JPS60169819A - Modulating signal generating device for synchronism detection - Google Patents

Abstract

PURPOSE:To improve precision, to set the time width of a modulating signal for synchronism detection short, to shorten the turn-on time of a semiconductor laser, and to reduce fatigue by generating the modulating signal for synchronism detection by a counter. CONSTITUTION:The counter 11 counts clock pulses of constant frequency from a clock pulse generator 12. The counter 11 holds its output at a low level during counting operation and goes up to a high level after entering a full-count state. The synchronism detection signal of a synchronous detector 9 is passed through an AND gate 13 with the high-level output signal of the counter 11 to reset the counter 11 to zero, which then starts counting clock pulses. The output signal of the counter 11 is sent as the modulating signal for synchronism detection to a semiconductor laser driving circuit 1 to turn on the semiconductor laser when the level is high. The signal is generated precisely by the counter 11 for a constant time, so the time width of the output signal is set short to shorten the turn-on time of the semiconductor laser 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a modulation signal generation device for synchronization detection in a laser printer.

(Prior Art) FIG. 1 shows an example of a laser printer using a semiconductor laser. In this example, a semiconductor laser drive circuit J 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.

When the hologram laser beam is rotationally driven by a motor, the laser beam moves repeatedly in the same line, but the synchronization detector 9 moves the laser beam from the mirror 7 into a line near the photoreceptor 8. It detects when the upper movement starts and generates a synchronization detection signal.

The phase synchronization circuit 2 outputs a modulation signal for synchronization detection and an information signal as modulation signals to the semiconductor drive circuit 1. In this case, a monomultivibrator is triggered by a clock pulse from a clock pulse generator and its output pulse is used for synchronization detection. At the same time, each time a synchronization detection signal is inputted from the synchronization detector 9, an information signal for one line is generated in the character generator 10, which is then outputted to the semiconductor laser drive circuit 1 as a modulation signal for the semiconductor laser drive circuit. Output to circuit 1. Therefore, information signals are sequentially recorded on the photoreceptor 8 one line at a time.

However, in this Seasabrink, is the clock pulse from the clock pulse generator mono? Multi-by-flake I・
Since the output pulse of the fixed pulse width TI is used as the synchronization detection modulation signal by triggering, the time width T1 of the synchronization detection modulation signal cannot be set short because the accuracy cannot be improved. For this reason, the semiconductor laser 3 is turned on for a long time due to the synchronization detection modulation signal, and even in standby mode in which no information is recorded, the semiconductor laser 3 is turned on by the synchronization detection modulation signal, which increases fatigue and changes over time.

(Objective) An object of the present invention is to provide a modulation signal generating device for synchronization detection that can shorten the lighting time of a semiconductor laser in a laser printer using a semiconductor laser.

(Structure) The present invention will be described below based on embodiments with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, and FIG. 3 is a timing chart thereof.

This embodiment is an example in which the device is used as a modulation signal generating device for synchronization detection in the phase synchronization circuit 2 in the laser printer, and the counter 11 divides the clock pulse of a constant frequency from the clock pulse generator 12. This counter 1
1, the output remains at a low level while counting clock pulses, and becomes a high level after the clock pulses have been counted (after the count value reaches the full count number).

The synchronization detection signal from the synchronization detector 9 passes through the AND gate 13 due to the high level output signal of the counter 11, resets the counter 11 to zero, and the counter 11 starts counting clock pulses. Therefore, as shown in FIG. 3, the counter 11 converts the output signal of the time width TI into
The full count number of the counter 11 and the frequency of the clock pulse are set so that this time T2 is slightly shorter than one line scanning time. The output signal of the counter 11 is sent to the semiconductor laser drive circuit 1 as a synchronization detection modulation signal, and when the signal is at a high level, the semiconductor laser 1 is turned on. Here, since the time T2 can be created with high accuracy by the counter 11, it is possible to shorten the lighting time of the semiconductor laser 3 by setting the time T1 short.

Although the up counter 11 was used in the above embodiment, a down counter was used instead of the up counter 11.
The set number may be preset by the output signal of.

(Effects) As described above, according to the present invention, a modulation signal for synchronization detection is generated by a counter in a laser printer using a semiconductor laser, so accuracy can be increased and the time width of the modulation signal for synchronization detection can be shortened. By setting in this manner, the lighting time of the semiconductor laser can be shortened, and fatigue of the semiconductor laser can be reduced, and its change over time can be reduced.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an example of a laser printer, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a timing chart of the same embodiment. 11...Counter, 12 Clock pulse generator.

Claims (1)

[Claims] A semiconductor laser is driven by a modulation signal for synchronization detection and an information signal, the laser beam is deflected by an optical scanning device, the photoreceptor is scanned with this laser beam, and information is recorded, and the laser beam from the optical scanning device is In a laser printer that generates a synchronization detection signal by detecting it with a synchronization detector at a predetermined position and generates the above-mentioned information signal in synchronization with this synchronization detection signal, a certain number of clocks are generated each time the synchronization detection signal is input. A modulation signal generator for synchronization detection, comprising a counter that starts counting pulses and outputs an output signal as a modulation signal for synchronization detection when not counting pulses.