off state of each of the total 2992 light-emitting elements 602 to each light-emitting chip 400 within a period of approximately 105.8 [μs]. For this reason, in this embodiment, the light-emission control unit 705 sets the frequency of the clock signal transmitted to the signal line CLK to 30 [MHz] when transmitting image data.

[0089] 17, data transferred between line synchronization signals for the light-emitting chip 400-1 are collectively referred to as L1-DATA1, L2-DATA1, L3-DATA1, etc. Data transferred between line synchronization signals for the light-emitting chip 400-2 are collectively referred to as L1-DATA2, L2-DATA2, L3-DATA2, etc. Similarly, data transferred between line synchronization signals for the light-emitting chip 400-20 are collectively referred to as L1-DATA20, L2-DATA20, L3-DATA20, etc.

[0090] 18 is a timing chart illustrating an example of the operation of the light emission control unit 705. FIG. 18 shows the timing from data input from the image data processing unit 703 to the light emission control unit 705 to data output from the image data output unit 1403.

[0091] The line synchronization signal (SYNC) is a timing signal used when transmitting image data DATAn from the light-emitting control unit 705 to each light-emitting chip 400 on the printed circuit board 202. The line synchronization signal becomes a high-level signal with a width equivalent to one cycle of the clock signal at the beginning of each line of image data.

[0092] The BDATA signal is data output from the image data processing unit 703. As described in FIG. 17, the light emission control unit 705 captures the BDATA signal between the first and second line synchronization signals. The light emission control unit 705 captures data L1-DATA1 to L1-DATA20 to be transferred to the printed circuit board 202 between the first and second line synchronization signals. The light emission control unit 705 captures L2-DATA1 to L2-DATA20 between the second and third line synchronization signals. The light emission control unit 705 captures L3-DATA1 to L2-DATA20 between the third and fourth line synchronization signals. The image data processing unit 703 sequentially outputs such data.

[0093] MEM1 and MEM2 indicate data stored in the image data storage unit 1401. The image data storage unit 1401 is configured with a memory such as an SRAM (Static Random Access Memory). The memory area of ​​the image data storage unit 1401 is divided into a first memory area and a second memory area, each of which has a capacity sufficient to store data acquired between line synchronization signals. The data stored in the image data storage unit 1401 is binary image data.

[0094] In this embodiment, toner adheres to the exposed portion of the photoconductor 102 to form a toner image, which is then transferred and fixed to a sheet. When the binary image data quantized by the image data processing unit 703 is at a high level, the light-emitting element is turned on so that toner is printed, and when the binary image data is at a low level, the light-emitting element is turned off so that toner is not printed.

[0095] The light emission control unit 705 acquires data based on the line synchronization signal. Data input to the image data storage unit 1401 at the first rising edge of the line synchronization signal is stored in the first memory area. Data input to the image data storage unit 1401 at the second rising edge of the line synchronization signal is stored in the second memory area. Data input to the image data storage unit 1401 at the third rising edge of the line synchronization signal overwrites the first memory area. Data input to the image data storage unit 1401 at the fourth rising edge of the line synchronization signal is overwritten in the second memory area. In this way, image data acquired in synchronization with odd-numbered line synchronization signals is stored in the first memory area while being overwritten, and image data acquired in synchronization with even-numbered line synchronization signals is stored in the second memory area while being overwritten.

[0096] The CDATA signal is image data output from the image data readout unit 1402. The image data readout unit 1402 outputs MDATA, which is image data, from the image data storage unit 1401 in synchronization with the clock signal based on a control signal and a line synchronization signal from the CPU 701. The output of image data from the image data storage unit 1401 begins with the line synchronization signal. At the third line synchronization signal, the image data stored initially is output from the first memory area of ​​the image data storage unit 1401, passes through the image data readout unit 1402, and is output from the light-emission control unit 705. At the fourth line synchronization signal, the image data stored second time is output from the second memory area of ​​the image data storage unit 1401, passes through the image data readout unit 1402, and is output from the light-emission control unit 705. In this way, image data is output sequentially from the first memory area and the second memory area of ​​the image data storage unit 1401, triggered by each line synchronization signal.

