JPH09254438A - Photoscan device for electrophotographic printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a photosensitive drum on the part to which a laser beam is emitted from becoming degraded when the laser beam to be detected by a light detector is emitted to the surface of the photosensitive drum at the time of starting of a motor for rotating a rotary polyhedral mirror. SOLUTION: This photoscan device for an electrophotographic printer consists of a laser 1 for emitting a laser beam, a rotary polyhedral mirror 2 for reflecting the laser beam, a motor 3 for rotating the rotary polyhedral mirror 2, an fθ lens for projecting the laser beam reflected by the polyhedral mirror 2 to a photosensitive drum, and a light detector 6 for detecting the laser beam reflected by the rotary polyhedral mirror 2. In this case, a periodic detection part 11 for detecting the period of the laser beam detected by the photodetector 6, memory 12 to which the detected period is stored, and a main CPU 13 for reading an optimal period at which the laser beam is emitted into the light detector 6 from period data stored in memory 12 and causing the laser 1 to emit a light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device for an electrophotographic printer, and more particularly to an optical scanning device for an electrophotographic printer that prevents early deterioration of a photosensitive drum.

[0002]

2. Description of the Related Art FIG.
FIG. 37 is a perspective view showing an example of an optical scanning device of a conventional electrophotographic printer shown in Japanese Patent No. 371. Referring to FIG. 3, in the optical scanning device of the conventional electrophotographic printer, the laser light emitted from the laser 1 is collimated by a collimator lens (not shown) and is deflected by a rotating polygon mirror 2 rotated by a motor 3. This deflected laser light is imaged on the charged surface of the photosensitive drum 5 by the fθ lens 4. This image spot is repeatedly moved in the arrow X direction on the rotating photosensitive drum 5 by the rotation of the rotary polygon mirror 2.

The photodetector 6 is installed outside the information writing area,
The laser beam deflected by the rotary polygon mirror 2 is detected to generate a synchronization signal. Based on this synchronizing signal, the laser 1 emits a print information signal.

[0004]

In the conventional optical scanning device of the electrophotographic printer, the photodetector 6 can detect the laser light in the next cycle from the time when the photodetector 6 detects the laser light. As a result, the laser light is continuously emitted after a certain period of time. However, the detection cycle of the laser light detected by the photodetector 6 is from the time when the motor 3 for rotating the rotary polygon mirror 2 starts to rotate until the rotational speed is stabilized to be constant.
Since the motor 3 becomes longer than when it is rotating stably, the laser 1 emits light regardless of the position where the laser light is irradiated onto the photosensitive drum 5 through the fθ lens 4, and As a result, the photosensitive drum 5 is irradiated with the laser light, and the portion of the photosensitive drum 5 irradiated with the laser light is deteriorated.

An object of the present invention is to irradiate a laser beam detected by a photodetector onto a photoconductor drum when a motor for rotating a rotary polygon mirror is started, and the photoconductor drum in a portion irradiated with the laser beam is deteriorated. An object of the present invention is to provide an optical scanning device for an electrophotographic printer that prevents the above.

[0006]

An optical scanning device for an electrophotographic printer according to the present invention includes a laser that emits laser light through a collimator lens, a rotary polygon mirror that reflects the laser light, and a rotary polygon mirror that rotates. And a motor for irradiating the photosensitive drum with the laser light reflected by the rotating polygon mirror.
In an optical scanning device of an electrophotographic printer including a θ lens and a photodetector that detects the laser light reflected by the rotary polygon mirror, a cycle detection unit that detects the cycle of the laser light detected by the photodetector. A memory for storing the detected cycle, and a control unit for causing the laser to emit light by reading an optimum cycle of the laser light incident on the photodetector from the cycle stored in the memory.

Further, the optical scanning device of the electrophotographic printer of the present invention stores a cycle detecting section for detecting the cycle of the laser beam detected by the photodetector at the time of starting the motor, and the detected cycle. A memory and a control unit for causing the laser to emit light by reading an optimum cycle of the laser light incident on the photodetector when the motor is restarted from the cycle stored in the memory.

[0008]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 3 is a perspective view showing an embodiment of the present invention.
In the optical scanning device of the electrophotographic printer according to this embodiment, the laser light emitted from the laser 1 is collimated by a collimator lens (not shown) and is deflected by a rotating polygon mirror 2 rotated by a motor 3. This deflected laser light is imaged on the charged surface of the photosensitive drum 5 by the fθ lens 4. This image spot is repeatedly moved in the arrow X direction on the rotating photosensitive drum 5 by the rotation of the rotary polygon mirror 2. The photodetector 6 is installed outside the information writing area and detects the laser beam deflected by the rotary polygon mirror 2 to generate a synchronization signal. Based on this synchronizing signal, the laser 1 emits a print information signal.

FIG. 1 is a block diagram showing the configuration of this embodiment. Referring to FIG. 1 in conjunction with FIG.
Emits light under the control of the laser controller 7. Rotating polygon mirror 2
The motor 3 for rotating the motor is controlled by the motor controller 9. When the photodetector 6 detects the laser light emitted from the laser 1, it requests the image writing control unit 10 to output image data on this scanning line. Image writing control unit 10
Causes the laser control unit 7 to emit laser light corresponding to image data. When the photodetector 6 detects the laser light emitted from the laser 1, the cycle is detected by the cycle detector 11. The cycle detected by the cycle detector 11 is stored in the memory 12. The main CPU 13 refers to the cycle stored in the memory 12.

