Information processing device, image forming apparatus, control method, and program

Abstract

To solve such a problem that correction accuracy of a light amount in an image forming apparatus is insufficient.SOLUTION: An information processing device generates correction data for correcting a light amount of an image forming apparatus having an exposure head including a plurality of light-emitting element array chips each having a plurality of light-emitting elements. The information processing device comprises: first correction means that generates first correction data for correcting a light amount difference at boundaries between adjacent light-emitting element array chips; and second correction means that generates second correction data for correcting a light amount distribution of the exposure head corrected by the first correction data.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to an information processing apparatus, an image forming apparatus, a control method, and a program. [Background technology]

[0002] An image forming apparatus that prints an image and has an exposure head and a photosensitive rod is known. The exposure head has a plurality of light-emitting element array chips each having a plurality of light-emitting elements. In such an image forming apparatus, the light-emitting elements of the exposure head irradiate light onto the photosensitive rod, thereby printing an image on a recording medium such as paper.

[0003] In such an image forming apparatus, there is a difference in the amount of light emitted by the light emitting elements, and therefore, a technique for correcting the amount of light is known.

[0004] For example, Patent Document 1 discloses a technology in which the difference in the average light intensity of each light-emitting element array chip is calculated and corrected based on the variation in density obtained by reading a printed chart using a scanner or the like, and then the light intensity between the ends of the light-emitting element array chips is corrected. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-1679 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the technique of Patent Document 1, the light amount is corrected in a state where there is a steep difference in the light amount at the boundary between the light emitting element array chips, and therefore the accuracy of the light amount correction is not sufficient.

[0007] Therefore, the present invention provides an information processing apparatus, an image forming apparatus, a control method, and a program for controlling an image forming apparatus that can improve the accuracy of light amount correction of the image forming apparatus. [Means for solving the problem]

[0008] In order to solve this problem, for example, an information processing device of the present invention has the following arrangement: 1. An information processing device that generates correction data for correcting the amount of light of an image forming device having an exposure head including a plurality of light emitting element array chips each having a plurality of light emitting elements, a first correction means for generating first correction data for correcting a difference in light intensity at a boundary between adjacent light emitting element array chips; a second correction means for generating second correction data for correcting the light quantity distribution of the exposure head corrected by the first correction data; Equipped with. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the accuracy of light amount correction in an image forming apparatus. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing the overall configuration of an image forming apparatus according to an embodiment; [Figure 2] FIG. 2 is a diagram illustrating an exposure head and a photosensitive drum according to the embodiment. [Figure 3] FIG. 2 is a plan view of a printed circuit board on which a group of light-emitting elements and connectors are arranged according to an embodiment. [Figure 4] FIG. 2 is a plan view showing the outline of the configuration of the light-emitting element array chip according to the embodiment. [Figure 5] FIG. 3 is a cross-sectional view of a part of a light-emitting unit according to the embodiment. [Figure 6] FIG. 4 is a plan view illustrating overlapping of light emitting elements according to the embodiment. [Figure 7] FIG. 2 is a block diagram illustrating a control system of the image forming apparatus according to the embodiment. [Figure 8]FIG. 2 is a block diagram of an internal circuit of the light-emitting element array chip according to the embodiment. [Figure 9] FIG. 2 is a block diagram illustrating the configuration of a light amount correction unit according to the embodiment. [Figure 10] 5A to 5C are diagrams illustrating a process of correcting an image according to an embodiment. [Figure 11] A diagram of a light intensity correction chart printed to obtain light intensity variations. [Figure 12] FIG. 10 is a flowchart of a correction process for generating correction data for correcting the amount of light. [Figure 13] FIG. 10 is a diagram showing the light amount distribution of the exposure head before correction in the longitudinal direction of the light emitting element array chip. [Figure 14] 10 is a diagram showing the light amount distribution of the exposure head after correction in the longitudinal direction of the light emitting element array chip. [Figure 15] FIG. 10 is a diagram showing the light intensity distribution before correction in the light-emitting element array chip. [Figure 16] 5A and 5B are diagrams for explaining the influence of sampling areas and dots for each light-emitting element array chip according to the embodiment. [Figure 17] FIG. 10 is a diagram showing the light intensity distribution of 18 sample area rows corresponding to one light-emitting element array chip. [Figure 18] FIG. 10 is a diagram showing the light amount distribution in a case where vertical streaks occur in an image. [Figure 19] FIG. 2 is a plan view showing a state in which light-emitting element array chips are arranged. [Figure 20] FIG. 2 is a block diagram illustrating the hardware configuration of a control system of the image forming apparatus according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be described in detail 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] <Embodiment> (Overall configuration of image forming apparatus) An electrophotographic image forming apparatus 10 according to this embodiment will be briefly described. FIG. 1 is a diagram showing the overall configuration of the image forming apparatus 10. The image forming apparatus 10 includes a scanner unit 100, an image creating unit 103, a fixing unit 104, a paper feed / transport unit 105, an optical sensor 113, and a printer control unit (not shown) that controls these units. In the following description, the term "image" may include "image data."

[0013] The scanner unit 100 irradiates a document placed on a document table with light to optically read the image of the document. The scanner unit 100 converts the light of the read document image into an electrical signal to create and output image data.

[0014] The imaging unit 103 has four sets of image forming units 101a, 101b, 101c, and 101d. When there is no need to distinguish between the image forming units 101a, 101b, 101c, and 101d, they will be referred to as image forming units 101. The number of sets of image forming units 101 is not limited to four and may be changed as appropriate. This embodiment has four sets of image forming units 101a, 101b, 101c, and 101d corresponding to four colors: cyan (C), magenta (M), yellow (Y), and black (K). The four sets of image forming units 101 are arranged in the order of cyan (C), magenta (M), yellow (Y), and black (K). The image forming unit 101 performs a series of electrophotographic processes (charging, exposure, development, and transfer) on a recording medium such as paper that is conveyed thereto. After a predetermined time has elapsed since the start of image formation at the cyan station, the quadruple image forming unit 101 sequentially performs image formation operations for magenta, yellow, and black. As a result, the quadruple image forming unit 101 sequentially prints images of the corresponding colors, forming a full-color image on paper.

[0015] Each of the image forming units 101 has a photosensitive drum 102, an exposure head 106, a charger 107, and a developing unit 108. The photosensitive drum 102 rotates. The charging unit 107 charges the photosensitive drum 102 as it rotates. The exposure head 106 irradiates the photosensitive drum 102 with light in accordance with image data to form an electrostatic latent image. The developing unit 108 develops the electrostatic latent image formed on the photosensitive drum 102 with toner, thereby generating a toner image. The toner image is transferred to paper being transported on a transfer belt 111.

[0016] The paper feed / transport unit 105 includes an internal paper feed unit 109a, an internal paper feed unit 109b, an external paper feed unit 109c, a manual paper feed unit 109d, registration rollers 110, and a transfer belt 111. In the paper feed / transport unit 105, a predetermined paper feed unit among the internal paper feed unit 109a, the internal paper feed unit 109b, the external paper feed unit 109c, and the manual paper feed unit 109d feeds paper. The fed paper is transported to the registration rollers 110. The registration rollers 110 transport the paper onto the transfer belt 111 at the timing when the toner image formed in the image creation unit 103 is transferred onto the paper. An optical sensor 113 is disposed opposite the transfer belt 111. The optical sensor 113 detects the position of a test chart printed on the transfer belt 111 to derive the amount of color misregistration between each station. The calculated color misregistration amount is notified to an image controller, which will be described later, and the image position of each color is corrected. This control allows a full-color toner image to be transferred onto the paper without color misregistration.

[0017] Fixing unit 104 has a plurality of opposing rollers and a heat source such as a halogen heater. In fixing unit 104, the toner on the paper onto which the toner image has been transferred and transported from transfer belt 111 is melted by the heat of the heat source and the pressure of the rollers, thereby fixing the toner to the paper. Fixing unit 104 then ejects the paper onto which the toner image has been fixed to the outside of image forming apparatus 10 using paper ejection rollers 112.

[0018] The printer control unit (not shown) communicates with an overall control unit (not shown) that controls the entire image forming apparatus 10, and executes control of image formation and the like in accordance with its instructions, while managing the status of the aforementioned scanner, image creation, fixing, and paper feed / transport units to ensure that the entire unit operates smoothly and in harmony.

