JPH10202943A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the frequency of lighting with a laser beam during an entire process time excepting an image writing time during a synchronous detection time and thereby prevent a flare from being generated by a scattered light which tends to result in the deterioration of an image quality. SOLUTION: This electrophotographic device is of the multibeam type that at least, two or more adjacent laser beams are used to write adjacent lines simultaneously. In addition, the device is of such a construction that when an exposure means configured to control a position for starting the writing of data with the help of an identical synchronous detection part is provided, a first laser beam (LD1) is initially lighted under control for synchronous detection, then the first laser beam (LD1) is turned OFF at the time of detecting the synchronous signal (A) and at the same time, a second laser beam (LD2) is lighted, and a second synchronous signal (B) is detected and at the same time, the second laser beam (LD2) is turned OFF as a sequential process. Thus it is possible to minimize a time for lighting the laser beam during the synchronous detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
Related to electrophotographic devices such as laser printers and facsimile machines, in particular, having multi-beam type exposure means for simultaneously writing adjacent lines with two or more laser beams, and being characterized by synchronous control of the plurality of laser beams And an electrophotographic apparatus having the same.

[0002]

2. Description of the Related Art Conventionally, electrophotographic apparatuses such as digital copying machines, laser printers, and facsimile machines are well known. In these electrophotographic apparatuses, a photosensitive member is charged by a charging means (a charging charger, a charging roller, etc.). After that, an electrostatic latent image is formed by an exposure unit that performs optical writing according to recorded information using a laser beam, and the electrostatic latent image is visualized with toner of a developing unit, and is visualized on a photoconductor. The supplied toner image is fed to a paper feed tray or paper feed device (paper feed roller, transport roller,
A transfer unit (transfer charger, transfer belt, transfer roller, etc.) transfers the paper to a sheet supplied to a transfer unit (opposite portion of the photoreceptor and the transfer unit) by a sheet supply unit including a resist roller. The sheet is conveyed to a fixing unit, and a toner image is fixed on the sheet by a fixing unit (a heat fixing roller or the like) to obtain a desired image.

In an electrophotographic apparatus having an exposure means for performing optical writing with a laser beam as described above, the passage of a laser beam scanned in the main scanning direction by an optical deflector such as a polygon mirror is synchronously detected by a photodetector. The write start position on the photosensitive member is controlled by an output signal (synchronization signal) from the synchronization detection unit. That is, the control unit of the laser light source controls the write start timing based on the output signal from the synchronization detection unit as a time reference, modulates the output of the laser light source from the write start position in accordance with the recording information, and places it on the photoconductor. An electrostatic latent image is formed.

In such an electrophotographic apparatus,
A multi-beam optical writing device that simultaneously writes adjacent lines with two or more laser beams on the exposure means in order to increase the recording speed and increase the recording density In a multi-beam type optical writing device, for example, a common scanning optical system including an fθ lens and the like is configured to deflect laser beams from two or more laser light sources with an optical deflector such as a polygon mirror. Then, the light is condensed on the photoconductor through a plurality of light spots, and is simultaneously scanned in the main scanning direction on the recording medium as a plurality of light spots separated in the sub-scanning direction, thereby writing recording information on the photoconductor.

[0005]

In the case of a multi-beam system in which two or more laser beams simultaneously write adjacent lines in the sub-scanning direction, the distance in the sub-scanning direction between simultaneously scanned adjacent spots. That is, the pitch of the scanning lines by a plurality of light spots changes depending on the recording density (resolution), and in the case of high-density recording, the scanning line pitch becomes minute. In order to set such a minute scanning line pitch, a plurality of laser light sources must be arranged in the main scanning direction while being shifted in the sub-scanning direction by an amount corresponding to the resolution (scanning line pitch). Have been done. In other words, the scanning line pitch is adjusted by arranging the laser light source rows arranged close to each other in the main scanning direction at an inclination in the sub-scanning direction and adjusting the inclination. For this reason, the positions of the plurality of light spots on the photoconductor are shifted by a certain distance in the main scanning direction, and a time difference occurs when the light spot passes through the synchronization detection unit.

In the conventional synchronous detection method, even in the case of two or more multi-beam methods, the synchronous detection is performed by one synchronous detection section. For example, when two laser light sources are provided, the synchronous detection at the time of the previous scanning is performed. Two laser light sources are turned on at the same time from the detection, and all laser light sources are turned off at the same time when the second light spot passes through the synchronization detection unit and the synchronization signal detection processing is completed. .

