JPH11348342A - Method and apparatus for controlling light quantity of laser for image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a light quantity of multibeams by a smaller number of control signals than in the prior art in an image formation apparatus using a multibeam laser, and a low-cost apparatus having the number of cables and connector pins reduced by the method. SOLUTION: In using two laser diodes LDA and LDB, a light quantity of each laser diode LDA and LDB can be controlled by a combination of signal levels of three control signal lines of a LONA signal, a LONB signal both connected to a laser drive circuit from an engine controller and a common S/H signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic process, and more particularly to a laser light amount control in an image forming apparatus using a multi-beam laser as a light source for image exposure.

[0002]

2. Description of the Related Art Conventionally, a laser printer has been known as this type of image forming apparatus.

In such an image forming apparatus using an electrophotographic process, when a multi-beam laser is used as a light source for image exposure, a plurality of laser driver ICs for single use are used and each laser driver IC is individually controlled. hand,
The laser light quantity adjustment and the laser switching operation are performed.

An example of a laser printer will be described with reference to FIGS.

In FIG. 3, a video controller 202
Converts the image data from the host computer 201 into a video signal for driving a laser,
Send to The laser drive circuit 204 is controlled by the engine controller 203. Laser drive circuit 204
Turns on the laser diode 205 according to the video signal.
It turns off and irradiates a laser beam toward the polygon mirror on the scanner motor 206. The polygon mirror reflects the laser beam while rotating, and scans in the horizontal direction at a constant speed. The laser beam passes through the fθ lens 207, is reflected by the return mirror 208, is irradiated on the photosensitive drum 209, and an electrostatic latent image is formed.

FIG. 10 is a diagram illustrating details of the laser drive circuit 204 and the laser diode 205 shown in FIG. In FIG. 10, a laser diode 306 includes:
Two laser diodes LDA303 and LDB3 inside
04 and one photodiode 305 are arranged. The LDA 303 is controlled by a laser driver A301 which is a laser driving IC, and the LDB 304 is controlled by a laser driver B302. The control signal lines 307 and 308 of the laser driver A of FIG. 10 connected to the laser drive circuit 204 from the engine controller 203 shown in FIG. 3 are a LONA signal and an S / HA signal, respectively. Signal lines 309 and 310 are a LONB signal and an S / HB signal, respectively.

Laser driver A and laser driver B
Is used as a laser diode light control means.
Although a hold circuit is provided, details thereof will be described.

Although only the laser driver A301 will be described, the same applies to the laser driver B302.

The LONA signal 307 is a laser diode L
A signal for forcibly causing the DA 303 to emit light. When the signal level is low (hereinafter, referred to as L level), the laser switching circuit 3 inside the laser driver A301
When the signal level is high (hereinafter referred to as H level), the laser switching circuit 311 is turned off to turn off the laser diode.

The S / HA signal 308 is a laser driver A
This signal is used to switch between the sample operation and the hold operation of the internal sample and hold circuit.
At the level, the switch 31 of the sample and hold circuit
2 is turned on to perform the sampling operation. When the signal level is at the H level, the switch 312 is turned off to perform the hold operation.

Next, a description will be given of a sample operation. During the sample operation, that is, when the switch 312 is turned on, the PD voltage generated by the output current of the photodiode 305 flowing through the variable resistor 313 and the reference voltage Vref
The voltage Vr obtained by dividing the voltage by a resistor is
When the Vr voltage is higher than the PD voltage, the charge / discharge circuit 315 outputs
When the Vr voltage is smaller than the PD voltage, the charge of the hold capacitor 316 is discharged from the charge / discharge circuit 315. Laser drive current source 31
Reference numeral 7 has a function of flowing a laser drive current proportional to the voltage of the hold capacitor 316. Therefore, by always charging / discharging the hold capacitor during the sample operation and adjusting the drive current of the laser diode 303,
Control is performed so that the output current of the photodiode 305 becomes a constant value. Since the output current of the photodiode is proportional to the light amount of the laser diode, the laser light amount is also controlled to a constant value.

Next, a description will be given of a hold operation. During the hold operation, that is, when the switch 312 is turned off, the hold capacitor 316 and the charging / discharging circuit 315 are separated, so that a constant voltage is held in the hold capacitor. Therefore, the drive current of the LDA 303 is also kept at a constant value.

