JP2669353B2 - Recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus, and more particularly, to a recording apparatus characterized by a structure of a laser light amount control circuit of an electrophotographic recording apparatus.

[0002]

2. Description of the Related Art In an electrophotographic recording apparatus, an image signal sent from a host computer is received by a mechanical control board and input to a laser head. In this laser head, the laser is output in accordance with the dot image to form an electrostatic latent image on the photosensitive drum.

Conventionally, a laser light amount control circuit for controlling the light amount of a laser provided in a laser head has a structure as shown in FIG. In FIG. 4, a PWM signal is a signal for controlling a current flowing through the laser diode 100 and is a constant pulse wave output from an output port of a CPU (not shown). The PWM signal is output constantly when the polygon motor of the laser head is driven and a printing state is established.

The control operation of this laser light amount control circuit is as follows. When the PWM signal becomes L level, the charge becomes 5
From the power source of V through the resistors R2 and R3, the capacitors C1 and
It flows into C2, and the capacitors 101 and 102 are charged. Then, when the PWM signal becomes H level, the electric charge is discharged through the resistors R3 and R5. The pulse waveform of the PWM signal is smoothed at the base voltage portion of the transistor 103 as shown in FIG. When the ratio of the H level of the pulse of the PWM signal is high, the base voltage of the transistor 103 is high, and when the ratio is low, the base voltage is low. Then, when LDON goes high, the base voltage of the transistor 103 operates the emitter voltage of the transistor 104. When the base voltage of the transistor 103 is high, the emitter voltage of the transistor 104 is high, and when it is low, the emitter voltage of the transistor 104 is low.

Here, LDON is a laser diode 10
This is a signal for turning on 0, and if the emitter voltage of the transistor 104 is high when this LDON is at the H level, the collector / emitter current of the transistors 105 and 106 becomes large. On the contrary, if the emitter voltage of the transistor 104 is low, the collector / emitter current of the transistors 105 and 106 becomes small.

The collector of the transistor 106
Since the emitter current is connected to the laser diode 100, the current of the laser diode 100 can be controlled. Thereby, the transistors 105 and 106
The collector / emitter current flowing through the laser diode, that is, the current of the laser diode 100 is determined by the base voltage of the transistor 103, that is, the ratio of the H level and the L level of the PWM signal.

The light quantity of the laser diode 100 is received by the photodiode 110, and the cathode voltage and the reference voltage VREF are compared by the comparator 200. When the cathode voltage is higher than the reference voltage VREF, COMP is set to the H level, and when the cathode voltage is lower than the reference voltage VREF, the COMP is set to the L level. Then, this COMP is detected by the CPU,
If COMP is at H level, the H level ratio of the PWM signal is reduced, and if COMP is at L level, PWM
Increase the H level ratio of the signal. Thus, the current value of the laser diode 100 is controlled to a current value corresponding to the reference voltage VREF.

The PWM signal for adjusting the light quantity of the laser diode 100 uses the numerical values from 0 to 255 to change the time of the H level within the constant period T. Therefore, the maximum H level time is TH. However,
T> TH, and by setting a value of 0 to 255, P
The WM signal changes between 0 and TH at minimum intervals TH / 255.

The startup process of the laser diode 100 will be described. When printing is started, the signal LDON for turning on the laser diode 100 is turned on.
At the same time, a specific value is set in the PWM signal.
For example, 160 or the like is output to make the detection voltage of the photodiode 110 corresponding to the laser light amount higher than the reference voltage VREF.

Next, when the laser light amount becomes higher than the reference value, the set value of the PWM signal is lowered. Then, when the amount of laser light becomes lower than the reference value, the average of the set value of the PWM signal at that time and the initial value 160 is calculated. Then, this average value is input to the PWM signal. After a while
The laser light amount is adjusted by finely adjusting the set value of the PWM signal according to the reference voltage value so that the laser light amount is stabilized.

Further, the control of the laser light amount during printing is performed by rotating the polygon scanner of the laser head so that the laser beam amount is not written on the photosensitive drum and 100 μm before the horizontal synchronizing signal.
The laser diode 100 is turned on for a time of about s, the signal of the comparator 200 is detected in this state, and the PWM signal is finely adjusted so as to become the reference voltage.

[0012]

However, in the above-mentioned conventional recording apparatus, the PWM signal is generated by the firmware, the smoothed voltage is generated, and the voltage is supplied to the laser diode 100. 1
Since it must be configured to control the light intensity of 00,
There is a problem that the structure of the laser light amount control circuit becomes complicated. Further, since the capacitors 101 and 102 in the laser light amount control circuit accumulate electric charge and then discharge the electric charge, there is also a problem that the response becomes slow with respect to the fluctuation of the PWM signal. Furthermore, the firmware has to control not only the mechanical control board but also the laser light quantity control circuit.
There is also a problem that the firmware becomes large.

To solve these problems, JP-A-62-1
No. 30578, JP-A No. 1-135082, JP-A-2-206187, JP-A-3-123091,
The technique described in Japanese Patent Laid-Open No. 3-61966 can be used, but these techniques also require a comparator, as in the laser light amount control circuit shown in FIG. If the processing speed of the comparator is increased when the comparator is used, the comparator oscillates. In order to deal with this situation, high-speed firmware must be used and a high-speed CPU must control the comparator.
Such a high-speed CPU is expensive, and using this causes a problem that the cost of the device increases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a recording apparatus capable of controlling the laser light amount at high speed with a simple structure and reducing the cost. I do.

[0015]

To achieve the above object, the present invention provides a laser light amount control circuit for controlling the amount of laser light output to a photosensitive drum based on a horizontal synchronizing signal and an image signal from a mechanical control board. In the recording apparatus, the laser light amount control circuit includes a laser diode that outputs a laser, a D / A converter that converts a digital voltage into an analog voltage and applies the analog voltage to the laser diode, and a laser light amount of the laser diode. The laser diode is turned on and off in response to the image signal output from the mechanical control board after the start-up and the control signal output for a predetermined time before the input of the horizontal synchronizing signal.
A transistor for flip-flop, a photodiode for detecting the light amount of the laser diode and outputting the light amount as a voltage, an A / D converter for converting the output voltage of the photodiode to a digital voltage, and the A / D converter From
Output the difference voltage that is the output voltage of
The first subtraction circuit and the difference voltage from the first subtraction circuit
The difference voltage subtracted from the laser reference voltage is stored in the memory circuit.
The second subtraction circuit for outputting and an OK signal indicating the completion of the rise of the laser light amount when the difference voltage close to the laser reference voltage is input from the second subtraction circuit are sent to the mechanical control board , and the control is performed. above the storage signal in which a signal is outputted from the mechanical control base just prior to OFF
A storage circuit for storing and fixing the difference voltage from the second subtraction circuit and outputting the fixed difference voltage to the D / A converter;
Is provided.

In this recording device , the emitter of the transistor is connected to the output side of the D / A converter, the collector is connected to the anode of the laser diode, and the base is provided with the image signal and the control signal. May be input .

A recording apparatus according to a second aspect of the present invention is a recording apparatus including a laser light amount control circuit for controlling the amount of laser light output to a photosensitive drum based on a horizontal synchronizing signal and an image signal from a mechanical control board. The laser light amount control circuit includes a laser diode for outputting a laser, a D / A converter for converting a digital voltage into an analog voltage and applying the analog voltage to the laser diode, and the mechanical control board after the start of the laser light amount of the laser diode. A transistor for turning on and off the laser diode in response to the image signal output from the device and a control signal output for a predetermined time before the input of the horizontal synchronizing signal;
A photodiode that detects the light amount of the laser diode and outputs the light amount as a voltage, an A / D converter that converts the output voltage of the photodiode into a digital voltage, a laser reference voltage and a reference voltage of the photodiode.
Lasers and subtracting circuit for outputting a difference voltage between a predetermined reference voltage and the output voltage from the A / D converter is the sum of the pressure, the differential voltage is close to the laser reference voltage at the time of input from the subtraction circuit Sends an OK signal indicating the end of the light intensity rise to the mechanical control board, and turns off the control signal.
Immediately before doing so, the difference voltage from the subtraction circuit is stored and fixed by the memory signal output from the mechanical control board,
And a storage circuit for outputting the constant difference voltage to the D / A converter.

[0018]

According to the above recording apparatus, since the output voltage of the photodiode of the laser light quantity control circuit is "0" at the rise of the laser light quantity, the subtraction circuit (first and second subtraction times) is performed.
) , A predetermined reference voltage is output and input to the D / A converter via the storage circuit. Then, the digital voltage of the predetermined reference voltage is converted into an analog voltage and applied to the laser diode.

Then, the laser diode is turned on, and the amount of light is output as a voltage from the photodiode to the first subtraction circuit through the A / D converter.
Is a predetermined reference voltage from the output voltage from the A / D converter.
The difference voltage obtained by subtracting is output to the second subtraction circuit, and the second subtraction circuit
The circuit uses the difference voltage from the first subtraction circuit as the laser reference.
The difference voltage subtracted from the voltage is passed through the memory circuit to the D / A converter
Enter again. When such an action is repeated and a difference voltage close to the laser reference voltage is output from the subtraction circuit, an OK signal is output from the storage circuit to the mechanical control board, and the rise of the laser light amount is completed.

After the laser light amount has been raised,
When the control signal is output from the mechanical control board to the transistor, the transistor is turned on for a predetermined time before the input of the horizontal synchronizing signal, and thereafter, the same operation as at the time of starting is performed. Then, just before the control signal is turned off, a storage signal is output from the mechanical control board to the subtraction circuit, the difference voltage at this time is stored and fixed in the storage circuit, and thereafter, this constant difference voltage is directed to the laser diode. Is output.

In this recording apparatus, the transistor
If the emitter of is connected to the output side of the D / A converter,
Connect the collector to the anode of the laser diode above
And a configuration in which the image signal and the control signal are input to the base
Then, the analog voltage from the D / A converter is input from the emitter of the transistor, and is applied to the laser diode via the collector. Then, the image signal and the control signal from the mechanical control board are input to the base of the transistor.

According to the recording apparatus of the second aspect , the output voltage from the A / D converter is subtracted from the sum of the laser reference voltage and the photodiode reference voltage by the subtraction circuit,
The difference voltage is output to the storage circuit.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. First embodiment. FIG. 1 is a block diagram of a laser light amount control circuit applied to this embodiment, and FIG. 2 is a schematic diagram showing a recording apparatus according to the first embodiment of the present invention. In FIG. 2, reference numeral 1 denotes a housing, in which a mechanical control board 2 and a laser head 3 are provided. A paper supply unit for supplying recording paper 4 to be printed by the laser head 3 is provided in the housing 1.
It is provided at the lower part. The paper feeding unit includes a recording paper cassette 5, a pickup roller 6, an intermediate roller 7, a registration roller 8, and a paper feeding sensor 9.

The recording paper 4 fed by this paper feeding section
A recording unit that prints is provided between the paper feeding unit and the laser head 3. As shown in the figure, this recording unit includes a transfer corotron 10, a charging corotron 11, a photoconductor drum 12, a cleaner 13, an eraser 14, and a fixing device 15.
And a developing device 16.

With this structure, the recording paper 4 in the recording paper cassette 5 is picked up by the pickup roller 6 and conveyed to the intermediate roller 7. And the intermediate roller 7
When the recording paper 4 conveyed by is detected by the paper feed sensor 9,
The tip is moved to the registration roller 8. And
The recording paper 4 is conveyed from the registration roller 8 to the conveying portion in accordance with the transfer timing position of the toner image on the photosensitive drum 12. Then, the laser of the laser head 3 is output according to the image of the dot of the image signal sent from the host computer (not shown) to the laser head 3 via the mechanical control board 2, and the electrostatic latent image is formed on the photosensitive drum 12. An image is formed. This electrostatic latent image is converted into a toner image by the developing device 16.

Then, the recording paper 4 is sent out from the registration roller 8 at the transfer timing of the toner image, and the toner image on the photosensitive drum 12 is transferred onto the recording paper 4 by the transfer corotron 10. The recording paper 4 that has been subjected to this transfer processing is sent from the conveying section to the fixing device 15, and is fixed by the fixing device 15. Thereafter, the residual toner on the photosensitive drum 12 is scraped off by the cleaner 13, the residual voltage of the photosensitive drum 12 is erased by the eraser 14, and the surface voltage of the photosensitive drum 12 is set to 0V.

In the laser head 3 of such a recording apparatus, a laser light amount control circuit 20, which is a main part of the present embodiment, is provided. The laser light amount control circuit 20 has the configuration shown in FIG. In FIG. 1, reference numeral 21 is a D / A converter that converts a digital signal into an analog signal, and an enable signal E from the mechanical control board 2 is turned on.
It is supposed to work when.

The emitter of the transistor 22 is connected to the output side of the D / A converter 21. The base of the transistor 22 is connected to the mechanical control board 2, and the control signal C or the image signal D from the mechanical control board 2 is input. Control signal C
Is the horizontal sync signal H on the mechanical control board 2.
Is input to the base of the transistor 22 for a time length of 100 μs before the laser light of the laser diode 23 hits the photosensitive drum 12.

The collector side of such a transistor 22 is connected to the anode of the laser diode 23 via a resistor. The laser diode 23 is connected to the anode of the photodiode 24 with its cathode grounded, and the laser diode 23 and the photodiode 24 are arranged opposite to each other.

The cathode of the photodiode 24 is connected to an A / D converter 25 which converts an analog signal into a digital signal. Subtraction circuits 26 and 28 as first and second subtraction circuits are connected in series to the output side of the A / D converter 25.

The subtraction circuit 26 is connected to a reference voltage generation circuit 27 for generating a reference voltage A, and subtracts the reference voltage A from the reference voltage generation circuit 27 from the output voltage B from the A / D converter 25. And subtract the difference voltage B-A from the subtraction circuit 2
8 is provided.

The subtraction circuit 28 is connected to a laser reference voltage generation circuit 29 which generates a laser reference voltage A'of the laser diode 23. The laser reference voltage generation circuit 2
9 from the laser reference voltage A ′, the difference voltage B− of the subtraction circuit 26
A has a function of subtracting A and outputting a difference voltage A ′ − (BA). Further, the subtraction circuit 28 outputs the OK signal K to the mechanical control board 2 when the output difference voltage A ′ − (BA) is in an oscillation state that gradually rises and falls around the laser reference voltage A ′. Has a function.
A storage circuit 30 is connected to the output side of the subtraction circuit 28.

The storage circuit 30 is a circuit for storing and holding the difference voltage A '-(BA) from the subtraction circuit 28. When the storage signal M from the mechanical control board 2 is input, the storage circuit 30 stores the difference voltage A'-(BA). By operating the holding function, the differential voltage A '-(B-
A) is held and fixed, and at the other time points, the differential voltage A′−
It has a function of outputting (BA) to the D / A converter 21 without storing it.

Next, the operation of the laser light amount control circuit 20 will be described. First, the laser light amount raising operation of the laser diode 23 will be described. Initially, since the laser diode 23 is not turned on, the output voltage B of the photodiode 24 is "0". Therefore, the difference voltage B-A output from the subtraction circuit 26 becomes the reference voltage A itself, and as a result, the difference voltage A '-(B-A) output from the subtraction circuit 28 becomes A' + A. At this time, since the storage signal M is not input to the subtraction circuit 28, the difference voltage A ′ + A passes through the subtraction circuit 28 and passes through the D / A converter 21.
Leads to.

Then, O from the mechanical control board 2
When the N enable signal E is input to the D / A converter 21 and the operation for raising the laser light amount is started, the D / A converter 21 operates and the difference voltage A ′ + from the subtraction circuit 28.
A is converted into analog, and an analog voltage corresponding to the difference voltage A ′ + A is applied to the emitter side of the transistor 22. As a result, the transistor 22 is turned on,
A current flows through the laser diode 23, the laser light amount of the laser diode 23 gradually increases, and the output voltage B of the photodiode 24 gradually increases from “0”.

As the output voltage B rises, the subtraction circuit 2
The differential voltage B-A of 6 decreases, and the differential voltage A '-(BA) from the subtraction circuit 28 gradually approaches the laser reference voltage A'. As a result, the difference voltage A '-(B-A) output from the subtraction circuit 28 gradually rises and falls around the laser reference voltage A'. When this state is reached, the density of the image printed by the laser light amount of the laser diode 23 can be substantially constant, so the OK signal K is output from the subtraction circuit 28 to the mechanical control board 2.

In the mechanical control board 2, the OK signal K
If it is detected, the internal firmware F / W determines that printing on the recording paper 4 (see FIG. 1) is possible and terminates the laser starting operation of the laser diode 23.
In this way, when the start-up operation is completed, the mechanical control board 2 inputs the horizontal synchronizing signal H and the image signal D from the host computer (not shown), and shifts to the printing operation.

Next, the laser light amount adjusting operation during the printing operation will be described. In this laser light amount adjusting operation, after stabilizing the laser light amount based on the horizontal synchronizing signal H, the laser light amount is kept constant based on the image signal D.

That is, in the mechanical control board 2, the control signal C having a time length of 100 μs before the horizontal synchronizing signal H is inputted and the laser beam of the laser diode 23 does not hit the photosensitive drum 12 is applied to the transistor 22.
Is input to the base of the memory circuit 30 and the transistor 22 is turned on while the memory circuit 30 is turned on.
As a result, the same operation as the above startup operation is performed,
The laser light quantity of the laser diode 23 is stabilized.

Then, immediately before the control signal C is turned off, the storage signal M is output from the mechanical control board 2 to the storage circuit 30, and the difference voltage A '-(BA) at that time is held and fixed in the storage circuit 30. You. Thereafter, when the image signal D is output to the base of the transistor 22, the held and fixed difference voltage A ′-(BA) is applied to the laser diode 23 via the D / A converter 21 and the transistor 22. And
After that, a constant voltage is always applied to the laser diode 23,
A laser with a constant light amount is output from the laser diode 23. At this time, the output voltage B of the photodiode 24 is input to the subtraction circuit 26 via the A / D converter 25, and the output voltage from the subtraction circuit 28 changes, but the storage circuit 30
Are held and fixed at the constant difference voltage A '-(BA), and the laser light amount of the laser diode 23 does not change.

As described above, according to the present embodiment, the D / A converter 21, the transistor 22, the laser diode 23,
Photodiode 24, A / D converter 25, subtraction circuit 2
6, the laser light amount control circuit 20 can be configured with a simple structure of the subtraction circuit 28 and the storage circuit 30. Also,
The control of the laser light amount of the laser diode 23 is performed by the above D / A.
Since the control is performed by hardware such as the converter 21, it is possible to speed up the control. That is, firmware F
/ W is used for controlling the CPU and the like in the mechanical control board 2 and is hardly used for controlling the laser light amount control circuit 20, so that the laser light amount control circuit 20 has little dependence on the firmware F / W. As a result, the control process can be performed at extremely high speed.

Further, since the dependence of the laser light amount control circuit 20 on the firmware F / W is small, the firmware F / W can be made small. Further, since the laser diode 100 is controlled by using the digital signal of the D / A converter without using the comparator, the above-mentioned Japanese Patent Laid-Open No.
High-speed processing can be executed without specially providing a high-speed and expensive CPU at the time of high-speed processing as in the technology described in Japanese Patent Application Laid-Open No. 2-130578, and as a result, the cost can be kept low as compared with the above-mentioned technology. Can be.

Second embodiment. A second embodiment of the present invention is shown in FIG. In the laser light amount control circuit of this embodiment, the laser diode 23 and the photodiode 24 are not grounded, and the subtraction circuits 26 and 2 are not connected.
The subtraction circuit 31 is used in place of 8, and the reference voltage generation circuit 27
The difference from the first embodiment is that a laser reference voltage generating circuit 32 is used instead of the laser reference voltage generating circuit 29.

The laser reference voltage generating circuit 32 is a circuit for generating a reference voltage A '+ B which is the sum of the laser reference voltage A'of the laser diode 23 and the reference voltage B of the photodiode 24. The subtraction circuit 31 detects the photodiode 24 from the reference voltage A ′ + B of the laser reference voltage generation circuit 32.
Has a function of subtracting the output voltage A of the above and outputting the difference voltage A ′ + B−A to the memory circuit 30.

With this configuration, the laser diode 23
Photodiode 2 when the laser light amount of
4 is “0”, and the difference voltage A ′ + BA output from the subtraction circuit 31 becomes the reference voltage A ′ + B.

Then, O from the mechanical control board 2
When the N enable signal E is input to the D / A converter 21 and the operation for raising the laser light amount is started, the D / A converter 21 operates and the difference voltage A ′ + from the subtraction circuit 28.
An analog voltage corresponding to B is applied to the emitter side of the transistor 22, the transistor 22 is turned on, and a current flows through the laser diode 23. As a result, the output voltage A of the photodiode 24 gradually rises from "0", the voltage BA portion of the subtraction circuit 31 decreases accordingly, and the difference voltage A '+ BA that is output gradually. It approaches the laser reference voltage A '. As a result, the difference voltage A ′ + B−A output from the subtraction circuit 28 enters an oscillation state in which the difference voltage A ′ + B−A gently rises and falls around the laser reference voltage A ′, and the subtraction circuit 31 outputs an OK signal K to the mechanical control board 2. Is done.

Then, the OK signal K is detected by the mechanical control board 2, and the laser starting operation of the laser diode 23 is completed. After the start-up operation is completed, the laser light amount is stabilized based on the horizontal synchronizing signal H, and then the laser light amount is kept constant based on the image signal D.

That is, in the mechanical control board 2, a control signal C having a time length of 100 μs before the horizontal synchronizing signal H is inputted and the laser beam of the laser diode 23 does not hit the photosensitive drum 12 is applied to the transistor 22.
To the base of the memory circuit 3 to turn on the transistor 22 during that time, and the memory circuit 3 without inputting the memory signal M.
0 is set to a through state. Accordingly, the same operation as the above-described start-up operation is performed, and the laser light amount of the laser diode 23 is stabilized.

The storage signal M is output from the mechanical control board 2 to the storage circuit 30 immediately before the control signal C is turned off, and the difference voltage A '+ BA at that time is stored in the storage circuit 30.
Is held and fixed. After that, when the image signal D is output to the base of the transistor 22, the held and fixed difference voltage A ′ + B−A is applied to the D / A converter 21 and the transistor 2.
The laser diode 23 is applied to the laser diode 23 via 2 and then a constant voltage is always applied to the laser diode 23 so that the laser diode 23 outputs a laser having a constant light amount. At this time, the output voltage A of the photodiode 24 is input to the subtraction circuit 26 via the A / D converter 25, and the subtraction circuit 2
Although the output voltage from 8 fluctuates, the voltage inside the memory circuit 30 is held and fixed at the constant difference voltage A ′ + BA, and the laser light amount of the laser diode 23 does not change.
The other configuration, operation, and effect are the same as those of the first embodiment, and the description is omitted.

[0050]

As described above, according to the recording apparatus of the present invention, the D / A converter, the transistor, the laser diode,
A laser light amount control circuit is configured with a simple structure including a photodiode, an A / D converter, a subtraction circuit, a subtraction circuit, and a storage circuit, and the laser light amount control of the laser diode is controlled by the D / A.
Since the control is performed by hardware such as a converter, it is possible to speed up the control. That is, since the firmware is hardly used for controlling the laser light amount control circuit, the dependence of the laser light amount control circuit on the firmware is small, and as a result, there is an effect that the control processing can be performed extremely fast.

Further, since the dependence of the laser light amount control circuit on the firmware is small, there is an effect that the firmware can be downsized. Further, since the laser diode is controlled by using the digital signal of the converter without using the comparator, the above-mentioned JP-A-62-1305 is used.
High-speed processing can be executed without specially providing a high-speed expensive CPU at the time of high-speed processing as in the technology described in Japanese Patent Application Publication No. 78-78, etc. This has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram of a laser light amount control circuit applied to a recording apparatus according to a first embodiment of the invention.

FIG. 2 is a schematic diagram of a recording apparatus according to a first embodiment.

FIG. 3 is a block diagram of a laser light amount control circuit applied to a recording apparatus according to a second embodiment of the invention.

FIG. 4 is a circuit diagram of a laser light amount control circuit applied to a conventional recording apparatus.

5A and 5B are operation time charts of a conventional example, FIG. 5A shows a PWM signal, and FIG. 5B shows a base voltage of the transistor 103.

[Explanation of symbols]

 Reference Signs List 21 D / A converter 23 Laser diode 2 Mechanical control board 22 Transistor 25 A / D converter 24 Photodiode 26 Subtraction circuit 28 Subtraction circuit 30 Storage circuit

Claims (2)

(57) [Claims] 1. A recording apparatus comprising a laser light amount control circuit for controlling a laser light amount output to a photosensitive drum based on a horizontal synchronization signal and an image signal from a mechanical control board, wherein the laser light amount control circuit comprises: A D / A converter for converting a digital voltage into an analog voltage and applying the same to the laser diode; and the image signal output from the mechanical control board after the start of the laser light amount of the laser diode And a control signal output for a predetermined time before the input of the horizontal synchronizing signal, to turn on / off the laser diode.
A transistor to detect the light intensity of the laser diode, a photodiode which outputs the light amount as a voltage, an A / D converter for converting the output voltage of the photodiode into a digital voltage, from the A / D converter Output voltage
The first subtraction that outputs the difference voltage obtained by subtracting the predetermined reference voltage from
Circuit and the difference voltage from this first subtraction circuit to the laser reference voltage
Second subtraction for outputting the difference voltage subtracted from
Circuit and an OK signal indicating the end of the laser light amount rise at the time when a difference voltage close to the laser reference voltage is input from the second subtraction circuit, and immediately before the control signal is turned off. A storage circuit that stores and fixes the differential voltage from the second subtraction circuit according to a storage signal output from the mechanical control board, and outputs the constant differential voltage to the D / A converter. Recording device. 2. A recording apparatus comprising a laser light amount control circuit for controlling the laser light amount output to a photosensitive drum based on a horizontal synchronizing signal and an image signal from a mechanical control board, wherein the laser light amount control circuit is a laser A D / A converter for converting a digital voltage into an analog voltage and applying the same to the laser diode; and the image signal output from the mechanical control board after the start of the laser light amount of the laser diode And a control signal output for a predetermined time before the input of the horizontal synchronizing signal, to turn on / off the laser diode.
Transistor, a photodiode that detects the light amount of the laser diode and outputs the light amount as a voltage, an A / D converter that converts the output voltage of the photodiode into a digital voltage, a laser reference voltage and the photodiode
A predetermined reference voltage which is the sum of the reference voltage of the ion and the above A
/ A subtracting circuit for outputting a difference voltage between the output voltage from the D converter, the mechanism control OK signal indicating the amount of laser light launching end of the differential voltage is close to the laser reference voltage at the time of input from the subtraction circuit The difference voltage from the subtraction circuit is stored and fixed by the memory signal output from the mechanical control board immediately before the control signal is turned off, and this constant difference voltage is stored in the D / A converter. A recording device comprising: a storage circuit for outputting.