However, in such a system, in the multi-beam system having two or more n laser light sources, all the laser light sources are turned on before the first light spot reaches the synchronous detection unit, and the last light spot is turned on. Since all the laser light sources are turned off after the n-th light spot has passed through the synchronization detection unit, the lighting time of the laser light source at the time of synchronization detection becomes longer, and the risk of scattered light increases accordingly. When flare occurs due to scattered light at the time of synchronization detection and reaches the photoconductor, the electrostatic latent image may be disturbed and image quality may be degraded.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and minimizes the lighting of a laser beam other than when writing an image, such as during synchronization detection, to prevent the occurrence of flare due to scattered light that leads to a reduction in image quality. It is an object of the present invention to provide an electrophotographic apparatus capable of performing such operations. It is another object of the present invention to facilitate control for the above.

[0009]

To achieve the above object, the present invention is directed to a charging device and an exposure device for forming an electrostatic latent image on a photoreceptor, and an electrostatic device formed on the photoreceptor. Developing means for visualizing the latent image, paper supply means and transfer means for transferring the visualized image to paper, fixing means for fixing the image transferred to the paper, etc. In the electrophotographic apparatus, the exposing means has a multi-beam system in which at least two or more adjacent laser beams are written and adjacent lines are simultaneously written by the two or more laser beams, and the same synchronization is performed. The write start position is controlled by a detection unit, and control for synchronization detection is performed by first turning on the first laser beam, turning off the first laser beam when the synchronization signal is detected, and switching off the second laser beam. Turns on the beam, and configuration and to be performed in sequential processing as that with the detection of the second synchronization signal turns off the second laser beam.

Further, in the invention of claim 2, in addition to the configuration of claim 1, the second laser beam is turned on one time earlier by using a synchronization signal output of the first laser beam as a time reference. The configuration is such that the synchronization signal output of the preceding laser beam is used as a time reference.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a view showing a main part of an electrophotographic apparatus according to the present invention, which is an electrophotographic apparatus used for a digital copying machine, a laser printer, or the like, and forms an electrostatic latent image on a photosensitive member. (Charging charger, charging roller, etc.) and exposure means (optical writing device using a laser beam, etc.), and developing means (one-component development) for visualizing an electrostatic latent image formed on the photoreceptor. And a paper supply means for transferring a visualized image (toner image) to paper (a paper tray or paper supply device for storing paper, such as a paper supply roller). Transfer roller (registration roller, transfer roller, etc.)) and transfer means (transfer charger, transfer belt, transfer roller, etc.), fixing means (heat fixing roller, etc.) for fixing the image transferred to the paper, and photosensitivity after transfer Residual toner on body Cleaning means (cleaning brush, a cleaning blade or the like) for removing it is provided with the like, the illustration of the non-multi-beam optical writing device is an exposure means are omitted.

The multi-beam optical writing device has a first and a second arrangement arranged in a substantially horizontal direction (corresponding to the main scanning direction) with a slight difference corresponding to the resolution in the height direction (corresponding to the sub-scanning direction). And two laser light sources LD1 and LD2. The laser beams from the two semiconductor laser light sources LD1 and LD2 are reflected by a deflecting and reflecting surface of a polygon mirror 3 rotated by a motor (not shown) and swung in the horizontal direction. Then, an imaging lens system 4 including an fθ lens and the like
Through the mirror, the optical path is bent downward by the mirror 5 and condensed on the photosensitive drum 6 as two small light spots. 2) simultaneously to form an electrostatic latent image.

The first and second semiconductor laser light sources LD
Between the LD 1 and the polygon mirror 3, lenses such as a collimator lens and a cylindrical lens, an aperture for adjusting an aperture diameter, a mirror and a prism for beam combining are arranged as necessary. The illustration is omitted.

On the other hand, a part of the laser beam from the polygon mirror 3 also reaches a synchronous detector 7 composed of a photodetector such as a photodiode, and controls the first and second semiconductor laser light sources LD1 and LD2. The LD control unit 8 controls the write start timing based on the output signal (synchronous signal) from the synchronization detection unit 7 as a time reference, and controls the first and second semiconductor laser light sources LD1 and LD2 from the write start position to record information. And an electrostatic latent image is formed on the photosensitive drum 6.

The operation of this part will be described in more detail. The LD control unit 8 determines the timing at which the next laser beam passes through the synchronization detection unit 7 from the synchronization detection during the previous scan (depending on the scanning speed of the polygon mirror, etc.). The first and second semiconductor laser light sources LD in consideration of a preset time).
1. Light LD2. Then, when the first and second laser beams pass through the synchronization detection unit 7, a synchronization signal is output. When the synchronization signal detection processing is completed, the laser beam is turned off once. After the light is turned off, a predetermined time elapses, and the laser beam is turned on / off in accordance with the recording information at the same timing as the laser beam reaches the image forming area on the photosensitive drum 6, and exits the image forming area. Then, the operation of turning off the light again until the next synchronization signal detection processing is performed.

The two semiconductor laser light sources LD1 and LD2 are shifted in the sub-scanning direction by an amount corresponding to the resolution (scanning line pitch) in order to set the scanning line pitch P in the sub-scanning direction. They are arranged side by side in the main scanning direction. For this reason, as shown in FIG. 2, the positions of the light spots S1 and S2 by the two laser beams that scan the photoconductor and the synchronization detection unit are shifted by a distance L in the main scanning direction. When passing through the surface 7a, a time difference corresponding to this distance L occurs.

Here, FIG. 3 shows a conventional synchronous signal detection 2
FIG. 4 is a diagram showing an example of turning-on / off timings of two semiconductor laser light sources LD1 and LD2. In a case where two semiconductor laser light sources LD1 and LD2 are provided, the two semiconductor laser light sources are the time from the synchronization detection at the previous scanning. LD
In this method, the semiconductor laser light sources LD1 and LD2 are simultaneously turned off (OFF) when the second light spot passes through the synchronization detection unit 7 and the synchronization signal detection processing is completed. . Also in this method, the light spot S by the two semiconductor laser light sources LD1 and LD2 is used.
Since the positions of S1 and S2 are shifted by L in the main scanning direction,
Synchronization signal outputs (A) and (B) corresponding to the respective light spots S1 and S2 are obtained.

However, in this method, especially in the case of two or more multi-beam systems, the lighting time of the semiconductor laser light source is lengthened, and the danger of scattered light is increased accordingly, and flare due to scattered light at the time of synchronization detection is generated. However, when it reaches the photoreceptor, the electrostatic latent image is disturbed, leading to deterioration in image quality.

Therefore, in the present invention, as a countermeasure against these problems, in the case of a multi-beam, a synchronization signal detection process is sequentially performed for each beam to suppress scattered light to some extent. 2 when the synchronization signal is detected according to the present invention
FIG. 4 shows an example of the turning-on / off timing of the two semiconductor laser light sources LD1 and LD2.

As shown in FIG. 4, the lighting timing of the first semiconductor laser light source LD1 is the same as in the prior art in the time from the synchronization detection at the previous scanning (O
N), but the second semiconductor laser light source LD2 is turned off (OF) until the synchronization signal detection processing by the laser beam from the first semiconductor laser light source LD1 is completed.
F) In advance, the first semiconductor laser light source LD1 is turned off (OF) with reference to the processing timing of the first semiconductor laser light source LD1 (the time point at which the first synchronization signal (A) is detected).
F), the second semiconductor laser light source LD2 is turned on (ON), a synchronization signal detection process is performed with the second laser beam, and the second laser beam is turned off together with the detection of the second synchronization signal (B) ( OFF).

As described above, each of the semiconductor laser light sources LD1, LD1,
By controlling the light emission and extinguishing of the LD 2 sequentially by shifting the timing, the lighting time of the two semiconductor laser light sources LD 1 and LD 2 at the time of synchronization detection can be minimized, and the generation of scattered light is minimized. Can be suppressed.

In the example of FIG. 4, the lighting timing of the second semiconductor laser light source LD2 is determined by the first semiconductor laser light source L2.
Although the detection timing of the first synchronization signal (A) by the laser beam D1 is delayed by Δt, as shown in FIG. 2, this is because the light spots S1 and S2 of the two laser beams on the scanning surface are scanned. Since the position is shifted by the distance L in the main scanning direction, the second semiconductor laser light source L is taken into consideration in consideration of the time difference when passing through the light receiving surface 7a of the synchronization detection unit 7.
This is to minimize the lighting time of D2. That is, the light spots S1 and S by two laser beams
Since the distance L of the second laser beam is short and the management of the time is easy and there is no problem even if the second semiconductor laser light source LD2 is turned off immediately before the detection, the second distance L (or the time difference) between the two laser beams is calculated in advance. If the delay time Δt of the lighting timing of the semiconductor laser light source LD2 is determined and set, the lighting time of the second semiconductor laser light source LD2 can be managed to a minimum.

FIG. 5 is a block diagram showing an embodiment of the synchronization signal detection processing section in the LD control section 8. As shown in FIG. In FIG. 5, the first output signal (first synchronization signal (A)) from the synchronization detection unit 7 is input to the synchronization circuit 1 via the synchronization separation circuit, and the synchronization circuit 1 performs phase matching with the write clock signal. The output is counted by the control counter 1 and
The result is sent to the LD1 drive control circuit in the LD control unit and other places, and is used for turning off the first semiconductor laser light source LD1 immediately after the synchronization detection, drive control at the start of recording information writing, and the like. .

