JP2008039914A - Exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deviation in image formation by detecting horizontal synchronous signals of a plurality of light sources with an original beam pitch corresponding to the plurality of light sources in an exposure device using an overfield optical system. <P>SOLUTION: The exposure device is equipped with: a semiconductor laser having a plurality of light sources; a means for expanding the optical beam emitted from the light sources over a range wider than the width in the scanning direction of one reflection face of a rotary polygon mirror; a means for forming and controlling horizontal synchronous signals which means forms a horizontal synchronous signal for all beams from the plurality of light sources; a means for storing a compensating current profile in which scanning light made incident on a photoreceptor becomes nearly constant over the scanning direction; and a means for supplying a current to the light sources on the basis of the compensating current profile. In this exposure device, a means for adjusting light intensity at horizontal synchronization is provided which adjusts a quantity of a light beam when it is made incident on the horizontal synchronous signal detecting means, thereby adjusting to the same light quantity each light beam quantity made incident on the horizontal synchronous signal detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exposure apparatus, and more particularly to an exposure apparatus that exposes a photosensitive member by deflecting a light beam emitted from a light source and main-scanning the photosensitive member.

  2. Description of the Related Art Conventionally, in an exposure apparatus used for a copying machine, a facsimile machine, a laser printer, etc., a laser beam is mainly scanned on a photosensitive member by a light deflecting means such as a polygon mirror, and the photosensitive member is rotated in the sub scanning direction. Scan. Thereby, an electrostatic latent image is formed on the photoreceptor.

  Recently, since the printing speed of these apparatuses is increasing, the polygon mirror rotation speed in the underfilled optical system is becoming a limit. Therefore, overfilled optical systems have been used. In the overfilled optical system, the length of each reflection surface of the polygon mirror in the scanning direction is made shorter than the diameter of the laser beam incident in the polygon mirror in the scanning direction, and the laser beam is simultaneously incident on the plurality of reflection surfaces. Compared with the underfilled optical system, the overfilled optical system can greatly reduce the length in the scanning direction of the reflecting surface necessary to generate a spot light of a predetermined size on the photoconductor, and has the same diameter. This polygon mirror can be provided with more reflecting surfaces than the underfilled optical system. Therefore, there is an advantage that the polygon mirror can be rotated at a relatively low speed than the underfilled optical system and a polygon mirror driving device with low power consumption can be used.

  However, since the overfilled optical system reflects a part of the light beam of the incident laser beam as described above, the amount of light incident on the reflecting surface of the polygon mirror varies depending on the angle of the polygon mirror. FIG. 10 is a diagram showing this state, and the distribution of the amount of light incident on the photoconductor is highest at the center of the photoconductor and gradually decreases toward the end. This difference in the light amount distribution has a bad influence on the image quality.

In order to solve this problem, as described in Japanese Patent Laid-Open No. 09-197316, the amount of light fluctuation on each scanning plane is measured in advance, stored, and corrected so that the amount of light on one scanning plane is substantially reduced. Control that is constant is necessary.
JP 09-197316 A JP 2001-324688 A

  However, in order to further increase the printing speed, reduce noise, and reduce power consumption, there is an increasing need for an exposure apparatus that uses a plurality of laser beams while using an overfilled optical system.

  When a plurality of beams are used in an overfilled optical system, the difference in the amount of light between the beams increases with increasing distance from the polygon mirror due to the difference in the incident angle with respect to the polygon mirror. In particular, since the sensor (BD sensor) for detecting the horizontal synchronizing signal is disposed at a position corresponding to the end of the photosensitive member in the optical path, the light amount difference when performing BD signal detection for each beam also increases.

  The light amount difference at the time of detecting the BD signal becomes a factor causing a difference between each beam interval on the photosensitive drum and a beam interval detected by the BD sensor, as described in JP-A-2001-324688. There is a problem of causing a shift on the image.

The present invention has been made in view of the above points.
An object of the first invention related to the present application is to detect a horizontal synchronizing signal at an original beam interval even when a plurality of beams are used in an overfilled optical system.

  The object of the second invention related to the present application is to make the light amount at the time of APC emission of each laser in the horizontal synchronization signal detection unit the same, and perform light amount correction so that the light amount distribution becomes substantially constant in one scanning direction. There is.

  An object of the third invention according to the present application is to perform light amount correction also in the horizontal synchronization signal detection unit so that the amount of light when each laser is incident on the horizontal synchronization signal detection unit is the same.

In order to achieve the above object, the invention according to claim 1 is provided with a semiconductor laser having a plurality of light sources that emit light beams having a light amount corresponding to the amount of supplied current, and a plurality of reflecting surfaces that are emitted from the light sources. And a rotating polygon mirror that is rotated so that the light beam reflected by the reflecting surface forms a scanning line on the photosensitive member, and the rotation over a range wider than the width of one reflecting surface of the rotating polygon mirror in the scanning direction. A beam expanding means for expanding the light beam emitted from the light source so that the light beam is irradiated onto the polygon mirror, and a horizontal line provided at the start end on the scanning line for detecting the light beam and outputting a horizontal synchronizing signal. Synchronization signal detection means, horizontal synchronization signal generation control means for driving the semiconductor laser to generate horizontal synchronization signals for all the beams from the plurality of light sources, and scanning light incident on the photosensitive member A correction current profile storage means for storing the correction current profile is substantially constant over the scan direction,
In an exposure apparatus comprising: a current supply unit that supplies a current to the light source based on a correction current profile stored in the correction current profile storage unit;
A light intensity adjusting means for adjusting the light intensity of the light beam when entering the horizontal synchronizing signal detecting means; and a light intensity adjusting means for adjusting the light intensity when the light is incident on the horizontal synchronizing signal detecting means. The light quantity of the beam is adjusted to the same light quantity.

  According to a second aspect of the present invention, in the exposure apparatus according to the first aspect, the previous horizontal synchronization signal generation control means is a control means for driving the semiconductor laser by APC emission when the horizontal synchronization signal is detected. The horizontal synchronization light intensity adjusting means includes means for adjusting the light intensity during APC emission, and the light intensity of each light beam when entering the horizontal synchronization signal detecting means is adjusted to be the same light quantity. It is characterized by.

  According to a third aspect of the present invention, in the exposure apparatus according to the first aspect, the light intensity adjusting means at the time of horizontal synchronization includes a light amount when the first light beam is incident on the horizontal synchronization signal detecting means. Means for adjusting the amount of light when the other light beam is incident on the horizontal synchronization signal detecting means so that the amount of light when the other light beam is incident on the horizontal synchronization signal detecting means is the same. And the light amount adjustment amount is stored in the correction current profile storage means as a correction current value to the light source, and the horizontal synchronization light intensity adjustment means is used when the other light beam is incident on the horizontal synchronization signal detection means. And operating the current supply means.

As explained above,
According to the first aspect of the present invention, a semiconductor laser having a plurality of light sources emitting a light beam having a light amount corresponding to the amount of supplied current, and a plurality of reflecting surfaces are emitted from the light source and reflected by the reflecting surfaces. A rotating polygon mirror that is rotated so that the formed light beam forms a scanning line on the photosensitive member, and the light beam is applied to the rotating polygon mirror over a range wider than the width of one reflecting surface of the rotating polygon mirror in the scanning direction. A beam expanding means for expanding the light beam emitted from the light source so as to be irradiated, a horizontal synchronizing signal detecting means provided at the start end on the scanning line, for detecting the light beam and outputting a horizontal synchronizing signal; Horizontal synchronization signal generation control means for driving the semiconductor laser so as to generate horizontal synchronization signals for all the beams from the plurality of light sources, and scanning light incident on the photosensitive member in the scanning direction. An exposure device comprising: a correction current profile storage unit that stores a constant correction current profile; and a current supply unit that supplies a current to the light source based on the correction current profile stored in the correction current profile storage unit. The apparatus further includes a horizontal synchronization light intensity adjustment unit that adjusts a light intensity of the light beam when incident on the horizontal synchronization signal detection unit, and is incident on the horizontal synchronization signal detection unit by the horizontal synchronization light intensity adjustment unit. Since the light quantity of each light beam is adjusted to the same light quantity, even in the overfilled optical system, the horizontal synchronization signal can be detected at the original beam interval when a plurality of beams are used. As a result, the image writing position in the main scanning direction is constant regardless of the beam, and good image formation can be performed.

