JP5697310B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming equipment for forming an image by using a plurality of laser beams.

  Conventionally, in an image forming apparatus, an electrostatic charge formed on a photosensitive drum is exposed with a semiconductor laser to form an electrostatic latent image, and developed with a developer to form an image. A conventional semiconductor laser irradiates one to four, and at most about eight laser beams from one semiconductor element.

  In recent years, a vertical cavity surface emitting laser called VCSEL (Vertical Cavity Surface Emitting LASER) has been put into practical use. Accordingly, an image forming apparatus using a VCSEL has been proposed.

  This VCSEL can emit about 40 laser beams from one chip. For this reason, it is considered that high-definition and high-speed image formation becomes possible by using a VCSEL for forming a latent image of the image forming apparatus.

  By the way, when a VCSEL is used for forming a latent image, a high-definition latent image cannot be formed at high speed simply by replacing the semiconductor laser with the VCSEL. For example, a laser device used for forming a latent image needs to control the amount of emitted laser beam to be a target amount of light. Of course, a VCSEL also has a laser in a light emitting region that generates a large number of laser beams. It is necessary to manage the light intensity of the beam.

  Therefore, when performing light amount control similar to that of a semiconductor laser with a small number of laser beams on a VCSEL with an increased number of laser beams, it takes a long time to control the light amount, and speeding up is limited. Occurs. For this reason, if the control of the light amount of the laser beam is thinned out, it becomes difficult to achieve high definition.

  For these reasons, various techniques have been proposed. For example, Patent Document 1 discloses an optical writing device including a light emitting light source unit having a plurality of light emitting elements and a light amount detecting element for detecting a light amount emitted from the light emitting elements. The optical writing device disclosed in Patent Document 1 includes a volume resistor and a sample hold capacitor for the number of beams in order to control the light amount of the light beam. Even with the technique described in Patent Document 1, it is possible to control the amount of light of a large number of laser beams.

  Further, in Patent Document 2, a first measuring unit for separating each light beam output from the light source into a first light beam and a second light beam, and measuring the light quantity of the first light beam; And a light quantity control means for performing light quantity control so that the light quantity measurement result by the first measurement means becomes the light quantity instructed by the light quantity instruction signal, the light quantity of the second light beam is measured, and the light quantity measurement result is A technique is disclosed in which the light quantity correction coefficient of each light beam for obtaining the light quantity of the second light beam to be substantially uniform among a plurality of light beams is obtained and stored, and the light quantity is controlled. It is possible to control the amount of light by applying the technique disclosed in Patent Document 2 to a VCSEL.

  However, with the technique described in Patent Document 1, the circuit scale of the VCSEL control circuit itself is increased. Further, in order to adjust the amount of light, the volume resistance must be set for the number of emitted beams, which causes a problem that work efficiency is lowered and maintenance is increased.

  Further, in the technique described in Patent Document 2, performing image formation while correcting the amount of light of each laser beam can provide a sufficient feedback speed when the number of laser beams is small. In addition, when a much larger number of laser beams are emitted, when considering the environmental variation of the VCSEL, it is not possible to provide feedback with respect to the control of the light amount of the light beam with sufficient efficiency only in the scanning period during image formation. There is a problem that may occur. As described above, when performing laser beam light amount control for forming an electrostatic latent image using a VCSEL, the control operation must be increased by an increase in the number of laser beams. There has been a problem that the advantage of the conversion cannot be sufficiently achieved.

The present invention was made in view of the above, and an object thereof is to provide an image forming equipment which can manage the amount of multiple laser beams efficiently.

In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention includes a light source that outputs a first laser beam and a second laser beam, and the first laser beam output from the light source. The laser beam is separated into a third laser beam for measuring the amount of light and a fifth laser beam for scanning the photosensitive member, and the second laser beam output from the light source is measured for the amount of light. Separating means for separating the fourth laser beam for scanning and the sixth laser beam for scanning the photosensitive member, and measurement for measuring the light amounts of the third laser beam and the fourth laser beam Means, photoelectric conversion means for outputting a voltage in accordance with the measured light amounts of the third laser beam and the fourth laser beam, the first laser beam generated during one scan, and the second laser beam Laser beam tie A first beam-specific correction value for controlling the amount of light of the first laser beam based on the voltage of the third laser beam output by the photoelectric conversion means according to the scanning signal, and the photoelectric conversion means First calculation means for calculating a second beam-specific correction value for controlling the amount of the second laser beam based on the voltage of the fourth laser beam; the first beam-specific correction value; A second calculation means for calculating a common current value indicating a drive current value common to the first laser beam and the second laser beam based on the correction value for each beam, and during the first image formation. The first beam-specific correction value and the second beam-specific correction value calculated by the first calculation means, and the second image formation calculated immediately before the first image formation. First beam Said common current value calculated by the correction value and the second calculating means based on said second beam specific correction value, based on the amount of the first laser beam and said second laser beam, Control means for controlling during the one scan.

  According to the present invention, by performing appropriate light quantity control, there is an effect that good image formation is possible while minimizing the circuit scale and the maintenance cost.

FIG. 1 is a hardware diagram illustrating a configuration of the image forming apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a planar configuration in which the optical device of the image forming apparatus is referenced from the line of sight A illustrated in FIG. FIG. 3 is a diagram for explaining the APC between sheets of the image forming apparatus according to the first embodiment. FIG. 4 is a block diagram illustrating a configuration for driving the VCSEL of the image forming apparatus according to the first embodiment. FIG. 5 is a graph showing identification of output characteristics of the laser beam output from the image forming apparatus according to the first embodiment. FIG. 6 is a diagram showing a table structure for storing initial values for controlling the VCSEL in the ROM area of the microcontroller. FIG. 7 is a diagram illustrating a configuration of a DEV calculation unit included in the drive current calculation unit. FIG. 8 is a diagram illustrating a configuration of the SW calculation unit included in the drive current calculation unit. FIG. 9 is a block diagram illustrating details of the driver of the image forming apparatus according to the first embodiment. FIG. 10 is a diagram illustrating input / output signals of the APC mode control unit of the image forming apparatus according to the first embodiment. FIG. 11 is a diagram illustrating mode transition of the APC mode control unit of the image forming apparatus according to the first embodiment. FIG. 12 is a diagram illustrating a timing chart of signals generated by the image forming apparatus according to the first embodiment when “APC_MODE” is “mode0”. FIG. 13 is a timing chart of signals generated by the image forming apparatus according to the first embodiment when “APC_MODE” is “mode1” or “mode2”. FIG. 14 is a flowchart illustrating a control procedure of the light amount of the laser beam in the image forming apparatus according to the first embodiment.

