JP2002311355A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To previously prevent a situation that a scanning position in a subscanning direction by a laser beam is deviated in an image forming device and the device can not be used, and to decrease the influence of the deviation to the minimum. SOLUTION: A synchronization detection sensor 20 is provided with a 1st photodetector part 21 and a 2nd photodetector part 22 arranged to be inclined by an angle θ to the 1st photodetector part 21. The time from detecting a laser spot 13 scanning in a direction shown by an arrow (a) by the 1st photodetector part 21 until detecting the laser spot 13 by the 2nd photodetector part 22 is measured, and an abnormality signal is outputted when the measured time is out of a specified range set in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming an image by scanning a laser beam emitted from a laser light source.
The present invention relates to an image forming apparatus such as a digital copier, a laser printer, and a facsimile machine.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus for forming an image by scanning a laser beam emitted from a laser light source, a synchronous sensor for detecting the laser beam is provided on a scanning optical path, and the synchronous sensor detects the laser beam. Control of the timing of the lighting control of the laser light source, that is, control of the image forming start position, is performed according to the detection timing. Here, a writing unit in a conventional image forming apparatus will be described first with reference to FIGS.
FIG. 11 is a schematic plan view showing the arrangement of the writing unit and the photoconductor, and FIG. 12 is a side view thereof.

As shown in FIGS. 11 and 12, a writing unit in a conventional image forming apparatus includes a laser diode (LD) unit 1, a polygon mirror 3, a motor 4,
a θ lens 5, a mirror 7, a cylindrical lens 9, a synchronization detection mirror 10, and a synchronization detection sensor 11. The laser beam emitted from the LD unit 1 is
An image is formed on the reflection surface of the polygon mirror 3 by the cylindrical lens 9, and the polygon mirror 3 rotated by the motor 4 deflects and scans in the main scanning direction. The laser beam passes through an fθ lens 5 serving as an image forming means for forming an image on the photosensitive drum 6 and scanning at a constant speed, is reflected toward the photosensitive drum 6 by a mirror 7, and is reflected by a driving source. The scanning is performed on the photosensitive drum 6 that is driven to rotate.

Here, a polygon mirror 3 as a deflecting means is used.
Is rotated by the motor 4, but the number of rotations is switched according to the recording density and the recording mode. For example, when the rotation speed of the photosensitive drum 6 is constant, the recording density is 400 dpi.
In the case of (1) and the case of 600 dpi, the polygon mirror 3 is rotated at a rotation speed 1.5 times higher in the case of 600 dpi than in the case of 400 dpi. That is, the scanning speed of the laser beam is 400 dpi in the case of 600 dpi.
1.5 times faster than in the case of i. The number of rotations of the polygon mirror 3 depends on not only the recording density but also the recording mode,
For example, switching may be performed even when the rotation speed of the photosensitive drum 6 is changed by setting a high definition mode or the like.

[0005] The LD unit 1 is modulated based on an image signal by an LD drive circuit, and a laser beam modulated based on the image signal is emitted from the LD unit 1 to scan the photosensitive drum 6 as described above. . The surface of the photoreceptor drum 6 is uniformly charged by a well-known charging unit, and then is scanned and exposed by a laser beam to form an electrostatic latent image based on an image signal. The electrostatic latent image on the photosensitive drum 6 is developed by a developing unit into a toner image, and is transferred to a transfer material such as a transfer paper or an intermediate transfer belt by a transfer unit. After that, the photosensitive drum 6 is removed of residual toner and the like by the cleaning device, and is discharged by the discharging unit to prepare for the next image forming operation. The laser beam that has passed through the fθ lens 5 is reflected by the synchronization detection mirror 10 outside the image writing area, and guided to the synchronization detection sensor 11 that is a beam detection unit. When the synchronization detection sensor 11 detects the laser beam, a synchronization signal serving as a reference for the image forming position in the main scanning direction is obtained.

Next, a synchronous detection sensor in a conventional image forming apparatus will be further described with reference to FIGS. FIG. 13 shows the arrangement of the synchronization detection sensor, and FIG.
FIG. 4 is a diagram showing the relationship between the detection signal and the image signal. As shown in FIG. 13, the shape of the light receiving portion 12 of the synchronization detection sensor 11 in the conventional image forming apparatus is such that the width wa in the scanning direction (main scanning direction) of the laser beam is small, and the width wa is perpendicular to the scanning direction (sub scanning direction). Has a large width wb. This is so that the laser beam can be detected even when the scanning position of the beam spot 13 is slightly shifted in the sub-scanning direction. Then, as shown in FIG. 14, when the synchronization detection sensor 11 detects the laser beam and outputs a detection signal, the transfer of the image signal to the LD drive circuit is started after a lapse of a predetermined time T, and the writing of the image is started. Is done.

By the way, even if the length of the light receiving section 12 is long in the sub-scanning direction, the scanning position of the laser beam in the sub-scanning direction fluctuates due to environmental fluctuations and the like. In some cases, a problem that detection cannot be performed may occur. Since image formation cannot be performed unless the laser beam can be detected by the synchronization detection sensor 11, this problem causes a serious problem that the image forming apparatus cannot be used. However, if the width wb in the sub-scanning direction of the light receiving unit 12 of the synchronization detection sensor 11 is increased to solve this problem, the area of the light receiving unit 12 increases. Then, the detection sensitivity of the laser beam deteriorates, and a detection timing shift occurs. That is, since the rise time of the detection signal becomes longer, the image writing position varies due to the fluctuation of the light amount of the laser beam, and the image quality deteriorates. For this reason, the width Wb of the light receiving unit 12 in the sub-scanning direction is limited to 2 mm to 3 mm, and it is not possible to sufficiently cover a range in which the scanning position of the laser beam may shift.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention solves such a problem, and promptly prompts the user when the scanning position of the laser beam in the sub-scanning direction exceeds an allowable range in the image forming apparatus. It is an object of the present invention to notify a user of an image or to make an automatic correction to prevent a situation in which the image forming apparatus cannot be used due to the shift, and to minimize the influence of the shift.

[0009]

In order to achieve the above object, the present invention provides a beam generating means for generating a laser beam modulated based on an image signal, and deflects a laser beam emitted by the beam generating means. Deflecting means for scanning the photoreceptor by scanning, and a first beam detecting means for detecting a laser beam deflected by the deflecting means at a predetermined position,
In an image forming apparatus for determining an image forming start position in response to a detection signal from the first beam detecting means, a second light emitting element arranged in a direction different from the first beam detecting means in the vicinity of the first beam detecting means. 2 beam detecting means, time measuring means for measuring the time from when the first beam detecting means detects the laser beam to when the second beam detecting means detects the laser beam, and the time An abnormal signal output unit that outputs an abnormal signal when the time measured by the measuring unit deviates from a predetermined range set in advance.

[0010] In such an image forming apparatus, it is preferable to provide a display section for displaying an operation state and a message of the apparatus, and means for displaying a predetermined message on the display section when the abnormal signal is output. Alternatively, there may be provided a notifying means for notifying a preset partner of the details of the abnormality when the abnormality signal is output. Further, instead of the abnormal signal output means, the incident position of the laser beam in the sub-scanning direction with respect to the first beam detection means and the second beam detection means is adjusted according to the time measured by the time measurement means. May be provided.

At this time, the incident position adjusting means adjusts the position or direction of the mirror for reflecting the laser beam toward the first beam detecting means and the second beam detecting means, thereby adjusting the incident position. Can be adjusted. Alternatively, instead of the abnormal signal detecting means, a detecting position adjusting means for adjusting the positions of the first beam detecting means and the second beam detecting means according to the time measured by the time measuring means may be provided. Good.

[0012]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. First, a digital copying machine which is a first embodiment of the image forming apparatus of the present invention will be described with reference to FIGS. FIG. 1 is a schematic plan view showing an arrangement relationship between a synchronization detection sensor and a photosensitive drum of the digital copying machine. FIG. 2 is a waveform diagram showing an example of a detection signal when a beam spot passes over the synchronization sensor. FIG. 3 is a block diagram showing the configuration of the digital copying machine of this embodiment, FIG. 4 is a diagram showing an example of an optical path when the scanning position of the beam spot is shifted, and FIG. FIG. 6 is a waveform diagram showing a detection signal by the synchronization detection sensor at the position shown by the arrow b, and FIG. 6 is a waveform diagram showing a detection signal at the position shown by the arrow c.

As shown in FIG. 3, this digital copying machine has:
It comprises a control circuit 41, an image reading unit 42, an image forming unit 43, and an operation display unit 44. The control circuit 41
CPU 45, ROM 46, RAM 47, network I
/ F (interface) 48. This CPU
Reference numeral 45 denotes a central processing unit, which performs overall control of the entire digital copying machine, such as processing control codes and image data, by using a control program stored in a ROM 46.

The ROM 46 stores control programs and parameters used by the CPU 45 for processing and managing data and controlling peripheral modules. In addition, ROM
By configuring 46 with a rewritable nonvolatile storage medium such as an EPROM, it becomes possible to update control programs and parameters. The RAM 47 is a random access memory, and is used as a work memory used when the CPU 45 performs data processing, an image memory for storing image data, and the like. Network I / F4
8 is a public line or a local area network (LA
N) is an interface for exchanging information with an external device through N). This digital copying machine communicates with an SS terminal 49 installed in a maker's service station (SS) via this network I / F 48. It is possible to do.

The image reading section 42 is an image scanner for reading an image of a document. The image forming unit 43 includes an image forming unit including a photoconductor and process devices around the photoconductor, a writing unit that optically scans the photoconductor with a laser beam that is modulated according to an image signal, A mechanism unit including a sheet transport unit including rollers such as a pair of registration rollers, and an engine driver serving as a control unit of the mechanism unit. The sequence operation of the image forming unit and the sheet transport unit is performed by a command from CPU 45 and printing or drawing data. The image forming process is performed by controlling the writing unit. The display operation unit 44 includes an operation unit for setting an operation mode of the digital copying machine, and a display unit including an LCD for displaying an operation state and a message.

A feature of this digital copying machine is a portion relating to a synchronization detection sensor which is a beam detection means in a writing unit of the image forming section 43. Next, this point will be described. Regarding the configuration of the writing unit, only the conventional image forming apparatus described with reference to FIGS. 11 to 14 will be described except for the configuration of the portion related to the synchronization detection sensor. However,
In this embodiment, the LD unit 1 shown in FIG. 11 corresponds to a beam generating unit, and the polygon mirror 3 corresponds to a deflecting unit.

In this embodiment, instead of the conventional synchronous detection sensor 11 shown in FIG. 13, a synchronous detection sensor 20 having a first light receiving section 21 and a second light receiving section 22 as shown in FIG. Is provided. Here, the first and second light receiving sections 21 and 22 are optical sensors, respectively. The first light receiving section 21 is a first beam detecting means, and the second light receiving section 22 is a second light detecting section.
Is a beam detecting means. The first light receiving unit 21 is configured as shown in FIG.
And a light-receiving unit corresponding to the light-receiving unit 12 described above, and an image forming start position on the photoconductor 6 is determined according to a detection signal from the light-receiving unit. Then, the second light receiving unit 22 is configured as shown in FIG.
As shown in the figure, the first light receiving portion 21 is disposed in the vicinity of the first light receiving portion 21 at a tilt angle θ with respect to the longitudinal direction of the first light receiving portion 21. Detect the beam.

Here, an arrow a shown in FIG. 1 indicates a normal scanning position of the beam spot 13. When the beam spot 13 scans this position, first, the first light receiving unit 2
1 detects the beam, and then the second light receiving section 22 detects the beam. And the two light receiving sections 21 and 22
As shown in FIG. 2, a time difference t depending on the distance between them and the scanning speed of the beam spot 13 is shown in FIG.
a occurs. The CPU 45 measures the time difference ta, that is, the time from when the first light receiving unit 21 detects the beam to when the second light receiving unit 22 detects the beam, by a software counter, and continuously or at a fixed timing. Monitored by Here, the CPU 45 functions as time measuring means.

When the incident position of the beam spot 13 on the synchronization detecting sensor 20 is shifted in the sub-scanning direction due to environmental fluctuation or the like, arrows b and c shown in FIG.
It is possible to scan the position of. Second light receiving unit 22
Are tilted with respect to the first light receiving unit 21, so that when the incident position in the sub-scanning direction changes, the first light receiving unit 21 and the second light receiving unit 22 on the scanning optical path of the beam spot 13 change. The distance between and also changes. Therefore, for example, when the incident position of the beam spot 13 shifts upward in the figure as shown by an arrow b, as shown in FIG.
The time difference of the detection signal by 22 is larger than ta when the incident position is the normal position, and becomes tb (tb> ta). Conversely, when the incident position of the beam spot 13 shifts downward in the figure as shown by the arrow c, the time difference between the detection signals by the two light receiving units 21 and 22 decreases from ta to tc as shown in FIG. (Tc <ta).

As described above, when the scanning position of the beam spot 13 changes, the time difference between the detection signals of the two light receiving sections 21 and 22 also changes accordingly, and the time difference is measured to scan the beam spot 13. The position can be detected. Then, the CP shown in FIG.
U45 monitors this time difference, and if this time difference deviates from a predetermined range, issues an abnormal signal indicating that the state of the apparatus is abnormal. Here, C
The PU 45 functions as an abnormal signal output unit. The above range is, for example, tc as the minimum value tmin.
May be set to tb as the maximum value tmax. Further, the time ta in the case of the normal scanning position naturally varies depending on the scanning speed of the beam spot 13, so that the range of the time difference is set according to the scanning speed (that is, the rotation speed of the polygon mirror 3).

When the above-mentioned abnormal signal is issued, the CPU 45 simultaneously displays the message "Please contact the service station. Telephone number: 0120-****"
A predetermined message such as “*” is displayed, and the user is informed of the abnormality of the device, and urged to request a repair. In this case,
The CPU 45 also functions as a unit for displaying a predetermined message on the display unit when an abnormal signal is output. Alternatively, the abnormality may be automatically reported by connecting to the SS terminal 48 provided in the service station (SS) via the network I / F 47. In this case,
The CPU 45 and the network I / F 47 function as reporting means. The report destination is not limited to the SS terminal 48,
For example, it may be a personal computer or the like of a person in charge of management of a device connected by a LAN.

As described above, when an abnormality occurs, the abnormality is promptly detected and reported to the user or SS, whereby
The deviation of the scanning position of the beam spot 13 becomes large, and the incident position on the synchronization detection sensor 20 deviates from its light receiving portion,
Before the image formation becomes impossible, the repair of the apparatus can be prompted. Further, if the notification is automatically made to the SS, the trouble of the user requesting the repair can be saved. The deviation of the scanning position can be easily repaired by adjusting the scanning position by adjusting the inclination of the synchronization detection mirror or by moving the beam detection sensor. By the way, in this embodiment, the first and second light receiving portions 21 of the synchronization detection sensor 20 are provided.
Although the example shown in FIG. 1 has been described as the arrangement of the 22, the arrangement of the first and second light receiving sections 21 and 22 is not limited to this.

For example, as in a synchronization detection sensor 20 shown in FIG. 7, the second light receiving section 2 which is longer than the first light receiving section 21 is provided.
2 'may be arranged with a large inclination angle. When the inclination angle is increased in this manner, the change in the distance between the two light receiving sections 21 and 22 'with respect to the shift in the incident position of the beam spot increases, and the change in the time difference between the detection signals also increases. The resolution of detection is improved. On the other hand, if the second light receiving portion 22 'is lengthened, the light receiving area increases and the sensitivity decreases. However, since the detection signal from the second light receiving portion 22' is not used to determine the image formation start position, There is no problem even if the sensitivity is slightly lowered. In addition, as in the synchronization detection sensor 20 shown in FIG.
2 is arranged on the upstream side of the scanning from the first light receiving unit 21,
The same effect as in the case of the arrangement as shown in FIG. 1 can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 9 is a diagram showing a configuration of a portion related to a synchronization detection sensor in the digital copying machine. In this embodiment, the first point is that a means for adjusting the direction of the synchronization detection mirror 10 is provided, and when the scanning position of the beam spot is shifted, the direction is corrected by adjusting the direction of the synchronization detection mirror 10. It is only different from the embodiment. Therefore, the other description is omitted.

In this embodiment, the synchronization detecting mirror 10 is mounted on an optical housing 31 and supported by an actuator 30 fixed to the optical housing 31. The synchronization detecting mirror 10 is pressed against the actuator 30 and the optical housing 31 by leaf springs 32 and 33. Actuator 30
The protrusion amount can be changed by moving the protrusion portion 30a in the direction of arrow d. Then, the synchronization detecting mirror 1 is pressed against the pressing of the leaf springs 32 and 33 accordingly.
0 can be rotated around the contact point with the optical housing 31 to adjust its direction. When the direction of the synchronization detection mirror 10 is changed, the scanning optical path of the laser beam reflected thereby (indicated by a dashed line in FIG. 9) naturally changes, and the incident position of the beam on the synchronization detection sensor 20 is changed in the direction of arrow e ( (Sub-scanning direction).

The synchronization detecting sensor 20 also has the first and second light receiving portions 21, 21 as in the first embodiment shown in FIG.
The detection signal from each light receiving section is input to the control circuit 41, and the control circuit 4
When the CPU 1 determines that adjustment of the incident position of the laser beam is necessary, the CPU 30 controls the actuator drive circuit 34 to drive the actuator 30 to adjust the incident position. Also in this embodiment, the CPU of the control circuit 41
Monitors the deviation of the scanning position of the beam spot based on the time difference between the detection signals from the first and second light receiving units 21 and 22. Then, when the shift of the scanning position (time difference of the detection signal) reaches a predetermined amount, for example, the scanning position of the beam spot shifts to the position shown by the arrow b or c in FIG. 4 and the time difference becomes tb or tc. In this case, the actuator 30 is driven to drive the synchronization detecting mirror 10 as described above.
Is adjusted, and the incident position of the laser beam in the sub-scanning direction on each light receiving unit of the synchronization detection sensor 20 is adjusted. As the adjustment amount at this time, for example, a movement amount from a position indicated by an arrow b or c in FIG. 4 to a position indicated by an arrow a in FIG. 1 can be determined in advance. Here, the control circuit 41, the actuator drive circuit 34, and the actuator 30 are incident position adjusting means.

By performing such adjustment, when the deviation of the scanning position of the beam spot reaches a certain amount, the deviation can be automatically repaired. Can be prevented from being disengaged from the light receiving section. Here, an example in which the adjustment is performed when the deviation of the scanning position of the beam spot reaches a predetermined amount has been described. However, if the scanning position is slightly deviated, the adjustment is immediately performed, and the scanning position is always set to a normal value. The position may be set. Also, here, an example in which the incident position of the beam is adjusted by adjusting the direction of the synchronization detection mirror 10 has been described. The incident position may be adjusted by moving in the direction and adjusting the position of the synchronization detection mirror 10.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 10 is a diagram showing a configuration of a portion related to a synchronization detection sensor in the digital copying machine. In this embodiment, a means for adjusting the position of the synchronization detection sensor 20 is provided, and when the scanning position of the beam spot is shifted, the position is corrected by adjusting the position of the synchronization detection sensor 20 as the first point. The only difference is the digital copying machine of the embodiment. Therefore, the other description is omitted.

In this embodiment, the synchronization detection sensor 20 is mounted on a substrate 39, and the substrate 39 is pressed against the optical housing 35 and the actuator 36 by compression springs 37, 38 fixed to the optical housing 35. . The actuator 36 is fixed to the optical housing 35, and the protrusion 36a is viewed from an arrow e.
The amount of protrusion can be changed by moving in the direction. Then, the substrate 39 can be moved in the direction of arrow e against the pressing of the compression springs 37 and 38 accordingly. When the substrate 39 is moved, the position of the synchronization detection sensor 20 naturally moves, and the incident position of the laser beam on the synchronization detection sensor 20 can be adjusted in the direction of arrow e (sub-scanning direction).

The synchronization detecting sensor 20 also has the first and second light receiving portions 21 and the same as in the first embodiment shown in FIG.
The detection signal from each light receiving section is input to the control circuit 41, and the control circuit 4
If the CPU 1 determines that the position of each light receiving unit needs to be adjusted, the CPU controls the actuator drive circuit 40 to drive the actuator 36 and adjusts the position of the synchronization detection sensor 20. Also in this embodiment, the CP of the control circuit 41
U monitors the deviation of the scanning position of the beam spot based on the time difference between the detection signals from the first and second light receiving units 21 and 22. When the scanning position shift (detection signal time difference) reaches a predetermined amount, for example, the scanning position shifts to the position indicated by the arrow b or c in FIG.
Or, when it reaches tc, the actuator 35 is driven to adjust the position of the synchronization detection sensor 20 as described above,
The incident position of the beam in the sub-scanning direction on each light receiving unit is adjusted. As the adjustment amount at this time, for example, a movement amount from a position indicated by an arrow b or c in FIG. 4 to a position indicated by an arrow a in FIG. 1 can be determined in advance. Here, the control circuit 41, the actuator drive circuit 40, and the actuator 36 are detection position adjusting means.

Even with such an adjustment, when the deviation of the scanning position of the beam spot reaches a certain amount, the deviation can be automatically repaired. It is possible to prevent a situation in which image formation cannot be performed due to detachment from the light receiving unit. Here, an example in which the adjustment is performed when the displacement of the scanning position of the beam spot reaches a predetermined amount has been described. However, if the scanning position is slightly displaced, the adjustment is immediately performed, and the scanning position is always set to a normal value. The position may be set. Further, the synchronization detection mirror described in the second embodiment may be adjusted, and the incident position may be adjusted by both the synchronization detection mirror and the synchronization detection sensor. Although a digital copying machine has been described as each embodiment of the present invention, the present invention can be applied to other image forming apparatuses that write an image using a laser beam, such as a laser printer, a facsimile machine, and a digital multifunction peripheral. Needless to say.

[0032]

As described above, according to the image forming apparatus of the present invention, in the writing unit of the image forming section, the first beam detecting means and the second beam arranged in the vicinity thereof in different directions are provided. By measuring the scanning time of the beam spot between the detecting means and the incident position of the beam on the synchronous detection sensor in the sub-scanning direction, the abnormality is detected when the position deviates from a predetermined range. By outputting the signal, it is possible to recognize that the apparatus is in an abnormal state before the beam does not enter the light receiving unit of the synchronization detection sensor and image formation cannot be performed.

In this case, if a predetermined message is displayed on the display unit, the user of the apparatus can be notified of the problem. Further, if the details of the abnormality are notified to a preset partner such as a service station, the trouble of the user requesting the repair can be saved. Further, if the incident position of the beam in the sub-scanning direction with respect to the first and second beam detecting means is adjusted in accordance with the incident position of the detected beam, if the incident position shifts, it is automatically repaired. However, it is possible to prevent a situation in which the beam does not enter the light receiving portion of the synchronization detection sensor and image formation cannot be performed.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an arrangement relationship between a synchronization detection sensor and a photosensitive drum of a digital copying machine according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing an example of a detection signal when a beam spot passes over the synchronization detection sensor.

FIG. 3 is a block diagram showing a configuration of the digital copying machine according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of an optical path when a deviation occurs in a scanning position of a beam spot in the synchronization detection sensor illustrated in FIG. 1;

FIG. 5 is a waveform chart showing a detection signal by a synchronization detection sensor when the optical path of the beam spot is at a position indicated by an arrow b in FIG.

FIG. 6 is a waveform chart showing a detection signal of the synchronization detection sensor at the position shown by the arrow c.

FIG. 7 is a diagram illustrating another arrangement example of the first and second light receiving units in the synchronization detection sensor used in the present invention.

FIG. 8 is a diagram showing still another arrangement example.

FIG. 9 is a diagram illustrating a configuration of a portion related to a synchronization detection sensor in a digital copying machine according to a second embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a portion related to a synchronization detection sensor in a digital copying machine according to a third embodiment of the present invention.

FIG. 11 is a schematic plan view showing an arrangement of a writing unit and a photoconductor in a conventional image forming apparatus.

FIG. 12 is a schematic side view of the same.

FIG. 13 is a schematic plan view showing an arrangement relationship between the synchronization detection sensor and the photosensitive drum.

FIG. 14 is a waveform diagram showing a relationship between a detection signal and an image signal when a beam spot passes over the synchronization detection sensor.

[Explanation of symbols]

 1: LD unit 3: Polygon mirror 4: Motor 5: fθ lens 7: Mirror 9: Cylindrical lens 10: Synchronous detection mirror 11, 20: Synchronous detection sensor 12: Light receiving section 21: First light receiving section 22, 22 ': 2nd light receiving part 30, 36: Actuator 30a, 36a: Projection part 31, 35: Optical housing 32, 33: Leaf spring 34, 40: Actuator drive circuit 37, 38: Compression spring 39: Substrate 41: Control circuit 42: Image reading unit 43: Image forming unit 44: Operation display unit 45: CPU 46: ROM 47: RAM 48: Network I / F 49: SS terminal

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 2C362 BA82 BB25 BB29 BB38 2H045 CA88 DA02 DA41 5C051 AA02 CA07 DB02 DB07 DB30 DC02 DC03 DC07 DE33 FA01 5C072 AA03 BA13 HA02 HA13 HB08 XA01 XA05

Claims (6)

[Claims] 1. A beam generating means for generating a laser beam modulated on the basis of an image signal, a deflecting means for deflecting the laser beam emitted by the beam generating means to scan a photosensitive member, and deflecting the deflecting means. First beam detecting means for detecting the laser beam at a predetermined position.
An image forming apparatus that determines an image forming start position in response to a detection signal from the beam detecting means, wherein a second beam arranged in a direction different from the first beam detecting means in the vicinity of the first beam detecting means Detecting means; time measuring means for measuring a time from when the first beam detecting means detects the laser beam to when the second beam detecting means detects the laser beam; An abnormal signal output unit that outputs an abnormal signal when the measured time is out of a predetermined range set in advance. 2. The image forming apparatus according to claim 1, further comprising: a display unit that displays an operation state and a message of the device; and a unit that displays a predetermined message on the display unit when the abnormal signal is output. An image forming apparatus, comprising: 3. The image forming apparatus according to claim 1, further comprising: a notifying unit that notifies a predetermined partner of the content of the abnormality when the abnormality signal is output. 4. A beam generating means for generating a laser beam modulated based on an image signal, a deflecting means for deflecting the laser beam emitted by the beam generating means to scan a photosensitive member, and deflecting the deflecting means. First beam detecting means for detecting the laser beam at a predetermined position.
An image forming apparatus that determines an image forming start position in response to a detection signal from the beam detecting means, wherein a second beam arranged in a direction different from that of the first beam detecting means in the vicinity of the first beam detecting means Detecting means; time measuring means for measuring a time from when the first beam detecting means detects the laser beam to when the second beam detecting means detects the laser beam; An image forming apparatus comprising: an incident position adjusting unit that adjusts an incident position of the laser beam in the sub-scanning direction with respect to the first beam detecting unit and the second beam detecting unit according to the measured time. apparatus. 5. The image forming apparatus according to claim 4, wherein the incident position adjusting unit is configured to adjust a position of a mirror that reflects the laser beam toward the first beam detecting unit and the second beam detecting unit. An image forming apparatus comprising: means for adjusting the incident position by adjusting a direction. 6. A beam generating means modulated based on an image signal, a deflecting means for deflecting a laser beam emitted from the beam generating means to scan on a photosensitive member, and a laser beam deflected by the deflecting means. An image forming apparatus for determining an image forming start position in accordance with a detection signal from the first beam detecting means. A second beam detector arranged in a direction different from that of the first beam detector; and the second beam detector detects the laser beam after the first beam detector detects the laser beam. Time measuring means for measuring the time until the detection, and detection for adjusting the positions of the first beam detecting means and the second beam detecting means according to the time measured by the time measuring means An image forming apparatus comprising a position adjusting unit.