It is desirable that the image light source of the laser printer has a constant light amount.

Since the laser printer forms an image by turning on and off the laser, in an image forming apparatus using a laser driver utilizing the above-mentioned sample and hold circuit, the scanning position of the laser during image printing is within the image area. , The sample operation cannot be performed. This is because the laser diode must always emit light in order to perform the sample operation. Therefore, the hold operation is performed during image printing. However, if the hold operation is continued, a phenomenon occurs in which the light amount of the laser diode decreases, and the light amount of the laser diode fluctuates due to a leak current of the holding capacitor from the laser driving current source. Therefore, when the laser scanning position is in the non-image area, a sampling operation is performed to control the amount of light of the laser diode to return to a constant value.

FIG. 11 is a flowchart showing this process.
Description will be made based on the timing chart shown in FIG. 12 and the explanatory diagram of FIG. Video controller 202 is host 2
01, the video controller 202 instructs the engine controller 203 to perform a printing operation.
3 starts the printing operation (A1).

First, the scanner motor is started (A2),
It is detected whether the scanning position of the laser beam is in the non-image area (A3). This is in a non-image area on the laser beam scanning path, and is a beam detection (hereinafter, referred to as BD) sensor 211 for detecting an image writing position timing in the horizontal direction.
It can be detected from the timing of the BD signal generated when the laser beam scans above.

When the BD signal is detected and the laser scanning position is in the non-image area, first, the LONA signal is set to L level and LD
A is forced to emit light (A4), and then the S / HA signal is changed to L
The level is sampled for LDA (A5). After performing LDA sampling for a period of time t ₁ (A6), S
/ H A signal is set to H level to hold LDA (A
7) Then, the LNA signal is set to the H level to turn off the LDA (A8). LDA is off to from time t after ₂ (A9), in order to sample the operation of the LDB, in turn,
The same control as LDA is performed (A10 to A14). The above control is repeated until the image data transmitted from the host computer is completed (A15).
After all the image data is completed, the scanner motor is turned off (A16), and the printing operation is completed (A17).

[0018]

In the prior art, the number of forced emission signals and the number of sample-and-hold signals required for the number of laser diodes are required.
As the number of pins increases, the increase in cost due to the increase in the number of pins of cables and connectors and the number of pins of ICs and laser drivers cannot be avoided.

An object of the present invention is to provide a low-cost image forming apparatus by reducing the cost of a connector, a cable, a laser driver, and the like by reducing the amount of multi-beam light control signals in the image forming apparatus. is there.

[0020]

In order to achieve the above object, a method for controlling the amount of laser light of an image forming apparatus according to the present invention comprises:
A method of controlling the light amount of an exposure laser of an image forming apparatus, wherein when a video controller receives a print command from a host computer, the video controller instructs an engine controller to perform a printing operation,
A step in which the engine controller starts a printing operation, a step in which the scanner motor is activated, the number of revolutions of the scanner motor becomes constant, and a step in which the scanner motor becomes scanner ready; Is set to a low level to forcibly emit light from the laser diode A, and a laser beam is scanned over the sensor by a beam detection sensor which is arranged in a non-image area on the laser beam scanning path and detects a timing of writing an image in a horizontal direction. Detecting the output of a beam detection signal, which is a horizontal synchronization signal generated when the laser diode A is output, and turning off the laser diode A by setting the forced emission signal of the laser A to a high level after detecting the beam detection signal. ,
After a certain period of time from the detection of the beam detection signal, the forced emission signal of the laser A is set to a low level to force the laser diode A to emit light. Then, the sample hold signal is set to a low level, and the sample hold A signal is set to a low level. Performing a sample operation of the diode A; and, after performing the sample operation of the laser diode A, setting the sample hold signal to a high level, setting the sample hold A signal to a high level to hold the laser diode A; Turning off the laser diode A by setting the forced emission signal to a high level;
After turning off the laser diode A, the forced emission signal of the laser A is set to the low level to forcibly emit the laser diode A. When the beam detection signal is detected, the forced emission signal of the laser A is set to the high level and the laser diode A is turned on. And turning off the forced emission signal of the laser B after a certain time from the detection of the beam detection signal,
After the laser diode B is forced to emit light, the sample-and-hold signal is set to a low level, the sample-and-hold B signal is set to a low level, and the sample operation of the laser diode B is performed. Raising the sample and hold signal to a high level, raising the sample and hold B signal to a high level, and holding the laser diode B; turning on the laser B forcible emission signal to a high level to turn off the laser diode B; Thereafter, when image data still remains and image formation is necessary, the method includes a step of forcing the laser diode A to emit light again, and a step of turning off the scanner motor and terminating the printing operation when the image data formation is completed.

