Optical writing device and image forming device

Abstract

To provide an optical writing device and an image forming device which eliminate the problem of image quality deterioration when reused, without requiring a dustproof room or dedicated adjustment equipment. [Solution] An optical writing device 6 comprises a light beam generating means 60 that emits a light beam and an optical scanning means 62 that reflects the light beam emitted from the light beam generating means 60 and scans in a one-dimensional direction, and the light intensity of the light beam is variably controlled within the one-dimensional scan by the optical scanning means 62 based on a light intensity unevenness correction value, and the light intensity unevenness correction value when the optical writing device 6 is reused is determined from the unique information of the optical writing device 6 and the usage information of the optical writing device.

Description

[Technical Field]

[0001] The present invention relates to an optical writing device used to write image data onto a photosensitive member in an image forming apparatus or the like, and to an image forming apparatus equipped with this optical writing device. [Background technology]

[0002] Refurbishment efforts are being made to refurbish used parts for image forming devices and other equipment, and the application of a certification label to certified refurbished products is also being considered.

[0003] When reusing the optical writing device described above used in an image forming apparatus, image quality degradation due to contamination of the light-reflecting surface of the polygon mirror becomes a problem. The polygon mirror functions as an optical scanning means that reflects a light beam emitted from a light beam generating means such as a laser diode and scans in one direction.

[0004] When refurbishing an optical writing device, it is also possible to replace a dirty polygon mirror.

[0005] Furthermore, Patent Document 1 proposes an image forming apparatus that is capable of predicting the remaining time until the polygon mirror becomes unusable due to contamination. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-184806 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when refurbishing an optical writing device, the method of replacing a dirty polygon mirror has the following problems.

[0008] That is, because it is necessary to open the dustproof optical writing device unit, there is a problem that the work must be done in a place with dustproof facilities such as a dustproof room. Also, if the positions of optical components such as the polygon mirror and optical sensor change when replacing parts of the optical writing device, the irradiation position of the light beam on the photosensitive element changes. This requires adjustment of the beam position, which is another problem that requires the work to be done in a place with dedicated adjustment facilities.

[0009] Furthermore, while the technology described in Patent Document 1 makes it possible to predict the remaining time until the polygon mirror becomes unusable due to dirt, it does not disclose any information about image quality degradation when the optical writing device is reused as a refurbished product or any countermeasures for this.

[0010] An object of the present invention is to provide an optical writing device and an image forming device which do not require a dustproof room or dedicated adjustment equipment and which solve the problem of image quality degradation when reused. [Means for solving the problem]

[0011] The above object can be achieved by the following means. (1) a light beam generating means for emitting a light beam; an optical scanning means for reflecting the light beam emitted from the light beam generating means and scanning in a one-dimensional direction; Equipped with an optical writing device in which the light amount of the light beam is variably controlled within one-dimensional scanning by the optical scanning means based on a light amount unevenness correction value, The optical writing device according to claim 1, wherein the light amount unevenness correction value when the optical writing device is reused is determined based on unique information of the optical writing device and usage information of the optical writing device. (2) at least one synchronization detection sensor for detecting a constant timing when the optical scanning means scans the light beam; 2. The optical writing device according to claim 1, wherein the usage information is determined from an output of the at least one synchronization detection sensor. (3) The optical writing device according to the above paragraph 2, wherein the synchronization detection sensors are plural, and the usage information is determined from outputs of the plural synchronization detection sensors. (4) The optical writing device according to the above item 2 or 3, wherein the usage information is an output value of an analog voltage output from the synchronization detection sensor. (5) The optical writing device according to the preceding paragraph 4, wherein the usage information is an output width of the analog voltage. (6) The optical writing device according to the preceding paragraph 1, wherein the usage information is the number of sheets on which an image written by the optical writing device is printed. (7) The optical writing device according to the preceding paragraph 1, wherein the usage information is an operating time of the optical writing device. (8) The optical writing device according to any one of the above items 1 to 3, 6 or 7, wherein the light amount unevenness correction value is stored in a memory. (9) The optical writing device according to any one of the above items 1 to 3, 6 or 7, wherein the light intensity unevenness correction value when the optical writing device is reused is determined and updated from the unique information and the usage information. (10) one or more photoreceptors; an optical writing device according to any one of items 1 to 3, 6 or 7, for irradiating a light beam to write image data onto the photosensitive member; a light amount control means for variably controlling the light amount of the light beam within one-dimensional scanning by the optical scanning means based on the light amount unevenness correction value; An image forming apparatus comprising: [Effects of the Invention]

[0012] In the optical writing device and image forming apparatus according to the present invention, the light intensity of the light beam is variably controlled within one-dimensional scanning by the optical scanning means of the optical writing device based on the light intensity unevenness correction value. The light intensity unevenness correction value when the optical writing device is reused is determined from the unique information of the optical writing device and the usage information of the optical writing device.

[0013] Therefore, when the optical writing device is reused, the light intensity of the light beam is controlled within one-dimensional scanning in the optical writing device based on the correction value determined from the unique information of the optical writing device and the usage information of the optical writing device. As a result, degradation of image quality caused by dirt on the polygon mirror can be corrected with high precision, and the optical writing device can be reused as a refurbished product without any problems.

[0014] Moreover, since there is no need to replace a dirty polygon mirror, a dustproof room or dedicated adjustment equipment is not required, and the optical writing device can be made to solve the problem of image quality degradation when reused. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing an outline of the configuration of an image forming apparatus equipped with an optical writing device according to an embodiment of the present invention; [Figure 2] FIG. 2A shows the configuration of the print head as seen from the front side, and FIG. 2B shows the configuration as seen from above. [Figure 3] FIG. 2 is a circuit diagram of an optical sensor. [Figure 4] Images 4A and 4B are diagrams for explaining why correction of uneven light quantity based on print head specific information is necessary. [Figure 5] 5A and 5B are explanatory diagrams of the correction of uneven light amount based on the unique information of the print head. [Figure 6] 10A and 10B are diagrams for explaining the tendency of contamination of a polygon mirror. [Figure 7] 7A and 7B are diagrams for explaining why it is necessary to correct the unevenness in the amount of light based on the usage information of the print head. [Figure 8] 8A and 8B are explanatory diagrams of the correction of uneven light amount based on print head usage information. [Figure 9] 9A and 9B are diagrams for explaining a method for determining a correction value magnification based on print head usage information using an optical sensor. [Figure 10]10A and 10B are tables showing examples of the relationship between the magnitude of the optical detection signal value of the optical sensor and the correction value magnification, respectively. [Figure 11] 10 is a table illustrating correction values ​​for uneven light intensity determined for a print head when it is reused. [Figure 12] 10 is a correspondence table showing the number of printed sheets and the correction value magnification when the correction value magnification is determined based on the number of printed sheets. [Figure 13] 10 is a correspondence table between operation time and correction value magnification when the correction value magnification is determined based on the operation time of the print head. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] 1 shows an outline of the configuration of an image forming apparatus 1 equipped with an optical writing device according to one embodiment of the present invention. The image forming apparatus 1 is an MFP (Multi-functional Peripheral) that combines the functions of a copier, printer, facsimile machine, image reader, etc.

[0018] The image forming apparatus 1 includes an automatic document feeder (ADF) 1A, a flatbed scanner 1B, an electrophotographic color printer 1C, a sheet cabinet 1D, and an operation panel 1E.

[0019] Automatic document feeder 1A transports documents (sheets) set on a document tray to the reading position of scanner 1B. Scanner 1B reads images from sheet-like documents transported from automatic document feeder 1A or from various documents set on the platen glass, and generates image data.

[0020] In print jobs such as copying, network printing (PC printing), facsimile reception, and box printing, color printer 1C forms color or monochrome images on one or both sides of recording sheets (paper) P. For example, in a copy job, an image is formed based on image data generated by scanner 1B.