Further, the lighting control of the second semiconductor laser light source LD2 also utilizes the counting result of the control counter 1, and preset data and the counting result of the control counter 1 are compared by a comparing circuit. 2 semiconductor laser light source L
The lighting timing of D2 (for example, the delay time Δt from the detection of the first synchronization signal (A) to the lighting shown in FIG. 4) is determined, the second LD control signal is output to the LD2 drive control circuit, and the second LD control signal is output. Is turned on, a switching timing signal is transmitted to the synchronization separation circuit, and the input of the synchronization signal is switched to the synchronization circuit 2 side.
As a result, a second synchronizing signal (B) is output from the synchronizing detection unit 7, phase matching with the write clock signal is achieved by the synchronizing circuit 2, and its output is counted by the control counter 2 and the output is counted. The result is sent to the LD2 drive control circuit in the LD control section and other places, and is used for turning off the second semiconductor laser light source LD1 immediately after the synchronization detection, controlling the drive at the start of recording information writing, and the like. After the detection processing of the second synchronization signal (B), the switching timing signal is transmitted to the synchronization separation circuit, and the input of the synchronization signal is switched to the synchronization circuit 1 side.

With the above control, the turning on and off of the two semiconductor laser light sources LD1 and LD2 at the time of synchronization detection can be performed at the timing shown in FIG. 4, and the lighting time can be minimized.

[0027]

As described above, the electrophotographic apparatus according to the first aspect has at least two or more adjacent laser beams, and simultaneously writes adjacent lines with the two or more laser beams. Even in the case of using a beam system and using an exposure unit configured to control the write start position by the same synchronization detection unit, the control for synchronization detection first turns on the first laser beam and detects the synchronization signal. At this point, the first laser beam is turned off, the second laser beam is turned on, and the second laser beam is turned off simultaneously with the detection of the second synchronization signal. Laser beam lighting time can be minimized, and the generation of scattered light can be minimized, so that high quality images can be obtained. Kill.

In the electrophotographic apparatus according to the second aspect, in addition to the configuration according to the first aspect, the lighting of the second laser beam is performed one time before the synchronization signal output of the first laser beam is used as a time reference. With the configuration in which the synchronization signal output of the preceding laser beam is used as a time reference, time can be easily managed, accurate processing can be performed, and control can be facilitated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main configuration of an electrophotographic apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a scanning position of a light spot by two laser beams.

FIG. 3 is a diagram showing an example of a conventional on / off timing of two semiconductor laser light sources (LD1, LD2) when a synchronization signal is detected.

FIG. 4 is a view showing one embodiment of the present invention, in which two semiconductor laser light sources (LD1, LD2) at the time of detecting a synchronization signal;
FIG. 3 is a diagram showing an example of lighting / light-off timings of FIG.

FIG. 5 is a diagram illustrating an embodiment of the present invention, and is a block diagram illustrating an example of a synchronization signal detection processing unit in an LD control unit.

[Explanation of symbols]

 3: Polygon mirror (optical deflector) 4: Imaging lens system 5: Mirror 6: Photoconductor drum 7: Synchronization detection unit 8: LD control unit A: First synchronization signal B: Second synchronization signal LD1: First 1st semiconductor laser light source LD2: 2nd semiconductor laser light source

Claims (2)

[Claims] An electrostatic latent image formed on a photoconductor; a developing device for visualizing the electrostatic latent image formed on the photoconductor; and a developing device for visualizing the electrostatic latent image formed on the photoconductor. An electrophotographic apparatus including a sheet supply unit and a transfer unit for transferring the image transferred to the sheet, and a fixing unit for fixing the image transferred to the sheet, wherein the exposing unit includes at least two or more adjacent units. It has a laser beam, is a multi-beam system in which writing of adjacent lines is performed simultaneously by the two or more laser beams, and has a configuration in which a writing start position is controlled by the same synchronization detection unit. First, when the first laser beam is turned on and the synchronization signal is detected, the first laser beam is turned off and the second laser beam is turned on, and the second laser beam is turned on together with the detection of the second synchronization signal. An electrophotographic apparatus characterized by sequentially performing processes such as turning off a lamp. 2. The method according to claim 1, wherein the second laser beam is lit based on the synchronization signal output of the immediately preceding laser beam, such that the synchronization signal output of the first laser beam is time-based. The electrophotographic apparatus according to claim 1, wherein