Further, the laser light amount control device of the image forming apparatus according to the present invention is connected to each laser drive unit from the laser drive control unit, and has the same number of first laser diodes as the number of laser diodes.
A control signal line, and one second control signal line commonly connected to each of the laser drive units from the laser drive control unit, and a light amount control of the laser diode is performed by a combination of signal levels of the control signal lines. Means for performing the following.

Further, a first control signal which is a laser forcible light emission signal having a function of forcibly emitting light from a laser diode, and the laser driving means is provided only when the first control signal is at a signal level in a laser emission state. An embodiment having a second control signal having a function of switching between the sample operation and the hold operation is also one embodiment.

When a laser beam is scanned in a non-image area on the laser beam scanning path, a horizontal synchronizing signal for detecting a horizontal image writing timing is output, and the laser scanning position is determined from the horizontal synchronizing signal. In one embodiment, the apparatus includes means for detecting the presence of a non-image area and performing a laser sampling operation in the non-image area.

In one embodiment of the present invention, there is provided a means for simultaneously performing a sampling operation at the time of laser emission for detecting the horizontal synchronizing signal.

Also, a preferred embodiment of the present invention has a plurality of laser driving means formed as a one-chip IC.

[0026]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 5 is a block diagram showing a laser drive circuit according to the first embodiment of the present invention.

In FIG. 5, two laser diodes LDA103 and LDB1 are provided inside a laser diode 106.
04 and one photodiode 105 are arranged. A laser diode LDA103 (hereinafter referred to as LDA) is a laser driver A101 which is a laser driving IC.
And the laser diode LDB104 (hereinafter referred to as LD
B) is driven by a laser driver B102.

Control signal 10 of laser driver A101
Reference numerals 7 and 108 denote a LONA signal and an S / HA signal, respectively, and control signals 109 and 110 for the laser driver B102.
Represents a LONB signal and an S / HB signal, respectively. The laser driver A101 and the laser driver B102 are three signal lines from the engine controller at distant positions, namely, the LONA signal 107, the LONB signal 109, and the S /
It is controlled by the H signal 120. Logic circuits 118 and 119 are connected to these signal lines.

As shown in FIG. 2, the S / HA signal is converted by the logic circuit 118 into the LONA signal and the S / H signal.
When both of the signal levels are at the L level, the signal becomes the L level signal. At this time, the sampling operation of the laser diode LDA is performed.

Similarly, the S / H B signal is applied to the logic circuit 1
19, when the signal levels of the LONB signal and the S / H signal 120 are both at L level, the signal becomes an L level signal.
The sample operation of B is performed.

Next, the state of light quantity control according to the present embodiment is shown in FIG.
, The timing chart shown in FIG. 4, and the configuration explanatory view of the laser printer shown in FIG.

When the video controller 202 receives a print command from the host computer 201, the video controller 202 instructs the engine controller 203 to perform a printing operation, and the engine controller 203 starts the printing operation (B1).

First, the scanner motor is started (B2),
It waits until the rotation speed of the scanner motor becomes constant and the scanner becomes ready (B3). After the scanner becomes ready, the LONA signal is set to the L level, and the LDA is forced to emit light (B4).

In a non-image area on the laser beam scanning path, a BD sensor 211 as an optical sensor for detecting a horizontal image writing position timing is arranged. It is detected that a BD signal which is a synchronization signal is output (B5). After detecting the BD signal, set the LONA signal to H level and
Is turned off (B6).

Next, first, in order to perform the sampling operation of the LDA, at time t ₁ (B7) after detecting the BD signal,
The LONA signal is set to L level and the LDA is forcibly emitted (B
8) Then, the S / H signal is set to L level (B9). At this time, since both the LONA signal and the S / H signal are at the L level, as shown in FIG.
The S / HA signal, which is the control signal of No. 1, is at the L level,
An LDA sampling operation is performed. After performing the LDA sampling operation for t ₂ time (B10), the S / H signal is changed to H level.
By setting the S / HA signal to H level, the LDA is held (B11), and the LONA signal is set to H level to turn off the LDA (B12).

