JP5550219B2 - Optical scanning device - Google Patents

Description

  The present invention relates to an optical scanning device used for an image forming apparatus or the like.

  First, the basic operation of the optical scanning device will be described with reference to FIG. In the optical scanning device 200, the light beam generated from the laser 202 passes through the collimator lens 203, the cylinder lens 204, and the beam shaping slit 210 and enters the rotating polygon mirror 205. The light beam reflected by the polygon mirror passes through the fθ lens 206 and the condensing lens 207, and moves on the photosensitive drum 208 that rotates in the sub-scanning direction as a photosensitive member provided in the image forming apparatus (the axis of the photosensitive drum 208). Direction). By repeating this series of operations, an electrostatic latent image is formed on the photosensitive drum.

  Further, in order to obtain a stable image quality, it is necessary to reduce the light amount fluctuation during the scanning on the photosensitive drum 208 of the laser 202 as much as possible. Further, in the optical scanning device 200 using a plurality of lasers (multi-beams) as light sources, it is necessary to perform light quantity stability control (APC) for each of the plurality of lasers.

  Further, when APC is performed, since the laser is forced to emit light in order to measure the amount of light, it is necessary to perform APC in a non-image area (area where the photosensitive drum is not exposed) so as not to expose the photosensitive drum.

However, even when APC is performed in a non-image area, the laser beam of the laser 202 reflected by the polygon mirror 205 is irradiated onto the optical box wall 600 of the optical scanning device 200 as shown in FIG. Reaches the photosensitive drum 208 (that is, the image area). The reflected light from the optical box wall 600 forms a streak-like image on the photosensitive drum 208, which causes a reduction in image quality . This streak-like image is called a ghost.

  In order to prevent a ghost from being generated, for example, Patent Document 1 discloses an invention that “a laser is not emitted at an image height at which a ghost is generated”.

  For example, Patent Document 2 discloses an invention in which an antireflection film is provided on an optical box wall.

In addition to conventional APC, bias APC is performed to improve the response speed characteristics of the laser. In the bias APC, a bias current (for the purpose of improving the response speed characteristics of the laser, is a current for slightly emitting light even in the OFF state, and the light emission state at this time is called a bias light emission state) becomes a constant value. The purpose is to control. Even when the bias APC is executed, the laser is forced to emit light, and the bias current value is determined by calculation based on the current value at that time. In general, the amount of laser forced light emission when performing bias APC is smaller than that when performing APC.
JP-A-3-268958 JP-A-5-40236

  However, in recent years, it has become necessary to perform APC for each of a plurality of lasers as the number of beams increases for the purpose of increasing the scanning speed, so the time for performing APC in a non-image area has increased. . Furthermore, since the bias APC for improving the response speed characteristic of the laser is further performed for each of the plurality of lasers, the time for performing the APC in the non-image region is increasing more and more.

  The amount of laser forced light emission at the time of bias APC execution is less than that at the time of execution of APC. However, since the same PD sensor as at the time of execution of APC is used, the same control time as APC is required. Become. Further, since the same PD sensor is used, it cannot be executed simultaneously with APC.

  That is, in an optical scanning device that performs APC and bias APC for one laser, the time for performing APC in a non-image area is increasing as compared with an optical scanning device that does not perform this.

  For the above reason, while the time required for APC and bias APC increases, as in Patent Document 1, it is not possible to emit light at a specific image height as a countermeasure against ghost. Implementation is difficult because the region is finite in time. For example, if laser APC is not performed at a specific image height as a ghost countermeasure, the light quantity control that should be performed for each line in a multi-beam optical scanning device is divided and performed once every several lines. As a result, there arises a problem that the light quantity accuracy of the laser is lowered.

  Moreover, even if an antireflection film is provided on the optical box wall to prevent the occurrence of ghosts, there is a problem that the cost increases.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide an optical scanning device that maintains the light quantity accuracy of a laser and reduces the amount of ghost generation without increasing the cost.

The present invention, in order to achieve the above object, those having the structure below.

(1) A light source having a plurality of lasers , a rotary polygon mirror that scans a photosensitive member with a laser beam emitted from the light source, a detection unit that detects a light emission amount of the laser, and a laser that emits light. A first light amount control for controlling the light amount of the laser beam to a first light amount based on a detection result of the detection unit, and a light amount of the laser beam lower than the first light amount based on the detection result of the detection unit Control means for executing second light quantity control for controlling to the second light quantity in a non-image forming period in which the laser beam does not scan the photoconductor, and the control means is configured to perform the control in the non-image forming period. the Rukoto are sequentially emitting time division multiple lasers, a plurality of laser light scanning apparatus for performing the first light amount control and the second light quantity control for each of the control hand It is wherein the predetermined period of the non-imaged period ghost the photoreceptor occurs, executes the second light amount control without executing the first light quantity control by executing the first light quantity control An optical scanning device.

  According to the present invention, even when a ghost is generated due to light emission in a non-image area, an optical scanning device that reduces the amount of ghost generation without reducing the light amount accuracy and without increasing the cost is realized. Is possible.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 1 is a schematic diagram showing a block configuration of an optical scanning device 200 for realizing the present invention.

It consists of four laser diodes (303A, 303B, 303C, 303D), a PD sensor 304, a laser driver 302, and a CPU 301 . The operation is described below.

  The CPU 301 outputs control signals (LDA control signal, LDB control signal, LDC control signal, LDD control signal) for controlling the four laser diodes (303A, 303B, 303C, 303D) to the laser driver 302. .

  The control modes that can be realized by the above-described control signals are the APC mode as the light quantity control means, the bias APC mode as the bias light quantity control means, the bias light emission mode for improving the response speed characteristic, and the electrostatic latent image on the photosensitive drum. Are four types of data emission modes. The description regarding these modes will be described later.

  The laser driver 302 emits light from the four laser diodes (303A, 303B, 303C, and 303D) based on the control signals (LDA control signal, LDB control signal, LDC control signal, and LDD control signal) input from the CPU 301. Control. Further, when the control signal input from the CPU 301 is in the APC mode or the bias APC mode, the laser driver 302 refers to the input current from the PD sensor 304 that detects the light emission amount, and sets the light emission amounts of the four laser diodes to a constant value. Control to be.

  Here, the four laser diodes (303A, 303B, 303C, and 303D) are formed on the same semiconductor chip and are edge-emitting lasers that incorporate the PD sensor 304, but the surface that includes the PD sensor outside the semiconductor chip. A light emitting laser may be used.

  FIG. 2 is a diagram showing the relationship between the bias light amount (light amount in a state where light is emitted slightly before light emission), the bias APC light amount, and the current of the APC light amount. The horizontal axis represents current and the vertical axis represents light quantity, and the laser emission characteristics are plotted. In this embodiment, the bias APC light quantity is assumed to be a quarter of the APC light quantity. The light emission amount of the bias light emission is a very small value obtained by calculation from the bias APC light amount. For example, as shown in the figure, 80% of the current value Ibapc when the laser is forced to emit light by bias APC is obtained by calculation, and this value is used as the bias current Ib.

  FIG. 3 is a diagram for explaining the operations of the laser driver 302 in the bias emission mode, APC mode, bias APC mode, and data emission mode. Since the operation of the four laser diodes is the same in each mode, the laser diode A (303A, hereinafter referred to as laser A) will be described here.

  First, the operation when the laser A is controlled in the bias emission mode will be described with reference to FIG. In FIG. 3A, the bias emission mode is described as BIAS for simplification.

  When the laser driver 302 is set to the bias emission mode at time t0, the laser A emits bias light from the extinguished state. The bias light amount at the time of bias emission is a constant light amount obtained by calculation from the bias APC light amount for the purpose of improving the response speed characteristic of the laser, and is a very small value. Then, after a predetermined time, when the bias emission mode is terminated at time t1, the laser A is turned off again.

  Hereinafter, it is assumed that the laser A emits bias light at times other than the APC mode, the bias APC mode, and the data light emission mode, which will be described later.

  Subsequently, an operation when the laser A is controlled in the APC mode will be described with reference to FIG.

  When the laser driver 302 is set to the APC mode at time t0, the laser A emits light forcibly from the bias emission state. Based on the current value generated by the PD sensor 304 that detects the light emission amount, the light amount control is performed so that the light amount of the laser A becomes a constant APC light amount. Then, after a certain time, the APC mode is terminated at time t1. The fixed time (t1-t0) in this case is arbitrarily determined, but it is desirable to set a value sufficient for the laser A light amount to converge to the APC light amount (a constant value). When the APC mode is finished, the laser A again enters the bias emission state.

  Next, the operation when the laser A is controlled in the bias APC mode will be described with reference to FIG. In FIG. 3C, the bias APC mode is described as BAPC for simplification.

  When the laser driver 302 is set to the bias APC mode at time t0, the laser A emits light forcibly from the bias emission state. Based on the current value generated by the PD sensor 304, the light amount control is performed so that the light amount of the laser A becomes a constant bias APC light amount. The bias APC light amount is generally smaller than the APC light amount. Therefore, in this embodiment, the bias APC light quantity is assumed to be a quarter of the APC light quantity. Then, after a certain time, the bias APC mode is terminated at time t1. In this case, the fixed time (t1-t0) is arbitrarily determined, but it is desirable to set a value sufficient for the light amount of the laser A to converge to the bias APC light amount (a constant value). When the bias APC mode is terminated, the laser A again enters the bias emission state.

  Next, the operation when the laser A is controlled in the data emission mode will be described with reference to FIG. In FIG. 3D, the data emission mode is described as DATA for simplification. This is a mode for forming an electrostatic latent image on a photosensitive member by a laser.

  When the laser driver 302 is set to the data emission mode at time t0, when the image data is “0”, the laser A is in the bias emission state, and when the image data is “1”, the laser A is in the bias emission state. The data emission state starts. The data emission amount at this time is the same as the APC light amount.

  In FIG. 3D, since the image data is “0”, the bias emission state is set. If the image data becomes “1” at time t1, the laser A changes from the bias emission state to the data emission state. When the image data becomes “0” at time t2, the laser A changes from the data emission state to the bias emission state. When the data emission mode ends at time t3, the laser A is in a bias emission state as it is.

  The operations of the laser driver 302 in the bias emission mode, APC mode, bias APC mode, and data emission mode are as described above.

  FIG. 4 is a diagram showing, in a time chart, control using the above-described four modes for control when there is an image height at which a ghost occurs in the image area in the present embodiment.

  Four laser diodes (303A: Laser A, 303B: Laser B, 303C: Laser C, 303D: Laser D) are shown on the vertical axis, and the horizontal axis is the time axis.

  In this embodiment, the time t0 to the time t9 is one period (one scan in the main scanning direction on one surface of the polygon mirror), and the time t5 to the time t6 is an image section. After time t9, one scanning in the main scanning direction on the next surface of the polygon mirror is shown and is the second cycle. Further, as a section G1 in which a ghost is generated when light is emitted from time ta to time tb, it is indicated by a dense left-down diagonal line in FIG.

  The time at which ghost occurs is known in advance by measurement at the time of assembling the apparatus, and therefore does not change with time during image formation.

<Control when there is an image height where ghost occurs>
Hereinafter, a control flowchart of the CPU 301 in the case where there is an image height at which a ghost occurs according to the present embodiment will be described with reference to FIG.

<S100>
“Start of first cycle, t = t0”
In S100, the first cycle operation is started from time t0.

<S101>
“Laser A APC started”
Since APC needs to be executed in a time-sharing manner, at time t0, the CPU 301 enters the APC state of the laser A, the laser driver 302 sets the laser A to the APC mode, and starts the APC of the laser A.

<S102>
“T = t1?”
The control of the CPU 301 shifts to S102, and the state of S101 is repeated until the time reaches t1. Then, after a predetermined time (as described above, it is desirable to set a value sufficient for the light amount of the laser A to converge to a constant APC light amount), at time t1, the control of the CPU 301 shifts to S103.

<S103>
"Laser A APC ends, Laser B APC starts"
The APC of the laser A is terminated and the APC of the laser B is started. Here, the laser driver 302 sets the laser A to the bias emission mode and sets the laser B to the APC mode.

<S104>
“T = t2?”
The control of the CPU 301 shifts to S104, and the state of S103 is repeated until the time reaches t2. Then, after a certain time, at time t2, the control of the CPU 301 shifts to S105.

<S105>
"Laser B APC ends, Laser C APC starts"
The APC of the laser B is terminated and the APC of the laser C is started. Here, the laser driver 302 sets the laser B to the bias emission mode and sets the laser C to the APC mode.

<S106>
“T = t3?”
The control of the CPU 301 shifts to S106, and the state of S105 is repeated until the time reaches t3. Then, after a certain time, at time t3, the control of the CPU 301 shifts to S107.

<S107>
“Laser C ACP ends, Laser A BACP starts”
The APC of the laser C is terminated, and the bias APC (denoted as BAPC in the drawing) of the laser A is started. Here, the laser driver 302 sets the laser C to the bias emission mode and sets the laser A to the bias APC mode. If APC is executed sequentially, the APC of the laser C should be terminated and the APC of the laser D should be started at time t3. However, since the time ta to the time tb is a time interval in which a ghost occurs, the bias APC is intentionally performed. As described above, the bias APC light amount is a quarter of the APC light amount. For this reason, when the bias APC is executed, it is possible to reduce the amount of ghost generation compared to the case where the APC is executed.

<S108>
“T = t4?”
The control of the CPU 301 shifts to S108, and the state of S107 is repeated until the time reaches t4. Further, after a certain time, at time t4, the control of the CPU 301 shifts to S109.

<S109>
"Laser A BAPC ends, Laser B BAPC starts"
The bias APC of the laser A is terminated, and the bias APC of the laser B is started. Here, the laser driver 302 sets the laser A to the bias emission mode and sets the laser B to the bias APC mode. From time ta to time tb is a time when a ghost occurs, bias APC is also performed here. At time tb, the time when the ghost is generated ends. At this time, since the laser B is still executing the bias APC, the laser driver 302 does not switch the control signal. As described above, it is desirable that the time for executing the bias APC is set to a value sufficient for the light amount to converge to the bias APC light amount. Similarly, it is desirable that the time for executing APC is set to a value sufficient for the light amount to converge to the APC light amount.

<S110>
“T = t5?”
The control of the CPU 301 shifts to S110, and the state of S109 is repeated until the time reaches t5. Then, after a certain time, at time t5, the control of the CPU 301 shifts to S111.

<S111>
“Laser B BAPC ends and lasers A, B, C, D start DATA”
The bias APC of the laser B is terminated and image formation is started. Here, the laser driver 302 sets the laser A, laser B, laser C, and laser D to the data emission mode.

<S112>
“T = t6?”
The control of the CPU 301 shifts to S112, and the state of S111 is repeated until the time reaches t6. Then, after a certain time, at time t6, the control of the CPU 301 shifts to S113.

<S113>
“Laser A, B, C, D DATA ends, Laser D APC starts”
Data emission of laser A, laser B, laser C, and laser D is terminated, and APC of laser D is started. Here, the laser driver 302 sets the laser A, laser B, and laser C to the bias emission mode, and sets the laser D to the APC mode.

<S114>
“T = t7?”
The control of the CPU 301 shifts to S114, and the state of S113 is repeated until the time reaches t7. Then, after a certain time, at time t7, the control of the CPU 301 moves to S115.

<S115>
“Laser D ACP ends, Laser C BAPC begins”
The APC of the laser D is terminated and the bias APC of the laser C is started. Here, the laser driver 302 sets the laser D to the bias emission mode and sets the laser C to the bias APC mode.

<S116>
“T = t8?”
The control of the CPU 301 shifts to S116, and the state of S115 is repeated until the time reaches t8. Then, after a certain time, at time t8, the control of the CPU 301 proceeds to S117.

<S117>
"Laser C BAPC ends, Laser D BAPC starts"
The bias APC of the laser C is terminated, and the bias APC of the laser D is started. Here, the laser driver 302 sets the laser C to the bias emission mode and sets the laser D to the bias APC mode.

<S118>
“T = t9?”
The control of the CPU 301 shifts to S118, and the state of S117 is repeated until the time reaches t9. Then, after a certain time, at time t9, the control of the CPU 301 shifts to S119.

<S119>
“End of first cycle operation”
The first cycle ends. Then, the bias APC of the laser D is terminated, and the APC of the laser A is started again. Here, the laser driver 302 sets the laser D to the bias emission mode and sets the laser A to the APC mode.

  Thereafter, the same operation as in the first cycle is repeated.

  As described above, when a plurality of lasers are controlled in a time-sharing manner, a bias APC in which the amount of emitted light is one-fourth of the amount of APC light is executed without executing APC in a section where a ghost is predicted to occur. Thus, an optical scanning device capable of reducing the influence of ghost can be realized. It is possible to realize an optical scanning apparatus that can reduce the influence of a ghost by performing bias APC preferentially in a section in which ghost occurrence is predicted and executing APC in a section in which ghost generation is not predicted.

  Note that the amount of light at the time of bias light amount control is not limited to the value shown in the above example because it varies depending on the performance of the laser driver.

  Next, an embodiment will be described in which when there are a plurality of image heights where a ghost occurs, the bias light amount control means is executed with priority given to an image height having a high ghost intensity.

  FIG. 6 is a diagram showing a time chart corresponding to the case where there are a plurality of image heights where a ghost occurs in the present embodiment. As in the first embodiment, the vertical axis represents four laser diodes (303A: laser A, 303B: laser B, 303C: laser C, 303D: laser D), and the horizontal axis represents the time axis.

  Further, time t0 to time t9 is one cycle, and time t5 to time t6 is an image section. In addition, in FIG. 6, a dense left-downward oblique line indicates a section G1 in which a strong ghost is generated when light is emitted from time ta to time tb and from time tc to time td. Further, as a section G2 in which a weak ghost is generated when light is emitted from time te to time tf, it is shown by a rough left-down diagonal line in FIG.

  The time and intensity at which a ghost occurs is known in advance by measurement at the time of assembling the apparatus, and therefore does not change with time during image formation.

  Accordingly, when there are a plurality of image heights where a ghost occurs in a non-image area as in this time, the present invention is preferentially applied to the time ta to time tb and the time tc to time td when a strong ghost occurs. Are two sections. That is, the bias APC is executed in two sections from time ta to time tb and time tc to time td where a strong ghost occurs. It does not apply to the interval from time te to time tf when a weak ghost occurs.

<Control when there are multiple image heights that generate ghosts>
Below, the control flowchart of CPU301 implemented in a present Example is demonstrated using FIG.

<S150>
“Start of first cycle, t = t0”
First, in S150, the first cycle operation is started from time t0.

<S151>
“Laser A APC started”
Since APC needs to be executed in a time-sharing manner, first, the CPU 301 enters an operation start state at time t0, the laser driver 302 sets the laser A to the APC mode, and starts APC of the laser A.

<S152>
“T = t1?”
And control of CPU301 transfers to S152 and repeats the state of S151 until time becomes t1. Then, after a predetermined time (as described above, it is desirable to set a value sufficient for the amount of the laser A to converge to the APC light amount), the control of the CPU 301 shifts to S153 at time t1.

<S153>
“Laser A APC ends, Laser C BAPC begins”
The APC of the laser A is terminated and the bias APC of the laser C is started. Here, the laser driver 302 sets the laser A to the bias emission mode and includes the ta to tb section in which a strong ghost is generated, so the laser C is set to the bias APC mode.

<S154>
“T = t2?”
And control of CPU301 transfers to S154 and repeats the state of S153 until time becomes t2. Then, after a certain time, at time t2, the control of the CPU 301 shifts to S155.

<S155>
"Laser C BAPC ends, Laser D BAPC starts"
The bias APC of the laser C is terminated, and the bias APC of the laser D is started. Here, the laser driver 302 sets the laser C to the bias light emission mode and also sets the laser D to the bias APC mode because it is in the ta to tb section where a strong ghost is still generated.

<S156>
“T = t3?”
And control of CPU301 transfers to S156 and repeats the state of S155 until time becomes t3. Then, after a certain time, at time t3, the control of the CPU 301 proceeds to S157.

<S157>
“Laser D BAPC ends, Laser A BAPC begins”
The bias APC of the laser D is terminated and the bias APC of the laser A is started. Here, the laser driver 302 sets the laser D to the bias emission mode and includes the tc to td period in which a strong ghost is generated, so the laser A is set to the bias APC mode.

<S158>
“T = t4?”
And control of CPU301 transfers to S158 and repeats the state of S157 until time becomes t4. Further, after a certain time, at time t4, the control of the CPU 301 shifts to S159.

<S159>
"Laser A BAPC ends, Laser B BAPC starts"
The bias APC of the laser A is terminated, and the bias APC of the laser B is started. Here, the laser driver 302 sets the laser A to the bias light emission mode, and the laser B is set to the bias APC mode because it is still in the tc to td section where a strong ghost is generated.

<S160>
“T = t5?”
And control of CPU301 transfers to S160 and repeats the state of S159 until time becomes t5. Then, after a certain time, at time t5, the control of the CPU 301 shifts to S161.

<S161>
“Laser B BAPC ends and lasers A, B, C, D start DATA”
The bias APC of the laser B is terminated and image formation is started. Here, the laser driver 302 sets the laser A, laser B, laser C, and laser D to the data emission mode.

<S162>
“T = t6?”
Then, the control of the CPU 301 shifts to S162, and the state of S161 is repeated until the time reaches t6. Then, after a certain time, at time t6, the control of the CPU 301 shifts to S163.

<S163>
Laser A, B, C, D DATA ends, Laser B APC starts "
Although the data emission of laser A, laser B, laser C, and laser D is terminated and the te to tf section where a weak ghost is generated is included, since the BAPC has already ended, the APC of laser B is started. Here, the laser driver 302 sets the laser A, laser C, and laser D to the bias emission mode, and sets the laser B to the APC mode.

<S164>
“T = t7?”
And control of CPU301 transfers to S164 and the state of S163 is repeated until time becomes t7. Then, after a certain time, at time t7, the control of the CPU 301 shifts to S165.

<S165>
"Laser B APC ends, Laser C APC starts"
The APC of the laser B is terminated and the APC of the laser C is started. Here, the laser driver 302 sets the laser B to the bias emission mode and sets the laser C to the APC mode.

<S166>
“T = t8?”
And control of CPU301 transfers to S166 and repeats the state of S165 until time becomes t8. Then, after a certain time, at time t8, the control of the CPU 301 shifts to S167.

<S167>
"Laser C APC ends, Laser D APC starts"
The APC of the laser C is terminated and the APC of the laser D is started. Here, the laser driver 302 sets the laser C to the bias emission mode and sets the laser D to the APC mode.

<S168>
“T = t9?”
Then, the control of the CPU 301 shifts to S168, and the state of S167 is repeated until the time reaches t9. Then, after a certain time, at time t9, the control of the CPU 301 shifts to S169.

<S169>
“End of first cycle operation”
The first cycle ends. Then, the APC of the laser D is terminated, and the APC of the laser A is started again. Here, the laser driver 302 sets the laser D to the bias emission mode and sets the laser A to the APC mode.

  Thereafter, the same operation as in the first cycle is repeated.

  As described above, when performing light intensity control in a time-sharing manner for a plurality of lasers, even if there are multiple image heights where ghosts occur, the ghost light is controlled by giving priority to the image height where the ghost intensity is high. An optical scanning device capable of effectively reducing the influence of the above can be realized.

  Note that the amount of light at the time of bias light amount control is not limited to the value shown in the above example because it varies depending on the performance of the laser driver. Bias APC is preferentially performed in a section where the ghost intensity is predicted to be large, and APC is preferentially executed in a section where the ghost intensity is not predicted. In addition, when APC is not executed for all the lasers in a section where the ghost intensity is not predicted, the influence of the ghost can be reduced by executing APC in a section where the ghost intensity is predicted to be small. An optical scanning device can be realized.

  Note that the amount of light at the time of bias light amount control is not limited to the value shown in the above example because it varies depending on the performance of the laser driver.

The figure which showed the block configuration of the optical scanning device for implement | achieving this invention Bias light quantity, bias APC light quantity, diagram showing the relationship between APC light quantity and current (A) Diagram showing the operation of the laser diode when controlled in the bias emission mode, (b) Diagram showing the operation of the laser diode when controlled in the APC mode, (c) When controlled in the bias APC mode The figure which showed operation of a laser diode, (d) The figure which showed operation of a laser diode at the time of controlling in data emission mode Time chart executed in the first embodiment CPU control flowchart executed in the first embodiment Time chart executed in the second embodiment CPU control flowchart executed in the second embodiment The figure which showed the composition of the optical scanning device Figure showing reflection of optical box wall

Explanation of symbols

202 Laser 205 Polygon mirror 208 Photosensitive drum (corresponding to photoconductor)
301 CPU (corresponding to light quantity control means and bias light quantity control means)
302 Laser driver 303A Laser diode A
303B Laser diode B
303C Laser diode C
303D Laser diode D
304 PD sensor 600 Optical box wall

Claims (3)

A light source having a plurality of lasers ;
A rotating polygon mirror that scans the photosensitive member with a laser beam emitted from the light source;
Detecting means for detecting the light emission amount of the laser;
A first light amount control for causing the laser to emit light and controlling a light amount of the laser beam to a first light amount based on a detection result of the detection unit; and a light amount of the laser beam based on a detection result of the detection unit. Control means for executing a second light amount control for controlling the second light amount lower than the first light amount in a non-image forming period in which the laser beam does not scan the photoconductor;
With
The control means, wherein the Rukoto are sequentially fire when dividing the plurality of laser in the non-image forming period, the plurality of laser each for the first light level control and an optical scanning device for performing the second light quantity control of the Because
The control means performs the second light amount control without executing the first light amount control during a predetermined period within the non-image forming period in which a ghost is generated on the photoconductor by executing the first light amount control. The optical scanning device characterized by performing. Wherein said control means includes an optical scanning apparatus according to claim 1, characterized in that said first amount of light at the first light level control and data amount of light emission. Said control means, based on said second amount of light at the second light level control, the optical scanning apparatus according to claim 1, wherein the determining the bias light quantity.

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