[0097] BAFF-DATA1 to BAFF-DATA20 are data stored in each buffer memory in the image data output unit 1403. The image data read out by the image data reading unit 1402 is sorted and stored in buffer memories for output signals of DATA1 to DATA20 corresponding to each light-emitting chip 400 according to the exposure position. DATA1 to DATA20 are output from the image data output unit 1403. When a line synchronization signal indicating the beginning of each line rises, image data is output from the buffer memory BAFF-DATAn in the image data output unit 1403 to each light-emitting chip 400 in synchronization with the clock signal. In this embodiment, as shown in FIG. 18 , the first captured image data is output to each light-emitting chip 400 on the printed circuit board 202 at the timing of the third line synchronization signal.

[0098] 17 and 18, when an exposure head 106 in which the light-emitting chips 400 are arranged in a staggered pattern as shown in FIG. 3(b) is used, the exposure lines on the photosensitive member 102 may be misaligned if all the light-emitting chips 400 are made to emit light simultaneously. This misalignment occurs due to the difference in the arrangement of the even-numbered light-emitting chips 400 and the odd-numbered light-emitting chips 400 in the sub-scanning direction. Therefore, when an exposure head 106 in which the light-emitting chips 400 are arranged in a staggered pattern is used, the timing of data transmission is shifted depending on the rotation speed of the photosensitive member 102, thereby controlling the exposure timing on the photosensitive member 102 to match.

[0099] With the above configuration, the image forming apparatus 1 can scan an original and print it out, or can print out based on image data obtained from an external device.

[0100] (PG Department) As described above, the image data processing unit 703 has PG units (RGB-PG unit 1302, CMYK-PG unit 1306, binary data PG unit 1310, and light emission control PG unit 1316). The PG units are arranged downstream of the image processing module that changes the format of image data. The PG units are used for debugging the downstream image processing modules, checking their operation, and generating data for adjustment images used to adjust color in the reading unit 100 and the image creating unit 103.

[0101] In this embodiment, the RGB-PG unit 1302 is provided at the beginning of the image data processing unit 703 where image data is input. The CMYK-PG unit 1306 is provided after the color space conversion unit 1305, which converts the color space of the image data from the RGB color space to the CMYK color space. The binary data PG unit 1310 is provided after the quantization processing unit 1309, which converts multi-value image data into binary image data. The light emission control PG unit 1316 is provided at the final stage of the image data processing unit 703.

[0102] In the exposure head 106, which has multiple light-emitting elements arranged in the main scanning direction and sub-scanning direction, it is necessary to adjust the light intensity of each light-emitting element individually and check the operation of each light-emitting element in order to form higher quality images. Therefore, it is necessary to turn each light-emitting element in the exposure head 106 on and off individually and check the status at that time. However, in PG units that perform processing upstream of image processing, such as the RGB-PG unit 1302, CMYK-PG unit 1306, and binary data PG unit 1310, it is difficult to generate image data for individually controlling the on / off of each light-emitting element.

[0103] For example, the light-emitting elements of each CMYK exposure head 106 are controlled using RGB multi-value image data generated by the RGB-PG unit 1302 at 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction. In this case, the multi-value image data is converted through image density changes caused by filtering by the MTF correction unit 1303, image density changes for each color caused by the scanner color correction unit 1304, and color space conversion from RGB color space to CMYK color space by the color space conversion unit 1305. As a result, even if the multi-value image data generated by the RGB-PG unit 1302 is data for individually controlling each light-emitting element, there is a possibility that the control of each light-emitting element will become impossible due to processing by each subsequent image processing module. The RGB-PG unit 1302 needs to generate multi-value image data that takes into account the processing by each subsequent image processing module, but generating such image data is extremely difficult.

