JPH11188915A - Method for image forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent jitter generated by being influenced by face falling of a rotary polygon mirror. SOLUTION: An initial error time Δtn (n: an integer number selected from 1 to 6) by each reflection face as an error of a time period from a start timing of scanning to a timing of a light beam passing through a starting edge of a recording region and an accumulated error time Δtmsn by each reflection face as an error of an accumulated time period from the start timing of the scanning of the light beam deflected by a reference reflection face to the start timing of the scanning of the light beam deflected by each of the reflection face are obtained beforehand. A generating timing of an image recording signal by each reflection face is corrected based on the initial error time Δtn by each reflection face and accumulated error time Δtmsn by each reflection face when executing the image forming processing, thereby eliminating influence by face falling of each reflection face to a printing start timing Ta for the scanning of the light beam deflected by each reflection face. The light beam is modulated to be outputted in accordance with the image recording signal generated based on the corrected printing start timing Ta, thereby executing the image forming processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method, and more specifically, to deflect a light beam modulated and output based on an image recording signal generated at a predetermined timing by a reflecting surface of a rotary polygon mirror. The image carrier is scanned with the deflected light beam, an image formed on the image carrier by the scanning is developed, and the image visualized by the development is transferred to a recording medium, whereby the image is recorded on the recording medium. And an image forming method for forming the image.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as a laser beam printer or a copying machine, a laser beam is flashed by a laser exposure device in accordance with an output image signal, and the laser beam is flashed uniformly. An electrostatic latent image corresponding to the output image signal is formed on the photoconductor by scanning and exposing the photoconductor subjected to the above process, and a toner image obtained by developing the electrostatic latent image is formed on a recording medium. 2. Description of the Related Art There is known an image forming apparatus which forms an image on a recording medium by a so-called electrophotographic method of transferring and fixing.

As a light source of the laser exposure apparatus, a semiconductor laser (laser diode) is generally used, and a laser beam modulated in accordance with an output image signal is output from the light source. In the image forming apparatus, in order to obtain the output timing of the laser beam (that is, the timing of writing an image), a lens for correcting the beam position and the beam diameter (hereinafter referred to as an “SOS lens”) is provided on the image writing side on the deflection scanning optical path. ), And a beam position detector for detecting a beam that has passed through the SOS lens is provided. By detecting a laser beam that has passed over the beam position detector, horizontal synchronization is achieved, The writing timing of the image is determined. That is, the laser beam is modulated after a predetermined time from the detection of the passage of the laser beam by the beam position detector, and the photoconductor is scanned and exposed with the modulated laser beam.

In such an image forming apparatus, if one of the reflecting surfaces of the rotary polygon mirror is slightly inclined back and forth in the scanning direction, the pitch of the scanning line of the deflected laser beam changes. I will. At this time, FIG.
As shown in the figure, the light receiving unit 90 (or S) of the beam position detector
If the laser beam is incident on the OS lens at a slight angle, the path of the laser beam changes,
The output timing of the SOS signal, that is, the horizontal synchronization pulse, may be shifted by Δt _n . As a result, as shown in FIG. 11, there is a problem in that the image recording start position determined by the output timing of the horizontal synchronization pulse is shifted, and the start end of the image may fluctuate in the vertical direction. This problem occurs regardless of the shape of the light receiving portion of the beam position detector, and this phenomenon is generally called jitter.

To solve such a problem, Japanese Patent Application Laid-Open No. 63-11 / 1988
Japanese Patent No. 0413 discloses a technique in which jitter is measured by two beam position detectors and the phase is shifted in a direction to reduce the dot shift by about half the error time.
However, in this technique, it is not possible to correct so as to completely eliminate the jitter, and since two beam position detectors are used, there arises a problem that the apparatus becomes large and expensive.

[0006] Japanese Patent Application Laid-Open No. 5-68142 discloses that
There is disclosed a technique for deflecting a laser beam by using two reflecting surfaces having less jitter among the reflecting surfaces of a rotating polygon mirror. However, in this technique, since only two reflecting surfaces are used, it is difficult to increase the scanning speed, and it is not suitable for high-resolution image forming processing.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is possible to avoid the increase in the size of the apparatus and to prevent the scanning speed from being increased. It is an object of the present invention to provide an image forming method capable of preventing jitter caused by the influence of mirror surface tilt.

[0008]

According to a first aspect of the present invention, there is provided an image forming method comprising the steps of: (a) outputting a light beam modulated and output based on an image recording signal generated at a predetermined timing; It is deflected by the reflecting surface, scans the image carrier with the deflected light beam, develops the image formed on the image carrier by the scanning, and transfers the image visualized by the development to a recording medium. Accordingly, in the image forming method for forming an image on the recording medium, the start timing of scanning by the light beam deflected by the reflection surface, and the position corresponding to the end of the recording medium, the light beam first The time interval with the passing timing is obtained for each reflection surface, and the time interval for each reflection surface is averaged to obtain a reference time interval.From the difference between the time interval and the reference time interval,
An initial error time of the scanning start timing is obtained for each reflection surface, and the image recording signal is generated at a timing corrected by the initial error time for each reflection surface during image forming processing. .

According to a second aspect of the present invention, there is provided an image forming method, wherein a light beam modulated and output based on an image recording signal generated at a predetermined timing is deflected by a reflecting surface of a rotary polygon mirror. By scanning the image carrier, developing the image formed on the image carrier by the scanning, by transferring the image visualized by the development to a recording medium,
An image forming method for forming an image on the recording medium,
A time interval between the start of scanning by the light beam deflected by the reflection surface, a timing at which the light beam first passes through a position corresponding to the end of the recording medium, and a time interval for each reflection surface; From the difference from the reference time interval obtained by averaging the above time intervals, an initial error time of the scanning start timing is obtained for each reflection surface, and the scanning by the light beam deflected by the predetermined reference reflection surface is performed. From the start timing to the start timing of scanning by the light beam deflected by each reflecting surface, and averaging for each reflecting surface to obtain a reference cumulative time for each reflecting surface. During the non-image forming process after the above, the total time from the start timing of scanning by the light beam deflected by the reference reflection surface to the start timing of scanning by the light beam deflected by each reflection surface is calculated. Averaging is performed for each reflecting surface to determine the total time for each reflecting surface, and from the difference between the calculated total time and the reference cumulative time, the total error time of the scan start timing is determined for each reflecting surface. During the processing, the image recording signal is generated at a timing corrected by the initial error time for each reflecting surface and the total error time for each reflecting surface.

Further, in the image forming method according to the third aspect,
In the image forming method according to claim 1 or 2,
The time interval between the scanning start timing and the timing at which the light beam first passes through the position corresponding to the edge of the recording medium is an average value of a plurality of time intervals obtained a plurality of times. .

In the image forming method according to the first aspect of the present invention, a light beam modulated and output based on an image recording signal generated at a predetermined timing is deflected by a reflecting surface of a rotary polygon mirror, and the deflected light beam is used. The image carrier is scanned, the image formed on the image carrier by the scanning is developed, and the image visualized by the development is recorded on a recording medium (for example, recording paper).
This is an image forming method for forming an image on a recording medium by transferring the image to a recording medium.

Before execution of the image forming process (for example, before shipment of the image forming apparatus or during initial setting immediately after installation of the image forming apparatus)
A time interval (hereinafter, referred to as a time interval t _n) between a start timing of scanning by the light beam deflected by the reflection surface of the rotary polygon mirror and a timing at which the light beam first passes through a position corresponding to the end of the recording medium. ) Is obtained for each reflecting surface, and a time interval t _n for each reflecting surface is averaged to obtain a reference time interval (hereinafter referred to as a reference time interval T _ave ).

The timing at which the light beam first passes through a position corresponding to the edge of the recording medium is determined, for example, by a production apparatus of an image forming apparatus capable of executing an image forming process based on the image forming method according to the present invention. It can be detected by a provided beam position detector or the like.

The time interval t _n and the reference time interval T
An error time of the scan start timing (hereinafter, referred to as an initial error time Δt _n ) is obtained for each reflection surface from the difference from _ave . The initial error time Δt _n for each reflecting surface is a value corresponding to the degree of surface inclination of each reflecting surface in the initial stage (mainly at the time of assembling the image forming apparatus or the like).

Therefore, in the image forming process, an image recording signal is generated at a timing corrected by the initial error time Δt _{n for} each reflecting surface, and the light beam modulated and output based on the image recording signal is used to generate the image recording signal. The image forming process is performed as described above.

As described above, according to the image forming method of the present invention, the initial error time Δt _n for each reflecting surface corresponding to the degree of initial surface tilt is obtained before the image forming process is executed, and Initial error time Δt _n for each reflecting surface during the forming process
An image recording signal is generated at the timing corrected by the above, and the image forming process is performed by the light beam modulated and output based on the image recording signal. Therefore, the image recording is performed according to the inclination of each reflecting surface of the rotary polygon mirror. The signal generation timing can be appropriately corrected, and a good image without jitter can be formed. Moreover, the jitter can be prevented without adding a new component to the image forming apparatus and without hindering the increase in the scanning speed.

Next, in the image forming method according to the present invention,
Similar to the above, the time interval t _n of the respective reflecting surfaces every timing the start timing and the light beam of the scanning by the light beam passes through the position corresponding to the end of the recording medium first, the time of each reflective surface each From the difference from the reference time interval T _ave obtained by averaging the interval t _n , the initial error time Δt _n of the scan start timing is obtained for each reflection surface.

The total time from the start of scanning by the light beam deflected by the predetermined reference reflecting surface to the start of scanning by the light beam deflected by each reflecting surface is averaged for each reflecting surface. A reference accumulated time (hereinafter, referred to as a reference accumulated time T _msn ) for each reflection surface is obtained.

Either the initial error time Δt _n for each reflecting surface or the reference cumulative time T _msn for each reflecting surface may be determined first.

Then, after the rotating polygon mirror is rotated stably,
During image forming processing (for example, warm-up, warm-up,
From the time the image is
During normal processing, such as during the gap between pages)
Start timing of scanning by light beam deflected by plane
Start timing of scanning by the light beam deflected by each reflecting surface.
Average the total time until the image is taken for each reflective surface and reflect each
Cumulative time for each face (hereinafter, cumulative time t_msn)
Total time t_msnAnd reference cumulative time T_{ms n}Difference with
Thus, the cumulative error time (hereinafter, referred to as the cumulative
Total error time Δt _msnIs called for each reflection surface.
Good.

While the initial error time Δt _n for each reflecting surface is a value corresponding to the initial degree of surface tilt of each reflecting surface,
The cumulative error time Δt _msn for each reflecting surface is deteriorated with time,
This is a value corresponding to the degree of surface tilt of each reflecting surface caused by factors such as vibration / shock, temperature environment, and the like.

Therefore, during the image forming process, the initial error time Δt _{n for} each reflection surface and the total error time Δt for each reflection surface
An image recording signal is generated at the timing corrected by t _msn , and an image forming process is performed as described above using a light beam modulated and output based on the image recording signal.

As described above, according to the image forming method of the present invention, the initial error time Δt _{n for} each reflecting surface corresponding to the degree of the initial surface tilt, and deterioration with time, vibration / shock, temperature environment, etc. The cumulative error time Δt _msn for each reflecting surface corresponding to the degree of surface tilt of each reflecting surface caused by the factor is obtained in advance, and the initial error time Δt _n for each reflecting surface during image forming processing.
And an image recording signal is generated at a timing corrected by the cumulative error time Δt _{msn for} each reflecting surface, and an image forming process is performed by a light beam modulated and output based on the image recording signal. The generation timing of the image recording signal can be more accurately corrected according to the inclination of each reflection surface, and a good image without jitter can be formed. Moreover, the jitter can be prevented without adding a new component to the image forming apparatus and without hindering the increase in the scanning speed.

If the average value of a plurality of time intervals obtained a plurality of times is adopted as the time interval t _n for each reflecting surface, the scanning start timing and the light beam is able to reduce the influence of the detection error of the timing or the like passing through the position corresponding to the end of the recording medium to the first, can be determined more accurately the time interval t _n of the respective reflecting surfaces each. For this reason, the accuracy of the initial error time Δt _n for each reflecting surface is improved, and the generation timing of the image recording signal can be corrected more accurately.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below.

[First Embodiment] First, a first embodiment corresponding to the first and third aspects of the present invention will be described.

[Schematic Configuration of Image Forming Apparatus] FIG. 1 shows a configuration diagram of a main part of an image forming apparatus 30 in the present embodiment. As shown in FIG. 1, the image forming apparatus 30 is provided with a photosensitive drum 1 as an image carrier, and the photosensitive drum 1 rotates at a predetermined angular velocity in a direction indicated by an arrow Q in FIG. In the vicinity of the outer peripheral portion of the photosensitive drum 1, a charging device 21, a developing device 23, a transfer device 24, and a cleaning device 26 are sequentially installed along the outer periphery. Also,
Above the photosensitive drum 1, an optical scanning device 22 that scans the surface of the photosensitive drum 1 with laser light modulated according to image data of an image to be formed is provided. The scanning position of the laser beam by the optical scanning device 22 is determined by the charging device 2.
1 and the developing position by the developing device 23.

The surface of the photosensitive drum 1 charged by the charging device 21 is scanned and exposed by a laser beam from an optical scanning device 22 modulated according to image data of an image to be formed, thereby forming an electrostatic latent image. Is done. Further, the electrostatic latent image is developed by the developing device 23, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 1.

On the other hand, the paper P is transferred to the photosensitive drum 1 and the transfer device 2 along a predetermined path in synchronization with the formation of the toner image.
4 is conveyed to the nip portion. A predetermined transfer bias voltage is applied to the transfer device 24 at the timing when the sheet P is conveyed to the nip portion, and the photosensitive member is caused by the application of the transfer bias voltage and the pressing action of the sheet P against the photosensitive drum 1 by the transfer device 24. The toner image on the drum 1 is transferred to the paper P.

The sheet P after the transfer is conveyed to the fixing device 25, and the toner image formed on the sheet P is fixed on the sheet P. The fixed sheet P is conveyed in the direction of arrow W and discharged to a discharge tray (not shown).

Next, the configuration of the optical scanning device 22 will be described with reference to FIG. As shown in FIG. 2, a laser diode (hereinafter, referred to as an LD) 3 is provided in the optical scanning device 22, and the laser light emitted from the LD 3 passes through an optical system such as a collimator lens (not shown). Thereafter, the light enters a rotating polygon mirror (polygon mirror) 8. Rotating polygon mirror 8
Is mounted on a motor drive board 9 including a motor for rotating the polygon mirror 8 and rotates at a constant angular speed in a predetermined direction.

A plurality of (here, six as an example) reflecting surfaces are formed on the side surface of the rotating polygon mirror 8, and the laser light incident on the rotating polygon mirror 8 is deflected by the reflecting surface and then f
The light passes through the θ lens 2 and irradiates the surface of the photosensitive drum 1. At this time, the surface of the photosensitive drum 1 is scanned and exposed with the laser light by the deflection of the laser light by the rotary polygon mirror 8. FIG. 2 shows a print start position 10 and a print end position 11 on the surface of the photosensitive drum 1, and an area between the print start position 10 and the print end position 11 corresponds to an image forming area. I do.

The optical scanning device 22 includes a mirror 4 at a predetermined position before the printing start position 10 of the photosensitive drum 1 when the photosensitive drum 1 is scanned by the laser beam.
Are disposed on the optical axis of the laser light reflected by the mirror 4. The SOS lens 5 for correcting the beam position and the beam diameter, and the SOS lens 5 for detecting the laser light passing through the SOS lens 5. A start detector (SOS sensor) 6 is provided.

The SOS sensor 6 is connected to a control device 40 composed of a microcomputer or the like.
The detection signal from the S sensor 6 is input to the control device 40,
Upon receiving this detection signal, the control device 40 establishes horizontal synchronization and determines the image writing timing. Further, the control unit 40 is connected to a storage unit 42 constituted by a nonvolatile memory such as an EP-ROM.

One of the six reflecting surfaces of the rotary polygon mirror 8 is a reflecting surface (hereinafter referred to as a reference surface or a first surface) serving as a reference for starting an error time calculation or the like described later. A position detector (not shown) on the motor drive board 9 detects that the reference plane has passed a predetermined position immediately before the laser beam incident position during rotation of the rotary polygon mirror 8 and determines a reference position. Surface detection signal (shown in FIGS. 3, 6, and 7)
rev signal) to the control device 40.

[Operation of First Embodiment] Next, as an operation of the first embodiment, an operation based on the image forming method according to the present invention will be described.

At the time of final adjustment of the image forming apparatus 30 before shipment, the control apparatus 40 executes the control routine of the initial error time calculation processing of FIG. At the time of execution of the initial error time calculation process, as shown in FIG. 12, the beam position detector 38 installed in the production apparatus that produces the image forming apparatus 30 is positioned near the print start position 10, It is assumed that the beam position detector 38 detects that the laser beam has passed the print start position 10.

In step 102 of FIG. 4, the rotary polygon mirror 8 is started to be driven by the rotary drive motor.
At 4, wait for the rotating polygon mirror 8 to rotate stably. Then, after the rotating polygon mirror 8 has been rotated stably, when the position detector detects that the reference surface (first surface) of the rotating polygon mirror 8 has passed a predetermined position immediately before the laser beam incident position (step 10).
6 (if the / rev signal is output from the position detector as shown in FIG. 3), the SOS sensor 6 detects the SOS timing regarding the laser beam deflected on the first surface ( Step 108), the beam position detector 38 detects the paper end passage timing at which the laser beam has passed the print start position (paper end) 10 (Step 1).
10). Then, in the next step 112, the time interval between the SOS timing and the paper edge passing timing is calculated.

Thereafter, the detection of the SOS timing (step 108) and the detection of the paper end passage timing (step 1)
10) and the calculation of the time interval between the SOS timing and the paper edge passing timing (step 112) is performed on the laser light deflected on all the reflecting surfaces after the second surface. Further, steps 108 to 112 are repeatedly executed for N rotations of the rotating polygon mirror 8 (that is, N times for each reflection surface).

In the next step 116, a time interval t _n for each reflecting surface is obtained by averaging the time intervals calculated N times for each reflecting surface for each reflecting surface.
At 18, a reference time interval T _ave is obtained by averaging the time intervals t _n for each reflection surface. Note that n is an integer of 1 to 6 corresponding to each reflection surface (the same applies to the following).

Then, in the next step 120, the difference between the time interval t _{n for} each reflection surface and the reference time interval T _ave is calculated.
The initial error time Δt _n of the SOS timing is obtained for each reflection surface and stored in the storage unit 42. The initial error time Δt _n for each reflecting surface is a value corresponding to the degree of surface inclination of each reflecting surface in an initial stage (mainly at the time of assembling the image forming apparatus 30 or the like).

By the above-described initial error time calculation processing, the initial error time Δ for each reflecting surface corresponding to the initial degree of surface tilt
t _n is obtained before the image forming apparatus 30 is shipped, and is stored in the storage unit 42.

Next, when the image forming apparatus 30 executes the image forming process after shipment, the control unit 40 executes the control routine of FIG.

In step 202 of FIG. 5, the rotary polygon mirror 8 is started to be driven by the rotary drive motor, and the initial error time Δt _n for each reflecting surface stored in the storage unit 42 in the initial error time calculation process is read. . Next step 204
Then, the image recording signal timing (= timing for outputting the image recording signal) for each reflection surface is corrected by the read initial error time Δt _n .

After the rotating polygon mirror 8 is rotated stably,
When the reference surface is detected, the process proceeds to step 210, where the image recording signal is generated based on the corrected image recording signal timing for each reflection surface during scanning exposure using the laser light deflected on each reflection surface. Perform formation processing. As a result, as shown in FIG. 3, the influence of surface inclination of each reflecting surface on the printing start timing Ta of scanning by the light beam deflected on each reflecting surface is eliminated, and the printing start timings Ta are aligned (synchronized). Become.

According to the above-described first embodiment, the initial error time Δt _n for each reflecting surface corresponding to the degree of initial surface inclination (mainly when the image forming apparatus 30 is assembled) is obtained in advance. And the initial error time Δt for each reflecting surface during the image forming process.
_{Since an} image recording signal is generated at the timing corrected by _n , and an image forming process is performed by a light beam modulated and output based on the image recording signal, an image is formed according to the inclination of each reflecting surface of the rotary polygon mirror. The generation timing of the recording signal can be appropriately corrected, and a good image without jitter can be formed. Moreover, the jitter can be prevented without adding a new component to the image forming apparatus and without hindering the increase in the scanning speed.

[Second Embodiment] Next, a second embodiment corresponding to the invention described in claims 2 and 3 will be described.
Note that the configuration of the image forming apparatus 30 according to the second embodiment is the same as the configuration of the first embodiment, and a description thereof will be omitted.

Thus, as an operation of the second embodiment, an operation based on the image forming method according to the present invention will be described. At the time of final adjustment of the image forming apparatus 30 before shipment, the control unit 40 executes a control routine of a process of calculating the initial error time and the reference accumulated time in FIG.

When executing the calculation processing of the initial error time and the reference total time, the beam position detector 38 installed in the production apparatus for producing the image forming apparatus 30 starts printing, as shown in FIG. Positioned near position 10,
It is assumed that the beam position detector 38 detects that the laser beam has passed the print start position 10.

In step 102 of FIG. 8, the rotary polygon mirror 8 is started to be driven by the rotary drive motor.
At 4, wait for the rotating polygon mirror 8 to rotate stably. Then, after the rotating polygon mirror 8 has been rotated stably, when the position detector detects that the reference surface (first surface) of the rotating polygon mirror 8 has passed a predetermined position immediately before the laser beam incident position (step 10).
If the determination is affirmative in step S6), the SOS sensor 6 detects the SOS timing related to the laser beam deflected on the first surface (step 108), and starts a timer for measuring the total time described later (step 109). . Then, the beam position detector 38 detects the timing at which the laser beam has passed the print start position (paper edge) 10 by the beam position detector 38, and
A time interval between the SOS timing and the paper edge passing timing is calculated (step 111).

In the next step 122, the SOS timing for the laser beam deflected on the next surface (second surface) is set to SOS.
If detected by the sensor 6, the routine proceeds to step 124, where the time of the timer is measured. Thus, the total time _Tms1 from the SOS timing for the laser light deflected on the first surface shown in FIG. 7 to the SOS timing for the laser light deflected on the first surface is obtained. In the next step 126, the beam position detector 38 detects the paper end passage timing at which the laser beam has passed the print start position (paper end) 10, and the time between the detected paper end passage timing and the SOS timing detected in step 122. Calculate the interval.

Thereafter, the detection of the SOS timing (step 122), the timing (step 124), the detection of the paper edge passage timing, and the calculation of the time interval between the SOS timing and the paper edge passage timing (step 126) are performed on the second and subsequent surfaces. Is performed on the laser light deflected by all the reflection surfaces. As a result, the total time T _ms2 shown in FIG.
_{T ms 3, T ms4, T} ms5, T ms6 is obtained.

Further, N rotations of the rotating polygon mirror 8 (that is, N rotations)
Steps 122 to 126 are repeatedly executed (N times for each reflection surface).

After calculating the time interval between the SOS timing and the sheet edge passing timing N times for each reflection surface, the process proceeds to step 130, where the SOS timing for the laser light deflected on the reference surface (first surface) is set to SOS. Detected by the sensor 6, the time of the timer is measured in the next step 132, and the timer is stopped. As a result, the N-th cumulative time T _ms6 shown in FIG. 7 is obtained.

In the next step 134, the time interval t _n for each reflecting surface is obtained by averaging the time intervals calculated N times for each reflecting surface for each reflecting surface.
At 36, the reference time interval T _ave is obtained by averaging the time intervals t _n for each reflection surface. And the next step 1
At 38, the initial error time Δt _n of the SOS timing is determined for each reflection surface from the difference between the average time interval t _{n for} each reflection surface and the reference time interval T _ave .

In the next step 140, the reference cumulative time T _msn for each reflecting surface is obtained by averaging the cumulative time for each reflecting surface obtained by the time _measurement . In the next step 142, the SOS for each reflecting surface is obtained. stores the initial error time Delta] t _n and the reference cumulative time T _{ms n} of the reflecting surfaces every time the storage unit 42, and ends the process.

[0057] The initial error time and the reference cumulative time of calculation processing described above, the initial error time Delta] t _n and the reference cumulative time T _{ms n} of the reflecting surfaces each of the reflecting surfaces each corresponding to the degree of tilt initial is, It is obtained before the image forming apparatus 30 is shipped, and is stored in the storage unit 42.

Next, when the image forming apparatus 30 executes image forming processing after shipment, the control unit 40 executes the control routine of FIG.

In step 203 in FIG. 9, the rotary polygon mirror 8 is started to be driven by the rotary drive motor, and the storage unit 4 is started.
The initial error time Δt _{n for} each reflecting surface and the reference total time T _msn for each reflecting surface stored in 2 are read.

After the rotating polygon mirror 8 is rotated stably,
When the reference surface (first surface) is detected, the process proceeds to step 212, where the SOS sensor 6 detects the SOS timing regarding the laser beam deflected by the first surface (step 21).
2) Start a timer (step 214). When the SOS sensor 6 detects the SOS timing related to the laser beam deflected on the next surface (second surface) in the next step 216, the process proceeds to step 218, and the time of the timer is measured.

Thereafter, the detection of the SOS timing (step 216) and the timing (step 218) are repeatedly executed N times for all the reflecting surfaces.

When the total time from the SOS timing of the first surface has been measured N times for each reflection surface, the timer is stopped (step 222), and in the next step 224, the measurement is performed N times for each reflection surface. By averaging the total time for each reflection surface, the total time t _msn for each reflection surface is obtained. Then, in the next step 226, the SOS is calculated from the difference between the total time t _{msn for} each reflection surface and the reference total time T _msn.
The total error time Δt _msn of the timing is obtained for each reflection surface. Note that the total error time Δt of this SOS timing is
_msn is a value corresponding to the degree of surface tilt of each reflecting surface caused by factors such as deterioration over time, vibration / shock, and temperature environment.

In the next step 228, the initial error time Δ
correcting the image recording signal timing of each reflective surface each at t _n and the obtained cumulative error time Delta] t _msn. Then, in the next step 230, an image recording signal is generated based on the corrected image recording signal timing for each reflective surface during scanning exposure with the laser light deflected on each reflective surface to perform image forming processing. As a result, as shown in FIG. 6, the influence of the tilt of each reflecting surface on the printing start timing Ta of scanning by the light beam deflected by each reflecting surface is eliminated, and the printing start timings Ta are aligned (synchronized). Become.

According to the above-described second embodiment, the initial error time Δt _{n for} each reflecting surface and the degree of surface tilt of each reflecting surface caused by factors such as deterioration with time, vibration / shock, and temperature environment. An image recording signal is generated at a timing corrected by the cumulative error time Δt _{msn for} each reflecting surface corresponding to the above, and an image forming process is performed by a light beam modulated and output based on the image recording signal. The generation timing of the image recording signal can be more accurately corrected according to the inclination of each reflection surface of the mirror 8, and a good image without jitter can be formed.

In the first and second embodiments, the SO
The time interval between the S timing and the paper edge passing timing was calculated N times for each reflecting surface, and the N time intervals were averaged for each reflecting surface to obtain the time interval t _n for each reflecting surface. The number of times of calculation of the time interval (that is, the value of N) can be set arbitrarily, and N = 1 may be used. However, in order to obtain a good time interval t _n accuracy, it is desirable to determine the time interval t _n by averaging the time interval calculated as possible a number of times.

[0066]

As described above, according to the image forming method of the present invention, the initial error time Δt _n for each reflecting surface corresponding to the initial degree of surface tilt is determined before executing the image forming process. In advance, an image recording signal is generated at a timing corrected by the initial error time Δt _n for each reflection surface during the image forming process, and the image forming process is performed by a light beam modulated and output based on the image recording signal. Accordingly, the generation timing of the image recording signal can be appropriately corrected according to the inclination of each reflecting surface of the rotary polygon mirror, and a good image without jitter can be formed.

Further, according to the image forming method of the present invention, the initial error time Δt _{n for} each reflecting surface, and the trouble of each reflecting surface caused by factors such as deterioration over time, vibration / shock, and temperature environment. Total error time Δt for each reflecting surface corresponding to the degree of
_The image recording signal is generated at the timing corrected by the _msn , and the image forming process is performed by the light beam modulated and output based on the image recording signal, so that the image is formed according to the inclination of each reflecting surface of the rotary polygon mirror. The generation timing of the recording signal can be corrected with higher accuracy, and a good image without jitter can be formed.

Further, according to the image forming method of the present invention, the time interval t _n for each reflecting surface can be obtained more accurately, so that the accuracy of the initial error time Δt _n for each reflecting surface is improved. However, the generation timing of the image recording signal can be more accurately corrected.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus.

FIG. 2 is a schematic configuration diagram of an optical scanning device.

FIG. 3 is a diagram for explaining correction of an image recording signal generation timing in the first embodiment.

FIG. 4 is a flowchart illustrating a processing routine of an initial error time calculation process according to the first embodiment.

FIG. 5 is a flowchart showing a processing routine when image formation is executed in the first embodiment.

FIG. 6 is a diagram for explaining correction of an image recording signal generation timing in the second embodiment.

FIG. 7 is a diagram for explaining a reference cumulative time T _msn for each reflection surface.

FIG. 8 is a flowchart illustrating a processing routine of a process of calculating an initial error time and a reference cumulative time according to the second embodiment.

FIG. 9 is a flowchart illustrating a processing routine when image formation is executed in the second embodiment.

FIG. 10 is a diagram for explaining a shift in output timing of a horizontal synchronization pulse.

FIG. 11 is a diagram for explaining jitter.

FIG. 12 is a schematic configuration diagram of an optical scanning device when a beam position detector detects that a laser beam has passed a printing start position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 3 Laser diode 6 SOS sensor 8 Rotating polygon mirror 22 Optical scanning device 30 Image forming device 38 Beam position detector 40 Control device P Recording paper (recording medium)

Claims (3)

[Claims] 1. A light beam modulated and output based on an image recording signal generated at a predetermined timing is deflected by a reflecting surface of a rotary polygon mirror, and the deflected light beam scans an image carrier. An image forming method for developing an image formed on the image carrier by transferring an image visualized by the development onto a recording medium, thereby forming an image on the recording medium, The time interval between the start of scanning by the deflected light beam and the timing at which the light beam first passes through a position corresponding to the edge of the recording medium is determined for each reflection surface, and the time interval for each reflection surface is determined. A reference time interval is obtained by averaging the time intervals, and an initial error time of the scanning start timing is obtained for each reflection surface from a difference between the time interval and the reference time interval. every Generating the image recording signal at a timing corrected by the initial error time of the image forming method. 2. A light beam modulated and output based on an image recording signal generated at a predetermined timing is deflected by a reflecting surface of a rotary polygon mirror, and the deflected light beam scans an image carrier. An image forming method for developing an image formed on the image carrier by transferring an image visualized by the development onto a recording medium, thereby forming an image on the recording medium, The time interval for each reflection surface between the start timing of scanning by the deflected light beam and the timing at which the light beam first passes through the position corresponding to the end of the recording medium, and the time interval for each reflection surface From the difference from the reference time interval obtained by averaging, the initial error time of the scan start timing is obtained for each reflection surface, and the scan start timing by the light beam deflected by the predetermined reference reflection surface Thus, the cumulative time until the start of scanning by the light beam deflected by each reflecting surface is averaged for each reflecting surface to obtain a reference cumulative time for each reflecting surface, after the rotating polygon mirror has been rotated stably. During the non-image forming process, the total time from the start of scanning by the light beam deflected by the reference reflecting surface to the start of scanning by the light beam deflected by each reflecting surface is averaged for each reflecting surface. The cumulative time for each reflecting surface is obtained, and the cumulative error time of the scan start timing is obtained for each reflecting surface from the difference between the obtained cumulative time and the reference cumulative time. At the timing corrected by the initial error time of and the total error time of each reflecting surface,
An image forming method for generating the image recording signal. 3. A time interval between a scan start timing and a timing at which a light beam first passes through a position corresponding to an end of the recording medium is an average value of a plurality of time intervals obtained plural times. The image forming method according to claim 1, wherein: