JP2001051216A - Light beam scanning control circuit and optical unit using the same, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and finely adjust timing of scanning light beams, when a desired scanning is made to be performed with the plural light beams. SOLUTION: Clock generators 102, 105 synchronize a video clock supplied from an oscillation circuit with a detection signal detected by a photodetector for detecting a laser beam reference position. Then, delaying parts 104, 33 for delay the video clocks generated by the clock generators 102 105 by a desired time interval and supply them to parallel-serial converter 26, 27, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning control circuit, an optical unit using the same, and an image forming apparatus. More particularly, the present invention relates to a light beam scanning control circuit for causing a plurality of beams to perform a desired scanning, and uses the same. To an optical unit and an image forming apparatus.

In recent years, a laser beam printer (LBP: La
ser Beam Printer) requires higher speed and higher resolution. In order to increase the speed and the resolution with a laser beam printer, it is necessary to speed up the scanning of the laser beam. To speed up the scanning of the laser beam, it is necessary to rotate the polygon mirror constituting the optical unit at a high speed. At present, the rotation of the polygon mirror has reached the physical limit of 30,000 or more. Therefore, an optical unit using a multi-beam that scans a plurality of laser beams has been proposed.

An optical unit using a multi-beam scans a photosensitive drum while slightly shifting a plurality of laser beams to form an electrostatic latent image on the photosensitive drum. At this time, if the relative scanning positions of the plurality of laser beams do not match, the image will be degraded. Therefore, it is necessary to accurately set the scanning positional relationship between a plurality of laser beams.

[0004]

2. Description of the Related Art FIG. 1 is a block diagram showing an example of a conventional laser printer.

The laser printer 1 comprises a paper transport mechanism 2, a photosensitive drum 3, a charger 4, an optical unit 5, a developing unit 6, a transfer unit 7, a fixing unit 8, and a video controller 9.

The paper 10 is moved by an arrow A by the paper transport mechanism 2.
Conveyed in the direction. The transported sheet 10 is supplied to the photosensitive drum 3. The photosensitive drum 3 is rotated in the direction of arrow B, and is first uniformly charged by the charger 4. Charger 4
The photosensitive drum 3 uniformly charged in the above is further rotated in the direction of the arrow B, and the laser beam L 1,
L2 is irradiated to form an electrostatic latent image.

The photosensitive drum 3 on which the electrostatic latent image has been formed by the optical unit 5 is further rotated in the direction of arrow B, and the developing device 6 develops the toner image with toner. Photosensitive drum 3
Is transferred by the transfer unit 7 to the sheet 10 conveyed in the direction of arrow A by the sheet conveying mechanism 2. The toner image is transferred to the sheet 10 by the transfer unit 7.

The paper 10 is further transported in the direction of arrow A by the paper transport mechanism 2 and supplied to the fixing device 8. The fixing device 8 fixes the toner image transferred to the paper 10 by heat or the like to the paper 10. The paper 10 on which the toner image is fixed by the fixing device 8 is further transported in the direction of arrow A by the paper transport mechanism 2 and is discharged.

Here, the optical unit 5 will be described.

The optical unit 5 includes a laser diode D
1, D2, polygon mirror 11, motor 12, motor driver 13, mirrors 14, 15, laser beam reference position detecting light detector 16, laser power adjusting light detector 1
7, 18, an optical control unit 19, a mechanism control unit 20, a power supply unit 21, and switches SW1 to SW4.

The laser diodes D1 and D2 are connected to the optical control unit 19, and the laser diodes L1 and D2 correspond to the laser beam L corresponding to the recorded image.
1 and L2 are emitted. The laser beams L1 and L2 emitted from the laser diodes D1 and D2 enter the polygon mirror 11.

The polygon mirror 11 is rotated in the direction of arrow C by a motor 12 at a constant rotation speed. The motor 12 is connected to a motor driver 13 and is controlled to rotate at a constant rotation speed, for example, 3000 rpm. Laser beam L emitted from laser diodes D1 and D2
1 and L2 are reflected by the rotating polygon mirror 11 and scanned in the direction of arrow C.

The polygon mirror 11 has a laser beam L
First, 1 and L2 are supplied to the mirror 15. Mirror 15
Is the laser beam L reflected by the polygon mirror 11
1 and L2 are reflected and made incident on the photodetector 16 for laser beam reference position detection. When the polygon mirror 11 further rotates in the direction of arrow C after the laser beams L1 and L2 are incident on the laser beam reference position detecting photodetector 16,
The laser beams L1 and L2 are further scanned in the direction of arrow D and are incident on the mirror 14. The mirror 14 reflects the laser beams L1 and L2 and supplies the laser beams L1 and L2 to the photosensitive drum 3.

When the polygon mirror 11 is rotated in the direction of arrow C, the laser beams L1 and L2 are scanned in the direction of arrow D, and move on the mirror 14 in the direction of arrow E. As the laser beams L1 and L2 move on the mirror 14 in the direction of arrow E, the laser beams L1 and L2 are scanned on the photosensitive drum 3 in the direction of arrow F. Laser beam L1,
When L2 scans on the photosensitive drum 3, light emission of the laser beams L1 and L2 is controlled according to an image to be recorded. At this time, the laser beams L1 and L2 are detected by the laser beam reference position detecting photodetector 16 and supplied to the optical control unit 19.

The optical control section 19 determines the positions of the laser beams L1 and L2 on the photosensitive drum 3 according to the detection signal detected by the laser beam reference position detecting light detector 16. The laser beams L1 and L2 are supplied to laser power adjusting photodetectors 17 and 18, respectively. The laser power adjusting photodetectors 17 and 18 output detection signals corresponding to the intensities of the laser beams L1 and L2. The detection signals output from the laser power adjustment photodetectors 17 and 18 are supplied to the optical control unit 19. The optical control unit 19 monitors the intensity of the laser beams L1 and L2, and
Control is performed so that the intensity of L2 becomes a desired intensity.

The optical control unit 19 includes laser control circuits 22 and 2
3. It is composed of an optical control circuit 24. The laser control circuits 22 and 23 control the light emission of the laser diodes D1 and D2 according to the signal supplied from the optical control circuit 24 and the detection signal supplied from the laser power adjusting photodetectors 17 and 18.

The optical control circuit 24 is supplied with a video signal corresponding to the recorded image from the video controller 9 and a detection signal from the laser beam reference position detecting photodetector 16. The optical control circuit 24 controls the emission of the laser beams L1 and L2 according to a video signal corresponding to a recorded image from the video controller 9 in accordance with a detection signal from the photodetector 16 for detecting a laser beam reference position.

Further, the mechanism control unit 20 includes the paper transport mechanism 2
, And control of each part mechanism such as rotation of the photosensitive drum 3. The mechanism control unit 20 includes detection switches SW1 to SW4 for detecting whether the stacker cover, the front cover, the eject cover are opened and closed, and the presence or absence of a transport unit.
Relays R1 to R4, R that switch according to the state of
5 When the stacker cover, the front cover, and the eject cover are closed and the transport unit is provided, the mechanism control unit 20 controls the relays R1 to R5.
Is turned on, and power is supplied from the power supply unit 21 to the optical control unit 19.

Next, the optical control circuit 24 will be described.

In the optical control unit 24, the laser beams L1,
The timing of L2 will be described.

FIGS. 2, 3 and 4 are views for explaining the timing of the laser beam. FIG. 2 shows the laser beam L
FIG. 3 is a diagram for explaining the displacement in the scanning direction of arrows L and L2, ie, the direction of arrow F. FIG. 3 is a diagram for explaining the displacement in the sub-scanning direction of laser beams L1 and L2, ie, the direction of arrow B. Shows a diagram illustrating the positional relationship between the laser beams L1 and L2.

The laser beam L1 is scanned prior to the laser beam L2 in the main scanning direction, that is, in the direction of arrow F, as shown in FIG. Further, as shown in FIG. 3, the laser beam L1 and the laser beam L2 are displaced by one line in the sub-scanning direction, that is, the direction of arrow B.

Therefore, as shown in FIG. 4A, the laser beams L1 and L2 scan the photosensitive drum 3 in the main scanning direction by the distance L in the main scanning direction, the direction of the arrow F, and the sub-scanning by one line. The scanning is performed in a state shifted in the direction of arrow B.

When dots are formed in the direction of arrow B as shown in FIG. 4B, it is necessary to accurately control the time T from the synchronization detection position BD to the position P0.

Next, a conventional circuit for controlling the timing of the laser beams L1 and L2 will be described.

FIG. 5 shows a block diagram of a conventional optical control circuit.

The optical control circuit 24 includes a video data distribution circuit 25, serial / parallel conversion circuits 26 and 27, a detection signal processing circuit 28, an oscillation circuit 29, and synchronization circuits 30 and 3.
1. It is composed of delay units 32 and 33 and 1 / N times units 34 and 35.

The video data distribution circuit 25 distributes the video data supplied from the video controller 9 alternately between the serial / parallel conversion circuit 26 and the serial / parallel conversion circuit 27 line by line.

The serial / parallel conversion circuit 26 has a function of 1 /
The video data supplied from the video data distribution circuit 25 is subjected to serial / parallel conversion at a timing corresponding to the clock supplied from the N-times unit 34. The serial data converted by the serial / parallel conversion circuit 26 is supplied to the laser control circuit 22. The laser control circuit 22 drives the laser diode D1 based on the serial video data supplied from the serial / parallel conversion circuit 26.

The serial / parallel conversion circuit 27
The video data supplied from the video data distribution circuit 25 is subjected to serial / parallel conversion at a timing according to the clock supplied from the N-fold unit 35. The serial data converted by the serial / parallel conversion circuit 27 is supplied to the laser control circuit 23. The laser control circuit 23 drives the laser diode D2 with the serial video data supplied from the serial / parallel conversion circuit 27.

The laser beams L1 and L2 emitted from the laser diodes D1 and D2 are supplied to the polygon mirror 11. The laser beams L1 and L2 reflected by the polygon mirror 11 are applied to a laser beam reference position detecting photodetector 1.
After being supplied to the photosensitive drum 6, the photosensitive drum 3 is irradiated.

Photodetector 16 for laser beam reference position detection
Is supplied to the detection signal processing circuit 28. The detection signal processing circuit 28 controls the timing of video data distribution by the video distribution circuit 25 based on the detection signal supplied from the laser beam reference position detecting photodetector 16. When the detection signal of the laser beam reference position detection photodetector 16 is supplied, the detection signal processing circuit 28 supplies a detection pulse to the synchronization circuits 30 and 31.

A clock is supplied from the oscillation circuit 29 to the synchronization circuits 30 and 31. The oscillation circuit 29 oscillates a clock N times the video clock. Synchronous circuit 3
0 and 31 output the clock of the oscillation circuit 29 according to the detection signal supplied from the detection signal processing circuit 28.

The clocks output from the synchronization circuits 30 and 31 are supplied to delay units 32 and 33. Delay units 32, 3
3 delays the clocks supplied from the synchronization circuits 30 and 31 by a predetermined time set in advance, and 1 / N
It is supplied to the doubling units 34 and 35.

At this time, the delay time of the delay units 32 and 33 is the time difference between the detection of the detection signal by the laser beam reference position detection photodetector 16 and the position where video data is recorded, that is, FIG. ), The clocks from the synchronization circuits 30 and 31 are delayed by a time T. 1 / N
The doubling units 34 and 35 multiply the clock supplied from the delay units 32 and 33 by 1 / N to have the same cycle as the clock of the video data, and then supply them to the serial / parallel conversion circuits 26 and 27.

Serial / parallel conversion circuits 26 and 27
Converts the parallel video data supplied from the video data distribution circuit 25 into serial data according to the clock supplied from the 1 / N multiplying units 34 and 35,
To supply.

[0037]

However, in the conventional laser scanning timing, a clock having a frequency N times higher than that of video data generated by an oscillator is extracted based on a detection signal of a reference position of a laser beam, and the extracted clock is extracted. Since the video clock is generated by multiplying the video clock by 1 / N, there is a problem that the output timing of the video data can be adjusted only in a clock unit having a frequency N times the video clock.

Further, if the clock timing is controlled by increasing the clock frequency, it is necessary to use usable electric components corresponding to a high frequency or to take measures against electromagnetic waves, thereby increasing the cost. was there.

The present invention has been made in view of the above points, and an object of the present invention is to provide a light beam scanning control circuit capable of easily and finely adjusting the scanning timing of a light beam, an optical unit using the same, and an image forming apparatus. Aim.

[0040]

Means for Solving the Problems Claims 1 and 5 of the present invention.
Reference numeral 9 denotes a light beam generating means for generating a light beam to be irradiated on a scanning target, a light beam scanning means for scanning the light beam generated by the light beam generating means, and a light beam scanned by the light beam scanning means. Position detecting means for detecting at a preset reference position and generating a detection signal, and clock generating means for generating a predetermined clock and synchronizing and outputting the clock generated with the detection signal generated by the reference position detecting means And characterized in that:

According to the first, fifth, and ninth aspects, the clock is synchronized with the detection signal by the clock generation means, so that the deviation due to the clock can be eliminated.

According to the present invention, the clock generating means is constituted by a clock generator.

According to the second, sixth, and tenth aspects of the present invention, the clock generating means is constituted by the clock generator, so that the constitution can be made at a low cost.

Further, claims 3, 7, and 11 of the present invention are:
A light detecting means for detecting the light beam at a predetermined position by the position detecting means, and comparing a detection signal of the light detecting means with a reference voltage,
Comparing means for generating a detection signal in accordance with the magnitude of the detection signal, and controlling the light amount of the light beam generated by the light beam generation means to adjust the detection position of the detection signal.

According to the third, seventh and eleventh aspects of the present invention, the detection position of the detection signal can be finely adjusted in an analog manner.

According to a fourth aspect of the present invention, the light beam generating means comprises a plurality of light beam generating sections for generating light beams, and the clock generating means comprises a plurality of light beam generating sections. A light beam generated by each of the plurality of light beam generators is provided so as to be synchronized at a predetermined timing.

According to the present invention, a plurality of light beams can be scanned in synchronization with a predetermined timing.

[0048]

FIG. 6 is an external view of a laser printer according to an embodiment of the present invention.

The laser printer 200 of this embodiment has a paper cassette 202, a transport section 203,
The image forming unit 204, the stacker 205, and the operation panel 206 are integrally mounted.

The paper cassette 202 stores recording paper. The paper cassette 202 is mounted on the printer main body 201, for example, in a plurality of stages for each paper size. The sheet held in the sheet cassette 202 is supplied to the image forming unit 203 by a sheet conveying unit.

The image forming unit 204 includes a paper cassette 202
An image is formed on the recording paper transported from the printer. The recording paper on which the image is formed by the image forming unit 204 is a stacker 205
Is discharged.

FIG. 7 is a block diagram showing a main part of an embodiment of the image forming apparatus of the present invention. The same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted.

The image transport section 203 includes a pickup roller 207 and a transport roller 208. The pickup roller 207 comes into contact with the recording paper stored in the paper cassette 202 and picks up the recording paper from the paper cassette 202.

The recording paper picked up by the pickup roller 207 is supplied to the image forming unit 204 by the transport roller 208.

The image forming unit 204 includes a photosensitive drum 209,
It comprises a charger 210, an optical unit 211, a developing device 212, a cartridge 213, a transfer device 214, a cleaner 215, a fixing device 216, and transport rollers 217 to 223. The photosensitive drum 209 is rotatable in the direction of arrow A. When the photosensitive drum 209 faces the charger 210, the photosensitive drum 209 is charged by the charger 210.

When the photosensitive drum 209 is further charged in the direction of arrow A after being charged by the charger 210, the optical unit 211 emits a laser beam. Photosensitive drum 209
In, an electrostatic latent image is recorded by a laser beam supplied from the optical unit 211. When the photosensitive drum 209 further rotates in the direction of arrow A after the electrostatic latent image is formed on the optical unit 211, the photosensitive drum 209 faces the developing device 212.

The developing device 212 is supplied with toner from the cartridge 213, and develops the electrostatic latent image recorded on the photosensitive drum 209 with the toner supplied from the cartridge 213.

The photosensitive drum 209, on which the toner image has been developed by the toner in the developing device 212, further rotates in the direction of arrow A and faces the transfer device 214. In the transfer unit 214, the recording paper is conveyed by the rollers 217, and the recording paper faces the photosensitive drum 209. The transfer device 214 is provided for the photosensitive drum 20.
The toner image developed in Step 9 is transferred to a recording sheet.

When the toner image is transferred to the recording paper by the transfer device 214, the photosensitive drum 209 further rotates in the direction of arrow A and faces the cleaner 215. Cleaner 215
Removes excess toner from the photosensitive drum 209. After the excess toner is removed by the cleaner 215, the photosensitive drum 209 is further rotated in the direction of arrow A, and faces the charger 210 again.

The recording paper is supplied between the photosensitive drum 209 and the transfer unit 214 by the roller 217. The toner image recorded on the photosensitive drum 209 is transferred to the recording paper by the transfer device 214. The recording sheet onto which the toner image has been transferred is supplied to the fixing device 216.

The fixing device 216 heats the recording paper and fixes the toner image transferred from the photosensitive drum 209 by the transfer device 214 to the recording paper. The recording paper on which the toner image has been fixed by the fixing device 216 is a pair of rollers 218, 219, and 22.
0, 221 and discharged to the stacker 205. When recording is performed on both sides of the recording paper, the roller 21 is moved after the rear end of the recording paper reaches the roller 218.
By inverting 8, 219, the recording paper is conveyed in the direction of arrow B. The recording paper includes rollers 218, 219,
The sheet is further conveyed in the direction of arrow B by 222, 223, and 224, and reaches the roller 217 again with the front and back reversed. By recording the toner image again on the recording paper that has reached the roller 217, recording can be performed on the back surface of the recording paper.

Next, the image forming section 204 will be described.

FIG. 8 is a block diagram of an image forming section of one embodiment of the image forming apparatus of the present invention, and FIG. 9 is a block diagram of an optical unit of one embodiment of the image forming apparatus of the present invention. 7, the same components as those of FIG. 7 are denoted by the same reference numerals, and the description thereof will be omitted.

The optical unit 211 has a luminance modulated 2
Are changed in the main scanning direction (arrow M).
(One direction).

The optical unit 211 includes the semiconductor laser 22
5,226, polygon mirror 227, fθ lens 22
8. It is composed of reflecting mirrors 229 and 230 and an optical sensor 231. The light beams BM1 and BM2 emitted from the semiconductor lasers 225 and 226 are supplied to the polygon mirror 227 via the adjusters 232 and 233. Polygon mirror 227
Is rotated in the direction of arrow C by the motor 234, and the light flux BM
1 and BM2 are deflected in accordance with the rotation angle to scan in the direction of arrow M1.

Light beam B reflected by polygon mirror 227
M1 and BM2 are reflected by the mirror 230 and the optical sensor 2
After being incident on 31, the light is reflected by the reflecting mirror 229 and supplied to the photosensitive drum 209. The light detected by the optical sensor 231 is supplied to the optical control circuit 101. Control unit 235
Controls various timings based on the detection result of the optical sensor 231.

FIG. 10 is a block diagram showing an optical unit according to an embodiment of the image forming apparatus of the present invention. The same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

The optical control circuit 101 of this embodiment comprises a video data distribution circuit 25, a parallel / serial conversion circuit 2
6, 27, a detection signal processing circuit 102, a video clock generation circuit 103, clock generators 104 and 105,
It comprises delay units 32 and 33.

The video data distribution circuit 25 distributes the video data supplied from the video controller 9 between the serial / parallel conversion circuit 26 and the serial / parallel conversion circuit 27 alternately for each line.

The serial / parallel conversion circuit 26 performs serial / parallel conversion of the video data supplied from the video data distribution circuit 25 at a timing corresponding to the clock supplied from the clock generator 104. The serial data converted by the serial / parallel conversion circuit 26 is supplied to the laser control circuit 22. The laser control circuit 22 drives the semiconductor laser 235 with the serial video data supplied from the serial / parallel conversion circuit 26.

The serial / parallel conversion circuit 27 performs serial / parallel conversion of the video data supplied from the video data distribution circuit 25 at a timing corresponding to the clock supplied from the clock generator 105. The serial data converted by the serial / parallel conversion circuit 27 is supplied to the laser control circuit 23. The laser control circuit 23 drives the semiconductor laser 236 with the serial video data supplied from the serial / parallel conversion circuit 27.

The detection signal processing circuit 102 separates the detection signal of the laser beam L1 and the detection signal of the laser beam L2 from the detection signal of the optical sensor 231 for detecting the reference position of the laser beam, and
5 and the laser control circuits 22 and 23.

The clock generators 104 and 105 are supplied with a video clock from the video clock generation circuit 103. Clock generators 104 and 105
The video clock generated by the video clock generation circuit 103 is transmitted to the laser beam reference position detecting optical sensor 231.
And output in synchronization with the detection signal detected by.

The video clocks output by the clock generators 104 and 105 in synchronization with the detection signal detected by the laser beam reference position detecting optical sensor 231 are supplied to delay units 32 and 33, and are used for detecting the laser beam reference position. The signal is supplied to the parallel / serial conversion circuits 26 and 27 after being delayed by a predetermined time set as the time from the detection by the optical sensor 231 to the start of information recording.

Here, the detection signal processing circuit 102 will be described in detail.

FIG. 11 is a block diagram of a detection signal processing circuit according to an embodiment of the image forming apparatus of the present invention.

The detection signal processing circuit 102 includes a comparator 106, a reference voltage source 107, and AND gates 108 and 10.
9, a timer 110 and an inverter 111.

Optical Sensor 23 for Laser Beam Reference Position Detection
The detection signal detected at 1 is supplied to the non-inverting input terminal of the comparator 106. A reference voltage source 107 is supplied to an inverting input terminal of the comparator 106. The comparator 106 outputs a high level when the detection signal is higher than the reference voltage generated by the reference voltage source 107, and outputs a low level when the detection signal is lower than the reference voltage.

The output of the comparator 106 is supplied to an AND gate 108 and an AND gate 109, and is also supplied to a timer 110. The timer 110 detects the falling of the detection signal, and outputs a pulse that becomes high level at least at time T or more. The output pulse of the timer 110 is supplied to the AND gate 108 and the inverter 111.

The AND gate 108 performs an AND logic operation on the detection signal detected by the laser beam reference position detecting optical sensor 231 and the output signal of the timer 110.

The inverter 111 inverts the output of the timer 110 and supplies the inverted output to the AND gate 109. The AND gate 109 is provided for the optical sensor 2 for detecting the laser beam reference position.
The AND logic of the detection signal detected at 31 and the inverted signal of the output signal of the timer 110 is taken.

FIG. 12 is a diagram for explaining the operation of the detection signal separation circuit according to one embodiment of the present invention. FIG. 12A shows a detection signal of the laser beam reference position detecting optical sensor 231, and FIG.
FIG. 12B shows the output signal of the timer 110, and FIG.
FIG. 12D shows an output signal of the D gate 108, and FIG.

As shown in FIG. 12A, the laser beam L
1 and a pulse S2 corresponding to the laser beam L2 are supplied at intervals of time T or less.

When the detection signal rises to a high level by detecting the laser beam L1 at time t1, FIG.
As shown in FIG. 12B, the output of the timer 110 is at a low level, and the output of the inverter 111 is at a high level. Therefore, the inputs of the AND gate 109 are both at a high level. AND gate 109
Output goes high.

Next, at time t2, when the detection signal falls to a low level as shown in FIG.
As shown in (B), the output of the timer 110 rises to a high level. When the output of the timer 110 rises to a high level, the output of the inverter 111 goes to a low level,
Both inputs of the AND gate 109 become low level,
Therefore, the output of the AND gate 109 becomes low level as shown in FIG. At this time, as for the output of the AND gate 108, the output of the timer 110 becomes high level, but the detection signal becomes low level.
The low level is maintained as shown in FIG.

Next, at time t3, when the detection signal again rises to a high level in response to the laser beam L2 as shown in FIG. 12A, the timer 1 is turned on as shown in FIG.
Since the output of 10 keeps the high level from the time t2 to the time T, it remains at the high level, so that the input of the AND gate 108 rises to the high level by the detection signal, and as shown in FIG. The output of the AND gate 108 goes high. Further, since the output of the inverter 111 is maintained at the low level, the output of the AND gate 109 remains at the low level as shown in FIG.

Next, at time t4, when the detection signal falls from the high level to the low level in response to the laser beam L2 as shown in FIG. 12A, the output of the timer 110 as shown in FIG. Maintains a high level for a time T from time t2, and thus remains at a high level.
When the input of the AND gate 108 falls to a high level in response to the detection signal, as shown in FIG.
The output of the ND gate 108 falls to a low level. Further, since the output of the inverter 111 is maintained at a low level, as shown in FIG.
Output remains at low level.

At time t5, even if the output of timer 110 falls to the low level, the output of both AND gates 108 and 109 is held at the low level because the detection signal is at the low level.

As described above, the AND gate 109 outputs the pulse S shown in FIG. 12A as shown in FIG.
1 is output from the AND gate 108 as shown in FIG.
As shown in (D), only the pulse S2 shown in FIG. 12 (A) is output. In this manner, the pulse S1 corresponding to the laser beam L1 and the pulse S2 corresponding to the laser beam L2 can be separated from the pulses S1 and S2 corresponding to the laser beams L1 and L2 shown in FIG.

Next, the clock generators 104 and 10
5 will be described.

FIG. 13 is a block diagram of a clock generator according to an embodiment of the image forming apparatus of the present invention.

The clock generators 104 and 105 are composed of commercially available relatively inexpensive ICs. Examples of usable clock generators include a standard clock generator “MM66234FP” manufactured by Mitsubishi Electric Corporation.
Is mentioned.

Clock generators 104 and 105 are
As shown in FIG. 13, it is composed of a delayed clock generation circuit 112, a synchronous clock selection circuit 113, a phase detection circuit 114, and a synchronous clock generation circuit 115. Video clocks are supplied to the clock generators 104 and 105 from the video clock generation circuit 103 as clock inputs.
The output of the detection signal processing circuit 102 is supplied as a trigger input.

The clock generators 104 and 105
The video clock supplied from the video clock generation circuit 103 is output in synchronization with the detection signal supplied from the detection signal processing circuit 102.

FIG. 14 is a diagram illustrating the operation of a clock generator according to an embodiment of the image forming apparatus of the present invention. FIG.
14A shows a video clock generated by the video clock generation circuit 103, and FIG. 14B shows a detection signal processing circuit 102.
14C shows an output video clock of the clock generators 104 and 105. FIG.

The clock generators 104 and 105
As shown in FIG.
3 is output in synchronization with the detection signal supplied from the detection signal processing circuit 102 shown in FIG. 14B as shown in FIG. 14C.

The video clocks generated by the clock generators 104 and 105 are supplied to the serial / parallel conversion circuits 26 and 27 after being delayed by the delay units 32 and 33 for a predetermined delay time. The video data converted to serial data by the serial / parallel conversion circuits 26 and 27 at timing according to the video clock is supplied to laser control circuits 22 and 23.

Next, the laser control circuits 22 and 23 will be described.

FIG. 15 is a block diagram of a laser control circuit of an embodiment of the image forming apparatus of the present invention.

The laser control circuits 22 and 23 include a buffer amplifier 116, a drive voltage supply unit 117, a drive transistor 118, a limiting resistor 119, an optical output level detection unit 120,
Switches 121 and 122, write light amount determination unit 123, write light amount control unit 124, synchronization detection light amount determination unit 125, synchronization detection light amount control unit 126, driver amplifier 127, timing signal generation units 128 and 129, write light amount setting level The generator 130 includes a synchronization detection light amount setting level generator 131.

The buffer amplifier 116 amplifies the video data supplied from the parallel / serial conversion circuits 26 and 27. The video data amplified by the buffer amplifier 116 is supplied to the drive voltage supply unit 117. The drive voltage supply unit 117 supplies a drive voltage corresponding to the video data supplied from the buffer amplifier 116 to the drive transistor 11.
8 base.

The driving transistor 118 has a collector connected to the semiconductor lasers 235 and 236, and an emitter grounded via the resistor 119. Drive transistor 118
The collector current is controlled according to the drive voltage supplied from the drive voltage supply unit 117, and the
The drive current flowing through the control circuit 36 is controlled. For this reason, the amount of light emitted from the semiconductor lasers 235 and 236 is controlled according to the drive current, and the laser beam L
1 and L2 are controlled.

At this time, the laser beams L1 and L2 output from the semiconductor lasers 235 and 236 are supplied to the laser power adjusting photodetectors 17 and 18. The laser power adjusting photodetectors 17 and 18 are composed of semiconductor lasers 235 and 2
The light intensity of the laser beams L1 and L2 output from the light source 36 is detected and supplied to the light output level detection unit 120.

The light output level detecting section 120 generates a detection signal according to the signals supplied from the laser power adjusting light detectors 17 and 18. The detection signal generated by the light output level detection unit 120 is supplied to the switch 121. The switch 121 is switched by the timing signal B rising at the falling of the timing signal A, and supplies the detection signal generated by the optical output level detection unit 120 to either the write light amount determination unit 123 or the synchronization detection light amount determination unit 125. I do.

The write light amount determination unit 123 includes the switch 12
1 and the preset write light amount setting level V1 from the write light amount setting level generator 130. The write light amount determination unit 123 includes a switch 121
Supplies the write light amount setting level V1 to the write light amount control unit 124 when the detection signal is supplied from.

The write light amount control unit 124 is supplied with the output signal of the write light amount determination unit 123 and the timing signal A output at the start of the print signal. Write light amount controller 124
Controls the output signal of the writing light amount determination unit 123 according to the timing signal A.

The writing light amount control section 124 outputs an output signal of the writing light amount determining section 123 with the timing signal A. The output signal output from the writing light amount control unit 124 is supplied to the switch 122.

The detection signal supplied from the switch 121 and the preset synchronization light amount setting level V2 generated by the synchronization detection light amount setting level generator 131 are supplied to the synchronization detection light amount determination unit 125. When the detection signal is supplied from the switch 121, the synchronization detection light amount determination unit 125 supplies the synchronization detection light amount setting level V2 to the synchronization detection light amount control unit 125.

The output signal of the synchronization detection light quantity determination section 125 and the timing signal B are supplied to the synchronization detection light quantity control section 126. The synchronization detection light amount control unit 126 controls an output signal of the synchronization detection light amount determination unit 125 according to the timing signal B.

The synchronization detection light quantity control section 126 outputs the output signal of the synchronization detection light quantity determination section 125 in response to the timing signal B. The output signal output from the synchronization detection light amount control unit 126 is supplied to the switch 122.

The switch 122 includes the writing light amount controller 12.
4 and the output signal of the synchronization detection light amount control unit 126 are supplied.
24 or the output signal of the synchronization detection light amount control unit 126 is selectively output.

The output signal of the switch 122 is supplied to the driver amplifier 127. The driver amplifier 127 amplifies the output signal selected and output by the switch 122 and supplies the output signal to the drive voltage supply unit 177.

FIG. 16 is a view for explaining the operation of the laser control circuit of an embodiment of the image forming apparatus of the present invention. 16A is a timing signal A, FIG. 16B is a timing signal B,
FIG. 16C shows the output of the driver amplifier 127, and FIG.
(D) is a print signal P ′, and FIG. 16 (E) is a laser output L.
D ′, FIG. 16F shows the waveform of the detection signal of the laser beam reference position detecting optical sensor 231.

When the signal rises at the start of the print signal shown in FIG. 16D, the timing signal A rises as shown in FIG. When the timing signal A rises, the write light amount determination unit 123 and the write light amount control unit 124 operate, and the write light amount setting level V
1 is output. At this time, since the variable terminal of the switch 122 is connected to the terminal a, the writing light amount setting level V1 is set to the drive voltage supply unit 1 via the driver amplifier 127.
17 is supplied.

For this reason, as shown in FIG. 16E, the semiconductor lasers 235 and 236 output the write light amount setting level V1.
Is output in accordance with the laser light output LD ′.

Next, when the timing signal A falls and the timing signal B rises, the switches 121 and 12
2 is connected to the synchronization detection light quantity determination unit 125 and the synchronization detection light quantity control unit 126, and the synchronization detection light quantity determination unit 125 and the synchronization detection light quantity control unit 126 operate. Therefore, the synchronization detection light amount setting level V2 is output from the synchronization detection light amount control unit 126, and the driver amplifier 12
7 is supplied. The synchronization detection light amount setting level V2 is supplied to the drive voltage supply unit 117 via the driver amplifier 127.

Therefore, as shown in FIG. 16E, the semiconductor lasers 235 and 236 output a laser light output LD 'corresponding to the synchronization detection light amount setting level V2.

For this reason, during the output period T of the timing signal B immediately before the print signal to be recorded on the photosensitive drum 3 is output, the semiconductor lasers 235 and 236 are set to the synchronous detection light amount. The detection signal is detected by the laser beam reference position detecting optical sensor 231. Note that during a period during which a print signal to be recorded on the photosensitive drum 3 is output, the switches 121 and 122 are switched, and FIG.
As shown in (E), the laser light output LD 'is set to the writing light amount setting level V1.

The synchronization detection light quantity setting level generator 13
Reference numeral 1 denotes a configuration capable of adjusting the generated synchronization detection light amount setting level V2. The detection signal detected by the laser beam reference position detection optical sensor 231 is adjusted by adjusting the synchronization detection light amount setting level V2 generated by the synchronization detection light amount setting level generator 131, and the detection signal processing circuit 102
The timing at the time of detection is controlled.

FIG. 17 is a diagram for explaining the operation of the timing control by adjusting the synchronization detection light amount setting level in one embodiment of the image forming apparatus of the present invention. FIG. 17A shows a laser beam L
17 (B) shows the detection signal processing circuit 10
2 shows the detection signal.

The synchronization detection light quantity setting level V2 generated by the synchronization detection light quantity setting level generator 131 is set to a level V2-1.
17A, the relationship between the light amounts of the laser beams L1 and L2 and the reference voltage Vref generated by the reference power supply 107 of the detection signal processing circuit 102 is as shown by a solid line in FIG. Comparator 1 of circuit 102
At 06, a detection signal is generated at the timing indicated by the solid line in FIG.

The synchronization detection light quantity setting level generating section 13
The synchronization detection light amount setting level V2 generated in step 1 is set to level V
By setting to 2-2, the laser beams L1, L2
17A and the reference voltage Vref generated by the reference power supply 107 of the detection signal processing circuit 102 are as shown by a broken line in FIG. 17A. The detection signal is generated at the timing shown by the broken line in FIG. That is, by setting the synchronization detection light amount setting level V2 generated by the synchronization detection light amount setting level generating section 131 to the level V2-2, the level of FIG.
The timing can be advanced by the time Δt as compared with the case where the synchronization detection light amount setting level V2 indicated by the solid line in (B) is set to the level V2-1.

As described above, the synchronization detection light amount setting level generator 131 can adjust the detection timing in an analog manner by adjusting the generated synchronization detection light amount setting level V2 and adjusting the light amounts of the laser beams L1 and L2. .

Next, the overall operation will be described.

FIG. 18 is an overall operation explanatory view of an embodiment of the image forming apparatus of the present invention. 18A is a timing signal B on the side of the laser beam L1, FIG. 18B is a detection signal on the side of the laser beam L1, and FIG.
18 (D) is the output light amount of the laser beam L1, FIG. 18 (E) is a timing signal B on the laser beam L2 side, FIG. 18 (F) is a detection signal on the laser beam L1 side, FIG. (G) is a print signal on the side of the laser beam L1, FIG. 18 (H) is an output light amount of the laser beam L1, and FIG.
18 (I) shows a detection signal of the laser beam reference position detecting optical sensor 231, FIG. 18 (J) shows a control signal for controlling a mechanism, and FIG. 18 (K) shows a control signal for video data control.

In a period T1 shown in FIG.
As shown in (D), the light amount of the laser beam L1 is the light amount for synchronization detection. As shown in FIG. 18D, during the period in which the light amount of the laser beam L1 becomes the light amount for synchronization detection, FIG.
As shown in (B), the synchronous reference position is detected by the laser beam reference position detecting optical sensor 231. FIG.
The timing of outputting the print signal shown in FIG. 18C is controlled based on the synchronization reference position shown in FIG.

Further, the laser beam L2 is shown in FIG.
As shown in FIG. 18, the light amount becomes the synchronization detection light amount in a period T2 which is delayed from the period T1 shown in FIG. 18A by a predetermined period ΔT. During the period when the light amount of the laser beam L1 becomes the synchronization detection light amount as shown in FIG. 18E, the laser beam reference position detection optical sensor 231 as shown in FIG.
, The synchronization reference position is detected. The timing for outputting the print signal shown in FIG. 18G is controlled based on the synchronization reference position shown in FIG.

Also, according to the output signal of the laser beam reference position detecting optical sensor 231 shown in FIG.
The mechanical mechanism such as the rotation of the photosensitive drum 3 is controlled at the timing shown in FIG.
As shown in (K), capture of video data and the like are controlled. That is, while the mechanism such as the photosensitive drum 3 performs the operation for one line, the data for two lines is fetched and the recording is performed.

As described above, video data is output after a predetermined time has elapsed since the detection signal is detected by the laser beam reference position detecting optical sensor 231, and the image corresponding to the video data is output to the photosensitive drum 3. An electrostatic latent image can be recorded. At this time, the time until the writing of the video data is not performed in clock units, but is generated by synchronizing the output clock of the commercially available clock generator 104 with the detection signal by the laser beam reference position detection optical sensor 231. The output timing of the video data is set by delaying the output by the delay units 32 and 33 for a predetermined time, so that the laser beam reference position detecting optical sensor 23 does not generate a clock unit shift.
Video data can be output at a timing synchronized with the first detection signal.

The fine adjustment is performed by the laser control circuit 2.
By controlling the rising edge of the detection signal by the laser beam reference position detecting optical sensor 231 by controlling the synchronization detection light amount setting level V2 of the second and the second 23, the timing can be finely adjusted.

In this embodiment, two laser beams are synchronized, but a plurality of laser beams may be scanned in synchronization.

In this embodiment, a laser printer has been described. However, the present invention is not limited to this, and the present invention is applicable to an apparatus that scans a light beam at a predetermined timing.

This embodiment can also be applied to a tandem type electrophotographic color printer.

Here, a case where the present invention is applied to a tandem type electrophotographic color printer will be described with reference to the drawings.

A tandem image in which colors (yellow, magenta, cyan, and black) corresponding to the respective photosensitive drums are separately formed on the four photosensitive drums, and the images are sequentially transferred to paper and superimposed to form a color image. There is an electrophotographic color printer. The present invention can be used in such an apparatus.

FIG. 19 is a conceptual diagram of exposure of the scanning optical system at the time of tandem arrangement. In this embodiment, four beams are simultaneously scanned by one polygon mirror, and each beam is a diagram showing a scanning optical system for exposing different photosensitive drums. A BD sensor for detecting the scanning start position of each beam is provided for each beam.

The arrangement of the BD sensors in the embodiment shows the concept of beam detection, and the actual arrangement may be performed by a method other than the embodiment, as long as the same function is selected.

Next, the color image forming section 190 will be described.

FIG. 19 is a view showing the arrangement of a color image forming section of an embodiment of a tandem type electrophotographic color printer according to the present invention. 8, the same components as those of FIG. 8 are denoted by the same reference numerals, and the description thereof will be omitted.

The optical unit changes the luminance-modulated four light beams and scans in the main scanning direction (the direction of arrow M2).

The optical unit comprises a semiconductor laser light source 33.
6, polygon mirror 227, fθ lens 328, reflecting mirror
329 and a BD sensor 331. The light beam emitted from the semiconductor laser 336 is supplied to the polygon mirror 227. The polygon mirror 227 is rotated in the direction of arrow C by the motor 234, deflects the light beam according to the rotation angle, and scans in the direction of arrow M2.

The light beam reflected by the polygon mirror 227 is reflected by the reflection mirror 329 and enters the BD sensor 331. Further, the light is reflected by the reflection mirror 329 and supplied to the photosensitive drum 209. The light detected by the BD sensor 231 is supplied to an optical control circuit 301 (described later). The start timing of the latent image is controlled based on the detection result of the BD sensor 331.

FIG. 20 is a block diagram of the signal processing in FIG.

In FIG. 20, the same components as those in FIG. 10 are denoted by the same reference numerals. The video data distribution unit 325 is the video data distribution unit 25 in FIG. 10, the para / serial conversion circuit 327 is the para / serial conversion circuits 26 and 27 in FIG. 10, the delay unit 304 is the delay units 32 and 33 in FIG. The generator 302 is the clock generator 104 of FIG.
105, the detection signal processing circuit 312 is the detection signal processing circuit 102 shown in FIG. 10, the video clock generation circuit 303 is the video clock generation circuit 103, and the laser control circuit 323 is the one shown in FIG.
The laser control circuits 22 and 23 and the LD 336 are the laser diodes (LD) 235 and 236 and the BD sensor 33 shown in FIG.
1 is a laser beam reference position detecting optical sensor 23 shown in FIG.
1 respectively.

The optical control circuit 301 of this embodiment comprises a video data distribution circuit 325 and a video clock generation circuit 30.
3 and 4 colors (yellow, magenta, cyan,
Black) Each parallel / serial conversion circuit 327, detection signal processing circuit 312, clock generator 302,
The delay unit 304 is configured.

The video data distribution circuit 325 converts the video data supplied from the video controller 9 into a serial / color image of each color corresponding to the video data for each line.
The signal is distributed to the parallel conversion circuit 327.

Each color serial / parallel conversion circuit 327
Performs serial / parallel conversion of the video data supplied from the video data distribution circuit 325 at a timing corresponding to the clock supplied from the clock generator 304. The serial data converted by the serial / parallel conversion circuit 327 is supplied to the laser control circuit 322.
The laser control circuit 322 drives the semiconductor laser 336 with the serial video data supplied from the serial / parallel conversion circuit 327.

The detection signal processing circuit 312 for each color outputs a detection signal by a laser beam for each color from the detection signal of the corresponding BD sensor 331 to the clock generator 3 for each color.
04 and the laser control circuit 323.

The video clock is supplied from the video clock generation circuit 303 to the clock generator 304. The clock generator 304 outputs the video clock generated by the video clock generation circuit 303 in synchronization with the detection signal detected by the laser beam reference position detection optical sensor 231.

The BD is generated by the clock generator 304 of each color.
The video clock output in synchronization with the detection signal detected by the sensor 231 is supplied to the delay unit 332, and is delayed by a predetermined time set as a time from the detection by the BD sensor 231 to the start of information recording. It is supplied to the parallel / serial conversion circuit 326.

In such an apparatus, a latent image formed on the photosensitive drum 209 for each color is developed with a toner of a corresponding color, and the toner image of each color is superimposed on a sheet to form a color image. I do. Therefore, it is necessary to match the overlapping positions of the toner images of each color, and it is necessary to make the sizes of the toner images of each color uniform. Therefore, it is necessary to adjust the light amount and the writing timing for forming a latent image on the photosensitive drum 209 by each optical unit.

For this, the clock generator 302
The video clock is supplied to (Y, M, C, K) from the video clock generation circuit 303, and the output of the detection signal processing circuit 312 is supplied as a trigger input.

Clock generator 302 (Y, M, C, K)
Outputs the video clock supplied from the video clock generation circuit 303 in synchronization with the detection signal supplied from the detection signal processing circuit 102.

The video clock generated by clock generator 302 is supplied to serial / parallel conversion circuit 327 after being delayed for a predetermined delay time in delay section 304. The video data converted into serial data at a timing according to the video clock by the serial / parallel conversion circuit 327 is supplied to the laser control circuit 323.

The laser control circuit 323 for each color has the same configuration as the laser control circuits 22 and 23 shown in FIG.

Therefore, as described above, similarly to FIG. 15, the video data supplied from the parallel / serial conversion circuits 26 and 27 are amplified, a drive voltage corresponding to the video data is supplied to the drive transistor, and the semiconductor laser ( LD)
The drive current of 336 is controlled, and the semiconductor laser (LD) 336 controls the amount and timing of light emission according to the drive current.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

[0158]

As described above, according to the first, fifth, and ninth aspects of the present invention,
According to the method, the clock is synchronized with the detection signal by the clock generation means, so that there is an advantage that a shift due to the clock can be eliminated.

According to the second, sixth, and tenth aspects of the present invention, the clock generator is constituted by a clock generator, thereby having the advantage of being inexpensive.

According to the third, seventh and eleventh aspects of the present invention, the detection position of the detection signal is adjusted by controlling the light amount of the light beam, thereby finely adjusting the detection position of the detection signal in an analog manner. It has features such as being able to.

According to the fourth, eighth, and twelfth aspects of the present invention, it is possible to scan a plurality of light beams in synchronization with a predetermined timing accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a conventional laser printer.

FIG. 2 is a diagram for explaining the timing of a laser beam.

FIG. 3 is a diagram for explaining the timing of a laser beam.

FIG. 4 is a diagram for explaining the timing of a laser beam.

FIG. 5 is a block diagram of a conventional optical control circuit.

FIG. 6 is an external view of an embodiment of the image forming apparatus of the present invention.

FIG. 7 is a configuration diagram of a main part of an embodiment of the image forming apparatus of the present invention.

FIG. 8 is a configuration diagram of an image forming unit of an embodiment of the image forming apparatus of the present invention.

FIG. 9 is a configuration diagram of an optical unit according to an embodiment of the image forming apparatus of the present invention.

FIG. 10 is a block diagram of an embodiment of the image forming apparatus of the present invention.

FIG. 11 is a block diagram illustrating a detection signal processing circuit according to an embodiment of the image forming apparatus of the present invention.

FIG. 12 is a diagram illustrating the operation of a detection signal processing circuit according to an embodiment of the image forming apparatus of the present invention.

FIG. 13 is a block diagram of a clock generator according to an embodiment of the image forming apparatus of the present invention.

FIG. 14 is a diagram illustrating the operation of a clock generator of an embodiment of the image forming apparatus of the present invention.

FIG. 15 is a block diagram of a laser control circuit of an embodiment of the image forming apparatus of the present invention.

FIG. 16 is a diagram illustrating the operation of a laser control circuit of an embodiment of the image forming apparatus of the present invention.

FIG. 17 is an explanatory diagram of an operation of timing control by adjusting a synchronization detection light amount setting level in one embodiment of the image forming apparatus of the present invention.

FIG. 18 is an overall operation explanatory diagram of an embodiment of the image forming apparatus of the present invention.

FIG. 19 is a schematic configuration diagram of another embodiment of the image forming apparatus of the present invention.

FIG. 20 is a block diagram of another embodiment of the image forming apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 9 video controller 16 laser beam reference position detection photodetector 22, 23, 323 laser control circuit 25 video data division circuit 26, 27, 327 parallel / serial conversion circuit 32, 33, 304 delay unit 100 optical unit 101 optical control circuit 102, 312 detection signal processing circuit 103 video clock generation circuit 104, 105, 302 clock generator 302 clock 336 semiconductor laser

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference)

Claims (12)

[Claims] 1. A light beam is emitted at a desired timing and
A light beam scanning control circuit that scans the object to be scanned based on a predetermined clock; a light beam generating means for generating a light beam to be irradiated on the object to be scanned; and a light beam generated by the light beam generating means. Light beam scanning means for detecting, the light beam scanned by the light beam scanning means at a predetermined reference position, and a position detection means for generating a detection signal; Clock generating means for synchronizing the generated clock with the detection signal generated by the position detecting means and outputting the generated clock. 2. The light beam scanning control circuit according to claim 1, wherein said clock generating means is a clock generator. 3. The position detecting means for detecting the light beam at a predetermined position, comparing the detection signal of the light detecting means with a reference voltage, and generating a detection signal according to the magnitude of the reference voltage. The light beam according to claim 1, further comprising: a comparing unit configured to adjust a detection position of the detection signal by controlling a light amount of the light beam generated by the light beam generating unit. Scan control circuit. 4. The light beam generator has a plurality of light beam generators for generating a light beam, and the clock generator is provided for each of the plurality of light beam generators. The optical scanning control circuit according to claim 1, wherein the light beam generated by each of the light beam generators is controlled so as to be synchronized at a predetermined timing. 5. A light beam is emitted at a desired timing and
An optical unit that scans an object to be scanned based on a predetermined clock, comprising: a light beam generator that generates a light beam to be irradiated on the object to be scanned; and a light beam that scans the light beam generated by the light beam generator. Scanning means; position detecting means for detecting the light beam scanned by the light beam scanning means at a preset reference position to generate a detection signal; generating the predetermined clock; and the reference position detecting means And a clock generating means for synchronizing and outputting the generated clock with the detection signal generated in (1). 6. The optical unit according to claim 5, wherein said clock generation means is a clock generator. 7. The position detecting means for detecting the light beam at a predetermined position, comparing the detection signal of the light detecting means with a reference voltage, and generating a detection signal according to the magnitude of the reference voltage. 7. The optical unit according to claim 5, further comprising: a comparing unit that adjusts a detection position of the detection signal by controlling a light amount of the light beam generated by the light beam generating unit. . 8. The light beam generating means has a plurality of light beam generating units for generating a light beam, and the clock generating means is provided for each of the plurality of light beam generating units. 8. The optical scanning control circuit according to claim 5, wherein control is performed such that the light beams generated by the respective light beam generating units are synchronized at a predetermined timing. 9. A light beam is emitted at a desired timing and
An image forming apparatus that scans a scanning target based on a predetermined clock and forms an image in accordance with the scanning of the light beam, wherein: a light beam generating unit that generates a light beam to be irradiated on the scanning target; Light beam scanning means for scanning the light beam generated by the beam generation means, position detection means for detecting the light beam scanned by the light beam scanning means at a preset reference position, and generating a detection signal; An image forming apparatus comprising: a clock generation unit that generates the predetermined clock, and synchronizes the generated clock with the detection signal generated by the reference position detection unit and outputs the generated clock. 10. The image forming apparatus according to claim 9, wherein said clock generating means is a clock generator. 11. A position detecting means for detecting a light beam at a predetermined position, comparing a detection signal of the light detecting means with a reference voltage, and generating a detection signal according to the magnitude of the reference voltage. 11. The image forming apparatus according to claim 9, further comprising: a comparing unit that adjusts a detection position of the detection signal by controlling a light amount of the light beam generated by the light beam generating unit. 12. apparatus. 12. The light beam generator has a plurality of light beam generators for generating a light beam, and the clock generator is provided for each of the plurality of light beam generators. The image forming apparatus according to claim 9, wherein the light beams generated by the light beam generating units are controlled so as to be synchronized at a predetermined timing.