JPH03202365A - Device for controlling light quantity for laser oscillator - Google Patents

Abstract

PURPOSE:To obtain a target light quantity in a short time after starting a light quantity control by controlling the quantity of light of a laser oscillator based on the values of drive electric current stored in advance after starting an image formation operation without resetting values of drive current of the oscillator. CONSTITUTION:A control means 27 causes in advance a light quantity control means 21 to control the quantity of light of a semiconductor laser oscillator 11 before a printing command is inputted into an input mean 26, while the values of drive electric current set in a drive means 22 is stored in a memory means 28. And after a printing command has been inputted into the means 26, the values of current stored in the means 28 are read out, whereby the means 21 controls the quantity of light of the oscillator 11 based on the values of drive current having been read out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a light amount control device for a laser oscillator used in an image forming apparatus such as a laser printer or a digital copying machine.

(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.

In this type of laser printer, a semiconductor laser oscillator is used as a laser oscillator for obtaining a laser beam. Generally, the amount of light from a semiconductor laser oscillator is very unstable with respect to temperature, so the amount of light from the semiconductor laser oscillator is usually stabilized using a light amount control device or the like. In that case, print command (image forming operation start command)
After this is input, the driving current value of the semiconductor laser oscillator is initialized, and thereafter the light amount of the semiconductor laser oscillator is controlled.

(38) Conventionally, after a print command is input, the drive current value of the semiconductor laser oscillator is initialized to control the light amount.
It took a certain amount of time to reach the target light intensity.

In image forming devices such as laser printers and digital copying machines, the time from when a print or copy operation start command is input until one print or copy is ejected, that is, the first print or first copy time is short. Moderate. Therefore, if it takes a long time to reach the target light amount, there is a problem because the start of the printing or copying operation will be delayed.

Furthermore, the higher the speed of a laser printer or digital copying machine, the shorter the first print or first copy time, and therefore the longer it takes to reach the target light amount, the more problematic it becomes.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a light amount control device for a laser oscillator that reaches a target light amount in a short time after starting the light amount control when controlling the light amount of the laser oscillator after an image forming operation start command is input. With the goal.

[Structure of the Invention (Means for Solving the Problems) The light amount control device for a laser oscillator of the present invention scans the image carrier with a laser beam output from the laser oscillator, thereby controlling the amount of light on the image carrier. An image forming means for forming an image, a driving means for driving the laser oscillator with current, a light amount detection means for detecting the amount of light from the laser oscillator, and a drive current for the driving means in accordance with a light amount detection signal of the light amount detection means. a light amount control means for controlling the light amount of the laser oscillator by setting a value; a storage means for storing the drive current value set by the light amount control means;
Before a command to start an image forming operation by the image forming means is input, the light amount of the laser oscillator is controlled in advance by the light amount control means, the drive current value set at that time is stored in the storage means, and the image forming means is stored in the storage means. and control means for controlling the light amount of the laser oscillator by the light amount control means based on the drive current value stored in the storage means after an instruction to start an image forming operation by the forming means is input. .

(Function) After the image forming operation starts, the light intensity of the laser oscillator is controlled based on the drive current value stored in advance without initializing the drive current value of the laser oscillator. to reach the target light intensity.

(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 semiconductor laser oscillator according to the present invention. In the figure, a polygon mirror 9 scans a laser beam 12 output from a semiconductor laser oscillator 11 onto a drum-shaped photoreceptor 10 serving as an image carrier in an image forming apparatus in the direction of the arrow.

The driving means 22 inputs a modulation signal and drives the semiconductor laser oscillator 11 with current to record information at a predetermined position on the photoreceptor 10. The light amount detection means 15 detects the amount of light of the laser beam 14 output from the semiconductor laser oscillator 11.

The light amount control means 21 is mainly composed of a microcomputer, for example, and controls the laser beam output from the semiconductor laser oscillator 11 by setting the driving current value of the driving means 22 according to the detection result of the light amount detection means 15. Control the amount of light uniformly.

26 is an input means for inputting a print command (image forming operation start command), and a control means 27 controls the light quantity control means 21 in advance before the print command is input to the input means 26.
The light amount of the semiconductor laser oscillator 11 is controlled by
At this time, the drive current value set for the drive means 22 is stored in the storage means 28. After the print command is input to the input means 26, the drive current value stored in the storage means 28 is read out, and the light amount control means 21 controls the light amount of the semiconductor laser oscillator 11 based on the read drive current value. It is now possible to

FIG. 2 is a block diagram showing in detail a part of the light amount control device for a semiconductor laser oscillator according to the present invention. In the figure, 30 is a semiconductor laser oscillator, which is composed of a laser diode 31 that outputs a laser beam, and a monitoring photodiode 32 that detects the intensity of the laser beam output from the laser diode 31. The laser diode 31 is driven with a constant current by a constant current circuit composed of a transistor 33 and a resistor 34. The base of the transistor 33 is connected to the output of the D/A conversion circuit 35 and the collector of the transistor 36. The drive current flowing through the semiconductor laser oscillator 30 is transmitted through the D/A conversion circuit 3.
It is proportional to the output voltage of 5.

The transistor 36 repeatedly turns on and off in response to a laser modulation signal output from the laser modulation control circuit 37, thereby modulating the laser diode 31. In this case, when the laser modulation signal is high level, the laser diode 3
1 goes out and emits light at low level. D/A conversion circuit 3
5 converts the digital value of the laser drive current output from the human output register 38 into an analog voltage.

On the other hand, a current proportional to the beam intensity of the laser diode 31 flows through the monitor photodiode 32 . Resistor 39 converts the current flowing through photodiode 32 into voltage. The converted voltage is applied to an operational amplifier 40. resistance 41
, a variable resistor 42, which performs non-inverting amplification.

Here, the variable resistor 42 is used to adjust the amplification factor, and its purpose is to correct differences in current characteristics flowing through the monitoring photodiode 32 with respect to the beam intensity of the laser diode 31 due to variations in the semiconductor laser oscillator 30. .

The output of the operational amplifier 40 is inputted to one side input terminal of the comparator 43, and the reference voltage Vre inputted to the + side terminal.
It is compared with f2. This reference voltage Vref2 sets the target light intensity of the laser diode 31. When the output of the operational amplifier 40 is less than Vref2, it is assumed that the target light intensity has not been reached, and the output of the comparator 43 becomes high level, and the output of the operational amplifier 40 reaches Vref2. When the target light amount is exceeded, the output of the comparator 43 becomes low level, indicating that the target light amount has been reached.

The comparison result of the comparator 43 is input to the latch circuit 44. The latch circuit 44 latches the output of the comparator 43 in synchronization with the input latch pulse output from the selector 45. The output of the latch circuit 44 is input to the input/output register 38, which controls the entire printer (not shown). Processed by the CPU that controls the

The selector 45 is a selector that selects the input latch pulse A output from the human output register 38 and the input latch pulse B output from the laser modulation control circuit 37 using a latch pulse switching signal output from the input/output register 38. When the latch pulse switching signal is low level, input latch pulse A is selected, and when it is high level, input latch pulse B is selected.

A beam detector 46 detects the position of the scanned laser beam 13, and uses a bin diode, for example. When the scanned laser beam 13 is incident, a current proportional to the intensity of the incident laser beam flows through the bin diode 46. Resistor 47 converts the current flowing through bin diode 46 into voltage. The converted voltage is sent to the comparator 48
The signal is inputted to one side terminal of , is compared with the reference voltage Vrefl inputted to the + side terminal, and is inputted to the laser modulation control circuit 37 as a negative pulse beam detection signal.

In response to the continuous pulse output of the beam detection signal, the laser modulation control circuit 37 sets the beam detection ready signal to the input/output register 38 as a beam detection ready signal from a low level to a high level (see e+g in FIG. 3). ).

The latch pulse switching signal output from the human output register 38 outputs a low level when the beam detection ready signal is at a low level, and outputs a high level when the beam detection ready signal is at a high level (see the third diagram).

When the beam detection signal is output, the laser modulation control circuit 37 outputs an input latch pulse B outside the recording area based on the beam detection signal (see FIG. 3). Further, this input latch pulse B is input as an interrupt signal to the interrupt input of the CPU.

In FIG. 2, reference numerals 49 and 50 indicate internal buses of the CPU, each of which is connected to a CPU (not shown). Further, 51 is an ink face signal, which is connected to a printer control circuit (not shown).

Next, the operation will be explained with reference to the timing chart shown in FIG. 3 and the flow chart shown in FIG. 4. first,
When the power is turned on, the fixing heater starts heating.
) Initialize the laser drive current output from the human output register 38 (S2). Next, the input latch pulse A is selected by the selector 45 using the latch pulse switching signal output from the human output register 38 (S3).

Next, the laser modulation signal output from the laser modulation control circuit 37 is forcibly turned on (S4). Next, the laser drive current is incremented (S5) and output from the input/output register 38, and then D/A converted by the D/A conversion circuit 35, and a current starts flowing to the laser diode 31.

After a predetermined time delay (S6), when the input latch pulse A is output from the human output register 38 (S7), the comparator 43
The comparison result is latched in the latch circuit 44. Next, it is determined whether the comparison result latched by the latch circuit 44 has reached the target light amount (S8). Here, the target light amount means that the output voltage of the operational amplifier 40 is equal to the reference voltage V of the comparator 43.
This is when ref2 is reached, and at this time the output of the comparator 43 changes from 1'' to "0".

If the target light amount has not been reached in step S8, the process returns to step S5 and is repeated until the target light amount is reached.

When the target light intensity is reached in step S8, the laser drive current value at this time is stored in a RAM (not shown) (S9), and the laser modulation signal is forcibly turned off (S10).
.

The loop continues until the fixing heater becomes ready in step S11, and when the fixing heater becomes ready, it waits for a print command (
S12). When the print command is input, the mirror motor is turned on (513), the laser drive current value stored in the RAM in step S9 is read out (514), and 1/n of the read laser drive current value is output from the input/output register 38. (S15). Next, the laser modulation signal is forced on (516) and the laser drive current is incremented (516).
S17).

After a predetermined time delay (518), it is determined whether the beam detection ready signal output from the laser modulation control circuit 37 is beam detection ready (S19). Here, beam detection ready means that the beam intensity of the scanning beam incident on the beam detector 46 exceeds the reference voltage Vref of the comparator 48,
This is when the beam detection signal is generated continuously (Fig. 3e)
, see g).

If the beam detection is not ready in step S19, the process returns to step S17 and is repeated until the beam detection is ready.

When the beam detection becomes ready in step S19, the laser modulation signal is forcibly turned off (S20). The laser modulation control circuit 37 outputs a beam detection ready signal, and at the same time emits a laser modulation signal in a sampled manner outside the recording area based on the beam detection signal, and similarly outputs an input latch pulse B outside the recording area based on the beam detection signal. Output (Fig. 3 f, 1
reference).

Next, in step S21, the input latch pulse B is selected by the selector 45 using the latch pulse switching signal output from the input/output register 38 (see the third diagram). Next, the CPU interrupt is canceled (S22), and the loop is repeated until the input latch pulse B of the interrupt signal is generated (523).

Here, when an interrupt signal occurs, the input latch pulse B
The comparison result of the comparator 43 is latched by the latch circuit 44.

Next, it is determined whether the comparison result latched by the latch circuit 44 has reached the target light amount (S24).

When the target light amount has not been reached, the laser drive current is incremented (S25) and output to the D/A conversion circuit 35.

Thereafter, the process returns to step S23 and is repeated until the target light amount is reached. When the target light amount is reached, the laser drive current is decremented (S26) and the process returns to step S23.

After reaching the target light intensity, the light intensity control of the semiconductor laser oscillator 30 is continued every time an interrupt signal is generated.

[Effects of the Invention] As described in detail above, according to the light amount control device for a laser oscillator of the present invention, after the image forming operation starts, the drive current value of the laser oscillator can be changed to a pre-stored drive current value without initializing the drive current value. Since the light amount of the laser oscillator is controlled based on the following, the target light amount is reached in a short time after starting the light amount control.

[Brief explanation of drawings]

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, and FIG. 2 shows a part of the light amount control device for a laser oscillator in detail. The block diagram, FIG. 3 is a timing chart explaining the operation, and FIG. 4 is a flow chart explaining the operation. 9... Polygon mirror 1o... Photoreceptor (image carrier), 11... Laser oscillator, 12... Laser beam, 15... Light amount detection means, 21... Light amount control means,
22... Drive means, 26... Input means, 27...
Control means, 28... Storage means.

Claims (1)

[Scope of Claims] An image forming means for forming an image on the image carrier by scanning the image carrier with a laser beam output from a laser oscillator, and a driving means for driving the laser oscillator with current. , a light amount detection means for detecting the light amount of the laser oscillator; and a light amount control means for controlling the light amount of the laser oscillator by setting a drive current value of the driving means according to a light amount detection signal of the light amount detection means. , a storage means for storing a drive current value set by the light amount control means, and a light amount control unit for controlling the light amount of the laser oscillator in advance by the light amount control means before an instruction to start an image forming operation by the image forming means is input. , the drive current value set at that time is stored in the storage means, and after an instruction to start the image forming operation by the image forming means is input, the light amount control means controls the drive current value based on the drive current value stored in the storage means. A light amount control device for a laser oscillator, comprising: a control means for controlling the light amount of the laser oscillator.