JP2001324688A - Optical scanning device and optical scanning method for image formation - Google Patents

Abstract

[PROBLEMS] To provide an image forming optical scanning device and a scanning method capable of forming a good image by irradiating light incident on a BD sensor in a stable state. An image forming apparatus having a plurality of laser light sources L1 and L2 emits light by adjusting the light amount of each laser light source when generating a horizontal synchronizing signal (/ BD signal), or emits light without adjusting the light amount. A control unit that can set the parameters independently is added. The optical system control unit 104 drives the semiconductor laser according to the setting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical scanning device and an optical scanning method for forming an image, and more particularly to a PWM.
(pulse width modulation) The present invention relates to an optical scanning device and an optical scanning method for forming an image by scanning a rotating photosensitive member with a plurality of light beams of a semiconductor laser driven based on a modulated signal.

[0002]

2. Description of the Related Art FIG. 2 is a side perspective view showing an example of a conventional electrophotographic printer, wherein 1 is a cylindrical photosensitive drum for forming an electrostatic latent image, and 2 is a photosensitive drum. A charging roller 3 for uniformly charging the photosensitive drum 1 positively, an optical unit 3 for scanning the photosensitive drum 1 in the axial direction with a laser beam, and a rotating polygon mirror 4 serving as a deflecting unit from the optical unit 3 13 are two laser beams emitted in accordance with the rotation of T.13. The rotating polygon mirror 13 is driven by a scanner motor which is a driving unit not shown in FIG.
It rotates on an axis perpendicular to the main scanning (horizontal) direction. By this rotation operation, the laser beam scans the scanning surface of the photosensitive drum 1 at a constant speed.

In the non-image area of this scanning, the laser beam 4
Is forcibly emitted at a predetermined timing, enters a reflection mirror disposed at a predetermined position near the photosensitive drum 1, is detected by an optical sensor (BD sensor), and based on the detected beam, a horizontal synchronization signal ( / BD signal) is generated.

A developing unit 5 develops an electrostatic latent image formed on the photosensitive drum 1 by the two laser beams 4 with a negatively charged toner. The transfer roller charger 7 transfers the formed toner image to a predetermined recording sheet. The transfer roller charger 7 is a fixing unit that fixes the toner on the recording sheet to the sheet by heating or melting the toner with a solvent vapor.

[0005] Reference numeral 8 denotes a standard cassette on which recording paper for forming an image (hereinafter, referred to as printing) is loaded. Reference numeral 9 denotes a standard cassette feed roller for feeding recording paper from the standard cassette 8; A resist sensor 11 for detecting a leading edge resist for printing the conveyed recording paper;
Is a paper ejection sensor for confirming whether or not the recording paper has been normally ejected from the fixing device 7, and 12 is a sensor for detecting the presence or absence of the paper in the standard cassette 8.

FIG. 3 is a block diagram showing a configuration of a printer control unit of a conventional electrophotographic printer.
A printer that performs communication with a host computer, receives image data, expands the received image data into printable data, and performs signal communication and serial communication with a printer engine control unit described later. It is a controller. 102 is the printer controller 10
An engine control unit controls each unit of the printer engine via signal communication and serial communication with the printer engine 1. Reference numeral 103 denotes an engine control unit 10 which conveys a recording sheet from a standard cassette 8 to a recording sheet being fed out of the apparatus in response to a print request from the printer controller 101.
2 is a sheet transport control unit that controls based on the instruction of 2.

A control unit 104 generates laser light based on image data from the printer controller 101 and rotates the rotary polygon mirror 13 by a scanner motor to generate a / BD signal based on an instruction from the engine control unit 102. An optical system control unit to be executed. Reference numeral 105 denotes a high-voltage output for primary charging, development, and transfer to the engine control unit 102.
Is a high-voltage control unit that outputs based on the instruction.

Reference numeral 106 denotes a fixing unit temperature control unit that controls the temperature of the fixing unit 7 to a predetermined temperature based on an instruction from the engine control unit 102. Reference numeral 107 denotes a sensor input unit for detecting the presence / absence of a sheet in the conveyance path, such as registration and discharge. The actual printing operation for performing the printing operation in accordance with a command or signal of the printer controller 101 is performed by the
02 is started by instructing each control unit connected to the engine control unit 102.

