JPH10138562A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the irregularity of quantity of light by modulating the drive current of a multibeam laser diode in timing wherein the adjacent elements of the multibeam laser diode emit lights. SOLUTION: Drive current sources 57a, 57b set the current values for correcting quantity of light of laser diodes 51a, 51b according to signals DA3, DA4 of the D/A converter of a main control part 40 and, when the video signals VD1, VD2 outputted from the video terminals 41a, 41b of the main control part 40 are together in an ON-state, switching circuits 58a, 58b are together turned ON and the correction current value is added to the laser drive current value set by drive current sources 56a, 56b. By this constitution, when both of the laser diodes 51a, 51b emit lights, it is avoided that the quantity of emitted light becomes lower than desired quantity of light by mutual heat interference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which is used in a laser beam printer, a digital copying machine, etc. and drives a multi-beam laser diode to perform optical writing.

[0002]

2. Description of the Related Art FIG. 8 shows a configuration diagram of a conventional laser diode driving circuit. A main control unit 1 for performing image processing of a laser printer and sequence processing such as paper conveyance is provided with a video terminal 2, a D / A converter. 3. An A / D converter 4 is provided. In the laser diode drive circuit 5 connected to the main control unit 1, a laser diode 6 and a photodiode 7 are housed in the same package 8.

The video output of the video terminal 1 of the main controller 1 is connected to a switching circuit 9 of a drive circuit 5 and further to a laser diode 6. The output from the D / A converter 3 of the main control unit 1 is connected to a constant current circuit 10, and the output of the constant current circuit 10 is connected to a switching circuit 9. The output of the constant current circuit 10 is connected to the photodiode 7 via the variable resistor 11 and to the A / D converter 4 of the main control unit 1 via the amplifier 12.

The switching circuit 9 controls the on / off of the laser diode 6 in accordance with the video signal VD of the main control unit 1, and the constant current circuit 10 controls the D / A converter 3 of the main control unit 1.
Is set according to the output voltage signal from the laser diode 6. The amount of light emitted from the laser diode 6 is converted into a photocurrent by the photodiode 7, further converted into a voltage by the variable resistor 11, and input to the A / A of the main control unit 1 via the amplifier 12 as an input voltage signal.
It is input to the D converter 4. The variable resistor 11 adjusts the photoelectric conversion efficiency between the laser diode 6 and the photodiode 7 and the dispersion of the optical system, and adjusts the signal to the A / D converter 4 of the main control unit 1 and the light amount on the photoreceptor by one. It corresponds to one to one. It should be noted that these adjustments are actually performed at the factory to be shipped.

In the following description, the light amount control performed before forming a latent image on the photoreceptor is referred to as pre-rotation light amount control, and the light amount control performed between recording paper conveyances during continuous printing is referred to as inter-sheet light amount. Let's call it control.

First, in the case of the sequence processing of the pre-rotation light amount control, as shown in the flow chart of FIG. 9, the main control unit 1 sets the digital signal DA input to the D / A converter 3 as an initial value in step S1 in step S1. Is set to “0”. Then, in step S2, the video signal is turned on. In step S3, the signal DA is incremented by "1". In step S4, the value of the digital signal AD converted by the A / D converter 4 is checked each time. To determine whether or not the laser light amount has reached the target value APC. That is, if AD ≧ APC, it is determined that the light emission amount of the laser diode 6 has reached the target value, the signal DA is reduced by “1” in step S5, the video signal VD is turned off, and the pre-rotation light amount control is performed. finish. Finally, set signal DA to “1”.
The reason for this is that the amount of light emitted from the laser diode 6 is corrected downward so that the amount of light does not exceed the target value APC.

If AD <APC in step S4, it is determined that the light emission amount of the laser diode 6 has not reached the target value, and the process returns to step S3. Therefore, the signal DA is the target value
Steps S3 and S4 are repeated until APC is reached. After the end of the pre-rotation light amount control, the main control unit 1 performs an image forming operation, that is, a printing operation, by the video signal VD with the set value of the signal DA.

Next, in the case of inter-sheet light quantity control, as shown in the flowchart of FIG.
Performs a fine-tuning operation to compare with the target value APC. Step S10
Turns on the video signal VD, and determines in step S11 whether it is larger or smaller than the target value APC. If it is larger than the target value APC in step S12, the signal DA is reduced by "1" in step S13, and the signal AD and the target value AP are reduced in step S13.
Compare the size with C. Then, in step S13, the signal
If AD is smaller than the target value APC, the inter-sheet light amount control ends. If the signal AD is larger than the target value APC in Step S13, the process returns to Step S12, and Steps S12 and
Repeat S13.

On the other hand, in step S11, the signal AD is set to the target value APC.
If it is smaller, the signal DA is increased by "1" in step S14, and the signal AD is compared with the target value APC in step S15. Then, Step S14 and Step S15 are repeated until the signal AD becomes larger than the target value APC in Step S15. If the signal AD exceeds the target value APC in step S15, the signal DA is decreased by "1" in step S16 and the step
In step S17, the video signal VD is turned off, and the inter-sheet light amount control ends. After the inter-sheet light amount control is completed, the main controller 1 sets the set signal.
The image forming operation is performed by the video signal VD with the value of DA.

In recent years, there has been a demand for high-speed and high-definition printers.
Some devices have exceeded 10,000 rotations. However, as the rotation speed of the scanner motor increases, cost and technical problems become important. For this reason, there is an apparatus which can respond to high speed and high definition without increasing the rotation speed of a scanner motor by using a plurality of laser diodes as a light source.

For example, as shown in FIG. 11, there is known a laser beam printer in which a plurality of laser units are provided and a laser beam is simultaneously scanned on a photosensitive member to perform writing. In this device, two laser diodes 20
The laser beams emitted from the laser units 22a and 22b including the laser beams a and 20b and the collimator lenses 21a and 21b are transmitted through the light splitting member 23 to the polygon mirror 2.
Focus on 4 The polygon mirror 24 is rotated at a high speed by a scanner motor (not shown), and this light beam forms a scanning image on a photoreceptor 26 by a scanning lens 25.

However, since this method has a complicated structure and is largely restricted in terms of space, it is conceivable to use a multi-beam laser diode having a plurality of laser diodes in one chip, as shown in FIG. Two-element laser diodes 30a, 30b and one
An element photodiode 31 is provided, and the output of each of the laser diodes 30a and 30b is controlled by one photodiode 31. As shown in FIG. 13, the laser diodes 30a and 30b have active layers 33a and 33b and light emitting points 34a and 34b, respectively, arranged on both sides of the central dividing groove 32. By arranging the 30b in an array structure, the number of light emitting elements can be increased.

[0013]

However, when the multi-beam laser diodes 30a and 30b are used as light emitting elements as in the above-described conventional image forming apparatus, thermal crosstalk between the light emitting elements is caused. In addition, the thermal characteristics of the laser diodes 30a and 30b are inferior to those of the single light emitting element, and the adjacent laser diodes 30a and 30b
b causes thermal interference between the laser diodes 30a,
In addition to the change in light amount due to the light emission of 0b itself, a change in light amount occurs due to the light emission of the adjacent laser diodes 30a and 30b. Therefore, there is a problem in that the amount of laser light irradiated on the photoreceptor varies due to an image pattern output from a device such as a laser beam printer, which affects the image density.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide an image forming apparatus in which a driving current of a laser diode is modulated at a timing at which an element adjacent to a multi-beam laser diode emits light to suppress variation in light amount.

[0015]

In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus using an electrophotographic process for forming an electrostatic latent image on a photosensitive member. At least two light-emitting elements comprising: a light-detecting element for detecting a light beam from the light-emitting element; a package integrally storing the light-emitting element and the light-detecting element; A first current setting unit that sets a drive current that emits light at a light amount; and a first switching unit that turns on / off a connection between the first current setting unit and the light emitting element; The circuit included in the current setting unit and the first switching unit includes:
The number of the light emitting elements is the same as that of the light emitting elements, and the light emitting elements are operated in one-to-one correspondence.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a configuration diagram of a laser diode driving circuit according to a first embodiment. A main control unit 40 which performs a sequence process such as image processing of a laser beam printer and sheet conveyance is provided with two video terminals 41a and 4a.
1b, two terminals 42a, 42b of the D / A converter 42,
The two terminals 43a and 43b of the D / A converter 43 and the A / D
A terminal of the converter 44 and an I / O terminal 45 are provided.
In the laser diode driving circuit 50, two laser diodes 51a and 51b and a photodiode 5
2 are housed in the same package 53.

The video terminals 41a and 41b of the main control unit 40
Are output from the switching circuit 5 of the drive circuit 50, respectively.
4a, 54b, the switching circuits 54a, 5b
The outputs of 4b are laser diodes 51a, 5d, respectively.
1b. In addition, video terminals 41a, 41
The output of b is connected to the input of the NAND logic circuit 55. The output of the D / A converter 42 of the main control unit 40 is connected to driving current sources 56a and 56b, respectively, and the output of the D / A converter 43 is connected to driving current sources 57a and 57b, respectively. The outputs of the drive current sources 57a and 57b are
They are added to the outputs of the drive current sources 56a and 56b via the switching circuits 58a and 58b, respectively, and are connected to the switching boxes 54a and 54b. The outputs of the drive current sources 56a, 56b, 57a, 57b are connected to each other, and one end is grounded.

The output of the photodiode 52 is connected to a variable resistor 59, an amplifier 60, and a comparator 61. A resistor 62 is connected to the amplifier 60 in series, and a resistor 63 is connected in parallel. A / D converter 4 of control unit 40
4 is connected. The comparator 61 has a variable resistor 6.
4 are connected in series, the resistor 65 is connected in parallel, and the output of the comparator 61 is connected to the I / O terminal 45 of the main control unit 40.

As described above, for the laser diode 51a, the video terminal 41a of the main controller 40, the D / A converters 42a and 43a, the switching circuits 54a and 58a of the drive circuit 50, the drive current sources 56a and 57a, Amplifier 6
0, the video terminal 42b of the main controller 40, the D / A converters 42b and 43b, and the switching circuit 54 of the drive circuit 50 for the laser diode 51b.
b, 58b, drive current sources 56b, 57b, and a comparator 61 are provided.

In the above configuration, the switching circuit 5
4a and 54b are video signals VD1 and VD from the main control unit 40.
2, the laser diodes 51a and 51b are turned on / off, respectively, and this signal is a low active signal that turns on the laser diodes 51a and 51b when "0" and turns off when "1". The driving current sources 56a and 56b are provided with the signals DA1 and DA2 of the D / A converters 42a and 42b of the main control unit 40.
, The value of the drive current flowing through the laser diodes 51a and 51b is set. The light emission amount of the laser diode 51 a is converted into a photocurrent by the photodiode 52, and is converted into a voltage by the variable resistor 59. Then, after being amplified by the amplifier 60, the A / D converter 4 of the main control unit 40
The signal AD is used as the signal AD.

The amount of light emitted from the laser diode 51b is
After being converted into a voltage by the variable resistor 59, the voltage is compared with a reference voltage by the comparator 61, and “1” or “0” is determined by the main control unit 40.
Is output to the I / O terminal 45. In this case, the digital data I / O input to the I / O terminal 45 is I / O = 0 when the laser diode 51b exceeds the target light amount.
= 1 is equal to or less than the target light amount. The reference voltage at this time is the power supply voltage Vc, the resistor 65, and the variable resistor 64.
Is determined by

The variable resistor 59 includes a laser diode 51a.
It is for adjusting the photoelectric conversion efficiency and the variation of the optical system between the photodetector 52 and the photodiode 52 so that the signal AD of the A / D converter 44 of the main control unit 40 and the light quantity on the photoconductor correspond one to one. . In addition, since there is variation between the laser diodes 51a and 51b,
b, the variation in the photoelectric conversion efficiency and the optical system
4 is adjusted. Actually, the laser diodes 51a and 51b emit light with a desired light quantity in a factory assembling process so that the signal AD to the A / D converter 44 and the reference voltage of the comparator 61 at this time become a predetermined voltage. , The variable resistors 59 and 64 are adjusted.

On the circuit, the amplifier 60 is distributed to the laser diode 51a.
Although the comparator 61 is assigned to b, the laser diode 51a and 51b are composed of two elements, whereas the photodiode 52 is composed of one element, so that it is necessary to perform control division. . Drive current source 57
Reference numerals a and 57b denote laser diodes 51a and 51b in accordance with signals DA3 and DA4 from the D / A converter 43 of the main control unit 40.
A current value for light quantity correction of 1b is set, and the set correction current value is turned on / off by the switching circuits 58a and 58b. When the switching circuits 58a and 58b are on, the correction current value is equal to the drive current sources 56a and 56b.
Is added to the laser drive current value set in.

The switching circuits 58a, 58b
Is turned on when the video signals VD1 and VD2 output from the video terminals 41a and 41b of the main controller 40 are both on, that is, when both of the video signals VD1 and VD2 are "0". Thus, when both the laser diodes 51a and 51b emit light, it is possible to compensate for the fact that the light emission amount becomes lower than the desired light amount due to thermal interference between them by adding the correction current value.

FIG. 2 is a flowchart of the pre-rotation light quantity control. This pre-rotation light quantity control is a light quantity control performed before a latent image is formed on the photosensitive member. In the main control unit 40,
In step S20, the signals DA1, DA2, DA3 and DA4 of the D / A converters 42 and 43 are set to "0" as initial values. Thereafter, in step S21, the video signal VD1 is turned on, and the signal VD1 is turned on.
2 is turned off, the signal DA1 is incremented by a predetermined value "K" in step S22, and the value of the signal AD of the A / D converter 44 is checked each time in step S23, and whether the target value APC has been reached is checked. Determine whether or not.

That is, if AD ≧ APC, it is determined that the light emission amount of the laser diode 51a has reached the target value, the signal DA1 is decreased by "1" in step S24, and the video signal VD1 is turned off in step S25. The pre-rotation light amount control for the laser diode 51a ends. Finally, the reason why the signal DA1 is decremented by 1 is to correct downward so that the amount of light emitted from the laser diode 54a does not exceed the target value APC. If AD <APC in step S23, the light emission amount of the laser diode 51a is equal to the target value AP.
It is determined that C has not been reached, and the process returns to step S22. Therefore, until the signal DA1 reaches the target value APC, step S2
Step 2 and Step S23 are repeated.

Next, the pre-rotation light amount control for the laser diode 51b is performed. In step S26, the video signal VD2
Is turned on, the signal DA2 is incremented by "K" in step S27, and in step S28, the digital data I / O
Is checked, and it is determined whether or not the laser diode 51b has reached the target light amount. That is, if digital data I / O = 0 in step S29, the laser diode 51b
Is determined to have reached the target value, and the signal at this time
After storing the value of AD as APC2, the signal is
Decrease DA2 by "K". Then, the pre-rotation light amount control for the laser diode 51b is terminated, and APC2 at this time is set as the target value of the laser diode 51b. If digital data I / O = 1 in step S28,
It is determined that the amount of light emitted from the laser diode 51b has not reached the target value, and the flow returns to step S27. Therefore, the signal DA
2 is the same as step S27 until digital data I / O = 0.
Repeat S28.

Next, the laser diodes 51a and 51b
Sets the correction current value when both emit light. First, the target value of the voltage input to the A / D converter 44 when both the laser diodes 51a and 51b emit light is determined. In step S31, the target value APC of the laser diode 51a and the target value APC2 of the laser diode 51b are added to obtain APC0. Since the video signal VD2 is in the ON state, the video signal VD1 is turned on in step S32, the signals DA3 and DA4 are incremented by a predetermined value "L" in step S33, and the value of the signal AD is incremented in step S34. Confirmed,
It is determined whether or not the laser diodes 51a and 51b have reached the target light amount.

That is, if AD ≧ APC0, it is determined that the light emission amounts of the laser diodes 51a and 51b have reached the target value, and the signals DA3 and DA4 are decreased by “K” in step S35. Then, in step S36, the video signals VD1 and VD2 are turned off, and the pre-rotation light amount control for the laser diodes 51a and 51b is terminated. In step S34, the signal AD
If <APC0, it is determined that the amount of light emitted from the laser diodes 51a and 51b has not reached the target value, and step S33 is performed.
Return to Therefore, steps S33 and S34 are repeated until the signal DA2 becomes AD ≧ APC0.

After the end of the pre-rotation light amount control, the main control unit 40 performs an image forming operation based on the set signals DA1, DA2, DA3, and DA4 in accordance with the video signals VD1, VD2.

FIG. 3 is a flowchart of the inter-sheet light amount control. The inter-sheet light amount control is a light amount control performed between recording paper conveyances when performing continuous printing, and the laser light amount, that is, the output of the signals AD1 and AD2. Performs a fine adjustment operation of comparing with the target value. First, the inter-sheet light amount control of the laser diode 51a is performed. In step S40, the video signal VD1 is turned on, and the video signal VD2 is turned off. In step S41, the signal AD is set to the target value APC.
Judge whether it is larger or smaller than Signal AD is the target value AP
If it is larger than C, the signal DA1 is reduced by a predetermined value "K" in step S42, and the signal AD and the target value APC are reduced in step S43.
And if the signal AD is smaller than the target value APC, the inter-sheet light amount control for the laser diode 51a is terminated. If the signal AD is larger than the target value APC in step S43, the process returns to step S42. Therefore, the signal AD has the target value AP
Steps S42 and S43 are repeated while it is larger than C.

On the other hand, in step S41, the signal AD becomes the target value APC
If smaller, the signal DA1 is set to "K" in step S44.
In step S45, the signal AD is compared with the target value APC. Then, Step S43 and Step S45 are repeated until the signal AD becomes larger than the target value APC in Step S45. If the signal AD exceeds the target value APC in step S45, the signal DA1 is decreased by "K" in step S46, the video signal VD1 is turned off in step S47, and the inter-sheet light amount control for the laser diode 51a ends. I do.

Next, the inter-sheet light amount control for the laser diode 51b is performed. In step S48, the video signal VD2 is turned on, and in step S49, it is determined whether the digital data I / O is "0" or "1". When digital data I / O = 0, the light emission amount of the laser diode 51b is equal to the target value APC.
Thus, the signal DA2 is reduced by a predetermined value "K" in step S50. Then, if the digital data I / O = 1 in step S51, the inter-sheet light amount control for the laser diode 51b ends. If digital data I / O = 0 in step S51, the process returns to step S50. Therefore, while digital data I / O = 0, steps S50 and S51 are repeated.

On the other hand, in step S49, the digital data I / O
If = 1, the signal DA2 is incremented by "K" in step S52, and it is determined in step S53 whether or not digital data I / O = 0.
S52 and step S53 are repeated. If digital data I / O = 0 in step S53, it is determined that the light emission amount of the laser diode 51b has reached the target light amount. In step S54, the signal DA1 is reduced by "K", and in step S55 the video signal is reduced. Turns off VD2 and ends the inter-sheet light amount control.

In the inter-sheet light quantity control, the correction current value is not controlled, and the signals DA3 and DA4 of the pre-rotation light quantity control are used at the time of image output. After the inter-sheet light amount control is completed, the main control unit 40 uses the values of the signals DA1 and DA2 set in the inter-sheet light amount control and the signals DA3 and DA4 set in the pre-rotation light amount control to output the video signal V
An image forming operation is performed by D1 and VD2.

FIG. 4 is a flow chart of the second embodiment, in which the inter-sheet light amount control of the laser diode 51b is performed using the amplifier 60 instead of the comparator 61, and the target value of the laser diode 51b is the pre-rotation light amount. During control, the signal AD set in step S29 of FIG. 2 is used as the target value APC2. The other configuration of the control circuit and the flowchart of the pre-rotation light amount control are the same as those of the first embodiment, and therefore, the duplicated description will be omitted.

First, the control is started from the control of the laser diode 51a. Steps S40 to S47 of the inter-sheet light amount control for the laser diode 51a are the same as those in the first embodiment, and the description is omitted. The same steps as those in FIG. 3 use the same step numbers. Next, the laser diode 5
The inter-sheet light amount control for 1b is performed. In step S48, the video signal VD2 is turned on, and in step S60, the signal AD is set to the target value AP.
Determine if it is larger or smaller than C2. Signal AD is the target value
If the signal AD is larger than APC2, the signal DA2 is reduced by a predetermined value "K" in step S50, the signal AD is compared with the target value APC2 again in step S61, and if the signal AD is smaller than the target value APC2, the laser diode 51b Is terminated. If the signal AD is larger than the target value APC2 in step S61, the process returns to step S50. Therefore, while the signal AD is larger than the target value APC2, step S50 and step
Repeat S61.

On the other hand, in step S60, the signal AD is set to the target value APC2.
If it is smaller, the signal DA2 is incremented by "K" in step S52, and the signal AD and the target value APC2 are incremented in step S62.
Compare with Steps S52 and S62 are repeated until the signal AD becomes larger than the target value APC2 in step S62. If the signal AD becomes equal to or larger than the target value APC2 in step S62, the signal DA2 is reduced by "K" in step S54,
In step S55, the video signal VD2 is turned off, and the inter-sheet light amount control ends. After the inter-sheet light amount control is completed, the main control unit 40 uses the values of the signals DA1 and DA2 set in the inter-sheet light amount control and the signals DA3 and DA4 set in the pre-rotation light amount control to output the video signal VD.
1. An image forming operation is performed by VD2.

FIG. 5 is a flowchart of the third embodiment. The control circuit configuration and the pre-rotation light amount control flowchart are the same as those of the first embodiment, and the description of the same parts will not be repeated. In the present embodiment, the control of the inter-sheet light amount of the laser diode 51b is simplified, and the result of the inter-sheet light amount control of the laser diode 51a is used as the laser diode 5b.
The inter-sheet light amount control of 1b is estimated. The same steps as those in FIGS. 3 and 4 use the same step numbers.

First, in step S70, the value of the signal DA1 based on the result of the pre-rotation light amount control is stored as the signal DAa, the video signal VD1 is turned on, the video signal VD2 is turned off in step S40, and the signal AD is set to the target value in step S41. Determine if it is larger or smaller than APC. If the signal AD is larger than the target value APC, the signal DA is reduced by a predetermined value "K" in step S42, and the signal AD is compared with the target value APC2 in step S43. If the signal AD is smaller than the target value APC in step S43, the inter-sheet light amount control for the laser diode 51a ends. If the signal AD is larger than the target value APC in step S43, the process returns to step S42. Therefore, the signal AD becomes the target value
Steps S42 and S43 are repeated while the difference is larger than APC.

On the other hand, in step S41, the signal AD becomes the target value APC
If it is smaller, the signal DA1 is incremented by "K" in step S44, and the signal AD and the target value APC are incremented in step S45.
Compare. Steps S45 and S45 are repeated until the signal AD becomes larger than the target value APC in step S45. If the signal AD has become equal to or larger than the target value APC in step S45, the signal DA1 is decreased by "K" in step S46.

Then, in step S71, the signal DA1 as a result at this time is stored as a signal DAb, and in step S72, a difference between the signals DAa and DAb is obtained. In step S73, this value is given to the signal DA2 set by the previous target value APC. In step S47, the video signal VD1 is turned off, and the inter-sheet light amount control ends. After the inter-sheet light amount control ends, the main control unit 40 performs an image forming operation based on the video signals VD1 and VD2 with the values of the signals DA1 and DA2 set between the sheets and the signals DA3 and DA4 set in the pre-rotation light amount control. .

This embodiment utilizes the fact that the multi-beam laser light source is composed of adjacent semiconductor elements and their characteristics are similar to each other. 5
Although the value for 1b is set, the reverse method may be used, or the laser diodes 51a and 51b may be controlled alternately for only one of the sheets. In this way, the processing can be simplified.

FIG. 6 is a block diagram of an electric circuit according to the fourth embodiment, and the description of the same parts as in the first embodiment will be omitted.
In this embodiment, the drive current sources 57a and 57b of the first embodiment are used.
Is provided with a correction drive current source 70 in place of
As in the embodiment, the multi-beam laser light source is constituted by adjacent semiconductor elements, and utilizes the fact that both have similar characteristics.

The drive current source 70 for correction is
The current value is determined according to the voltage from the / A converter 43a.
Here, the output voltage of the D / A converter 43a is set for the laser diode 51a, and the value is used for the laser diode 51b. In this embodiment,
Since the number of outputs of the D / A converter 43 of the main control unit 40 can be reduced, and light amount control for setting a correction current for the laser diode 51b is not required, the number of light emitting elements is particularly increased to three or more. It is effective when

The driving current source 70 is provided with a D / A converter 43.
The current value set in a can be easily associated with the laser diodes 51a and 51b by the mirror circuit. Here, the value set for the laser diode 51a is used for the laser diode 51b, but the reverse method may be used.

FIG. 7 is a block diagram of an electric circuit according to the fifth embodiment. The laser diode driving circuit 50 is provided with low-pass filters 75a and 75b, The signals PW1 and PW2 are converted into DC voltages and used for setting the correction drive current sources 57a and 57b.

[0048]

As described above, the image forming apparatus according to the present invention changes the drive current in accordance with the on / off state of the adjacent laser diode, so that the amount of light emitted from the laser diode against thermal crosstalk can be reduced. Can be suppressed, so that the variation in the amount of light on the photoreceptor can be reduced, and the quality of the output image can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electric circuit according to a first embodiment.

FIG. 2 is a flowchart of a pre-rotation light amount control.

FIG. 3 is a flowchart of sheet light amount control.

FIG. 4 is a flowchart of a second embodiment.

FIG. 5 is a flowchart of a third embodiment.

FIG. 6 is a configuration diagram of an electric circuit according to a fourth embodiment.

FIG. 7 is a configuration diagram of an electric circuit according to a fifth embodiment.

FIG. 8 is a configuration diagram of a conventional electric circuit.

FIG. 9 is a flowchart of a conventional example at the time of pre-rotation light amount control.

FIG. 10 is a flowchart of a conventional example at the time of inter-sheet light amount control.

FIG. 11 is a plan view of a multi-beam laser scanner device.

FIG. 12 is a configuration diagram of an electric circuit of a laser diode.

FIG. 13 is a configuration diagram of a laser diode.

[Explanation of symbols]

 Reference Signs List 40 Main control unit 50 Laser diode drive circuit 51a, 51b Laser diode 52 Photodiode 54a, 54b, 58a, 58b Switching circuit 56a, 56b, 57a, 57b Drive current source 59, 61 Variable resistor 60 Amplifier 61 Comparator 75a, 75b Low pass filter

Claims (11)

[Claims] In an image forming apparatus using an electrophotographic process for forming an electrostatic latent image on a photoreceptor, at least two light emitting elements having a semiconductor array structure and a light beam from the light emitting elements are detected. A light detecting element, a package integrally storing the light emitting element and the light detecting element, first current setting means for setting a driving current for emitting the light emitting element with a desired light amount; And first switching means for turning on / off the connection between the light-emitting element and the light-emitting element, wherein the first current-setting means and the first switching means have the same number of circuits as the light-emitting element. And an image forming apparatus which operates in a one-to-one correspondence with the light emitting element. 2. The method according to claim 1, wherein the first switching unit turns on / off a connection between the first current setting unit and the light emitting element according to a first digital signal corresponding to the light emitting element on a one-to-one basis. Item 2. The image forming apparatus according to Item 1. 3. The image forming apparatus according to claim 1, wherein the first current setting means sets a current value according to a first analog signal corresponding to the light emitting element on a one-to-one basis. 4. A second current setting means for setting a current value to be added to the first current setting means, and a second switching for turning on / off the current value set by the second current setting means. 2. The circuit according to claim 1, wherein the number of circuits included in the second current setting means and the number of circuits included in the second switching means are equal to the number of the light emitting elements, and operate in one-to-one correspondence with the light emitting elements. The image forming apparatus according to claim 1. 5. The second switching means according to an output from a logic circuit for synthesizing two first digital signals corresponding to the adjacent light emitting elements, the two second light emitting elements corresponding to the respective light emitting elements. 5. The image forming apparatus according to claim 4, wherein the current values set by said current setting means are simultaneously turned on / off. 6. The image forming apparatus according to claim 4, wherein said second current setting means sets a current value according to a second analog signal corresponding to said light emitting element on a one-to-one basis. 7. The image forming apparatus according to claim 4, wherein said second current setting means sets all current values of itself according to a second analog signal corresponding to one predetermined light emitting element. 8. A photoelectric conversion means for converting a photocurrent of the photodetector into a voltage, an amplifier for amplifying a voltage from the photoelectric conversion means corresponding to the predetermined light emitting element, and an amplifier other than the predetermined light emitting element. The image forming apparatus according to claim 7, further comprising a comparator configured to compare a voltage from the photoelectric conversion unit corresponding to the light emitting element with a reference voltage. 9. The light emitting device according to claim 1, wherein the comparator and the reference voltage generating means have a circuit obtained by subtracting one from the number of the light emitting elements, and correspond to light emitting elements other than the predetermined light emitting element on a one-to-one basis. Item 10. The image forming apparatus according to Item 8. 10. The image forming apparatus according to claim 8, wherein said photoelectric conversion means is constituted by a variable resistor and can change a conversion rate. 11. The image forming apparatus according to claim 8, wherein said reference voltage generating means is constituted by a variable resistor and is capable of changing a voltage value.