[0104] The CMYK multi-value image data generated by the CMYK-PG unit 1306 at 600 dpi in the main scanning direction and 600 dpi in the sub-scanning direction controls the light-emitting elements of each CMYK exposure head 106. In this case, the resolution of the multi-value image data is converted by the downstream magnification processing unit 1307 to 2400 dpi in the main scanning direction and 600 dpi in the sub-scanning direction, changing the pixel value interpolated by the difference in image density between adjacent pixels. This changes the high-level or low-level image data when binarized by the downstream quantization processing unit 1309. Thus, even if the multi-value image data generated by the CMYK-PG unit 1306 is data for individually controlling each light-emitting element, there is a possibility that the control of each light-emitting element will become impossible due to processing by each downstream image processing module. The CMYK-PG unit 1306 needs to generate multi-value image data that takes into account the processing by each downstream image processing module, but generating such image data is extremely difficult.

[0105] The binary data PG unit 1310 generates binary image data consisting of CMYK binary data at 2400 dpi in the main scanning direction and 600 dpi in the sub-scanning direction to control the light-emitting elements of each CMYK exposure head 106. In this case, the downstream shading processing unit 1313 performs corrections to accommodate the individual conditions of each device, such as lens periodicity unevenness and light intensity unevenness. As a result, even if the binary image data generated by the binary data PG unit 1310 is data for individually controlling each light-emitting element, there is a possibility that the control of each light-emitting element will become impossible due to processing by each downstream image processing module. The binary data PG unit 1310 needs to generate image data that takes into account the processing by each downstream image processing module, but generating such image data is extremely difficult.

[0106] Furthermore, when controlling the light-emitting elements of each CMYK exposure head 106 using binary image data generated by the binary data PG unit 1310, it is possible to bypass the image processing module at the subsequent stage. However, even in this case, the binary image data in the main scanning direction and sub-scanning direction is converted twice by the resolution conversion unit 1314. This makes it difficult to control each light-emitting element individually.

[0107] In this embodiment, a light emission control PG unit 1316 is used as a PG module that generates image data for individually turning on and off each light emitting element in the exposure head 106. The light emission control PG unit 1316 generates data for the printed circuit board 202 that matches the image quality of the image formed by the image forming unit 103. In other words, the light emission control PG unit 1316 generates binary image data with the same image quality (resolution, color) as the image represented by the binary image data output from the image position control unit of the image data processing unit 703. For example, the light emission control PG unit 1316 generates binary image data consisting of CMYK binary data with a resolution of 4800 dpi in the main scanning direction and 1200 dpi in the sub-scanning direction. This binary image data controls the individual turning on and off of each light emitting element in each light emitting chip 400.

[0108] The subsequent processing of the light emission control PG unit 1316 involves the light emission control unit 705 simply outputting the binary image data generated by the light emission control PG unit 1316 in accordance with the data input format of the printed circuit board 202. For this reason, the binary image data generated by the light emission control PG unit 1316 is input directly to each light emitting element of the light emitting chip 400 mounted on the printed circuit board 202. The light emission control PG unit 1316 of this embodiment generates binary image data for five light emission control patterns: an all-off pattern, an all-on pattern, a block light-on pattern, an arbitrary light-on pattern, and an individual line light-on pattern. The light emission control patterns individually control the lighting states of all light emitting elements.

[0109] Each light emission control pattern of this embodiment will be described below. In the following description, in the diagrams showing the lighting states of the light emitting chips 400, the numbers assigned to the light emitting elements have the following correspondence relationship. 1: R0_0 in Figure 11 2: R0_1 in Figure 11 3: R0_2 in Figure 11 4: R0_3 in Figure 11 … 2989: R747_0 in Figure 11 2990: R747_1 in Figure 11 2991: R747_2 in Figure 11 2992: R747_3 in Figure 11

[0110] Fig. 19 is an explanatory diagram of the all-off pattern. In the all-off pattern, as shown in Fig. 19(a), all 2992 light-emitting elements of each light-emitting chip 400 are turned off. In this case, as shown in Fig. 19(b), the state of the binary image data BDATA is such that all values ​​for 2992 cycles after the line synchronization signal is output are at low level.

[0111] Fig. 20 is an explanatory diagram of the full lighting pattern. In the full lighting pattern, as shown in Fig. 20(a), all 2992 light-emitting elements of each light-emitting chip 400 are lit. In this case, as shown in Fig. 20(b), the state of the binary image data BDATA is such that all values ​​for 2992 cycles are high level after the line synchronization signal is output.

[0112] Fig. 21 is an explanatory diagram of a block lighting pattern. In the block lighting pattern, as shown in Fig. 21, light-emitting elements in a range from a predetermined light emission start position to a light emission stop position for each light-emitting chip 400 are set to a lighting state. In this embodiment, a lit pixel position 0, an unlit pixel position 0, a lit pixel position 1, an unlit pixel position 1, a lit pixel position 2, and an unlit pixel position 2 are set in the register setting unit 1317 so that three blocks can be set for each light-emitting chip 400.

[0113] FIG. 22 is an explanatory diagram of lighting setting of a block lighting pattern. In FIG. 22(a), the lighting pixel position is set as follows: 0:9, unlit pixel position 0:21, lighting pixel position 1:27, unlit pixel position 1:35, lighting pixel position 2:43, and unlit pixel position 2:48. In this case, as shown in FIG. 22(b), after the line synchronization signal is output, the binary image data BDATA goes high in the 10th cycle and goes low in the 21st cycle. The binary image data BDATA goes high in the 30th cycle and goes low in the 33rd cycle. The binary image data BDATA goes high in the 40th cycle and goes low in the 45th cycle. As a result, the lighting pattern shown in FIG. 22(a) is obtained in the light-emitting chip 400.

[0114] FIG. 23 is an explanatory diagram of an arbitrary lighting pattern. In the arbitrary lighting pattern, as shown in FIG. 23, a lighting pattern of light-emitting elements in a predetermined range is repeatedly set for each light-emitting chip 400. In FIG. 23, the lighting pattern is set for light-emitting elements at positions 10 to 29, and the lighting pattern is repeated. In FIG. 23, the lighting pattern is set so that light-emitting elements at positions 10, 14, and 18 are turned on and light-emitting elements at other positions are turned off. In this embodiment, a start position setting value, a cycle setting value, and a continuous lighting setting value for each light-emitting chip 400 are set in the register setting unit 1317.

[0115] FIG. 24 is an explanatory diagram of lighting setting of an arbitrary lighting pattern. A case where the start position setting value is 9, the cycle setting value is 12, and the continuous lighting setting value is 1 will be described. In this case, as shown in FIG. 24(a), the binary image data BDATA becomes high level in the 9th cycle after the line synchronization signal is output, and then becomes high level data once again in the 13th cycle. The binary image data BDATA forms one lighting pattern for 12 cycles from the 9th cycle to the 20th cycle. This lighting pattern is repeated up to 2992 cycles. As a result, the light-emitting chip 400 has a lighting pattern as shown in FIG. 24(b).

[0116] FIG. 25 is an explanatory diagram of lighting setting of another arbitrary lighting pattern. A case where the start position setting value is 5, the cycle setting value is 5, and the continuous lighting setting value is 0 will be described. In this case, as shown in FIG. 25(a), the binary image data BDATA becomes high level in the fifth cycle after the line synchronization signal is output, and thereafter, the binary image data BDATA does not become high level data continuously in the same column. Five cycles of the binary image data BDATA, from the fifth cycle to the ninth cycle, form one lighting pattern. This lighting pattern is repeated up to 2992 cycles. As a result, the light-emitting chip 400 has a lighting pattern as shown in FIG. 25(b).

[0117] FIG. 26 is an explanatory diagram of each line lighting pattern. In each line lighting pattern, light-emitting elements of a specific line are lit for each light-emitting chip 400. In the example of FIG. 26, a lighting line position 1, a lighting pixel position 2, a lighting pixel position 3, and a lighting pixel position 4 are set in the register setting unit 1317 so that lighting of each line can be set for each light-emitting chip 400. FIG. 26 illustrates a case where only the light-emitting elements of Line 1 are lit, and a case where the light-emitting elements of Lines 2 and 4 are lit.

[0118] FIG. 27 is a diagram illustrating an example of setting each line lighting pattern. A case will be described in which lighting line position 1:0, lighting pixel position 2:1, lighting pixel position 3:0, and lighting pixel position 4:0 are set. In this case, as shown in FIG. 27(a), after the line synchronization signal is output, the binary image data BDATA is repeatedly set to a high level in the second cycle, the sixth cycle, the tenth cycle, and 2+4×N cycles. As a result, the light-emitting chip 400 has a lighting pattern in which all of the light-emitting elements in the second column of the four columns are lit, as shown in FIG. 27(b).

[0119] FIG. 28 is a diagram illustrating an example of setting an arbitrary lighting pattern. A case will be described in which the start position setting value is 2, the cycle setting value is 4, and the continuous lighting setting value is 0. In this case, as shown in FIG. 28(a), the binary image data BDATA becomes high level in the second cycle after the line synchronization signal is output. Although the binary image data BDATA is not set so that high-level data is output continuously in the same column thereafter, four cycles from the second cycle to the fifth cycle form one lighting pattern. This lighting pattern is repeated up to 2992 cycles. As a result, the light-emitting chip 400 can obtain the same lighting pattern as FIG. 27(b), as shown in FIG. 28(b). The lighting pattern of each line can be easily controlled without complex settings such as those for an arbitrary lighting pattern.

[0120] 29 is a configuration diagram of the light emission control PG unit 1316. The light emission control PG unit 1316 includes a PG pattern generation unit 2701, a PG pattern storage unit 2702, a PG pattern reading unit 2703, and an output selection unit 2704. The light emission control PG unit 1316 executes the processing operations of each built-in unit in synchronization with a clock signal obtained from a clock generation unit 702. Each unit of the light emission control PG unit 1316 uses a synchronization signal obtained from a synchronization signal generation unit 706 as the reference for the timing of inputting and outputting image data. The PG pattern generation unit 2701 of this embodiment generates binary image data (PG pattern data) in CMYK with a resolution of 4800 dpi in the main scanning direction and 1200 dpi in the sub-scanning direction.

[0121] The light emission control PG unit 1316 receives a mode selection setting value from the register setting unit 1317. The mode selection setting value is a value indicating one of the light emission control patterns: all-off pattern, all-on pattern, block lighting pattern, arbitrary lighting pattern, and each line lighting pattern. The light emission control PG unit 1316 generates PG pattern data for the pattern set by the mode selection setting value.

[0122] 19(a), PG pattern data for turning off all 2992 light-emitting elements is generated for each light-emitting chip 400. When the mode selection setting value sets the all-off pattern, PG pattern data for turning on all 2992 light-emitting elements is generated for each light-emitting chip 400. When the mode selection setting value sets the all-on pattern, PG pattern data for turning on all 2992 light-emitting elements is generated for each light-emitting chip 400.

[0123] When the mode selection setting value sets a block lighting pattern, a mode detail register setting value is also set. The mode detail register setting value sets the light-emitting elements to be lit. The mode detail register setting value is, for example, setting values ​​of lit pixel position 0, unlit pixel position 0, lit pixel position 1, unlit pixel position 1, lit pixel position 2, and unlit pixel position 2. Using these setting values, as described in FIG. 22(a), PG pattern data is generated for each light-emitting chip 400, instructing the lighting and extinguishing of each light-emitting element for each block.

[0124] When the mode selection setting value is an arbitrary lighting pattern, a mode detail register setting value is further set. The mode detail register setting value is, for example, setting values ​​of lighting line position 1, lighting pixel position 2, lighting pixel position 3, and lighting pixel position 4. As described with reference to FIGS. 24(b) and 25(b), these setting values ​​generate PG pattern data for each light-emitting chip 400 that instructs the lighting and extinguishing of light-emitting elements of a line according to the setting. When the mode selection setting value is a line lighting pattern, the mode detail register setting value sets a start position setting value, a cycle setting value, and a continuous lighting setting value. As described with reference to FIGS. 27(b) and 28(b), these setting values ​​generate PG pattern data for each light-emitting chip 400 that instructs the lighting and extinguishing of light-emitting elements according to the setting.

[0125] The PG pattern generation unit 2701 generates PG pattern data using the mode selection setting value and, if necessary, the mode detail register setting value acquired from the register setting unit 1317. The PG pattern generation unit 2701 may be a memory that stores in advance PG pattern data corresponding to the mode selection setting value and the mode detail register setting value. In this case, the PG pattern generation unit 2701 generates PG pattern data by reading from the memory the PG pattern data corresponding to the mode selection setting value and the mode detail register setting value acquired from the register setting unit 1317.

[0126] The PG pattern storage unit 2702 is a memory that stores the PG pattern data generated by the PG pattern generation unit 2701. The PG pattern storage unit 2702 has a capacity that can store, for example, PG pattern data that is binary image data in CMYK with a resolution of 4800 dpi in the main scanning direction and 1200 dpi in the sub-scanning direction for each light-emitting chip 400. Under the control of the CPU 701, the PG pattern reading unit 2703 reads out the PG pattern data from the PG pattern storage unit 2702 in accordance with the timing of the synchronization signal, and transmits the read data to the output selection unit 2704.

[0127] The output selection unit 2704 selects data to be output to the light emission control unit 705 . During normal operation, the output selection unit 2704 receives an output selection signal that instructs it to select image data processed by the image position control unit 1315, based on the output selection setting value from the register setting unit 1317. In this case, the output selection unit 2704 outputs the image data processed by the image position control unit 1315 to the light emission control unit 705. When outputting PG pattern data, the output selection unit 2704 receives an output selection signal that instructs it to select PG pattern data read out by the PG pattern reading unit 2703, based on the output selection setting value from the register setting unit 1317. In this case, the output selection unit 2704 outputs the PG pattern data to the light emission control unit 705.

[0128] 30 is a flowchart showing the process of generating PG pattern data by the light emission control PG unit 1316. This process is executed when the power is turned on or when reset is released.

[0129] When processing starts, the CPU 701 sets various image processing parameters in the register setting unit 1317 and sets registers for each PG unit (S2801). When register setting is complete (S2802: Y), the CPU 701 determines whether the output mode for PG pattern data is set (S2803). If the output mode for PG pattern data is not set (S2803: N), the CPU 701 ends processing because it will not output PG pattern data.

[0130] If the output mode for PG pattern data is set (S2803: Y), the CPU 701 causes the light emission control PG unit 1316 to generate PG pattern data (S2804). At this time, the CPU 701 causes the register setting unit 1317 to transmit a mode selection setting value and, if necessary, a mode detail register setting value to the light emission control PG unit 1316. The light emission control PG unit 1316 generates PG pattern data based on these setting values ​​acquired from the register setting unit 1317.

[0131] When generation of the PG pattern data is completed (S2805: Y), the CPU 701 sends a read start command to the light emission control PG unit 1316 (S2806: Y). Upon receiving the read start command, the light emission control PG unit 1316 outputs the generated PG pattern data at the timing when the next line synchronization signal is input (S2807: Y, S2808). When all PG pattern data has been output from the light emission control PG unit 1316, the CPU 701 ends the process (S2809: Y).

[0132] The PG pattern data thus output is input to the light emission control unit 705. The light emission control unit 705 individually controls the light emission of each light-emitting element of each light-emitting chip 400 based on the acquired PG pattern data. Whether each light-emitting element is lighting up correctly is confirmed based on the detection results of the optical sensor 113 of the image formed on the sheet and the detection results of the light intensity output from each light-emitting element by a predetermined sensor. The CPU 701 confirms whether each light-emitting element is operating normally based on such detection results. This maintains the quality of the image to be formed. The operation of each light-emitting element is confirmed using such PG pattern data, for example, during the manufacture of the image forming apparatus 1 or before shipping.

[0133] As described above, the image forming apparatus 1 of this embodiment adjusts the light intensity of each individual light-emitting element in the exposure head 106, which has multiple light-emitting elements arranged in a plane in the main scanning direction and sub-scanning direction, and checks for malfunctions. This maintains the image quality of the formed image. To achieve this, the image forming apparatus 1 also has a PG module located farthest downstream of the image processing module, in addition to the PG module that is conventionally located upstream of the image processing module.

