JP2007192967A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multibeam optical scanner in which an automatic power control (APC) of a plurality of light sources can be achieved without increasing the speed of APC. <P>SOLUTION: The multibeam optical scanner draws a picture by scanning a photoreceptor with light beams emitted from a plurality of laser diodes LD1 to LD4 and has an optical power controller OPC which performs APC for automatically controlling the light intensity of the respective laser diodes, wherein the optical power controller performs APC for each light source with weak light intensity Vref which do not form a latent image on the photoreceptor in scanning the margin and the non-scanned regions of the photoreceptor and controls the each of the light sources to have drawing light intensity obtained by superimposing predetermined light intensity Va on the weak light intensity in scanning the drawing region of the photoreceptor. Thus, the time of APC for the each of laser diodes can be extended without causing a fog on the margin region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical scanning apparatus that performs drawing by scanning a light beam such as a laser beam, and more particularly to an optical output control apparatus having a function of performing APC (auto power control) on the light intensity of the light beam.

  In an optical scanning apparatus that performs drawing using a light beam such as a laser beam, for example, a laser scanning apparatus, it is necessary to control the light intensity of the laser beam to a predetermined intensity in order to obtain drawing with a desired density. For this control, an optical output control device having an APC function is used. In this APC, a laser beam emitted from a light source such as a laser diode is received by a light receiving element such as a photodiode to monitor the light intensity, and the laser diode is set so that the light intensity of the monitored laser light becomes a preset reference value. The drive current to be supplied to is feedback controlled.

  FIG. 1 is a block diagram of this type of laser scanning apparatus, which is applied to, for example, a laser printer. The laser beam LB emitted from the laser diode 11 in the laser light source block 1 and shaped by the beam shaping means 12 is deflected and scanned within a predetermined angle range by the polygon mirror 2 that rotates at high speed, and the laser beam LB that has been deflected and scanned is scanned. Main scanning is performed on the photosensitive surface of the photosensitive drum 4 that is axially rotated in the sub-scanning direction through the fθ lenses 3a and 3b. A synchronizing signal generating photodiode (hereinafter referred to as a synchronizing photodiode) 5 is disposed on the scanning optical path of the laser beam LB. The laser beam LB to be deflected and scanned is received and photoelectrically converted. A signal is output, and this light reception signal is used as the main scanning timing signal. By scanning the photosensitive surface of the photosensitive drum 4 with the laser beam LB and simultaneously controlling on / off of the light emission of the laser diode 11, a latent image having a required pattern is formed on the photosensitive surface. The latent image is developed with toner, and the developed image is transferred and fixed on a sheet to execute laser printing.

Here, as shown in the schematic diagram of FIG. 7, in the main scanning of the laser beam LB, the timing region for scanning the photosensitive drum 4 with the laser beam LB is called a scanning region, and the other timing regions are non-scanning regions. Called. Further, even in the scanning area, an area in which drawing on both sides in the scanning direction when being transferred to the paper is not performed is referred to as a front margin area and a rear margin area, and an area in which drawing is performed surrounded by these margin areas is referred to as a drawing area. . In this type of laser scanning device, in order to realize the APC described above, a monitoring photodiode (hereinafter referred to as a monitoring photodiode) that receives laser light emitted from the laser diode 11 (not shown in the figure). ). Then, in the timing region where the image data in the image signal does not exist, that is, in the non-scanning region as shown in FIG. 9A, the synchronization signal (horizontal synchronization) obtained by the synchronization photodiode 5 as shown in FIG. Signal) sets one period of main scanning by the laser beam LB, and APC is executed in the non-scanning region in the main scanning of one period as shown in FIG. In this APC, the light intensity of the laser diode is monitored by a monitoring photodiode, and the drive current supplied to the laser diode is feedback controlled based on the monitored light intensity to control the light intensity of the laser diode to a predetermined value. . Therefore, a predetermined light intensity can be obtained when drawing in the scanning area by the laser beam, and drawing with a constant density can be realized. As a laser scanning device provided with such a light output control device having an APC function, for example, there is one described in Patent Document 1. Further, in Patent Document 2, the white level (minimum density) and the black level (maximum density) of an image to be drawn are set by APC, respectively, so that an intermediate density gradation between the white level and the black level is obtained. A technique that enables an appropriate setting has been proposed.
JP 2003-298178 A JP-A-7-61041

