JPH1052939A - Light amount control device and image forming apparatus - Google Patents

Abstract

(57) [Problem] To provide the same adjustment of the light amount of each light beam emitted from each light emitting unit at a position to be exposed. SOLUTION: When adjusting the light amount of light emitting units 2 and 3, a conversion unit C is used.
Each output voltage converted by OV and each setting unit SET1,
It is characterized in that the CPU 10 independently adjusts the drive current applied to each of the light emitting units 2 and 3 so that each target light amount set by SET2 matches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount control device for adjusting the light amounts of a plurality of light emitting units having different light amount characteristics and an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a laser element has been used as an exposure means of an image recording apparatus such as a printer. In this case, the light emitting portion of the exposure means is one, and the laser light amount control in this case controls the laser current so that the output value of the light amount detecting element paired with the light emitting portion becomes a certain value. (A
PC).

[0003]

However, when a plurality of light emitting laser elements are used as exposure means and a light quantity detecting means (for example, a pin photodetector) is common, control of the laser light quantity is performed as in the above-mentioned conventional example. When the output of the light amount detection element is set to a constant value for any of the light emitting units, the aperture of the laser unit with respect to the light amount on the laser element due to the difference in the far field pattern of each light emitting unit. Since the light quantity after that, that is, the light quantity ratio on the photosensitive drum surface (hereinafter, referred to as collimator efficiency) is different, the conventional method in which the light quantity on the laser element is controlled to a constant value for each light emitting unit, The light emitting unit causes a difference in the amount of light on the drum surface.

Further, the internal resistance of the light quantity detecting element varies from light receiving portion to light receiving portion, and even if the same light amount is received due to the difference in the light receiving position of the beam from each light emitting portion, the output of the light quantity detecting element varies. I was

[0005] Further, when the light passes through the lens or is reflected by the mirror, the light quantity varies for each beam due to the variation of the polarization of each light emitting portion.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the first to eighth inventions according to the present invention to provide a light-emitting device in which each light-emitting portion has a light-intensity characteristic in accordance with a light-intensity characteristic. By individually setting a control target value and adjusting the collimator efficiency of each light emitting unit, and the amount of light on the drum surface caused by the difference in polarization and sensitivity unevenness of the detecting element, light is emitted from each light emitting unit. An object of the present invention is to provide a light amount control device and an image forming apparatus that can adjust the respective light amounts of respective light beams at exposure positions and can form an image without image unevenness.

[0007]

According to a first aspect of the present invention, there is provided an exposure means having a plurality of light emitting portions for emitting light beams, and a light amount for detecting the light amount of each light beam emitted from each light emitting portion. Detecting means, converting means for converting an output current corresponding to the light quantity of each light beam detected by the light quantity detecting means into an output voltage when adjusting the light quantity of the exposing means, and independently setting a different target light quantity for each light emitting unit. A plurality of setting means for adjusting the driving current to be applied to each light emitting unit independently so that each output voltage converted by the conversion means and each target light quantity set by each setting means coincide with each other. And a first adjusting means.

According to a second aspect of the present invention, there is provided an exposure unit having a plurality of light emitting units for emitting a light beam, a light amount detecting unit for detecting a light amount of each light beam emitted from each light emitting unit, At the time of light amount adjustment of the means, a converting means for converting an output current corresponding to the light amount of each light beam detected by the light amount detecting means into an output voltage, and a setting means for setting a different target light amount to any of the light emitting units, Second adjusting means for independently adjusting the drive current applied to each light emitting unit such that each output voltage converted by the converting means matches the target light quantity set by the setting means or the stored reference light quantity. And

According to a third aspect of the present invention, the conversion means changes and sets the current / voltage conversion rate when adjusting the light amount of one of the light emitting units.

According to a fourth aspect of the present invention, the conversion means changes and sets the current / voltage amplification factor when adjusting the light amount of one of the light emitting units.

According to a fifth aspect of the present invention, there is provided an exposure unit having a plurality of light emitting units for emitting light beams, a light amount detecting unit for detecting the amount of each light beam emitted from each light emitting unit, A plurality of conversion means for converting an output current corresponding to the light quantity of each light beam detected by the light quantity detection means into an output voltage when adjusting the light quantity of the means; And a third adjusting unit that independently adjusts a drive current applied to each light emitting unit so that the light amount of each light beam becomes each reference value based on the reference value.

According to a sixth aspect of the present invention, one of the conversion means changes and sets the current / voltage amplification factor.

According to a seventh aspect of the present invention, each conversion means changes and sets a current / voltage conversion rate.

An eighth invention according to the present invention is characterized in that the first, second,
The present invention relates to an image forming apparatus provided with any one of the light amount control devices according to the fifth invention.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram illustrating the configuration of a light quantity control device according to a first embodiment of the present invention. The light quantity control device includes a laser unit LU and a control unit CU.
It is composed of

In FIG. 1, reference numeral 1 denotes a multi-beam semiconductor laser, in which two light emitting units 2 and 3 are provided.
A pin photodetector 4 serving as a light amount detecting means for detecting the amount of light is built in. The pin photo detector 4
Outputs a current (output current Ipd) corresponding to the light amount of the light emitting unit.

Output current I from pin photodetector 4
The pd is subjected to current / voltage conversion by the resistor 5, and the light amount is detected by the CPU 10 as a laser light amount adjusting means via a voltage follower circuit (conversion unit COV) including an operational amplifier 6, input resistors 7, 8 and an output protection resistor 9. It is transmitted as signal PDIN.

Inside the CPU 10, a light amount detection signal PD is provided.
It has an analog / digital conversion input port (hereinafter referred to as A / D port) 11 for taking in IN. The A / D port 11 also has a target voltage of a light amount detection signal PDIN at the time of laser light amount adjustment. It is input to each of the light emitting units 2 and 3 (target voltage Vpd1, target voltage Vpd2).
The target voltages Vpd1 and Vpd2 are generated by resistance voltage division by the resistors 12 and 13 and the variable resistors 14 and 15 in the laser unit LU, respectively, and the amount of light on the photosensitive drum surface after the aperture (squeezing) of each laser beam is obtained. The values of the target voltages Vpd1 and Vpd2 can be adjusted by the variable resistors 14 and 15 so as to be controlled to desired values. The setting units SET1 and SET2 are constituted by the resistor 12, the variable resistor 14, or the resistor 13 and the variable resistor 15.

Reference numeral 16 denotes a digital / analog conversion output port (hereinafter, referred to as a D / A port). Two sets of 8-bit outputs are input to the addition circuits 17 and 18, respectively. In the adders 17 and 18, the two inputs are weighted differently to make coarse adjustment and fine adjustment, and the addition result is input to constant current power supplies 19 and 20 of the semiconductor laser. A current value corresponding to the input voltage from the circuits 17 and 18 is supplied to the light emitting units 2 and 3 via the differential switching circuits 21 and 22.

Thus, the CPU 10 controls the laser current by changing each output of the D / A port 16 so that the light quantity detection signal PDIN becomes equal to the target voltages Vpd1 and Vpd2.

Reference numeral 23 denotes an input / output port (hereinafter referred to as an I / O port) for outputting the forced light emission signals UBL1 and UBL2.
The signals are input to AND circuits 24 and 25 together with DO1 and VDO2. When any one of the forced light emission signals UBL1 and UBL2 or the image signals VDO1 and VDO2 becomes a LOW level, the LOW output is output from the differential switching circuits 21 and 22.
And supplies current from the constant current power supplies 19 and 20 to the semiconductor laser side to cause the semiconductor laser to emit light. At the time of adjusting the laser light amount, the forcible light emission signals UBL1 and UBL2 are set to LOW to cause the semiconductor laser to emit light. In addition, an arithmetic unit (hereinafter referred to as ALU) 26 inside the CPU 10,
A ROM 27, a RAM 28, a timer 29 and the like as storage means are provided.

FIG. 2 is a diagram for explaining the light amount control characteristics of each of the light emitting units 2 and 3 shown in FIG. 1. The first and second quadrants indicate the pin photodetector output current Ipd. The horizontal axis of the four quadrants indicates the light amount detection signal PDIN,
The abscissa of the quadrant indicates the amount of light output from the laser element, and the ordinates of the third and fourth quadrants indicate the amount of light on the photosensitive drum (not shown).

As shown in this figure, in order to make the light amount of each of the light emitting units 2 and 3 on the photosensitive drum surface a desired value (Ld),
The output light amounts L1 and L2 on the laser device are different from the collimator efficiencies of the light emitting units 2 and 3, and the output currents of the pin photo detectors 4 are also different. The output current target value is provided independently. Therefore, the target voltages Vpd1, Vp of the light quantity detection signal PDIN after the current / voltage conversion are performed.
d2 also becomes an independent value for each of the light emitting units 2 and 3.

As described above, when the light amount adjustment of the semiconductor laser device having the plurality of light emitting units 2 and 3 is performed by one light amount detecting element, the target value for the detection output is made independent for each light emitting unit 2 and 3. By making the adjustment possible, it is possible to control the light amount of the photosensitive drum surface of each of the light emitting units 2 and 3 having different collimator efficiencies to be constant (Ld).

Hereinafter, the correspondence between this embodiment and each means of the first invention and the operation thereof will be described with reference to FIG.

According to a first aspect of the present invention, there is provided an exposure unit having a plurality of light emitting units 2 and 3 for emitting a light beam, and a light amount detecting unit (pin photodetector 4) for detecting the amount of each light beam emitted from each light emitting unit. When adjusting the light amount of the exposure means,
A converter (converter COV) for converting an output current corresponding to the light amount of each light beam detected by the light amount detector into an output voltage; and a plurality of setting units for independently setting different target light amounts for the respective light emitting units. (Setting part SET1, SET2)
And first adjusting means (CPU 10) for independently adjusting the drive current applied to each light emitting unit so that each output voltage converted by the converting means and each target light amount set by each setting means coincide with each other. Executes the control program stored in the ROM 27 to execute the addition circuits 17 and 18 and the constant current power supply 1.
9, 20 and adjustment via differential switching circuits 21 and 22), and when adjusting the light amount of the light emitting units 2 and 3, each output voltage converted by the conversion unit COV and each setting unit SET.
Since the CPU 10 independently adjusts the driving current applied to each of the light emitting units 2 and 3 so that the respective target light amounts set by the SET 1 and SET 2 coincide with each other, the target for controlling the light amount according to the variation in the light amount characteristics. While individually setting the values, the light amounts of the respective light beams emitted from the respective light emitting units in the vicinity of the exposure unit (for example, the exposure position of the photosensitive drum) can be matched.

[Second Embodiment] Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a circuit block diagram illustrating the configuration of a light quantity control device according to a second embodiment of the present invention.
The same components as those described above are denoted by the same reference numerals. The first
The difference from the embodiment is that a variable resistor 30 is added in series with a resistor 5 for converting the output current from the pin photodetector 4 into a voltage, so that the current / voltage conversion efficiency can be adjusted.

For this reason, one of the two light emitting units 2 and 3 (the light emitting unit 2 in the present embodiment) outputs a light amount detection signal PDIN when the light amount on the photosensitive drum surface is a desired value.
By adjusting the variable resistor 30 so as to be equal to the value Vpd1 set in the ROM 27 of the No. 10, there is no need to transmit the target voltage from the laser unit side, the Vpd1 signal in the first embodiment can be deleted, and the A / D The number of inputs to the port 11 can be reduced by one. The output relationship is the same as the characteristic shown in FIG. 2 in the first embodiment.