[0019] (Exposure head configuration) The exposure head 106 that exposes the photosensitive drum 102 will now be described. Fig. 2 is a diagram illustrating the exposure head and the photosensitive drum. Fig. 2(a) is a diagram illustrating the arrangement of the exposure head 106 relative to the photosensitive drum 102. Fig. 2(b) is a diagram illustrating light emitted from a light-emitting element group 201 being focused on the photosensitive drum 102 by a rod lens array 203.

[0020] The exposure head 106 and the photosensitive drum 102 are each attached to the image forming apparatus 10 by attachment members (not shown). The exposure head 106 has a light-emitting element group 201, a printed circuit board 202, a rod lens array 203, and a housing 204. The light-emitting element group 201 has an array of light-emitting elements. The light-emitting elements are, for example, semiconductor light-emitting elements and LEDs (Light Emitting Diodes) such as organic EL (Electro Luminescence) elements. The light-emitting element group 201 is mounted on the printed circuit board 202. The rod lens array 203 is arranged on the optical path of light emitted from the light-emitting element group 201. The rod lens array 203 has an array of rod lenses. The housing 204 holds the light-emitting element group 201, the printed circuit board 202, and the rod lens array 203.

[0021] When printing an image, the exposure head 106 causes the light emitting elements on the chip surfaces of the light emitting element group 201 to emit light in accordance with image data. The rod lens array 203 focuses the light emitted by the light emitting element group 201 onto the photosensitive drum 102. As a result, an electrostatic latent image is formed on the photosensitive drum 102.

[0022] In the factory, adjustment of the exposure head 106 is performed individually. The adjustment involves focus adjustment, which adjusts the spot size at the light-condensing position of the exposure head 106, to a predetermined size, and light intensity adjustment. The photosensitive drum 102 and the rod lens array 203, and the rod lens array 203 and the light-emitting element group 201 are positioned so that predetermined intervals are maintained between them, so that light emitted from the light-emitting element group 201 forms an image on the photosensitive drum 102. Therefore, during focus adjustment, the mounting position of the rod lens array 203 is adjusted so that the distance between the rod lens array 203 and the light-emitting element group 201 is a desired value. During light intensity adjustment, each light-emitting element is individually turned on in sequence, and the drive current of each light-emitting element is adjusted so that the light condensed through the rod lens array 203 has a predetermined light intensity.

[0023] (Board configuration) Fig. 3 is a plan view of the printed circuit board 202 on which the light-emitting element group 201 and the connector 305 are arranged. Fig. 3(a) is a plan view of the surface opposite to the surface on which the light-emitting element group 201 is mounted (hereinafter referred to as the light-emitting element non-mounting surface). Fig. 3(b) is a plan view of the surface on which the light-emitting element group 201 is mounted (hereinafter referred to as the light-emitting element mounting surface).

[0024] The light emitting element group 201 is configured by arranging 17 light emitting element array chips 400-1 to 400-17 in a staggered pattern on the printed circuit board 202. When it is not necessary to distinguish between the light emitting element array chips 400-1 to 400-17, they will be referred to as light emitting element array chips 400. The arrangement direction of the light emitting element array chips 400 is an example of the arrangement direction. The light emitting element group 201 includes a plurality of light emitting element array chips 400 arranged on the surface of the printed circuit board 202, and can be considered a surface-emitting device. Each light emitting element array chip 400 has 748 light emitting elements functioning as light emitting points arranged along its longitudinal direction at a predetermined pitch according to the chip resolution. In this embodiment, the pitch between adjacent light emitting elements in the chip longitudinal direction is a pitch corresponding to a resolution of 1200 dpi (approximately 21.16 μm), and the distance from one end to the other of the 748 light emitting elements in the light emitting element array chip 400 is approximately 15.8 mm. Seventeen light emitting element array chips 400 are arranged in the light emitting element group 201. As a result, the number of light-emitting elements that can be exposed by the light-emitting element group 201 becomes 12,716, making it possible to form an image corresponding to an image width of approximately 267 mm. The light-emitting element array chips 400-1 to 400-17 are arranged in two staggered rows. Each row of the light-emitting element array chips 400 is arranged along the longitudinal direction of the printed circuit board 202.

[0025] FIG. 3(c) is an enlarged plan view of the boundary between the light-emitting element array chips. As described above, in the light-emitting element array chip 400, the light-emitting elements 602 are arranged at intervals of 1200 dpi. Four rows of the light-emitting elements 602 are arranged in the short-side direction. Each row of the light-emitting elements 602 is arranged with a positional shift of approximately 5 μm (equivalent to 4800 dpi) in the long-side direction. The light-emitting elements 602 are arranged so that the interval Ly between the light-emitting points (light-emitting elements 602) of the two staggered rows of the light-emitting element array chips 400 in the short-side direction of the exposure head 106 is approximately 105 μm (equivalent to five pixels at 1200 dpi and ten pixels at 2400 dpi). In addition, in the long-side direction of the exposure head 106, the light-emitting elements 602 are arranged so as to overlap between the light-emitting element array chips 400. In this embodiment, four light-emitting elements 602 at the end overlap. The amount of overlap is not limited to four light-emitting elements 602. For example, the overlap amount may be determined based on the maximum amount of mounting variation of the mounting device (die bonder) so that no gaps are formed between the light emitting elements 602 of adjacent light emitting element array chips 400 .

[0026] A connector 305 is arranged on the non-light-emitting element mounting surface of the printed circuit board 202. The connector 305 receives a control signal output from the image controller unit to control the light-emitting element array chip 400, and connects the power supply line to the light-emitting element array chip 400. Each light-emitting element array chip 400 is driven via the connector 305.

[0027] (Configuration of light-emitting element array chip) 4 is a plan view showing the outline of the configuration of the light emitting element array chip 400. The light emitting element array chip 400 has a light emitting substrate 402, a light emitting section 404, a circuit section 406, and a plurality of WB pads 408.

[0028] The light emitting substrate 402 may be a silicon substrate. The process technology for forming integrated circuits on silicon substrates has also been developed, and silicon substrates are already used as substrates for various integrated circuits, so high-speed, highly functional circuits can be formed at high density. In addition, silicon substrates have the advantage of being inexpensive, as large-diameter wafers are readily available.

[0029] The light emitting section 404 includes a plurality of light emitting elements 602 provided on the light emitting substrate 402 .

[0030] The circuit unit 406 is built into the light emitting substrate 402. The circuit unit 406 controls the light emitting unit 404. The circuit unit 406 may be configured to include an analog drive circuit, a digital control circuit, or both. In this embodiment, the circuit unit 406 includes a drive unit that drives the light emitting element, a data transfer unit that generates a light emitting signal, and a light emitting signal generation unit. The circuit unit 406 is formed on a Si substrate, thereby making it a circuit that can respond to high speeds.

[0031] The WB pads 408 are an abbreviation for wire bonding pads, and are provided on the light emitting substrate 402. Power supply to the circuit section 406 and input / output of signals from outside the light emitting element array chip 400 are performed via the WB pads 408.

[0032] (Light emitting section configuration) Fig. 5 is a cross-sectional view of a part of light-emitting section 404 taken along line AA in Fig. 4. The configuration of light-emitting section 404 will be described with reference to Fig. 5.

[0033] The light-emitting section 404 has multiple lower electrodes 504, light-emitting layers 506, and upper electrodes 508. The multiple lower electrodes 504, light-emitting layers 506, and upper electrodes 508 are stacked on the light-emitting substrate 402. The lower electrodes 504 are independent electrodes provided for each light-emitting element (pixel). The light-emitting layer 506 is a layer provided in common to the multiple light-emitting elements and emits light when, for example, a current flows through it. The upper electrode 508 is a common electrode provided in common to the multiple light-emitting elements. The multiple lower electrodes 504 have a width W in the X direction in the figure, and are formed with a predetermined distance dx between adjacent lower electrodes 504 in the X direction. When a voltage is applied between the lower electrodes 504 and the upper electrode 508, a current flows from the lower electrodes 504 to the upper electrode 508. This causes the light-emitting layers 506 between the lower electrodes 504 and the upper electrode 508 to emit light. By making the electrode spacing dx wider than the spacing dz between the lower electrode 504 and the upper electrode 508, it is possible to eliminate leakage current between adjacent lower electrodes 504 and prevent erroneous light emission from adjacent pixels.

[0034] In the manufacturing process of the light-emitting section 404, the light-emitting layer 506 is formed on the lower electrode 504 after the lower electrode 504 is formed. In the drawing, the light-emitting layer 506 is continuously formed over the entire surface, but this is not limited to this. For example, the light-emitting layer 506 may be divided into sections of approximately the same size as the lower electrode 504. The light-emitting layer 506 may be, for example, an organic EL film. When an organic EL film is used as the light-emitting layer 506, the light-emitting layer 506 may be a laminated structure including functional layers such as an electron transport layer, a hole transport layer, an electron injection layer, a hole injection layer, an electron blocking layer, and a hole blocking layer as necessary. Furthermore, the light-emitting layer 506 may be an inorganic EL layer other than an organic EL layer.

[0035] The upper electrode 508 is formed on the light-emitting layer 506 after the light-emitting layer 506 is formed on the lower electrode 504. The upper electrode 508 is transparent to the emission wavelength of the light-emitting layer 506. Therefore, the upper electrode 508 is a transparent electrode such as indium tin oxide (ITO). In this embodiment, a configuration in which the entire upper electrode 508 is formed of a transparent electrode (ITO) will be described as an example. Note that the transparent electrode of the upper electrode 508 only needs to be formed in the openings through which light is emitted, and does not necessarily need to cover the entire light-emitting element array chip 400. For example, a transparent electrode may be formed only in the openings, and an electrode other than a transparent electrode (such as metal wiring) may be used for wiring other than the openings.

[0036] (Light emitting element arrangement (high resolution overlap arrangement)) 6 is a plan view illustrating overlapping of light-emitting elements. The light-emitting section 404 has a plurality of light-emitting elements 602-11 to 602-mn. m and n are positive integers. When there is no need to distinguish between the plurality of light-emitting elements 602-11 to 602-mn, they will be referred to as light-emitting element 602.

[0037] FIG. 6(a) is a plan view illustrating the arrangement of multiple light-emitting elements 602 in the light-emitting unit 404. The multiple light-emitting elements 602 are arranged in a row along the X direction in the figure at a predetermined interval, for example, a pitch of 21.16 μm in the case of 1200 dpi. The rows of light-emitting elements 602 along the X direction are referred to as light-emitting element rows 604-1 to 604-2. When there is no need to distinguish between light-emitting element rows 604-1 to 604-2, they are referred to as light-emitting element row 604. The multiple light-emitting elements 602 are also arranged in the Y direction at a predetermined pitch. The light-emitting elements 602 are arranged in a matrix with n elements in the row direction (X direction in the figure) and m elements in a direction different from the row direction (Y direction in the figure). In this embodiment, four rows of light-emitting elements 602 are arranged in the Y direction, but the light-emitting elements 602 may be arranged in two or more rows.

[0038] In the drawing, width W1 is the width of the light emitting element 602 in the X direction. Width W2 of the light emitting element 602 in the Y direction may be the same as width W1, but is not limited to this. Distance d1 is the distance between adjacent light emitting elements 602 in the X direction. Distance d2 is the distance between adjacent light emitting elements 602 in the Y direction. Here, distances d1 and d2 represent the above-mentioned inter-electrode distance dx in two-dimensional coordinates. Distances d1 and d2 are determined to be wider than distance dz between the upper electrode 508 and the lower electrode 504. Light emitting element columns 604-1 to 604-4 are arranged with their positions shifted in the X direction. In this embodiment, the amount of shift d3 in the position of the light emitting element columns 604 is 5 μm (equivalent to 4800 dpi).

[0039] As described above, the light emitting element columns 604 are arranged in the Y direction. Each light emitting element column 604 emits light at a different light emission timing, forming an image on the same line on the photosensitive drum 102. FIG. 6B shows light spots 606 of the light emitting element columns 604 when the light emission timing of each light emitting element column 604 is shifted and the same column on the photosensitive drum 102 is exposed. The actual width of the light spots 606 will be larger than the width W1 of the light emitting elements 602 due to factors such as lens focus misalignment. However, for the sake of simplicity, this example will be described assuming that the width of the light spots 606 is approximately equal to the width W1. The latent image potential formed on the photosensitive drum 102 by the light spots 606 of each light emitting element 602 is such that adjacent light emitting elements 602 overlap each other, eliminating sudden potential fluctuations between the light emitting elements 602 and forming a smooth latent image. If the width W1 of the light-emitting element 602 is small, the amount of overlap of the light spots 606 will be small, resulting in gaps between the light spots 606 and causing image defects such as streaks. In this embodiment, the width W1 is at least twice the amount of positional deviation d3 of the light-emitting element row 604. As a result, the light spot 606 of each light-emitting element 602 will overlap not only with the light spot 606 of the adjacent light-emitting element 602, but also with the light spot 606 of the light-emitting element 602 two positions away. As a result, this embodiment can increase resistance to streaks.

[0040] (control block) 7 is a block diagram illustrating a control system of the image forming apparatus 10. The image forming apparatus 10 further includes an image controller unit 800 electrically connected to the printed circuit board 202. In this embodiment, to simplify the explanation, processing of a single color will be described, but similar processing may be performed simultaneously in parallel for four colors.

[0041] The image controller unit 800 transmits signals for controlling the printed circuit board 202. The signals transmitted by the image controller unit 800 include a chip select signal indicating the effective range of image data, a clock signal, image data, a line synchronization signal indicating the division of each line of image data, and a communication signal with the CPU 811 of the processing device 820. Each signal is transmitted to the light emitting element array chip 400 in the printed circuit board 202 via one of a chip select signal line 805, a clock signal line 806, an image data signal line 807, a line synchronization signal line 808, and a communication signal line 809.

[0042] The image controller unit 800 processes image data and print timing. The image controller unit 800 has a processing device 820 including an image data generation unit 801, a light intensity correction unit 802, a chip data conversion unit 803, a synchronization signal generation unit 804, and a CPU 811. The processing device 820 is an example of an information processing device. Some or all of the functions of the image data generation unit 801, the light intensity correction unit 802, the chip data conversion unit 803, and the synchronization signal generation unit 804 may be realized by one or more circuits, such as an ASIC (Application Specific Integrated Circuit) and a PLD (Programmable Logic Device) including an FPGA (Field Programmable Gate Array).

[0043] The image data generation unit 801 performs dithering processing on image data acquired from the scanner unit 100 or from outside the image forming apparatus 10 at a resolution instructed by the CPU 811. In this manner, the image data generation unit 801 generates image data for printing. In this embodiment, the image data generation unit 801 performs dithering processing at a resolution of 1200 dpi in the sub-scanning direction and 4800 dpi in the main scanning direction.

[0044] The light intensity correction unit 802 performs light intensity correction on the dithered image data based on the light intensity correction value acquired from the CPU 811. The light intensity correction unit 802 inserts and extracts image data for each main scanning position within the chip, and corrects variations in the amount of light within the chip.

[0045] The synchronization signal generation unit 804 determines the line boundaries of the image data, generates a line synchronization signal, and supplies it to a line synchronization signal line 808 .

[0046] The chip data conversion unit 803 divides one line of image data for each light-emitting element array chip 400 in synchronization with the line synchronization signal generated by the synchronization signal generation unit 804, and sends it to the printed circuit board 202 together with a clock signal and a chip select signal indicating which light-emitting element array chip 400 will receive which part of the image data.

[0047] The CPU 811 stands for Central Processing Unit and executes various arithmetic processing. The CPU 811 is an example of a first correction means and a second correction means. The CPU 811 generates light intensity correction data from image read values ​​input from the scanner unit 100, and outputs the generated light intensity correction data to the light intensity correction unit 802 and the light-emitting element array chip 400. For example, the CPU 811 generates correction data (first correction data) for correcting the difference in light intensity at the boundary between adjacent light-emitting element array chips 400. The CPU 811 generates correction data (second correction data) for correcting the light intensity distribution of the exposure head in which the difference in light intensity at the boundary has been corrected by the correction data. The light-emitting element array chip 400 sets the setting current of a built-in reference current source according to an instruction from the CPU 811, and controls the overall light intensity of the light-emitting element array chip 400.

[0048] The CPU 811 specifies the time interval of the signal period to the synchronization signal generation unit 804, with one line period being the period during which the surface of the photosensitive drum 102 moves a pixel size of 1200 dpi (approximately 21.2 μm) in the rotation direction at a predetermined rotation speed of the photosensitive drum 102. For example, when printing at a speed of 200 mm / s in the paper transport direction, the CPU 811 specifies a time interval that sets one line period to 105.8 μs (decimals to two decimal places omitted) to the synchronization signal generation unit 804. The CPU 811 calculates the speed in the paper transport direction using a setting value (fixed value) of the print speed set in a speed control unit (not shown) of the photosensitive drum 102.

[0049] Next, a description will be given of the configuration of the printed circuit board 202. The printed circuit board 202 further includes a head information storage unit 810.

[0050] The head information storage unit 810 is a storage device that stores head information such as the light emission amount and mounting position information of each light-emitting element array chip 400. The head information storage unit 810 is connected to a CPU 811 via a communication signal line 809.

[0051] The clock signal line 806, the image data signal line 807, the line synchronization signal line 808, and the communication signal line 809 are connected to all the light-emitting element array chips 400. The chip select signal lines 805 are 17 bus signals that correspond one-to-one to each of the light-emitting element array chips 400-1 to 400-17 and transmit signals. The chip data converter transfers image data to the light-emitting element array chips 400 line by line based on the line synchronization signal. The 17 light-emitting element array chips 400 become able to write data when the chip select signal transmitted from the chip data converter 803 transitions from low to high. The chip data converter 803 sequentially sets the chip select signal to high for each light-emitting element array chip 400 and transfers image data corresponding to each light-emitting element array chip 400, thereby transferring the image data line by line. After receiving the image data, the light-emitting element array chip 400 performs a light-emitting operation according to the image data at the input timing of the next line synchronization signal.

[0052] FIG. 8 is a block diagram of the internal circuit of the light-emitting element array chip 400. The internal circuit of the light-emitting element array chip 400 includes a D / A 901 and reference current sources 902-1 to 902-5. When there is no need to distinguish between the reference current sources 902-1 to 902-5, they are referred to as reference current sources 902. The D / A 901 is a DA converter that generates an analog voltage based on data instructed by the CPU 811. The light-emitting element array chip 400 is divided into multiple blocks in the longitudinal direction, and the analog voltage generated by the D / A 901 is distributed to the reference current sources 902-1 to 902-5 of each block. The reference current source 902 of each block generates a reference current based on the analog voltage and supplies it to the light-emitting elements 903 of the light-emitting element array chip 400. In other words, the current of each light-emitting element 903 is determined by the reference current source 902 of each block. In this embodiment, an example has been given in which the reference current source 902 is divided into five blocks, but the number of blocks may be changed depending on the wiring distance in the longitudinal direction of the chip and the driving capability of the reference current source 902.

[0053] (Light intensity correction unit 802) 9 is a block diagram illustrating the configuration of the light intensity correction unit 802. The light intensity correction unit 802 generates image data for correcting density variations caused by the light intensity correction value AmA, the light intensity correction value AmB, and the spot correction value AmC. The light intensity correction value AmA corresponds to the current variations caused by variations between blocks of the circuit of the light-emitting element array chip 400. The light intensity correction value AmB corresponds to the light intensity variations caused by variations in the luminous efficiency of the lens in the longitudinal direction. The spot correction value AmC corresponds to the density variations caused by variations in the longitudinal direction of the spot. The light intensity correction values ​​AmA, the light intensity correction value AmB, and the spot correction value AmC are set and output by, for example, the CPU 811.

[0054] The light quantity correction unit 802 includes a gradation data unit 1105 , a gradation correction unit 1106 , a subtraction data unit 1107 , an addition data unit 1108 , and an image correction unit 1109 .

[0055] The gradation data unit 1105 acquires image data that has been dithered by the image data generation unit 801. The gradation data unit 1105 reads gradation values ​​from the acquired image data and outputs gradation data to a gradation-by-gradation correction unit 1106.

[0056] The gradation-by-gradation correction unit 1106 acquires the gradation data, spot correction value AmC, and gradation-by-gradation light intensity correction table Tb output by the gradation data unit 1105. The spot correction value AmC is a value for performing processing that corresponds to cases where the spot is partially enlarged in the main scanning direction and the amount of density fluctuation varies for each gradation. In the gradation-by-gradation light intensity correction table Tb, a preset light intensity correction value AmD is associated with the spot correction value AmC and the gradation data of the image data. The gradation-by-gradation correction unit 1106 references the gradation-by-gradation light intensity correction table Tb and extracts the light intensity correction value AmD associated with the acquired spot correction value AmC and gradation data. When increasing the light intensity, the gradation-by-gradation correction unit 1106 outputs the extracted light intensity correction value AmD to the addition data unit 1108. When the light amount is to be reduced, the gradation-by-gradation correction unit 1106 outputs the extracted light amount correction value AmD to the subtraction data unit 1107 .

[0057] The subtraction data unit 1107 calculates subtraction data for reducing the light amount from the light amount correction values ​​AmA, AmB, and AmD, and outputs the calculated data to the image correction unit 1109. The subtraction data unit 1107 may calculate, for example, the total value of the subtractions from the light amount correction values ​​AmA, AmB, and AmD as the subtraction data.

[0058] The added data unit 1108 outputs the acquired added data to the image correction unit 1109 .

[0059] The image correction unit 1109 acquires the subtraction data calculated by the subtraction data unit 1107, the addition data output by the addition data unit 1108, and the image data that has been dithered by the image data generation unit 801. The image correction unit 1109 corrects the image using the subtraction data, addition data, and image data, thereby generating a corrected image (hereinafter also referred to as the corrected image).

[0060] FIG. 10 is a diagram illustrating the process of correcting an image. FIG. 10(a) shows an example of an image before correction (hereinafter, pre-correction image 1001). The pre-correction image 1001 shown in FIG. 10(a) may be a part of the image to be corrected. FIG. 10(b) shows an image to be corrected (hereinafter, correction image 1002). FIG. 10(c) shows a post-correction image 1003.

[0061] The image correction unit 1109 acquires a pre-correction image 1001 of a predetermined image size. The image correction unit 1109 generates a correction image 1002 with a positive or negative sign using the subtraction data and addition data. The image correction unit 1109 then processes the correction image 1002 for the predetermined image size. For example, the image correction unit 1109 calculates a light intensity correction ratio per unit area according to either the acquired subtraction data or addition data, and selects pixels to add or subtract for the predetermined image size. Specifically, when subtracting 4% from the light intensity, the image correction unit 1109 selects four pixels from 10 x 10 pixels (a total of 100 pixels) as shown in the figure as subtraction data. The image correction unit 1109 performs subtraction processing on the luminescent pixels of the pre-correction image 1001 based on the selected four pixels, and generates a corrected image 1003.

[0062] As an example of a method for generating the correction image shown in FIG. 10(b), the image correction unit 1109 may use a threshold matrix table to determine the number and positions of correction pixels corresponding to the correction amount. In the commonly known blue noise mask method, image data is generated using a threshold matrix table with high-frequency spatial frequency characteristics. In this embodiment, the image correction unit 1109 uses the blue noise mask method to generate a spatially high-frequency correction image 1002 and adds or subtracts it from the pre-correction image 1001. The image correction unit 1109 selects pixels to be corrected by determining the correction position according to the correction amount using the threshold matrix table. In this embodiment, the threshold matrix table has a size of 10×10 pixels and stores ON / OFF threshold data for the correction amount. If the correction amount at each pixel position exceeds the threshold of the corresponding pixel in the threshold matrix table, the image correction unit 1109 determines that the correction is ON for that pixel. The image correction unit 1109 corrects the light amount across the entire longitudinal direction by repeatedly performing the above-described 10×10 pixel unit processing in the longitudinal direction. The same settings are used for the threshold matrix table repeatedly, and the image correction unit 1109 sets different correction amounts depending on the position in the longitudinal direction. Through the above operation, the image correction unit 1109 corrects the light amount by an arbitrary correction amount for a predetermined position in the longitudinal direction.

[0063] The image correction unit 1109 can achieve high-precision light intensity correction by setting a correction resolution fine enough relative to the dot size of the pre-correction image 1001. In this embodiment, the image correction unit 1109 performs addition and subtraction on the image at 4800 dpi in the main scanning direction and 2400 dpi in the sub-scanning direction. While the example of the image to be processed is described using 10 x 10 pixels, the image correction unit 1109 may specify insertion and removal points for larger image sizes. When using the blue noise mask method, it is desirable to process at a size of 128 x 128 pixels or 256 x 256 pixels. Increasing the processing image size allows the spatial frequency of the insertion and removal points to be randomly dispersed, preventing the occurrence of moire patterns due to interference between the original image and the insertion and removal pixel period. Furthermore, the processing by the light intensity correction unit 802 is performed before the chip data conversion unit 803. Since the chip data conversion unit 803 divides the image data in the main scanning direction for each light-emitting element array chip 400, it is better for the light intensity correction unit 802 to perform correction processing upstream of the chip data conversion unit 803 in order to perform continuous processing in the main scanning direction.

[0064] (Method for generating light intensity correction data by light measurement) In this embodiment, light intensity correction is performed by adjusting the current for each chip to address variations in light intensity in the longitudinal direction, and light intensity adjustment is performed using image data to address light intensity changes that are smaller than the chip unit. Data for correction can be obtained by measuring during the assembly and adjustment process of the exposure head 106, or by obtaining data within the image forming apparatus 10. Light intensity data measured during the assembly and adjustment process is stored in a head information storage unit 810 within the printed circuit board 202. A CPU 811 reads out the light intensity data from the head information storage unit 810.

[0065] The CPU 811 sets the correction value for each light-emitting element array chip calculated based on the read-out light intensity data in the D / A 901. The CPU 811 sets the light intensity correction value AmA for light intensity variations finer than the width of the light-emitting element array chip in the light intensity correction unit 802. The CPU 811 may also set the light intensity correction value AmB and spot correction value AmC for current variations in the light intensity correction unit 802. As a result, the image correction unit 1109 of the light intensity correction unit 802 corrects the image.

[0066] Among the correction values ​​set by the CPU 811 in the light intensity correction unit 802, the spot correction value AmC is a component that locally changes the image spot. Therefore, under conditions where all light-emitting elements are lit, the spot correction value AmC is not measured as a component of light intensity variation. Therefore, the CPU 811 does not use the locally changing component of the image spot in the process of calculating the setting value of the D / A 901. Under conditions where all light-emitting elements 602 are lit, the CPU 811 measures the light intensity value of each light-emitting element array chip and adjusts the value of the D / A 901 so that the light-emitting element 602 with the lowest light intensity in the light-emitting element array chip 400 reaches a predetermined target light intensity. The subtraction data unit 1107 of the light intensity correction unit 802 determines the light intensity value to be subtracted as the subtraction data. If the correction amount of the image data value is too large, image defects such as distorted dot shapes may occur. Therefore, the CPU 811 determines the magnitude of the subtraction data to be small, for example, to the minimum value. The CPU 811 adjusts the value of the D / A 901 so that the light emitting element 602 with the lowest light intensity in the light emitting element array chip 400 reaches a predetermined target light intensity. As a result, the D / A 901 roughly adjusts the light intensity, and the light intensity correction unit 802 corrects only the component of the light intensity variation within the surface of the light emitting element array chip 400.

[0067] Furthermore, for components of the imaging spot that change locally, the amount of variation can be read by discretely emitting light from the light-emitting element 602. For example, the imaging spot is measured by emitting light from one light-emitting point and reading the imaging spot at the imaging position of the exposure head with a CCD (Charge Coupled Device) camera. In this embodiment, the imaging spot is measured during the assembly process, and the amount of change in the local imaging spot and the generation position are stored in the head information storage unit 810.

[0068] As described above, it is possible to make the light intensity uniform by performing light measurement in the assembly adjustment process. However, it is also possible to adjust the light intensity within the image forming apparatus 10 by reading a printed light intensity correction chart with the scanner unit 100. Hereinafter, a light intensity adjustment method using the scanner unit 100 will be described. The light intensity adjustment method using the scanner unit 100 adjusts the setting value of the D / A 901 based on the result of reading an image with the scanner unit 100 and the result of detecting density differences between the light-emitting element array chips 400. After adjusting the density differences between the light-emitting element array chips 400, the density variation over the entire length of the image is measured, and the CPU 811 sets the density variation as a light intensity correction value AmB, thereby making the image density uniform in the length direction.

[0069] (How to generate light intensity correction data using a light intensity correction chart) <1. Correction chart, light intensity conversion method, and how to check for out-of-focus images> Next, a method for acquiring correction data within the image forming apparatus 10 will be described.

[0070] 11 is a diagram of a light intensity correction chart that is printed to obtain the light intensity variation. The light intensity correction chart is printed when a correction process for adjusting the light intensity variation is instructed via the user interface. The user reads the printed light intensity correction chart with the scanner unit 100, and light intensity correction data is generated within the image forming apparatus 10.

[0071] The light intensity correction chart includes band-shaped images 2101 to 2104 corresponding to four colors Y (yellow), M (magenta), C (cyan), and K (black) arranged in the longitudinal direction, and reference marks 2121 to 2124. The reference marks 2121 to 2124 are arranged corresponding to the images 2101 to 2104, respectively. The reference marks 2121 to 2124 are marks for identifying the position of the light-emitting element array chip 400. Each of the reference marks 2121 to 2124 is printed by emitting light from an edge pixel of the light-emitting element array chip 400. In this embodiment, 17 light-emitting element array chips 400 are arranged, and therefore the reference marks 2121 to 2124 are printed corresponding to 16 locations on the boundary of each light-emitting element array chip 400. The CPU 811 can calculate the boundary position of each light-emitting element array chip 400 by calculating the center of gravity position of the reference marks 2121 to 2124 read by the scanner unit 100, and can accurately calculate the position of the light-emitting element array chip 400 relative to the image even if the light intensity correction chart is misaligned relative to the paper.

[0072] The CPU 811 converts the sensor signal (the brightness signal of the CCD sensor) read by the scanner unit 100 into density information using a predetermined conversion coefficient, and then converts the density information into light intensity information. This conversion process is also referred to as density-light intensity conversion processing. When converting density information into light intensity information, the CPU 811 may use a conversion coefficient determined experimentally in advance. The relationship between density and light intensity may change depending on the temperature and humidity conditions around the image forming apparatus 10. Therefore, the image forming apparatus 10 of this embodiment pre-stores different conversion coefficients depending on the temperature and humidity conditions. This allows the image forming apparatus 10 to calculate light intensity information with high accuracy by using conversion coefficients corresponding to the temperature and humidity conditions. In this case, the image forming apparatus 10 may further include a temperature sensor and a humidity sensor, which detect temperature and humidity information when outputting the light intensity correction chart and use the information for correction.

[0073] If the distance between the exposure head 106 and the photosensitive drum 102 deviates from a predetermined distance, the light collected by the exposure head 106 becomes out of focus, which can result in density abnormalities. In particular, if the distance between the exposure head 106 and the photosensitive drum 102 differs at both ends of the exposure head 106, a large density difference occurs at both ends of the exposure head 106. The density fluctuation caused by focus misalignment varies depending on the image gradation and the size of the printed dots, and may not be fully corrected by light intensity correction. In this embodiment, focus detection marks 2111 to 2118 are printed to detect focus misalignment. The light intensity correction chart has focus detection marks 2111 to 2114 corresponding to colors Y, M, C, and K on the left edge. The light intensity correction chart has focus detection marks 2115 to 2118 corresponding to colors Y, M, C, and K on the right edge. The focus detection marks 2111 to 2118 are images of two intersecting lines extending diagonally. The diagonal lines are sensitive to variations in the light spot size in the main scanning direction and sub-scanning direction, and disappear as the light spot becomes larger. The intersections where the lines intersect are printed darker than the remaining areas. This allows the extent of light spot enlargement to be detected by comparing the image density of the ends of the focus detection marks 2115 to 2118 with the image density of the intersections. In this embodiment, the CPU 811 determines whether the enlargement of the light spot is within an acceptable range based on the results of reading the focus detection marks 2115 to 2118 by the scanner unit 100. If the enlargement is outside the acceptable range, the CPU 811 terminates the series of light intensity adjustment operations and may notify the user of the abnormal condition by means of a visual or audio message.

[0074] <2. Explanation of correction process: After correcting the light intensity difference between chips, long-term variations are corrected> 12 is a flowchart of the correction process for generating correction data for correcting the amount of light. When the user issues an instruction to start the process of correcting density variations via a user interface such as a touch panel, the CPU 811 starts the correction process.

[0075] In S2201, the CPU 811 prints and outputs the light intensity correction chart shown in FIG. 11, and the process proceeds to S2202.

[0076] In S2202, the CPU 811 receives an instruction to start scanning and determines whether or not to start scanning. For example, a user places the output light intensity correction chart in the scanner unit 100 and issues an instruction to start scanning via a user interface. When the CPU 811 receives an instruction to start scanning from the user, it determines that scanning has started and proceeds to S2203. Note that the CPU 811 waits until it determines that scanning has started.

[0077] In S2203, the CPU 811 scans the light intensity correction chart, obtains light intensity information from the read result of the light intensity correction chart, and calculates the light intensity. The process proceeds to S2204. The light intensity information may be information on the light intensity or density for calculating the light intensity. Specific calculations of the light intensity will be described later.

[0078] In S2204, the CPU 811 calculates the difference in light intensity at the boundary between the light-emitting element array chips 400, calculates correction data (an example of first correction data) for correcting the difference in light intensity, and corrects the difference in light intensity between the light-emitting element array chips 400 by setting the D / A 901 that supplies the drive current to each light-emitting element array chip 400.

[0079] FIG. 13 is a diagram showing the light intensity distribution of the exposure head 106 before correction in the longitudinal direction of the light-emitting element array chip 400. FIG. 14 is a diagram showing the light intensity distribution of the exposure head 106 after correction in the longitudinal direction of the light-emitting element array chip 400. The vertical axis in FIGS. 13 and 14 indicates the light intensity of the light-emitting element array chip 400. The horizontal axis in FIGS. 13 and 14 indicates the position in the longitudinal direction of the light-emitting element array chip 400. Therefore, FIGS. 13 and 14 show the light intensity distribution at each position on the light-emitting element array chip 400. The dashed lines in FIGS. 13 and 14 indicate the boundaries between adjacent light-emitting element array chips 400. Therefore, the space between the dashed lines indicates one light-emitting element array chip 400. Note that the correction referred to in FIGS. 13 and 14 refers to the correction of the difference in light intensity at the boundaries of the light-emitting element array chips 400.

[0080] In this embodiment, the exposure head 106 has 17 light-emitting element array chips 400, so light intensity distributions for 17 chips are acquired. However, for simplicity, FIG. 13 shows the light intensity distribution for the central 7 chips. In the light intensity distribution before correction shown in FIG. 13, a steep difference in light intensity occurs at the boundaries of the light-emitting element array chips 400, indicated by the dashed lines. In S2204, the CPU 811 generates correction data to reduce the difference in light intensity between the light-emitting element array chips 400, and corrects the light intensity. As a result, in the light intensity distribution after correction shown in FIG. 14, the steep difference in light intensity at the boundaries of the light-emitting element array chips 400, indicated by the dashed lines, is corrected, the step at the boundary is reduced, and the boundary is smoothed.

[0081] The following steps S2205 to S2207 are the same as steps S2201 to S2203, and will therefore be explained in a simplified manner.

[0082] 11, and proceeds to S2206. Here, the CPU 811 corrects the light intensity of the light-emitting element array chip 400 using the correction data calculated in S2204, and prints the light intensity correction chart in a state where the difference in light intensity at the boundary is reduced.

[0083] In S2206, the CPU 811 waits until it receives an instruction to start scanning from the user. When the CPU 811 receives an instruction to start scanning from the user, it determines that scanning should be started and proceeds to S2207.

[0084] In S2207, the CPU 811 scans the light intensity correction chart, acquires light intensity information from the read result of the light intensity correction chart, and proceeds to S2208. Here, the CPU 811 acquires the light intensity information by scanning the light intensity correction chart that has been printed after the light intensities of the light-emitting element array chips 400 have been corrected based on the correction data generated in S2204. Therefore, the light intensity information acquired by the CPU 811 has a gentle light intensity distribution without steps at the boundaries of the light-emitting element array chips 400, as shown in FIG.

[0085] In S2208, the CPU 811 calculates and sets correction data (an example of second correction data) for correcting the light intensity distribution of a plurality of sample areas predetermined in the light-emitting element array chip 400, based on the light intensity information. The light intensity distribution to be corrected is the light intensity distribution across the plurality of light-emitting element array chips 400. The light intensity distribution to be corrected here is the light intensity distribution across all the light-emitting element array chips 400, in other words, the overall light intensity distribution of the exposure head 106. The CPU 811 sets the correction data for the light intensity distribution as correction data for the light intensity correction value AmB that corrects the light intensity variation.

[0086] As described above, in this embodiment, after correcting the difference in light quantity at the boundaries between the light-emitting element array chips 400, the overall light quantity distribution of the exposure head 106 is corrected based on the light quantity correction chart printed based on this correction. The CPU 811 corrects gentle fluctuations by correcting the overall light quantity distribution of the exposure head 106, making the light quantity distribution approach flatness. For example, the CPU 811 generates correction data approximating the overall light quantity distribution of the exposure head 106 with a quadratic function or the like. The quadratic function mentioned here is, for example, a function showing the relationship between the position in the longitudinal direction of the exposure head 106 and the light quantity at that position. In this embodiment, first, by correcting the sharp difference in light quantity at the boundaries between the light-emitting element array chips 400, the approximation accuracy when approximating the light quantity distribution can be improved.

[0087] <Method of Averaging in Sub-Scanning Direction for Obtaining In-Chip Light Quantity Information in S2203> FIG. 15 is a diagram of the light quantity distribution before correction within the light-emitting element array chip 400 acquired in S2203. In this embodiment, the scanner unit 100 scans a light quantity correction chart that is a two-dimensional strip-shaped image, and the CPU 811 calculates one-dimensional light quantity information corresponding to the position in the longitudinal direction within the exposure head 106 from the two-dimensional light quantity correction chart.

[0088] FIG. 16 is a diagram for explaining the sample area and dot influence for each light-emitting element array chip 400. FIG. 16(a) is a diagram of two-dimensional image information corresponding to one acquired light-emitting element array chip 400 by the scanner unit 100. In this embodiment, the image area corresponding to one light-emitting element array chip 400 is divided in two directions: the longitudinal direction of the exposure head 106 and the direction (hereinafter referred to as the orthogonal direction) intersecting (here, perpendicular) with the longitudinal direction of the exposure head 106. As a result, the image area is divided into sample areas arranged two-dimensionally. Specifically, the image area is divided into 18 sample areas in the longitudinal direction of the exposure head 106 and 12 sample areas in the orthogonal direction. The orthogonal direction is an example of an intersecting direction. When the average density of each sample area is detected, the CPU 811 converts the light quantity for each sample area from the average density by the above-described density-light quantity conversion process.

[0089] Through the following process, the CPU 811 calculates the light amounts of the columns of 18 sample areas arranged in the longitudinal direction of the exposure head 106. The sample area columns are columns extending in the orthogonal direction. The CPU 811 deletes at least the sample areas with the maximum value and the minimum value (here, the values of light amount or density) among the 12 sample areas arranged in the orthogonal direction. In the present embodiment, the CPU 811 deletes the sample areas with the first and second largest values and the first and second smallest values of light amount or density among the 12 sample areas arranged in the orthogonal direction. The CPU 811 calculates the average value of the light amount of each of the 18 sample areas in the longitudinal direction as the light amount of the sample areas in the longitudinal direction based on the remaining 8 sample areas in the orthogonal direction that were not excluded among the 12 sample areas arranged in the orthogonal direction of the exposure head 106. For example, the CPU 811 performs an average process on the data of 8 sample areas excluding the two with the largest magnitudes and the two with the smallest magnitudes among the data of the light amounts of the 12 sample areas p1-1 to p1-12, and calculates the average value as the light amount of the sample areas of the sample area column p1. Note that the CPU 811 may calculate the average of the density first and then calculate the light amount instead of the light amount.

[0090] FIG. 16(b) shows a state in which the dot Dt is printed unintentionally due to factors such as dirt on the light amount correction chart. In cases where extra dots Dt are printed on the chart and cases where the image is white and missing, an error occurs in the calculation result of the light amount. Therefore, as described above, the CPU 811 excludes the top two and bottom two in terms of the magnitude of the light amount (or density) in the sample area column in the orthogonal direction including 12 sample areas, so that even if an unintended dot Dt is printed, the occurrence of a detection error in the light amount can be suppressed.

[0091] <S2204 First Inter-chip Light Amount Difference Calculation Method Measures for Density Variation and Streaks> 17 is a diagram showing the light intensity distribution of 18 sample area rows corresponding to one light-emitting element array chip 400. The sample area rows here are rows of sample areas extending in orthogonal directions. For example, sample area row p1 is a row of sample areas including sample area p1-1 to sample area p1-12.

[0092] The CPU 811 calculates the light intensities at the left and right ends of each light-emitting element array chip 400 for the 18 sample area columns p1 to p18 in the light-emitting element array chip 400 calculated in S2203. Because the outermost sample area columns p1 and p18 may detect the density of an image printed by an adjacent light-emitting element array chip 400, the CPU 811 excludes the sample area columns p1 and p18 from the calculation of the light intensities of the sample area columns p1 and p18. In other words, the CPU 811 calculates the light intensities of the left and right end sample area columns p1 and p18 using the second and subsequent sample area columns p2, p3,... or sample area columns p17, p16,... Here, the CPU 811 calculates the light intensities of the left and right end sample area columns p1 and p18 using the three left and right end sample area columns excluding the outermost left and right sample area columns p1 and p18. Specifically, the CPU 811 calculates the light intensity of the leftmost sample area column p1 using the three leftmost sample area columns p2 to p4, excluding the sample area column p1 of the light-emitting element array chip 400. The CPU 811 calculates the light intensity of the rightmost sample area column p18 using the data of the rightmost sample area columns p17 to p15, excluding the sample area column p18 of the light-emitting element array chip 400. As a calculation method, the CPU 811 may calculate the light intensity of the sample area columns at both the left and right ends of the light-emitting element array chip 400 by performing an approximation calculation using a method such as the least squares method from the three sample area columns. By using a linear function or a quadratic function as an approximation formula, the CPU 811 can accurately calculate the light intensity of the left and right ends even if there is a density difference within the light-emitting element array chip 400 due to long-period density variations.

[0093] Here, the image printed by the image forming apparatus 10 may include vertical streaks due to various factors within the apparatus. FIG. 18 is a diagram showing the light amount distribution in a case where vertical streaks occur in the image. In this example, the sample area columns p15 and p16 obtain a higher light amount than the surrounding sample area columns. When the CPU 811 calculates the light amount at the right end of the light emitting element array chip 400 using the sample area columns p15 and p16, the error in the light amount becomes large. Therefore, in such a case, the CPU 811 derives an approximation formula from the sample area columns p17, p14, and p13 excluding the sample area columns p15 and p16 among the sample area columns starting from the second column from the end. As a method of exclusion, the CPU 811 calculates an approximation formula by the least squares method for the light amounts of the sample area columns p2 to p17, and excludes the sample area columns with a light amount exceeding a predetermined allowable range of ±δA (the range of limit1 and limit2 in the figure). Further, the CPU 811 newly sets the same number of sample area columns as the excluded sample area columns in the central direction of the light emitting element array chip 400 from the excluded sample area columns (sample area columns p13 and p14 in FIG. 18). Therefore, the CPU 811 extracts the sample area columns with a light amount within the allowable range of ±δA among the sample area columns starting from the second column from the end (here, the right end) in the order closest to the end, and calculates the light amount of the sample area column p18 at the end.

[0094] <S2204 Second method for calculating the light amount difference between chips Align the left and right with the center of the exposure head fixed> In this embodiment, the CPU 811 determines the drive current value of each light-emitting element array chip 400 using the light intensity at both ends of each light-emitting element array chip 400 calculated by the above-mentioned process so as to reduce the difference in light intensity between each light-emitting element array chip 400. If the adjustment amount of the drive current between each light-emitting element array chip 400 becomes too large, the density of the entire image may fluctuate (become too dark or too light). Therefore, in order to minimize the adjustment amount of the drive current, the CPU 811 determines the light intensity correction value of each light-emitting element array chip 400 so as to correct the difference in light intensity between the left and right light-emitting chips using the center chip of the exposure head 106 as a reference.

[0095] FIG. 19 is a plan view showing an arrangement of light-emitting element array chips 400. Referring to FIG. 19, correction of the light intensity at the boundary between adjacent light-emitting element array chips 400 will be described. FIG. 19(a) shows areas for calculating the light intensity of the seven central light-emitting element array chips 400. First, the CPU 811 derives the light intensity at the left and right ends of the central light-emitting element array chip 400 from the light intensity (or density) of area D9_L and area D9_R. The CPU 811 may calculate the light intensity by calculating the 18 sample area rows of the light-emitting element array chip 400 described above.

[0096] The CPU 811 corrects the set light intensity of the light-emitting element array chip 400-8 based on the difference between the light intensity of the area D9_L at the left end of the light-emitting element array chip 400-9 and the light intensity of the area D8_R at the right end of the light-emitting element array chip 400-8. For example, the CPU 811 may add or subtract this difference from the set light intensity of the light-emitting element array chip 400-8 to obtain the corrected set light intensity. Here, the relationship between the light intensity and the drive current is converted using a predetermined conversion coefficient. As described above, the CPU 811 overwrites the set value of the D / A 901 of the light-emitting chip 8 with the calculated drive current to control the light intensity.

[0097] Similarly, the CPU 811 calculates the light intensity of the light-emitting element array chip 400-10 by adding or subtracting the difference between the light intensity of the area D9_R at the right end of the light-emitting element array chip 400-9 and the light intensity of the area D10_L at the left end of the light-emitting element array chip 400-10 to the set light intensity of the light-emitting element array chip 400-10 before correction.

[0098] 19(b) is a diagram illustrating the light amounts of the light-emitting element array chips 400 other than those on both sides of the central light-emitting element array chip 400-9. Areas D7_R, D8_L, D10_R, and D11_L are areas for calculating the difference in light amount to correct the light amount of the light-emitting element array chip 400-7 and the light-emitting element array chip 400-11.

[0099] The CPU 811 sequentially calculates the difference in light intensity between the light emitting element array chip 400-8 and the light emitting element array chip 400-10 based on the difference in light intensity between the end areas. The CPU 811 corrects the light intensity of the light emitting element array chip 400-7 based on the difference in light intensity between the areas D7_R and D8_L. The CPU 811 corrects the light intensity of the light emitting element array chip 400-11 based on the difference in light intensity between the areas D10_R and D11_L. The CPU 811 performs similar processing to sequentially calculate the light intensity of the light emitting element array chips 400 along the left-right direction using the light emitting element array chip 400-9 at the center of the exposure head 106, and corrects the light intensities of the light emitting element array chips 400-1 to 400-17.

[0100] 20 is a block diagram showing the hardware configuration of the processing device 820. The processing device 820 is, for example, a computer. The processing device 820 has a processor 2001, a memory 2002, a storage 2003, a communication IF 2004, an input IF 2005, an output IF 2006, and a bus 2007. The processor 2001, the memory 2002, the storage 2003, the communication IF 2004, the input IF 2005, and the output IF 2006 are connected via the bus 2007 so as to be able to input and output data to and from each other.

[0101] The processor 2001 includes a CPU 811. The processing device 820 may have other processors such as an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), and a QPU (Quantum Processing Unit) instead of or in addition to the CPU 811. The processor 2001 may function as a first correction means and a second correction means by executing a program.

[0102] Some or all of the functions of the image data generation unit 801, light intensity correction unit 802, chip data conversion unit 803, and synchronization signal generation unit 804 may be realized by one or more processors 2001 including a CPU 811 reading out a program stored in storage 2003, expanding it in memory 2002, and executing it.

[0103] The memory 2002 is a storage device that can be read and written at high speed. The memory 2002 may be, for example, a random access memory (RAM). The memory 2002 functions as a work area when the processor 2001 executes a program.

[0104] The storage 2003 is a nonvolatile large-capacity storage device. The storage 2003 may be, for example, a read-only memory (ROM), a hard disk drive (HDD), or a solid state drive (SSD). The storage 2003 stores programs such as correction processes executed by the processor 2001, parameters required for executing the programs, image data to be processed by the programs, and the like.

[0105] The communication IF 2004 is an interface for connecting to an external network, and may be an interface for wireless communication or an interface for wired communication, but is not particularly limited thereto.

[0106] The input IF 2005 is an interface connected to an input device, such as a user interface, a mouse, a keyboard, a touchpad, or the scanner unit 100. The input IF 2005 outputs user instructions and the like input from the input device to the processor 2001.

[0107] The output IF 2006 is an interface connected to an output device, such as an image display device, and outputs data, such as image data, acquired from the CPU 811 of the processor 2001 to the output device.

[0108] As described above, the image forming apparatus 10 of the embodiment generates correction data for correcting the sharp difference in light intensity at the boundary between adjacent light-emitting element array chips 400, and corrects the light intensity distribution of the exposure head 106 in which the difference in light intensity at the boundary (step in light intensity) has been corrected using the correction data. As a result, the embodiment can improve the accuracy of correction and the image quality after correction compared to when the light intensity distribution of the exposure head 106 is corrected while leaving the sharp difference in light intensity at the boundary.

[0109] In this embodiment, when calculating the light intensity of a sample area row, the average light intensity, excluding at least the maximum and minimum light intensity values ​​of the sample area row, is calculated as the light intensity of the sample area row. This makes it possible to remove outliers in the light intensity due to noise, etc., and improves the accuracy of calculation of the light intensity of the sample area row.

[0110] In this embodiment, the light intensity of the sample area row at the end of the light-emitting element array chip 400 is calculated based on the light intensity of the sample area row from the second row onward from the end. This makes it possible to improve the accuracy of calculating the light intensity of the sample area row at the end that is easily affected by the adjacent light-emitting element array chip 400.

[0111] In this embodiment, the light intensity of the end portion is calculated based on the light intensity of the sample area rows whose light intensity is within a predetermined allowable range among the second and subsequent sample area rows at the end portion of the light-emitting element array chip 400. This makes it possible to remove outliers in the light intensity due to noise, etc., and improve the accuracy of the calculation of the light intensity of the sample area rows at the end portion.

[0112] In this embodiment, in the direction in which the plurality of light-emitting element array chips 400 are arranged, the light intensity is corrected in order from the central light-emitting element array chip 400 to the end light-emitting element array chips 400. As a result, in this embodiment, the difference in light intensity before and after correction can be made smaller than when correction is made from the end light-emitting element array chips 400, and the difference in the image before and after correction can be made smaller.

[0113] In this embodiment, a quadratic function that flattens the overall light intensity distribution according to the position of the exposure head 106 is generated as correction data, so the volume of correction data can be reduced.

[0114] In this embodiment, correction data is generated by scanning a light intensity correction chart printed with the same image data for both boundary correction and overall correction of the light intensity distribution of the exposure head 106. This makes it possible to reduce the volume of image data.

[0115] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0116] The disclosure of this specification includes the following information processing device, image forming device, control method, and program. (Item 1) 1. An information processing device that generates correction data for correcting the amount of light of an image forming device having an exposure head including a plurality of light emitting element array chips each having a plurality of light emitting elements, a first correction means for generating first correction data for correcting a difference in light intensity at a boundary between adjacent light emitting element array chips; a second correction means for generating second correction data for correcting the light quantity distribution of the exposure head corrected by the first correction data; An information processing device comprising: (Item 2) The first correction means generates the first correction data so as to reduce a difference in light intensity at a boundary between adjacent light-emitting element array chips among the plurality of light-emitting element array chips. 2. The information processing device according to item 1, (Item 3) The first correction means calculates the light amount difference based on data on the amount of light acquired by scanning a first image for correction, and generates the first correction data. Item 1 or 2. The information processing device according to item 1 or 2. (Item 4) The first correction means calculating light intensities of a plurality of sample areas obtained by two-dimensionally dividing an image area of ​​the light-emitting element array chip along a plurality of rows along the direction in which the plurality of light-emitting element array chips are arranged and a plurality of columns intersecting the rows; calculating an average value of the light amounts excluding at least the maximum and minimum values ​​of each of the rows of sample areas as the light amounts of the rows of the plurality of sample areas; Calculating the first correction data based on the amount of light. 4. The information processing device according to any one of items 1 to 3. (Item 5) The first correction means calculates the light intensity of a row including the plurality of sample areas at an end facing the boundary of the light-emitting element array chip based on the light intensity of rows including the plurality of sample areas from the end to the second row onward. 5. The information processing device according to item 4. (Item 6) The first correction means calculates the light intensity of the row of sample areas at the end based on the light intensity of the row of sample areas whose light intensity is within a predetermined allowable range, among the rows of sample areas from the second row onward from the end. 6. The information processing device according to item 5, (Item 7) The first correcting means corrects the light amount in the direction in which the plurality of light emitting element array chips are arranged, starting from the central light emitting element array chip to the end light emitting element array chips. 7. The information processing device according to any one of items 1 to 6, (Item 8) The second correction means generates the second correction data so as to make the overall light quantity distribution according to the position on the exposure head closer to flat. 8. The information processing device according to any one of items 1 to 7, (Item 9) The second correction means generates, as the second correction data, a quadratic function that makes the light quantity distribution closer to flat. 9. The information processing device according to item 8, (Item 10) The second correction means generates the second correction data based on the amount of light acquired by scanning a second image obtained by printing the same image data as the first image based on the first correction data. 4. The information processing device according to item 3, (Item 11) the information processing device according to item 1; the exposure head controlled by the information processing device; a photosensitive drum on which an electrostatic latent image is formed by the exposure head; An image forming apparatus having the same. (Item 12) 1. A control method for generating correction data for correcting a light amount of an image forming apparatus having an exposure head including a plurality of light emitting element array chips each including a plurality of light emitting elements, the method comprising: a first correction step of generating first correction data for correcting a difference in light intensity at a boundary between adjacent light emitting element array chips; a second correction step of generating second correction data for correcting the light quantity distribution of the exposure head corrected by the first correction data; A control method comprising: (Item 13) A program for causing a computer to function as each means of the information processing device according to any one of items 1 to 10.

[0117] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0118] 10 Image forming apparatus, 102 Photosensitive drum, 106 Exposure head, 400 Light emitting element array chip, 602, 903 Light emitting element, 604 Light emitting element row, 606 Light spot, 800 Image controller unit, 820 Processing device, 811 CPU, 1 Processor, 2101, 2104 Image, p1-p18 Sample area row.

Claims

1. 1. An information processing device that generates correction data for correcting the amount of light of an image forming device having an exposure head including a plurality of light emitting element array chips each having a plurality of light emitting elements, a first correction means for generating first correction data for correcting a difference in light intensity at a boundary between adjacent light emitting element array chips; a second correction means for generating second correction data for correcting the light quantity distribution of the exposure head corrected by the first correction data; An information processing device comprising:

2. The first correction means generates the first correction data so as to reduce a difference in light intensity at a boundary between adjacent light-emitting element array chips among the plurality of light-emitting element array chips.

2. The information processing apparatus according to claim 1, wherein:

3. The first correction means calculates the light amount difference based on data on the amount of light acquired by scanning a first image for correction, and generates the first correction data. The information processing device according to claim 1 .

4. The first correction means calculating light intensities of a plurality of sample areas obtained by two-dimensionally dividing an image area of ​​the light-emitting element array chip along a plurality of rows along the direction in which the plurality of light-emitting element array chips are arranged and a plurality of columns intersecting the rows; calculating an average value of the light amounts excluding at least the maximum and minimum values ​​of each of the rows of sample areas as the light amounts of the rows of the plurality of sample areas; The first correction data is calculated based on the amount of light.

2. The information processing apparatus according to claim 1, wherein:

5. The first correction means calculates the light intensity of a row including the plurality of sample areas at an end facing the boundary of the light-emitting element array chip based on the light intensity of rows including the plurality of sample areas from the end to the second row onward.

5. The information processing apparatus according to claim 4,

6. The first correction means calculates the light intensity of the row of sample areas at the end based on the light intensity of the row of sample areas whose light intensity is within a predetermined allowable range, among the rows of sample areas from the second row onward from the end.

6. The information processing apparatus according to claim 5,

7. The first correcting means corrects the light amount in the direction in which the plurality of light emitting element array chips are arranged, starting from the central light emitting element array chip to the end light emitting element array chips.

2. The information processing apparatus according to claim 1, wherein:

8. The second correction means generates the second correction data so as to make the overall light quantity distribution according to the position on the exposure head closer to flat.

2. The information processing apparatus according to claim 1, wherein:

9. The second correction means generates, as the second correction data, a quadratic function that makes the light quantity distribution closer to flat.

9. The information processing apparatus according to claim 8,

10. The second correction means generates the second correction data based on the amount of light acquired by scanning a second image obtained by printing the same image data as the first image based on the first correction data.

4. The information processing apparatus according to claim 3,

11. The information processing device according to claim 1 ; the exposure head controlled by the information processing device; a photosensitive drum on which an electrostatic latent image is formed by the exposure head; An image forming apparatus having the same.

12. 1. A control method for generating correction data for correcting a light amount of an image forming apparatus having an exposure head including a plurality of light emitting element array chips each including a plurality of light emitting elements, the method comprising: a first correction step of generating first correction data for correcting a difference in light intensity at a boundary between adjacent light-emitting element array chips; a second correction step of generating second correction data for correcting the light quantity distribution of the exposure head corrected using the first correction data; A control method comprising:

13. A program for causing a computer to function as each of the means of the information processing device according to any one of claims 1 to 10.

Images