[0134] The most downstream PG module generates PG pattern data that matches the number of pixels in the main scanning direction and sub-scanning direction of the output image and the gradation of the output image density. The PG pattern data generated by the most downstream PG module is used to control the light emission of each light-emitting element without undergoing image processing by other image processing modules after generation. Such PG pattern data becomes control data for turning on and off each of the multiple light-emitting elements in each light-emitting chip 400.

[0135] In this embodiment, the description has been given taking as an example an exposure head 106 having a configuration in which a plurality of light-emitting chips 400, each configured with a plurality of light-emitting elements arranged in a staggered pattern in the main scanning direction and the sub-scanning direction. The configuration of the exposure head 106 is not limited to this, and it may also be a configuration in which light-emitting elements are arranged in a line in the main scanning direction, or a configuration in which light-emitting elements are arranged individually rather than in units of light-emitting chips 400. Even with such an exposure head 106 configuration, it is possible to control the light emission of each light-emitting element using PG pattern data generated by the PG module provided at the most downstream side.

Claims

1. A photoreceptor; an exposure unit having a plurality of light-emitting elements and exposing the photosensitive member to the light-emitting elements to form an image; a control means for controlling the lighting of the plurality of light-emitting elements; The control means an image processing unit that performs predetermined image processing on first image data for forming the image; a generating means for generating second image data for individually controlling the lighting of the plurality of light-emitting elements, the generating means being provided at a subsequent stage of the image processing means; a light emission control means for transmitting the first image data that has been subjected to the image processing to the exposure means when forming the image, and transmitting the second image data to the exposure means when checking whether the plurality of light emitting elements are operating normally. Image forming device.

2. The generating means generates the second image data having the same image quality as the first image data that has been image-processed by the image processing means.

2. The image forming apparatus according to claim 1.

3. the control means confirms whether the plurality of light-emitting elements are operating normally based on a result of the exposure means causing the plurality of light-emitting elements to emit light based on the second image data.

3. The image forming apparatus according to claim 2.

4. a detection means for detecting whether the plurality of light emitting elements are lit; The control means checks whether the plurality of light-emitting elements are operating normally based on the detection result by the detection means.

4. The image forming apparatus according to claim 3.

5. a transfer means for transferring the image formed on the photoreceptor to a sheet; The detecting means detects the image transferred onto the sheet.

5. The image forming apparatus according to claim 4.

6. The detecting means detects the amount of light output from each of the plurality of light-emitting elements.

5. The image forming apparatus according to claim 4.

7. the generating means generates binary image data of a predetermined light emission control pattern as the second image data.

2. The image forming apparatus according to claim 1.

8. The light emission control patterns include an all-off pattern that turns all light-emitting elements off, an all-on pattern that turns all light-emitting elements on, a block lighting pattern that turns light-emitting elements within a predetermined range on, an arbitrary lighting pattern that repeats a lighting pattern that turns on light-emitting elements at specific positions within a predetermined range and light-emitting elements at other positions on, and an individual line lighting pattern that lights up light-emitting elements in a specific line.

8. The image forming apparatus according to claim 7.

9. a register in which a mode selection setting value indicating the light emission control pattern is set; the generating means generates the second image data based on a light emission control pattern indicated by the mode selection setting value acquired from the register.

9. The image forming apparatus according to claim 7.

10. the control means includes second generation means for generating third image data for confirming the operation of the image processing means; The image processing means is provided at a subsequent stage of the second generation means.

2. The image forming apparatus according to claim 1.

11. the exposure means has a plurality of light-emitting chips, each of which has a plurality of light-emitting elements mounted thereon; The plurality of light emitting chips are arranged in a staggered pattern in a predetermined direction.

2. The image forming apparatus according to claim 1.

12. The plurality of light emitting elements mounted on the light emitting chip are arranged in a stepped pattern. The image forming apparatus according to claim 11.

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