JP4510645B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a function of forming an image on a recording medium such as a sheet, for example, a printer, a copying machine, a facsimile machine, and the like. The present invention relates to uniformizing the amount of exposure light in an image forming apparatus.

Conventionally, as an image forming apparatus of this type, a UFS (underfilled scanner) system in which a surface of a rotating polygon mirror (hereinafter referred to as a polygon mirror) is wide with respect to an incident light beam width is frequently used in a laser scanning optical system. As the speed of image forming apparatuses has increased, UFS has a large polygon mirror, so temperature rise and noise have become problems. As a countermeasure, there is a small OFS (overfilled scanner, see FIGS. 15 and 16) of a polygon mirror proposed in Patent Document 1. Since OFS has a narrow polygon mirror surface relative to the incident beam width and is smaller than UFS, heat generation and noise can be kept low, the start-up is quick, and the spot diameter can be reduced. Excellent in high definition.
JP-A 49-84518

  However, in the case of the prior art as described above, the following problems have occurred. As shown in FIGS. 15 and 16, OFS irradiates the photosensitive drum using a part of the luminous flux. Therefore, the width of the reflected luminous flux varies depending on the angle at which the laser is incident on the polygon mirror 401. As a result, on the photosensitive drum surface. The amount of laser light applied to the laser beam is not uniform in the main scanning direction. Specifically, as shown in FIG. 17, in the OFS system, there is a problem that the amount of laser light is reduced by about 5 to 25% on the end side with respect to the central portion.

  As a countermeasure against such a light amount unevenness in the main scanning direction, for example, as proposed in Japanese Patent Laid-Open No. 63-53043, information for correcting the light amount unevenness is stored in a ROM. When the scanned light beam is applied to the photosensitive drum by a method that controls the laser drive current so that the laser drive current is lowered when the photoconductor is irradiated in the central part of the main scanning direction and is increased when the edge is irradiated. In addition, there is a method of reducing the amount of light irradiated to the central portion of the photosensitive drum.

  However, in order to cause the semiconductor laser to emit light with a predetermined amount of light, it is necessary to adjust the drive current according to the ambient temperature, and it is necessary to increase the drive current due to deterioration over time. Therefore, the amount of drum surface light can be corrected as shown in FIG. 18 (a) only by using the above method, or the correction may be insufficient as shown in FIG. is there.

  As a result, density unevenness occurred in the printed image, and a high quality image could not be obtained.

  The present invention has been made under such circumstances. Even when the overfilled scanner system is employed, the semiconductor laser can be placed on the image bearing member (photosensitive drum) even if the semiconductor laser deteriorates with time or changes in environmental temperature. It is an object of the present invention to provide an image forming apparatus that can perform exposure with a uniform amount of light in the main scanning direction, suppress occurrence of density unevenness in a printed image, and obtain a high-quality image.

In order to solve the above problems, in the present invention, the image forming apparatus is configured as described in the following (1) and (2) .

(1) A laser beam emitted from a semiconductor laser light emitting element is scanned by a rotary polygon mirror that reflects a surface narrower than the incident beam width to expose the image carrier, and an electrostatic latent image is formed on the image carrier. Laser exposure means to perform,
Image forming means for transferring a toner image obtained by developing the electrostatic latent image formed on the image carrier by the laser exposure means by a developing means to a transfer material ;
In the image forming apparatus in which the width of the light beam reflected by the incident angle of the incident light beam on the narrow surface is larger than the end portion in the center portion in the main scanning direction of the laser beam .
Correction information for correcting the light quantity of the reflected laser beam in accordance with the position in the main scanning direction of laser beam scanning, wherein the laser driving current is reduced in the central portion in the main scanning direction as compared with the end portion. A memory storing predetermined correction information for correcting the light amount of the reflected laser beam;
Current varying means for changing a laser driving current based on the predetermined correction information read from the memory in synchronization with a synchronization signal representing a scanning position of the laser beam;
A light amount monitoring means for monitoring the light amount of the laser beam;
A first laser drive for driving the semiconductor laser so as to obtain a first predetermined light amount by monitoring the light amount when the decrease amount is set to zero and the semiconductor laser light emitting element emits light by the light amount monitor means. The current is set, the amount of decrease is set to the maximum, and the amount of light when the semiconductor laser light emitting element emits light is monitored by the light amount monitoring means, and the semiconductor laser is adjusted so that the second predetermined amount of light is obtained. Control means for setting a second laser drive current to be driven,
The current variable means changes the laser drive current between the first laser drive current and the second laser drive current set by the control means based on the correction information. Forming equipment.
(2) The laser beam emitted from the semiconductor laser light emitting element is scanned by a rotary polygon mirror that reflects on a surface narrower than the incident light beam width to expose the image carrier, and an electrostatic latent image is formed on the image carrier. Laser exposure means to perform,
Image forming means for transferring a toner image obtained by developing the electrostatic latent image formed on the image carrier by the laser exposure means by a developing means to a transfer material;
In the image forming apparatus in which the width of the light beam reflected by the incident angle of the incident light beam on the narrow surface is larger than the end portion in the center portion in the main scanning direction of the laser beam.
Correction information for correcting the light quantity of the reflected laser beam in accordance with the position in the main scanning direction of laser beam scanning, wherein the laser driving current is reduced in the central portion in the main scanning direction as compared with the end portion. A memory storing predetermined correction information for correcting the light amount of the reflected laser beam;
Current varying means for changing a laser driving current based on the predetermined correction information read from the memory in synchronization with a synchronization signal representing a scanning position of the laser beam;
A light amount monitoring means for monitoring the light amount of the laser beam;
In order to adjust the degree of change of the laser drive current when the correction information is changed, the amount of decrease when the amount of decrease is set to a first amount of decrease and the semiconductor laser light emitting element emits light is monitored by the light amount monitor. The first laser drive current for driving the semiconductor laser is set so that the first predetermined amount of light is monitored, and the amount of decrease is larger than the first amount of decrease. The amount of light when the semiconductor laser light emitting element is caused to emit light is set to a decrease amount of 2 and monitored by the light amount monitoring means, and a second laser driving current for driving the semiconductor laser is set so as to be a second predetermined light amount. An image forming apparatus comprising: a control unit configured to set the image forming apparatus.

  According to the present invention, it is possible to irradiate an image carrier (photosensitive drum) with a laser beam with a uniform amount of light even when the semiconductor laser is deteriorated with time or changed in environmental temperature. As a result, even in an image forming apparatus using an overfilled scanner type scanner, it is possible to expose the image carrier with a uniform amount of light in the main scanning direction, suppressing occurrence of density unevenness in the printed image, and high-quality images. Can be obtained.

  The best mode for carrying out the present invention will be described in detail with reference to an embodiment of an image forming apparatus.

  FIG. 1 is a circuit block diagram illustrating a calibration loop for light amount correction, which is related to the main part of the “image forming apparatus” according to the first embodiment. Details will be described later.

  FIG. 2 is a block diagram of the entire image forming apparatus according to the present exemplary embodiment. The video controller 101 receives print information from a host computer (not shown), develops it into bitmap image data 110 by an image development unit, and stores it in a page memory (not shown). The image output control unit sends the image data 110 to the printer engine 102 based on the horizontal synchronizing signal (BD signal 308) and the vertical synchronizing signal (TOP signal 112) sent from the printer engine 102. In addition, the video controller 101 and the printer engine 102 regularly transmit and receive information via the serial communication line 113.

  Next, the print sequence will be described with reference to the schematic configuration diagram of the printer engine shown in FIG. When printing the image data 110 from the controller 101 on the first surface (front surface) of the recording medium conveyed from the paper feeding unit 209 (flow in the I direction), the registration roller 202 removes the skew of the recording medium. A TOP sensor 117 for detecting the leading edge of the recording medium is disposed at the same position as the registration roller 202, and at the same time as removing the skew, the printer engine 102 indicates that the leading edge of the recording medium has reached a predetermined position. CPU 2 (not shown) recognizes. Thereafter, before the image data is recorded on the recording medium, the recording medium is attracted to the electrostatic transport belt 208 by the attracting roller 203 and transported.

  On the other hand, the laser scanners 115C, 115Y, 115M, and 115K drive the laser drive circuits 116C, 116Y, 116M, and 116K in the laser scanners for the respective colors based on the image data sent from the video controller 101 to the printer engine 102. As a result, toner images are formed on the photosensitive drums 204 to 207 of the respective colors, transferred onto the recording medium, fixed on the recording medium by the fixing device 210, and discharged to the outside through the paper discharge roller 211. Is done.

  FIG. 4 shows the timing for the TOP sensor output signal 123, the serial communication line 113, the TOP signal 112, and the image data 110-K, 110-M, 110-Y, and 110-C. When the TOP sensor output signal 123 becomes HIGH, it indicates that the leading edge of the recording medium has reached a predetermined position. The CPU 2 sends a TOP signal 112, which is a synchronization signal for the video controller 101 to send out the C color image data 110-C, to the video controller 101 after T (tc) time from the rising edge of the TOP sensor output signal 123. Send it out. As shown in FIG. 3, the video controller 101 must send the image data 110 in consideration of the time difference for the recording medium to reach the photosensitive drums 204 to 207 of the respective colors.

  FIG. 5 is a diagram showing the transmission timing of image data in the horizontal scan direction. The BD-C, BD-Y, BD-M, and BD-K signals in the figure are horizontal synchronization signals and are generated every time one line is printed. The video controller 101 sends the image data 110 at a predetermined time Tbd from the rising edge of the BD signal, and performs printing at a predetermined position from the left end edge of the recording medium.

  FIG. 1 is a block diagram showing the relationship between the laser drive circuits 116C, 116Y, 116M, and 116K and the control board that controls them. Reference numeral 1 denotes a control board having a CPU 2, from which a control signal for controlling each laser driving board is transmitted. The laser drive circuit 116 includes a light amount correction circuit 301, a VI conversion circuit 306, a laser driver IC 4, a semiconductor laser 6, and a buffer circuit 3 for the light amount monitor.

  Next, the operation of the laser drive circuit 116 will be described. As will be described later, the light amount correction circuit 301 has a nonvolatile memory that stores profile information for correcting light amount unevenness on the photosensitive drum surface in the main scanning direction scan, and stores the memory in synchronization with the horizontal synchronization signal 308. Read and converted to analog voltage as described below. Then, it is converted into a current value Id by the subsequent VI conversion circuit 306 and output to the laser driver IC 4.

  The laser driver IC 4 performs control by switching between the current IL flowing through the semiconductor laser 6 to emit light or the dummy resistor 5 to turn off the light according to the VDO image signal 110. The laser current value IL passed through the laser 6 is a current IL obtained by subtracting the current Id output from the VI conversion circuit 306 from the current Ia set by the constant current circuit 10. The current Ia flowing through the constant current circuit 10 is set so that the light quantity monitoring photodetector 7 of the semiconductor laser has a desired light quantity. A method for setting the current Id output from the VI conversion circuit will be described later.

  A serial communication signal 307 is transmitted and received from the CPU 2 of the control board 1 to the light amount correction circuit 301 to determine an operation mode of the light amount correction circuit 301. Further, the detection result of the photodetector 7 that performs laser light amount monitoring is sent to the A / D port of the CPU 2 via the buffer circuit 3. The value of the volume resistor 8 is adjusted so that it is input to the laser driver IC 4 as a desired voltage when the laser emits a predetermined amount of light during factory assembly.

  As described above, the laser drive current IL is obtained by subtracting the current Id output from the VI conversion circuit 306 from the current Ia necessary for emitting light with a desired light amount, so that the laser can be used in any case. The drive current IL does not flow more than Ia. Therefore, it is possible to prevent a laser failure due to light emission exceeding the rated light amount.

  FIG. 6 is a block diagram of the light amount correction circuit 301. 304 is a nonvolatile memory, 303 is a circuit for writing / reading the contents of the nonvolatile memory, 302 is a memory read circuit that reads the contents of the nonvolatile memory 304 in synchronization with the BD signal 308, and 305 is multi-value data output from the nonvolatile memory 304 A DA converter 306 for D / A conversion, and a VI conversion circuit 306 for converting the analog voltage signal 312 output from the DA converter 305 into a current value 313. The DA converter 305 converts the voltage between the analog voltage signals 309 and 310 output from the external CPU 2 into a voltage with 8-bit resolution. The rewriting of the nonvolatile memory 304 and the memory read condition (read speed, etc.) are determined by changing the set values of the circuit 303 and the memory read circuit 302 by serial communication from the CPU 2.

  7 is a graph showing the current and light quantity characteristics of the semiconductor laser 6, FIG. 8 is a timing chart showing the relationship between the DAC 305 and the laser light quantity, and FIG. 9 is a process for determining the reference voltages 309 and 310 of the DAC 305 of the light quantity correction circuit 301. It is the flowchart which showed.

  The current IL necessary for emitting a predetermined amount of light with the semiconductor laser varies depending on the ambient temperature and aging deterioration. A graph 15 in FIG. 7 is an example of a current-light amount graph in a low temperature environment, and a graph 16 is an example of a current-light amount graph in a high temperature environment. That is, in order to emit light with the predetermined light amount Papc, the current IL indicated by the point A is sufficient in the low temperature environment, but the current IL indicated by the point B is necessary in the high temperature environment.

  In this embodiment, as shown in the conventional example, in a scanner in which the light amount on the drum surface in the main scanning direction is high at the center of the image, the laser current IL is gradually decreased toward the center of the image, so that the drum The amount of light on the surface is made uniform.

  FIG. 8 is a time chart showing that the laser current IL is reduced toward the center of the image. As shown in the figure, in synchronization with the BD signal 308, data 320 for correcting the unevenness in the drum surface light amount is read from the nonvolatile memory, converted to an analog voltage value 312 by the DAC 305, and then converted into an analog voltage value 312 by the subsequent VI conversion circuit 306. It is converted into current 313. The Id current 313 is input to the laser driver IC4 and suppresses the laser current IL. Therefore, the laser current attenuates toward the center of the image as indicated by the laser current IL in FIG. As a result, the laser light amount output from the semiconductor laser 6 is a diagram in which the central portion of the image is attenuated as shown in FIG. For example, if the input of the DAC 305 is set to FFh and the light amount is set to be reduced by 50%, the input is reduced by 25% at 80h. By performing this processing in a scanner in which the drum surface light amount increases by 25% in the center of the image, the light amount on the drum surface becomes a uniform irradiation light amount as shown in FIG.

  Next, a process for determining the reference voltages 309 and 310 of the DAC 305 of the light amount correction circuit 301 will be described with reference to the flowchart of FIG.

  First, 0 V is set to VrefL310 (S1), and the input value to the DAC 305 is set to 00h (S2). In this state, the laser driver IC 4 of the laser driving circuit 116 performs adjustment APC (abbreviation of Auto Power Control) of the laser light amount (S3). This APC is an operation for determining the laser current IL so as to obtain a desired light amount while monitoring the photodetector 7 incorporated in the semiconductor laser. As described above, when the input value to the DAC 305 is set to 00h, the output current Id of the VI conversion circuit 306 is 0 mA. Therefore, the set current Ia at the time of APC execution is the same as the laser current IL. Then, the voltage sensed by the photodetector 7 when the light is emitted with this APC light quantity (Papc in FIG. 7) (the voltage obtained by converting the current generated by the photodetector with the variable resistor 8) is stored (S4). Next, the target value of the voltage of the photodetector 7 is determined from the amount (50% in FIG. 7) that the amount of light is desired to be reduced during FFh of the DAC 305 (S6), and FFh is set as the input value of the DAC 305 (S7). Then, VrefH is increased from 0V (S8), compared with the voltage sensed by the photodetector 7 (S9), and when the voltage value determined in S6 is reached, the increase in VrefH is stopped and the voltage value is stored. VrefH309.

  When the characteristic of the semiconductor laser 6 is the graph 15 of FIG. 7, the current difference ΔI (L) between the point A and the point B can be adjusted with a resolution of 8 bits, and the characteristic of the semiconductor laser 6 is the graph 16 of FIG. In this case, the current difference ΔI (H) between the points C and D can be adjusted with 8-bit resolution.

  Next, the light amount adjustment in the printing operation will be described with reference to FIG. In the nonvolatile memory 304 (FIG. 6), a profile of the drum surface light amount is measured when the laser scanner is assembled, and a correction value is stored so that the laser light amount is uniform on the drum surface. For example, as shown in FIG. 8, when the value input from the non-volatile memory to the DAC 304 is 80 h at the center of the image, that is, when it is necessary to reduce the amount of light by 25% with respect to the amount of light at the edge of the image, VI conversion The output current Id of the circuit is maximum at the center of the image as indicated by 313. On the other hand, the laser current IL has the lowest profile at the center of the image, and the light emission amount of the laser has a profile that is reduced by 25% in the center of the image. As a result, the amount of drum surface light is uniform at the center and the edge of the image, and high-quality printing without density unevenness is possible.

  The adjustment of Vref is preferably performed every time the power is turned on, when returning from the sleep mode, or every predetermined number of printed sheets during continuous printing. Alternatively, it may be performed only when the power is turned on.

  Alternatively, the nonvolatile memory 304 may be a RAM, and correction data may be loaded into the RAM from the control board 1 when the power is turned on.

  As described above, according to the present embodiment, when the power is turned on or when returning from the sleep mode, the light quantity measurement is performed by the light quantity monitor for each predetermined number of printed sheets, and the light emission quantity to be corrected stored in the memory. By adjusting the correction current value based on this information and the correction current amount of the laser drive current, even if there is a deterioration of the semiconductor laser over time or an environmental temperature change, the photosensitive drum is irradiated with a laser beam with a uniform amount of light. Is possible.

  In the second embodiment, a modification of setting the reference voltages VrefH and VrefL of the DAC 305 will be described.

  FIG. 10 is a circuit block diagram illustrating a feedback loop for calibration of light amount correction according to this embodiment. In the first embodiment, the reference voltages 309 and 310 for the light quantity correction circuit are sent from the CPU 2, but not sent from the CPU 2 in the present embodiment. Other than the above, the second embodiment is the same as the first embodiment.

  FIG. 11 shows an internal block diagram of the light amount correction circuit 321. As shown in the drawing, the reference voltages VrefH309 and VrefL310 sent to the DAC 305 are generated by the reference voltage generators 322 and 323 in the previous stage. The reference voltage generation units 322 and 323 have registers therein and are set by serial communication 307 with the CPU 2. The internal register is composed of 8 bits. For example, the reference voltage generators 322 and 323 perform D / A conversion with a resolution of 8 bits between the power supply voltage 5V and the GND potential 0V, and the voltages of VrefH309 and VrefL310 are converted. To decide. Reference numeral 324 denotes a low-pass filter, and smoothing the DAC output 312 and making a voltage transition smoothly enables smoother light quantity correction.

  Next, a process for determining the reference voltages 309 and 310 of the DAC 305 of the light amount correction circuit 321 will be described with reference to the flowchart of FIG.

  First, 00h is set in the register in the reference voltage generation unit 323, VrefL310 is set to 0V (S21), and then the input value to the DAC 305 is set to 00h (S22). In this state, the laser driver IC 4 of the laser driving circuit 116 performs adjustment APC of the laser light amount (S23). This APC is an operation for determining the laser current IL so as to obtain a desired light amount while monitoring the photodetector 7 incorporated in the semiconductor laser. As described above, when the input value to the DAC 305 is set to 00h, the output current Id of the VI conversion circuit 306 is 0 mA. Therefore, the set current Ia at the time of APC execution is the same as the laser current IL. Then, the voltage sensed by the photodetector 7 when the light is emitted with this APC light quantity (Papc in FIG. 7 of Embodiment 1) (the voltage obtained by converting the current generated by the photodetector into a voltage by the variable resistor 8) is stored (S24). Next, the target value of the voltage of the photodetector 7 is determined from the amount (50% in FIG. 7) that the amount of light is desired to be reduced during the FFh of the DAC 305 (S26), and FFh is set as the input value of the DAC 305 (S27). Then, the register in the reference voltage generator 322 is increased from 00h (VrefH is 0V) to FFh (VrefH is 5V) (S28), and compared with the voltage sensed by the photodetector 7 (S29). When the voltage value determined in S26 is reached, the increase in VrefH is stopped, the register value at that time is stored, and the voltage of VrefH309 is determined.

  Also in this embodiment, when the characteristic of the semiconductor laser 6 is the graph 15 in FIG. 7, the current difference ΔI (L) between the point A and the point B can be adjusted with a resolution of 8 bits. In the case of the graph 16 of FIG. 7, the current difference ΔI (H) between the point C and the point D can be adjusted with 8-bit resolution, as in the first embodiment.

  In this embodiment, since the DAC 305 and the reference voltage generation units 322 and 323 are arranged in the vicinity, the VrefH 309 and the VrefL 310 are not easily influenced by external noise, and a stable output of the DAC 305 is obtained. Can be stabilized.

  Further, by making the light amount correction circuit 321 a one-chip IC, the DAC output and the laser light amount can be further stabilized.

  Further, as shown in FIG. 10, it is possible to reduce signal lines between the control board 1 and the laser drive circuit 116, and it is also possible to reduce the number of ports of the CPU 2 and the number of cable cores.

  In the third embodiment, a modification example in which a multi-beam laser is used, for example, a two-beam laser is used will be described. When a two-beam laser is used, the profile to be corrected differs depending on the characteristics of each laser. For this reason, the light amount correction circuit requires two nonvolatile memories.

  FIG. 13 shows an internal block diagram of the light amount correction circuit 351. The basic configuration is the same as that of the second embodiment, and each laser beam circuit is required.

  FIG. 14 is a time chart showing that the laser current IL is reduced toward the center of the image by the light amount correction circuit 351 of FIG. As shown in the figure, the BD signal 308 has two pulses for each line, the first for the first laser and the second for the second laser. Data 320 and 350 for correcting the unevenness of the drum surface light amount are read from the nonvolatile memories 304 and 334 in synchronization with the respective BDs, converted into analog voltage values 312 and 342 by the DACs 305 and 335, and the subsequent VI conversion Circuits 306 and 336 convert the currents to 313 and 343, respectively. Since the nonvolatile memories 304 and 334 store information for correcting unevenness of the drum surface light amount of each beam, the DAC output voltages 312 and 342 have different shapes and corrected light amount values as shown in FIG. Therefore, the laser drive current IL of each beam is different as shown in FIG. 14, and as a result, the amount of laser emission is also different. Thus, by correcting the laser light emission amount in the main scanning direction, the drum surface light amount becomes uniform for each beam.

  In this embodiment, a description is given by preparing a memory having correction data for each beam and performing light quantity correction. However, the average value of the profile of each beam is stored in one memory, and one memory read is performed. The content of the memory may be read by a circuit, and the light amount correction may be performed on each beam. Since the characteristics of each beam in a single chip package are not greatly different, and the phase difference (light emitting point distance) of each beam is very close to a few dots, this method is sufficiently effective for correction. There is.

  As described above, according to the present embodiment, in the image forming apparatus having a multi-beam laser element, the memory means for storing the light amount correction information for each beam and the laser drive current value based on the read correction information. Is provided with current varying means for varying in the main scanning direction, so that different corrections can be made for each beam.

FIG. 3 is a circuit block diagram illustrating a calibration loop for light amount correction in the first embodiment. Configuration diagram of entire apparatus according to Embodiment 1 Sectional drawing showing the paper conveyance path in Example 1 3 is a time chart showing image signal transmission timing in the sub-scanning direction in the first embodiment. Time chart showing image signal transmission timing in the main scanning direction in Embodiment 1 Block diagram of a light amount correction circuit in the first embodiment Graph showing current-light quantity characteristics of semiconductor laser Time chart showing light amount correction in the main scanning direction in Embodiment 1 Calibration flowchart according to the first embodiment Circuit block diagram showing a feedback loop of calibration for light amount correction in the second embodiment Block diagram of a light amount correction circuit in the second embodiment Calibration flowchart in the second embodiment Block diagram of a light amount correction circuit in Embodiment 3 Time chart showing light amount correction in the main scanning direction in Embodiment 3 Explanatory drawing of irradiation to polygon mirror in conventional example Explanatory drawing of irradiation to polygon mirror in conventional example The figure explaining the irradiation light amount nonuniformity on the photosensitive drum surface in a prior art example The figure explaining the irradiation light quantity nonuniformity correction on the photosensitive drum surface in a prior art example

Explanation of symbols

2 CPU
301 Light quantity correction circuit 302 Memory read circuit 304 Non-volatile memory 305 DA converter 306 VI conversion circuit 307 Serial communication 308 BD signal 401 Polygon mirror

Claims (8)

Laser exposure that scans a laser beam emitted by a semiconductor laser light emitting element with a rotary polygon mirror that reflects a surface narrower than the incident beam width, exposes the image carrier, and forms an electrostatic latent image on the image carrier Means,
Image forming means for transferring a toner image obtained by developing the electrostatic latent image formed on the image carrier by the laser exposure means by a developing means to a transfer material ;
In the image forming apparatus in which the width of the light beam reflected by the incident angle of the incident light beam on the narrow surface is larger than the end portion in the center portion in the main scanning direction of the laser beam .
Correction information for correcting the light quantity of the reflected laser beam in accordance with the position in the main scanning direction of laser beam scanning, wherein the laser driving current is reduced in the central portion in the main scanning direction as compared with the end portion. A memory storing predetermined correction information for correcting the light amount of the reflected laser beam;
Current varying means for changing a laser drive current based on the predetermined correction information read from the memory in synchronization with a synchronization signal representing a scanning position of the laser beam;
A light amount monitoring means for monitoring the light amount of the laser beam;
A first laser drive for driving the semiconductor laser so as to obtain a first predetermined light amount by monitoring the light amount when the decrease amount is set to zero and the semiconductor laser light emitting element is caused to emit light. In addition to setting the current, the amount of decrease is set to the maximum and the light amount when the semiconductor laser light emitting element emits light is monitored by the light amount monitor means, and the semiconductor laser is adjusted so as to have a second predetermined light amount. Control means for setting a second laser driving current to be driven,
The current variable means changes the laser drive current between the first laser drive current and the second laser drive current set by the control means based on the correction information. Forming equipment. The image forming apparatus according to claim 1.
The laser exposure means is a multi-beam system having a first semiconductor laser light emitting element and a second semiconductor laser light emitting element, and the memory corresponds to each of the first semiconductor laser light emitting element and the second semiconductor laser light emitting element. an image forming apparatus comprising that you store the correction information as the first correction information and the second correction information. 3. The image forming apparatus according to claim 1, further comprising a constant current supply unit configured to supply a current so that a sum of a current supplied by the current variable unit and the laser driving current becomes a predetermined current. . 2. The correction information is information for indicating a laser driving current having a current value between a current value of the first laser driving current and a current value of the second laser driving current. 4. The image forming apparatus according to any one of items 1 to 3 . The image forming apparatus according to any one of claims 1 to 4, wherein:
An image forming apparatus, wherein the memory and the current varying means are arranged in the laser exposure means . The control means is configured to set the first laser drive current and the second laser drive based on a first reference voltage for setting the amount of decrease of zero and a second reference voltage for setting the maximum amount of decrease. The image forming apparatus according to claim 1, wherein an electric current is set . The image forming apparatus according to claim 6, wherein the current varying unit includes a setting unit that sets the first reference voltage and the second reference voltage . Laser exposure that scans a laser beam emitted by a semiconductor laser light emitting element with a rotary polygon mirror that reflects a surface narrower than the incident beam width, exposes the image carrier, and forms an electrostatic latent image on the image carrier Means,
  Image forming means for transferring a toner image obtained by developing the electrostatic latent image formed on the image carrier by the laser exposure means by a developing means to a transfer material;
  In the image forming apparatus in which the width of the light beam reflected by the incident angle of the incident light beam on the narrow surface is larger than the end portion in the center portion in the main scanning direction of the laser beam.
  Correction information for correcting the light quantity of the reflected laser beam in accordance with the position in the main scanning direction of laser beam scanning, wherein the laser driving current is reduced in the central portion in the main scanning direction as compared with the end portion. A memory storing predetermined correction information for correcting the amount of the reflected laser beam;
  Current varying means for changing a laser driving current based on the predetermined correction information read from the memory in synchronization with a synchronization signal representing a scanning position of the laser beam;
  A light amount monitoring means for monitoring the light amount of the laser beam;
  In order to adjust the degree of change of the laser drive current when the correction information is changed, the amount of decrease when the amount of decrease is set to a first amount of decrease and the semiconductor laser light emitting element emits light is monitored by the light amount monitor. The first laser drive current for driving the semiconductor laser is set so that the first predetermined amount of light is monitored, and the amount of decrease is larger than the first amount of decrease. The amount of light when the semiconductor laser light emitting element is caused to emit light is set to a decrease amount of 2 and monitored by the light amount monitoring means, and a second laser driving current for driving the semiconductor laser is set so as to be a second predetermined light amount. An image forming apparatus comprising: a control unit configured to set the image forming apparatus.