JPH1020736A - Image forming device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the color shift of an output image along an auxiliary scanning direction, in a color image forming device having a plurality of scanning optical systems. SOLUTION: A plurality of scanning optical systems are synchronously controlled by PLL control circuits 55, 56, and color shift correcting control is performed by a color shift correcting control part 51 so that the distance from the end of a transfer material to the image reading position of the optical scanning system is constant for each rotation. A scanner motor 8 is rotated by a scanner clock signal, an FG signal is obtained as information about the rotation of the motor, and the PLL control circuit 55 performs control to accelerate or decelerate the motor 8 so that the phase difference between the scanner clock signal and the FG signal is held constant. An FG signal of the first optical scanning system is also input to the PLL control circuit 56 of the second scanning optical system to control the scanner motor 9 likewise. The color shift correcting control part 51 measures the phase difference between a TOP signal and a BD signal and controls the rotating speed of the motor 50 that drives the transfer drum, so as to hold the phase difference within a certain range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for sequentially transferring a plurality of color visible images sequentially formed on an image carrier (for example, a photosensitive drum) onto a transfer material (for example, paper). And an image forming method.

More specifically, the present invention relates to a first optical scanning means for deflecting a laser beam modulated according to an odd-numbered row of image signals by a first rotary polygon mirror and guiding the laser beam to an image carrier for optical scanning. And a second light for deflecting the laser beam modulated according to the image signals of the even rows independently of the first optical scanning means by the second rotary polygon mirror and guiding the laser beam to the image carrier for optical scanning. The present invention relates to a technology for preventing color misregistration such as a color laser beam printer having a scanning unit.

[0003]

2. Description of the Related Art In a color image forming apparatus in which a full-color image is obtained by multiplex-transferring a plurality of color toner images onto the same transfer material, there is a problem that the overlapping position of each color is shifted during the multiplex transfer. Yes, there is a need for improvement.

In order to solve such a problem, a method of controlling the transfer system in synchronization with the scanning optical system for each color and keeping the transfer position from the leading end of the transfer material within a predetermined range is considered. Have been.

[0005]

In recent years, laser printers have been required to operate at a higher speed, and various mechanical configurations corresponding to the higher speed have been considered. As one of them, a method of increasing the speed of horizontal scanning by providing a plurality of scanning optical systems has recently been often proposed. Therefore, it is necessary to perform color misregistration correction control for a color image forming apparatus having such a plurality of scanning optical systems.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to form an image having a plurality of scanning optical systems and capable of preventing the occurrence of misregistration between colors during multiple transfer. An object of the present invention is to provide an apparatus and an image forming method.

[0007]

In order to achieve the above object, the present invention provides an FG (frequency) which is a rotation information signal of a motor for driving a rotary polygon mirror in a first scanning optical system.
generation) signal to control the phase difference from the reference clock signal to be minimized, thereby controlling the rotation to be stable. At this time, the FG signal is sent to the second scanning optical system, and the first scanning optical system is sent to the first scanning optical system. Similarly to the scanning optical system, the rotary polygon mirror is controlled to perform synchronization control of the first and second scanning optical systems, and further, color shift correction control is performed by controlling the phase of the first scanning optical system and the transfer driving system. Thus, the phase control of the second scanning optical system and the transfer driving system is inevitably performed, and the color shift is corrected.

More specifically, the image forming apparatus of the present invention deflects a laser beam modulated in accordance with a first image signal by a first rotating polygon mirror and guides the laser beam to an image carrier to guide the image carrier. A first optical scanning unit for optically scanning, and independently of the first optical scanning unit, a laser beam modulated in accordance with a second image signal is deflected by a second rotary polygon mirror, and is illuminated on the image carrier. Second optical scanning means for guiding and optically scanning the image carrier, and developing the latent image formed on the image carrier by the first optical scanning means and the second optical scanning means with a plurality of recording materials. A developing means group, a transfer support for supporting and transporting the transfer material, and transferring the visible image on the image carrier obtained by the development of the developing means group to the same transfer after each development of each recording material. Color image forming apparatus having transfer means for transferring onto a material A first detecting means for detecting a rotation of a motor for driving the first rotary polygon mirror of the first optical scanning means; a second detecting means for detecting a rotational position of the transfer support; Synchronous control means for synchronously controlling the first optical scanning means and the second optical scanning means with respect to the first detection output outputted from the detecting means, and the first detection output outputted from the first detecting means, Phase difference detecting means for detecting a phase difference of a second detection output outputted from the second detecting means, and the first signal based on an output signal of the phase difference detecting means.
A reference signal of a drive signal of a motor for driving the transfer support so that a phase difference between the first detection output output from the detection means and the second detection output output from the second detection means falls within a predetermined range. And a reference signal generating means for variably controlling the frequency.

According to another aspect of the image forming apparatus of the present invention, a laser beam modulated in accordance with a first image signal is deflected by a first rotating polygonal mirror, and guided to an image carrier to carry the image carrier. A first optical scanning unit for optically scanning a body, and independently of the first optical scanning unit, a laser beam modulated according to a second image signal is deflected by a second rotary polygon mirror, and the image carrier A second optical scanning unit that guides the image carrier to the body and optically scans the image carrier, and develops a latent image formed on the image carrier by the first optical scanning unit and the second optical scanning unit with a recording material. An image forming apparatus comprising: a developing unit; a transfer support that supports and transports a transfer material; and a transfer unit that transfers a visible image on the image carrier obtained by development by the developing unit onto the transfer material. In the first,
First detecting means for detecting the rotation of a motor for driving the first rotating polygonal mirror of the optical scanning means, second detecting means for detecting the rotational position of the transfer support, and second output means for outputting from the first detecting means. Synchronization control means for controlling the first light scanning means and the second light scanning means in synchronization with one detection output; the first detection output outputted from the first detection means;
Phase difference detection means for detecting a phase difference between second detection outputs output from the detection means, and the first detection output and the second detection output from the first detection means based on an output signal of the phase difference detection means A reference signal generating means for generating a reference signal of a drive signal of a motor for driving the transfer support by variably controlling a frequency so that a phase difference of the second detection output outputted from the means falls within a predetermined range; Is provided.

In a preferred embodiment of the apparatus according to the present invention, the first image signal is an odd-numbered image signal and the second image signal is an even-numbered image signal. be able to. Further, there is provided a light detecting means arranged on a scanning axis line of the laser beam, and the synchronization control means comprises a first detecting means for outputting the first light from the first detecting means.
First PLL control means for controlling acceleration and deceleration of a motor for driving the first rotary polygon mirror so that a phase difference between a detection output and a BD signal output from the light detection means is always constant; and the first detection means A second PLL control means for controlling acceleration and deceleration of a motor for driving the second rotary polygon mirror so that the phase difference between the first detection output output from the first detection output and the BD signal output from the light detection means is always constant. It can be characterized by having.

Further, the reference signal generation means starts counting with the second detection output output from the second detection means, stops counting with the BD signal output from the light detection means, and counts the count. Counter means for outputting a value as phase difference information between the second detection output and the BD signal; counter clock generation means for generating a clock for driving the counter means; And a transfer-system motor clock generating means for variably generating a drive clock frequency which is a reference signal of a drive signal of a motor for driving the transfer support. Then, the counter means outputs the phase difference information as the number of pulses. If the cycle of the pulse train is t and the number of counted pulses is n, the phase difference to be obtained is t × n. The means may be characterized in that the driving clock is switched to a clock signal having a cycle longer by t than a normal clock signal generated in advance, the number being counted n times. Further, the reference signal generating means may perform variable control of the frequency of the reference signal in a non-print area.

In order to achieve the above object, an image forming method according to the present invention is characterized in that a laser beam modulated in accordance with a first image signal, which is an odd-numbered row of image signals, is deflected by a first rotary polygon mirror, and an image bearing image is formed. A first optical scanning means for guiding the image carrier to the body by optically scanning the image carrier, and a laser beam modulated according to a second image signal which is an image signal of an even-numbered row independently of the first optical scanning means Is deflected by a second rotating polygon mirror, and is guided to the image carrier to optically scan the image carrier. The first optical scanning device and the second optical scanning device perform image scanning by the first optical scanning device and the second optical scanning device. A developing unit for developing the latent image formed on the body with a plurality of recording agents; a transfer support for supporting and transporting the transfer material; and a developing unit on the image carrier obtained by developing the developing unit. After each development of each recording agent, the visible image A color image forming method for a color image forming apparatus having a transfer means for transferring the image on a material, wherein a first detection step of detecting rotation of a motor for driving the first rotary polygon mirror of the first optical scanning means; A second detecting step of detecting a rotational position of the transfer support;
The first detection output obtained in the detection step is the first detection output.
A synchronous control step of synchronously controlling the optical scanning means and the second optical scanning means; and a first detection output obtained in the first detection step and a second control output obtained in the second detection step.
Based on the phase difference detection step of detecting the phase difference of the detection output, based on the phase difference detected in the phase difference detection step,
A motor for driving the transfer support so that a phase difference between the first detection output obtained in the first detection step and the second detection output obtained in the second detection step falls within a predetermined range; Generating a reference signal of the drive signal by variably controlling the frequency.

As a preferred embodiment, the method of the present invention includes a light detecting step of detecting the laser beam by a light detecting means arranged on a scanning axis of the laser beam and outputting a BD signal, The synchronous control step includes: a first PLL control step of performing control for accelerating and decelerating a motor that drives the first rotary polygon mirror such that a phase difference between the first detection output and the BD signal is always constant. A second PLL control step of performing control for accelerating and decelerating a motor for driving the second rotary polygon mirror so that a phase difference between the first detection output and the BD signal is always constant.

In the reference signal generating step, the counting is started with the second detection output, the counting is stopped with the BD signal, and the count value is used as phase difference information between the second detection output and the BD signal. And a transfer system motor that generates by changing the frequency of a drive clock that is a reference signal of a drive signal of a motor that drives the transfer support in accordance with the phase difference information obtained in the counter step. And a clock generation step. Then, the counter step outputs the phase difference information as the number of pulses, the period of the pulse train is t, and the number of counted pulses is n,
The phase difference to be obtained is t × n, and the transfer system motor clock generation step converts the drive clock into a clock signal having a cycle longer than the normal clock signal generated in advance by t, by the counted n times, Switching can be characterized.

A storage medium storing a program represented by software for achieving the image forming method is included in the present invention.

[0016]

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

FIG. 1 shows an example of a schematic configuration of a color image forming apparatus to which the present invention is applied. The photosensitive drum 2 is charged to a predetermined polarity and a predetermined voltage by the charger 1, and the recording paper P stored in the cassette 3 is fed one by one at a predetermined timing by the feed roller 4. And the recording paper P
Is detected by the paper edge detector 5, the image signals VDO1 and VDO2 for one page are output to the semiconductor laser diodes 6 and 7, respectively, and the laser light whose ON / OFF is controlled by the image signal VDO is Polygon mirrors 10, which are rotationally driven by scanner motors 8, 9,
It is emitted toward 11. The emitted laser light is horizontally scanned on the photosensitive drum 2 by the polygon mirrors 10 and 11, the lenses 12 and 13, and the mirror 14. When the laser beam L is emitted, the laser beam is detected by the photodetectors 15 and 16 arranged on the scanning axis of the beam, and the detection signal is output as a beam detection signal BD serving as a horizontal synchronization signal. Is done. As a result, the laser beam L scans and exposes the photosensitive drum 2 in synchronization with the beam detect signal BD, and a first electrostatic latent image is formed.
Next, the first electrostatic latent image is developed by the developing device 17M, and a magenta first toner image is formed on the photosensitive drum 2.

On the other hand, immediately before the recording paper P reaches the transfer start position, a predetermined transfer bias voltage having a polarity opposite to that of the toner is applied to the transfer drum 18, and the first toner image is transferred onto the recording paper P, and the recording is performed at the same time. The paper P is electrostatically attracted to the transfer drum 18. After the transfer, the untransferred toner image remaining on the photosensitive drum 2 is scraped off by the cleaner 19.

Next, a second electrostatic latent image is formed on the photosensitive drum 2 by the laser beam L, and the formed second electrostatic latent image is developed by the developing device 17C. Two toner images are formed. This second toner image is transferred to the same recording paper P in accordance with the position of the first toner image previously transferred to the recording paper P.

Similarly, a third electrostatic latent image is formed on the photosensitive drum 2, the formed electrostatic latent image is developed by the developing unit 17Y, and the yellow toner image is recorded in the same position with the same alignment. It is transferred to paper P.

Similarly, a fourth electrostatic latent image is formed on the photosensitive drum 2, and the formed electrostatic latent image is
k, and the black toner image is transferred to the same recording paper P with the same alignment.

Thereafter, the recording paper P to which the four color toner images have been transferred is separated from the recording paper P by the separation claw 20 and the accumulated charge is reduced in order to reduce air discharge at the time of separation. Is removed by the charger 21. Then, when the leading end of the recording paper P approaches the position of the separation claw 20, the separation claw 20 approaches the transfer drum 18 at a predetermined timing and comes into contact with the surface of the transfer drum 18 to maintain this contact state. as a result,
The recording paper P is separated from the leading edge of the paper. Thereafter, when the rear end of the recording paper P is separated from the transfer drum 18, the separation claw 20 separates from the transfer drum 18 and retreats to the original position. Then, the separated recording paper P is heat-fixed under pressure by the fixing device 22, and is discharged onto a paper discharge tray 23.

Next, the operation of the laser beam scanning device constituting the laser beam printer will be described with reference to FIG. The reference clock output from the reference oscillator 30 is divided by the frequency divider 31 and supplied to the motor control circuit 32. The motor control circuit 32 incorporates a known phase control circuit (not shown) and controls the scanner motor 8 so that the phase difference between the input divided clock and the feedback signal from the scanner motors 8 and 9 becomes a predetermined phase difference. , 9 are controlled to rotate at a constant speed.

Next, the timing of writing an image will be described with reference to FIG. When the transfer drum 18 is rotated at a constant speed by a drive motor (not shown) and the leading end of the recording paper P on the transfer drum 18 is detected by the detector 5, a vertical synchronization signal VSYNC is output from the detector 5 to the image generator 40. Is output to The image generating device 40 has a vertical synchronization signal VSYNC.
, The image signals VDO1 and VDO2 are synchronized with the beam detection signals BD detected by the detectors 15 and 16, and the synchronized image signals VDO1 and VDO2 are sequentially transmitted to lasers (semiconductor laser diodes) 6 and 7. I do.

FIG. 4 shows the vertical synchronizing signal VSYN at this time.
C, the output timing of the horizontal synchronization signal HSYNC (that is, the beam detect signal BD) and the output timing of the image signal VDO.

In the present invention, as in the color image forming apparatus shown in FIG. 1, in a system in which the first scanning optical system and the second scanning optical system are independent, the polygon mirror 10 obtained from the first scanning optical system is used. A PLL control circuit (not shown, a well-known circuit) such that the phase difference between the FG signal that is the rotation information of the scanner motor 8 to be rotated and the scanner clock signal of the other second scanning optical system is a predetermined phase difference. By performing control using a phase control circuit), synchronous control of both scanning optical systems is performed. Furthermore, the phase control of the clock signal of the transfer system drive motor is performed on the first scanning optical system so that the writing start positions of the respective colors coincide with each other during printing. This means that the shift correction has been performed.

FIG. 5 shows a circuit configuration of a main part of an embodiment of the present invention. In the configuration of FIG. 5, when the printing operation is started, the respective scanner motors (polygon motors) 8 and 9 of the first scanning optical system and the second scanning optical system start rotating.

In the first scanning optical system, the scanner motor 8 rotates according to the scanner clock signal generated from the scanner clock generation circuit 53. When the scanner motor 8 starts rotating, an FG signal as motor rotation information is obtained from a sensor (not shown) according to the rotation of the motor. The PLL control circuit 55 controls the acceleration / deceleration of the scanner motor 8 via the scanner clock generation circuit 53 so that the phase difference between the scanner clock signal and the FG signal is always constant.

The FG signal obtained by the first scanning optical system is
Also input to the PLL control circuit 56 of the scanning optical system, the PLL
Similarly to the first scanning optical system, the control circuit 56 controls the second scanning via the scanner clock generation circuit 54 so that the phase difference between the scanner clock signal generated from the scanner clock generation circuit 54 and the FG signal becomes constant. The acceleration / deceleration control of the scanner motor 9 of the optical system is performed. With the above control, the polygon mirror 11 of the second scanning optical system rotates in synchronization with the polygon mirror 10 of the first scanning optical system.

When image data is sent from a host device (for example, a personal computer or an image reading device), the semiconductor laser diodes 6 and 7 flash according to the image data, and these laser diodes 6 and 7 are turned on and off.
Laser beams emitted from the polygon mirrors 10 and 1
1. Deflected by the lenses 12 and 13 to scan on the photosensitive drum (photoconductor) 2 to form an electrostatic latent image on the photosensitive drum 2. At this time, the data of the first line of the image data is processed by the first scanning optical system, and at the same time, the data of the second line is processed by the second scanning optical system. Similarly, the data of the third line is processed by the first scanning optical system,
At the same time, the odd lines are processed by the first scanning optical system, and the even lines are processed by the second scanning optical system, such that the data of the fourth line is processed by the second scanning optical system.

In FIG. 1, the paper edge detector 5 is a recording paper P
When the leading end position of the (transfer material) is detected, a TOP signal used as a vertical synchronization signal for image recording is output. Also,
BD signal detectors (photodetectors) 15 and 16 output BD signals used as horizontal synchronization signals for image printing.

The color misregistration correction control unit 51 shown in FIG.
The transfer system drive motor 5 that drives the transfer drum 18 in the non-print area so as to eliminate the phase difference between the TOP signal and the BD signal by measuring the phase difference between the signal and the BD signal.
0 rotation speed is controlled.

That is, the color misregistration correction control section 51 generates a pulse train of a predetermined cycle inside the color misregistration correction control section 51, and measures the phase difference between the TOP signal and the BD signal by counting the pulses. In this embodiment, the color misregistration correction control unit 51 starts counting when a TOP signal is generated, and stops counting when a BD signal is generated, thereby outputting the phase difference as the number of pulses. Here, assuming that the period of the pulse train is t and the number of counted pulses is n, the phase difference to be obtained is t × n. Thereafter, the color misregistration correction control unit 51 switches the drive clock of the transfer system drive motor 50 to a clock signal having a cycle longer by t than a previously generated normal clock signal, for n counts. Due to the characteristic of the pulse motor that the timing of rotation changes according to the change in pulse length, the period is set to t
Since the rotation timing of the transfer system drive motor 50 changes due to the change in the pulse length of the clock signal
The phase difference between the TOP signal and the BD signal can be corrected within a predetermined range.

FIG. 6 is a diagram showing in detail the phase difference detecting section inside the color misregistration correction control section 51 of FIG. The counter oscillation circuit 60 is an oscillation source of a clock for driving the counter 61. The counter 61 starts counting when a TOP signal is input, stops counting when a BD signal is input, and outputs a count value CNTOUT as phase difference information between the two signals. The transfer motor clock oscillation circuit 62 counts the count value C
Detecting NTOUT, oscillates the clock of the transfer system drive motor 50 and sends it to the pulse motor drive circuit 63.

(Other Embodiments) In the above-described embodiment of the present invention, an image forming apparatus having first and second optical scanning means (scanning optical system) has been exemplified. The present invention can be similarly applied to an image forming apparatus having the same.

The present invention is not limited to a color image forming apparatus, but can be applied to a monochrome image forming apparatus.

The image forming apparatus of the present invention is not limited to a printer, but can be applied to a digital copying machine, a facsimile machine, a ticket issuing machine and the like.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus. In this case, by reading a storage medium storing a program represented by software for achieving the present invention into the system or the apparatus, the system or the apparatus can enjoy the effects of the present invention. Becomes

[0039]

As described above, according to the present invention,
In a color image forming apparatus using multiple independent scanning optical systems, the scanning optical system is controlled synchronously, and the distance from the leading edge of the transfer material to the image writing position of the scanning optical system is constant at every rotation. Since it is configured to perform misregistration correction control, the scanning optical system can form an image faster than one apparatus, and the color misregistration of the output image in the sub-scanning direction can be suppressed to the minimum. The effect is obtained that the print quality (print quality) of the apparatus can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of the structure of a color image forming apparatus to which the present invention is applied.

FIG. 2 is a block diagram illustrating a schematic configuration of a motor drive control circuit of the scanning optical system of FIG. 1;

FIG. 3 is a block diagram illustrating a control circuit of an image generation timing in the color image forming apparatus of FIG. 1;

FIG. 4 is a timing chart showing timings of signals of respective units shown in FIG. 3;

FIG. 5 is a block diagram showing a circuit configuration of one embodiment of the present invention.

FIG. 6 is a block diagram illustrating a detailed configuration of a color misregistration correction control unit in FIG. 5;

[Explanation of symbols]

 2 Photosensitive drum (image carrier) 5 Paper edge detector 6,7 Semiconductor laser diode 8,9 Scanner motor (polygon motor) 15,16 Photodetector 17M, 17C, 17Y, 17Bk Developing device 18 Transfer drum (transfer support) 20) Separating claw 30 Reference oscillator 31 Divider 32 Motor control circuit 40 Image generation device 50 Transfer system drive motor 51 Color misregistration correction control unit 53, 54 Scanner clock generation circuit 55, 56 PLL control circuit 60 Counter oscillation circuit 61 Counter 62 Transfer system motor clock oscillation circuit 63 Pulse motor drive circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G03G 15/16 G03G 15/16

Claims (12)

[Claims] 1. A first optical scanning means for deflecting a laser beam modulated according to a first image signal by a first rotating polygon mirror, guiding the laser beam to an image carrier and optically scanning the image carrier, Independently of the first optical scanning means, the laser beam modulated according to the second image signal is deflected by the second rotating polygon mirror and guided to the image carrier to optically scan the image carrier. Two light scanning means; a developing means group for developing a latent image formed on the image carrier by the first light scanning means and the second light scanning means with a plurality of recording materials; A color having a transfer support that conveys, and a transfer unit that transfers a visible image on the image carrier obtained by development of the development unit group onto the same transfer material after each development of each recording material. An image forming apparatus, wherein: First detecting means for detecting the rotation of a motor for driving a rotating polygon mirror; second detecting means for detecting a rotational position of the transfer support; and a first detecting output from the first detecting means. Synchronization control means for synchronously controlling the first light scanning means and the second light scanning means; and a position of the first detection output outputted from the first detection means and a second detection output outputted from the second detection means. Phase difference detection means for detecting a phase difference; and a position of the first detection output output from the first detection means and the second detection output output from the second detection means, based on an output signal of the phase difference detection means. An image forming apparatus comprising: a reference signal generating unit configured to variably control a frequency of a reference signal of a driving signal of a motor for driving the transfer support so as to keep a phase difference within a predetermined range. . 2. A first optical scanning means for deflecting a laser beam modulated according to a first image signal by a first rotary polygon mirror, guiding the laser beam to an image carrier and optically scanning the image carrier, Independently of the first optical scanning means, the laser beam modulated according to the second image signal is deflected by the second rotating polygon mirror and guided to the image carrier to optically scan the image carrier. Two light scanning means; developing means for developing a latent image formed on the image carrier by the first light scanning means and the second light scanning means with a recording material; transfer for supporting and transporting a transfer material An image forming apparatus comprising: a support; and a transfer unit that transfers a visible image on the image carrier obtained by development by the developing unit onto the transfer material, wherein the first rotation of the first optical scanning unit is performed. Detects rotation of motor driving polygon mirror First detecting means, second detecting means for detecting a rotational position of the transfer support, first light scanning means and second light scanning for a first detection output outputted from the first detecting means. Synchronous control means for synchronously controlling the means; phase difference detecting means for detecting a phase difference between the first detection output outputted from the first detection means and a second detection output outputted from the second detection means; Based on an output signal of the phase difference detection means, a phase difference between the first detection output output from the first detection means and the second detection output output from the second detection means is set within a predetermined range, An image forming apparatus comprising: a reference signal generating unit that generates a reference signal of a drive signal of a motor for driving the transfer support by variably controlling a frequency. 3. The image forming apparatus according to claim 1, wherein the first image signal is an odd-numbered row image signal, and the second image signal is an even-numbered row image signal. 4. A light detecting means disposed on a scanning axis of the laser beam, wherein the synchronization control means outputs the first detection output from the first detecting means and an output from the light detecting means. A first PLL control means for controlling acceleration and deceleration of a motor for driving the first rotary polygon mirror so that a phase difference between the BD signals is always constant; and a first detection output outputted from the first detection means. A second PLL control means for controlling acceleration and deceleration of a motor for driving the second rotary polygon mirror so that a phase difference of a BD signal output from the light detection means is always constant. An image forming apparatus according to any one of claims 1 to 3. 5. The reference signal generation means starts counting with the second detection output output from the second detection means, stops counting with the BD signal output from the light detection means, and counts the count value. Counter means for outputting as a phase difference information between the second detection output and the BD signal; counter clock generating means for generating a clock for driving the counter means; and responding to the phase difference information output from the counter means. 5. The image forming apparatus according to claim 4, further comprising: a transfer system motor clock generating unit configured to generate a variable frequency of a drive clock as a reference signal of a drive signal of a motor for driving the transfer support. . 6. The counter means outputs the phase difference information as the number of pulses. If the period of the pulse train is t and the number of counted pulses is n, the phase difference to be obtained is t × n. 6. The image according to claim 5, wherein the motor clock generating means switches the drive clock to a clock signal having a cycle longer by t than a normal clock signal generated in advance, for n times counted. Forming equipment. 7. The image forming apparatus according to claim 1, wherein said reference signal generating means executes variable control of the frequency of said reference signal in a non-print area. 8. A laser beam modulated in accordance with a first image signal, which is an image signal of an odd-numbered row, is deflected by a first rotating polygon mirror, and is guided to an image carrier to optically scan the image carrier. A first optical scanning unit, independently of the first optical scanning unit, a laser beam modulated in accordance with a second image signal, which is an image signal of an even-numbered row, is deflected by a second rotating polygon mirror, and A second optical scanning unit that guides the image carrier to the carrier and optically scans the image carrier; and a plurality of recording agents that transfer the latent image formed on the image carrier by the first optical scanning unit and the second optical scanning unit. A developing means group for developing with a transfer material, a transfer support for supporting and transporting a transfer material, and a visible image on the image carrier obtained by development of the developing means group after each development of each recording material. Transfer means for transferring onto the transfer material of In the color image forming method of the forming apparatus, a first detecting step of detecting a rotation of a motor for driving the first rotary polygon mirror of the first optical scanning means, and a second detecting step of detecting a rotational position of the transfer support A synchronous control step of synchronously controlling the first optical scanning means and the second optical scanning means with respect to the first detection output obtained in the first detecting step; A phase difference detecting step of detecting a phase difference between the obtained first detection output and the second detection output obtained in the second detection step; and A drive signal for a motor driving the transfer support so that a phase difference between the first detection output obtained in the first detection step and the second detection output obtained in the second detection step falls within a predetermined range. Standards of Image forming method characterized by having a reference signal generation step of generating by variably controlling the frequency of the issue. 9. A light detection step of detecting the laser beam by a light detection means arranged on a scanning axis of the laser beam and outputting a BD signal, wherein the synchronization control step includes: And the BD
A first PLL for controlling acceleration and deceleration of a motor for driving the first rotary polygon mirror so that a signal phase difference is always constant.
Control step; and a second PLL control step of performing control for accelerating and decelerating a motor for driving the second rotary polygon mirror so that a phase difference between the first detection output and the BD signal is always constant. The image forming method according to claim 8, wherein 10. The reference signal generating step starts counting with the second detection output, stops counting with the BD signal, and counts the count value as phase difference information between the second detection output and the BD signal. A transfer step motor that generates a drive clock frequency that is a reference signal of a drive signal of a motor that drives the transfer support in accordance with the phase difference information obtained in the counter step. The image forming method according to claim 9, further comprising a clock generating step. 11. The counter step outputs the phase difference information as the number of pulses. If the period of the pulse train is t and the number of counted pulses is n, the phase difference to be obtained is t ×
n, wherein the transfer system motor clock generating step switches the driving clock to a clock signal having a cycle longer by t than a normal clock signal generated in advance by n times counted. The image forming method according to claim 10. 12. A storage medium storing a program represented by software for achieving the image forming method according to claim 8. Description: