JPH0282676A - Light quantity controller for laser oscillator - Google Patents

Abstract

PURPOSE:To prevent the breakage, etc., of laser oscillators by comparing a detected light quantity with light quantity having been stored, detecting the first abnormal state on the basis of its comparison result, comparing a detected driving current value with a current value having been memorized, and detecting the second abnormal state on the basis of its comparison result. CONSTITUTION:In time of controlling light quantity, the driving current of a laser oscillator 11 is detected by a current detecting means 13, and the detected value is sent to a control means 19. The control means 19 detects the driving current abnormality of the laser oscillator 11 in accordance with the comparison result between the value detected by the current detecting means 13 and the peak value of the driving current having been stored in a storage means 17 after comparing them, and transmits a signal indicating an abnormal state to a display section, etc. In addition, the control means 19 detects the deterioration abnormality of the laser oscillator 11 in accordance with the comparison result between the value detected by a light quantity detecting means 12 and the light quantity in time of deterioration having been stored in the storage means 17 after comparing them, and transmits a signal indicating an abnormal state to the display section, etc.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is applicable to, for example, an image forming apparatus such as an electrophotographic laser printer or a copying machine, an optical disk device, or an optical communication device. The present invention relates to a light amount control device for a laser oscillator that controls the amount of light of a laser oscillator for obtaining a laser beam light to a predetermined value and detects an abnormal state of the laser oscillator.

(Prior Art) Recently, an electrophotographic laser printer has been developed that prints by scanning exposure using a laser beam output from a laser oscillator and an electrophotographic process.

Now, in this type of laser printer, a semiconductor laser oscillator is used as a laser oscillator for obtaining laser beam light. Generally, the light intensity of a semiconductor laser oscillator is very unstable due to the influence of temperature changes. Therefore, the light intensity of the laser oscillator is detected, and this detected light intensity is compared with a target setting value. By controlling the driving current of the laser oscillator according to the result, the amount of light from the laser oscillator is controlled to a predetermined value.

Furthermore, by using a cooling element or the like to keep the temperature of the laser oscillator itself constant, fluctuations in the amount of light due to temperature changes are also dealt with.

Conventional light intensity control uses an analog circuit, and while the detected light intensity is compared with a target set value, it is also compared with the light intensity when the laser oscillator deteriorates abnormally, and the laser oscillator deterioration is determined according to the comparison result. It also detects abnormalities.

However, since it is an analog method, a dedicated circuit is required for detecting deterioration abnormalities in the laser oscillator, and the set value of the deterioration abnormality detection level is not accurate, and the set value changes due to temperature rise.

In addition, since no special measures were taken to limit the drive current of the laser oscillator and protect the laser oscillator, controlling the amount of light could cause the drive current of the laser oscillator to increase due to temperature rise, causing damage to the laser oscillator. There was a problem.

(Problems to be Solved by the Invention) As described above, the present invention has the problem that a special dedicated circuit is required to detect deterioration abnormalities in the laser oscillator, and the detection level setting value fluctuates, resulting in poor accuracy. This was developed to solve the problem that it is not possible to protect the laser oscillator from damage by limiting the drive current when controlling the amount of light. A light amount control device for a laser oscillator that can detect abnormalities, do not change the detection level setting value, and prevent the drive current from exceeding the maximum drive current value when controlling the light amount, protecting the laser oscillator from destruction. The purpose is to provide

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a light amount detection means for detecting the light amount of a laser oscillator, a light amount setting means for setting the light amount of the laser oscillator, and a light amount setting means for setting the light amount by the light amount setting means. control means for controlling the light amount of the laser oscillator to a predetermined value by comparing the light amount detected by the light amount detection means with the light amount detected by the light amount detection means and controlling the driving current of the laser oscillator according to the comparison result;
When controlling the light amount by the control means, a current detection means for detecting the drive current of the laser oscillator, a storage means for storing the upper limit value of the drive current of the laser oscillator and the light amount when the laser oscillator is deteriorated; a first abnormality detection means for comparing the light amount detected by the light amount detection means and the light amount stored in the storage means and detecting a first abnormal state of the laser oscillator based on the comparison result; a second abnormality detection means for comparing the drive current value detected by the current detection means with the current value stored in the storage means and detecting a second abnormal state of the laser oscillator based on the comparison result; Equipped with:

(Function) The upper limit of the driving current of the laser oscillator and the light amount when the laser oscillator deteriorates are stored, and the stored light amount is compared with the light amount of the laser oscillator detected by the light amount detection means, and the comparison result is calculated. detecting a deterioration abnormality (first abnormal state) in the laser oscillator based on the above, detecting the drive current of the laser oscillator during light amount control, and comparing the detected drive current value with the above-mentioned stored current value; Based on the comparison result, a drive current abnormality (second abnormal state) of the laser oscillator is detected. All of these controls are digitally performed by a microprocessor.

As a result, the laser oscillator operates with the light intensity set by the light intensity setting means during one light intensity setting, and when the laser beam light is incident on the light intensity detection means, if the light intensity of the laser oscillator decreases, the laser oscillator is operated by the control means. The drive current is increased, but the current is controlled so as not to flow in excess of the drive current upper limit value. Therefore, the deterioration abnormality of the laser oscillator can be easily and accurately detected without using a special dedicated circuit as in the past, and the detection level setting value can be detected with high accuracy without fluctuation.

Furthermore, if the light intensity of the laser oscillator does not reach a predetermined value despite an increase in the drive current, the second abnormality detection means detects this, so that the drive current does not exceed the maximum drive current value when controlling the light intensity. This can protect the laser oscillator from breakage.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an outline of a light amount control device for a laser oscillator according to the present invention. In the figure, 11 is a laser oscillator, for example, a semiconductor laser oscillator is used.
A laser beam B modulated according to the image signal is output. Reference numeral 12 denotes a light amount detection means that detects a part of the laser beam B output from the laser oscillator 11 and performs photoelectric conversion.

Reference numeral 13 denotes a current detection means that detects the driving current of the laser oscillator 11 during light amount control. Reference numeral 14 denotes a rotating mirror such as a polygon mirror, which has, for example, six mirrors, and is rotated by a motor (not shown). An image is formed on the photoreceptor 15 by reflecting the laser beam B output from the laser oscillator 11 with this rotating rotating mirror and scanning the drum-shaped photoreceptor 15 as an image carrier in the image forming apparatus. It is now possible to do this.

16 is an fθ lens, and a laser oscillator B on the photoreceptor 15
The scanning speed is kept constant.

Reference numeral 17 denotes a storage means using a non-volatile memory, which stores the drive current upper limit value (maximum drive current value) of the laser oscillator 11 and the amount of light when the laser oscillator 11 is deteriorated. 18
is a light amount setting means that sets a target light amount (target value) of the laser oscillator 11.

Reference numeral 19 denotes a control means that includes an abnormality detection means and manages overall control, and is mainly composed of, for example, a CPU (Central Processing Unit).

In such a configuration, the storage means 17 stores the drive current upper limit value (maximum drive current value) of the laser oscillator 11 and the tip when the laser oscillator 11 deteriorates, as described above. Then, the light amount setting means 18 sets a predetermined light amount (
At the same time, the light amount detection means 12 detects (monitors) the light amount of the laser oscillator 11 and outputs the detected value to the control means 19. The control means 19 compares the detection value of the light amount detection means 12 and the setting value of the light amount setting means 18, and controls the drive current of the laser oscillator 11 according to the comparison result, thereby setting the light amount of the laser oscillator 11. The light amount is controlled so that it becomes equal to the value (target value).

Further, when controlling the amount of light, the current detection means 13 detects the drive current of the laser oscillator 11 and outputs the detected value to the control means 19. The control means 19 compares the detection value of the current detection means 13 with the drive current upper limit value stored in the storage means 17, and detects an abnormality in the drive current of the laser oscillator 11 according to the comparison result. Sends a signal indicating an abnormal condition to a display unit, etc. that does not operate.

Furthermore, the control means 19 detects a deterioration abnormality of the laser oscillator 11 according to the comparison result by comparing the detection value of the light amount detection means 12 and the light amount at the time of deterioration stored in the storage means 17, A signal indicating an abnormal state is transmitted to a display unit (not shown) or the like.

Next, an example in which an embodiment of the present invention is applied to a laser printer will be described.

FIG. 6 shows a schematic configuration of an electrophotographic monochrome laser printer. This laser printer is electrically connected to a host system (external device) such as a computer or word processor via a transmission control device (not shown), and accepts dot image data from the external device to modulate the laser beam. By doing so, writing is performed on the photoreceptor, and the written dot image data is developed and transferred onto paper.

That is, 100 is an apparatus main body, and a drum-shaped photoreceptor 101 is disposed within this main body 100, and this photoreceptor 101 is rotated in the direction of the arrow shown in the figure by a drive source (not shown). Around the photoconductor 101, along the direction of rotation thereof, there are provided a charge control type charger 102, an electrostatic latent image forming section 103, a developing device 104 that simultaneously performs development and cleaning,
Charge control type transfer chargers 105 are sequentially arranged.

A paper feed cassette 106 is provided in the lower part of the main body 100, and paper P as a recording medium taken out from the paper feed cassette 106 by a paper feed roller 107 is transferred between a photoreceptor 101 and a transfer charger 105. image transfer section 108 between
A paper output tray 10 provided on the upper surface of the main body 100 through
A conveyance path 110 leading to 9 is formed. Conveyance path 110
On the upstream side of the image transfer section 108, there is a pair of aligning rollers 1.
11, and a fixing device (heat roller) 112 on the downstream side.
and a pair of paper ejection rollers 113 are provided.

The electrostatic latent image forming section 103 includes a semiconductor laser oscillator (such as a laser diode) 114 that generates a laser beam B modulated according to dot image data from an external device (not shown), and a laser output from the laser oscillator 114. A lens system 115 such as a collimator lens that focuses the beam light B, a six-sided rotating mirror (polygon mirror) 116 that scans the laser beam B focused by this lens system 115, and a rotating mirror 116 that rotates at high speed. an fθ lens 118 that passes the laser beam B scanned by the rotating mirror 116, a reflecting mirror 119, 120 that reflects the laser beam B that has passed through the fθ lens 118 toward the photoreceptor 101,
A correction lens 121 allows the laser beam B reflected by the reflecting mirrors 119 and 120 to pass through and guides it to the surface of the photoreceptor 101, and a beam photodetector 122 (not shown) detects the laser beam B scanned by the rotating mirror 116. (No)

In such a configuration, when a print start signal is received from an external device, the photoreceptor 101 rotates and the photoreceptor 1
01 is uniformly charged by the charging device 102 so that the surface potential becomes, for example, about -600 volts.

Next, when receiving dot image data from an external device,
The electrostatic Im forming unit 103 outputs a laser beam B modulated according to the dot image data, and scans and exposes the charged surface of the photoreceptor 101 with the laser beam B. Forms an electrostatic latent image on the surface.

The electrostatic latent image formed on the photoreceptor 101 is reversely developed by the developing device 104, thereby being visualized and becomes a toner image. At this time, the developing device 104 removes (cleans) the transfer residual toner remaining on the photoreceptor 101 at the same time as the development.

The toner image on the photoconductor 101 is transferred to an image transfer section 108.
Due to the action of the transfer charger 105, the paper feed cassette 1
The image is transferred onto the paper P conveyed from 06. The paper P on which the toner image has been transferred is conveyed to a fixing device 112, where the toner image is fixed, and then discharged onto a paper discharge tray 109 by a pair of paper discharge rollers 113.

Furthermore, after completing the image formation, the electrostatic Pi image forming section 10
3, the photoreceptor 101 is neutralized. That is, first, the transfer charger 105 is turned off. At this time, since the positive charge from the transfer charger 105 remains between the transfer charger 105 and the charger 102 of the photoreceptor 101, the photoreceptor 101 is uniformly charged with a negative charge by the charger 102. After charging, the charging device 102 is turned off.

Thereafter, the laser oscillator 114 is forced to emit light (no light modulation is performed), the rotating mirror 116 is rotated, and the entire surface of the photoreceptor 101 is exposed to the laser beam B scanned by the rotating mirror 116. , the photoreceptor 101 is neutralized, and then the rotation of the photoreceptor 101 is stopped and the process ends. These controls are performed by a control section that will be described later.

FIG. 5 shows the control section of the laser printer constructed as described above. This control unit is based on the CPU (central
A processing unit) 201 is used as a control center, a ROM (read only memory) 202 stores a system program, a ROM 203 stores a first data table, and an R used as a working memory.
AM (random access memory) 204, rewritable non-volatile RA in which the second data table is stored
It basically includes an M205, a timer 206, an input/output port 207, a print data write control circuit 208, and an interface control circuit 209 that controls the ink face with an external device.

The second data table of the nonvolatile RAM 205 stores the drive current upper limit value (maximum drive current value) of the laser oscillator 114 and the amount of light when the laser oscillator 114 is deteriorated. Here, in this embodiment, the light intensity when the laser oscillator 114 deteriorates is about 70% of the setting value set by a light intensity setting device 222, which will be described later, and the light intensity is set by the light intensity setting device 222. When it is done,
The CPU 201 automatically calculates the value and stores it in the RAM 205. Note that this value may be fixedly stored in advance.

The timer 206 is a general-purpose timer, and generates basic timing signals for controlling, for example, paper conveyance and processes around the photoreceptor.

The input/output boat 207 outputs display data to the operation display section 210, inputs various switch data, etc., inputs from various detectors (microswitches, sensors, etc.) 211, drive system (various motors, clutches, solenoids, etc.)
Output to drive circuit 213 that drives 212, high voltage power supply 2
14, etc., and an output signal from a temperature detection element (thermistor, etc.) 216 provided in the fixing device 112,
input/output to the heater control circuit 218 that controls the temperature of the heater lamp 217 of No. 2;
input/output to the toner concentration control circuit 221 that controls the toner replenishment solenoid 220 that replenishes toner to the developing device 104 by inputting the output signal of the toner concentration sensor 219 that determines the target light amount of the laser oscillator 1]4. The input/output signal to the light intensity setting device 222 for setting the laser oscillator 114 and the output signal of the monitor diode 223 for detecting (monitoring) the light intensity of the laser oscillator 114 are input to the laser beam 1 control circuit 224 for controlling each light of the laser oscillator 114. Perform human output etc.

The monitor diode 223 is, for example, a photodiode, and is provided integrally within the laser oscillator 114.

The laser light amount control circuit 224 includes a monitor diode 223
By comparing the light amount (detection value) detected with the light amount (detection value) and the light amount (setting value) set by the light amount setting device 222, and controlling the driving flow 7Ii of the laser oscillator 114 according to the comparison result, the laser oscillator 114 is controlled. The light amount of the laser oscillator 114 is controlled so that the light amount is equal to a set value (target value).

The print data write control circuit 208 includes the laser oscillator 114
The laser modulation circuit 225 that performs optical modulation control is controlled to write the print data of the video image to a predetermined position on the photoreceptor 101. At this time, the beam photodetector 122 detects the laser beam B being scanned by the rotating mirror 116, and the beam photodetector circuit 226 generates a horizontal synchronization signal by shaping the output signal of the laser beam B. This is sent to the print data write control circuit 208.

The interface control circuit 209 outputs status data to an external device, and receives command data and print data from the external device.

FIG. 4 shows details of the laser light amount control circuit 224. That is, a circuit composed of NPN transistors 301 and 302 and resistors 303 and 304 is a driving circuit for a laser oscillator (laser diode) 114. The amount of light from the laser oscillator 114 is determined by the sum of the currents flowing through the resistors 303 and 304. The current flowing through the resistor 303 is controlled by the base voltage of the transistor 301, and similarly the current flowing through the resistor 304 is controlled by the base voltage of the transistor 301.
It is controlled by the base voltage of 2.

The light intensity of the laser oscillator 114 is set based on the output value of the light intensity setting device 222. The output value of the light amount setting device 222 is
The data is input to the CPU 201 via the input/output port 207, subjected to predetermined processing, and outputted from the input/output port 207 as appropriate control data. The control data output from the input/output board 207 is converted into an analog signal by the D/A converter 305, then impedance-converted by the voltage follower 306, and applied to the base of the transistor 301 as an appropriate voltage.

The base voltage of the transistor 302 is the same as that of the laser oscillator 11.
A bias current below the threshold level of the drive current of No. 4 is set to flow through the resistor 304, and control data corresponding to a value set in the CPU 201 in advance is output from the input/output port 207. The control data output from the input/output boat 207 is sent to the D/A converter 30.
After being converted into an analog signal in step 5, the impedance is converted by voltage follower 307 to control the base voltage of transistor 302.

The laser oscillator 114 is modulated by the field effect transistors 308 and 308 by a modulation control signal according to the dot image data output from the print data write control circuit 208.
This is done by controlling the switching of transistor 309 and turning on and off the base voltage of transistor 301.

The monitor diode 223 detects the amount of light from the laser oscillator 114 and converts it into an electrical signal. The output signal of the monitor diode 223 is amplified by an operational amplifier 310, converted to a digital signal by an A/D converter 311, and then
It is input to the human output port 207 and read into the CPU 201.

Note that resistors 312, 313, and 314 are operational amplifiers 310
This is a constant that sets the amplification factor of .

The voltage follower 315 converts the drive current of the laser oscillator 114 into a voltage into an impedance. Then, the output voltage of the voltage follower 315 is the A/D
After being converted into a digital signal by the converter 311, it is input to the human output port 207 and read into the CPU 201.

The voltage follower 316 converts the bias current of the laser oscillator 114 into a voltage into an impedance. Then, the output voltage of the voltage follower 316 is A
After being converted into a digital signal by the /D converter 311, it is input to the input/output board 207 and read into the CPU 201.

In such a configuration, voltage follower 315.
The sum of the output values 316 indicates the total drive current of the laser oscillator 114, and the output value of the operational amplifier 310 indicates the amount of light from the laser oscillator 114 detected by the monitor diode 223.

Next, the operation in the above configuration will be explained. First, the process of initializing the drive current for the laser oscillator 114 will be described with reference to the flowchart shown in FIG. First, in step Sll, clear the control number counter that counts the number of times the drive current is controlled, and then in step Sll.
Proceed to step 12. In step S12, approximately 2 of the maximum drive current
A current value of 0% (control data for setting the bias current) is output to the input/output port 207, and the process advances to step 813.

Here, the current value of about 20% of the maximum drive current is r33oJ if the maximum drive current value is rFFHJ, for example.
It is.

In step S13, the laser oscillator 114 is turned on, and the process proceeds to step S14. In step S14, the output value of the monitor diode 223 is read, and the process proceeds to step S15. In step S15, the control number counter is counted up, and the process proceeds to step S16. Step S16
Then, the value of the control number counter is compared with a preset control number of times specified value (for example, 64) 1), and if the value of the control number of times counter is greater than or equal to the controlled number of times specified value, abnormality processing of the laser oscillator 114 (for example, laser The oscillator 114 is turned off and an abnormal signal is output to an external device).

In step S16, if the value of the control number counter is less than the control number specified value, the process advances to step S17. In step S17, the output value of the monitor diode 223 read in step S14 is compared with the set value ("1 standard value") set by the light amount setting device 222, and if the two are equal, the process advances to step S18. , At this time, the drive current value output to the input/output port 207 is stored in the RAM 205.
The process then proceeds to step 819. Note that when the laser oscillator 114 is turned on thereafter, the drive current value stored in the RAM 205 is used as the initial drive current value. Step S
In step 19, the laser oscillator 114 is turned off, and the process ends.

In step S17, if the output value of the monitor diode 223 is smaller than the set value, the process advances to step S20.

In step S20, the set value and the monitor diode 223 are
The difference between the output value and the output value is determined, and if the absolute value exceeds the drive current control specified value (for example, 5, 1), step S21
Proceed to. In step S21, the drive current value in the RAM 205 is increased by, for example, 4 bits, and the process proceeds to step S22. In step S20, if the absolute value of the difference between the set value and the output value of the monitor diode 223 is less than or equal to the drive current control specified value, the process proceeds to step S23. In step 82B, the drive current value in the RAM 205 is increased by, for example, 1 bit, and the process proceeds to step S22.

In step S22, the drive current value controlled as described above is output to the human output boat 207 as control data, and the processes from step S14 onwards are repeated.

In step S17, if the output value of the monitor diode 223 is larger than the set value, the process advances to step S24.

In step S24, the set value and the monitor diode 223 are
If the absolute value exceeds the drive current control specified value (for example, 5), step S25
Proceed to. In step S25, the drive current value in the RAM 205 is decreased by, for example, 4 bits, and the process proceeds to step S26. In step S24, if the absolute value of the difference between the set value and the output value of the monitor diode 223 is less than or equal to the drive current control specified value, the process advances to step S27. In step S27, the drive current value in the RAM 205 is decreased by, for example, 1 bit, and the process proceeds to step S26.

In step S26, the drive current value controlled as described above is output to the input/output port 207 as control data, and the processes from step S14 onwards are repeated.

Here, the drive current control specified value means that the control increase/decrease range is divided into two stages depending on the magnitude of the difference between the set value set by the light intensity setting device 222 and the output value of the monitor diode 223, and the control is shortened. Therefore, a boundary value for this two-stage control is required, and this boundary value is referred to as the boundary value.

Next, the second section regarding the light amount control process of the laser oscillator 114 will be described.
This will be explained with reference to the flowchart shown in the figure. first,
In step 531, the output value of the monitor diode 223 is read, and the process proceeds to step S32. In step S32, the output value of the monitor diode 223 read in step S31 and the laser oscillator 114 stored in the RAM 205 are determined.
The output value of the monitor diode 223 is compared with the light Q(MIN) when the signal is degraded, and the output value of the monitor diode 223 is
IN), the process proceeds to step 333. Step 3
33, for example, it is determined that the laser oscillator 114 has deteriorated abnormally, and a laser abnormality process is performed (for example, the laser oscillator 114 is turned off, a signal indicating an abnormal state is sent to the operation display section 210, and the abnormality is displayed). end.

In step S32, if the output value of the monitor diode 223 is greater than the optical ffi (MIN) at the time of deterioration,
The process advances to step S34. In step S34, the set value set by the light amount setter 222 is read as a target value, and the process proceeds to step S35.

In step S35, the output value of the monitor diode 223 read in step S31 is compared with the set value (target value) set by the light amount setting device 222, and if the two are equal, the process advances to step S36.

In step S35, if the output value of the monitor diode 223 is smaller than the set value, the process advances to step S37.

In step S37, it is determined that the amount of light from the laser oscillator 114 is insufficient, and the drive current value in the RAM 205 is increased by, for example, 1 bit, and the process proceeds to step S36.

In step S35, if the output value of the monitor diode 223 is larger than the set value, the process advances to step S38.

In step S38, it is determined that the amount of light from the laser oscillator 114 is excessive, and the drive current value in the RAM 205 is decreased by, for example, 1 bit, and the process proceeds to step S36.

In step S36, the value of the drive current flowing through the laser oscillator 114 at this time is read, and the process proceeds to step S39.

In step S39, the drive current value read in step S36 and the drive current upper limit value (
If the read drive current value is greater than or equal to the drive current upper limit value (MAX), the process advances to step 33B.

In step 333, for example, it is determined that there is an abnormality in the drive current of the laser oscillator 114, and laser abnormality processing is performed (for example, the laser oscillator 114 is turned off, a signal indicating an abnormal state is sent to the operation display section 210, and the abnormality is displayed). The process ends.

In step S39, if the read drive current value is less than the drive current upper limit value (MAX), the process advances to step S40. In step S40, the drive current value controlled in step S37 or S38 is output to the input/output port 207 as control data, and the process proceeds to step S41. Step S4
In step S1, a control number counter that counts the number of times the light amount is controlled is incremented, and the process proceeds to step S42.

In step S42, the value of the control number counter is compared with a preset control number of times regulation value (for example, 32H), and if the value of the control number of times counter is less than the control number of times regulation value, the processing from step S31 onward is repeated. In step S42, if the value of the control number counter is equal to or greater than the control number specified value, the process advances to step 343. Step 843
Now, clear the control number counter and end the process.

In this way, the upper limit of the drive current of the laser oscillator and the amount of light when the laser oscillator deteriorates are stored in the RAM, and the stored amount of light is compared with the amount of light from the laser oscillator detected by the monitor diode. Based on the comparison results, abnormal deterioration of the laser oscillator is detected, and the drive current of the laser oscillator is detected during light intensity control, and the detected drive current value and the above-mentioned stored current value are compared. Based on this, abnormalities in the driving current of the laser oscillator are detected. All these controls are digitally performed by the CPU.

As a result, the laser beam operates with the light intensity set by the light intensity setting device during one light intensity setting, and if the laser beam light enters the monitor diode and the light intensity of the laser oscillator decreases, the laser oscillator will be activated under the control of the CPU. However, if the output value level of the monitor diode is below the deterioration light amount level, a deterioration abnormality is detected. Therefore, deterioration abnormalities in the laser oscillator can be easily and accurately detected without using a special dedicated circuit as in the past.
Moreover, there is no fluctuation in the detection level setting value, and detection can be performed with high accuracy.

In addition, if the light intensity of the laser oscillator does not reach a predetermined value despite the increase in drive current, the CPU detects this, which prevents the drive current from exceeding the maximum drive current value when controlling the light intensity, and The oscillator can be protected from destruction. However, this drive current abnormality can also be detected easily and accurately without using a special dedicated circuit.

In the above embodiment, abnormality in the deterioration of the laser oscillator is detected by comparing the amount of light stored in the RAM at the time of deterioration of the laser oscillator with the actually detected output value of the monitor diode. For example, by storing in advance in the RAM the relationship between the drive current value of the laser oscillator and the output value of the monitor diode, abnormal deterioration of the laser oscillator can be detected.

Further, in the above embodiment, a case has been described in which the device is applied to a light amount control device of a laser oscillator in an electrophotographic laser printer, but the present invention is not limited to this. For example, the laser beam output from a laser oscillator The present invention can be similarly applied to an electrophotographic copying machine that forms an image by scanning exposure with light and an electrophotographic process, or to a light amount control device for a laser oscillator in an optical disk device or an optical communication device.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to easily and accurately detect a deterioration abnormality in a laser oscillator without using a special dedicated circuit, there is no change in the detection level setting value, and the light intensity is It is possible to provide a light amount control device for a laser oscillator that can prevent the drive current from exceeding the maximum drive current value during control and protect the laser oscillator from damage.

[Brief explanation of the drawing]

The figures are for explaining one embodiment of the present invention, and FIG. 1 is a block diagram showing an overview of a light amount control device for a laser oscillator according to the present invention, and FIG. 2 is a diagram for explaining the light amount control process of a laser oscillator. Flowchart, FIG. 3 is a flowchart explaining the initial setting process of the drive current of the laser oscillator, FIG. 4 is a block diagram showing the details of the laser light amount control circuit, and FIG. 5 is a block diagram showing the structure of the control section of the laser printer. , FIG. 6 is a block diagram schematically showing a laser printer to which a light amount control device for a laser oscillator according to the present invention is applied. 11... Laser oscillator, B... Laser beam light, 1
2... Light amount detection means, 13... Current detection means, 14
... Rotating mirror 15 ... Photoreceptor, 17 ... Storage means, 18 ... Light amount setting means, one ... Control means,
114...Semiconductor laser oscillator, 116...Rotating mirror 201...CPU, 205...Nonvolatile RAM. 207...Person output port, 222...Tip setting device,
223... Monitor diode, 224... Laser light amount control circuit, 305... D/A converter, 311...
A/D converter. Applicant's agent Patent attorney Takehiko Suzutsuta Figure 5 Figure 1

Claims (1)

[Scope of Claims] A light amount detection means for detecting the light amount of a laser oscillator; a light amount setting means for setting the light amount of the laser oscillator; and a light amount set by the light amount setting means and a light amount detected by the light amount detection means. control means for controlling the light intensity of the laser oscillator to a predetermined value by comparing the drive current of the laser oscillator according to the comparison result; a current detection means for detecting a driving current; a storage means for storing an upper limit value of the driving current of the laser oscillator and a light amount when the laser oscillator is deteriorated; and a storage means for storing the light amount detected by the light amount detection means and the storage means. a first abnormality detection means that compares the amount of light with a stored amount of light and detects a first abnormal state of the laser oscillator based on the comparison result; and a drive current value detected by the current detection means and the storage means. A light amount control device for a laser oscillator, comprising second abnormality detection means for comparing the current value stored in the current value and detecting a second abnormal state of the laser oscillator based on the comparison result. .