JP4103386B2 - Multi-beam optical scanning method and image forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device used as an image writing means in an image forming apparatus such as an electrophotographic printer such as a laser printer, an electrophotographic copying machine, or a laser facsimile, and more particularly to a plurality of scanning lines simultaneously on a surface to be scanned of a photoreceptor. The present invention relates to a multi-beam optical scanning provided with a plurality of laser light sources for scanning.
[0002]
[Prior art]
Conventionally, there has been proposed a multi-beam optical scanning device as described in JP-A-10-177145. The multi-beam optical scanning device includes a synchronization signal detecting unit and an adjusting unit that mechanically moves the light source to adjust a shift, and uses one of the plurality of light beams as a reference light beam, A reference light beam is sequentially combined, and a scanning timing shift of each light is detected according to a time width in which the combined light beam passes through the synchronization detection unit, and the position of the light beam is detected by the adjustment unit according to the shift amount. Is configured to adjust the deviation of the scanning timing.
[0003]
[Problems to be solved by the invention]
However, the multi-beam optical scanning device detects the amount of change after moving the adjustment mechanism without considering the order of which beam precedes when the optical beam shift occurs. There was a problem that it was necessary. Further, regarding the correction of the deviation amount, a light beam position adjustment mechanism is necessary, the structure is complicated and expensive, and the adjustment work is complicated, so that the adjustment work is complicated. Yes.
[0004]
The first object of the present invention is to eliminate such drawbacks of the prior art and detect the timing shift amount of a plurality of beams emitted from a plurality of light sources and the beam order indicating which beam precedes. An object is to provide an inexpensive multi-beam optical scanning method .
[0005]
The second object of the present invention is that there is no deviation in the main scanning direction without using an adjustment mechanism that mechanically adjusts the position of the light source based on the detected deviation amounts of the plurality of light beams and the order of the light beams. An object of the present invention is to provide an image forming method capable of forming an image .
[0006]
[Means for Solving the Problems]
In order to achieve the first object, the first means of the present invention is a multi-stage including at least a first light source and a second light source for simultaneously scanning a plurality of light beams in the main scanning direction on the photosensitive member. A beam light emitting means, a light deflecting means for scanning a plurality of light beams emitted from the multi-beam light emitting means in the main scanning direction, and a light receiving element, and a light beam emitted from the multi-beam light emitting means. The present invention is intended for a multi-beam optical scanning method of a multi-beam optical scanning device that includes synchronization detection means that receives light at a predetermined position and detects scanning position timing.
[0007]
Then, the first light source is turned on, the first time interval ta passing through the synchronization detecting means is measured, and then the first light source and the second light source are turned on at the same time, and the previous light beam is received. The second light source is turned off after a predetermined time t1 shorter than the first time width ta after the output of the synchronization detection means changes, and then the light beam of the first light source passes through the synchronization detection means. Measure the second time tb until the end,
Further, the first light source and the second light source are turned on at the same time, the first light beam is received, and the output of the synchronization detecting means is changed. Then, after a predetermined time t1 shorter than the first time width ta, the first light source is changed. A third time tc until the light beam of the second light source finishes passing through the synchronization detection means,
The difference between the first time width ta, the second time width tb, and the third time width tc is calculated,
When tb <tc, it is determined that the scanning with the light beam of the first light source precedes the scanning with the light beam of the second light source, and the timing deviation amount Δt of the scanning with the light beam is set to Δt = tc−ta Calculated by
When tb> tc, it is determined that the scanning by the light beam of the second light source precedes the scanning by the light beam of the first light source, and the timing deviation amount Δt of the scanning by the light beam is set to Δt = tb−ta It is characterized by calculating by .
[0008]
In order to achieve the second object, according to a second means of the present invention, in the image forming method, the horizontal shift is performed according to the timing deviation amount calculated by the multi-beam light scanning method of the first means and the order of the light beams. A synchronization signal is output, and an image signal is generated in synchronization with the horizontal synchronization signal .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an image forming apparatus according to the embodiment, and FIG. 2 is a schematic diagram showing a positional relationship between a photoconductor and a synchronization detection unit.
[0013]
In the image forming apparatus of the present invention, the surface of the photoreceptor 20 is uniformly charged by a charger (not shown), and is exposed to two laser beams emitted from the multi-beam light emitting means 2 to be belt-shaped or drum-shaped photosensitive. An electrostatic latent image is formed on the surface of the body 20. As shown in FIG. 2, the laser light emitted from the multi-beam light emitting means 2 passes through the collimator lens 23 and is reflected by the optical deflector 21. The optical deflector 21 has a plurality of planar mirror surfaces in the circumferential direction, is driven to rotate at a constant speed by an optical deflection motor 22, and the reflected laser light is scanned in the main scanning direction 24.
[0014]
The synchronization detection means 1 has one light receiving element, and its position in the main scanning direction 24 is fixed near the photoconductor 20, and detects the position of the laser beam to be main scanned with respect to the photoconductor 20. A reference timing signal for generating a horizontal synchronizing signal indicating the scanning direction timing of the image signal is output.
[0015]
The multi-beam light emitting means 2 has a plurality of light emitting elements, and in this embodiment, has two light emitting elements, a laser diode A6 and a laser diode B7. The on / off control means 3 controls the turning on / off of the laser diode A6 and the laser diode B7. In the present embodiment, during the horizontal synchronization period in which the photoconductor 20 is exposed, the laser diode A6 is on / off controlled by the image signal A8, and the laser diode B7 is on / off controlled by the image signal B9 to form an image. The laser diode A6 and the laser diode B7 are forcibly set by the on / off control means 3 in order to detect the position of the laser light during a period from a predetermined time before the laser light passes before the synchronous detection means 1 to after the passage. Is lit.
[0016]
The positions at which the laser beams emitted from the laser diodes A6 and B7 form an image on the photosensitive member 20 and on the synchronization detecting means 1 are separated by one scanning line interval in the sub-scanning direction, and are substantially scanned in the main scanning direction. Are arranged vertically. Accordingly, the two laser beams pass in front of the synchronization detecting means 1 almost simultaneously, and one position detection pulse is output in one main scan.
[0017]
At this time, if the positions of the two laser beams in the main scanning direction are completely perpendicular to the scanning line, the horizontal synchronization signals for the respective image signals may be at the same timing. However, a slight misalignment occurs due to an error in the mounting angle of the multi-beam light emitting means 2.
[0018]
Here, a method of detecting the positional deviation between the laser diode A6 and the laser diode B7 in the main scanning direction will be described with reference to the block diagram of FIG. 1 and the timing charts of FIGS.
[0019]
3 to 5, LDA 31 indicates the on / off state of laser diode A 6, LDB 32 indicates the on / off state of laser diode B 7, the low level is off, and the high level is on. PD33 indicates the state of the output signal of the synchronization detection means 1.
[0020]
When the light deflection motor 22 rotates to reach a predetermined rotational speed, one of the lasers of the multi-beam light emitting means 2 is turned on [timing (a)]. Here, the laser diode A6 is turned on. At this time, since the scanning position of the laser is unknown, the timing (a) in FIG. 3 is an arbitrary timing.
[0021]
When the light emitted from the laser diode A6 that is main-scanned by the rotation of the optical deflector 21 reaches the synchronization detection means 1, the output of the synchronization detection means 1 changes at the timing (b) in FIG. At this time, the width measuring circuit 4 in FIG. 1 starts measuring the pulse width (first time) ta of the synchronization detecting means 1 and stores the measurement result in the pulse width ta storage means 10 after the measurement is completed. Thereafter, the on / off control means 3 turns off the laser diode A6 at the timing (c) after the elapse of a predetermined time T1 from the timing of FIG. 3 (b).
[0022]
Next, the on / off control means 3 turns on both the laser diode A6 and the laser diode B7 after a time longer than the predetermined time T1 and shorter than one scanning period T from the timing of FIG. When the laser light emitted from either the laser diode A6 or the laser diode B7 reaches the position of the synchronization detection means 1, the output of the synchronization detection means 1 changes as shown in (e). At this time, the width measuring circuit 4 in FIG. 1 starts measuring the pulse width (second time) tb of the synchronization detecting means 1. Thereafter, the laser diode B7 is turned off at the timing (f) after the time t1 shorter than the previous measurement result ta. When the laser light from the laser diode A6 finishes passing through the synchronization detection means 1, the output PD33 of the synchronization detection means 3 changes as shown in (g), and the measurement result of the pulse width tb is stored in the pulse width tb storage means 11. To do. Thereafter, the on / off control means 3 turns off the laser diode A6 at the timing (h) after the elapse of a predetermined time T1 from the timing shown in FIG.
[0023]
Next, the on / off control means 3 turns on both the laser diode A6 and the laser diode B7 again after a time T2 that is longer than the predetermined time T1 and shorter than one scanning period T from the timing of FIG. Let When the laser light emitted from either the laser diode A6 or the laser diode B7 reaches the position of the synchronization detection means 1, the output of the synchronization detection means 1 changes as shown in (j). At this time, the width measuring circuit 4 in FIG. 1 starts measuring the pulse width (third time) tc of the synchronization detecting means 1. Thereafter, the laser diode A6 is turned off at the timing (k) after the time t1 shorter than the previous measurement result ta. When the laser beam from the laser diode B7 has passed through the synchronization detection means 1, the output PD33 of the synchronization detection means 1 changes as shown in (l), and the measurement result of the pulse width tc is stored in the pulse width tc storage means 12. To do. Thereafter, the on / off control means 3 turns off the laser diode A6 at a timing (m) after the elapse of a predetermined time T1 from the timing of FIG.
[0024]
1 inputs the pulse widths ta, tb, and tc stored in the storage units 10, 11, and 12, respectively, and compares tb and tc. When tb <tc, it is determined that the laser diode A6 scans with the laser beam precedes, and the phase Δt of the laser diode B7 scan with the laser beam is calculated as Δt = tc−ta. On the other hand, when tb> tc, it is determined that scanning with the laser beam of the laser diode B7 precedes, and the phase Δt with respect to the scanning with the laser beam of the laser diode A6 is calculated as Δt = tb−ta.
[0025]
The order of the scanning line by the laser diode A6 and the scanning line by the laser diode B6 and the reason why the phase difference can be calculated by this calculation will be described with reference to FIGS.
[0026]
FIG. 4 is a timing chart when scanning with the laser light of the laser diode A6 precedes, and FIG. 5 is a timing chart when scanning with the laser light of the laser diode B7 precedes. 4 and FIG. 5 are (a) portion in FIG. 3, and (b) are detailed enlarged views of (a) portion in FIG.
[0027]
In the figure, LDA 31 indicates the on / off state of the laser diode A 6, LDB 32 indicates the on / off state of the laser diode B 7, the low level state is off, and the high level state is on. (PDA) 34 is a signal that does not actually exist, but an output signal assumed to be a level induced in the output of the synchronization detection means 1 by the laser diode A6, and (PDB) 35 is a laser diode B6 of the synchronization detection means 1 The output signal is assumed to be a level induced in the output. PD33 indicates an actual output signal of the synchronization detecting means 1, which outputs a high level signal when either (PDA) or (PDB) is at a high level.
[0028]
With reference to FIG. 4, the case where the laser diode A6 scans with laser light precedes the laser diode B6 will be described.
At the timing (d) in the figure, the on / off control means 3 turns on both the laser diode A6 and the laser diode B7. Since the laser diode A6 is ahead, when the laser light emitted from the laser diode A6 reaches the position of the synchronization detection means 1, the output of the synchronization detection means 1 changes as shown in (e). At this time, the width measuring circuit 4 in FIG. 1 starts measuring the pulse width tb of the synchronization detecting means 1.
[0029]
Thereafter, the laser light emitted from the laser diode B7 reaches the position of the synchronization detecting means 1 at (e ′), but the output does not change because the PD33 is already at the high level by the irradiated light of the laser diode A6. . Thereafter, the laser diode B7 is turned off at the timing of (f) after the time t1 shorter than the previous measurement result ta. However, since t1 is shorter than ta, even if the (PDB) 35 becomes low level, the laser diode A6 Since the irradiated light has not passed through the synchronization detecting means 1, the PD 33 maintains a high level.
[0030]
When the laser light from the laser diode A6 finishes passing through the synchronization detection means 1, the output PD of the synchronization detection means 3 changes as shown in (g), and the measurement result is stored in the pulse width tb storage means 11 after the measurement is completed. To do. Thereafter, the on / off control means 3 turns off the laser diode A6 at a timing (h) after the elapse of a predetermined time T1 from the timing of FIG. 3 (e). The measurement result tb at this time is substantially equal to the pulse width ta of the PD 33 output only by the laser diode A6.
[0031]
Next, at the timing (i), the on / off control means 3 turns on both the laser diode A6 and the laser diode B7 again. Since the laser diode A6 is ahead, when the laser light emitted from the laser diode A6 first reaches the position of the synchronization detection means 1, the output of the synchronization detection means changes as shown in (j). At this time, the width measuring circuit 4 in FIG. 1 starts measuring the pulse width tc of the synchronization detecting means 1.
[0032]
Thereafter, the laser light emitted from the laser diode B7 reaches the position of the synchronization detecting means 1 at (j '), but the output is not changed because the PD is already at the high level by the irradiation of the laser diode A6. After that, the laser diode A6 is turned off at the timing (k) after the time t1 shorter than the previous measurement result ta. However, since t1 is shorter than ta, the laser diode B7 is output even when the (PDA) 34 becomes low level. Since the irradiated light has not passed through the synchronization detecting means 1, the PD 33 maintains a high level.
[0033]
Further, since the irradiation light of the laser diode B7 is delayed at the timing (k ′) after the time ta elapses until the laser light of the laser diode A6 passes through the synchronization detecting means 1, the PD signal is (l ) Hold up to a high level. Therefore, the pulse width tc is a time obtained by adding the time Δtc of the phase difference between the scanning line by the laser diode A6 and the scanning line by the laser diode B6 to ta. Therefore, when tb <tc, it can be determined that the laser diode A6 scans with the laser beam precedes, and the phase Δt of the laser diode B7 scan with the laser beam is Δt = Δtc = tc−ta.
[0034]
In FIG. 5, the case where the scanning with the laser beam of the laser diode B7 precedes the scanning with the laser beam of the laser diode A6 will be described.
The on / off control means 3 lights both the laser diode A6 and the laser diode B7 at the timing (d) in the figure. Since the laser diode B7 is ahead, when the laser light emitted from the laser diode B7 reaches the position of the synchronization detection means 1, the output of the synchronization detection means 1 changes as shown in (e). At this time, the width measuring circuit 4 in FIG. 1 starts measuring the pulse width tb of the synchronization detecting means 1.
[0035]
Thereafter, the laser light emitted from the laser diode A6 reaches the position of the synchronization detecting means 1 at (e ′), but the output is not changed because the PD is already at the high level by the irradiated light of the laser diode B7. . Thereafter, the laser diode B7 is turned off at the timing of (f) after the time t1 shorter than the previous measurement result ta. However, since t1 is shorter than ta, even if the (PDB) 35 becomes low level, the laser diode A6 Since the irradiated light has not passed through the synchronization detecting means 1, the PD 33 maintains a high level. Since the irradiation light of the laser diode A6 is delayed even at the timing of (g) after the time ta after the laser light of the laser diode B7 passes through the synchronization detecting means 1, the PD signal is at a high level until (g '). Hold. Accordingly, the pulse width tb is a time obtained by adding the time Δtb of the phase difference between the scanning line by the laser diode A6 and the scanning line by the laser diode B6 to ta.
[0036]
Next, the on / off control means 3 turns on both the laser diode A6 and the laser diode B7 at the timing (i). Since the laser diode B7 is ahead, when the laser light emitted from the laser diode B7 reaches the position of the synchronization detection means 1, the output of the synchronization detection means changes as shown in (j). At this time, the width measuring circuit 4 in FIG. 1 starts measuring the pulse width tc of the synchronization detecting means 1.
[0037]
Thereafter, the laser light emitted from the laser diode A6 reaches the position of the synchronization detecting means 1 at (j '), but since the PD 33 is already at the high level by the irradiation of the laser diode B7, the output does not change. After that, the laser diode A6 is turned off at the timing (k) after the time t1 shorter than the previous measurement result ta. However, since t1 is shorter than ta, the laser diode B7 is output even when the (PDA) 34 becomes low level. Since the irradiated light has not passed through the synchronization detecting means 1, the PD 33 maintains a high level. Further, the laser diode B7 keeps the high level until (k ′) after the time ta has elapsed until the laser beam from the laser diode B7 finishes passing through the synchronization detecting means 1. Accordingly, the pulse width tc is substantially equal to ta.
[0038]
Therefore, when tb> tc, it can be determined that scanning with the laser light of the laser diode B7 precedes, and the phase Δt with respect to scanning with the laser light of the laser diode A6 is Δt = Δtb = tb−ta.
[0039]
With the above calculation, the order of the scanning line by the laser diode A6 and the scanning line by the laser diode B6 and the phase difference thereof can be calculated.
[0040]
Next, after the detection of the shift amount and the beam order is completed, the shift detection unit 13 outputs a plurality of horizontal synchronization signals having a phase difference corresponding to the shift amount and output in the order corresponding to the beam order. The horizontal synchronization generating means to be described will be described with reference to FIG. The horizontal synchronization generation means is composed of a horizontal synchronization signal generation means 14, a delay means A16, and a delay means B17.
[0041]
The horizontal synchronizing signal generating means 14 outputs a horizontal synchronizing signal indicating a period during which the image signal is valid after a predetermined time has elapsed from the output of the synchronization detecting means 1, and is supplied to the delay means A16 and the delay means B17. The delay amounts of the delay means A16 and the delay means B17 can be set from the calculation results of the deviation detection means 13, respectively.
[0042]
When the calculation result of the deviation detection unit 13 indicates that the scanning with the laser beam of the laser diode A6 precedes the scanning with the laser beam of the laser diode B7, the delay amount of the delay unit B17 is set to be greater than the delay amount of the delay unit A16. The phase difference detection result is set to be longer by Δt. On the other hand, when the result of the deviation detecting means 13 is that the scanning with the laser light of the laser diode B7 precedes the scanning with the laser light of the laser diode A6, the delay amount of the delay means A16 is set to the delay amount of the delay means B17. Accordingly, the phase difference detection result is set to be longer by Δt.
[0043]
The image signal A8 is generated in synchronization with the output synchronization signal of the delay means A16, and the image signal B9 is generated in synchronization with the output synchronization signal of the delay means B17. Can be formed.
[0044]
FIG. 6 is a view for explaining another embodiment of the multi-beam light emitting means 2. In this embodiment, three laser diodes A26, B27, and C28 are arranged in a straight line in order on one chip-shaped diode support member 25.
[0045]
These laser diodes A26, B27, and C28 should originally be installed as shown in FIG. 6A, but are installed with an inclination due to an error in the mounting angle as shown in FIG. Sometimes. In FIGS. 2B and 2C, the inclination angle of the diode support member 25 is set to be larger than the actual angle in order to significantly represent the state in which the diode support member 25 is inclined. In such a case, first, the phase difference between the scanning diodes at both ends, that is, the scanning line by the laser diode A26 and the scanning line by the laser diode C28, is calculated. The order of scanning lines and the method for calculating the phase difference are the same as in the above embodiment.
[0046]
The order of the scanning lines by the laser diode B27 at the intermediate position between the laser diode A26 and the laser diode C28 is naturally second, and the phase difference is half of the phase difference between the scanning line by the laser diode A26 and the scanning line by the laser diode C28. Therefore, it can be calculated by multiplying by 1/2.
[0047]
In this embodiment, the case where the three laser diodes A26 to C28 are arranged linearly in order has been described. However, even when the four laser diodes A26 to D29 are arranged linearly, the laser diodes at both ends are first arranged. That is, the phase difference between the scanning line by the laser diode A26 and the scanning line by the laser diode D29 is calculated.
[0048]
As a result, for example, when the scanning line by the laser diode A26 is first and the scanning line by the laser diode D29 is later, the order of the scanning lines is laser diodes A26, B27, C28, and D29. The phase difference between the scanning lines based on the laser diode A26 can be calculated by multiplying the phase difference between the scanning line by the laser diode A26 and the scanning line by the laser diode D29 by 1/3. The laser diode C28 can be calculated by multiplying the phase difference between the scanning line by the laser diode A26 and the scanning line by the laser diode D29 calculated in the above by 2/3.
[0049]
FIG. 7 is a view for explaining still another embodiment of the multi-beam light emitting means 2. In this embodiment, three laser diodes A26, B27, and C28 are individually arranged.
[0050]
One of the three laser diodes A26, B27, and C28 is determined as a reference laser diode (for example, laser diode A26), and the order of the scanning line by the laser diode A26 and the scanning line by the laser diode B27 and its phase difference are calculated. To do. Next, the order of the scanning line by the laser diode A26 and the scanning line by the laser diode C28 and its phase difference are calculated. The order of scanning lines and the method for calculating the phase difference are the same as in the above embodiment. Then, the calculation results are collated to determine the order of the scanning lines of the other laser diodes B27 and C28 with reference to the laser diode A26.
[0051]
Even if the number of laser diodes increases, the order of the scanning lines and the phase difference thereof may be calculated with respect to the reference laser diode by the method described above.
[0052]
【The invention's effect】
As described above, according to the present invention, there is provided an inexpensive multi-beam optical scanning method capable of detecting the timing shift amount of a plurality of beams emitted from a plurality of light sources and the beam order indicating which beam precedes. Can be provided.
[0053]
Further, according to the present invention, an image having no deviation in the main scanning direction can be obtained without using an adjustment mechanism that mechanically adjusts the position of the light source based on the detected deviation amounts of the plurality of light beams and the order of the light beams. An image forming method that can be formed can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a positional relationship between a photoconductor and a synchronization detecting unit of the image forming apparatus.
FIG. 3 is a timing chart showing the on / off states of the laser diode A and the laser diode B and the state of the output signal of the synchronization detecting means according to the embodiment of the present invention.
FIG. 4 is a timing chart showing the on / off states of the laser diode A and the laser diode B and the state of output signals of the synchronization detecting means according to the embodiment of the present invention.
FIG. 5 is a timing chart showing the on / off states of the laser diode A and the laser diode B and the state of the output signal of the synchronization detecting means according to the embodiment of the present invention.
FIG. 6 is a view for explaining a laser diode according to another embodiment of the present invention.
FIG. 7 is a view for explaining a laser diode according to still another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Synchronization detection means 2 Multi-beam light emission means 3 On / off control means 4 Width measurement means 6 Laser diode A
7 Laser diode B
8 Image signal A
9 Image signal B
10 Pulse width ta storage means 11 Pulse width tb storage means 12 Pulse width tc storage means 13 Deviation detection means 14 Horizontal synchronization generation means 16 Delay means A
17 Delay means B
20 Photoconductor 21 Optical deflector 22 Optical deflection motor 23 Collimator lens 24 Main scanning direction 25 Diode support member 26 Diode A
27 Diode B
28 Diode C
31 ON / OFF state of laser diode A (LDA)
32 Laser diode B on / off status (LDB)
33 Output signal (PD) of synchronization detection means
34 Output signal (PDA) assumed to be a level induced in the output of the synchronous detection means by laser diode A
35 Output signal (PDB) assumed to be a level induced in the output of the synchronous detection means 1 by the laser diode B

Claims (2)

A multi-beam light emitting means having at least a first light source and a second light source for simultaneously scanning a plurality of light beams in a main scanning direction on the photosensitive member;
A light deflecting means for scanning a plurality of light beams emitted from the multi-beam light emitting means in the main scanning direction;
Has one light-receiving element, wherein the multi-beam multi-beam optical scanning of the multi-beam optical scanning device in which the light beams emitted from the light emitting means and a synchronization detecting means for detecting the scanning position timing by receiving a predetermined position In the method
Turn on the first light source, measure a first time interval ta passing through the synchronization detection means,
Next, the first light source and the second light source are turned on simultaneously, the first light beam is received, the output of the synchronization detecting means changes, and the first light source and the second light source are changed after a predetermined time t1 shorter than the first time width ta. The second light source is turned off, and then the second time tb until the light beam of the first light source finishes passing through the synchronization detection means is measured,
Further, the first light source and the second light source are turned on at the same time, the first light beam is received, and the output of the synchronization detecting means is changed. Then, after a predetermined time t1 shorter than the first time width ta, the first light source is changed. A third time tc until the light beam of the second light source finishes passing through the synchronization detection means,
The difference between the first time width ta, the second time width tb, and the third time width tc is calculated,
When tb <tc, it is determined that the scanning with the light beam of the first light source precedes the scanning with the light beam of the second light source, and the timing deviation amount Δt of the scanning with the light beam is set to Δt = tc−ta Calculated by
When tb> tc, it is determined that the scanning by the light beam of the second light source precedes the scanning by the light beam of the first light source, and the timing deviation amount Δt of the scanning by the light beam is set to Δt = tb−ta a multi-beam optical scanning method which is characterized in that in calculation. A horizontal synchronization signal is output according to the timing deviation amount calculated by the multi-beam optical scanning method according to claim 1 and the order of the light beams, and an image signal is generated in synchronization with the horizontal synchronization signal. Image forming method .

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