When the optical scanning device of the electrophotographic printer is forming an image on the photosensitive drum 5, the photodetector 6 does not detect laser light. Therefore, in order to detect the laser light in the next cycle, it is necessary to emit the laser light from a position where the laser light emitted from the laser 1 deviates from the image forming surface of the photosensitive drum 5. The photodetector 6 serves as a reference for its position. That is, when the photodetector 6 detects laser light, the image writing control unit 10 performs laser control for image formation. The main CPU 13 stops the emission control of the laser 1 for the photodetector 6 to detect the laser light. Further, the laser light for the laser light detection of the photodetector 6 in the next cycle is emitted.

However, the optical scanning device of the electrophotographic printer must start the motor 3 for rotating the rotary polygonal mirror 2 when starting from the stopped state. However, from the time when the motor 3 that rotates the rotary polygon mirror 2 starts to rotate until the rotation speed stabilizes at a constant level, the photodetector 6
Since the detection cycle of the laser light detected by is longer than that when the motor 3 is stably rotating, the laser light may irradiate the photosensitive drum 5 through the fθ lens 4 regardless of the position. Instead, the laser 1 emits light, and as a result, the photosensitive drum 5 is irradiated with the laser light, and the photosensitive drum 5 in the portion irradiated with the laser light deteriorates.

In the optical scanning device of the electrophotographic printer of the present invention, the cycle detector 11 detects the cycle of the laser light detected by the photodetector 6 and stores the data of this cycle in the memory 12. When the optical scanning device is activated next time, the main CPU 13 refers to the cycle stored in the memory 12 at the previous activation, retrieves the approximated data, and based on this, detects the light in the next cycle. The laser control unit 7 is instructed that the device 6 emits the laser light 1 for detecting the light. For example,
When the rotation of the motor 3 is accelerated, the detection cycle of the laser light of the photodetector 6 detected at a certain timing is already short in the next cycle. If there is data stored in the memory 12, it is possible to find data that is close to the cycle just detected and predict that the next data will be close to the next cycle. Therefore, the light emission of the laser 1 in the next cycle can be performed outside the image forming surface of the photosensitive drum 5.

FIG. 2 is a signal diagram of this embodiment. The operation of this embodiment will be further described with reference to FIG. 3 together with FIG. 1 and FIG.

In FIG. 3 (A), the period detector 11 detects the period of the laser beam detected by the photodetector 6 (..., t _n-1 ,
t _n , t _{n + 1} , t _{n + 2} , ...), and this data is stored in the memory 12 (address is ..., P _n-1 , p _n , p _{n + 1} , p).
_It is stored in _{n + 2} , ...). At this time, in order for the laser light emitted from the laser 1 to be emitted at a position outside the image forming surface of the photoconductor drum 5, x _n for the cycle t _n and x _{n + 1} for the cycle t _{n + 1.} ,, and the ratio is t _n : x _n =
t _{n + 1} : x _{n + 1} = ... = t: x = constant.

In FIG. 3B, the emission timing of the laser 1 is determined based on the data stored in the memory 12 in FIG. That is, in a to b of the photodetector 6 outputs, 'when detecting a _n, emission of the laser 1 for detecting c of the sensor 6 outputs, first, the period t' period t the value of the approximation is _n, It is detected from the memory 12. The detected value is t _n
, The period from b to c of the photodetector 6 output is t
It is expected to be close to _{n + 1} . Therefore, the period t _{n + 1}
Based on, in accordance with _{(t n + 1 × x /} t) of the formula, by realizing the emission timing of the laser 1 for the detection of c of the photodetector 6 outputs the detected period t _'n of the next It is possible to prevent the image forming surface of the photosensitive drum 5 from being irradiated with light in a cycle.

[0017]

As described above, according to the present invention,
The period of the laser light reflected from the rotating polygon mirror can be detected and stored in memory, so based on that data,
Even if the rotation speed of the motor for rotating the rotary polygon mirror is not stable, the laser light emitted from the laser can be controlled so as not to be emitted on the photosensitive drum, and the deterioration of the photosensitive drum can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a signal diagram of this embodiment.

FIG. 3 is a perspective view illustrating this embodiment and a conventional example.

[Explanation of symbols]

 1 laser 2 rotating polygon mirror 3 motor 4 fθ lens 5 photoconductor drum 6 photodetector 7 laser control unit 9 motor control unit 10 image writing control unit 11 cycle detection unit 12 memory 13 main CPU

Claims (2)

[Claims] 1. A laser that emits a laser beam through a collimator lens, and a rotating polygon mirror that reflects the laser beam,
An electronic device including a motor for rotating the rotary polygon mirror, an fθ lens for irradiating the photosensitive drum with the laser light reflected by the rotary polygon mirror, and a photodetector for detecting the laser light reflected by the rotary polygon mirror. In an optical scanning device of a photographic printer, a cycle detector for detecting a cycle of the laser light detected by the photodetector, a memory for storing the detected cycle, and an optimum laser light incident on the photodetector. The optical scanning device of the electrophotographic printer, comprising: 2. A cycle detector that detects a cycle of the laser light detected by the photodetector when the motor is started, a memory that stores the detected cycle, and the photodetector when the motor is restarted. 2. An optical scanning device for an electrophotographic printer according to claim 1, further comprising: a control unit that reads out an optimum cycle of incidence of laser light from the cycle stored in the memory and causes the laser to emit light.