JPS60170371A - Synchronizing signal generator - Google Patents

Abstract

PURPOSE:To reduce malfunction due to noise remarkably in a photorecording device by providing a gate circuit and controlling signals sent from a synchronism detector to a phase synchronizing circuit through an electric wire. CONSTITUTION:A gate circuit 12 is provided in a laser printer to control signals sent from the synchronism detector 9 to the phase synchronizing circuit 2 through an electric wire 11. The circuit 12 is opened by a modulation signal for synchronism detection from a modulation signal for synchronism detection generating section in the circuit 2 during synchronism detecting period and passes synchronizing signals from the detector 9 to the circuit 2. However, during the time other than synchronism detecting period and modulation signal for synchronism detection is not inputted, the circuit is closed and invalidates signals from the detector 9. The circuit 12 is provided at nearly the same place with the circuit 2, and the detector 9 and the circuit 12 are connected by a long electric wire 11. Noise entered from the electric wire 11 is cut off during the time other than synchronism detecting period, and malfunction caused by noise of the circuit 2 is reduced sharply.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a synchronization signal generating device in an optical recording device such as a laser printer that records information using a light beam.

(Prior Art) Optical recording devices for recording light beam information include laser printers and the like, and FIG. 1 shows an example of a laser printer using a semiconductor laser. In this example, a semiconductor laser drive circuit 1 drives a semiconductor laser 3 using a modulation signal from a phase synchronization circuit 2, and a laser beam modulated by the modulation signal is emitted from the semiconductor laser 3. This laser beam passes through a coupling lens 4, is reflected by a mirror 5, is deflected by an optical scanning device 6 consisting of a hologram disk, is reflected by a mirror 7, and is irradiated onto a rotating photoreceptor 8 after being charged. As the hologram disk 6 is rotationally driven by a motor, the laser beam moves repeatedly on the same line, but the synchronization detector 9 detects the laser beam from the mirror 7 near the photoreceptor 8 when it starts moving along the line. Detects and generates a synchronization signal. The phase synchronization circuit 2 outputs the information signal and the modulation signal for synchronization detection as a modulation signal to the semiconductor laser drive circuit 1. In this case, the modulation signal for synchronization detection with a predetermined period generated in the modulation signal generation section for synchronization detection is output as a modulation signal. Each time the synchronization signal is input from the synchronization detector 9, the character generator 10 generates an information signal for one line and outputs it to the semiconductor laser drive circuit 1. Information signals are sequentially recorded on the photoreceptor 8 line by line.

However, in this laser printer, it is necessary to place the synchronization detector 9 near the photoreceptor 8.Since the synchronization signal is sent from the synchronization detector 9 to the phase synchronization circuit 2 via a long electric wire, Noise enters from the electric wire 11, and the phase synchronization circuit 2 misidentifies the noise as synchronous, resulting in malfunction.

In addition to the above-mentioned laser printers, optical recording devices include laser printers that modulate a constant-intensity laser beam from a laser using an optical modulator such as an acousto-optic device according to the modulation signal and enter the optical scanning device. These optical recording devices also malfunction due to noise because the synchronization signal is sent from the synchronization detector via a long electric wire.

(Objective) An object of the present invention is to provide a synchronization signal generating device that can improve the above-mentioned drawbacks and significantly reduce malfunctions due to noise in an optical recording device.

(Structure) FIG. 2 shows an example of the present invention, and FIG. 3 is a timing chart thereof.

This embodiment has a gate circuit 1 in the laser printer.
2 is provided to control the signal sent from the synchronization detector 9 to the phase synchronization circuit 2 via the electric wire 11. During the synchronization detection period, this gate circuit 12 is opened by the synchronization detection modulation signal from the synchronization detection modulation signal generator in the phase synchronization circuit 2 and allows the synchronization signal from the synchronization detector 9 to pass through the phase synchronization circuit 2. , when the synchronization detection modulation signal is not inputted outside the synchronization detection period, it is closed and the signal from the synchronization detector 9 is invalidated. The gate circuit 12 is provided at approximately the same location as the phase synchronization circuit 2, and the circuit 12 is connected to the synchronization detector 9 and the gate 1 by a long electric wire 11. This electric wire 1
Noise entering from 1 is sent to gate circuit 12 except during the synchronization detection period.
As a result, malfunctions due to noise in the phase synchronized circuit 2 are significantly reduced.

Note that the present invention is not limited to the above-mentioned embodiments, and can be similarly applied to optical recording devices other than laser printers using the above-described semiconductor laser.

(Effects) As described above, according to the present invention, the signal sent from the synchronization detector via the electric wire in the optical recording device is made valid only during the synchronization detection period, so that the noise input from the electric wire can be reduced. Malfunctions can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an example of a conventional laser printer, FIG. 2 is a system diagram showing an example of a laser printer to which the present invention is applied, and FIG. 3 is a timing chart of the same embodiment. 9...Synchronization detector, 11...Electric wire, 12...Cate circuit.

Claims (1)

[Claims] In an optical recording device that modulates a light beam with a modulation signal from a modulation signal generating means, deflects it with an optical scanning device, and scans a photoreceptor with the light beam to record information, the light beam from the optical scanning device is A synchronization detector that detects at a predetermined position and generates a synchronization signal, and means for validating the signal sent from the synchronization detector via an electric wire only during the synchronization detection period and applying it to the modulation signal generation means. Equipped with a synchronous signal generator.