  In recent years, there has been proposed a multi-beam scanning laser scanning device that realizes high speed drawing by simultaneously scanning a plurality of laser diodes for drawing. In such a light output control device of a multi-beam scanning laser scanning device, it is necessary to perform APC independently for each of a plurality of laser diodes that emit laser light. In this case, it is conceivable to provide a monitoring photodiode for each of a plurality of laser diodes and to provide a light output control device having an independent APC function for each laser diode. It is an obstacle to becoming more economical and not economical. In a multi-beam laser diode in which a plurality of laser diodes are housed in one package, the number of monitoring photodiodes is usually one or less than the number of laser diodes. APC cannot be performed at the same time. For this reason, APC of each laser diode is performed on a plurality of laser diodes in a time-sharing manner. However, when an attempt is made to perform APC multiple times within a limited timing region of the non-scanning region as shown in FIG. The APC time applied to one laser diode is shortened, and the APC is required to increase the speed. Therefore, it is necessary to use high-speed components with excellent responsiveness for each component constituting the light output control device. Since these components are expensive, the APC device or laser scanning device is expensive. Become a factor. Further, if the APC time is made too short due to the limit of characteristics such as responsiveness of the components constituting the light output control device, it becomes difficult to perform highly accurate APC.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-beam optical scanning apparatus that realizes APC for a plurality of light beams without requiring high speed for APC.

  The present invention is a multi-beam optical scanning device that performs drawing by scanning light beams emitted from a plurality of light sources on a photoconductor, and performs optical output that performs APC for automatically controlling the light intensity of the plurality of light sources. The light output control device performs APC for each of the plurality of light sources with weak light intensity that does not form a latent image on the photoconductor at the scanning timing of the blank area and the non-scanning area of the photoconductor. Each light source is controlled to a drawing light intensity obtained by superimposing a predetermined light intensity on a weak light intensity at the scanning timing of the drawing area. In this case, each light intensity of the plurality of light sources is detected by the same light receiving means, and APC of the plurality of light sources is performed at a time-division timing based on the detection output.

  According to the optical scanning device of the present invention, even at the scanning timing including not only the non-scanning area but also the blank area of the photoconductor, a plurality of light sources are time-divided in a weak light intensity state in which a latent image is not formed on the photoconductor. By performing each APC, it is possible to lengthen the time for performing APC for each of a plurality of light sources. Therefore, it is not necessary to increase the speed of APC, and it is possible to use low-cost circuit components and realize high-precision APC. . Further, since a latent image is not formed when the blank area is scanned, image fog does not occur in the blank area, and drawing quality does not deteriorate.

  In the present invention, a light receiving means for receiving light emitted from a plurality of light sources, a monitor means for comparing a detection voltage of the light receiving means with a weak light reference voltage corresponding to the weak light intensity, and a comparison output of the monitor means Light source driving means for causing a plurality of light sources to emit light with weak light intensity, superimposed voltage supply means for supplying a superimposed voltage for increasing the light intensity of each light source to the plurality of light source driving means, and operation timing of the light source driving means. Control means for controlling. In this configuration, the light scanning device of the present invention can be realized by providing the light source driving means corresponding to each of the plurality of light sources.

  Here, the monitor means includes a detection circuit that outputs a voltage detected by the light receiving means as a monitor voltage, and a comparison means that outputs the comparison voltage by comparing the monitor voltage with the weak light reference voltage. The light source driving unit emits the light source based on the holding circuit that holds the comparison voltage, the superimposing circuit that superimposes the comparison voltage that holds the superimposed voltage supplied from the superimposing voltage supply unit, and the voltage that is output from the superimposing circuit. And a driving circuit to be operated. The control means causes the image signal to operate the driving circuit at the timing of APC and the scanning timing of the drawing area, the holding signal to operate the holding circuit at the timing of APC, and the superposition by the superimposing circuit at the scanning timing of the drawing area. The superimposed signal is output. Note that the superimposed voltage supply means may be provided in common to each of the plurality of light source driving means, or may be configured to be provided independently in correspondence with the plurality of light source driving means.

  Next, Embodiment 1 of the present invention will be described with reference to the drawings. The first embodiment is applied to the laser scanning device shown in FIG. 1, and a laser beam emitted from a multi-beam laser diode 11 (to be described later) in the laser light source block 1 is converted into a laser beam LB by a beam shaping means 12, and this laser is used. The beam LB is deflected and scanned within a predetermined angle range by the polygon mirror 2 that rotates at high speed, and the laser beam LB that has been deflected and scanned is rotated on the photosensitive surface of the photosensitive drum 4 in the sub-scanning direction through the fθ lenses 3a and 3b. Main scan. A synchronizing photodiode 5 as a horizontal synchronizing sensor is disposed on the scanning optical path of the laser beam LB, and the laser beam LB to be deflected and scanned is received by being reflected by the mirror 6, and a photoelectrically received light receiving signal is received. The received light signal is used as a main scanning timing signal. Then, when the laser beam LB is scanned on the photosensitive surface of the photosensitive drum 4, by turning on / off the light emission of each laser diode of the multi-beam laser diode 11, a latent image of a required pattern is formed on the photosensitive surface. The latent image is developed with toner, and the developed image is transferred and fixed on paper or the like to perform laser printing. Here, as described with reference to FIG. 7, the scanned laser beam LB is scanned over a wider range than the region of the photosensitive drum 4 in the main scanning direction. The other area is defined as a non-scanning area. In this scanning area, the photosensitive drum 4 is physically drawn by scanning the laser beam LB over the entire length of the photosensitive surface in the main scanning direction, that is, a predetermined paper size, and a latent image is formed by this drawing. However, in order to prevent the drawn image from protruding from the paper to be transferred, a blank area is secured in each of the front and rear areas in the main scanning direction, and drawing is not performed in this blank area. I have to. An area sandwiched between the margin areas on both sides is defined as a drawing area. These blank areas can be appropriately changed according to the setting in the laser scanning device, but when the setting is changed, information such as the size of the blank area can be recognized by the control device 400 described later. ing.

  As shown in the conceptual diagram of FIG. 2, the multi-beam laser diode 11 of the laser light source block 1 includes a chip CH in which a plurality of (here, first to fourth) laser diodes are monolithically formed, and this chip CH. The monitor photodiode MPD formed on the mounted semiconductor substrate SB is housed in one package P. Each of the laser diodes LD1 to LD4 can be driven independently, and emits a laser beam when a required current is applied. In this embodiment, the laser beams emitted from the front surfaces of the laser diodes LD1 to LD4 are arranged side by side in the sub-scanning direction with respect to the photosensitive drum, and four lines are drawn in the sub-scanning direction in one main scanning. Can be executed, and the drawing speed is increased. The laser light emitted from the laser diodes LD1 to LD4 in the back direction is received by a monitoring photodiode MPD and output as a monitor voltage for detecting the light intensity of the laser light. The drive current supplied to each of the laser diodes LD1 to LD4 is independently feedback controlled based on the monitor voltage generated by the current output from the monitoring photodiode MPD, and the light of each laser diode LD1 to LD4 is controlled. Control is performed so that the intensity becomes a predetermined light intensity suitable for drawing.

  FIG. 3 is a block circuit diagram of a light output control device OPC for controlling the light emission intensity of each of the laser diodes LD1 to LD4 of the multi-beam laser diode 11, and has an APC function. The optical output control device OPC includes first to fourth LD (laser diode) drive circuits 101 to 104 corresponding to the first to fourth laser diodes LD1 to LD4 of the multi-beam laser diode 11, respectively. And one monitor circuit 200 and one superimposed voltage control circuit 300 common to the four LD drive circuits 101 to 104. Further, a control circuit 400 for controlling these circuits is provided.

  The monitor circuit 200 includes a detection resistor R connected in series with the one monitor photodiode MPD that receives the laser beams emitted from the first to fourth laser diodes LD1 to LD4, and the detection resistor. A differential amplifier 201 is provided that outputs, as a monitor voltage Vm, a voltage generated at both ends of the detection resistor R by a current flowing through R. Further, a comparator 202 is provided that compares the monitor voltage Vm output from the differential amplifier 201 with a preset weak light reference voltage Vref and outputs the difference voltage Vd. The output of the comparator 202 is input to the four LD driving circuits 101 to 104, respectively.

  Since the four LD drive circuits 101 to 104 have the same configuration, only the internal circuit configuration of one LD drive circuit 101 is shown. A sample / hold circuit 111 for sampling and holding the differential voltage Vd output from the first comparator 202 of the monitor circuit 200, and for superimposing (adding) a required superimposed voltage Va on the held voltage. The superimposing circuit 112, the voltage / current converter 113 that converts the voltage output from the superimposing circuit 112 into a driving current, and the driving current supplied to the laser diode LD1 based on image data input from the outside are turned on / off. And a driver 114 that causes the laser diode LD1 to emit light with a light intensity corresponding to the drive current supplied when the switch is turned on.

  The superposed voltage Va superposed in the superposed circuit 112 is output from a superposed voltage supply circuit 300 formed of a constant voltage source here and supplied to each superposed circuit 112 of the four LD drive circuits 101 to 104. The superimposed voltage Va will be described. FIG. 4 shows characteristics indicating the characteristics of light intensity during light emission with respect to the driving voltage input to the voltage-current converter 113 for driving the laser diode LD1, and the laser light emitted from the laser diode LD1 by the monitoring photodiode MPD. It is a figure which shows the characteristic of the monitor voltage Vm obtained when it receives light in correlation. Corresponding to the light intensity of the laser diode LD1, the light intensity at the minimum density (white level) and the light intensity at the maximum density (black level) when an image is developed on the photoreceptor are set. The monitor voltage Vm when the laser light with white level light intensity is received by the monitoring photodiode MPD is used as the weak light reference voltage Vref. Further, the superimposed voltage Va is set to a difference voltage between the black level voltage Vb when the laser diode LD1 emits light with a black level light intensity and the white level voltage Vw when light is emitted with a white level light intensity. Here, the laser diodes LD1 to LD4 are formed monolithically, and the superimposed voltage Va is set to the same voltage for each of the laser diodes LD1 to LD4. In particular, even when the characteristics of the laser diodes LD1 to LD4 are changed to different characteristics due to temperature changes or the like due to the characteristics of the semiconductor laser, the change in the differential efficiency (characteristic slope) is as shown by the phantom line in FIG. Since it can be ignored and can be considered to be limited to a change at a threshold level (moving in parallel along the horizontal axis), even if the white level voltage Vm and the black level voltage Vb change respectively, it is a difference voltage between the two level voltages. A certain superimposed voltage Va does not change and can be regarded as a constant value.

  The control circuit 400 outputs a drawing signal Svideo for turning on / off the drivers 114 of the LD driving circuits 101 to 104 in order to perform drawing by the LD driving circuits 101 to 104 at the scanning timing of the drawing area. Here, as will be understood from the following description, since the APC is executed using the drawing signal Svideo, the drawing signal Svideo is output even in the non-scanning region. Further, the control circuit 400 sequentially outputs the sample / hold signal S / H to the four LD driving circuits 101 to 104 at a required timing. As will be described later, the sample / hold signal S / H is output in the non-scanning area and the blank area in order to perform APC on the LD driving circuits 101 to 104 over the scanning timing of the non-scanning area and the blank area. Output in synchronization with the drawing signal Svideo. Further, the control circuit 400 outputs a superposition signal Add that causes the superposition operation in the superposition circuit 112 of each of the LD drive circuits 101 to 104 at the scanning timing of the drawing area.

  The operation of the optical output control device having the above configuration will be described. FIG. 5 is an operation timing chart of each circuit. As in the scanning timing shown in FIG. 7, in the scanning area, there are front and rear margin areas before and after the drawing area. Conventionally, the horizontal synchronization signal is generated in the non-scanning area to perform horizontal synchronization, and the APC is executed with the APC timing signal generated in the non-scanning area. However, in the present invention, each of the non-scanning area and the front side and the rear side is executed. An area including a margin area is set as an APC timing area, and an APC timing signal is generated in the APC timing area to perform an APC operation and a horizontal synchronization operation. The control circuit 400 sequentially executes APC for the four LD drive circuits 101 to 104 under the condition in which the APC timing area is set as described above. That is, the control circuit 400 sequentially outputs the first to fourth image signals and the first to fourth sample / hold signals S / H as the image signal Svideo in the region excluding the drawing region, APC in each of the LD drive circuits 101 to 104 is executed at the signal timing. By this APC operation, the weak photovoltage supplied to each of the laser diodes LD1 to LD4 is set in each of the LD drive circuits 101 to 104. Here, the horizontal synchronization signal is generated in a part of the second image signal, but another image signal may be used.

  FIG. 6 is a timing chart showing an APC operation of the first LD driving circuit 101 and the second driving circuit 102 among the four LD driving circuits 101 to 104. When the first image signal Svideo1 is input to the first LD driving circuit 101 and the first sample / hold signal SH1 is further input, the driver 114 is turned on in the first LD driving circuit 101. At this time, since the image signal Svideo is not inputted to each of the second to fourth LD driving circuits 102 to 104, these drivers 114 are turned off and in a non-light emitting state. Then, a weak voltage is applied to the first LD driving circuit 101 so that the first laser diode LD1 emits light with weak light. In the monitor circuit 200, light emitted from the first laser diode LD1 is received by the monitor photodiode MPD, the monitor voltage Vm is detected by the detection resistor R and the differential amplifier 201, and this is detected by the comparator 203 as weak light. Compared with the reference voltage Vref, the difference voltage Vd is output. Further, the difference voltage Vd is sampled by the sample / hold circuit 111 by the sample signal of the first hold / sample signal S / H1 from the control circuit 400, and the voltage / current converter 113 corresponds to the sampled difference voltage Vd. Current to be output and input to the driver 114. Thus, the first laser diode LD1 is supplied with a drive current corresponding to the differential voltage Vd and emits light. At this time, when the differential voltage Vd is positive, the drive current is reduced and the emission intensity of the first laser diode LD1 is reduced. When the difference voltage Vd is negative, the drive current is increased and the emission intensity is increased. As a result, APC is performed, and when APC converges, the difference voltage Vd of the first LD drive circuit 101 becomes equal to the white level voltage Vw, and the emission intensity of the first laser diode LD1 is the weak light reference voltage. The light intensity corresponding to Vref, that is, the light intensity at the white level is controlled. Thereafter, the sample / hold circuit 111 holds the white level voltage Vw by the hold signal of the first sample / hold signal S / H1 from the control circuit 400.

  Next, when the second image signal Svideo2 is input to the second LD driving circuit 102 and then the second sample / hold signal SH2 is input, the second LD driving circuit 101 turns on the driver 114. At this time, since the image signal Svideo is not input to the first, third, and fourth LD driving circuits 101, 103, and 104, these drivers 114 are turned off and are in a non-light emitting state. Then, a weak voltage is applied to the second LD driving circuit 101 so that the second laser diode LD2 emits light with weak light. In the monitor circuit 200, light emitted from the second laser diode LD2 is received by the monitor photodiode MPD, the monitor voltage Vm is detected by the detection resistor R and the differential amplifier 201, and this is detected by the comparator 203 as weak light. Compared with the reference voltage Vref, the difference voltage Vd is output. Further, the difference voltage Vd is sampled by the sample / hold circuit 111 by the sample signal of the second hold / sample signal S / H2 from the control circuit 400, and the voltage / current converter 113 corresponds to the sampled difference voltage Vd. Current to be output and input to the driver 114. Thus, the second laser diode LD1 is supplied with a drive current corresponding to the differential voltage Vd and emits light. As APC converges in the same manner as in the case of the first LD drive circuit 101, the difference voltage Vd of the second LD drive circuit 102 becomes equal to the white level voltage Vw, and the emission intensity of the second laser diode LD2 Is controlled to a weak light intensity corresponding to the weak light reference voltage Vref, that is, a white level light intensity. Thereafter, the sample / hold circuit 111 holds the white level voltage Vw by the hold signal of the second sample / hold signal S / H2 from the control circuit 400. In the second LD drive circuit 102, the white level voltage Vw is input to the voltage-current converter 113 by the second image signal Svideo2 immediately after this, and the second laser diode LD2 emits light by the weak light intensity and is leveled. A synchronization signal is obtained.

  In the following, although not shown, APC for the weak light intensity is similarly executed in the third and fourth LD drive circuits 103 and 104.

  When the first to fourth LD driving circuits 101 to 104 complete the APC to the weak light intensity with respect to LD1 to LD4 and the timing of the drawing area comes, the control circuit 400 sends the first LD driving circuits 101 to 104 to the first LD driving circuits 101 to 104, respectively. Alternatively, the fourth drawing signals Svideo1 to Svideo4 are output, and at the same time, the superimposed signal Add is output. As a result, in each of the LD driving circuits 101 to 104, the superimposed voltage Va from the superimposed voltage supply circuit 300 is superimposed on the white level voltage Vw held in the superimposing circuit 112 to become the black level voltage Vb, and this black level voltage Vb. Is converted into current by the voltage-current converter 113 and input to each driver 114. Accordingly, in each of the LD driving circuits 101 to 104, the laser diodes LD1 to LD4 are controlled to be turned on / off based on the image data of the image signals Svideo1 to Svideo4, and when turned on, the light intensity corresponding to the black level voltage Vb is obtained. Light will be emitted. As a result, all of the first to fourth laser diodes LD1 to LD4 emit light with a predetermined light intensity, and drawing on the photosensitive drum 4 is performed, so that drawing with a predetermined uniform density can be realized.

  As described above, since the APC of the first to fourth laser diodes LD1 to LD4 is performed using the non-scanning area of the main scanning of the laser scanning device and the blank areas before and after the drawing area, the conventional non-scanning is performed. Compared with the case where APC is performed only in the region, the time for performing APC can be lengthened. As a result, even when the APC of the first to fourth laser diodes LD1 to LD4 is performed in a time-sharing manner, a sufficient APC time for each laser diode can be secured, and the APC is not required to be speeded up. APC with high accuracy can be realized. Therefore, the circuit components are not expensive and the APC control is not lowered. By executing APC also in the blank area, a laser diode is emitted during APC and exposed to the photosensitive surface of the photosensitive drum. However, each laser diode emits light with a light intensity of white level. For this reason, a latent image is not formed in the margin area of the photosensitive drum, and so-called drawing fog is not generated in which drawing is performed on the margin of the paper and the margin becomes gray.

  In the above embodiment, the superimposed voltage supply circuit 300 supplies the same superimposed voltage Va to the first to fourth LD drive circuits 101 to 104, respectively, but each laser diode LD1 to LD4 is configured as an individual element. In this case, the laser diodes LD1 to LD4 may vary in the differential efficiency and threshold level characteristics. In this case, a superimposed voltage is supplied to each of the LD drive circuits 101 to 104 individually. What is necessary is just to comprise. For example, an independent superimposed voltage supply circuit is connected to each LD drive circuit, or a plurality of superimposed voltages are prepared in the superimposed voltage supply circuit. Further, the superimposed voltage of the superimposed voltage supply circuit can be varied, and the APC It is conceivable to connect each LD driving circuit in accordance with the timing of the above.

  In the above embodiment, an example of a multi-beam type laser scanning device constituted by four laser diodes has been shown. However, a multi-beam type constituted by two or more laser diodes, and the number of monitoring diodes is a laser diode. The present invention can be similarly applied to any LD driving circuit including an APC device that detects the light intensity of a plurality of laser diodes in common with a single monitoring diode.

It is a figure which shows the conceptual structure of the laser scanning apparatus with which this invention is applied. It is a figure which shows the conceptual structure of a multi-beam laser diode. It is a circuit diagram of a light output control device. It is a characteristic diagram of the voltage-light intensity of a laser diode and a photodiode. It is a timing diagram which shows the operation of APC and voltage superposition. It is a detailed timing diagram of APC and voltage superposition. It is a conceptual diagram for demonstrating the conventional APC timing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source block 2 Polygon mirror 3 f (theta) lens 4 Photosensitive drum 5 Synchronous photodiode 11 Multi-beam laser diode 101-104 LD drive circuit 200 Monitor circuit 300 Superposed voltage supply circuit 400 Control circuit LD1-LD4 Laser diode MPD Monitor photodiode OPC Light output control device Vw White level voltage Vb Black level voltage Va Superimposition voltage Vref Weak light reference voltage

Claims (8)

  A multi-beam optical scanning device that performs drawing by scanning a light beam emitted from a plurality of light sources onto a photosensitive member, and automatically controls the light intensity of the plurality of light sources. The light output control device performs APC for each of the plurality of light sources with weak light intensity that does not form a latent image on the photoconductor at the scanning timing of the blank area and the non-scanning area of the photoconductor. And an optical scanning device that controls each of the light sources so as to obtain a drawing light intensity obtained by superimposing a predetermined light intensity on the weak light intensity at the scanning timing of the drawing area of the photosensitive member.   2. The optical scanning device according to claim 1, wherein each light intensity of the plurality of light sources is detected by the same light receiving unit, and APC of the plurality of light sources is performed at a time-division timing based on the detection output.   The light output control device includes a light receiving unit that receives light emitted from the plurality of light sources, a monitor unit that compares a detection voltage of the light receiving unit with a weak light reference voltage corresponding to the weak light intensity, and the monitor A light source driving means for causing each of the plurality of light sources to emit light with weak light intensity based on a comparison output of the means; and a superimposed voltage supply for supplying a superimposed voltage for increasing the light intensity of each light source to the plurality of light source driving means The optical scanning device according to claim 2, further comprising: means for controlling the operation timing of the light source driving means.   The monitoring means includes a detection circuit that outputs a voltage detected by the light receiving means as a monitor voltage, and a comparison means that compares the monitor voltage with a weak light reference voltage and outputs a comparison voltage. Item 4. The optical scanning device according to Item 3.   The light source driving means is based on a holding circuit that holds the comparison voltage, a superposition circuit that superimposes the superposed voltage supplied from the superposed voltage supply means on the held comparison voltage, and a voltage output from the superposition circuit. The optical scanning device according to claim 4, further comprising a drive circuit that causes the light source to emit light.   The control means includes an image signal for operating the driving circuit at the timing of the APC and a scanning timing of the drawing area, a holding signal for operating the holding circuit at the timing of the APC, and the superposition at the scanning timing of the drawing area. 6. The optical scanning device according to claim 3, wherein a superimposing signal for superimposing in a circuit is output.   7. The optical scanning device according to claim 5, wherein the superimposed voltage supply means is provided in common to each of the plurality of light source driving means. 7. The optical scanning device according to claim 5, wherein a plurality of the superimposed voltage supply means are provided independently corresponding to the plurality of light source driving means.

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