As described above, when the light amount adjustment of the semiconductor laser device having the plurality of light emitting units 2 and 3 is performed by one light amount detecting element, the target value for the detection output is independently set for each light emitting unit 2 and 3. By making the adjustment possible, it is possible to control the light amount of the photosensitive drum surface of each light emitting unit having different collimator efficiency to be constant.

Further, by making the current-voltage conversion efficiency from the detection output (current value) to voltage variable, it becomes possible to carry out the operation at lower cost.

Hereinafter, the correspondence between this embodiment and each means of the second and third inventions and the operation thereof will be described with reference to FIG.

According to a second aspect of the present invention, there is provided an exposure unit having a plurality of light emitting units 2 and 3 for emitting a light beam, and a light amount detecting unit (pin photodetector 4) for detecting the amount of each light beam emitted from each light emitting unit. When adjusting the light amount of the exposure means,
A conversion unit (conversion unit COV11) for converting an output current corresponding to the light amount of each light beam detected by the light amount detection unit into an output voltage, and a setting unit (setting unit) for setting a different target light amount for one of the light emitting units SET11) and a second step of independently adjusting the drive current applied to each light emitting unit so that each output voltage converted by the conversion unit matches the target light amount set by the setting unit or the stored reference light amount. (The CPU 10 executes a control program stored in the ROM 27 and adjusts it through the addition circuits 17 and 18, the constant current power supplies 19 and 20, and the differential switching circuits 21 and 22), and emits light. When adjusting the light amounts of the units 2 and 3, each output voltage converted by the conversion unit COV11 is equal to the target light amount set by the setting unit SET11 or the stored reference light amount. The CPU 10 independently adjusts the drive current applied to each of the light emitting units 2 and 3 so that the target value for light amount control can be individually set according to the variation in light amount characteristics with a simple circuit configuration. The light amounts of the respective light beams emitted from the respective light emitting units in the vicinity of the exposure unit can be matched.

According to a third aspect of the present invention, the conversion means (conversion unit CO
In V11), the current / voltage conversion rate is changed and set by the variable resistor 30 when adjusting the light amount of one of the light emitting units, so that the conversion unit COV11 easily sets a target value for any one of the light emitting units. be able to.

Third Embodiment Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is a circuit block diagram illustrating the configuration of a light quantity control device according to a third embodiment of the present invention.
The same components as those described above are denoted by the same reference numerals. The second
The difference from the embodiment is that the efficiency of the current / voltage conversion of the light amount detection current (Ipd) from the pin photodetector 4 to the light amount detection signal (PDIN) can be varied by providing an amplifier circuit after the resistor 5 and increasing the amplification factor. This is done by making it variable. In terms of circuit, the variable resistor 30 is eliminated from the circuit of the second embodiment, and the variable resistor 31
Is added to the voltage follower circuit to form an amplifier circuit having a variable amplification factor. The output relationship is the same as the characteristic shown in FIG. 2 in the first embodiment.

As described above, when the light amount of a semiconductor laser device having a plurality of light emitting portions 2 and 3 is adjusted by one light amount detecting element, the target value for the detection output is independently set for each light emitting portion 2 and 3. By making it adjustable, it becomes possible to control the light amount of the photosensitive drum surface of each of the light emitting units 2 and 3 having different collimator efficiencies to be constant.

Further, by making the current / voltage conversion efficiency from the detection output (current value) to voltage variable, it becomes possible to implement the method at lower cost.

Hereinafter, the correspondence between this embodiment and each means of the fourth invention and the operation thereof will be described with reference to FIG.

According to a fourth aspect of the present invention, the conversion means (conversion unit CO
V12) is to change and set the current / voltage conversion rate by changing and setting the current / voltage amplification rate by the variable resistor 31 when adjusting the light amount of one of the light emitting units.
The light amount of each light beam emitted from each of the light emitting units 2 and 3 near the exposure unit can be matched while easily setting the target value for any one of the light emitting units COV on the side.

[Fourth Embodiment] Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a circuit block diagram illustrating the configuration of a light quantity control device according to a fourth embodiment of the present invention. The light quantity control device includes a laser unit LU and a control unit CU.
It is composed of The same components as those in FIG. 1 are denoted by the same reference numerals. The difference from the second embodiment is that after the light quantity detection current (Ipd) from the pin photodetector 4 is current / voltage converted by the resistor 5 and the variable resistor 30,
Two amplifier circuits including operational amplifiers 6 and 33, input resistors 7 and 34, output protection resistors 9 and 36, and feedback resistors 8, 32, 35 and 37 are provided. The light amount detection signal (PDIN1) is used as the light amount detection signal, and the other light amount detection signal PDIN2 of the light emitting unit 3 is used as the light amount detection signal (PDIN1). And
The point is that the amplification factor of the amplification circuit on the light amount detection signal PDIN2 side is made variable.

Thus, the light amount detection signal PDIN1 is adjusted by adjusting the variable resistor 30 for current / voltage conversion.
The light amount detection signal PDIN2 is adjusted by adjusting the amplification factor of the amplifier circuit so that when the light amount of each of the light emitting units 2 and 3 on the photosensitive drum surface is a desired value, each light amount detection signal output is output to the CPU 10.
If the adjustment is made so as to be equal to the value (Vpd) set in the ROM 27, there is no need to transmit the target voltage from the laser unit side. It suffices to perform control so as to be equal to (Vpd), which simplifies control.

FIG. 6 is a diagram for explaining the light amount control characteristics of each of the light emitting sections 2 and 3 shown in FIG. 5. The vertical axes of the first and second quadrants indicate the pin photodetector output current Ipd. The horizontal axis of the four quadrants indicates the light amount detection signal PDIN,
The abscissa of the quadrant indicates the amount of light output from the laser element, and the ordinates of the third and fourth quadrants indicate the amount of light on the photosensitive drum (not shown).

As shown in this figure, the output current target value of the pin photodetector 4 at the time of adjusting the light amount of each of the light emitting units 2 and 3 is independently provided, but the light amount detection signal PDIN1 after the current / voltage conversion is performed. , PDIN2 have a single value due to the adjustment.

As described above, when the light amount of the semiconductor laser element having the plurality of light emitting units 2 and 3 is adjusted by one light amount detecting element, the target value for the detection output is independently set for each light emitting unit 2 and 3. By making the adjustment possible, it is possible to control the light amount of the photosensitive drum surface of each light emitting unit having different collimator efficiency to be constant.

Further, by making the current / voltage conversion efficiency from the detection output (current value) to voltage independently variable by each of the light emitting units 2 and 3, the operation can be performed at lower cost and the control becomes simpler.

Hereinafter, the correspondence between this embodiment and each means of the fifth and sixth inventions and the operation thereof will be described with reference to FIG.

According to a fifth aspect of the present invention, there is provided an exposure unit having a plurality of light emitting units 2 and 3 for emitting light beams, and a light amount detecting unit (pin photodetector 4) for detecting the amount of each light beam emitted from each light emitting unit. When adjusting the light amount of the exposure means,
A plurality of converters (converters COV21 and COV22) for converting an output current corresponding to the amount of light of each light beam detected by the light amount detector to an output voltage, and different output voltages converted by the respective converters are stored. Third adjusting means (the CPU 10 controls the control program stored in the ROM 27 to independently adjust the drive current applied to each light emitting unit so that the light amount of each light beam becomes each reference value based on each reference value. To be adjusted via the adder circuits 17 and 18, the constant current power supplies 19 and 20, and the differential switching circuits 21 and 22). CPU so that the light quantity of each light beam becomes each reference value based on each output voltage obtained by the conversion and each stored different reference value.
10 independently adjusts the drive current to be applied to each of the light emitting units 2 and 3, so that each of the light beams emitted from each of the light emitting units can be easily set on each converting means side. Can be made equal in the vicinity of the exposed portion.

According to the sixth aspect of the present invention, one of the conversion means (the conversion unit COV21 in the present embodiment) changes and sets the current / voltage amplification rate via the variable resistor 30, so that any one of the conversion means is provided on the conversion means side. A target value for one light emitting unit can be easily set.

[Fifth Embodiment] Hereinafter, a fifth embodiment of the present invention will be described with reference to the drawings.

FIG. 7 is a circuit block diagram illustrating the configuration of a light quantity control device according to a fifth embodiment of the present invention. The light quantity control device includes a laser unit LU and a control unit CU.
It is composed of The same components as those in FIG. 1 are denoted by the same reference numerals. The difference from the fourth embodiment is that all the current / voltage conversion efficiency adjusting means for converting the light amount detection current Ipd from the pin photodetector 4 into a voltage is provided on the amplifier circuit side. Accordingly, the adjustment method is the same for each of the light emitting units 2 and 3, and thus the adjustment can be easily performed. The output relationship is the same as the characteristic of FIG. 6 in the fourth embodiment.

As described above, when the light amount of the semiconductor laser element having the plurality of light emitting units 2 and 3 is adjusted by one light amount detecting element, the target value for the detection output can be adjusted independently for each light emitting unit. This makes it possible to control the amount of light on the photosensitive drum surface of each light emitting unit having a different collimator efficiency.

In addition, since the current-voltage conversion efficiency from the detection output (current value) to the voltage can be independently varied by each light emitting unit, it can be implemented at a lower cost, and the adjustment and control can be simplified.

As a result, it is possible to control the light amount of the laser unit having a plurality of light-emitting portions whose light amount characteristics vary, so that a clear image can be recorded.

Hereinafter, the correspondence between this embodiment and each means of the seventh invention and the operation thereof will be described with reference to FIG.

According to a seventh aspect of the present invention, each of the conversion means (the conversion unit COV
21A and 22A), the current / voltage conversion rate is changed and set by the respective variable resistors 37 and 38, so that the conversion means can easily set the target value for any one of the light emitting units.

The above-described first to first embodiments are applied to an image forming apparatus (including a laser beam printer, a digital copying machine printer, etc.) capable of recording an electrostatic latent image on a photosensitive drum based on an input image signal. The light quantity control device shown in the fifth embodiment may be provided (eighth invention).

[0060]

As described above, the first embodiment according to the present invention is described.
According to the invention, at the time of adjusting the light quantity of the exposure means, the first adjusting means is independently controlled so that each output voltage converted by the converting means matches each target light quantity set by each setting means. Since the drive current applied to each light emitting unit is adjusted, the light amount of each light beam emitted from each light emitting unit near the exposure unit is set while individually setting the target value for light amount control according to the variation in the light amount characteristics. Can be matched.

According to the second aspect of the present invention, when adjusting the light amount of the exposure means, each output voltage converted by the conversion means is made to coincide with the target light amount set by the setting means or the stored reference light amount. Since the second adjusting means independently adjusts the driving current applied to each light emitting unit, each of the light emitting units has a simple circuit configuration and individually sets a target value for light amount control in accordance with a variation in light amount characteristics. The light amounts of the respective light beams emitted from the light emitting unit near the exposure unit can be matched.

According to the third aspect, the conversion means changes and sets the current / voltage conversion rate when adjusting the light amount of one of the light emitting units. The value can be set easily.

According to the fourth aspect, the conversion means changes and sets the current / voltage conversion rate by changing and setting the current / voltage amplification rate when adjusting the light amount of one of the light emitting units. The amount of light of each light beam emitted from each light emitting unit in the vicinity of the exposure unit can be matched while easily setting the target value for any one light emitting unit on the conversion unit side.

According to the fifth aspect, at the time of adjusting the light quantity of the exposure means, the light quantity of each light beam is adjusted to each reference value based on each output voltage converted by each conversion means and each different reference value stored. The third adjusting means independently adjusts the drive current applied to each light emitting unit so that each converting means can easily set a target value for each light emitting unit while emitting light from each light emitting unit. The light amount of each light beam in the vicinity of the exposed portion can be made to match.

According to the sixth aspect, since one of the conversion means changes and sets the current / voltage amplification factor, the conversion means can easily set the target value for any one of the light emitting units. .

According to the seventh aspect, since each of the conversion means changes and sets the current / voltage conversion rate, the conversion means can easily set a target value for any one of the light emitting units.

According to the eighth aspect, the light amount control device matches the light amounts of the respective light beams emitted from the respective light emitting portions in the vicinity of the exposed portions, so that an image without image unevenness can be formed.

Accordingly, it is possible to adjust the light amounts of the respective light beams emitted from the respective light emitting portions at the positions to be exposed to the same value, and to form an image without image unevenness.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram illustrating a configuration of a light amount control device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating light amount control characteristics of each light emitting unit shown in FIG.

FIG. 3 is a circuit block diagram illustrating a configuration of a light quantity control device according to a second embodiment of the present invention.

FIG. 4 is a circuit block diagram illustrating a configuration of a light quantity control device according to a third embodiment of the present invention.

FIG. 5 is a circuit block diagram illustrating a configuration of a light quantity control device according to a fourth embodiment of the present invention.

FIG. 6 is a diagram for explaining light amount control characteristics of each light emitting unit shown in FIG.

FIG. 7 is a circuit block diagram illustrating a configuration of a light amount control device according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multi-beam semiconductor laser 2, 3 Light emitting part 4 Pin photodetector 10 CPU

Claims (8)

[Claims] An exposure unit having a plurality of light emitting units for emitting a light beam; a light amount detection unit for detecting a light amount of each light beam emitted from each of the light emitting units; Conversion means for converting an output current corresponding to the light amount of each light beam detected by the detection means into an output voltage, a plurality of setting means for independently setting a different target light amount for each light emitting unit, and conversion by the conversion means A first adjusting means for independently adjusting a driving current applied to each light emitting unit so that each output voltage thus set and each target light quantity set by each setting means coincide with each other. Control device. 2. An exposure unit having a plurality of light emitting units for emitting a light beam, a light amount detecting unit for detecting a light amount of each light beam emitted from each light emitting unit, and the light amount when adjusting the light amount of the exposure unit. A conversion unit for converting an output current corresponding to the light amount of each light beam detected by the detection unit into an output voltage, a setting unit for setting a different target light amount for any of the light emitting units, and each of the conversion units A second adjusting unit for independently adjusting a driving current applied to each light emitting unit so that the output voltage matches the target light amount set by the setting unit or the stored reference light amount. Light intensity control device. 3. The light quantity control device according to claim 1, wherein the conversion means changes and sets the current / voltage conversion rate when adjusting the light quantity of one of the light emitting units. 4. The light quantity control device according to claim 1, wherein the conversion means changes and sets a current / voltage amplification factor when adjusting the light quantity of one of the light emitting units. 5. An exposure unit having a plurality of light emitting units for emitting a light beam, a light amount detection unit for detecting a light amount of each light beam emitted from each light emitting unit, and the light amount when adjusting the light amount of the exposure unit. A plurality of conversion means for converting an output current corresponding to the light amount of each light beam detected by the detection means into an output voltage; and a light source based on each output voltage converted by each conversion means and a different reference value stored. And a third adjusting means for independently adjusting a drive current applied to each light emitting unit so that a light amount of the beam becomes each reference value. 6. The light quantity control device according to claim 5, wherein one of the conversion means changes and sets the current / voltage amplification factor. 7. The light quantity control device according to claim 5, wherein each conversion means changes and sets a current / voltage conversion rate. 8. An image forming apparatus comprising the light quantity control device according to claim 1. Description: