JP2007245592A - Apparatus, method and program for forming image, and computer readable recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically restore a synchronization signal when a synchronization error is generated. <P>SOLUTION: In a normal operation, when an LD of light irradiation device 2 is made to emit light every time a counter of a main scanning counter 10 indicates, for example, a value of "10000", a synchronization sensor 7 arranged in a normal synchronization detection position, detects this light emission, and a synchronization signal generator 8 generates a synchronization signal. In this state, when a synchronization error detector 9 detects the abnormality of the synchronization signal from the synchronization signal generator 8, automatic restoration is executed. Concretely, one line is scanned by forcing the LD to emit light by an LD controller 1, and if the synchronization sensor 7 detects the forced light emission in the intervening period, the synchronization signal generator 8 provides the synchronization signal. A counter value at this time, for example, "8000" is acquired. After that time, the LD is made to emit light every time the counter indicates a value of "8000", and the synchronization signal is thereby normally provided to complete the automatic restoration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  Optical writing apparatus for writing image by light beam, and image forming apparatus, method, and the like, such as laser printer, digital copying machine, facsimile apparatus having the optical writing apparatus, or a digital multi-function peripheral having these functions combined The present invention relates to a program used in the method and a computer-readable recording medium on which the program is recorded.

In an image forming apparatus that forms an image on a photosensitive member using a developing device such as a polygon motor using laser light emitted from a laser light source such as an LD, 1 is used to specify the writing position in the main scanning direction. Line-by-line synchronization is essential. The following methods are mainly used as a method of synchronizing. First, a device that generates a synchronization signal by receiving laser light is installed so as to receive light in a non-image area. Next, using a counter based on the frequency used for LD driving, when the count value comes to a timing at which the sync signal generator can receive light, a laser beam is output to generate a sync signal, and this sync signal The image is developed in the main scanning direction on the basis of the above. If the image forming apparatus is operating normally, a synchronization signal is generated for each line scan, and the intended writing is started. However, if the synchronization signal is not generated, the intended writing cannot be performed in the next scanning. Therefore, it becomes an abnormal image. For this reason, when the synchronization signal is not generated, it is determined that the image forming apparatus is abnormal, and the image forming apparatus is stopped. There are various causes for the abnormality of the synchronization signal. For example, if the sync detection sensor has an attachment that prevents light reception, or if the reflection surface of the polygon motor has an attachment that prevents light reflection, the synchronization detection sensor cannot recognize the light due to insufficient output due to deterioration of the light source. In this case, there may be a case where light cannot be output to the synchronization detection sensor due to a rotation abnormality of the polygon motor or a change in lens characteristics due to a temperature change. Conventionally, for example, Patent Literatures 1, 2, and 3 have been proposed for specifying the cause of the synchronization signal abnormality.
Japanese Patent No. 3508364 JP 2003-326759 A JP 2003-57580 A

Conventionally, an abnormality in the synchronization signal can be detected, but it cannot be restored automatically. Therefore, after the user has stopped the image forming apparatus and restored it, the printing is resumed. So it was very inefficient.
An object of the present invention is to enable automatic recovery by resetting the light emission timing in the case of an abnormality in the synchronization signal.

  The invention according to claim 1 is a light source means, a light source control means for controlling the light source means to output an optical signal corresponding to the image signal, and for causing the light source means to emit light at a predetermined timing in line scanning of the optical signal, Rotating polygon mirror means that reflects an optical signal and exposes the reflected light signal by scanning in the main scanning direction and the sub-scanning direction on the photosensitive member, and main scanning light emitted at a predetermined timing in the reflected light signal Synchronization detection means arranged at a position where light can be received before the start, synchronization signal generation means for generating a synchronization signal in response to light reception of the synchronization detection means, error detection means for detecting a synchronization signal synchronization error, When the error detection means detects a synchronization error, it has an automatic return means for automatically resetting the generation of the synchronization signal by resetting the timing at which the light source emits light during line scanning of the optical signal. To.

  According to a second aspect of the present invention, in the first aspect of the present invention, when the error detecting means detects a synchronization error, a light source abnormality determining means for determining whether or not an abnormality has occurred in the light source means is provided. And

  According to a third aspect of the invention, in the second aspect of the invention, the automatic return means performs an operation stop process when an abnormality occurs in the light source means, and automatically when no abnormality occurs in the light source means. A return operation is started.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, when the error detecting means detects a synchronization error, it is determined whether or not an abnormality has occurred in the rotary polygon mirror means. A polygon mirror abnormality determining means is provided.

  The invention according to claim 5 is the invention according to claim 4, wherein the automatic return means performs an operation stop process when an abnormality occurs in the rotary polygon mirror means, and the abnormality occurs in the rotary polygon mirror means. If not, an automatic return operation is started.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the automatic return means includes a counting means for counting a light emission interval for causing the light source to emit light at a predetermined timing. The control means forcibly causes the light source means to emit light when a synchronization error is detected, and acquires the count value of the counter means when the synchronization error detection means normally detects the synchronization signal during the light emission, and synchronizes The detection position is estimated.

  The invention described in claim 7 is characterized in that, in the invention described in claim 6, when the synchronization is restored by the automatic return operation by the automatic return means, the light source control means causes the LD to emit light at the timing of the acquired count value. To do.

  The invention according to claim 8 is the invention according to claim 6 or 7, wherein an upper limit of the number of retries for obtaining the count value by the automatic return means is set, and when the upper limit is exceeded, the automatic return operation is not performed. Without stopping the operation.

  According to a ninth aspect of the present invention, there is provided the shutter according to any one of the first to eighth aspects, wherein shutter means for shielding an optical signal to the photosensitive member is provided during the automatic return operation by the automatic return means. To do.

  The invention according to claim 10 controls the light source to output an optical signal corresponding to the image signal, causes the light source to emit light at a predetermined timing in line scanning of the optical signal, and reflects the optical signal using a polygon mirror. The reflected light signal is exposed by scanning on the photosensitive member in the main scanning direction and the sub-scanning direction, and the light emitted at the predetermined timing in the reflected light signal can be received before the main scanning is started. Detects a sync signal in response to light reception, detects a sync error in the sync signal, and resets the timing for causing the light source to emit light in line scanning of the optical signal when a sync error is detected. It is characterized in that the occurrence of the error is automatically restored to normal.

  The invention described in claim 11 is characterized in that, in the invention described in claim 10, when a synchronization error is detected, it is determined whether or not an abnormality has occurred in the light source.

  According to a twelfth aspect of the invention, in the invention of the eleventh aspect, when an abnormality occurs in the light source, the operation is stopped, and when the abnormality does not occur in the light source, an automatic return operation is started. And

  A thirteenth aspect of the invention is characterized in that, in the invention according to any one of the tenth to twelfth aspects, when a synchronization error is detected, it is determined whether or not an abnormality has occurred in the rotary polygon mirror. .

  According to a fourteenth aspect of the present invention, in the invention of the thirteenth aspect, the operation is stopped when an abnormality occurs in the rotary polygon mirror, and the automatic return operation is started when no abnormality occurs in the rotary polygon mirror. It is characterized by doing.

  The invention according to claim 15 is the invention according to any one of claims 10 to 14, wherein in the automatic return operation, the counting means for counting the light emission interval for causing the light source to emit light at a predetermined timing is used. When an error is detected, the light source is forcibly emitted, and the synchronization detection position is estimated by acquiring the count value of the counter means when the synchronization signal is normally detected during the emission.

  The invention described in claim 16 is characterized in that, in the invention described in claim 15, when the synchronization is recovered by the automatic return operation, the LD is caused to emit light at the timing of the acquired count value.

  The invention described in claim 17 is the invention described in claim 15 or 16, wherein an upper limit of the number of retries for obtaining the count value is set, and when the upper limit is exceeded, the automatic return operation is not performed. It is characterized by stopping.

  According to an eighteenth aspect of the present invention, in the invention according to any one of the tenth to seventeenth aspects, the optical signal to the photosensitive member is shielded during the automatic return operation.

  The invention according to claim 19 controls the light source to output an optical signal corresponding to the image signal, and causes the light source to emit light at a predetermined timing in line scanning of the optical signal, and reflects the optical signal, Rotating polygon mirror control process that scans the reflected light signal in the main scanning direction and sub-scanning direction on the photoconductor and exposes the light emitted at the specified timing in the reflected light signal before starting the main scanning Detection error detected at a predetermined position, synchronization signal generation process that generates a synchronization signal in response to light reception, error detection process that detects a synchronization signal synchronization error, and error detection process detected a synchronization error When the optical signal line scan is performed, the computer is caused to execute automatic return processing for resetting the timing for causing the light source to emit light and automatically returning the generation of the synchronization signal to normal. To.

  According to a twentieth aspect of the invention, in the invention of the nineteenth aspect, when a synchronization error is detected by the error detection process, the computer is caused to execute a light source abnormality determination process for determining whether an abnormality has occurred in the light source. Features.

  According to a twenty-first aspect of the invention, in the invention of the twentieth aspect, the operation stop process is executed when an abnormality occurs in the light source, and the automatic return process is executed when no abnormality occurs in the light source. It is characterized by.

  According to a twenty-second aspect of the invention, in the invention according to any one of the nineteenth to twenty-first aspects, when a synchronization error is detected, a polygonal mirror abnormality determination process for determining whether an abnormality has occurred in the rotary polygon mirror Is executed by a computer.

  According to a twenty-third aspect of the invention, in the invention of the twenty-second aspect, when an abnormality has occurred in the rotating polygon mirror, an operation stop process is performed, and when no abnormality has occurred in the rotating polygon mirror, an automatic return process is performed. It is characterized by performing.

  According to a twenty-fourth aspect of the invention, in the invention according to any one of the nineteenth to twenty-third aspects, a counting process for counting a light emission interval for causing a light source to emit light at a predetermined timing and a synchronization error are detected. , Causing the computer to execute a light emission process for forcibly causing the light source to emit light, and an estimation process for estimating a synchronization detection position by obtaining a count value by a counter process when the synchronization signal is normally detected during the light emission. Features.

  According to a twenty-fifth aspect of the invention, in the twenty-fourth aspect of the invention, when synchronization is restored by the automatic return operation process, the computer is caused to execute a light emission process for causing the LD to emit light at the timing of the acquired count value. .

  According to a twenty-sixth aspect of the invention, in the invention of the twenty-fourth or twenty-fifth aspect, an upper limit is set for the number of retries for obtaining the count value, and when this upper limit is exceeded, the operation is stopped without performing an automatic return operation. It is characterized by performing processing.

  According to a twenty-seventh aspect of the present invention, in the invention according to any one of the nineteenth to twenty-sixth aspects, when the automatic return operation is performed, the computer executes a shielding process for shielding an optical signal to the photosensitive member with a shutter. To do.

  The invention according to claim 28 is characterized in that the program according to any one of claims 19 to 27 is recorded.

  According to the first, tenth and nineteenth aspects of the present invention, it is possible to avoid outputting an abnormal image by detecting a synchronization error, and to form an image without stopping the image forming apparatus even if a synchronization abnormality occurs. It can be in a resumable state.

According to the second, eleventh and twentieth aspects of the invention, it can be estimated that the cause of the synchronization error is an LD abnormality.
According to the third, twelfth, and twenty-first aspects of the present invention, it is possible to make it possible to resume image formation without stopping the image forming apparatus even if a synchronization abnormality that can be automatically restored occurs.
According to the inventions of claims 4, 13 and 22, it can be estimated that the cause of the synchronization error is an abnormality of the polygon mirror means.
According to the fifth, fourteenth and twenty-third aspects of the present invention, it is possible to resume image formation without stopping the image forming apparatus even when a synchronous abnormality that can be automatically restored due to, for example, a change in lens characteristics occurs. It can be in a state.

According to the sixth, fifteenth and twenty-fourth aspects of the present invention, it is possible to estimate how many count values will be the synchronization detection position.
According to the inventions of claims 7, 16 and 25, the synchronization can be reliably recovered by the automatic return operation.
According to the inventions of claims 8, 17 and 26, when the operation for acquiring the count value continues to fail, the automatic return operation can be prevented from falling into an infinite loop.
According to the inventions of claims 9, 18, and 27, it is possible to avoid damaging the photosensitive member during the automatic return operation.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a portion related to the present invention of the image forming apparatus according to the first embodiment of the present invention.
In FIG. 1, during normal operation, the LD control unit 1 controls a light irradiation device 2 using an LD (laser diode) as a light source based on an image signal obtained from a scanner or the like (not shown), and performs light irradiation. The device 2 outputs an optical signal corresponding to the image signal. The optical signal output from the light irradiation device 2 is reflected by a polygon mirror (rotating polygon mirror) 4 that is rotated by a polygon motor controlled by the polygon control unit 3. The reflected optical signal is exposed by being subjected to main scanning and sub scanning on the photosensitive member 6 through the lens 5, and an electrostatic latent image is formed on the photosensitive member 6.

  On the other hand, the synchronization sensor 7 is a mirror installed at a predetermined position that can detect light in a non-image area in an optical signal that has passed through the lens 5 when normal synchronization is established. The light in the non-image area detected by the synchronization sensor 7 is received by the synchronization signal generator 8, and based on this, the synchronization signal generator 8 generates a synchronization signal and outputs it to the synchronization error detection unit 9. The LD control unit 1 causes the LD to emit light at the timing of the non-image area of the image signal. This light emission is performed at the timing of a predetermined count value of the main scanning counter 10 that operates at the synchronization signal generation interval.

Next, the normal sequence operation of the automatic return operation according to the present invention will be described with reference to FIGS. FIG. 2 shows a flowchart of the automatic return operation.
The synchronization error detector 9 detects the synchronization signal from the synchronization signal generator 8 (S1), and determines whether or not a synchronization signal is output (S2). If the synchronization signal is not output, the general abnormality detection unit 11 is notified as a synchronization error. The general abnormality detection unit 11 first checks whether there is an abnormality in the LD and the polygon motor (S3) (S4). If there is no abnormality in the LD and the polygon motor, the automatic return control unit 12 is requested to execute the automatic return operation.

  The automatic return control unit 12 controls the LD control unit 1 to force the LD of the light irradiation device 2 to emit light continuously. At this time, as shown in FIG. 3, the shutter 13 is operated to shield the optical signal from the lens 5 so that the photosensitive member 6 is not irradiated with light. When the LD emits light continuously, one-line scanning is performed (S5). Since the light from the LD is detected somewhere during the one-line scanning by the synchronization sensor 7, a synchronization signal is output from the synchronization signal generator 8. The count value of the main scanning counter 11 at that time is stored (S6). If the count value during one line scanning can be acquired, the detection position of the synchronous sensor 7 can be estimated.

  In FIG. 4, before the automatic return operation, the synchronization signal is not input due to a synchronization abnormality while the count value of the main scan counter 10 for one line scan is “10000”, and one line scan is performed by the automatic return operation. When the counter value is acquired by this method, an example of “8000” is shown. That is, if the LD is lit at the position where the count value is “10000”, the count value per line changes due to a change in the characteristics of the lens 4, for example, when the sync sensor 7 is at the sync signal detection position. Thus, if the light is not lit at the position of the count value “8000”, it cannot be detected by the synchronous sensor 7. Even if the LD is lit at the position where the count value is “10000” in this state, the light passes through the synchronization sensor 7, so that a synchronization signal cannot be generated. Therefore, when the count value is set to “8000” during the automatic return operation, it can be estimated that this is the synchronization signal detection position. Therefore, thereafter, if the position where the LD is lit is 8000 counts, the LD can be lit at the synchronization signal detection position.

  When the automatic return control unit 12 acquires the count value as described above (S7, Yes), the automatic return is performed by resetting the LD lighting position for detecting the synchronization signal based on the count value (S8). End control. Thereafter, the operation returns to the normal operation, and the synchronization error detection unit 9 detects again whether the synchronization signal is output (S9).

Next, the abnormal series operation of the automatic return operation will be described.
When the synchronization error detection unit 9 determines that the synchronization signal is not output and notifies the synchronization error to the total abnormality detection unit 11, when the LD abnormality is confirmed (S3, No), the total abnormality detection unit 11 performs the LD. As an abnormality, the LD control unit 1 and the polygon control unit 3 that controls the polygon motor are stopped (S10). Further, when the synchronization error detection unit 9 determines that no synchronization signal is output and notifies the general abnormality detection unit 11 of the synchronization error, if the polygon abnormality is confirmed (S4, No), the general abnormality detection unit 11 Stops the LD control unit 1 and the polygon control unit 3 as a polygon abnormality.

  If the count value acquisition fails during the automatic return operation (S7, No), the count value acquisition is continued until a certain number of retries is exceeded. When the count value can be acquired before the number of retries exceeds the upper limit, the above-described normal series operation is advanced. When the number of retries exceeds the upper limit, the general abnormality detection unit 11 stops the LD control unit 1 and the polygon control unit 3 as a synchronization detection abnormality.

According to the present embodiment described above, the following operational effects can be obtained.
When a synchronization error occurs, an abnormal image is formed on the photosensitive member 6 because the image formation timing of the main scan cannot be taken, but according to the present embodiment, by detecting the synchronization error, It is possible to avoid outputting an abnormal image.
-It can automatically recover from a synchronization error.
-If an LD error occurs when a synchronization error has occurred, synchronization detection may not be possible due to light intensity deterioration. According to this embodiment, an LD error is detected when a synchronization error occurs. By doing so, the cause of the synchronization error can be estimated.
Even if a synchronization abnormality that can be automatically restored due to, for example, a characteristic change of the lens 4 occurs, it is possible to resume image formation without stopping the image forming apparatus.

• If a rotation error has occurred in the polygon motor when a synchronization error has occurred, light cannot be irradiated to the synchronization detection position even if the light irradiation timing is normal. Therefore, the cause of the synchronization error can be estimated by detecting the abnormality of the polygon motor when the synchronization error occurs.
In the case of a synchronization abnormality that can be automatically restored, it is possible to return to a state in which image formation can be resumed without stopping the image forming apparatus.
-It is possible to estimate how many count values the synchronization detection position will be.
-Since the upper limit of the number of retries for acquiring the count value is determined, the automatic return operation can be prevented from falling into an infinite loop when the automatic return operation continues to fail.
Since the photosensitive member 6 is shielded by the shutter 13 during the automatic return operation, it is possible to avoid damaging the photosensitive member.

  A program for the CPU of the image forming apparatus to execute the processing shown in the flowchart of FIG. 2 constitutes a program according to the present invention. The recording medium for recording the program constitutes a computer-readable recording medium according to the present invention. As this recording medium, a semiconductor storage device, an optical and / or magnetic storage device, or the like can be used. By using such a program and recording medium in an apparatus or system having a configuration different from that of the above-described embodiment and causing the CPU to execute the program, substantially the same effect as the present invention can be obtained. .

1 is a block diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a flowchart which shows an automatic return operation | movement. 2 is a block diagram illustrating an image forming apparatus when a shutter operates. FIG. It is a block diagram which shows the example of the count value at the time of normal operation | movement, and the count value acquired by automatic return operation | movement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 LD control part 2 Light irradiation device 3 Polygon control part 4 Polygon mirror 5 Lens 6 Photoconductor 7 Synchronization sensor 8 Synchronization signal generator 9 Synchronization error detection part 10 Main scanning counter 11 Comprehensive abnormality detection part 12 Automatic return control part 13 Shutter

Claims (28)

Light source means;
A light source control means for controlling the light source means to output an optical signal corresponding to an image signal, and for causing the light source means to emit light at a predetermined timing in line scanning of the optical signal;
Rotating polygon mirror means for reflecting the optical signal and scanning the reflected light signal in the main scanning direction and the sub-scanning direction on the photosensitive member;
Synchronization detecting means disposed at a position where the light emitted at the predetermined timing in the reflected light signal can be received before the start of the main scanning;
Synchronization signal generating means for generating a synchronization signal in response to reception of the light of the synchronization detection means;
Error detection means for detecting a synchronization error of the synchronization signal;
When the error detection means detects a synchronization error, it further comprises an automatic return means for automatically resetting the generation of the synchronization signal by resetting the timing at which the light source emits light in line scanning of the optical signal. An image forming apparatus.   2. The image forming apparatus according to claim 1, further comprising a light source abnormality determining unit configured to determine whether or not an abnormality has occurred in the light source unit when the error detecting unit detects a synchronization error.   3. The automatic return means performs an operation stop process when an abnormality occurs in the light source means, and starts an automatic return operation when no abnormality occurs in the light source means. The image forming apparatus described.   4. A polygon mirror abnormality determining means for determining whether or not an abnormality has occurred in the rotating polygon mirror means when the error detection means detects a synchronization error. The image forming apparatus described in the item.   The automatic return means performs an operation stop process when an abnormality occurs in the rotary polygon mirror means, and starts an automatic return operation when no abnormality occurs in the rotary polygon mirror means. The image forming apparatus according to claim 4.   The automatic return means includes counting means for counting a light emission interval for causing the light source to emit light at the predetermined timing, and the light source control means forcibly turns on the light source means when the synchronization error is detected. The light emission is performed, and the synchronization detection position is estimated by acquiring the count value of the counter means when the synchronization error detection means normally detects the synchronization signal during the light emission. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 6, wherein when synchronization is recovered by an automatic return operation by the automatic return unit, the light source control unit causes the LD to emit light at the timing of the acquired count value.   An upper limit of the number of retries for obtaining the count value by the automatic return means is set, and when the upper limit is exceeded, the operation stop process is performed without performing an automatic return operation. 8. The image forming apparatus according to 6 or 7.   9. The image forming apparatus according to claim 1, further comprising: a shutter unit configured to shield the optical signal with respect to the photosensitive member during an automatic return operation by the automatic return unit. 10. The light source is controlled to output an optical signal corresponding to the image signal, and the light source emits light at a predetermined timing in line scanning of the optical signal,
The optical signal is reflected using a polygon mirror, and the reflected light signal is scanned and exposed on the photosensitive member in the main scanning direction and the sub-scanning direction,
Detecting light emitted at the predetermined timing in the reflected light signal at a predetermined position where light can be received before the main scanning starts,
Generating a synchronization signal in response to receiving the light,
Detecting a synchronization error in the synchronization signal;
An image forming method, wherein when the synchronization error is detected, a timing for causing the light source to emit light is reset in line scanning of the optical signal so that the generation of the synchronization signal is automatically automatically restored.   The image forming method according to claim 10, wherein when the synchronization error is detected, it is determined whether an abnormality has occurred in the light source.   12. The image forming method according to claim 11, wherein when the abnormality occurs in the light source, the operation is stopped, and when the abnormality does not occur in the light source, the automatic return operation is started.   13. The image forming method according to claim 10, wherein when the synchronization error is detected, it is determined whether an abnormality has occurred in the rotary polygon mirror.   14. The image forming according to claim 13, wherein when the abnormality occurs in the rotary polygon mirror, the operation is stopped, and when the abnormality does not occur in the rotary polygon mirror, the automatic return operation is started. Method.   In the automatic return operation, a counting unit that counts a light emission interval for causing the light source to emit light at the predetermined timing is used, and when the synchronization error is detected, the light source is forced to emit light, and during this light emission, The image forming method according to any one of claims 10 to 14, wherein the synchronization detection position is estimated by obtaining a count value of the counter means when the synchronization signal is normally detected.   16. The image forming method according to claim 15, wherein when the synchronization is restored by the automatic return operation, the LD is caused to emit light at the timing of the acquired count value.   The image formation according to claim 15 or 16, wherein an upper limit of the number of retries for acquiring the count value is set, and when the upper limit is exceeded, the operation is stopped without performing the automatic return operation. apparatus.   The image forming method according to claim 10, wherein the optical signal to the photoconductor is shielded during the automatic return operation. A light source control process for controlling the light source and outputting an optical signal corresponding to the image signal, and causing the light source to emit light at a predetermined timing in line scanning of the optical signal;
A rotary polygon mirror control process that reflects the optical signal, scans the reflected light signal in the main scanning direction and the sub-scanning direction on the photosensitive member, and exposes the reflected light signal;
A detection process for detecting light emitted at the predetermined timing in the reflected light signal at a predetermined position where the light can be received before the start of the main scanning;
A synchronization signal generation process for generating a synchronization signal in response to reception of the light;
An error detection process for detecting a synchronization error in the synchronization signal;
When a synchronization error is detected by the error detection processing, the computer is caused to execute automatic return processing for automatically resetting the generation of the synchronization signal by resetting the timing at which the light source emits light in line scanning of the optical signal. program.   The program according to claim 19, wherein when a synchronization error is detected by the error detection process, the computer executes a light source abnormality determination process for determining whether an abnormality has occurred in the light source.   The program according to claim 20, wherein an operation stop process is executed when an abnormality occurs in the light source, and the automatic return process is executed when no abnormality occurs in the light source.   The program according to any one of claims 19 to 21, which causes a computer to execute a polygon mirror abnormality determination process for determining whether an abnormality has occurred in the rotary polygon mirror when the synchronization error is detected.   23. The program according to claim 22, wherein an operation stop process is performed when an abnormality has occurred in the rotary polygon mirror, and the automatic return process is executed when no abnormality has occurred in the rotary polygon mirror.   Count processing for counting the light emission interval for causing the light source to emit light at the predetermined timing, light emission processing for forcibly causing the light source to emit light when the synchronization error is detected, and the synchronization signal during the light emission. The program according to any one of claims 19 to 23, which causes a computer to execute estimation processing for acquiring a count value obtained by the counter processing when normally detected and estimating a synchronization detection position.   25. The program according to claim 24, wherein when synchronization is restored by the automatic return operation process, the computer executes a light emission process for causing the LD to emit light at the timing of the acquired count value.   26. The program according to claim 24, wherein an upper limit of the number of retries for acquiring the count value is set, and when the upper limit is exceeded, the operation stop process is performed without performing an automatic return operation. .   27. The program according to claim 19, further causing a computer to execute a shielding process for shielding the optical signal to the photosensitive member with a shutter during the automatic return operation.   A computer-readable recording medium on which the program according to any one of claims 19 to 27 is recorded.

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