JP5134386B2 - Light quantity control device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a light amount control device for use in an electrophotographic laser beam printer, a copying machine, or the like that scans with a plurality of laser beams from a plurality of laser diodes by an optical scanning unit including a rotating polygon mirror, and an image including the same. The present invention relates to a forming apparatus.

  FIG. 1 is a configuration diagram showing an example of an optical scanning unit using a laser diode. In this figure, 1 is a semiconductor laser diode, 2 is a collimator lens, 3 is a polygon motor, 5 is a rotary polygon mirror, 6 is an fθ lens, 7 is a synchronous detection sensor, 8 is a return mirror, and 9 is a photosensitive drum.

  An image forming apparatus equipped with an optical scanning unit using a laser beam modulates the semiconductor laser diode 1 based on an image signal from a controller and emits a laser beam. The laser beam is deflected in the main scanning direction by the rotary polygon mirror 5 and scanned on the photosensitive drum 9 as an image carrier through an optical system lens such as the fθ lens 6, whereby an electrostatic latent image is obtained. The electrostatic latent image is developed with toner and transferred to paper as a recording material to form an image.

  FIG. 2 shows a light quantity control device using a laser diode drive circuit (LD driver) 56. The LD driver 56 that emits a laser beam by modulating the semiconductor laser diode 1 according to the image data automatically adjusts the light amount of the laser beam based on the reference voltage Vc that determines the light amount of the emitted laser beam and the detection output of the photodiode. Control to adjust.

  In this figure, a semiconductor laser diode 1 includes a laser diode (hereinafter abbreviated as LD) and a photodiode (hereinafter abbreviated as PD). The PD detects the light amount of the LD and outputs a current as a detection output. Here, the detection output is the monitor current Im.

  As shown in FIG. 4, the light amount of the laser beam and the monitor current Im which is the detection output of the PD are in a proportional relationship. The monitor current Im is converted into a voltage by an I / V conversion circuit 41 configured by a resistor. Here, this voltage is set as the monitor voltage Vm. This resistance is referred to as monitor resistance Rm. In the LD driver 56, the comparator 42 compares the monitor voltage Vm with a reference voltage Vc that determines the amount of light emitted by the LD, and controls the drive current so as to always match.

  When the APC signal is “1”, the switch 43 is turned on and becomes conductive, and the hold capacitor Ca is charged or discharged according to the comparison result of the comparator 42. On the other hand, when the APC signal is “0”, the switch 43 is turned OFF and cut off, and the potential of the hold capacitor Ca is maintained. The APC signal is used for AutoPowerControl, and is a signal for periodically adjusting and maintaining the light quantity of the LD, and is repeatedly output for a predetermined time at a constant period.

  The current value of the constant current generated by the current generation circuit 44 is determined in proportion to the potential of the hold capacitor Ca that has been charged and discharged.

  The switch circuit 45 supplies a constant current from the current generation circuit 44 to the LD as a drive current based on the image data and the LD lighting signal. The LD emits light with a predetermined amount of light by the supplied drive current. The PD detects the amount of light from the LD and returns to the comparator 42 via the I / V conversion circuit 41 to configure feedback (or loop) control.

  The photosensitive drum 9 forms an electrostatic latent image by irradiation with a laser beam. This electrostatic latent image is where the surface potential charged by the charger is lowered by the irradiation of the laser beam. The toner adheres to the place where the surface potential is lowered to form a toner image. Since the potential at which the surface potential is lowered is determined by the amount of light irradiated with the laser beam, it is important to adjust the light amount to a predetermined amount in order to prevent deterioration in image quality due to machine differences in the image forming apparatus.

  Further, the half-exposure characteristic (or attenuation characteristic of the surface potential) with respect to the amount of light changes depending on the temperature and humidity around the photosensitive drum 9 in the image forming apparatus and the secular change of the photosensitive drum 9. For this reason, it is necessary to change the emitted light amount in accordance with the environmental change in the image forming apparatus, the temperature and humidity change around the photosensitive drum, and the secular change of the photosensitive drum 9 with respect to the initially adjusted light amount. . In addition, it is necessary that the amount of light emitted by all the LDs be aligned at substantially the same value until the life of the photosensitive drum.

  In this way, when the emitted light quantity is increased or decreased with respect to the initially adjusted light quantity, it is important that the light quantities of all the LDs are even after the increase or decrease.

Japanese Examined Patent Publication No. 7-54957

  In an optical scanning unit using a plurality of LDs, if the light quantity of each LD is not uniform, the surface potential due to laser beam irradiation becomes uneven. This unevenness in potential affects the amount of adhering toner, resulting in an image having color misregistration, shading unevenness, and streaks. For this reason, it is necessary to adjust so that the light quantity of each LD is equal.

  FIG. 3 shows one configuration example of the semiconductor laser diode 1 incorporating a plurality of LDs and PDs. In this figure, for the sake of simplicity, the number of LDs is three. From this figure, three LD1, LD2, and LD3 are formed on the same chip, and laser beams B1, B2, and B3 are emitted from two end faces. The front laser beam in the figure is emitted from a semiconductor laser diode and used for image formation as a light source of an optical scanning unit. On the other hand, the laser beam on the far side in the figure is for detecting the amount of light and is emitted to a PD as a light receiving element for detecting the amount of light.

  In a scanning optical unit using a plurality of LDs, a monitor current Im, which is a detection output of a PD that detects a predetermined light amount of the LD, is an individual even if a laser diode array in which a plurality of LDs are formed on the same chip. It depends on the LD.

  In addition, the deviation of the monitor current Im becomes a large value depending on the combination of the variation in the electrical characteristics of the PD and the variation in the electrical characteristics of the LD and the mounting position (mechanical characteristics) thereof.

FIG. 13 shows a configuration of the I / V conversion circuit 41 as current-voltage conversion means. In this figure, the I / V conversion circuit 41 includes a fixed resistor R3 and a variable resistor VR2, and is referred to as a monitor resistor Rm as a combined resistance thereof. Here, the fixed resistor R3 is a protective resistor for preventing the amount of light exceeding the rating of the LD from being emitted when adjusting the monitor resistor Rm. In the light quantity control circuit, the PD detection output Im is converted into the monitor voltage Vm by the monitor resistor Rm of the I / V conversion circuit 41. Here, Vm is a voltage between the power supply Vcc and the cathode of the PD. From this,
Vm = Rm × Im (Formula 1)
It can be expressed.

Further, the control voltage Vm is controlled so that the reference voltage Vc always coincides with the setting of the light quantity. From this,
Vc = Rm × Im (Formula 2)
It can be expressed.

  From (Equation 2), if the reference voltage Vc is constant, the monitor resistance Rm and the monitor current Im are in an inversely proportional relationship. If the monitor current Im is constant, the reference voltage Vc and the monitor resistor Rm are in a proportional relationship.

  The reference voltage Vc needs to have a high S / N ratio in order to avoid the influence of noise, and it is desirable to set the reference voltage Vc to a high voltage.

  Further, the monitor voltage Vm is controlled so as to coincide with the reference voltage Vc. However, if the monitor resistance Rm is too large, an oscillation phenomenon may occur or the response characteristics of the monitor voltage Vm may deteriorate.

  For these reasons, in the optical scanning unit using a plurality of LDs, it is necessary to adjust the resistance value of the monitor resistor Rm in order to optimize the reference voltage Vc and the monitor voltage Vm. In order to obtain a predetermined amount of light, it is necessary to adjust the monitor resistance Rm.

  In order to adjust the resistance value of the monitor resistor Rm, it is necessary to cause the laser diode to emit light, but the monitor current Im changes according to the light amount. FIG. 6 shows an inversely proportional relationship between the monitor resistance Rm and the monitor current Im when the reference voltage has a relationship of Vc1 <Vc2 <Vc3. In this figure, when the reference voltage Vc is low, the monitor current change amount ΔIm is smaller than the resistance value change amount ΔRm. As the reference voltage Vc increases, the change amount ΔIm of the monitor current increases with respect to the change amount ΔRm of the resistance value.

  As described above, since the monitor resistance Rm and the monitor current Im are in an inversely proportional relationship, the change amount ΔP of the light amount with respect to the change amount ΔRm of the monitor resistor Rm due to the light amount adjustment is the voltage of the reference voltage Vc. Depending on the situation. For this reason, there is a problem that, as the amount of emitted light increases, adjusting the resistance value of the monitor resistor Rm to set the predetermined amount of light makes adjustment work difficult and adjustment error increases.

  In addition, when a predetermined amount of light is adjusted for a plurality of LDs, since the deviation of the monitor current Im is large for each LD, a range in which the second reference voltage Vc divided by all the LDs can be adjusted by the voltage dividing resistor Ra. Therefore, it is necessary to match the reference voltage Vc of the LD, which serves as a reference when adjusting the amount of light, near the center of the adjustable range of the voltage dividing resistor Ra. However, there is a problem that, depending on the LD having a large deviation of the monitor current Im, it cannot be adjusted within the range in which the voltage dividing resistor Ra can be adjusted, resulting in a defective product.

  In addition, as shown in FIG. 5, since the monitor current Im differs depending on the individual LD, if the light quantity emitted by each LD is made uniform, the reference voltage Vc of each LD varies and a plurality of LDs are incorporated. In the laser diode array, there is a problem that the number of individual control processes becomes more complicated as the number of built-in LDs.

  The present invention has been made in view of such a problem, and when adjusting the resistance value of the monitor resistor Rm to set a predetermined light amount, the adjustment work can be easily performed while suppressing the light amount emitted. An object of the present invention is to provide a light amount control device with little error and an image forming apparatus using the same.

  It is another object of the present invention to provide a light quantity control device that eliminates the determination that the voltage dividing resistance Ra cannot be determined as a defective product because it cannot be adjusted within the range in which the voltage dividing resistor Ra can be adjusted by adjusting the light quantity.

  It is another object of the present invention to provide a light quantity control device that is provided with means for eliminating the influence of the monitor current Im that varies depending on the individual LD, and that can control the quantity of light emitted by each LD by common control.

To achieve the above object, a plurality of light emitting elements for image formation, a light intensity detection light receiving element for detecting the light quantity of the light emitting element, a first reference voltage for determining a plurality of light emitting elements of each light quantity First reference voltage generating means for generating the first reference voltage , second reference voltage adjusting means for adjusting the second reference voltage by dividing the first reference voltage, and detection output of the light receiving element for detecting the light amount in the light quantity control device for controlling the light amount of the light emitting element based on the monitor voltage converting means for converting the monitor voltage, the second reference voltage and the detection output of said light intensity detection light-receiving element, said plurality of light emitting elements Are set as a reference light-emitting element and another light-emitting element, a first reference voltage for determining the light quantity of each of the plurality of light-emitting elements is set, and a second reference corresponding to the reference light-emitting element is set By voltage adjustment means The minimum voltage in the voltage dividing adjustment range of the second reference voltage is set, and the monitor voltage conversion means temporarily adjusts the light amount of the reference light emitting element to a temporary value smaller than a target value, The light quantity control device is configured to adjust the light quantity of the light emitting element serving as the reference to a target value by adjusting within the partial pressure adjustment range of the second reference voltage by the adjusting means.

Further, after the light amount of the reference light emitting element reaches a target value, the second reference voltage adjusting means detects the light amount of the other light emitting element based on the detection output of the light receiving element for detection. Adjustment is made so that the light quantity of the other light emitting elements becomes the target value.

Further, when the light quantity of the other light emitting element cannot be set to the target value within the partial pressure adjustment range, the temporary value is changed.