  According to a second aspect of the present invention, in the exposure apparatus according to the first aspect, the first horizontal synchronizing signal generation control means controls the semiconductor laser when the horizontal synchronizing signal is detected by APC emission. The horizontal synchronization light intensity adjusting means includes means for adjusting the light intensity during APC emission, and the light intensity of each light beam when entering the horizontal synchronization signal detecting means is adjusted to be the same light quantity. Therefore, the same amount of light can be stably incident on the horizontal synchronization signal detecting means.

  According to a third aspect of the present invention, in the exposure apparatus according to the first aspect, the horizontal synchronization light intensity adjustment means includes a light amount when the first light beam is incident on the horizontal synchronization signal detection means. And means for adjusting the amount of light when the other light beam is incident on the horizontal synchronization signal detecting means so that the amount of light when the other light beam is incident on the horizontal synchronization signal detecting means is the same. The light amount adjustment amount is stored in the correction current profile storage means as a correction current value to the light source, and the light intensity adjustment means at the time of horizontal synchronization has the other light beam incident on the horizontal synchronization signal detection means. Since the current supply means is sometimes operated, it is possible to apply a light amount correction function that is essential for an overfilled optical system, and to detect a horizontal synchronization signal without increasing the cost of the apparatus. The amount of incident light of each laser light can be the same for stages.

(Example 1)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a view for explaining an exposure apparatus according to this embodiment of the present invention.

  In the figure, 1 is a laser light source, 2 is a collimator lens, 3 is an aperture, 4 is a main scanning expander lens, 5 is a cylindrical lens, 7 is a folding mirror, 8 is a polygon mirror, 9 is an fθ lens, and 10 is mainly used. An anamorphic aspherical lens 11 having power in the sub-scanning direction, 11 is a drum front folding mirror. Reference numeral 12 denotes a BD reflection mirror for guiding a beam to a horizontal synchronization detecting element (BD sensor) 13 provided for determining the image writing timing.

  The laser light emitted from the laser light source 1 is made into near-parallel light by the collimator lens 2, the light beam is restricted by the diaphragm 3, the light beam becomes divergent light in the main scanning direction by the main scanning expander lens, and sub-scanning is performed by the cylindrical lens 5. The light is collected only in the direction, reflected and folded by the folding mirror 7, passed through the fθ lens 9, and collected on the line near the reflecting surface of the polygon mirror 8. The polygon mirror 8 rotates at a constant speed and deflects the laser beam.

  Further, the deflected laser light is incident again on the fθ lens 9 having the fθ characteristic, and the light beam is condensed in the main scanning direction. The light beam emitted from the fθ lens is condensed in the sub-scanning direction by the anamorphic aspherical lens 10 having power in the sub-scanning direction, and forms a spot on a photosensitive drum (not shown) via the drum front folding mirror 11.

  FIG. 2 shows a control block of the exposure apparatus.

  The semiconductor laser 1 includes laser light sources 21a (LD) and 21b, and a photodiode (PD) 22 that receives a laser beam emitted from the LD 21 and outputs a current corresponding to the amount of the received laser beam. Has been. The anode of the LD 21 is connected to the power source, and the cathode is connected to the LDOA terminal and LDOB terminal of the laser driver IC 27 which is a laser control means. One end of the PD 22 is connected to the power source, and the other end is connected to the PD terminal of the laser driver IC 27. The resistors R1a and R1b are provided between the power supply and the R0A terminal and the R0B terminal of the laser driver IC 27. The resistors R3a and R3b are provided between GND and the RMA and RMB terminals of the laser driver IC 27. Capacitors C1a and C1b are provided between GND and the VCHA and VCHB terminals of the laser driver IC 27. The resistors R2a and R2b are provided between GND and the RSA and RSB terminals of the laser driver IC 27. The exposure apparatus control unit 28 transmits control signals and video signals to the laser driver IC 27 to control APC and laser switching. The output of the light amount correction unit 29 is input to the constant current conversion circuits 30a and 30b, and after being converted to a constant current, is connected to the RSA and RSB terminals of the laser driver IC 27, and the light amount on one scanning on a photosensitive drum (not shown). The current is supplied so that becomes substantially constant.

  Next, the operation of the exposure apparatus in one scan will be described with reference to FIG.

  In period (1), the exposure apparatus control unit 28 instructs the laser driver IC 27 to perform APC-B (Auto Power Control), and the laser driver IC 27 performs APC emission of the LD 21b. By emitting light from the LD 21b, a current flows through the PD 22 in accordance with the amount of light emitted, and this current flows from the RMB terminal to R3b. In APC-B light emission, the current of the LD 21b is adjusted so that the voltage of the RMB terminal becomes a desired value. The current of the LD 21b is converted from current to voltage and output to the VCHB terminal. When this state has passed for a certain period of time, APC-B is terminated and transition is made to period (2).

  In the period (2), the exposure apparatus control unit 28 instructs the laser driver IC 27 to perform APC-A (Auto Power Control), and performs the same processing as in the previous period (1) for the other light source LD 21a. . If the output from the BD sensor (BD-A, falling) is obtained during APC-A emission, APC-A emission ends immediately (or after a predetermined time), and transitions to the APC-B state again.

  In period (3), when the output from the BD sensor (BD-B, falling) is obtained, APC-B emission is terminated immediately (or after a predetermined time), and the state transits to the mask state.

  In period (4), the exposure apparatus controller 28 issues a mask control instruction to the laser driver IC 27. As a result, the LD 21a and LD 21b do not emit light, and constant currents determined based on the voltages of the VCHA terminal and the VCHB terminal are supplied to R1a, R1b and R2a, R2b. The purpose of flowing this current is to speed up the rise of LD21a and LD21b. The time of the period (4) is determined by the time from when the BD sensor signal is input until the image is written, and is a variable value depending on the paper size or the like, with / without border.

  In period (5), the exposure apparatus control unit 28 instructs the laser driver IC 27 to input video. Thereby, laser light emission based on image data (video signal) is performed. When the video input is true, switching is performed so that a current flows through the LD21, and when the video input is false, a current flows through R1.

  In period (6), the mask state is entered again. This timing is also a variable value depending on the paper size and the presence / absence of a border as in the previous period (4).

  By repeating the above, APC and BD detection for each light source is performed for each scan, and an electrostatic latent image is formed on the photosensitive drum.

  Next, light quantity correction will be described.

  FIG. 5 is a diagram illustrating a block configuration of the light amount correction unit 29.

  The light quantity correction unit 29 includes a logic unit 51, an internal memory 52 including a nonvolatile memory and various setting registers, and a D / A conversion unit 53. The logic unit 51 receives a trigger (TR) signal, an operation clock (SCLK) signal, a data out (DO) signal, a data communication clock (SCK) signal, and a select (CS) signal from the exposure control device 28, and receives data in. (DI) signal is output. In addition, reading / writing of the internal memory 52 and an operation instruction to the D / A conversion unit 53 are simultaneously performed.

  Correction data is stored as a digital value in a nonvolatile memory in the internal memory. This correction data is address-mapped, and in the present embodiment, there are two light sources, so the correction data for each of the light sources A and B is address-mapped. These correction data are sequentially transmitted to the D / A conversion unit 53 by the clock from the logic unit 51, and a voltage obtained by converting the digital value into an analog signal is input to the constant current circuit, converted into a constant current, and RSA and RSB terminals. To be supplied.

  FIG. 4 is an example showing the relationship between the amount of current supplied to the resistor RS and the correction light quantity of the LD 21, with the horizontal axis representing the RS supply current and the vertical axis representing the correction light quantity. The corrected laser emission amount is proportional to the amount of current supplied to the resistor RS.

  Next, the light amount adjustment of the exposure apparatus will be described.

  Light from the light sources 21a and 21b is transmitted through each lens and is incident on the photosensitive drum via the front folding mirror. In order to keep the amount of light incident on the photosensitive member constant from the variation in the transmittance of each lens, the variation in the reflectance of each folding mirror, and the variation in the radiation pattern (FFP: far field) of the semiconductor laser, It is necessary to adjust the light amount for the exposure apparatus. The function of adjusting the amount of light is the resistance of R3a and R3b.

  These resistors are variable resistors, and if the resistance value is lowered, more current flows through the laser, so that the amount of light emission during APC increases, and if the resistance value is increased, the amount of light emission during APC decreases. The position where the light amount adjustment is performed is performed at the position of the BD sensor.

  For example, a light quantity detection element such as a photodiode is placed at the position of the BD sensor 13 in FIG. 1, APC-A light emission is performed, and the detection value of the light quantity detection element is a predetermined value, P (for example, on the photosensitive drum) R3a is adjusted so as to be a value that takes into account the variation in the reflectance of the front folding mirror 11 with respect to the amount of light. Next, APC-B light emission is performed, and similarly, R3b is adjusted so that the detection value of the light amount detection element becomes a predetermined value, P.

  Alternatively, the BD sensor itself may have a function of outputting an analog voltage output corresponding to the amount of incident light, and the variable resistor may be adjusted while monitoring this voltage to adjust the amount of light during APC.

  The adjustment may be performed by connecting an oscilloscope or the like to the light quantity detection element while the polygon mirror 8 is rotating, or by fixing the angle of the polygon mirror 8 so that the light beam hits the light quantity detection element. May be.

  FIG. 6 is a diagram showing the light distribution on the photosensitive member when the APC light amount is adjusted at the position of the BD sensor and when APC light emission is performed at the image center portion. (A) is a case where the APC light amounts of LDA and LDB are adjusted at the center of the image, and the difference between the light amounts of the beams increases toward the end. On the other hand, (b) shows the case where the APC light quantity is adjusted by the BD sensor unit, and the light quantity difference at the center of the image is the largest.

  By obtaining light amount correction data in this state (a state where the APC light amount is adjusted by the BD sensor unit), the exposure light amount on the photosensitive member is controlled to be constant.

  FIG. 7 is a data table of a light amount distribution corresponding to the APC light amount of the LDA in FIG. The amount of light on the photosensitive member when the LDA is APC emitted at each position is shown as a pre-correction light amount by dividing the photosensitive member into 32 parts in the main scanning direction. Since the light amount of the beam irradiated on the photoconductor during image formation is 215 uW, the correction light amount at each position is calculated as (pre-correction light amount) −215. FIG. 7B shows the relationship between the pre-correction light amount, the correction light amount, and the target light amount on the photosensitive member. Since the light amount correction is correction in a direction in which the light amount from the light source is reduced by supplying a current to the RSA terminal (resistor R2a), the corrected light amount is converted into a current. The corrected current amount indicates the converted current value. This correction current amount is supplied from the constant current circuit 30a. The amount of correction current supplied from the constant current circuit 30 a is determined by the voltage output from the light amount correction unit 29 to the constant current circuit 30. The portion indicated by the correction voltage target is the output voltage from the light amount correction unit corresponding to each correction current amount. The voltage output from the light intensity correction unit is the value obtained by multiplying the data stored in the memory by the output unit voltage, for example, 5 mV × 10 = 50 mV when the output unit is 5 mV and the data is 0 AH. Therefore, the value obtained by dividing the correction voltage target by the output unit voltage is the data value stored in the memory. The same is done for LDB.

  In this way, APC light amount adjustment is performed for each exposure apparatus, and light amount correction data is sequentially stored in the memory of the light amount correction unit. FIG. 8 shows the stored correction data. A correction data memory for LDA is provided from addresses “0000h” to “007Fh”. In this embodiment, 32 rows from “001Fh” are used. A correction data memory for LDB is provided from addresses “0080h” to “00FFh”. In this embodiment, 32 rows from “009Fh” are used.

  FIG. 9 is a flowchart of control performed by the exposure apparatus control unit 28.

  When a print instruction is issued in step S601, the light amount correction start address of the LDA is written as “00H” to the light amount correction unit in step S602, and further, the number of LDA correction data is written as “32” in step S603.

  Next, the LDB light quantity correction start address and the number of correction data are written in the same manner.

  In the next step S606, a clock for sequentially transferring the correction data to the D / A converter is designated.

  In the present embodiment, since the number of data is 32 at 100 KHz, the light amount correction is performed for 1 / 100k * 32 = 320 usec. The clock frequency and the number of correction data are usually optimized in accordance with the light amount correction resolution and the rotation speed of the polygon mirror.

  In the next step S607, the process waits until the scanner is ready. The scanner ready indicates a state in which the rotation speed of the polygon mirror reaches the printable rotation speed and the rotation is stable. If it is determined that the scanner is ready, the light amount correction unit is instructed to start light amount correction in step S608. Receiving this, the light amount correction unit performs light amount correction in synchronization with each scan. Next, it is determined in step S609 whether or not printing is completed. When it is determined that printing is completed, a light amount correction stop instruction is sent to the light amount correction unit in step S610, and this control is terminated.

  As described above, in the overfilled optical system, the BD sensor unit is adjusted so that the light amounts at the time of APC of the lasers are the same, and the light amount correction data is obtained in that state to perform light amount correction. When a plurality of beams are used, the BD signal can be detected with the original beam interval.

(Example 2)
In the above-described embodiment, the amount of light at the time of APC is adjusted by the BD sensor unit so that each beam has the same amount of light. However, in this embodiment, the amount of light of the BD sensor unit is adjusted using light amount correction. The same BD signal is detected.

  This will be described below with reference to the drawings.

  FIG. 11 shows the light amount distribution in one scanning range of each laser at a position corresponding to the photosensitive member in this embodiment. The mutual lasers are APC-adjusted at the center of the image, and the APC light quantity is adjusted to be the same at this position. The light amount distribution is measured by dividing it into 60 parts, and is 24 points left and right (48 points in the image area) from the center of the image, and 12 points in others. The BD sensor is arranged at a position where the reflection surface of the polygon is switched.

  The light amount of the BD sensor portion of the LDA is less than the target light amount on the photoconductor. On the other hand, the LDB exceeds the target light amount on the photoconductor. Since the light amount correction functions in the direction of reducing the light amount, in order to make the light amount of the BD sensor unit the same, it is necessary to correct the light amount when the LDB BD sensor is incident and to match the light amount when the LDA BD sensor is incident There is.

  FIG. 12 is a timing chart showing how much correction clock time each period in one scan corresponds to. 2CLK is required for the periods (1) and (2), 1CLK is required for the period (3), 5CLK is required for the period (4), 48CLK is required for the period (5), and 2CLK is required for the period (6). Since the beam from the LDB is incident on the BD sensor in the period (3), the light quantity in this period must be matched with the light quantity of the LDA.

  FIG. 13 shows data when the light quantity correction is performed so that the light quantity of the LDB when the BD sensor is incident is the same as that of the LDA. When the light amount correction is started from the beginning of the period (2) in FIG. 12, the LDB light is incident on the BD sensor after 3 CLK of the correction clock. Is data that matches the amount of light that is incident on the BD sensor. Since the period from the 5th CLK to the 8th CLK is a mask period, no light amount correction is performed (it is not corrected by setting the data to zero). After the 9th CLK, the amount of light is corrected by 48 CLK, and the amount of light on the photoconductor becomes constant.

  As described above, it is also possible to correct the light amount of other laser beams so that the light amount of a specific laser beam when the BD sensor is incident is the same as the light amount of the other laser beam. The amount of light can be the same.

1 is a diagram showing a configuration of an exposure apparatus according to the present invention. 1 is a block diagram showing a block configuration of an exposure apparatus according to the present invention. The timing chart explaining 1st embodiment concerning the present invention. The figure explaining light quantity correction | amendment of the exposure apparatus concerning this invention. The figure explaining the control block of the exposure apparatus concerning this invention. The figure explaining light quantity adjustment of the exposure apparatus of 1st embodiment concerning this invention. The light quantity correction data of the exposure apparatus of 1st Embodiment concerning this invention. The light quantity correction data of the exposure apparatus of 1st Embodiment concerning this invention. The flowchart explaining 1st embodiment concerning this invention. The figure explaining the light quantity distribution of an overfilled optical system. The figure explaining the Vref voltage setting of 2nd embodiment concerning this invention. The figure explaining light quantity correction | amendment of the exposure apparatus of 2nd embodiment concerning this invention. The light quantity correction data of the exposure apparatus of 1st Embodiment concerning this invention.

Explanation of symbols

1 Light source (semiconductor laser)
8 Polygon mirror
27 Laser driver
28 Exposure unit controller
29 Light intensity correction
30 Constant current circuit
52 Internal memory
53 D / A converter

Claims (3)

A semiconductor laser having a plurality of light sources that emit a light beam having a light amount corresponding to the amount of supplied current;
A rotating polygon mirror that includes a plurality of reflecting surfaces and is rotated so that a light beam emitted from the light source and reflected by the reflecting surfaces forms a scanning line on the photosensitive member;
Beam expanding means for expanding the light beam emitted from the light source so that the light beam is irradiated onto the rotating polygon mirror over a range wider than the width in the scanning direction of one reflecting surface of the rotating polygon mirror;
A horizontal synchronizing signal detecting means provided at a starting end on the scanning line, for detecting the light beam and outputting a horizontal synchronizing signal;
Horizontal synchronization signal generation control means for driving the semiconductor laser to generate horizontal synchronization signals for all the beams from the plurality of light sources;
Correction current profile storage means for storing a correction current profile in which the scanning light incident on the photosensitive member becomes substantially constant in the scanning direction;
Current supply means for supplying current to the light source based on the correction current profile stored in the correction current profile storage means;
In an exposure apparatus comprising:
A light intensity adjusting means for adjusting the light intensity of the light beam when entering the horizontal synchronizing signal detecting means; and a light intensity adjusting means for adjusting the light intensity when the light is incident on the horizontal synchronizing signal detecting means. An exposure apparatus characterized in that the light quantity of the beam is adjusted to the same light quantity. The horizontal synchronization signal generation control means is a control means for driving the semiconductor laser at the time of detecting the horizontal synchronization signal by APC emission,
The horizontal synchronization light intensity adjustment means includes means for adjusting the light intensity during APC emission, and the light intensity of each light beam when entering the horizontal synchronization signal detection means is adjusted to be the same.
2. An exposure apparatus according to claim 1, wherein: The horizontal synchronization light intensity adjusting means has a light quantity when the first light beam is incident on the horizontal synchronization signal detection means and a light quantity when the other light beams are incident on the horizontal synchronization signal detection means. Means for adjusting the amount of light when the other light beams are incident on the horizontal synchronization signal detecting means so as to be the same,
The light amount adjustment amount is stored in the correction current profile storage unit as a correction current value to the light source,
2. The exposure apparatus according to claim 1, wherein the horizontal synchronization light intensity adjustment means operates the current supply means when another light beam is incident on the horizontal synchronization signal detection means.

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