The hatched area in FIG. 4 is an image area.
During this time, the laser cannot be forcibly emitted. T ₃ hours after turning off the LDA (B13), in order to detect the next BD signal, forcibly emit LDA and the LONA signal to L level (B14). When a BD signal is detected (B1
5) The LNA signal is set to the H level to turn off the LDA (B16).

Next, in order to perform the LDB sampling operation,
In addition, t from BD signal detection₁ After an hour (B17), LON
The B signal is set to the L level to force the LDB to emit light (B1
8) Then, the S / H signal is set to L level (B19).
At this time, both the LONB signal and the S / H signal are at L level.
Therefore, as shown in FIG.
The S / H B signal which is the control signal of the L.02 signal becomes L level.
Thus, the LDB sampling operation is performed. t_Two Time LD
After performing the sample operation of B (B20), the S / H signal
To the H level, the S / H B signal to the H level, and LD
B is held (B21), and the LONB signal is
The LDB is turned off (B22). t _Three Time elapsed
Later, if image data still remains and image formation is required
In this case, LDA is forcibly issued again to detect the next BD signal.
Light (B4).

Thereafter, the above operation is repeated until the image data is completed. When the image data is completed (B24), the scanner motor is turned off and the printing operation is completed (B2).
6).

The laser driving means switches between a sampling operation for controlling the output current of the photodiode to a constant value and a holding operation for holding the current value supplied to the laser diode constant. In the hold circuit, the first control signal is a laser forcible emission signal having a function of forcibly emitting light from the laser diode, and the second control signal is a signal level when the first control signal is in the laser emission state. It is a signal having a function of switching the laser driving means to one of a sampling operation and a holding operation only at a certain time.

As described above, in the present embodiment, the light quantity control of the two laser diodes LDA and LDB is controlled by the three signals of the LONA signal, LONB signal and S / H signal connected from the engine controller to the laser drive circuit.
This can be performed by using the control signal lines.

In this embodiment, the case of two laser diodes has been described, but the present invention is not limited to the case of two laser diodes. For example, in the case of an image forming apparatus using four laser diodes, it is possible to control the light amount of four laser diodes with a total of five signal lines of four LON signals and one S / H signal. Needless to say.

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

This embodiment is different from the first embodiment in the sequence of the laser diode sampling operation. This will be described with reference to a flowchart shown in FIG. 7 and a timing chart shown in FIG.

When the video controller 202 receives a print command from the host computer 201, the video controller 202 instructs the engine controller 203 to perform a printing operation, and the engine controller 203 starts the printing operation (C1).

First, the scanner motor is started (C2),
Wait until the number of rotations of the scanner motor becomes constant and the scanner becomes ready (C3). After becoming a scanner ready,
The LONA signal is set to the L level, the LDA is forced to emit light (C4), and the S / HA signal is set to the L level (C5).
At this time, since both the LONA signal and the S / H signal are at L level, the control signal S /
The HA signal becomes L level, and the LDA sampling operation is performed.

When the BD signal is detected (C
6) By setting the S / H signal to the H level, the S / H
The A signal becomes H level and holds LDA (C
7) Then, the LDA signal is set to the H level to turn off the LDA (C8).

Next, to perform a sample operation of the LDB, t ₁ hour after turning off the LDA in (C9), LO
The NB signal is set to the L level to force the LDB to emit light (C1
0) Then, the S / H signal is set to L level (C11).
At this time, since both the LONB signal and the S / H signal are at the L level, as shown in FIG.
The S / H B signal, which is the control signal 02, goes low, and the LDB sampling operation is performed. t ₂ hours LDB
After the sampling operation (C12), the S / H signal is set to the H level, the S / HB signal is set to the H level, the LDB is held (C13), and the LDB is turned off (C14). t ₃ hours after (C15), the image data are still left, when the image forming is required, in order to detect the next BD signal, forcibly emit light again LDA (C4).

Thereafter, the above operation is repeated until the image data is completed. When the image data is completed (C16), the scanner motor is turned off (C17), and the printing operation is completed (C18).

As described above, in the second embodiment, the sampling operation of LDA and LDB can be performed within one period of the BD signal, so that the hold time can be shortened and the light quantity fluctuation of the laser diode can be reduced. Can be reduced.

As described above, when the laser beam is scanned in the non-image area on the laser beam scanning path, a horizontal synchronization signal for detecting a horizontal image writing timing is output. It detects that the scanning position is in the non-image area, performs a laser sampling operation in the non-image area, and also performs a sampling operation at the same time as laser emission for detecting the horizontal synchronization signal. Processing can be performed with fewer control signal lines, for example, two for laser diode emission and one for sample hold.

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

FIG. 8 is a block diagram showing the configuration of the present embodiment. In this figure, parts corresponding to those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. I do.

In this embodiment, the logic circuits 118, 119
Are different from those of the first embodiment in that they are built in the laser drivers 101 and 102, respectively.

Since the logic circuits 118 and 119 have a simple configuration, they can be easily mounted inside the laser driver IC, and the cost of the laser driver IC itself is small. By doing so, the laser drive circuit has no logic circuit in the configuration, so that the space is free and the substrate size can be reduced, so that the cost can be reduced.

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

FIG. 9 is a block diagram showing the structure of the present embodiment. In this figure, parts corresponding to those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. Is omitted.

In this embodiment, the laser drivers 101, 10
2 differs from the first embodiment in that it is a one-chip IC. By doing so, the S / H
The two laser driver control signals of the A signal and the S / H B signal become one S / H signal, and the total number of pins of the IC can be reduced.

In addition to the S / H signal, each driver IC such as an input terminal of a photodiode for monitoring the light amount, a power supply terminal, a ground terminal (not shown), etc.
Terminals that were required one by one can be shared,
The total cost of the driver IC can be reduced.

Next, the control program is read from the recording medium 213 to the host computer, controls the operation of the program processing, and executes the following processing. That is, when the video controller receives a print command from the host computer, the video controller instructs the engine controller to perform a printing operation, the engine controller starts the printing operation, activates the scanner motor, and rotates the scanner motor. The number is constant,
A process of waiting until the scanner motor becomes scanner ready, a process of setting the forced emission signal of the laser A to a low level after the scanner becomes ready and forcing the laser diode A to emit light, and a process of causing the laser diode A to emit a non-image area on the laser light scanning path. A beam detection sensor disposed to detect a horizontal image writing position timing, a process for detecting that a beam detection signal, which is a horizontal synchronization signal generated when a laser beam scans the sensor, is output; After detecting the detection signal, the process of turning off the laser diode A by setting the forced emission signal of the laser A to a high level, and changing the forced emission signal of the laser A to a low level after a certain time from the detection of the beam detection signal. The laser diode A is forced to emit light, and then the sample-and-hold signal is set to a low level to lower the sample-and-hold A signal. And performing a sampling operation of the laser diode A, performing a sampling operation of the laser diode A, setting the sample hold signal to a high level after performing the sampling operation of the laser diode A, setting the sample hold A signal to a high level, and holding the laser diode A. A process of turning off the laser diode A by setting the forced emission signal of the laser A to a high level, and forcing the laser diode A to a low level by setting the forced emission signal of the laser A to a low level after a certain period of time after the laser diode A is turned off. And the process of turning off the laser diode A by setting the forced emission signal of the laser A to a high level when the beam detection signal is detected, and then forcing the emission of the laser B a certain time after the detection of the beam detection signal. When the signal is low, the laser diode B is forced to emit light, and then the sample-and-hold signal is Is set to the low level, the sample-and-hold B signal is set to the low level, and the sample operation of the laser diode B is performed. After the sample operation of the laser diode B is performed, the sample-and-hold signal is set to the high level and the sample-and-hold B signal is set. To a high level to hold the laser diode B, a process to turn off the laser diode B by setting the forced emission signal of the laser B to a high level, and after a certain period of time, image data still remains and image formation is necessary. In such a case, the process for forcibly emitting the laser diode A again and the process for turning off the scanner motor when the image data formation is completed and terminating the printing operation are executed.

[0061]

As described above, according to the present invention,
In an image forming apparatus using a multi-beam laser, it is possible to reduce the number of multi-beam light quantity control signals, so that the cost of connectors, cables, laser drivers, and the like can be reduced, and an inexpensive image forming apparatus can be provided. .

Also, LDA and LD within one cycle of the BD signal
Since the sample operation of B can be performed, the hold time can be shortened, and the light quantity fluctuation of the laser diode can be reduced.

Further, by using a one-chip IC for a plurality of laser drivers, the configuration of the driver IC can be simplified and the total cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing laser light quantity control according to a first embodiment of the present invention.

FIG. 2 is a truth table of a laser control signal.

FIG. 3 is a diagram illustrating the configuration of a laser printer.

FIG. 4 is a timing chart showing laser light quantity control according to the first embodiment;

FIG. 5 is a configuration diagram of a laser drive circuit according to the first embodiment of the present invention.

FIG. 6 is a timing chart showing laser light amount control according to a second embodiment.

FIG. 7 is a flowchart illustrating laser light amount control according to a second embodiment.

FIG. 8 is a configuration diagram of a laser drive circuit according to a third embodiment.

FIG. 9 is a configuration diagram of a laser drive circuit according to a fourth embodiment.

FIG. 10 is a configuration diagram of a conventional laser drive circuit.

FIG. 11 is a flowchart illustrating a conventional laser light amount control.

FIG. 12 is a timing chart showing a conventional laser light amount control.

[Explanation of symbols]

101, 301 Laser driver A 102, 302 Laser driver B 103, 303 Laser diode (LDA) 104, 304 Laser diode (LDB) 105, 305 Photodiode 106, 306 Laser diode 107, 307 Laser A forced emission signal (LON)
A) 108, 308 Sample hold A signal (S / H
A) 109, 309 Laser B forced emission signal (LON
B) 110, 310 Sample hold B signal (S / H
B) 111, 311 Laser switching circuit 112, 312 Switch 113, 313 Variable resistor 114, 314 Comparator 115, 315 Charge / discharge circuit 116, 316 Hold capacitor 117, 317 Laser drive current source 118 Logic circuit 119 Logic circuit 120 Sample / hold Circuit (S / H) 201 Host computer 202 Video controller 203 Engine controller 204 Laser drive circuit 205 Laser diode 206 Scanner motor 207 fθ lens 208 Folding mirror 209 Photosensitive drum 211 Beam detection (BD) sensor 213 Recording medium

Claims (7)

[Claims] 1. A method for controlling a light amount of an exposure laser of an image forming apparatus, comprising: when a video controller receives a print command from a host computer, the video controller instructs an engine controller to perform a printing operation; Starts the printing operation, activates the scanner motor, and the scanner motor rotation speed becomes constant, and the scanner motor becomes scanner ready. After the scanner becomes ready, the laser A forced emission signal is lowered. Level, forcing the laser diode A to emit light, and when the laser light is scanned over the sensor by a beam detection sensor that is disposed in a non-image area on the laser light scanning path and detects a horizontal image writing position timing. Beam detection, which is the horizontal synchronization signal Detecting the output of a signal; and, after detecting the beam detection signal, turning off the laser diode A by setting the forced emission signal of the laser A to a high level; and for a predetermined time after detecting the beam detection signal. Thereafter, the forced emission signal of the laser A is set to a low level to force the laser diode A to emit light, and then the sample and hold signal is set to a low level to set the sample and hold A signal to a low level to perform a sampling operation of the laser diode A; After performing the sample operation of the laser diode A, the sample hold signal is set to a high level, and the sample hold A
Raising the signal to a high level to hold the laser diode A; raising the level of the forced emission signal of the laser A to a high level to turn off the laser diode A; Laser diode A with emission signal at low level
And turning off the laser diode A by setting the forced emission signal of the laser A to a high level when the beam detection signal is detected. Next, after a certain time from the detection of the beam detection signal, the laser B Setting the forced emission signal to low level to cause the laser diode B to emit light, then setting the sample hold signal to low level, setting the sample hold B signal to low level, and performing a sample operation of the laser diode B; After performing the sampling operation of the diode B, the sample hold signal is set to a high level, and the sample hold B
Raising the signal to a high level to hold the laser diode B; turning off the laser diode B by setting the forced emission signal of the laser B to a high level; after a certain period of time, the image data still remains and the image formation is stopped. A method for controlling the amount of laser light in an image forming apparatus, comprising the steps of forcing the laser diode A to emit light again when necessary, and turning off the scanner motor when printing of image data is completed and ending the printing operation. 2. An optical scanning means for scanning a laser beam modulated in accordance with image information on an image carrier, a plurality of laser diodes as a light source for image exposure, and one detecting means for detecting a light amount of the laser diode. Photodiodes, the same number of laser driving means as the number of laser diodes for detecting the light amount of the laser diode from the output of the photodiode and controlling the light amount of each laser diode to a predetermined value,
The laser driving means includes a sample-and-hold circuit that switches between a sample operation for controlling the output current of the photodiode to have a constant value and a hold operation for holding the current value supplied to the laser diode constant. A laser drive control unit for controlling the laser drive unit by a control signal line, a laser light amount control device of the image forming apparatus, wherein the same number of laser diodes as the number of laser diodes connected from the laser drive control unit to each laser drive unit A first control signal line, and one second control signal line commonly connected from the laser drive control unit to each of the laser drive units, and the light amount of the laser diode is determined by a combination of the signal levels of the control signal lines. A laser light amount control device for an image forming apparatus, comprising: means for performing control. 3. The first control signal is a laser forcible emission signal having a function of forcibly emitting light from a laser diode, and the second control signal is a signal when the first control signal is at a signal level in a laser emission state. 3. The laser light amount control device of the image forming apparatus according to claim 2, wherein the signal is a signal having a function of switching the laser driving unit between a sample operation and a hold operation. 4. When a laser beam scans in a non-image area on the laser beam scanning path, the laser scanning position is detected in the non-image area by a horizontal synchronization signal for detecting a horizontal image writing timing. 4. The laser light amount control device for an image forming apparatus according to claim 2, wherein a laser sampling operation is performed in the non-image area. 5. A sample operation is performed simultaneously with laser emission for detecting the horizontal synchronization signal.
The laser light amount control device of the image forming apparatus according to any one of the above. 6. The plurality of laser driving means is one chip I
The laser light amount control device of the image forming apparatus according to claim 2, wherein the laser light amount control device is C-shaped. 7. A recording medium on which a control program for controlling the amount of light of a multi-beam with a smaller number of control signals than in a conventional example is recorded, wherein when the video controller receives a print command from a host computer, the video controller becomes an engine controller. A procedure instructing the engine controller to perform a printing operation, and causing the engine controller to start a printing operation; a procedure in which the scanner motor is started, and a step in which the rotation speed of the scanner motor becomes constant and the scanner motor becomes ready for scanning; After the scanner becomes ready, the procedure for setting the forced emission signal of the laser A to a low level and forcing the laser diode A to emit light, and detecting the timing of the horizontal image writing position in the non-image area on the laser light scanning path. The beam detection sensor A procedure for detecting that a beam detection signal, which is a horizontal synchronization signal generated when a laser beam scans, is output. After detecting the beam detection signal, the laser diode A And a certain time after the detection of the beam detection signal, the forced emission signal of the laser A is set to a low level to force the laser diode A to emit light, and then the sample hold signal is set to a low level to set the sample hold A The procedure for setting the signal to low level to perform the sampling operation of the laser diode A, and the step for performing the sampling operation of the laser diode A, then setting the sample and hold signal to the high level to set the sample and hold A
A procedure for setting the signal to a high level to hold the laser diode A, a procedure for setting the forced emission signal of the laser A to a high level to turn off the laser diode A, and forcing the laser A after a certain period of time after turning off the laser diode A Laser diode A with emission signal at low level
A procedure for forcibly emitting light, a procedure for setting the forced emission signal of the laser A to a high level when the beam detection signal is detected, and for turning off the laser diode A. The laser diode B is forced to emit light, then the sample and hold signal is set to low level, the sample and hold B signal is set to low level, and the laser diode B is sampled. After performing the sampling operation of the laser diode B, the sample hold signal is set to a high level, and the sample hold B
A procedure for setting the signal to a high level and holding the laser diode B, a procedure for setting the forced emission signal of the laser B to a high level and turning off the laser diode B. After a certain period of time, image data still remains and image formation is not performed. A recording medium on which a program for executing a procedure for forcing the laser diode A to emit light again when necessary and a procedure for turning off the scanner motor and terminating the printing operation when image data formation is completed are recorded.