JPH09260789A - Image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the output variation of a laser, due to self-heating of the laser and thermal interference from other lasers to improve image quality, by setting a laser driving current based on a first quantity control signal and an output signal of integral operation means. SOLUTION: Respective light emitting points of a plurality of laser light sources are modulated independently, by modulation means 1204 and laser drive means 1205. Respective light outputs from the light sources are detected by light quantity detection means 1203. Laser operating currents are individually set by first light quantity control signal setting means 1303, in accordance with a predetermined timing other than the image formation, so that the detected values from the light quantity detection means 1203 for respective lasers are equal to a predetermined reference value. A modulated laser signals are integrated by a plurality of integral operation means, having different time constants and gains. Laser driving currents are set by second light quantity control signal setting means 1401, based on a first light quantity control signal which is the output of the first light quantity control signal setting means 1303 and on the output of one or more integral operation means.

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 such as a printer, a copying machine or a facsimile, which scans a recording medium with a plurality of laser beams to form an image.

[0002]

9 and 10 are block circuit diagrams showing a configuration example of a conventional image forming apparatus. Also, FIG.
6 is a flowchart showing image forming sequence control,
FIG. 12 is a flowchart showing a laser light output adjustment routine. Hereinafter, description will be given with reference to these drawings.

First, a print signal for controlling the start or continuation of printing of the image forming apparatus is connected to the microprocessor 1 from the image controller 2. When the print signal is enabled, the microprocessor 1 recognizes the start of printing or the continuation of printing (S1), and conveys the recording material to a predetermined position in the image forming apparatus by the recording material conveying means (not shown). Wait (S
2).

Next, the microprocessor 1 follows the flowchart showing the laser light output adjustment shown in FIG.
The light output of the laser is adjusted (S3).

Here, as shown in FIG. 13, the image forming apparatus includes a semiconductor laser diode array 1201 having four laser emission points arranged in a line, and a photodiode 1202 for detecting the laser light output. The light source unit 12 configured by is used. It should be noted that the laser emission points of such a semiconductor laser diode array 1201 are LD1, LD in the order in which they are arranged in a line.
2, LD3, LD4.

In FIG. 12, the microprocessor 1
Sets a variable M for identifying the laser of the semiconductor laser diode array 1201 to 1 and selects LD (M), that is, LD1 (S301).

Next, the microprocessor 1 determines the laser L
The initial setting value of the light intensity control signal of D1 is output (S30
2), the buffer latch circuit 30 by the selector 300
Only 1 is enabled (S303). The light quantity control signal of the laser LD1 is supplied to the buffer latch circuit 301.
And the laser drive circuit 11 via the D / A converter 401.
01 is input to the constant current circuit. This constant current circuit supplies a laser operating current proportional to the input light amount control signal, and ON / OFF control is performed by a switching circuit arranged in the laser drive circuit 1101.

Then, the microprocessor 1 outputs data for forcibly lighting only the laser LD1 to the LD forcible lighting selector 8, and the output of the LD forcible lighting selector 8 passes through the logical sum 1001 and the laser drive circuit 1101.
(S304). The laser driving circuit 1101 which has received the laser forced lighting signal,
The laser LD1 is continuously turned on, and the D / A converter 401
A laser operating current proportional to the output light quantity control signal is supplied to the laser LD1.

The light output of the laser LD1 is detected by a photodiode 1202, and the LD light amount detection circuit 120 is detected.
The current-voltage conversion and amplification are performed at 3, and the result is input to the microprocessor 1 through the A / D converter 1204.

The microprocessor 1 which has detected the light output of the laser LD1 calculates the output light amount error E (= Pref-P) between the light output reference value Pref and the detected light amount value P (S305).

The detected light amount value P of the LD 1 is the light output reference value Pr.
If the value is smaller than ef, the optical output light amount error E
Is a positive value (S306 → S307). At this time, if the detected light quantity value P does not reach 90% of the light output reference value Pref, the light quantity detection error E is larger than the value of Pref / 10 (S307 → S308), so that the LD1 light quantity control signal has a large I1. And the optical output of the laser LD1 is increased. This sequence is repeated until the detected light amount value P reaches 90% or more of the light output reference value Pref.

Then, when the increased detected light amount value falls within the range of 90% or more and less than 95% of the light output reference value Pref, the output light amount error E becomes Pref / 20 <E ≦ Pre.
It becomes f / 10 (S307 → S309), and the magnitude of I2 is increased in the light amount control signal (S309).

The value of I2 is smaller than the value of I1 to improve the resolution of the light amount control signal. In this sequence, the detected light amount value P is 9 of the light output reference value Pref.
It is repeated until it reaches 5% or more. Further, when the increased detected light amount value P is in a range of 95% or more of the light output reference value Pref and smaller than the light output reference value Pref, the output light amount error E becomes E ≦ Pref / 20 (S307 →
S310), the magnitude of I3 is increased in the light quantity control signal (S310).

The value of I3 is smaller than the value of I2 to improve the resolution of the light quantity control signal. This sequence is repeated until the detected light amount value P becomes equal to or higher than the light output reference value Pref, and when the increased detected light amount value P reaches the light output reference value Pref, E = 0 (S30
6 → S314), the light amount control signal at that time is latched by the buffer latch circuit 301 (S314), and the light amount control signal output from the D / A converter 401 holds a constant value.

Therefore, since the laser LD1 can obtain a desired light output in the thermal equilibrium state, data for canceling the laser forced lighting is output to the LD forced lighting selector 8.
The laser LD1 is turned off (S315).

Further, due to variations and deterioration of laser characteristics, the resolution of I1 and I2 is insufficient, and the laser LD
When the detected light amount value P of the light output of 1 becomes larger than the light output reference value Pref, the output light amount error E becomes a negative value (E <0) (S306 → S311).

At this time, the magnitude of I3 in the light quantity control signal is reduced (S311) to reduce the laser light output. This sequence is repeated until the detected light amount value P is less than or equal to the light output reference value Pref, that is, the output light amount error E becomes E ≧ 0 (S311, S312, S313), and the output light amount error E
When E becomes E ≧ 0, the light quantity control signal value is latched by the buffer latch circuit 301 (S314), and the LD1 light quantity control signal output from the D / A converter 401 holds a constant value.

Therefore, since the laser LD1 has obtained the desired light output in the thermal equilibrium state, the data for canceling the laser forced lighting is output to the LD forced lighting selector 8.
The laser LD1 is turned off (S315).

After the light output adjustment of the laser LD1 is completed, the variable M is not 4 (= the number of laser emission points) (S316 → S317), so the value of the variable M is incremented (S317).

Then, the microprocessor 1 performs the same optical output adjustment as that of the above-described LD1 for the laser LD2 corresponding to the variable M (= 2) (S302 to S31).
6) When the light amount control signal of LD2 is determined, the variable M (=
Since the value of 2) is not 4 (S316S → S317), the value of the variable M is incremented (S317).

The microprocessor 1 then proceeds to the variable M (=
For the laser LD3 corresponding to 3), the same optical output adjustment as that of the above-described LD1 is performed (S302 to S316), and the LD
When the light amount control signal of 3 is determined, the value of the variable M (= 3) is not 4 (S316 → S317), so the value of the variable M is incremented (S317).

The microprocessor 1 uses the variable M (= 4)
The same light output adjustment as that of the above-described LD1 is performed for the laser LD4 corresponding to (S302 to S316), and when the light amount control signal of the LD4 is determined, the value of the variable M (= 4) is 4, so It is determined that the light output adjustment has been completed for all the lasers of the semiconductor laser diode array provided, and the process proceeds to the next sequence.

The microprocessor 1 judges that the preparation for image formation is completed, and outputs a vertical synchronization signal requesting the transmission of the vertical synchronization signal for the sub scanning period of the recording material to the image controller 2 (S4).

The image controller 2 that receives the vertical synchronization request outputs a vertical synchronization signal to the microprocessor 1 and receives the vertical synchronization signal.
Performs the image forming operation on the recording material (S5 → S)
6).

The optical system will be described below with reference to FIG.

Laser emission point LD1 of the light source unit 12,
Central light rays L1, L2, L3, L4 parallel to the optical axis of the condenser lens 1501 are emitted from LD2, LD3, LD4.

These central rays are collected by a condenser lens 1501.
After passing through the focal point f of the cylindrical lens 1502 and reaching the deflecting mirror surface of the rotary polygon mirror 1503. Each light beam reflected by the deflecting mirror surface of the rotating polygon mirror 1503 is a spherical lens 1504 or a toric lens 15.
An anamorphic scanning lens system constituted by 05 forms an image on the surface of the recording medium 16 to form an image.

Further, a reflection mirror 1506 is arranged at the tip of the scanning line, and the light beam is detected by the beam detector 13.
Leading to 01. The beam detector 1301 includes a light receiving element 1301A, a slit plate 1301B for individually detecting a plurality of lasers, and the light receiving element 1301A (not shown).
The optical output detection signal of each laser beam passing through the tip of the scanning line is input to the comparator 1302.

The comparator 1302 converts the analog signal into a pulse signal, the timing signal forming circuit 1303 separates the timing of the pulse signal for each laser, and the horizontal synchronizing signal BT for each laser.
1, BT2, BT3, BT4 are obtained.

The horizontal synchronizing signals BT1, BT2, BT3, BT output from the timing signal forming circuit 1303 are output.
4 is each line buffer 501, 502, 503, 50
Output to 4. The line buffers 501 to 504 are
The recording information corresponding to each main scanning line is transferred from the image controller 2 which holds dot matrix information for forming an image on the recording medium, which corresponds to the timing of the horizontal synchronizing signal and Image data for one scan is output in synchronization with the image clock from the controller 2.

The image data output from the line buffers 501 to 504 is the laser data LD1, LD2, LD.
3, a laser modulation signal for modulating the LD 4, and a laser drive circuit 1101 via each logical sum 1001 to 1104.
˜1104 to the switching circuit. And
Lasers LD1 and LD arranged in the light source unit 12
2, LD3, LD4 are modulated and driven, and modulated beams L1, L
2, L3, and L4 are emitted.

When the image formation on the recording material is completed in this way, the microprocessor 1 repeats the above sequence control in order to continuously form the image on the recording material of the next page if the print signal is enabled. Perform (S7).
If the print signal is disabled, the image forming apparatus shifts to the standby state (S8) and waits for the next print signal to be enabled (S1).

[0033]

As described above,
As a means for uniformly maintaining the light output of a plurality of lasers arranged in the light source unit, a plurality of laser operating currents are individually set every time one page image is formed, and the values are held, Keeps the light output of all lasers uniform.

However, when the laser is modulated with the laser operating current Iop by the conventional laser light output adjustment, as shown in FIG.
As shown in FIG. 5, the temperature of the laser oscillation region fluctuates with the laser modulation, so that the optical output of the laser fluctuates. Further, as shown in FIG. 16, when the light emitting points are close to each other due to the arrangement of the laser diode arrays, thermal interference affects the temperature of the laser oscillation region due to the modulation operation of another laser. Light output fluctuates.

Therefore, when the laser light output fluctuates, the recorded image density fluctuates and density unevenness occurs, and gradation reproduction characteristics with linearity cannot be obtained, and there is a problem that image quality is significantly deteriorated.

Therefore, an object of the present invention is to provide an image forming apparatus of high image quality, which suppresses laser light output fluctuation caused by self-heating of a laser and thermal interference of other lasers.

[0037]

According to a first aspect of the present invention, in an image forming apparatus for irradiating a photosensitive member with a plurality of lasers to form an electrostatic latent image, light emitting points of the plurality of laser light emitting sources are provided. A plurality of laser modulation means and laser driving means for respectively independently modulating, a light amount detecting means for detecting the light output of each light emitting source, and detection of the light amount detecting means for each laser at a predetermined timing other than image formation. First light amount control signal setting means for individually setting the laser operating current so that the value becomes equal to a predetermined reference value, and a plurality of integration calculation means having different time constants and gains for integrating the laser modulation signal A second light quantity control signal setting means for setting a laser drive current based on a first light quantity control signal which is an output of the first light quantity control signal setting means and an output signal of one or more integral calculation means. Characterized in that it.

A second invention of the present application is characterized in that, in the above-mentioned first invention, there is provided means for resetting the integral calculation means during operation of the first light amount control signal setting means.

The third invention of the present application is based on the above first and second inventions.
In the present invention, adding means for adding the outputs of the first light amount control signal and one or more integral calculating means, a constant current circuit for controlling the laser operating current in proportion to the output of the adding means, and switching And a laser driving unit including a circuit.

The fourth invention of the present application is the above first and second inventions.
In the present invention, there is provided a laser driving means including a plurality of constant current circuits and a switching circuit for controlling the laser operating current in proportion to the first light amount control signal and the output of the integration calculating means. And

The fifth invention of the present application is based on the above first and second inventions.
In the present invention, a constant current circuit and a switching circuit for controlling the laser operating current proportional to the first light amount control signal, and one or more constant current circuits for controlling the laser bias current in proportion to the output of the integral calculating means. And a laser driving means configured to include.

The sixth invention of the present application is the above-mentioned first to fifth inventions.
In the present invention, the control means for pulsing the semiconductor laser during the setting of the first light amount control signal is provided.

In the above structure, the first light quantity control signal setting means adjusts the laser light output to compensate for the ambient temperature of the image forming apparatus and the variation of the laser, and each integrating means is
An integrator such as a low-pass filter having a first-order delay type transfer function, which estimates the temperature fluctuation due to self-heating of the cavity temperature and the temperature fluctuation due to thermal interference between laser elements based on the laser modulation signal and thermal resistance model. The light output correction signal is generated.

At this time, each integrator is set to the initial setting value by the means for resetting the integrating means during the operation of the first light amount control signal setting means. Further, during the operation of the first light quantity control signal setting means, the means for driving the laser by a single pulse adjusts the laser light output while suppressing the temperature fluctuation due to the lighting of the laser to the minimum. Further, during the operation of the first light amount control signal setting means, the means for continuously turning on the laser adjusts the laser light output in the thermal equilibrium state of the laser.

By the second light quantity control signal setting means, the light output of each laser can be constantly adjusted during image formation.

[0046]

1 and 2 are block circuit diagrams showing a configuration of an image forming apparatus in a first embodiment of the present invention, and FIG. 3 is a laser beam in the first embodiment. It is a flow chart which shows an output adjustment routine.
In these figures, the elements common to the conventional example are designated by the same reference numerals.

First, a print signal for controlling the start or continuation of printing of the image forming apparatus is connected to the microprocessor 1 from the image controller 2. Then, when the print signal is enabled, the microprocessor 1 recognizes the start of printing or the continuation of printing (S1), the recording material conveying means conveys the recording material to a predetermined position in the image forming apparatus, and waits. Yes (S2).

Next, the microprocessor 1 adjusts the light output of the laser according to the flowchart showing the laser light output adjustment shown in FIG. 16 (S3).

Here, as shown in FIG. 13, the image forming apparatus includes a semiconductor laser diode array 1201 having four laser emission points arranged in a line, and a photodiode 1202 for detecting the laser light output. The light source unit 12 is used. It should be noted that the laser emission points of such a semiconductor laser diode array 1201 are arranged in a row in the order of LD1, LD2,
Referred to as LD3 and LD4.

The microprocessor 1 resets all the integrators that perform the integral calculation of the laser modulation signal and sets them to their respective initial setting values (S321).

Further, the microprocessor 1 uses the variable M for identifying the laser of the semiconductor laser diode array.
Is set to 1 and LD (M), that is, LD1 is selected (S322).

Further, the microprocessor 1 outputs the initial setting value of the light quantity control signal of the laser LD1 (S32).
3), the selector 300 allows the buffer latch circuit 30
Only 1 is enabled (S324). The light quantity control signal of the laser LD1 is supplied to the buffer latch circuit 301.
And to the adder 901 via the D / A converter 401.

The adder 901 includes integrators 611 and 62.
The output of No. 1 and the first light amount control signal are added, and the result is input to the constant current circuit provided in the laser drive circuit 1101. Now, since all the integrators are in the reset state, each integrator outputs a constant initial setting value. Therefore, the adder 901 outputs an inverted signal obtained by adding the light amount control signal of the LD1 and the initial setting values of the integrators 611 and 612, and the constant current circuit of the laser drive circuit 1101 proportionally outputs the output signal of the adder 901. The laser operating current is supplied. That is, the laser operating current has decreased the predetermined value set by the integrator with respect to the first light amount control signal.

Next, in the microprocessor 1, the selector 1402 causes the 3-state buffer 1411 for the LD 1 to be used.
Output a signal for enabling (S325),
A trigger signal for outputting a pulse signal is output to the pulse generation circuit 1401 (S326).

Upon receiving the trigger signal from the microprocessor 1, the pulse generation circuit 1401 outputs a pulse signal for driving the laser in a single pulse. The pulse signal output from the pulse generation circuit 1401 is input to the buffers 1411 to 1414, and is input to the switching circuit provided in the laser driving circuit 1101 through the logical sum 1001 and the buffer 1411 which is currently enabled. To do. Upon receiving the pulse signal, the laser driving circuit 1101 causes the laser LD1 to pulse-light with a laser operating current proportional to the output signal of the adder 901.

The light output of the laser LD1 is detected by a photodiode 1202 provided in the light source unit 12, current-voltage converted and amplified by an LD light amount detection circuit 1203, and digitally output via an A / D converter 1204. It is converted into a signal and input to the latch circuit 1205.

At this time, the latch trigger signal of the latch circuit 1205 latches the data for a predetermined time after the laser LD1 is turned on by the delay circuit 1403 for the trigger signal for pulse driving the LD1. And
The latch data of the latch circuit 1205 is input to the microprocessor 1 to obtain the detected light amount value P.

Having detected the light output of the laser LD1, the microprocessor 1 calculates the output light amount error E (Pref-P) between the light output reference value Pref and the detected light amount value P (S327).

The detected light amount value P of LD1 is the light output reference value Pr.
If the value is smaller than ef, the optical output light amount error E
Is a positive value (S328 → S329). At this time, if the detected light amount value P does not reach 90% of the light output reference value Pref, the light amount detection error E is larger than the value of Pref / 10 (S329 → S330), so that the light amount control signal of LD1 is set to I1. The size is decreased and the light output of the laser LD1 is increased (here, when the first light amount control signal is decreased, the laser light output is increased because of the inverting adder 9).
This is because 01 is used). This sequence is repeated until the detected light amount value P reaches 90% or more of the light output reference value Pref.

When the increased detected light amount value P is in the range of 90% or more and less than 95% of the light output reference value Pref, the output error E becomes Pref / 20 <E≤Pref.
/ 10 (S329 → S331), and the magnitude of I2 in the light amount control signal is reduced (S331). The I2 is
By taking a value smaller than I1, the resolution of the light quantity control signal is improved. This sequence is repeated until the detected light amount value P becomes equal to or higher than the light output reference value Pref, and when the increased detected light amount value P reaches the light output reference value Pref, E
Becomes 0 (S328 → S336), and the light intensity control signal at that time is latched by the buffer latch circuit 301 (S33).
6), the light amount control signal output from the D / A converter 401 holds a constant value. Therefore, the laser LD1
The optical output of the LD1 can be obtained with the influence of self-heating suppressed to a minimum.

Further, due to the variation and deterioration of the laser characteristics, the resolution of I1 and I2 is insufficient, and the laser LD
When the detected light amount value P of the light output of 1 becomes larger than the light output reference value Pref, the output light amount error E is a negative value (E
<0) is obtained (S328 → S333). At this time, the magnitude of I3 is increased in the light quantity control signal (S323), and the laser light output is decreased.

In this sequence, the detected light amount value P is less than or equal to the light output reference value Pref, that is, the output light amount error E is E ≧ 0.
Repeatedly until (S333, S334, S33
5) When the output light quantity error becomes E ≧ 0, the light quantity control signal value is latched by the buffer latch circuit 301 (S335).
→ S336), L output from the D / A converter 401
The D1 light amount control signal holds a constant value. Therefore, the laser LD1 can obtain the optical output of the laser LD1 while suppressing the influence of self-heating to the minimum.

After the light output adjustment of the laser LD1 is completed, the variable M is not 4 (= the number of laser emission points) (S337 → S338), and the value of the variable M is incremented (S338).

Then, the microprocessor 1 performs the same optical output adjustment as that of the above-mentioned LD1 for the laser LD2 corresponding to the variable M (= 2) (S323 to S33).
6) When the light amount control signal of LD2 is determined, the variable <(=
Since the value of 2) is not 4 (S337 → S338), the value of the variable M is incremented (S338).

The microprocessor 1 then proceeds to the variable M (=
Regarding the laser LD3 corresponding to 3), the above-mentioned LD1
Adjust the light output in the same manner as (S323 to S336), and
When the light amount control signal of D3 is confirmed, the value of the variable M (= 3) is not 4 (S337 → S338), so the value of the variable M is incremented (S338).

The microprocessor 1 then proceeds to the variable M (=
Regarding the laser LD4 corresponding to 4), the above-mentioned LD1
Adjust the light output in the same manner as (S323 to S316), and
When the light amount control signal of D4 is determined, the value of the variable M (= 4) is 4 (S337 → S339), so reset of all the integrators is released (S339) and the setting of the first light amount control signal is performed. finish.

When the setting of the first light amount control signal in each laser is completed, the microprocessor 1 judges that the preparation for image formation is completed, and the microprocessor 1 determines the vertical synchronization signal for synchronizing the recording material in the sub-scanning direction. The vertical synchronizing signal for requesting the transmission of is output (S4).

The image controller 2 which receives this vertical synchronization request outputs a vertical synchronization signal to the microprocessor 1 and receives the vertical synchronization signal.
Performs the image forming operation on the recording material (S5 → S)
6).

The beam detector 1301 is the light source unit 1
2 detects the optical output of each laser beam when a plurality of laser beams emitted from the laser beam pass through the end of the operation line for operating the recording medium, and inputs the detection signal to the comparator 1302 to pulse the analog signal. Convert to signal. A timing signal forming circuit 1303 separates the timing of the pulse signal of each pulse signal from each laser, and horizontal synchronization signals BT1, BT2, BT3, and BT4 of each laser are separated.
Get.

The horizontal synchronizing signals BT1, BT2, BT3, BT output from the timing signal forming circuit 1303 are output.
4 is each line buffer 501, 502, 503, 50
Output to 4. The line buffers 501 to 504 are
The recording information corresponding to each main scanning line is transferred by the image controller 2 which holds the dot matrix information for forming an image on the recording medium, and corresponds to the timing of the horizontal synchronizing signals BT1 to BT4. Further, in synchronization with the image clock from the image controller 2, the image data for one scan is output.

The image data output from the line buffers 501 to 504 is the laser data LD1, LD2, LD.
3, a laser modulation signal for modulating the LD4, and a laser drive circuit 1101 through each logical sum 1001 to 1004.
˜1104 to the switching circuit. And
Lasers LD1 and LD arranged in the light source unit 12
2, LD3, LD4 are modulated and driven to form an electrostatic latent image on the recording medium.

The line buffers 501 to 504 are also provided.
The laser modulation signal output from each is connected to an integrator having a predetermined time constant and gain.

The integrators 611, 622, 633, 64
Reference numeral 4 denotes an inversion type integrator (LPF) that integrates the laser modulation signals of the lasers LD1, LD2, LD3, and LD4 to estimate the temperature change due to self-heating of each laser and generates a laser light amount control signal. is there. The integrator 621 is an inversion type integrator (LPF) that estimates the thermal interference of the laser LD1 due to the thermal interference of the modulation driving of the laser LD2 and generates the light amount control signal of the laser LD1.

The integrator 612 estimates the thermal interference of the laser LD2 due to the thermal interference of the modulation driving of the laser LD1 and generates the light quantity control signal of the laser LD2.
F). The integrator 632 estimates the thermal interference of the laser LD2 due to the thermal interference of the modulation drive of the laser LD3, and generates the light amount control signal of the laser LD2.
F).

The integrator 623 estimates the thermal interference of the laser LD3 due to the thermal interference of the modulation driving of the laser LD2, and generates the light quantity control signal of the laser LD3.
F). The integrator 643 estimates the thermal interference of the laser LD3 due to the thermal interference of the modulation driving of the laser LD4 and generates a light amount control signal of the laser LD3.
F).

The integrator 634 estimates the thermal interference of the laser LD4 due to the thermal interference of the modulation driving of the laser LD4, and generates the light quantity control signal of the laser LD4.
F).

The integrator may be a cascade connection of integrators or filters having respective first-order delay transfer functions. That is, the integrator infers the fluctuation of the cavity temperature due to the self-heating and the thermal interference caused by the laser modulation signal, and generates the light amount control signal for correcting the fluctuation of the laser light output. Further, the influence of thermal interference in this embodiment is described by considering only the influence from the adjacent laser.

Next, the laser drive current of the laser LD1 will be described.

The first light quantity control signal output from the D / A converter 401, the light quantity control signal of the integrator 611 for inferring the temperature fluctuation due to self-heating associated with the modulation signal of the laser LD1, and the modulation signal of the laser LD2 are used. Laser LD2 with
Inversion type adder 9 for performing addition operation with the light amount control signal of the integrator 621 which infers the temperature fluctuation due to the thermal interference from
Enter 01.

The output of the adder 901 is input to a constant current circuit provided in the laser drive circuit 1101 and is controlled to a laser operating current proportional to the output signal of the inverting adder 901, and the LD1 laser modulation signal is output. Pulse driving is performed by a switching circuit that is ON / OFF controlled by.
Therefore, the integrators 611 and 621 are generated according to the laser modulation signal.
Output is reduced from the initial output value, and as a result, the laser operating current increases, laser light output fluctuation correction is performed, and uniform laser light output is obtained.

Next, the laser drive current of the laser LD2 will be described.

The first light quantity control signal output from the D / A converter 402, the light quantity control signal of the integrator 622 which infers the temperature fluctuation due to self-heating associated with the modulation signal of the laser LD2, and the modulation signal of the laser LD1. Laser LD1 accompanying
Light control signal of the integrator 612 that infers the temperature variation due to thermal interference from the laser LD3, and integrator 6 that infers the temperature variation due to thermal interference from the laser LD3 accompanying the modulation signal of the laser LD3.
The light amount control signal of 32 is input to the inverting adder 902 for performing addition operation.

The output of the adder 902 is input to the constant current circuit provided in the laser drive circuit 1102, controlled to a laser operating current proportional to the output signal of the inverting adder 902, and the LD2 laser modulation signal is output. Pulse driving is performed by a switching circuit that is ON / OFF controlled by.
Therefore, the integrators 622 and 61 are responsive to the laser modulation signal.
The output of 2,632 is reduced from the initial output value, and as a result, the laser operating current is increased, laser light output fluctuation correction is performed, and uniform laser light output is obtained.

Next, the laser drive current of the laser LD3 will be described.

The first light quantity control signal output from the D / A converter 403, the light quantity control signal of the integrator 633 which infers the temperature fluctuation due to self-heating accompanying the modulation signal of the laser LD3, and the modulation signal of the laser LD2 are used. Laser LD2 with
Light amount control signal of the integrator 623 for inferring temperature variation due to thermal interference from the laser LD4 and integrator 6 for inferring temperature variation due to thermal interference from the laser LD4 accompanying the modulation signal of the laser LD4.
The light amount control signal of 43 is input to the inverting adder 903 for performing addition calculation.

Pulse driving is performed by a switching circuit that is controlled to a laser operating current proportional to the output signal of the adder 903 and is ON / OFF controlled by the LD3 laser modulation signal. Therefore, the outputs of the integrators 633, 623, and 643 are reduced from the initial output value in accordance with the laser modulation signal, and as a result, the laser operating current is increased, and the laser light output fluctuation correction is performed and uniform output is performed. A laser light output is obtained.

Next, the laser drive current of the laser LD4 will be described.

Along with the first light quantity control signal output from the D / A converter 404 and the modulation signal of the laser LD4, the light quantity control signal of the integrator 644 for deducing the temperature variation due to self-heating accompanying the modulation signal of the laser LD4 and the modulation signal of the laser LD3 are involved. The light amount control signal of the integrator 634 for inferring the temperature fluctuation due to the thermal interference from the laser LD3 and the inverting adder 9 for performing addition operation.
Enter in 04.

The output of the adder 904 is input to the constant current circuit provided in the laser drive circuit 1104, controlled to a laser operating current proportional to the output signal of the inverting adder 904, and the LD4 laser modulation signal is output. Pulse driving is performed by a switching circuit that is ON / OFF controlled by.
Therefore, the integrators 644 and 634 are provided according to the laser modulation signal.
Output is reduced from the initial output value, and as a result, the laser operating current increases, laser light output fluctuation correction is performed, and uniform laser light output is obtained.

When the image formation on the recording material is completed in this way, the microprocessor 1 repeats the above sequence control in order to continuously form the image on the recording material of the next page if the print signal is enabled. Perform (S7).
If the print signal is disabled, the image forming apparatus shifts to the standby state (S8) and waits for the next print signal to be enabled (S1).

As described above, in the semiconductor laser diode array having a plurality of laser emission points, it is possible to control the light quantity so that a uniform laser light output can always be obtained.

Next, a second embodiment of the present invention will be described.

FIGS. 4 and 5 are block circuit diagrams showing the structure of the image forming apparatus according to the second embodiment, and FIG.
6 is a flowchart showing laser light output adjustment in this second embodiment. The same elements as those of the first embodiment are designated by the same reference numerals, and the description of the same contents will be omitted and only different points will be described.

The microprocessor 1 includes the lasers LD1 to LD1.
When the first light amount control signal of the LD 4 is set, in the first embodiment, the laser operating current is controlled via the inverting adder, so the laser light output is reduced by decreasing the first light amount control signal. Was increasing. However, in the present embodiment, the laser operating current is increased by increasing the first light amount control signal by directly controlling the laser operating current without using the inverting adder. Also, by resetting each integrator, the output of each integrator becomes zero.

The laser modulation signals output from the line buffers 501 to 504 are respectively connected to integrators having a predetermined time constant and gain.

The integrators 711, 722, 733, 74
Reference numeral 4 denotes an integrator (LPF) that integrates the laser modulation signals of the lasers LD1, LD2, LD3, and LD4 to estimate a temperature change due to self-heating of each laser and generate a laser light amount control signal. The integrator 721 is a laser LD
2 is an integrator (LPF) that estimates the thermal interference of the laser LD1 due to the thermal interference of the modulation drive of No. 2 and generates the light amount control signal of the laser LD1. The integrator 712 estimates the thermal interference of the laser LD2 due to the thermal interference of the modulation driving of the laser LD1,
An integrator (LP for generating a light amount control signal for the laser LD2)
F).

The integrator 732 is an integrator (LPF) that estimates the thermal interference of the laser LD2 due to the thermal interference of the modulation driving of the laser LD3 and generates the light amount control signal of the laser LD2. The integrator 723 is an integrator (LPF) that estimates the thermal interference of the laser LD3 due to the thermal interference of the modulation driving of the laser LD2 and generates the light amount control signal of the laser LD3. The integrator 743 has an L value due to thermal interference of modulation driving of the laser LD4.
It is an integrator (LPF) that estimates the thermal interference of D3 and generates a light amount control signal of the laser LD3. The integrator 734 is an integrator (LPF) that estimates the thermal interference of the laser LD4 due to the thermal interference of the modulation driving of the laser LD3 and generates the light amount control signal of the laser LD4.

The integrator may be a cascade connection of integrators or filters having respective first-order delay transfer functions. That is, the integrator infers the fluctuation of the cavity temperature due to the self-heating and the thermal interference caused by the laser modulation signal, and generates the light amount control signal for correcting the fluctuation of the laser light output. Further, the influence of thermal interference in this embodiment is described by considering only the influence from the adjacent laser.

Next, the laser drive current of the laser LD1 will be described.

The first light quantity control signal output from the D / A converter 401, the light quantity control signal of the integrator 711 for inferring the temperature fluctuation due to self-heating associated with the modulation signal of the laser LD1, and the modulation signal of the laser LD2 are used. Laser LD2 with
The light amount control signal of the integrator 721 that infers the temperature fluctuation due to the thermal interference from the laser is input to each of the plurality of constant current circuits provided in the laser drive circuit 1111, and the laser operating current proportional to each light amount control signal is input. Pulse driving is performed by a switching circuit which is controlled to ON and OFF by the LD1 laser modulation signal. Therefore, the outputs of the integrators 711 and 721 increase according to the laser modulation signal, and as a result, the laser operating current increases, the laser light output fluctuation correction is performed, and a uniform laser light output is obtained.

Next, the laser drive current of the laser LD2 will be described.

The first light quantity control signal output from the D / A converter 402, the light quantity control signal of the integrator 722 for deducing the temperature fluctuation due to self-heating accompanying the modulation signal of the laser LD2, and the modulation signal of the laser LD1 are used. Laser LD1 accompanying
Light amount control signal of the integrator 712 for inferring temperature fluctuation due to thermal interference from the laser LD3 and LD3 accompanying the modulation signal of the laser LD3.
The light amount control signal of the integrator 732 that infers the temperature fluctuation due to the heat interference from the laser is input to each of the plurality of constant current circuits provided in the laser drive circuit 1112, and the laser operation proportional to each light amount control signal is input. LD2 controlled by current
Pulse driving is performed by a switching circuit that is ON / OFF controlled by a laser modulation signal. Therefore, the outputs of the integrators 722, 712, and 732 increase according to the laser modulation signal, and as a result, the laser operating current increases, the laser light output fluctuation correction is performed, and a uniform laser light output is obtained. To be

Next, the laser drive current of the laser LD3 will be described.

The first light amount control signal output from the D / A converter 403, the light amount control signal of the integrator 733 for inferring the temperature fluctuation due to self-heating associated with the modulation signal of the laser LD3, and the modulation signal of the laser LD2 are used. Laser LD2 with
Light amount control signal of the integrator 723 for inferring temperature fluctuation due to thermal interference from the laser LD4 and LD4 accompanying the modulation signal of the laser LD4.
The light amount control signal of the integrator 743 which infers the temperature fluctuation due to the heat interference from the laser is input to each of the constant current circuits provided in the laser drive circuit 1113, and the laser operation proportional to each light amount control signal is input. LD3 controlled by current
Pulse driving is performed by a switching circuit that is ON / OFF controlled by a laser modulation signal. Therefore, the outputs of the integrators 733, 723, and 743 increase according to the laser modulation signal, and as a result, the laser operating current increases, the laser light output fluctuation correction is performed, and a uniform laser light output is obtained. .

Next, the laser drive current of the laser LD4 will be described.

The first light quantity control signal output from the D / A converter 404, the light quantity control signal of the integrator 744 for deducing the temperature fluctuation due to self-heating accompanying the modulation signal of the laser LD4, and the modulation signal of the laser LD3 are used. Laser LD3 with
The light amount control signal of the integrator 734 for inferring the temperature variation due to the heat interference from the laser is input to each of the plurality of constant current circuits arranged in the laser driving circuit 1114, and the laser operation proportional to each light amount control signal is input. LD4 controlled by current
Pulse driving is performed by a switching circuit that is ON / OFF controlled by a laser modulation signal.

Therefore, the integrator 7 responds to the laser modulation signal.
The outputs of 44 and 734 increase, and as a result, the laser operating current increases, laser light output fluctuation correction is performed, and uniform laser light output is obtained.

As described above, according to the second embodiment, in the semiconductor laser diode array having a plurality of laser emission points, it is possible to control the light quantity so that a uniform laser light output can always be obtained.

Next, a third embodiment of the present invention will be described.

FIG. 7 and FIG. 8 are block circuit diagrams showing the structure of the image forming apparatus in the third embodiment of the present invention. It should be noted that elements common to the first and second embodiments are denoted by the same reference numerals, the same contents are not described, and different points will be described below.

Next, the laser drive current of the laser LD1 will be described.

The first light quantity control signal output from the D / A converter 401, the light quantity control signal of the integrator 711 which infers the temperature fluctuation due to self-heating associated with the modulation signal of the laser LD1, and the modulation signal of the laser LD2 are used. Laser LD2 with
The light amount control signal of the integrator 721 that infers the temperature variation due to the heat interference from the input signal is input to each of the plurality of constant current circuits provided in the laser drive circuit 1111.

At this time, a laser bias current proportional to the light amount control signals of the integrators 711 and 721 is supplied, and L
The laser operating current proportional to the first light amount control signal of the LD1 is pulse-driven by the switching circuit which is ON / OFF controlled by the D1 laser modulation signal. Therefore,
The outputs of the integrators 711 and 721 increase according to the laser modulation signal, and as a result, the laser bias current increases, the laser light output fluctuation correction is performed, and a uniform laser light output is obtained.

Next, the laser drive current of the laser LD2 will be described.

The first light amount control signal output from the D / A converter 402, the light amount control signal of the integrator 722 for inferring the temperature fluctuation due to self-heating accompanying the modulation signal of the laser LD2, and the modulation signal of the laser LD1 are used. Laser LD1 accompanying
Light amount control signal of the integrator 712 that infers the temperature fluctuation due to thermal interference from the laser LD3, and integrator 7 that infers the temperature fluctuation due to thermal interference from the laser LD3 accompanying the modulation signal of the laser LD3.
The 32 light amount control signals are input to each of the plurality of constant current circuits provided in the laser drive circuit 1112.

At this time, each integrator 722, 712, 73
A laser bias current proportional to the light quantity control signal of 2 is supplied, and a laser operating current proportional to the first light quantity control signal of LD2 performs pulse driving by a switching circuit which is ON / OFF controlled by a laser modulation signal of LD2. . Therefore, the integrators 722, 7 are responsive to the laser modulation signal.
The outputs of 12 and 732 increase, and as a result, the laser bias current increases, so that the laser light output fluctuation correction is performed and a uniform laser light output is obtained.

Next, the laser drive current of the laser LD3 will be described.

The first light quantity control signal output from the D / A converter 403, the light quantity control signal of the integrator 733 for inferring the temperature fluctuation due to self-heating associated with the modulation signal of the laser LD3, and the modulation signal of the laser LD2 are used. Laser LD2 with
Light control signal of the integrator 723 for inferring temperature fluctuation due to thermal interference from the laser LD4 and integrator 7 for inferring temperature fluctuation due to thermal interference from the laser LD4 accompanying the modulation signal of the laser LD4.
The light intensity control signal 43 is input to each of the plurality of constant current circuits provided in the laser drive circuit 1113.

At this time, each integrator 733, 723, 74
A laser bias current proportional to the light quantity control signal of No. 3 is supplied, and a laser operating current proportional to the first light quantity control signal of LD3 is pulse-driven by a switching circuit that is ON / OFF controlled by the LD3 laser modulation signal.
Therefore, the integrators 733 and 72 depending on the laser modulation signal.
The outputs of Nos. 3 and 743 increase, and as a result, the laser bias current increases, laser light output fluctuation correction is performed, and uniform laser light output is obtained.

Next, the laser drive current of the laser LD4 will be described.

The first light quantity control signal output from the D / A converter 404, the light quantity control signal of the integrator 744 for inferring the temperature fluctuation due to self-heating associated with the modulation signal of the laser LD4, and the modulation signal of the laser LD3 are used. Laser LD3 with
The light amount control signal of the integrator 734 for inferring the temperature variation due to the heat interference from the input signal is input to each of the plurality of constant current circuits provided in the laser drive circuit 1114.

At this time, a laser bias current proportional to the light amount control signals of the integrators 744 and 734 is supplied, and L
The laser operating current proportional to the first light amount control signal of the LD4 is pulse-driven by the switching circuit that is ON / OFF controlled by the D4 laser modulation signal. Therefore,
The outputs of the integrators 744 and 734 increase in accordance with the laser modulation signal, and as a result, the laser bias current increases, the laser light output fluctuation correction is performed, and a uniform laser light output is obtained.

As described above, according to the third embodiment, in the semiconductor laser diode array having a plurality of laser emission points, it is possible to control the light quantity so that a uniform laser light output can always be obtained.

[0124]

As described above, according to the present invention,
The following effects are obtained.

(1) Since it is possible to suppress fluctuations in laser light output due to temperature fluctuations during image formation, it is possible to obtain gradation reproduction characteristics with high linearity without density unevenness, and to improve device quality and reliability. Can be improved.

(2) Since the fluctuation of the laser light output due to the droop characteristic and the thermal interference can be suppressed without feeding back the laser light output, the hunting phenomenon does not occur and the reliability of the apparatus can be improved.

(3) Since the laser light output fluctuation caused by the droop characteristic and thermal interference can be suppressed without using the feedback control of the laser light output, a simple and inexpensive system can be configured and the apparatus is economical. Can be improved.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a block circuit diagram showing the configuration of the first embodiment.

FIG. 3 is a flowchart showing a laser light output adjustment routine of the first embodiment.

FIG. 4 is a block circuit diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a block circuit diagram showing the configuration of the second embodiment.

FIG. 6 is a flowchart showing a laser light output adjusting routine of the second embodiment and the third embodiment of the present invention.

FIG. 7 is a block circuit diagram showing the configuration of the third embodiment.

FIG. 8 is a block circuit diagram showing a configuration of the third embodiment.

FIG. 9 is a block circuit diagram showing a configuration of a conventional example.

FIG. 10 is a block circuit diagram showing a configuration of a conventional example.

FIG. 11 is a flowchart showing image sequence control in the image forming apparatus.

FIG. 12 is a flowchart showing a laser light output adjustment routine of the above conventional example.

FIG. 13 is an external view showing the outline of a light source unit in the image forming apparatus.

FIG. 14 is an explanatory diagram showing a configuration of an optical system block in the image forming apparatus.

FIG. 15 is an explanatory diagram showing laser doping characteristics in the image forming apparatus.

FIG. 16 is an explanatory diagram showing a laser light output fluctuation due to thermal interference of laser in the image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Microprocessor, 2 ... Image controller, 12 ... Light source unit, 300 ... Selector, 301-304 ... Buffer latch circuit, 401-404 ... D / A converter, 501-504 ... Line buffer, 611, 621-623, 632 ~ 634, 643, 6
44 ... Integrator, 901-904 ... Adder, 1001-1004 ... Logical sum, 1101-1104 ... Laser drive circuit, 1201 ... Semiconductor laser diode array, 1202 ... Photodiode, 1203 ... LD light amount detection circuit, 1204 ... A / D converter, 1205 ... Latch circuit, 1301 ... Beam detector, 1302 ... Comparator, 1303 ... Timing signal forming circuit, 1401 ... Pulse generating circuit, 1402 ... Selector, 1411-1414 ... 3-state buffer.

Claims (6)

[Claims] 1. An image forming apparatus for irradiating a photosensitive member with a plurality of lasers to form an electrostatic latent image, comprising: a plurality of laser modulation means for independently modulating the light emitting points of the plurality of laser light emitting sources; and a laser drive. Means; a light quantity detecting means for detecting the light output of each light emitting source; and an individual laser so that the detection value of the light quantity detecting means for each laser becomes equal to a predetermined reference value at a predetermined timing other than image formation. A first light quantity control signal setting means for setting an operating current; a plurality of integration calculation means having different time constants and gains for integrating the laser modulation signal; and an output of the first light quantity control signal setting means. An image forming apparatus comprising: a first light quantity control signal and a second light quantity control signal setting means for setting a laser drive current based on an output signal of one or more integration calculation means. 2. The image forming apparatus according to claim 1, further comprising means for resetting the integral calculation means during operation of the first light amount control signal setting means. 3. The image forming apparatus according to claim 1, wherein the first light amount control signal and an output of one or more integral calculation means are added together, and an output of the addition means is proportional to the addition means. An image forming apparatus, comprising: a constant current circuit for controlling a laser operating current; and a laser driving unit including a switching circuit. 4. The image forming apparatus according to claim 1, further comprising a plurality of constant current circuits and switching circuits for controlling the laser operating current in proportion to the first light amount control signal and the output of the integral calculating means. An image forming apparatus having a configured laser driving unit. 5. The image forming apparatus according to claim 1, wherein a constant current circuit and a switching circuit for controlling a laser operating current proportional to the first light amount control signal, and a laser bias proportional to the output of the integral calculating means. An image forming apparatus comprising: a laser driving unit configured to include one or more constant current circuits for controlling a current. 6. The image forming apparatus according to claim 1, further comprising control means for pulse-lighting a semiconductor laser during setting of the first light amount control signal.