FIG. 4 is a block diagram for explaining control of a multi-laser beam.

Conventionally, control of the multi-laser beam of the laser L1 (L2) is executed by communication between the engine control unit 102 and the optical system control unit 104. For example, for one laser L1 (L2), the laser forced emission signal / L
ON1 (/ LON2), sample & hold request signal /
One SH1 (/ SH2) is prepared, and each laser L1 (L2) is forced to emit a forced emission signal / LON1 (/ LON) at a predetermined timing of a non-image area for each scan during a printing operation.
2), sample and hold request signal / SH1 (/ SH
The light emission is performed according to 2), and the control for adjusting the laser light amount to a predetermined light amount, that is, the start of APC (Automatic Power Control) is instructed.

In the APC mode, the laser driver 110, which is a component of the optical system control unit, has the forced emission signal / LON1 (/ LON2) active and the sample & hold request signal / SH1 (/ SH2)
Is active, the amount of laser light from the laser L1 (L2) is adjusted based on the output of the photodiode D that detects the laser beam from the laser L1 (L2).

FIG. 5 shows a timing chart relating to this series of APC and / BD signal detection control.

As shown in FIG. 5, a laser driver 110
Sets the / LON2 signal and / SH2 signal to the True state at the timing T1 of the non-image area, and sets the AP of the laser L2 to the true state.
Perform C. A certain time has passed since T1 (timing T
2) Then, to end APC of laser L2, / LON
The two signals and the / SH2 signal are set to the False state, and the / LON1 signal and the / SH1 signal are changed to the True state in order to perform APC of the laser L1. In this state, the apparatus waits until an output from the BD sensor is obtained. When the output signal / BD1 from the BD sensor is detected at the timing T3, the / LON1 signal and the / SH1 signal for stopping the emission of the laser L1 at the timing T4. Causes the signal to transition to the False state.

Next, at the timing T5, the laser L2
Is emitted in the APC mode, deflection scanning is performed, and light emitted from the laser L2 is incident on the BD sensor, and the BD sensor outputs a / BD2 signal (timing T6). After a certain period of time has passed since timing T5,
In order to stop the emission of the laser L2, the / LON2 signal is set, and the / SH2 signal is set to False at the timing T7.

[0015]

As described above, in an electrophotographic printer having a plurality of light-emitting sources as shown in the conventional example, each beam interval on the photosensitive drum and the output from the BD sensor / If the time interval between the BD1 signal and the / BD2 signal is not ideal, that is, if there is a difference in the interval, there is a problem in that an image shift occurs.

FIG. 6 is a diagram for explaining the cause of such an image shift. FIG. 6A shows the light distribution of the lasers 1 and 2 on the photosensitive drum. Laser 2 lags laser 1 by time t1. (B) is / B when an ideal / BD signal output is obtained.
It shows the output timing of the D1 signal and / BD2 signal, where t2 = t1. (B ') shows the case where the time from the / BD1 signal output to the / BD2 signal output is shorter than that of (B), that is, the case where t2 = t1> t3. In such a case, for example, if a vertical line of 2 dots / 2 space is printed, an image in which the edges of the laser 1 and the laser 2 do not match as shown in FIG.

The main cause of such a phenomenon when there is a difference in the time interval from the / BD1 signal output to the / BD2 signal output is the light waveform of the laser 1 and the laser 2 incident on the BD sensor. Because there is a difference. The reason for this will be described with reference to FIG.

First, the laser 1 emitted in the APC mode is deflected and scanned, and light is incident on the BD sensor with a light distribution as shown on the left side of the above figure. When the light level reaches the threshold value of the BD sensor, the BD sensor outputs a / BD1 signal after an output delay time. The emission of the laser 1 in the APC mode ends, and the emission of the laser 2 in the APC mode starts. Eventually, laser 2 emitting in APC mode
Is deflected and scanned, and light is incident on the BD sensor with a light distribution as shown on the right side of the above figure.

Here, when the light of the laser 2 incident on the BD sensor overshoots as shown in FIG.
The inclination of the light of the laser 2 incident on the D sensor is different from that at the time of the laser 1, and the time interval t10 passing through the threshold value of the BD sensor is a value t1 which is an ideal time interval shown in the drawing.
And different.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object the purpose of forming an image capable of forming a good image by allowing light incident on a BD sensor to enter in a stable state. An object of the present invention is to provide an optical scanning device and an optical scanning method.

[0021]

SUMMARY OF THE INVENTION In order to solve such a problem, an invention according to a first aspect is directed to a semiconductor laser having a plurality of light-emitting sources for emitting laser light, and a PW based on an image signal.
A laser driving unit that drives the semiconductor laser based on the M-modulated signal, and that can adjust a light amount of the laser light;
An optical system control unit for controlling a laser driving unit to generate a horizontal synchronization signal for all of the plurality of light emitting sources; and an optical system control unit provided at a start end on a scanning line of the laser light, detecting the laser light and outputting a detection signal. A horizontal synchronization signal detecting means for generating the horizontal synchronization signal, and a control means capable of independently and variably setting a light emission mode of a light emitting source incident on the horizontal synchronization signal detecting means when generating the horizontal synchronization signal. And

The invention described in claim 2 is the first invention.
5. The optical scanning device according to claim 1, wherein: a rotating polyhedron that deflects and scans the laser light to form a scanning line; a rotation driving unit that rotates the rotating polyhedron; and a photoconductor that forms an image on a portion irradiated with the scanning line. And a drum.

The invention described in claim 3 is the first invention.
3. In the optical scanning device for forming an image according to 2, the light emitting mode of the light incident on the horizontal synchronizing signal detecting means when generating the horizontal synchronizing signal is a light quantity adjusting light emitting mode or a constant current light emitting mode. Or any one of the following.

The invention described in claim 4 is the first invention.
3. The image forming optical scanning device according to 2, wherein the control unit is a control unit that sets a light emission mode of the light emission source by determining a time interval of a detection signal output from the horizontal synchronization detection unit. It is characterized by.

The invention described in claim 5 is the first invention.
Or in the optical scanning device for forming an image according to item 2, wherein the control means is a control means for setting a light emitting mode of the light emitting source according to a resolution of an image to be formed.

The invention according to claim 6 is the first invention.
3. The image forming optical scanning device according to claim 2, wherein the control unit is a control unit that sets a light emitting mode of the light emitting source based on a rotation speed of the rotating polyhedron.

The invention described in claim 7 is the first invention.
3. The optical scanning device according to claim 2, wherein the control unit is a control unit that sets a light emission mode of the light emission source according to a laser light amount.

The invention described in claim 8 is the first invention.
3. The image forming optical scanning device according to claim 2, wherein the control means further includes a control means for performing control for prohibiting a setting change within the same page.

According to a ninth aspect of the present invention, a plurality of beams used for image formation are controlled by controlling a light source of light incident on a horizontal synchronization signal detecting means when a horizontal synchronization signal is generated. An optical scanning method, comprising: measuring a time interval at which the horizontal synchronization signal is detected;
Changing the emission mode of the emission source according to the length of the time interval.

According to a tenth aspect of the present invention, in the optical scanning method for forming an image according to the ninth aspect, the step of changing a light emitting mode of the light emitting source is performed when the time interval is longer than a predetermined time. The light emitting mode of the light emitting source is set to a light amount adjusting light emitting mode, and in other cases, the light emitting mode of the light emitting source is set to a constant current light emitting mode.

According to the eleventh aspect of the present invention, a plurality of beams used for image formation are controlled by controlling a light source of light incident on a horizontal synchronizing signal detecting means when generating a horizontal synchronizing signal. The method comprises the steps of: measuring a resolution of an image to be formed; and changing a light emission mode of the light source according to the resolution.

According to a twelfth aspect of the present invention, in the optical scanning method for forming an image according to the eleventh aspect, the step of measuring the resolution includes the step of deflecting and scanning the light to form a scanning line. The resolution is determined based on the number of rotations.

According to a thirteenth aspect of the present invention, in the optical scanning method for forming an image according to the eleventh aspect, the step of changing the light emission mode of the light emission source comprises deflecting and scanning the light to form a scanning line. If the rotation speed of the rotating polyhedron to be formed is smaller than a predetermined rotation speed, the light emission mode of the light emission source is set to the light amount adjustment light emission mode; otherwise, the light emission mode of the light emission source is set to the constant current light emission mode. It is characterized by doing.

According to a fourteenth aspect of the present invention, a plurality of beams used for image formation are controlled by controlling a light emission source of light incident on a horizontal synchronization signal detecting means when a horizontal synchronization signal is generated. The method comprises the steps of: measuring a light amount of the light emitting source; and changing a light emitting mode of the light emitting source according to the light amount.

According to a fifteenth aspect of the present invention, in the optical scanning method for forming an image according to the fourteenth aspect, the step of changing a light emission mode of the light emission source is performed when the light amount is smaller than a predetermined time. Sets the light emission mode of the light emission source to the light amount adjustment light emission mode, and otherwise sets the light emission mode of the light emission source to the constant current light emission mode.

[0036]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a control unit of an electrophotographic printer according to an embodiment of the present invention. The structure of the mechanism of the electrophotographic printer is the same as that of the above-described conventional example shown in FIG.

In FIG. 1, reference numeral 201 denotes communication and reception of image data with a host computer,
A printer controller that expands received image data into data that can be printed (image formed) by a printer. Further, the printer controller 201 exchanges various control signals (/ CPRDY,
/ PPRDY, / PRNT, / PRFD, / TOP, /
BD, / VDO1, / VDO2, / SCLK, / CM
D, / CBSY, / STS, / SBSY) and serial communication. The engine control unit 202 controls each unit of the printer engine via communication of control signals and serial communication with the printer controller 201 described above.

Reference numeral 203 denotes a stop of the driving of the main motor 210 for conveying the recording paper until the recording paper is fed from the standard cassette 8 and discharged out of the machine, or a predetermined each of them, in response to a print request from the printer controller 201. ON / OFF of the solenoid 211 for driving / stopping the transport roller
A sheet transport control unit that executes control based on an instruction from the engine control unit 202.

Reference numeral 204 denotes a scanner motor 21 for emitting a plurality of lasers L 1 and L 2 based on image data from the printer controller 201 and for driving the rotary polygon mirror 13.
3 to generate a horizontal synchronizing signal / BD signal by rotating
The laser driver 110 is an optical system control unit that executes a process of emitting light at the timing of generating a / BD signal from the D sensor 214 based on an instruction from the engine control unit 202.
And a BD signal detection circuit 120.

A high-voltage control unit 205 outputs high-voltage outputs V1, V2, and V3 for primary charging, development, and transfer based on an instruction from the engine control unit 202. A fixing unit temperature control unit 206 controls the temperature of the fixing unit 7 to a predetermined temperature based on an instruction from the engine control unit 202. The fixing unit 206 detects a change in the resistance value of the thermistor 215 and generates a heater 216 according to the changed value. To generate heat. Reference numeral 207 denotes a sensor input unit for detecting the presence / absence of a sheet in the conveyance path such as a registration and a sheet ejection, and receives detection signals of the registration sensor 10 and the sheet ejection sensor 218.

FIG. 8 is a flowchart showing the control performed by the optical system control section based on the control of the optical scanning device according to the present invention. In the present embodiment, the control instruction to the optical system control unit 202 is performed by a CPU (not shown), but the instruction may be performed by the engine control unit 202.

In step S101, driving of the scanner motor is started, and in step S102, it is determined whether or not the rotation speed of the scanner motor has reached a steady printable rotation speed. If it is determined that the rotation has not been reached, the determination of the number of revolutions is continued until the rotation is reached, and the Wiet operation is repeated. In S103, the laser 1 emits light in the APC mode.

Next, the process waits until two / BD signals are detected (S104, S105). Here, the reason that two / BD signals are detected is that the BD signal detection timing of only the first signal may be detected at a place where the BD sensor should not be originally detected. This is to prevent such erroneous detection because it affects the APC timing in the image area. After the detection of the two signals, the laser 1 is turned off in S106, and after waiting a predetermined time t1 in S107, the laser 2 is caused to emit light in the APC light emission mode for a time t2 in S108.

Next, the laser 1 emits light in the APC mode (S109), and waits until the / BD signal is detected in S110. When the / BD signal (/ BD1 signal) is detected, a timer for measuring a time interval from the / BD1 signal to obtaining the / BD2 signal is started (S11).
1) Turn off the laser 1 (S112), and set the laser 2 to AP
Light emission is performed in the C mode (S113). Here, S106
The reason why the laser 2 is turned on after that and the / BD2 signal is not detected is that the time for performing the APC is insufficient. When the / BD2 signal is detected in S114, the timer is stopped in S115, and the laser 2 is turned off in S116. The timing of turning off the laser 2 is as follows.
The emission time may be determined in advance at the same time as the detection of the / BD2 signal or after a certain time.

Then, the flow shifts to S117, where it is determined whether the obtained timer value is longer or shorter than a predetermined time T1, and if it is longer, the laser 2 emission mode for detecting the subsequent / BD2 signal is changed to APC emission. The mode is set (S118). If it is determined in S117 that it is short, the following /
The laser 2 emission mode for detecting the BD2 signal is set to the ACC emission mode (S119). The ACC light emission mode referred to here is a light emission mode (constant current light emission mode) in which laser light is emitted without performing light amount adjustment.
This is achieved by setting only two signals to the true state.

That is, when the interval between / BD1 and / BD2 is short, the APC time cannot be secured, so that light is emitted in the ACC mode to avoid the effect of overshoot at the light launch portion, and / BD1 to / BD2 Is long, the control to emit light in the APC mode is performed in order to avoid the effect of a decrease in light amount due to droop when the light emission is performed in the ACC mode.

The emission mode of the laser 2 in S126 is determined and controlled based on the emission mode set based on the result of the determination in S112.

As described above, according to the present embodiment, the BD for detecting the / BD signal for both of the two lasers
Since the light incident on the sensor can be stabilized, stable / BD signal detection can be performed.

(Second Embodiment) In the above embodiment, the emission mode of the laser 2 for detecting the / BD2 signal is determined by determining the time interval from the detection of the / BD1 signal to the detection of the / BD2 signal. Although the control is performed, the present invention is not limited to this, and the setting of the light emission mode can be changed using other criteria. Another criterion is, for example, the resolution of the specified print.

Some image forming apparatuses have a high-resolution print mode for the purpose of forming high-quality images. In such an apparatus, when high-resolution printing is designated, the light emission mode can be controlled by the number of revolutions of the scanner motor 213 that drives the rotary polygon mirror 13. In this case, the following operation is performed. Perform

For example, the resolution is usually set to 600 dpi (dot p
er inch), if the resolution is changed and 1200 dpi printing is specified, and if the same image clock is used for image formation, the rotation speed of the scanner motor and The driving speed in the sub-scanning direction (direction perpendicular to the main scanning direction) must be halved.

When the rotation speed of the scanner motor is reduced by half,
Naturally, the time interval from the signal / BD1 to the signal / BD2 is doubled. At this time, in the present embodiment, when the resolution mode is the normal 600 dpi mode, the / BD2 signal detected in the ACC light emission mode is changed to 1200 dpi.
In the case of the mode, it can be switched to detect in the APC light emission mode. That is, by determining whether or not the rotation speed of the scanner motor is equal to or higher than a certain value, it is possible to perform control for setting the emission mode of the laser 2 for detecting the / BD2 signal.

When the printing is performed with the resolution switched, it is necessary to switch the laser light amount. When the amount of laser light is high, the overshoot of light in the initial stage of APC becomes large, and it takes time until the light is stabilized. Therefore,
When the light amount is equal to or more than a certain value, control for setting the light emission mode of the laser 2 for detecting the / BD2 signal to the ACC mode for a certain time can be performed.

(Third Embodiment) In the present embodiment,
The control of prohibiting the timing of switching the emission mode of the laser 2 for detecting the BD2 signal within the same page, that is, the control of switching only between the sheets or before the start of image formation is performed.

For example, when the light emission mode is switched to the optical system control unit by the engine control unit, and the light emission mode is switched before the start of image formation, the engine control is performed after the scanner motor reaches a steady rotation. Until the unit outputs the first sub-scanning synchronization signal (/ TOP signal) to the printer controller, or if the light emission mode is switched between sheets, after the / TOP signal is output, or after the transport time according to the sheet size The switching control is performed only until the next / TOP signal is output. By doing so, it is possible to suppress variations in the writing start position within the same page.

Although the above embodiment has been described assuming an electrophotographic printer, a laser scanning apparatus using a horizontal synchronizing signal detecting circuit according to the present invention is a laser scanning device such as a facsimile or a digital copying machine. The present invention can be used for an image forming apparatus that optically writes an image.

[0057]

As described above, according to the optical scanning device of the present invention, a semiconductor laser having a plurality of light emitting sources for emitting laser light and a semiconductor laser based on a signal PWM-modulated with an image signal are used. A laser driving unit that drives and adjusts the amount of laser light, an optical system control unit that controls the laser driving unit so as to generate a horizontal synchronization signal for all of the plurality of light emitting sources, and a laser driving unit that is provided at a start end on a scanning line of the laser light. And
It is possible to independently and variably set a light emitting mode of a light emitting source which is incident on the horizontal synchronizing signal detecting means for generating a horizontal synchronizing signal and a horizontal synchronizing signal detecting means for detecting a laser beam and outputting a detection signal. Control means, each of the light beams generated from the plurality of light-emitting sources has a / B
In scanning control of image formation by detecting a D signal,
By controlling the light emission mode at the time of incidence on the BD sensor to be switchable so that the light incident on the BD sensor can enter in a stable state, it is possible to form a good image without deviation in the writing position of each beam. .

Further, since the control means is provided with a prohibition so as to further include a control means for performing a control for prohibiting the setting change within the same page, it is possible to suppress the variation of the writing start position within the same page. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a control unit of an electrophotographic printer according to a first embodiment of the present invention.

FIG. 2 is a side perspective view illustrating a configuration of an example of a conventional electrophotographic printer.

FIG. 3 is a block diagram illustrating a configuration of a printer control unit of a conventional electrophotographic printer.

FIG. 4 is a block diagram illustrating control of a multi-laser beam.

FIG. 5 is a timing chart related to APC and / BD signal detection control.

FIG. 6 is a diagram illustrating a laser light distribution, a / BD signal output timing, and a shift on an image in a conventional electrophotographic printer.

FIG. 7: Optical waveform of BD sensor unit, / BD signal output, / AP
It is a figure which shows C1 and / APC2.

FIG. 8 is a flowchart illustrating control performed by an optical system control unit according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2 charging roller 3 optical unit 4 laser beam 5 developing device 6 transfer roller charging device 7 fixing device 8 standard cassette 9 standard cassette feeding roller 10 registration sensor 11 paper ejection sensor 12 paper detection sensor 13 rotating polygon mirror 101, 201 Printer controller 102, 202 Engine control unit 103, 203 Paper transport control unit 104, 204 Optical system control unit 105, 205 High voltage control unit 106, 206 Fixing unit temperature control unit 107, 207 Sensor input unit 110 Laser driver 120 BD signal detection Instrument 210 Main motor 211 Solenoid 213 Scanner motor 214 BD sensor 215 Thermistor 216 Heater

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04N 1/113 B41J 3/00 D 1/23 103 H04N 1/04 104A F term (reference) 2C362 AA32 AA53 AA54 AA61 AA63 AA68 BA35 BA56 BA67 BA69 BB32 BB33 BB38 CB03 CB04 CB05 2H045 AA53 BA02 BA23 BA32 CA88 5C072 AA03 BA04 HA02 HA06 HA12 HB08 HB11 XA01 5C074 AA05 BB03 CC22 DD15 EE02 EE06 HH02 5F073 GA02 EA03

Claims (15)

[Claims] 1. A semiconductor laser having a plurality of light emitting sources for emitting laser light, and a laser driving means for driving the semiconductor laser based on a signal PWM-modulated with an image signal and capable of adjusting an amount of the laser light. An optical system control unit that controls a laser driving unit to generate a horizontal synchronization signal for all of the plurality of light emitting sources, provided at a start end on a scanning line of the laser light,
A horizontal synchronization signal detecting unit that detects the laser beam and outputs a detection signal, and a light emission mode of a light source incident on the horizontal synchronization signal detection unit when the horizontal synchronization signal is generated can be independently and variably set. An optical scanning device for forming an image, comprising: a control unit. 2. A rotating polyhedron for deflecting and scanning the laser light to form a scanning line, a rotation driving unit for rotating the rotating polyhedron, and a photosensitive drum for forming an image on a portion irradiated with the scanning line. The optical scanning device for image formation according to claim 1, further comprising: 3. A light emission mode of a light emission source of light incident on the horizontal synchronization signal detection means when generating the horizontal synchronization signal is one of a light amount adjustment light emission mode and a constant current light emission mode. The optical scanning device for image formation according to claim 1 or 2, wherein: 4. The control means according to claim 1, wherein said control means sets a light emission mode of said light emission source by judging a time interval of a detection signal output from said horizontal synchronization detection means. 3. The optical scanning device for image formation according to item 2. 5. An optical scanning device for image formation according to claim 1, wherein said control means is a control means for setting a light emission mode of said light emission source according to a resolution of an image to be formed. 6. The image forming optical scanning device according to claim 1, wherein the control unit is a control unit that sets a light emitting mode of the light emitting source based on a rotation speed of the rotating polyhedron. 7. The image forming optical scanning device according to claim 1, wherein the control unit is a control unit that sets a light emission mode of the light emission source according to a laser light amount. 8. The optical scanning device for image formation according to claim 1, wherein said control means further comprises control means for performing control for prohibiting a setting change within the same page. 9. An optical scanning method for controlling a plurality of beams used for image formation by controlling a light source of light incident on a horizontal synchronizing signal detecting means when generating a horizontal synchronizing signal, wherein An optical scanning method for forming an image, comprising: measuring a time interval at which a synchronization signal is detected; and changing a light emitting mode of a light emitting source according to a length of the time interval. 10. The step of changing a light emission mode of the light emission source, wherein the light emission mode of the light emission source is set to a light amount adjustment light emission mode when the time interval is longer than a predetermined time; 10. The optical scanning method for forming an image according to claim 9, wherein the light emitting mode of the light emitting source is set to a constant current light emitting mode. 11. A method for controlling a plurality of beams used for image formation by controlling a light emitting source of light incident on a horizontal synchronization signal detecting means when generating a horizontal synchronization signal, the method comprising: Measuring the resolution of the image and changing the light emission mode of the light emitting source according to the resolution. 12. The method according to claim 1, wherein in the step of measuring the resolution, the resolution is determined based on the number of rotations of a rotating polyhedron forming a scanning line by deflecting and scanning the light.
2. The optical scanning method for forming an image according to item 1. 13. The light emitting mode of the light emitting source is changed when a rotational speed of a rotating polyhedron forming a scanning line by deflecting and scanning the light is smaller than a predetermined rotational speed. 12. The optical scanning method for image formation according to claim 11, wherein the light emission mode of the light emitting source is set to a constant current light emission mode in other cases. 14. A method of controlling a plurality of beams used for image formation by controlling a light emitting source of light incident on a horizontal synchronization signal detecting means when generating a horizontal synchronization signal, wherein An optical scanning method for forming an image, comprising: measuring a light amount; and changing a light emission mode of the light emitting source according to the light amount. 15. The method of changing the light emission mode of the light emission source, wherein the light emission mode of the light emission source is set to a light amount adjustment light emission mode when the light amount is smaller than a predetermined time;
15. The optical scanning method for forming an image according to claim 14, wherein the light emitting mode of the light emitting source is set to a constant current light emitting mode in other cases.