JPH03206477A - Horizontal synchronous detecting device - Google Patents

Abstract

PURPOSE:To detect horizontal synchronism and whether or not there is a photosensitive body by one sensor and to save the space and cost for mounting by detecting part of laser light with which the photosensitive body is scanned as a horizontal synchronizing signal and detecting whether or not there is the photosensitive body from the reflection state of the laser light. CONSTITUTION:A part of the laser light with which the photosensitive body 5 is scanned is detected as the horizontal synchronizing signal and a simple electronic circuit is added to detect whether or not there is the photosensitive body 5 from the reflection state of the laser light. Consequently, a part of the laser light can be detected as the horizontal synchronizing signal by one photosensor 6 and whether or not the photosensitive body 5 is mounted in an equipment housing is also detected to save the storage space and cost in addition to sensors.

Description

Detailed Description of the Invention (Industrial Technical Field) The present invention is an optical scanning exposure device in which a laser beam emitted from a laser light source is deflected by a rotating polygon mirror and scanned on a photoconductor. This paper relates to a horizontal synchronization detection device for output synchronization. (Prior Art) For example, when a laser beam is scanned on a photoconductor (in a direction perpendicular to the rotational direction of the photoconductor, that is, in the main scanning direction) using an optical deflector such as a rotating polygon mirror, as in a laser printer, The laser light is turned on and off by a video modulation signal, and as the rotating polygon mirror rotates, the laser light moves as it is deflected, forming an electrostatic latent image on the photoreceptor that corresponds to the image signal. Ru. The movement of this laser light is asynchronous with the image signal source, that is, the laser emitting unit modulated by the image signal data. Therefore, it is necessary to detect the timing at which the image signal should be sent to the laser emitting unit to form an electrostatic latent image at the appropriate position on the photoreceptor, and the timing at which the scanning of the laser beam should start in order to achieve horizontal synchronization. be.

Figure 6 shows a schematic diagram of the configuration of an example of an optical scanning exposure apparatus for achieving the above-mentioned horizontal synchronization. As shown in the figure, a laser beam emitted from a laser light source 1 is deflected by a rotating polygon mirror 2, passes through a lens 3 and a mirror 4, and scans the scanning surface of a photoreceptor 5 (in the direction of arrow A). In this case, the optical sensor 6 is placed on the scanning line of the laser beam to detect the horizontal synchronization signal (LSYNC) of the image signal data. Incidentally, for mounting reasons, a folding mirror 7 is generally arranged near the mirror 4, and an optical sensor 6' is often arranged at an equivalent position on the scanning line of the photoreceptor 5. (
Problems to be Solved by the Invention) The optical sensor 6 (or 6') is used as a detector for achieving such horizontal synchronization, but whether the photoreceptor is installed inside the device housing (for example, a printer), Another set sensor was provided to detect whether or not the

As a result, the number of sensors increases, resulting in the problem of securing mounting space and increasing costs.

(Object of the Invention) In view of the above-mentioned circumstances, it is an object of the present invention to solve the conventional problems by detecting horizontal synchronization and detecting the presence or absence of a photoreceptor using a single sensor. (Structure and operation) In order to achieve the above object, the present invention provides an optical scanning exposure device that scans a photoconductor with a laser beam emitted from a laser light source using a rotating polygon mirror. It is characterized in that a portion of the laser beam is detected as a horizontal synchronization signal, and the presence or absence of the photoconductor is also detected from the state of reflection of the laser beam. The present invention uses a single optical sensor to detect part of the laser beam as a horizontal synchronization signal, and also detects whether or not a photoreceptor is installed in the device housing. Space and cost savings can be achieved. Examples of the present invention will be described below. (Embodiment) FIG. 1 is a perspective external view showing the arrangement of an optical sensor and a photoreceptor according to a first embodiment of the present invention. As shown in the figure, a part of the circumferential surface on one side of the photoreceptor 5 is made into a solid surface 5a as a reflective surface (
(shaded area). Next, horizontal synchronization detection and photoconductor presence/absence detection will be explained using the optical writing control circuit shown in FIG. 2 and the timing chart shown in FIG. 3. Here, 2 in Figure 2
0 is a controller (image processing device), 2l is an optical write control circuit that outputs a video modulation signal (VIDEOB) to the laser diode (LD) driver 22 based on image write signal data (WDATA) from the controller, 2
3 is a laser diode (LD) which is turned on/off by the video modulation signal. The optical sensor 6 is a photodiode (PD), and inputs a synchronization detection signal (DETPB) to the optical write control circuit 21. 24 is a polygon motor (PM) of the rotating polygon mirror 2 (see FIG. 6), 25 is an operation signal from the operation panel 26, and an LD power set error signal (LDPSER) from the optical write control circuit 21.
RB), a synchronization detection error signal (DETPERRB), and a lock signal (P) from the polygon motor (PM) 24.
This is a microcomputer (CPU) that performs optical scanning exposure control using input signals such as MLOKB. Now, the optical write control circuit 2l sends a video modulation signal (VIDEOB) to the LD 23 to achieve horizontal synchronization.
'', the LD 23 lights up. When the rotating polygon mirror rotates and the laser beam α comes to point CB) on one side of the photoconductor 5, the laser beam is reflected by the solid surface 5a of the photoconductor 5, and the light is transmitted to the optical sensor 6. This causes the synchronization detection signal (DETP
B) is input to the optical write control circuit 21. In this optical writing control circuit 21, the synchronization detection signal (DETPB
) Outputs a line synchronization signal (LSYNCB) indicating the start of main scanning after a certain period of time from the rising edge (a) of
After a certain period of time from the rising edge (b) of the line synchronization signal, a line gate signal (LGA
TEB) is output. When the line gate signal is "L", a video modulation signal (VIDEOB) is generated based on the image write signal data (WDATA) sent from the controller 20.
), and the LD23 is turned on by the LD driver 22.
/OFF to form an electrostatic latent image on the photoreceptor 5. Here, if the photoconductor 5 is not attached to the device housing, the laser beam will not be reflected from the solid surface 5a and will not enter the optical sensor 6, so the synchronization detection signal (DETPB) will not become "L". ．． At this time, the optical write control circuit 21 counts the time T2 from when the video modulation signal (V I DEOB) is set to "L" and the LD 23 is turned on until the synchronization detection signal (DETPB) is input from the optical sensor 6. If a synchronization detection signal is not input after a certain period of time (time T required for one scan, longer time), a synchronization detection error signal (DETPERRB="L") is output to the CPU 25. As mentioned above, the synchronization detection signal (DETPB) is detected by the optical sensor 6.
Possible causes of less output include the case where the photoreceptor 5 is not attached to the device housing as described above, and the case where the LD 23
There are three cases: does not light up, and rotating polygon mirror 2 does not rotate.

The optical writing control circuit 21 includes a light amount stabilizing circuit (not shown in the drawing) so that the LD 23 always has a constant light amount.
The power of the LD 23 is set so that the amount of light is constant at regular intervals, for example, every 1 prints. If the LD 23 has deteriorated, the power set will not operate normally, and an LD power set error signal (LPPSERRB="L") is output to the CPU 25.

Further, a polygon motor (PM) 21 of the rotating polygon mirror outputs a lock signal (PMLOKB, at L'' during steady rotation) of the motor to the CPU 25.

Therefore, the CPU 25 uses the synchronization detection signal (DETPB="H").
”), LD power set error signal (L P P SE
RRB="L"), lock signal (PMLOKB="'L")
”), it is determined that the photoreceptor 5 is not attached to the device housing, and the user is notified by displaying on the operation panel 26 that the photoreceptor is not installed.In this way, the first embodiment 1
The optical sensors 6 can detect horizontal synchronization and detect whether or not the photoconductor is attached to the device housing. FIG. 4 is a perspective external view showing the arrangement of an optical sensor and a photoreceptor according to a second embodiment of the present invention. As shown in the figure, an optical sensor 6 is placed on the scanning line at one end (C) of the photoreceptor 5, and a first reflecting mirror 8 is placed behind the photoreceptor 5 to direct the laser beam α to the photoreceptor 5. It is designed to block light. The second reflecting mirror 9 is placed at a position where the optical sensor 6 is irradiated with the laser beam reflected from the first reflecting mirror 8. By arranging the first and second reflecting mirrors 8, 9 and one optical sensor 6 in this way, when the photoreceptor 5 is mounted on the device housing, during one scan of the laser beam, Photoreceptor 5
Since the laser beam α is incident on the optical sensor 6 provided at the end only l times, the synchronization detection signal (DETPB) becomes DETPBI in FIG. If the photoconductor 5 is not attached to the device housing, the flood of laser light will not be blocked by the photoconductor, so it will be reflected by the first reflection mirror 8 and the second reflection mirror 9 and enter the optical sensor 6. Therefore, the laser beam is incident twice during one scan of the laser beam.

As a result, the synchronization detection signal (DETPB) becomes DETPB 1 in FIG. At this time, the optical writing control circuit 21 shown in FIG. 2 counts the interval of the synchronization detection signal (DETPB), and if it is shorter than the time T1 required for one scan (see FIG. 3), the time (DETPB) is counted. T3 or T.) of B1 is. C.P.
U25 outputs a photoconductor not set signal and displays the operation panel 26.
Displays on the top that the photoconductor is not installed to notify the user. (Effects of the Invention) As explained above, according to the present invention, an optical sensor used as a horizontal synchronization detection sensor can be provided with the function of detecting the presence or absence of a photoreceptor by adding a simple electronic circuit or a mirror. can. Therefore, in the present invention, as described above, a laser printer, a copying machine, an F.
It is extremely suitable for applications such as AX.

[Brief explanation of drawings]

FIG. 1 is a perspective external view showing the arrangement of an optical sensor and a photoreceptor according to a first embodiment of the present invention, FIG. 2 is an optical writing control circuit, and FIG. 3 is a timing chart of FIG. FIG. 4 is a perspective external view showing the arrangement of an optical sensor and a photoreceptor according to the second embodiment of the present invention, FIG. 5 is a timing chart of the synchronization detection signal of FIG. 4, and FIG. 6 is an optical scanning exposure device. This is a schematic diagram of the configuration. 2... Rotating polygon mirror, 5... Photoreceptor, 5a... Solid surface, 6... Optical sensor, 8... First reflecting mirror, 9... Second reflecting mirror, 20 ... Controller (image processing device), 21 ... Optical writing control circuit, 22 ... LD driver 23 ... Laser diode (LD), 24 ... Polygon motor (PM
), 25... microcomputer (CPU),
26...Operation panel.

Claims (1)

[Claims] In an optical scanning exposure device that scans a laser beam emitted from a laser light source onto a photoreceptor using a rotating polygon mirror, a portion of the laser beam scanning the photoreceptor is detected as a horizontal synchronization signal, and the reflection state of the laser beam is detected. A horizontal synchronization detection device characterized in that it detects the presence or absence of the photoreceptor.