  Exemplary embodiments of an image forming apparatus and an image forming method according to the present invention are explained in detail below with reference to the accompanying drawings. The present invention is not limited to the embodiments described later, and can be applied to various image forming apparatuses that perform image formation using a plurality of beams.

(First embodiment)
FIG. 1 is a hardware diagram illustrating a configuration of an image forming apparatus 100 according to the first embodiment. As shown in FIG. 1, an image forming apparatus 100 according to the first embodiment includes an optical device 102 including optical elements such as a semiconductor laser and a polygon mirror, and an image including a photosensitive drum, a charging device, a developing device, and the like. The image forming apparatus includes a forming unit 112 and a transfer unit 122 including an intermediate transfer belt. The optical device 102 deflects a light beam emitted from a light source such as a semiconductor laser (not shown) by a polygon mirror 102c and makes it incident on an fθ lens. In the illustrated embodiment, a number of light beams corresponding to the respective colors of cyan (C), magenta (M), yellow (Y), and black (K) are generated, and after passing through the fθ lens 102b, the reflecting mirror 102a. Reflected by.

  After shaping the light beam, the WTL lens 102d deflects the light beam toward the reflection mirror 102e, and the light beam is transmitted to the photosensitive drums 104a, 106a, 108a, 110a as the light beam L used for exposure. Imagewise irradiation. The irradiation of the light beam L onto the photosensitive drums 104a, 106a, 108a, and 110a is performed using a plurality of optical elements as described above, and therefore timing synchronization is performed in the main scanning direction and the sub-scanning direction. Yes. Hereinafter, the main scanning direction is defined as the light beam scanning direction, and the sub-scanning direction is a direction orthogonal to the main scanning direction. In the image forming apparatus 100, the photosensitive drums 104a, 106a, 108a, 110a Defined as the direction of rotation.

  Each of the photosensitive drums 104a, 106a, 108a, and 110a includes a photoconductive layer including at least a charge generation layer and a charge transport layer on a conductive drum such as aluminum. The photoconductive layer is disposed corresponding to each of the photosensitive drums 104a, 106a, 108a, and 110a, and is charged with a surface charge by the chargers 104b, 106b, 108b, and 110b including a corotron, a scorotron, or a charging roller. Is granted.

  The electrostatic charges imparted on the photosensitive drums 104a, 106a, 108a, 110a by the respective chargers 104b, 106b, 108b, 110b are imagewise exposed by the light beam L to form an electrostatic latent image. The electrostatic latent images formed on the photosensitive drums 104a, 106a, 108a, and 110a are developed by developing units 104c, 106c, 108c, and 110c including a developing sleeve, a developer supply roller, a regulating blade, and the like, and a toner image is developed. It is formed.

  The toner images carried on the photosensitive drums 104a, 106a, 108a, and 110a are transferred onto the intermediate transfer belt 114 that moves in the direction of arrow B by the conveying rollers 114a, 114b, and 114c. The intermediate transfer belt 114 is conveyed to the secondary transfer unit while carrying C, M, Y, and K toner images. The secondary transfer unit includes a secondary transfer belt 118 and conveying rollers 118a and 118b. The secondary transfer belt 118 is conveyed in the direction of arrow C by the conveyance rollers 118a and 118b. An image receiving material 124 such as high-quality paper or a plastic sheet is supplied to the secondary transfer portion from an image receiving material storage portion 128 such as a paper feed cassette by a conveying roller 126.

  The secondary transfer unit applies a secondary transfer bias to transfer the multicolor toner image carried on the intermediate transfer belt 114 onto the image receiving material 124 held by suction on the secondary transfer belt 118. The image receiving material 124 is supplied to the fixing device 120 along with the conveyance of the secondary transfer belt 118. The fixing device 120 includes a fixing member 130 such as a fixing roller including silicone rubber, fluorine rubber, and the like. The fixing member 120 pressurizes and heats the image receiving material 124 and the multicolor toner image to form a printed matter 132 of the image forming apparatus 100. Output to the outside. After the transfer of the multicolor toner image, the intermediate transfer belt 114 is prepared for the next image forming process by removing the transfer residual toner by a cleaning unit 116 including a cleaning blade.

  A sub-scanning deviation detecting device (not shown) is provided near the end point in the main scanning direction of each of the photosensitive drums 104a, 106a, 108a, and 110a, and detects a deviation in the sub-scanning direction. .

  FIG. 2 is a diagram illustrating a planar configuration in which the optical device 102 of the image forming apparatus 100 is referenced from the line of sight A illustrated in FIG. In FIG. 2, the photosensitive drum 104a on which an electrostatic latent image is formed, which cannot be referred to from the line of sight A, is also shown for clarity of scanning with a laser beam.

  As shown in FIG. 2, the optical device 102 includes a driver 206, a VCSEL controller 200, a drive current calculation unit 204, an A / D conversion unit 202, a VCSEL 208, a coupling optical element 210, a half mirror 212, A total reflection mirror 214, a second condenser lens 216, and a photoelectric conversion element 218 are provided.

  A VCSEL controller (hereinafter referred to as GAVD) 200 is an application specific integrated circuit (ASIC) and receives a control signal from a CPU (not shown) that controls image formation of the image forming apparatus 100. Then, the drive control of the VCSEL 208 is commanded. Further, the GAVD 200 issues a factory adjustment signal, an initialization signal, a line APC (Auto Power Control) signal, an inter-paper APC signal, etc. to the VCSEL 208 in response to a command from the CPU. The line APC is a control for correcting the light amount of the laser beam at every timing when the laser beam is scanned in the main scanning direction while the image forming apparatus 100 is operating and printing on the printed matter (recording paper). To do. The inter-paper APC is a control in which a light quantity of a laser beam is corrected by a method different from the line APC between a plurality of printed materials that are being continuously printed and between the printed materials (inter-paper).

  FIG. 3 is a diagram for explaining the APC between sheets. In the example shown in FIG. 3, when the intermediate transfer belt moves in the transport direction B, the inter-paper APC is performed by the light beam L scanning the photosensitive drum K to form a toner image for the paper P, and thereafter When the next sheet P ′ is irradiated, control is performed to correct the light amount of the laser beam at an interval INT until the light beam L scans the photosensitive drum K. As described above, the inter-paper APC indicates that the light amount of the laser beam is corrected after printing on an arbitrary printed material (recording paper) and before printing the next printed material.

  Returning to FIG. 2, the driver 206 supplies a drive current to the VCSEL 208. Specifically, the driver 206 receives the control signal from the GAVD 200 and supplies the drive current corresponding to the control signal to the VCSEL 208, thereby driving the VCSEL 208. Then, the driven VCSEL 208 generates a laser beam. Forty laser beams corresponding to 40 channels are emitted from the VCSEL 208 according to the present embodiment. Although this embodiment is an example in which 40 beams are emitted, the number of emitted laser beams is not particularly limited.

  The laser beam is collimated by the coupling optical element 210 and then enters the half mirror 212. The half mirror 212 is formed by dielectric multilayer coating or the like. The half mirror 212 functions as a light separating unit, and separates the incident laser beam into a monitor beam for measuring the light amount and a scanning beam for scanning the photosensitive member.

  The scanning beam is deflected by the polygon mirror 102c, passes through the fθ lens 102b, and is irradiated onto the photosensitive drum 104a. Note that a synchronization detection device 220 including a photodiode (PD) is disposed in the vicinity of the scanning start position of the photosensitive drum 104a. The synchronization detection device 220 detects a laser beam (scanning beam) and issues a synchronization signal. The synchronization signal is a signal that gives timing for various controls including the first light quantity correction.

  The monitor beam is reflected by the total reflection mirror 214 to the second condenser lens 216, and is irradiated to the photoelectric conversion element 218 such as a photodiode through the second condenser lens 216. The photoelectric conversion element 218 generates a monitor voltage Vpd corresponding to the light amount of the monitor beam. The generated monitor voltage Vpd is converted into a monitor signal corresponding to the monitor voltage Vpd by the A / D converter 202. Then, the monitor signal is transmitted to the drive current calculation unit 204.

  The drive current calculation unit 204 generates, for example, VCSEL control data based on the value of the amount of laser beam light indicated by the input monitor signal. The generated VCSEL control data is used for driving current control by the driver 206. For this reason, the drive current calculation unit 204 outputs the generated VCSEL control data to the driver 206.

  The A / D conversion unit 202 and the drive current calculation unit 204 may be configured as separate modules or may be configured integrally. In the case of an integrated configuration, for example, a microcontroller including a ROM, a RAM and the like for storing various control values used for processing can be considered.

  FIG. 4 is a block diagram showing a configuration for driving the VCSEL 208. As shown in FIG. 4, in order to drive the VCSEL 208, the image forming apparatus 100 includes a CPU 400, a synchronization detection device 220, a GAVD 200, a driver 206, a VCSEL 208, a microcontroller 401, an APC control unit 402, A photoelectric conversion element 218.

  The GAVD 200 receives a control signal from the CPU 400, and starts factory setting adjustment and initialization setting of the VCSEL 208. In parallel, the synchronization detector 220 starts detecting the laser beam.

  FIG. 5 is a graph showing the identification of the output characteristics (hereinafter referred to as IL characteristics) 400 of the laser beam output from the image forming apparatus 100 according to the present embodiment. In the present embodiment, it is assumed that the VCSEL 208 is composed of a 40ch semiconductor laser element. The graph shown in FIG. 5 shows the amount of light output according to the current supplied to each semiconductor laser element. As shown in FIG. 5, each semiconductor laser element has a threshold current Ibi for starting laser oscillation. The semiconductor laser elements have different output L-drive current levels I corresponding to the respective element characteristics. For this reason, the drive current Iη for each semiconductor laser element to output the same laser beam light amount is different by the value ΔI even at the initial setting. The initial drive current value Iswi indicates the probe current value for the channel i registered in the ROM area of the memory 412 based on the factory measurement before shipment. The initial drive current value Iswi is used when initializing the semiconductor laser element. I according to the present embodiment represents each channel of the laser beam of the VCSEL 208, and takes a value of ch = 1 to 40 in the present embodiment.

  Returning to FIG. 4, the APC control unit 402 includes an A / D conversion unit 202, a drive current calculation unit 204, and an I / F control unit 403.

  The microcontroller 401 includes a calculation unit 411 and a memory 412 including a ROM area and a RAM area. The memory 412 stores initial values of various control values used by the drive current calculation unit 204. Furthermore, the ROM area stores factory setting data and the like, and the RAM area is used as a register memory for storing values necessary for processing.

  FIG. 6 is a diagram showing a table structure for storing initial values for controlling the VCSEL controller 200 in the ROM area of the microcontroller 401. As shown in FIG. 6, in the ROM area, a channel number 502, an initial monitor voltage Vpd 504, and an initialization current Isw_A 506 are stored in association with each other. As shown in FIG. 6, initial values of various control values of the VCSEL controller 200 are registered for each channel 502 assigned to the semiconductor laser element. The initial monitor voltage Vpdi 504 is a monitor voltage of the photoelectric conversion element 218 set at the time of factory shipment. The initialization current Isw_A 506 is an average value of the initial drive current values Iswi set for each semiconductor laser element. The initialization current Isw_A 506 is assumed to be a current for giving a monitor light quantity at the time of light quantity control. The initial values of the various control values stored in these ROM areas are used for calculation by the drive current calculation unit 204 in the APC control unit 402.

  Returning to FIG. 4, the microcontroller 401 receives a command from the GAVD 200 via the I / F control unit 403 of the APC control unit 402. Then, the calculation unit 411 calculates an initial setting value using the factory setting data stored in the memory 412 and the light amount of the laser beam in response to the received command. Then, the microcontroller 401 sets the register memory 421 included in the drive current calculation unit 204 via the I / F control unit 403.

  The drive current calculation unit 204 includes a register memory 421, a DEV calculation unit 422, and a SW calculation unit 423.

  The register memory 421 includes a ch1 register 705_1 to a ch40 register 705_40, which will be described later, and an SW register 805. That is, initial values are set by the microcontroller 401 for the ch1 register 705_1 to ch40 register 705_40 and the SW register 805 at the time of initial activation.

  The DEV calculation unit 422 calculates a beam-specific current correction value DEVi for each laser beam (i) based on the monitor signal output from the A / D conversion unit 202 or the like. The beam-specific current correction value DEVi indicates a correction value for correcting a current for controlling the amount of light for each laser beam.

  The SW calculation unit 423 calculates a common supply current value Isw that is a current supplied in common to all the laser beams based on the beam-specific current correction value DEVi for each laser beam.

  It is assumed that the VCSEL control data includes the beam-specific current correction value DEVi and the common supply current value Isw. The calculated beam-specific current correction value DEVi and the common supply current value Isw are updated and stored in the register memory 421. The VCSEL control data stored in the register memory 421 is used for the light quantity control of the VCSEL 208 due to the continuous operation of the VCSEL 208 and the environmental variation of the image forming apparatus 100. The calculation method by the DEV calculation unit 422 and the SW calculation unit 423 will be described later.

  The VCSEL control data calculated by the APC control unit 402 is sent to the GAVD 200. As the first VCSEL control data, the initial set current value set by the microcontroller 401 is input to the driver 206 together with the lighting signal of each channel. The driver 206 performs PWM conversion on the input initial set current value to set a drive current, and supplies a current at the set drive current level to the channel specified by the channel lighting signal. The VCSEL 208 driven by the supplied current generates a laser beam. The generated laser beam of each channel is fed back via the photoelectric conversion element 218 in order to control the light amount of the laser beam. Based on the footback-backed monitor signal, the drive current calculation unit 204 calculates an appropriate common supply current value Isw and beam-specific current correction value DEVi.

  FIG. 7 is a diagram illustrating a configuration of the DEV calculation unit 422 included in the drive current calculation unit 204. As shown in FIG. 7, the DEV calculation unit 422 includes a ch1 target value register 701_1 to ch40 target value register 701_40, a selector 702, a subtracter 703, an adder 704, a ch1 register 705_1 to a ch40 register 705_40, and a selector. 706, an enable signal generation unit 707, an APC mode control unit 708, a timing generation unit 709, and multipliers 710_1 to 710_40.

  The ch1 target value registers 701_1 to ch40 target value registers 701_40 hold predetermined APC target values for each channel. In image forming apparatus 100 according to the present embodiment, a channel is assigned to each semiconductor laser element of VCSEL 208.

  The APC mode control unit 708 controls the APC control mode. The APC control mode will be described later.

  The timing generation unit 709 generates a channel designation signal (APC_CH) that specifies a VCSEL channel for performing APC, generates a lighting timing (LDON) of the VCSEL 208, generates a sampling timing (AD_SMP) of the AD conversion unit 202, and a ch1 register described later. The update timing (CTL_EN) of 705_1 to ch40 register 705_40 is generated.

  The selector 702 selects one of the APC target values of each channel held in the ch1 target value register 701_1 to ch40 target value register 701_40 according to the APC_CH generated by the timing generation unit 709, and outputs it to the subtractor 703. To do.

  The subtractor 703 subtracts the monitor signal corresponding to the light amount of the monitor beam of each channel input from the A / D converter 202 from the APC target value of each channel input from the selector 702. This subtracted value is set as a target difference value.

  The adder 704 adds an output value from a selector 706 described later to the target difference value of each channel output from the subtracter 703.

  The enable signal generation unit 707 outputs a write enable signal to the corresponding ch1 register 705_1 to ch40 register 705_40 according to the update timing (CTL_EN) generated by the timing generation unit 709.

  The ch1 register 705_1 to ch40 register 705_40 hold the output value output from the adder 704. The output value is updated at the timing when the write enable signal is input from the enable signal generation unit 707.

  The selector 706 outputs the output values stored in the ch1 register 705_1 to the ch40 register 705_40 to the adder 704 in accordance with APC_CH generated by the timing generation unit 709.

  Multipliers 710_1 to 710_40 multiply the output values output from the ch1 register 705_1 to ch40 register 705_40 by a gain to generate beam-specific current correction values DEV1 to DEV40. The beam current correction values DEV1 to DEV40 generated by the multipliers 710_1 to 710_40 are output to the GAVD 200 and the SW calculation unit 423.

  When the DEV calculation unit 422 has the above-described configuration, when the monitor signal (indicating the light amount of the monitor beam) input from the A / D conversion unit 202 of each channel of the VCSEL 208 is larger than the target value of each channel. The feedback control is applied so as to decrease the beam-specific current correction value DEV of the corresponding channel, and when it is small, the feedback control is applied so that the beam-specific current correction value DEV data of the corresponding channel is increased. For this reason, the light quantity of the laser beam output for each semiconductor laser element of the VCSEL controller 200 is controlled so as to become the target value.

  FIG. 8 is a diagram illustrating a configuration of the SW calculation unit 423 included in the drive current calculation unit 204. The SW calculation unit 423 includes an average value calculation unit 801, a target value register 802, a subtracter 803, an adder 804, an SW register 805, an enable signal generation unit 806, and a multiplier 807.

  The SW calculation unit 423 performs processing for correcting the common supply current value Isw in the inter-paper APC mode. In other words, there is a possibility that all the laser beams of the VCSEL 208 cannot be output with the target light amount only by correcting with the beam-specific current correction value DEVi data by the DEV calculation unit 422. Therefore, the common supply current value Isw is corrected so that all the laser beams are within a range that can be corrected by the beam-specific current correction value DEVi data.

  The average value calculation unit 801 calculates the average value of DEV1 to DEV40 input from the DEV calculation unit 422. The calculated average value is output to the subtracter 803.

  The target value register 802 holds a target value of a predetermined common supply current value Isw.

  The subtracter 803 subtracts the target value held by the target value register 802 from the average value input from the average value calculation unit 801. A value obtained by subtracting the target value from the input average value is defined as an average difference value.

  The enable signal generation unit 806 determines whether to permit writing based on the update timing (CTL_EN) output from the timing generation unit 709 and the APC control mode output from the APC mode control unit 708. When the enable signal generation unit 806 determines to permit writing, the enable signal generation unit 806 outputs a write enable signal to the adder 804 and the SW register 805.

  When the write enable signal is input from the enable signal generation unit 806, the adder 804 adds an output value output from the SW register 805 described later to the average difference value input from the subtracter 803.

  The SW register 805 holds the output value input from the adder 804. The output value is updated when a write enable signal is input from the enable signal generation unit 806.

  The multiplier 807 outputs a common supply current value Isw obtained by multiplying the output value of the SW register 805 by a gain.

  With this configuration, the common supply current value Isw is increased when the average value of DEV is larger than the target value, and the common supply current value Isw is decreased when the average value of DEV is smaller than the target value. .

  The image forming apparatus 100 according to the present embodiment is configured to calculate the common supply current value Isw by feeding back the average value of the beam-specific current correction values DEVi. That is, in the image forming apparatus 100 according to the present embodiment, the common supply current value Isw is the average value of the beam-specific current correction values DEVi calculated for each laser beam, and thus has a significant influence on latent image formation. Good image formation becomes possible without giving.

  However, in the image forming apparatus according to the modification of the present embodiment, the maximum value and the minimum value of the beam-specific current correction value DEV are used as the calculation of the common supply current value Isw instead of the average value of the beam-specific current correction value DEVi. The average value may be obtained. Thereby, even when there is only one abnormal channel among the VCSEL channels, the probability that appropriate control is performed is improved.

  The driver 206 performs PWM control on the VCSEL 208 using the bias current (Ib), the common supply current value Isw, and the beam-specific current correction value DEVi stored in the register memory 421 and the like.

  Thereafter, the driver 206 controls to output a laser beam with an appropriate light amount for each channel based on the common supply current value Isw and the beam-specific current correction value DEVi calculated by the drive current calculation unit 204.

  FIG. 9 is a block diagram showing details of the driver 206. In FIG. 9, the driver 206 includes a bias current generation unit 206b and a common current supply unit 206d. In the example shown in FIG. 9, each code is distinguished by adding a subscript from 1ch to 40ch.

  The driver 206 includes a correction value setting unit 206ai and an LD current supply unit 206ci for each semiconductor laser element LD (i = 1 to 40) that issues a laser beam.

  The bias current generator 206b generates a bias current (Ib) and supplies it for each semiconductor laser element LD (i = 1 to 40). The bias current (Ib) is set to a preset value, for example, 3 mA.

  The common current supply unit 206d supplies a common current for each semiconductor laser element LD according to the input common supply current value Isw.

  The correction value setting unit 206ai (i = 1 to 40) sets the beam-specific current correction value i for each channel with respect to the supplied common current. Then, the correction value setting unit 206ai (i = 1 to 40) corrects the common current based on the common supply current value Isw supplied from the common current supply unit 206d with the beam-specific current correction value DEVi. The correction value setting unit 206ai can correct the current value within the range of 68% to 132% with respect to the common current based on the common supply current value Isw. That is, by setting the common supply current value Isw to the average value of the beam-specific current correction values DEVi, the beam-specific current correction value DEVi can be prevented from being out of the correction range.

  The current supply unit 206ci (i = 1 to 40) adds the bias current (Ib) generated by the bias current generation unit 206b to the corrected current and supplies it to the semiconductor laser element LD.

  In the present embodiment, the driver 206 having the above-described configuration can supply a drive current of Isw × DEVi + Ib to the semiconductor laser elements LDi (i is an integer of 1 to 40) of each channel.

  Next, signals output from the APC mode control unit 708 will be described. FIG. 10 is a diagram for explaining input / output signals of the APC mode control unit 708. As shown in FIG. 10, the APC mode control unit 708 receives a reset signal (reset_n), an APC enable signal (apc_enable), a write_ready signal, and an apc_fgate signal as input signals, and outputs bd_en and APC_MODE as output signals. . Further, the APC mode control unit 708 changes the mode based on the input signal that is input.

  The reset signal (reset_n) is a signal input from the CPU 400 as a signal for initializing the APC mode control unit 708. The APC enable signal (apc_enable) is a signal input from the CPU 400 as a signal indicating whether or not APC can be executed. The write_ready signal is input from the GAVD 200 as a signal indicating whether writing preparation is completed (main scanning synchronization processing is completed).

  The apc_fgate signal is input from the CPU 400 as a signal indicating whether or not it is the sheet interval timing. The apc_fgate signal is input at a low level when it is not a paper interval timing, and is input as a high level when it is a paper interval timing.

  FIG. 11 is a diagram showing mode transition of the APC mode control unit 708. In any mode, the APC mode control unit 708 shifts to the “init” mode when the input reset signal (reset_n) is at the low level. Also, the APC mode control unit 708 shifts to the “init” 1001 mode even when the apc_enable signal becomes the Low level.

  When the APC mode signal of the APC mode control unit 708 is “init” mode 1001 and the input APC enable signal (apc_enable) becomes High level, the APC mode shifts to “mode 0” 1002.

  Next, after the APC mode of the APC mode control unit 708 shifts to the “mode 0” mode 1002, the APC control process shifts to the “hold” mode 1003 after the designated number of APC control processes are completed. The designated number of times of this APC control processing is set in advance in the register memory 421 in the drive current calculation unit 204 by the microcontroller 401.

  When the APC mode of the APC mode control unit 708 shifts to the “hold” mode 1003, the APC mode control unit 708 notifies the GAVD 200 of the output signal “bd_en” as a high level. As a result, the GAVD 200 starts a main scanning synchronization process (hereinafter referred to as a BD synchronization process). After the BD synchronization processing is completed in the GAVD 200, the GAVD 200 inputs the write_ready signal to the APC mode control unit 708 at the High level. Then, the APC mode control unit 708 shifts to the “mode 1” mode 1004 with the input of the signal as a trigger. Note that “mode 1” is a mode for performing APC between sheets.

  After that, when the APC mode of the APC mode control unit 708 is “mode1” 1004, when “apc_fgate” is input as a high level, the mode shifts to “mode2” 1005. “Mode2” is a mode for performing line APC.

  When the APC mode of the APC mode control unit 708 is “mode2” 1005, when “apc_fgate” is input as a low level, the mode shifts to “mode1” 1004 again. As described above, the APC mode control unit 708 switches between “mode1” and “mode2” in accordance with switching between “High level” and “Low level” of “apc_fgate”.

  Then, the APC mode control unit 708 outputs the above-described signal indicating “mode 0”, “mode 1”, or “mode 2” to the timing generation unit 709 and the SW calculation unit 423 as APC_MODE.

  FIG. 12 is a diagram illustrating a timing chart of signals generated by the timing generation unit 709, the enable signal generation unit 707, and the enable signal generation unit 806 when “APC_MODE” is “mode0”. “APC_CH” in FIG. 12 is a signal for generating a timing for processing each channel of ch1 to ch40. The timing generation unit 709 generates “APC_CH” for the period of the number of times designated by the microcontroller 401 with ch1 to ch40 as one period. Thereby, APC control of each channel for the designated period is performed.

  Then, the timing generation unit 709 generates a lighting timing signal (LDON) for each channel of the VCSEL 200 according to the APC_CH to be generated, and outputs it to the GAVD 200. At the same time, the timing generation unit 709 generates a sampling timing signal (AD_SMP) according to the generated APC_CH, and outputs the sampling timing signal (AD_SMP) to the A / D conversion unit 202.

  After that, the timing generation unit 709 generates a register update timing (CTL_EN) so that the register in the drive current calculation unit 204 is updated according to the result of the process performed by the output signal, and the enable signal generation unit 707. And output to the enable signal generation unit 806.

  Then, the enable signal generation unit 707 instructs to update the registers of the designated channel (ch1 register 705_1 to ch40 register 705_40) according to the input register update timing (CTL_EN) and the channel designation signal (APC_CH). “REG_ch1_en” to “REG_ch40_en” are generated. As a result, the ch1 register 705_1 to the ch40 register 705_40 are updated.

  The enable signal generation unit 806 generates a write enable signal “REG_sw_en” that instructs to update the SW register 805 in accordance with the input APC mode (APC_MODE), register update timing (CTL_EN), and channel designation signal (APC_CH). Specifically, in the case of APC_MODE = “mode0”, it is generated with a trigger that the register update timing (CTL_EN) becomes High level during APC_CH = “ch40”. As a result, the control for updating the common supply current value Isw is performed after the registers of all channels ch1 to ch40 are updated.

  FIG. 13 is a diagram illustrating a timing chart of signals generated by the timing generation unit 709, the enable signal generation unit 707, and the enable signal generation unit 806 when “APC_MODE” is “mode1” or “mode2”. . In the example shown in FIG. 13, the VCSEL 200 is turned on outside the image area immediately before the line clear signal (LCLR) output at the start of the main scanning by the VCSEL 200 to perform light quantity correction control.

  In the example shown in FIG. 13, a timing signal for performing APC control for two channels is shown for one scan by main scanning. That is, signals for two channels are generated with “APC_CH” per scan. The procedure from the issue of “APC_CH” to the generation of the enable signal is the same as the procedure in “mode 0” shown in FIG. When there is a margin in timing, the number of APC channels controlled per scan may be increased.

  In addition, the update of the SW register 805 in which Isw is stored affects the light amount of the laser beam of all the channels of the VCSEL. For this reason, if Isw is changed during image formation, the image density changes abruptly. Therefore, in the mode “mode 2” in which line APC is performed, the enable signal generation unit 806 does not generate a signal for updating so as not to control Isw.

  That is, “CTL_EN”, “APC_MODE”, and “APC_CH” are input to the enable signal generation unit 806. When “APC_MODE” is “mode1” and “APC_MODE” is ch40, if “CTL_EN” is at a high level, an enable signal is output at a high level. Then, if the “APC_MODE” is “mode2”, the enable signal generation unit 806 always outputs the enable signal as a low level.

  As described above, in the present embodiment, DEV and Isw are controlled when “mode 1”, and only the beam-specific current correction value DEVi is controlled when “mode 2”. However, the present invention is not limited to such control, and it is designed to be able to set whether to control each of the beam-specific current correction value DEVi and the common supply current value Isw for each mode. It is possible to perform control suitable for the situation.

  Next, a control procedure of the light amount of the laser beam in the image forming apparatus 100 according to this embodiment will be described. FIG. 14 is a flowchart showing the above-described processing procedure in the image forming apparatus 100 according to the present embodiment. Since the control timing and the like are as described above, the description thereof is omitted. The processing procedure shown below is a processing procedure after “APC_MODE” once becomes “mode1”.

  First, the timing generation unit 709 designates a target channel whose light amount is to be controlled (step S1401). The number of channels increases from '1' to '40' in order. If the previous channel is “40”, “1” is designated as the next channel.

  Then, the timing generation unit 709 outputs the designated channel as APC_CH (step S1402). As output destinations, a selector 702, an enable signal generation unit 707, a selector 706, a SW calculation unit 423, a GAVD 200, and the like are used. Thereby, the selector 702 acquires the target value of the designated channel from the chi target value register 701_i.

  Next, the subtractor 703 acquires a monitor voltage indicating the measured light amount (step S1403). Thereafter, the subtractor 703 and the adder 704 calculate the beam-specific current correction value DEVi based on the acquired monitor voltage, the APC target value of the corresponding channel, and the like (step S1404). Since the specific calculation method has been described above, a description thereof will be omitted.

  Thereafter, the chi register 705_i is updated with the calculated beam-specific current correction value DEVi at the timing when the enable signal is input (step S1405).

  Then, the beam-specific current correction value DEVi stored in the chi register 705_i is output to the GAVD 200 (step S1406). Thereafter, the process starts again from step S1401.

  On the other hand, the enable signal generation unit 806 of the SW calculation unit 423 determines whether or not the input APC_CH is 'ch40' (step S1431). If it is determined that APC_CH is not 'ch40' (step S1431: No), the process waits until APC_CH becomes 'ch40'.

  If the enable signal generation unit 806 determines that APC_CH is 'ch40' (step S1431: Yes), it determines whether “APC_MODE” is “mode1” (step S1432). If it is determined that “mode1” is not present (step S1432: NO), the process starts again from step S1431.

  When the enable signal generation unit 806 determines that “APC_MODE” is “mode1” (step S1432: Yes), the enable signal generation unit 806 outputs the enable signal at the high level at the timing when “CTL_EN” is at the high level. Accordingly, the subtractor 803 and the adder 804 calculate the common supply current value Isw based on the input beam-specific current correction values DEVi and the like of all the channels, and the SW register 805 uses the calculated common supply current value Isw. Is updated (step S1433).

  Then, the common supply current value Isw stored in the SW register 805 is output to the GAVD 200 (step S1434). Thereafter, the process starts again from step S1431.

  Then, the GAVD 200 receives the beam-specific current correction value DEVi calculated from the DEV calculation unit 422 (step S1451).

  Next, the GAVD 200 inputs the common supply current value Isw calculated from the SW calculation unit 423 (step S1452).

  Then, the GAVD 200 controls the laser beam based on the beam-specific current correction value DEVi and the common supply current value Isw (step S1453).

  In the sheet-to-sheet APC mode of the image forming apparatus 100 according to the present embodiment, the calculation process of the beam-specific current correction value DEVi and the common supply current value Isw is repeated. Thereby, the light quantity of each laser beam can be controlled.

(1) Factory Setting The image forming apparatus 100 according to the present embodiment performs photoelectric conversion when each channel of the VCSEL 208 irradiates a laser beam with a specified light amount on a surface of a photosensitive drum (not shown) at the time of factory shipment. The value of the monitor voltage by the element 218 is stored in the ROM area of the memory 412 as shown in FIG.

  In the measurement performed at the time of shipment, an optical sensor is arranged at a position corresponding to the surface of the photosensitive drum, and a correlation with the amount of laser beam on the surface of the photosensitive drum is acquired. This optical sensor is connected to a personal computer (hereinafter referred to as a PC). In addition, the PC controls the GAVD 200, and a factory adjustment start signal is sent from the PC to the drive current calculation unit 204 via the GAVD 200.

  The microcontroller 401 first turns on an operation enable signal of a channel (ch1) for factory adjustment via the GAVD 200, and then gradually increases the initial drive current Iswi. When the optical sensor detects that the light amount of the laser beam of ch1 has reached the set light amount, it notifies the PC. The PC that has received the notification notifies the microcontroller 401 via the GAVD 200 that the laser beam light amount of ch1 has reached the set light amount. Upon receiving the notification, the microcontroller 401 records the output voltage Vpd1 of the photoelectric conversion element 218 in the ROM area of the memory 412 at that time. The above-described processing is repeated until 40ch recording is performed, and when 40ch recording ends, the PC calculates an average value Isw_A of Isw1 to Isw40 and writes it in the ROM area of the memory 412. Thereby, an appropriate initial value is set at the time of shipment.

(2) Image Initialization Processing Device Operation After the image forming apparatus 100 is assembled with the photosensitive drum and shipped to the user, the initialization operation is executed at the time of start-up or operation start. In this embodiment, when APC_MODE = “init”, the channel 1 in the DEV operation unit 422 is micro-programmed according to the Vpd 1 to Vpd 40 of each channel registered in the ROM area of the memory 412 as the factory setting. Set by the controller 401 (when the light amount different from the lighting light amount at the time of factory setting is set as the target value, the target value is calculated and set by performing proportional calculation of Vpd1 to Vpd40 in the microcontroller 401).

  Further, the microcontroller 401 sets the initial value of the common supply current value Isw in the SW register 805 based on the initialization current Isw_A 506 stored in the ROM area of the memory 412. (When the gain of the multiplier 807 is Gsw, the value set in the SW register 805 is the common supply current value Isw / Gsw. If the light quantity different from the factory setting is set as the target value, further proportional calculation is performed. Is set by the microcontroller 401). In the ch1 register 705_1 to the ch40 register 705_40, a set value that is ± 0% of the set value of the beam-specific current correction value DEV is set.

  In this state, if the apc_enable signal is validated by a command from the CPU, APC_MODE shifts to “mode 0”, and APC control is performed by the timing signal shown in FIG. As a result of the feedback calculation in the drive current calculation unit 204, the influence of variations among the channels of the VCSEL 208, temperature characteristics, changes with time of characteristics, and the like are corrected, and a control value corresponding to the target value is obtained.

  Thereafter, APC_MODE shifts to “mode 1” through the “hold” mode. In that case, APC control is performed by the timing signal shown in FIG. 13, and the feedback calculation is continued. This state is maintained until the image forming operation starts.

(3) Image Forming Operation The image forming apparatus 100 starts the image forming operation using the beam-specific current correction value DEVi determined by the initialization operation. In the image forming operation, an electrostatic charge is imparted on the photosensitive drum, an electrostatic latent image is formed by exposure with a semiconductor laser, and conventional processing including development with toner, transfer, fixing, and discharge of printed matter may be used. it can.

  At the start of image formation, apc_fgate input from GAVD 200 is at a high level. Accordingly, the APC mode control unit 708 shifts APC_MODE to “mode2”. As shown in FIG. 13, in “mode 2”, the line APC control is performed and only the correction of the beam current correction value DEVi is performed. That is, if a large correction of the laser beam light amount is performed during image formation as line APC control, an image defect occurs. For this reason, the APC control during image formation is only the correction of the beam-specific current correction value DEVi, which is the light amount control for each channel, and the common supply current value Isw is not corrected. That is, as shown in FIG. 13, REG_SW_EN is always set to the LOW level in “mode 2” so that the value stored in the SW register 805 is not updated.

  The image forming apparatus 100 according to the present embodiment pays attention to the fact that when the VCSEL 208 is applied, the light amount control technique used in the conventional semiconductor laser is simply extended and applied. It was made. In other words, the VCSEL 208 effectively utilizes the characteristic that the VCSEL 208 emits a large number of laser beams rather than the conventional light quantity control technique for a semiconductor laser, thereby reducing the circuit scale and adjusting the volume resistance without adjusting the volume resistance. Light quantity management can be performed efficiently.

  Further, the image forming apparatus 100 according to the present embodiment calculates the drive current correction value of each laser beam of the VCSEL 208 and then drives the laser beam of the VCSEL 208 with the corrected drive current level to set the light amount. Latent image formation is executed. If the correction value cannot be set, the upper limit value or the lower limit value of the correction range is temporarily assigned, and the image formation is continuously executed until the subsequent sheet timing without stopping the image formation process in the image formation process. . For this reason, even if the light quantity of a specific semiconductor laser element falls outside the control range, the influence on the latent image formation can be minimized.

  Furthermore, in the image forming apparatus 100 according to the present embodiment, the APC control unit 402 notifies the CPU 400 that the second light amount correction has been completed in the inter-sheet APC mode. The image forming apparatus receives the notification that the correction of the beam-specific current correction value DEVi and the common supply current value Isw has been completed, and starts the next image forming process. That is, the amount of light for all the laser beams of the VCSEL 208 can be controlled by correcting the beam-specific current correction value DEVi and the common supply current value Isw, so that the increase in the inter-paper timing time can be minimized.

  In addition, by registering the channel of the semiconductor laser element outside the control range acquired during the first light intensity correction, it is possible to further shorten the paper interval timing, resulting in high-speed printing. It becomes possible to cope with.

  As described above, the image forming apparatus 100 according to the present embodiment uses the synchronization signal and the inter-paper signal to minimize the influence on the latent image formation and optimizes the multiple laser beams emitted from the VCSEL 208. Enables effective light quantity control.

  Furthermore, the image forming apparatus 100 according to the present embodiment can achieve good image formation without significantly affecting the latent image formation while minimizing the circuit scale and maintenance cost.

  In the image forming apparatus 100 according to the present embodiment, the drive current calculation unit 204 includes a first feedback system in which the DEV calculation unit 422 calculates the beam-specific current correction value DEVi based on the input monitor signal, and the beam-specific calculation. The SW calculation unit 423 includes a second feedback system that calculates the common supply current value Isw based on the current correction value DEVi. As a result, it is possible to minimize the influence of an increase in the inter-paper timing due to the light amount correction for many laser beams at the inter-paper timing.

  Further, in the image forming apparatus 100 according to the present embodiment, since the calculation control is performed by the above-described feedback system using the beam-specific current correction value DEVi and the common supply current value Isw, the linearity of the detection system / drive system (detection circuit) , Linearity of the A / D converter 202, linearity of the D / A converter in the drive system) can be reduced, and the cost of each element constituting the control system can be reduced. It is.

  For this reason, the image forming apparatus 100 according to the present embodiment can achieve good image formation without significantly affecting the latent image formation while minimizing the circuit scale and the maintenance cost.

  The image forming apparatus 100 according to the present embodiment controls the common supply current value Isw only in the inter-paper APC mode, and in the line APC mode, corrects only the beam-specific current correction value DEVi, thereby controlling the control amount during the image forming period. It is possible to control so as not to greatly change. As a result, it is possible to form a good image without significantly affecting the latent image formation.

  In the line APC mode, the image forming apparatus 100 according to the present embodiment controls the current correction value DEVi for each beam to suppress variations between channels, and thus has a significant influence on latent image formation. And good image formation is possible.

  Note that the image forming program executed by the image forming apparatus 100 of the present embodiment is provided by being incorporated in advance in a ROM or the like.

  The image forming program executed by the image forming apparatus 100 of the present embodiment is a file in an installable or executable format, and is a CD-ROM, flexible disk (FD), CD-R, DVD (Digital Versatile Disk). For example, the program may be recorded on a computer-readable recording medium.

  Furthermore, the image forming program executed by the image forming apparatus 100 of the present embodiment may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. . Further, the image formation executed by the image forming apparatus 100 of the present embodiment may be configured to be provided or distributed via a network such as the Internet.

  The image forming program executed by the image forming apparatus 100 according to the present embodiment may have a module configuration including the above-described units (drive current calculation units) as software modules. In this case, in the image forming apparatus 100, when the CPU (processor) reads the image forming program from the ROM and executes it, the above-described units are loaded on the main storage device, and the drive current calculation unit is generated on the main storage device. Become so.

  In the above embodiment, the image forming apparatus according to the present invention is described by taking an example in which the image forming apparatus is applied to a multifunction machine having at least two functions among a copy function, a printer function, a scanner function, and a facsimile function. The present invention can be applied to any image forming apparatus such as a printer, a scanner apparatus, and a facsimile apparatus.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 102 Optical apparatus 102a, 102e Reflection mirror 102b f (theta) lens 102c Polygon mirror 104a, 106a, 108a, 110a Photosensitive drum 104b, 106b, 108b, 110b Charger 104c, 106c, 108c, 110c Developer 112 Image formation part 114 Intermediate transfer belt 114a, 114b, 114c Conveying roller 118 Secondary transfer belt 120 Fixing device 122 Transfer unit 124 Image receiving material 130 Fixing member 132 Printed product 200 GAVD
202 A / D converter 204 Drive current calculator 206 Driver 208 VCSEL
210 Coupling optical element 212 Half mirror 214 Total reflection mirror 216 Second condenser lens 218 Photoelectric conversion element 220 Synchronization detection device 401 Microcontroller 402 APC control unit 403 IF control unit 411 calculation unit 412 memory 421 register memory 422 DEV calculation unit 423 SW calculation unit 701_1 to 701_40 Target value register 702 Selector 703 Adder 703 Subtractor 704 Adder 705_1 to 705_40 chi register 706 Selector 707 Enable signal generation unit 708 APC mode control unit 709 Timing generation unit 710_1 to 710_40 Multiplier 801 Unit 802 Target value register 803 Subtractor 804 Adder 805 SW register 806 Enable signal generation unit 807 Multiplier

JP 2007-021826 A JP 2005-161790 A

Claims (8)

A light source that outputs a first laser beam and a second laser beam;
The first laser beam output from the light source is separated into a third laser beam for measuring the amount of light and a fifth laser beam for scanning the photoconductor, and output from the light source. Separating means for separating the second laser beam into a fourth laser beam for measuring the amount of light and a sixth laser beam for scanning the photosensitive member;
Measuring means for measuring light amounts of the third laser beam and the fourth laser beam;
Photoelectric conversion means for outputting a voltage corresponding to the measured light amounts of the third laser beam and the fourth laser beam;
The light quantity of the first laser beam based on the voltage of the third laser beam output by the photoelectric conversion means according to the timing signals of the first laser beam and the second laser beam generated during one scan A second beam-specific correction value for controlling the light amount of the second laser beam based on the voltage of the fourth laser beam output by the photoelectric conversion means, First calculating means for calculating
Based on the first beam-specific correction value and the second beam-specific correction value, a second common current value indicating a drive current value common to the first laser beam and the second laser beam is calculated. A calculation means;
The first beam-specific correction value and the second beam-specific correction value calculated by the first calculation means during the first image formation, and the second image immediately before the first image formation. Based on the first current beam correction value calculated by the second calculation means based on the first beam specific correction value and the second beam specific correction value calculated during formation , the first laser beam And a control means for controlling the amount of light of the second laser beam during the one scan,
An image forming apparatus comprising: The first calculating means calculates the first beam-specific correction value and the second beam-specific correction value using a first feedback system;
The second calculating means calculates the common current value using a second feedback system;
The image forming apparatus according to claim 1. The second calculation means calculates the common current value only after printing on an arbitrary recording paper and before printing on the next recording paper,
The image forming apparatus according to claim 1, wherein: Repeating the calculation of the beam-specific correction value by the first calculation means and the calculation of the common current value by the second calculation means;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The second calculating means calculates a current value required for the first laser beam indicated by the first beam-specific correction value and a second laser beam indicated by the second beam-specific correction value. Calculating an average value of necessary current values as the common current value;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The second calculating means applies a current value required for the first laser beam indicated by the first beam-specific correction value and a second laser beam indicated by the second beam-specific correction value. Calculating an average value of a maximum value and a minimum value of necessary current values as the common current value;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The first calculation means is a timing after printing on an arbitrary recording paper and before printing on the next recording paper, and a timing of scanning the paper in the main scanning direction during printing. Calculating the beam-specific correction value;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Storage means for storing an initial value of the common current value and an initial value of the beam-specific correction value;
The control means further controls the amount of light for each laser beam using the initial value of the common current value stored in the storage means and the initial value of the correction value for each beam,
The measurement means uses the first laser beam and the second laser beam whose light amounts are controlled by the control means, and uses the third laser beam and the fourth laser separated by the separation means. Measuring the light intensity of the beam,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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