Also, image formation equipped with an optical scanning unit having a plurality of light emitting elements for image formation, a light amount detecting light receiving element for detecting the light quantity of the light emitting elements, and a light quantity control device for adjusting the light quantity of the plurality of light emitting elements. the apparatus is characterized by using the light quantity control device.

  In the present invention, the second reference voltage adjusting means is provided as means for eliminating the influence of the monitor current Im that varies depending on the individual LDs, and the amount of light emitted by each LD can be implemented by common control.

  Further, as a means for eliminating the influence of the monitor current Im that varies depending on each LD, the voltage dividing resistor Ra as the second reference voltage adjusting means is adjusted to set the reference voltage Vc to the minimum, and the light amount of the light emitting element is set to a predetermined value. Temporarily adjust to a temporary value smaller than the target value. This temporary value is not fixed, but is set so that the reference voltage Vc can be adjusted within the range in which the voltage dividing resistor Ra can be adjusted even if the deviation of the monitor current Im is large depending on the individual LD. For this reason, it is not necessary to adjust the reference voltage Vc of the LD, which is a reference when adjusting the light amount, to the vicinity of the center of the range where the voltage dividing resistor can be adjusted, and the monitor current Im flowing according to the light amount can be minimized, The change amount ΔP of the light amount can be suppressed to the minimum change amount with respect to the change amount ΔRm of the resistance value of the monitor resistor Rm.

  In addition, the provisional light amount determines the resistance value of the monitor resistor, and does not determine the light amount, so it should be lower than the light amount actually adjusted. If there is an LD that cannot be adjusted to a predetermined light amount, this temporary light amount may be changed so that it can be adjusted to the predetermined light amount. For this reason, the voltage dividing resistor Ra cannot be adjusted, and is not determined as a defective product.

  The purpose of providing a light quantity control device that facilitates the adjustment of the quantity of light and has a small adjustment error is to provide a second reference voltage adjusting means for the predetermined first reference voltage of the first reference voltage generating means. The second reference voltage adjusting means sets the minimum voltage in the second reference voltage division adjustment range, and the detection output of the light quantity detecting light receiving element is temporarily set to a temporary value smaller than a predetermined target value. Realized by adjusting to.

  FIG. 8 is a block diagram showing an embodiment of the light quantity control device of the present invention. LD1 and LD2 are laser diodes as light emitting elements, PD is a photodiode as a light receiving element, and 12 is a current-voltage converting means. Monitor resistor, 51 is CPU, 52 is ROM, 53 is an image processing unit (hereinafter referred to as IPU), 54a and 54b are DACs (Digital Analog Converter) as first reference voltage generating means, and 55a and 55b are second reference voltages. Voltage dividing resistors 56a and 56b as adjustment means are LD drivers as automatic light quantity control means.

  The CPU 51 controls the entire image forming apparatus with setting data and a control program written in the ROM 52 to form an image as the image forming apparatus. The ROM 52 stores a control program for the image forming apparatus and related data. The IPU 53 outputs the respective light amount setting data Data1 and Data2 to the DACs 54a and 54b as the first reference voltage generation means in order to set the light amount of the LD in accordance with the instruction of the CPU 51. Also, the LD emits light, generates a synchronization signal, and processes the image data from the host, outputs it to the LD driver, generates an APC signal, etc. based on the synchronization signal returned.

  The DACs 54a and 54b, which are first reference voltage generation means, generate analog reference voltages Vr1 and Vr2 from the respective light amount setting data Data1 and Data2.

  The voltage dividing resistors 55a and 55b serving as the second reference voltage adjusting means generate the second reference voltages Vc1 and Vc2 from the input first reference voltages Vr1 and Vr2.

FIG. 12 shows the configuration of one embodiment of the voltage dividing resistor Ra as the second reference voltage adjusting means according to the present invention. In this figure, the voltage dividing resistor Ra is composed of fixed resistors R1 and R2 and a variable resistor VR1, and the second reference voltage Vc is Vc = Vr × R2 / (R1 + R2 + VR1) with respect to the input first reference voltage Vr. ) ... (Formula 3)
It can be expressed as

Here, when the variable resistor VR1 has the maximum resistance value (here, VR1m), the second reference voltage Vc is minimum (here, VL). VL = Vr × R2 / (R1 + R2 + VR1m) ( Formula 4)
It can be expressed as

Further, since the resistance value is wired to be 0Ω when the variable resistance VR1 is minimum, the second reference voltage Vc is maximum (here, VH), and VH = Vr × R2 / (R1 + R2) ... (Formula 5)
It can be expressed as

  Next, the light quantity adjustment work of the present invention will be described using the flowchart shown in FIG.

  First, in order to obtain a predetermined light amount P, the light amount setting data of all LDs is set in the DAC 54 which is the first reference voltage generating means to generate the first reference voltage Vr (step S10).

  Next, the second reference voltage is adjusted by adjusting the variable resistor VR1 of the voltage dividing resistor 55a, which is the second reference voltage adjusting means corresponding to the LD (here, LD1) serving as a reference for adjusting the light amount. Vc is minimized (step S20). As described above with Expression 4, in the configuration example of FIG. 12, when the resistance value of the variable resistor VR1 is the maximum, the second reference voltage Vc is the minimum VL.

  Next, while measuring the light quantity of the LD 1 serving as a reference for adjusting the light quantity with the optical power meter, in the configuration example of FIG. 13 described above, the resistance value of the variable resistor VR2 constituting the monitor resistor Rm is adjusted to be predetermined. Is temporarily adjusted to a temporary value P0 smaller than the target value (step S30). As described above, since the monitor resistance Vm and the monitor current Im are in an inversely proportional relationship, the light amount is adjusted by gradually decreasing the resistance value of the variable resistor VR2.

  Next, the variable resistor VR1 of the voltage dividing resistor 55a is adjusted while measuring the light amount of the LD 1 serving as a reference for adjusting the light amount with an optical power meter to adjust the light amount of the LD 1 to a predetermined P value (step S40). ). When the resistance value of the variable resistor VR1 is gradually decreased, the second reference voltage Vc gradually increases, and the amount of light emitted by the LD1 increases.

  Next, the variable resistor VR1 of the voltage dividing resistor 55b, which is the second reference voltage adjusting means corresponding to the LD2, is measured while measuring the light amount of the LD2 other than the LD1 serving as a reference for adjusting the light amount with an optical power meter. The light quantity is adjusted to a predetermined value P (step S50).

  Next, it is determined whether or not the adjustment is possible within the adjustment range of the voltage dividing resistor which is the second reference voltage adjusting means. If possible, the process proceeds to step S80, and if not possible, the process proceeds to step S70 (step S60). .

  If it is determined in step S60 that it is not possible, the temporary light quantity P0 is slightly changed and the process returns to step S30 (step S70).

  If it is determined in step S60 that it is possible, it is determined whether the light amount adjustment for all channels has been completed. If not, the process returns to step S50. If completed, the adjustment work is completed (END).

  Next, the light quantity adjustment work of the present invention will be described with reference to FIGS.

  In FIG. 7A, in step S10, the light quantity setting data of all the LDs is set in the DAC 54 which is the first reference voltage generating means, and the first reference voltage Vr is generated. The second reference voltage Vc that can be adjusted by the variable resistor VR1 of the voltage dividing resistor 55a that is the second reference voltage adjusting means for the first reference voltage Vr is from the minimum VL to the maximum VH. In step S20, the second reference voltage Vc becomes the minimum VL. In step 30, the light quantity of LD1 used as a reference for adjusting the light quantity is temporarily adjusted to a temporary value P0 smaller than a predetermined target value by adjusting the resistance value of the variable resistor VR2 constituting the monitor resistor Rm. (61).

  In FIG. 7B, in step S40, the variable resistor VR1 of the voltage dividing resistor 55a is adjusted to measure the light amount of the LD1 while measuring the light amount of the LD1 serving as a reference for adjusting the light amount with an optical power meter. The P value is adjusted (62).

  In FIG.7 (c), in step S50, adjusting the variable resistance VR1 of the voltage dividing resistor 55b which is the 2nd reference voltage adjustment means corresponding to LD2 while measuring the light quantity of LD2 with an optical power meter, light quantity is adjusted. It is adjusted to a predetermined value P (63).

Thereafter, step S50 is repeatedly executed to adjust all LDs to a predetermined light amount P.
Next, as for the fixed resistors used for the voltage dividing resistor Ra and the monitor resistor Rm, the difference (accuracy) between individual constants and actual resistance values can be obtained with a cost of ± 1% without cost. Due to the structure of the variable resistor, it is difficult to improve accuracy, and the difference between the individual constants and the actual resistance value is much larger than that of the fixed resistor.

  FIG. 10 considers the accuracy of the resistance value of the variable resistor VR1 described above, and the voltage dividing resistor Ra as the second reference voltage adjusting means with respect to the set value Vr of the DAC 54 as the first reference voltage generating means. This represents the adjustment range. As shown in Equation 4, when the resistance value of the variable resistor VR1 is maximum, the second reference voltage Vc is minimum (91). For this reason, the accuracy of the resistance value of the variable resistor VR1 affects only when the second reference voltage Vc is minimum.

  In FIG. 10, if the accuracy of the variable resistor VR1 is on the + side, the second reference voltage Vc becomes ΔV1 lower than VL when it takes the minimum (92). On the other hand, if the accuracy of the variable resistor VR1 is −side, the second reference voltage Vc becomes ΔV2 higher than VL when the minimum is taken (93).

  Next, in FIG. 11A and FIG. 11B, the influence on the light amount adjustment work by the accuracy of the resistance value of the variable resistor will be described. A case where the accuracy of the variable resistor VR1 is on the + side will be described with reference to FIG. As described above, if the accuracy is on the + side, the minimum reference voltage Vc that can be adjusted by the voltage dividing resistor is VL−ΔV1. With this reference voltage, the provisional light quantity P0 is adjusted (81). Next, the variable resistor Ra is adjusted and adjusted to the original light amount P within the adjustable range from the reference voltage VL-ΔV1 to VH (82). If the predetermined light quantity P cannot be adjusted within the variable resistor adjustment range, the temporary light quantity P0 is slightly lowered and adjusted again. The provisional light amount P0 determines the resistance value of the monitor resistor, and therefore does not affect the predetermined light amount P. If the value of the provisional light quantity P0 is adjusted, it is not impossible to adjust even an LD having various light quantity and monitor current Im characteristics.

  The case where the accuracy of the variable resistor VR1 is on the negative side will be described with reference to FIG. As described above, if the accuracy is −side, the minimum reference voltage Vc that can be adjusted by the voltage dividing resistor is VL + ΔV2. With this reference voltage, the provisional light quantity P0 is adjusted (83). Next, the variable resistor Ra is adjusted and adjusted to the original light amount P within the adjustable range from the reference voltage VL + ΔV2 to VH (84). If the predetermined light quantity P cannot be adjusted within the variable resistor adjustment range, the temporary light quantity P0 is slightly increased and adjusted again. The provisional light amount P0 determines the resistance value of the monitor resistor, and therefore does not affect the predetermined light amount P. If the value of the provisional light quantity P0 is adjusted, it is not impossible to adjust even an LD having various light quantity and monitor current Im characteristics.

  In this way, even if the variable resistor is less accurate than the fixed resistor, if the provisional light quantity P0 is adjusted, it can always be adjusted to the predetermined light quantity within the adjustment range of the voltage dividing resistor, and it becomes a defective product. Absent.

  As described above, in the image forming apparatus using the light amount adjusting unit and the light amount adjusting method according to the present invention, all the setting values for generating the reference voltage are set regardless of the total number of LDs incorporated in the laser diode array. The LD can be aligned with a predetermined light quantity P.

It is a block diagram which shows an example of the optical scanning unit using the laser diode concerning this invention. It is a block diagram which shows the structure of the light quantity control apparatus concerning this invention. It is a block diagram of a semiconductor laser diode incorporating a plurality of laser diodes and photodiodes. It is a characteristic view showing the relationship between the light quantity of the laser diode and the monitor current of the photodiode. FIG. 6 is a characteristic diagram showing that there is a difference in the amount of light emitted from a plurality of laser diodes with respect to a reference voltage. It is a characteristic view showing the relationship between the resistance value of the monitor resistor due to the difference in the reference voltage and the monitor current. It is a characteristic view for demonstrating the adjustment method of the light quantity adjustment concerning this invention. It is a block diagram which shows the Example of the light quantity control apparatus concerning this invention. It is a flowchart for demonstrating the adjustment method of the light quantity adjustment concerning this invention. It is a characteristic view for demonstrating the adjustment method of the light quantity adjustment concerning this invention. It is a characteristic view for demonstrating the adjustment method of the light quantity adjustment concerning this invention. It is a block diagram which shows the structure of the voltage dividing resistance as the 2nd reference voltage adjustment means concerning this invention. It is a block diagram which shows the structure of the monitor resistance as a current-voltage conversion means concerning this invention.

Explanation of symbols

1: semiconductor laser diode array, 2: collimator lens, 3: polygon motor, 5: rotating polygon mirror, 6: fθ lens, 7: synchronous detection sensor, 8: return mirror, 9: photosensitive drum, 12: monitor resistor, 41: I / V conversion circuit, 42: comparator, 43: switch, 44: current generation circuit, 45: switch circuit, 51: CPU, 52: ROM, 53: IPU, 54: DAC, 55: voltage dividing resistor, 56 : LD driver.

Claims (4)

A plurality of light emitting elements for image formation, a light amount detecting light receiving element for detecting a light amount of the light emitting element, and
First reference voltage generating means for generating a first reference voltage for determining the amount of light of each of the plurality of light emitting elements;
A second reference voltage adjusting means for adjusting the second reference voltage by a partial pressure adjusting said first reference voltage,
A monitor voltage converting means for converting the detection output of said light intensity detection light receiving element in the monitor voltage,
In the light quantity control device for controlling the light quantity of the light emitting element based on the second reference voltage and the detection output of the light quantity detecting light receiving element ,
The plurality of light emitting elements are set as a reference light emitting element and another light emitting element,
Setting a first reference voltage for determining the amount of light of each of the plurality of light emitting elements;
The second reference voltage adjusting means corresponding to the light emitting element serving as the reference is set to the minimum voltage in the voltage dividing adjustment range of the second reference voltage,
The monitor voltage conversion means temporarily adjusts the light amount of the reference light emitting element to a temporary value smaller than a target value,
The light quantity control device, wherein the second adjustment means is adjusted within a partial pressure adjustment range of the second reference voltage so that the light quantity of the reference light emitting element becomes a target value. After the light amount of the reference light emitting element reaches a target value, the second reference voltage adjusting means detects the other light emitting element based on the detection output of the light receiving element for detection. The light quantity control device according to claim 1, wherein the light quantity of the light emitting element is adjusted so as to become a target value. The light quantity control device according to claim 2, wherein when the light quantity of the other light emitting element cannot be set as a target value within the partial pressure adjustment range, the temporary value is changed. In an image forming apparatus equipped with an optical scanning unit having a plurality of light emitting elements for image formation, a light amount detecting light receiving element for detecting the light amount of the light emitting elements, and a light amount control device for adjusting the light amount of the plurality of light emitting elements. ,
An image forming apparatus using the light quantity control device according to any one of claims 1 to 3 .

Images