[0021] The color printer 1C is equipped with a tandem printer engine 2. The printer engine 2 has four imaging units 3y, 3m, 3c, and 3k, a print head 6, an intermediate transfer belt 10, and the like.

[0022] Each of the imaging units 3y to 3k includes a cylindrical photosensitive member 4, a charging roller 5, a developing device 7, and a cleaner 8. The imaging units 3y to 3k have the same basic configuration.

[0023] The print head 6 corresponds to an optical writing device and emits a laser beam LB as a light beam for performing pattern exposure on each of the imaging units 3y to 3k. In the print head 6, a main scan is performed in which the laser beam LB is deflected in a direction parallel to the rotation axis of the photosensitive member 4. In parallel with this main scan, a sub scan is performed in which the photosensitive member 4 rotates at a constant speed.

[0024] The intermediate transfer belt 10 is a member to which a toner image is transferred during the primary transfer, and is wound around a pair of rollers and rotates. Primary transfer rollers 11 are disposed inside the intermediate transfer belt 10 for each of the imaging units 3y, 3m, 3c, and 3k.

[0025] The sheet cabinet 1D is a three-tiered drawer type equipped with paper feed trays 12a, 12b, and 12c. The sheet cabinet 1D takes out sheets P from one of the paper feed trays selected according to the job specifications and supplies them to the color printer 1C above.

[0026] The operation panel 1E has a touch panel display that displays a screen for user operation, and outputs signals in response to input operations. In response to these signals, the control circuit 100 controls the operation of the image forming apparatus 1.

[0027] The control circuit 100 comprehensively controls the entire image forming apparatus 1. As an example of control, the control unit 100 executes operations such as copying, printing, and document scanning. Furthermore, the control unit 100 controls the light intensity of the laser beam LB emitted from the print head 6. Although not shown, the control circuit 100 includes a CPU, ROM, RAM, a storage unit, etc.

[0028] In color printing mode, imaging units 3y to 3k form toner images of four colors, Y (yellow), M (magenta), C (cyan), and K (black), in parallel. The four color toner images are sequentially transferred (primary transfer) onto the rotating intermediate transfer belt 10. The Y toner image is transferred first, and then the M toner image, C toner image, and K toner image are sequentially transferred so as to be superimposed on it.

[0029] When the sheet P faces the secondary transfer roller 16, the toner image that has been primarily transferred is secondarily transferred onto the sheet P that has been transported from the sheet cabinet 1D via the timing roller 15. After the secondary transfer, the sheet P passes through the fixing device 17 and the connecting transport path 19 in that order, and is sent to the finisher. If the image forming apparatus 1 is not connected to a finisher, the sheet P is discharged to a paper output tray 19 instead of the connecting transport path 19. As the sheet P passes through the fixing device 17, the toner image is fixed to the sheet P by heat and pressure.

[0030] 2A and 2B show the configuration of the print head 6. In detail, Fig. 2A shows the configuration as seen from the front side, and Fig. 2B shows the configuration as seen from above.

[0031] As shown in FIGS. 2A and 2B, the print head 6 has a light source unit 60, a polygon unit 61, an fθ lens 67, reflecting mirrors 68 to 79, and two optical sensors 80 and 81.

[0032] The light source unit 60 is a means for emitting a laser beam LB for exposure according to a latent image to each of the four photosensitive elements 4 provided in each of the imaging units 3y to 3k. In the light source unit 60, a set of a laser light source, a collimator lens, and a mirror is provided for each of the imaging units 3y to 3k. The laser light source is, for example, a semiconductor laser (laser diode) equipped with a photodiode for monitoring the light emission. The four laser beams LB, collimated by the collimator lens, are reflected by mirrors and travel in approximately the same direction. The four mirrors are arranged at different levels from each other or are half mirrors so as not to block the laser beams LB reflected by the other mirrors.

[0033] In color printing, a total of four laser beams LBy, LBm, LBc, and LBk corresponding to the colors Y, M, C, and K are emitted from the light source unit 60. The emitted laser beams LB are guided to the polygon unit 61 by a reflecting mirror 68.

[0034] The polygon unit 61 is an optical device in which a polygon mirror 62 and a polygon motor 63 that rotates the polygon mirror 62 are housed and integrated in a housing 610. The housing 610 is provided with glass windows 611 and 612 through which the laser beam LB passes. The polygon unit 61 also has a dust sensor 64 that detects the dust concentration inside the housing 610, and a position sensor 65 that detects when the rotation angle position of the polygon mirror 62 reaches a reference position.

[0035] The laser beam LB guided by the reflecting mirror 68 passes through a glass window 611 and is incident on a polygon mirror 62. The polygon mirror 62 is rotated at high speed in one direction by a polygon motor 63, and deflects the laser beam LB in the main scanning direction M1. The deflected laser beam LB passes through the glass window 611 and proceeds to an fθ lens 67. The polygon mirror 62 functions as an optical scanning means that scans the laser beam LB in one dimension.

[0036] The fθ lens 67 corrects the traveling direction of the incident laser beam LB so that it performs a constant speed main scan on the photosensitive member 4. The laser beam LB that passes through the fθ lens 67 is guided by reflection mirrors 69 to 75 to the photosensitive member 4 of each of the imaging units 3y to 3k, and irradiates the surface of the photosensitive member 4.

[0037] Furthermore, of the optical path 600 through which the laser beam LB passes after being deflected, reflecting mirrors 76 and 77 are arranged outside a main optical path 600A (shown with diagonal lines in FIG. 2(B)) corresponding to the latent image formation area. The laser beam LB passing outside the main optical path 600A is reflected by the reflecting mirrors 76 and 77, and is further reflected by reflecting mirrors 78 and 79, and is incident on optical sensors 80 and 81 as light beams LB_SOS and LB_EOS, respectively.

[0038] The reflecting mirror 76 is disposed, for example, near the upstream end of the reflecting mirror 72 in the main scanning direction M1. Therefore, the laser beam LB that has passed through the upstream portion of the optical path 600 in the main scanning direction M1 (deflection direction) is incident on the optical sensor 80. The optical detection signal from the optical sensor 80 is used as an SOS (Start of Scan) signal for synchronizing the start of main scanning for each line.

[0039] Furthermore, the reflecting mirror 77 is disposed near the downstream end of the reflecting mirror 72 in the main scanning direction M1. Therefore, the laser beam LB that has passed through the downstream portion of the optical path 600 in the main scanning direction M1 is incident on the optical sensor 81. The optical detection signal from the optical sensor 81 is used as an EOS (End of Scan) signal for synchronizing the end of main scanning for each line.

[0040] 3 is a circuit diagram of the optical sensor 80. The circuit of the optical sensor 81 is the same as the circuit of the optical sensor 80.

[0041] The optical sensor 80 is mounted on the optical sensor substrate 800. Also, the scanned optical beam LB_SOS is incident on the photodiode 801 in the optical sensor substrate 800, and a current proportional to the incident light amount is output to the current amplifier 802.

[0042] The current amplifier 802 amplifies the current from the photodiode 801, for example, by a factor of 10, and outputs it as the current Igain to the gain resistor 803. The current Igain is converted into a voltage by the gain resistor 803, and becomes the output of the optical sensor 80 as the analog output Vgain. Vgain = Igain × gain resistance value.

[0043] The voltage Vgain is also compared with the reference voltage Vref by the comparator 804, and is output from the optical sensor 80 as a digital output. When Vref > Vgain, an L-level output is obtained, and when Vref < Vgain, an H-level output is obtained.

[0044] When the light emission amount of the laser light source (LD) is made constant within one scan as shown in FIG. 4A, the light amount on the image surface of the photoreceptor 4 becomes non-uniform as shown in FIG. 4B due to the influence of the mirror reflectance, lens transmittance, etc. Therefore, light amount unevenness correction is performed. Specifically, as shown in FIG. 5A, the control unit 100 variably controls the light emission amount of the laser light source in the light source unit 60 according to the main scanning position. By this light amount unevenness correction, as shown in FIG. 5B, the light amount on the image surface of the photoreceptor 4 becomes constant at each position in the main scanning direction.

[0045] The transmittance and reflectance of optical components such as the mirror reflectance and lens transmittance have approximately determined characteristics. However, since there are individual differences for each component, the correction value for light amount unevenness correction is determined based on the unique information for each print head 6. In the following description, the correction value determined based on the unique information of this print head 6 is also referred to as the initial correction value. Also, since the unique information of the print head 6 does not change due to continuous use, the initial correction value is determined at the time of initial shipment.

[0046] Next, we will explain contamination on the polygon mirror 62. As shown in Figure 6, the polygon mirror 62 has a low external shape, for example, a regular hexagonal prism, and has six mirror surfaces 620 (620a to 620f) that form the side surfaces of the hexagonal prism. Each mirror surface 620 is strip-shaped with a length corresponding to one side of the regular hexagon. The polygon mirror 62 rotates at a predetermined speed around the geometric center of the regular polygon so that each mirror surface 620 deflects one line in the main scan.

[0047] The shape of the polygon mirror 62 in plan view may be a regular heptagon or another regular polygon.

[0048] Air currents are generated by the high-speed rotation of the polygon mirror 62. These air currents allow dust particles floating inside and outside the image forming apparatus 1 to pass through minute gaps in the print head 6 and enter the inside of the polygon unit 61.

[0049] Because the side surfaces of polygon mirror 62 are angular, vortices of air flow are generated near the side surfaces that are rotating at high speed. Vortices are particularly likely to be generated near the front end of each mirror surface 620 in the direction of rotation, and vortices generated at the front end move with the rotation of mirror surface 620, as if being dragged by mirror surface 620. In other words, polygon mirror 62 rotates while constantly generating vortices near front end portion 620A of mirror surface 620.

[0050] This vortex draws in dust particles floating around the polygon mirror 62 and causes them to adhere to the mirror surface 620. For this reason, as shown in Figure 6, more dust particles adhere to the front end side of the mirror surface 620 than to the rear end side. In other words, the front end side of each mirror surface 620 is more likely to become dirty with dust than the rear end side.

[0051] One of the changes over time in the polygon mirror 62 is a decrease in the light intensity of the laser beam LB due to dirt on the mirror surface 620. As described above, dirt on the mirror surface 620 progresses faster on the front end side, so the rate of decrease in light intensity on the upstream side in the main scanning direction M1 is greater than the rate of decrease in light intensity on the downstream side. This tendency is observed for all of the Y, M, C, and K laser beams LBy, LBm, LBc, and LBk.

[0052] As a result of this contamination of the polygon mirror 62 over time, as shown in FIG. 7A, the reflectance of the polygon mirror 62 after aging (shown by the dashed line and labeled "In-Use") decreases compared to the initial reflectance (shown by the solid line and labeled "Initial"). As mentioned above, the degree of decrease is greater upstream than downstream in the main scanning direction M1. Therefore, even if light intensity unevenness is corrected using an initial correction value based on the print head 6's unique information, as shown in FIG. 7B, the amount of light on the image plane of the photosensitive element 4 will not be constant at each position in the main scanning direction due to contamination of the polygon mirror 62, as shown by the dashed line in FIG. 7C. This results in image quality degradation. However, if the print head 6 is to be reused as a refurbished product, the image quality degradation caused by the contamination of the polygon mirror 62 must be corrected before shipping.

[0053] Therefore, in this embodiment, when reusing the print head 6, the correction value for correcting the uneven light amount is determined based on the unique information of the optical writing device, such as the transmittance and reflectance of the optical components, and the usage information of the print head 6. This process is explained with reference to FIG.

[0054] As described above, as a result of the polygon mirror 62 becoming dirty over time, the reflectivity of the polygon mirror 62 when the print head 6 is reused is reduced, as shown by the dashed line in FIG. 8A, compared to the initial reflectivity shown by the solid line. For this reason, the laser beam is emitted at an emitted light intensity (shown by the dashed line in FIG. 8B) obtained by adding a correction amount based on the usage information of the print head 6 to the emitted light intensity of the laser beam based on the initial correction value shown by the solid line in FIG. 8B. The correction amount based on the usage information of the print head 6 is estimated from the usage information of the print head 6. By such correction, the light intensity of the image on the photosensitive element 4 becomes uniform at each position in the main scanning direction, as shown in FIG. 8C.

[0055] In this embodiment, the amount of correction based on the usage information of the print head 6 is determined as a magnification of the correction value (correction value magnification) based on the output of the optical sensor 80. How the correction value magnification is determined based on the usage information using the optical sensor 80 will be described with reference to FIG.

[0056] The optical detection signal value (voltage value) and output width (output time), which are analog outputs of the optical sensor 80, change depending on the level of contamination on the polygon mirror 62. Therefore, by acquiring the optical detection signal value and output width, which are analog outputs of the optical sensor 80, the level of contamination on the polygon mirror 62 can be known.

[0057] In an initial, uncontaminated state, the photodetection signal value is large, for example, 2.0 V, as shown in the left diagram of FIG. 9A. Furthermore, the output width of the photodetection signal is also large, for example, 480 ns, as shown in the left diagram of FIG. 9B. The output width of the photodetection signal can be detected by the time the digital output is at a high level when the photodetection signal is compared with a predetermined reference voltage Vref in the circuit diagram of optical sensor 80 in FIG. 3.

[0058] When the contamination level is medium, as shown in the middle diagram of Fig. 9A, the photodetection signal value is slightly smaller than when there is no contamination, for example, 1.6 V. Also, as shown in the middle diagram of Fig. 9B, the output width of the photodetection signal is also slightly shorter, for example, 270 ns.

[0059] When the contamination level is high (late stage), as shown in the right diagram of Fig. 9A, the photodetection signal value becomes even smaller, for example, 1.0 V. Also, as shown in the right diagram of Fig. 9B, the output width of the photodetection signal becomes even shorter, for example, 190 ns.

[0060] Therefore, a corresponding correction value magnification is determined in advance for each photodetection signal value (voltage value) and / or output width (output time). Note that since there is a correlation between the photodetection signal value and the output width, a correction value magnification may be determined for only one of them.

[0061] FIG. 10A is a table showing an example of the relationship between the magnitude of the optical detection signal value (labeled optical sensor output in FIG. 10A) of the optical sensor 80 and the correction value magnification. For example, a correction value magnification of 7.50 is preset when the optical detection signal value is 0.2 to 0.4 V, and a correction value magnification of 5.00 is preset when the optical detection signal value is 0.4 to 0.6 V. The larger the optical detection signal value, the smaller the level of contamination, so the correction value magnification is smaller. Note that when the optical detection signal value is 0 to 0.2 V, the correction value magnification cannot be used. This indicates that the polygon mirror 62 is so contaminated that it cannot be recovered by correction.

[0062] 10B is a table showing an example of the relationship between the output width of the optical detection signal from the optical sensor 80 and the correction value magnification. For example, a correction value magnification of 5.00 is preset when the output width is 0.2 to 0.4 μs, and a correction value magnification of 3.33 is preset when the output width is 0.4 to 0.6 μs. The larger the output width, the smaller the level of contamination, so the correction value magnification is smaller. Note that when the output width is 0 to 0.2 μs, the correction value magnification cannot be used. This indicates that the polygon mirror 62 is so contaminated that it cannot be recovered by correction.

[0063] Figure 11 is a table illustrating correction values ​​for light intensity unevenness when reused, determined for the print head 6. Positions A to G in the main scanning direction M are set in advance, with A being the upstream position in the main scanning direction M and G being the downstream position, and an initial correction value specific to the print head 6 is determined for each position A to G. By applying these initial correction values, the light intensity on the image plane of the photosensitive element 4 is constant when the print head 6 is initially shipped (see Figure 5).

[0064] If the output signal value of the optical sensor 80 when the print head 6 with the above initial correction value is reused is 2.1 V, the correction value magnification based on the usage information of the print head 6 is 1.36 according to the table of FIG. 10A.

[0065] Therefore, the light amount unevenness correction value when the print head 6 is reused is a value obtained by multiplying the initial correction value for each of the positions A to G in the main scanning direction by the correction value magnification factor 1.36.

[0066] In the above embodiment, the correction value magnification based on the usage information is determined from the output of one optical sensor 80. However, the correction value magnification based on the usage information may be determined using the output of optical sensor 81 in addition to optical sensor 80. In this case, the average value of the light detection signal values ​​or output widths of the optical sensors 80 and 81 may be used as the value for determining the correction value magnification.

[0067] Thus, in this embodiment, the light intensity unevenness correction value when the print head 6 is reused is determined from the initial correction value based on the unique information of the print head 6 and the correction value magnification based on the usage information of the print head 6. Then, based on the determined correction value, the control unit 100 controls the light intensity within the one-dimensional scan. As a result, degradation of image quality caused by dirt on the polygon mirror 62, etc., can be corrected with high accuracy, and the print head 6 can be reused as a refurbished product without any problems.

[0068] Moreover, since there is no need to replace the dirty polygon mirror 62, a dustproof room or dedicated adjustment equipment is not required, and the print head 6 can be made to eliminate the problem of image quality degradation when reused.

[0069] Furthermore, in the above embodiment, the correction value magnification based on the usage information of the print head 6 is determined based on the output of the optical sensor 80. As another determination method, the correction value magnification based on the usage information may be determined based on the number of pages printed by the image forming apparatus 1 when the print head 6 is reused or the operating time of the print head 6.

[0070] FIG. 12 is a correspondence table of the number of printed sheets and the correction value magnification when the correction value magnification is determined based on the number of printed sheets. For example, the correction value magnification is preset to 1.00 when the number of printed sheets is 0 to 50,000, and 1.81 when the number of printed sheets is 50,000 to 100,000. The higher the number of printed sheets, the greater the level of contamination, so the correction value magnification increases. Note that the correction value magnification cannot be used when the number of printed sheets is 450,000 to 500,000. This indicates that the polygon mirror 62 is so contaminated that it cannot be recovered by correction.

[0071] FIG. 13 is a correspondence table showing the relationship between operation time and correction value magnification when the correction value magnification is determined based on the operation time of the print head 6. For example, a correction value magnification of 1.00 is preset when the operation time is between 0 and 50 hours, and a correction value magnification of 1.81 is preset when the operation time is between 50 and 100 hours. The longer the operation time, the greater the level of contamination, so the correction value magnification increases. Note that if the operation time is between 450 and 500 hours, the correction value magnification cannot be used. This indicates that the polygon mirror 62 is so contaminated that it cannot be restored by correction.

[0072] The image forming apparatus 1 is capable of accumulating the number of printed sheets and operating time and storing the accumulated data in the memory of the control unit 100. Therefore, the correction value magnification can be calculated from the accumulated number of printed sheets. In addition, the accumulated operating time can be used as the operating time of the print head 6, and the correction value magnification can be calculated from this operating time.

[0073] As described above, the initial correction value for light intensity unevenness is a value specific to each print head 6 because it takes into account individual differences between print heads 6. Therefore, data must be stored for each print head 6, and a memory is provided to store the initial correction value for light intensity unevenness. The memory may be provided in the print head 6. For example, as shown in FIG. 2, the light source unit 60 may be provided with a memory 60a, and the initial correction value may be stored in this memory. Alternatively, the initial correction value may be stored in the memory of the control unit 100 of the image forming apparatus 1 or in a data center such as the cloud. By storing the initial correction value in the print head 6, the initial correction value can be used as is when the print head 6 is replaced with a refurbished product in the market. Furthermore, when the initial correction value is stored in the memory of the image forming apparatus 1, the initial correction value tailored to the print head 6 is written into the memory before shipping the refurbished product. Furthermore, when the initial correction value is stored in a data center, the image forming apparatus 1 can read the correction value from the data center based on the serial number of the print head 6 and perform the correction.

[0074] Furthermore, at the time of the first refurbishing, the light intensity unevenness correction value calculated from the initial correction value and the correction value magnification based on the usage information may be used to update the initial correction value stored in the print head 6, the image forming apparatus 1, or the data center, and then saved. In this case, at the time of the second refurbishing, the light intensity unevenness correction value may be calculated based on the updated initial correction value and the correction value magnification based on the usage information from the previous refurbishing to the current refurbishing. Thereafter, the light intensity unevenness correction value at that time may be updated with each refurbishing.

[0075] In the above embodiment, the control unit 100 of the image forming apparatus 1 controls the light intensity of the laser beam LB emitted from the light source unit 60, but the print head 6 may also be equipped with a control unit, and the control unit of this print head 6 may control the light intensity of the laser beam LB. [Explanation of symbols]

[0076] 1. Image forming device 1A Automatic Document Feeder 1B Scanner 1C color printer 2 Printer Engine 3y, 3m, 3c, 3k imaging unit 4 Photoreceptor 6 Print head (optical writing device) 10 Intermediate transfer belt 16 Secondary transfer roller 17 Fixing unit 60 Light source unit 60a memory 61 polygon units 62 Polygon Mirror 63 Polygon Motor 64 Dust sensor 65 Position Sensor 65 67 fθ lens 68~79 Reflective mirror 80, 81 Optical sensor 100 control circuit 600 light path 610 Housing 800 Optical Sensor Board 801 Photodiode 802 Current Amplifier 803 Gain Resistor 804 Comparator LB laser beam

Claims

1. a light beam generating means for emitting a light beam; an optical scanning means for reflecting the light beam emitted from the light beam generating means and scanning in a one-dimensional direction; Equipped with an optical writing device in which the light amount of the light beam is variably controlled within one-dimensional scanning by the optical scanning means based on a light amount unevenness correction value, The optical writing device according to claim 1, wherein the light amount unevenness correction value when the optical writing device is reused is determined based on unique information of the optical writing device and usage information of the optical writing device.

2. at least one synchronization detection sensor for detecting a constant timing when the optical scanning means scans the light beam, 2. The optical writing device of claim 1, wherein the usage information is determined from the output of the at least one synchronization detection sensor.

3. 3. The optical writing device according to claim 2, wherein the synchronization detection sensors are plural, and the usage information is determined from outputs of the plural synchronization detection sensors.

4. 4. The optical writing device according to claim 2, wherein the usage information is an output value of an analog voltage output from the synchronization detection sensor.

5. 5. The optical writing device according to claim 4, wherein the usage information is an output width of the analog voltage.

6. The optical writing device according to claim 1 , wherein the usage information is the number of sheets on which an image written by the optical writing device is printed.

7. The optical writing device according to claim 1 , wherein the usage information is an operating time of the optical writing device.

8. 8. The optical writing device according to claim 1, wherein the light amount unevenness correction value is stored in a memory.

9. 8. The optical writing device according to claim 1, wherein a light intensity unevenness correction value when the optical writing device is reused is determined and updated from the unique information and the usage information.

10. one or more photoreceptors; an optical writing device according to any one of claims 1 to 3, 6 and 7 for irradiating a light beam to write image data onto the photosensitive member; a light amount control means for variably controlling the light amount of the light beam within one-dimensional scanning by the optical scanning means based on the light amount unevenness correction value; An image forming apparatus comprising:

Images