JPS6076867A - Control system of laser printer - Google Patents

Abstract

PURPOSE:To obtain the result of printing with high quality by a saturation amplifying signal from a beam detector that detects laser light momentarily and determining the position at which a latent image is drawn on a sensitive body by the steep rise or fall of an output waveform. CONSTITUTION:The output of the beam detector 31 is amplified by an unsaturated amplifier 32. The output is inputted to a sample hold circuit 34 on the one side, and a diode laser driving circuit 35 that stores a peak voltage for a fixed time is made on and off by an input signal by the resistance of an input side, and controls the forward current of the laser diode at the time of ON by the output of the circuit 34. On the other hand, the output is inputted to the saturated amplifier 33 to obtain a square wave and to reduce the variance of the position of the starting write on the drum by utilizing steep rising.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to laser output control of a laser beam printer and control of the position at which an image is drawn on a photosensitive drum.

Conventionally, the laser output is not controlled, or the output is controlled by feeding back the output of a laser output detection photodetector that is provided exclusively to the laser.In general, there is a Many lenses are inserted, and even if the laser output is constant, the output output on the photosensitive drum at the final stage often changes due to the influence of dust, etc. If the output output decreases, a large shadow will appear on the print result. give.

In addition, the output of a beam detector that instantaneously detects the scanned laser beam is sliced at a point where the voltage exceeds a certain level to determine the starting point from which an image is drawn.

This aims to control the laser output by detecting the final output reaching the photosensitive drum, and also to improve the image quality by using the same detector.

Laser printers generally have a high-speed light-receiving element called a beam detector that determines the basic time of laser scanning, but this output is amplified by one with unsaturated amplification and the other with saturated amplification, and the former uses it as a sample. The latter is used as a starting point for laser scanning.

FIG. 1 shows a general laser scanning system. The beam is emitted from the laser 1, is formed into a J-degree beam shape by a 1/lens system 23, and is reflected by a polyhedral rotating mirror 4, which is called an Fθ lens 5. Sensation through the lens) n drum 6”-to-
Make sure to focus on a straight line.

A laser beam runs from left to right in FIG. 1 on each side of the mirror, and when it hits mirror 7 at the left end, beam detector 8 receives the light momentarily. At this time, at 8, the light is applied to the jl:1ITF, and this (H- is turned on and off), the laser 9 drum-1- is set to W (S'll), and the laser is turned on and off. However, when drawing the desired image, the output of 8 is generally mountain-shaped like the second pressure, but if this rise is slow and the output of 8 fluctuates, the f position at the beginning of drawing may be inappropriate. This results in poor printing quality.So, in order to make the tt laser output even, the tt laser output If it is used for !l+tl l1III, the laser output cannot be controlled as long as analog control is performed.Therefore, on the other hand, this waveform is proportionally amplified and used for voltage feedback of the laser output] This is the present invention. Since the output is instantaneous only once for each scan, it is necessary to sample and hold the waveform in order to capture one peak of the waveform.

In FIG. 3, numeral 31 is a beam detector, and its output is in the shape of a chevron as shown in FIG.

32 is an unsaturated amplifier, which is similar to the beam detector output as shown in FIG. 2(b). This output has 34 sample and hold circuits (peak value storage circuit) on the one hand.
35 is a diode laser drive circuit that stores the peak pressure for a certain period of time. It is turned on and off by the input signal by the resistor on the input side, and the forward current of the laser diode when it is on is controlled by the output of the sample hold (
ill.

The output of 32 is input to the saturation amplifier on the one hand, and the output of
As shown in (a), the shape is close to a rectangular wave, and the sharp rise is used to reduce the variation in the initial position of the color 1 on the drum.

In FIG. 3, the saturated amplifying circuit 32 and the unsaturated amplifying circuit are arranged in series, but the outputs of the circuits 31 are directly input to the respective amplifying circuits, that is, the parallel KL is exactly the same.

Target lasers that can be controlled are lasers whose current and optical output are proportional, such as a gamma argon laser or a guiode laser.

According to the present invention, the laser output can be increased to f with one beam detector.
Since lj can be controlled and the initial drawing to the drum is also 1t-,
Good quality printing results can be obtained.

[Brief explanation of drawings]

1'7n is a schematic diagram of Laser Solink. Figure 2 (
A) is a schematic diagram showing output waveforms in an embodiment of the present invention. FIG. 31 is a 'C circuit diagram of an embodiment of the present invention. Name of license applicant Hitachi Koki Co., Ltd.

Claims (1)

[Claims] Scans the laser beam and instantaneously detects the laser beam,
Starting from that time, the printer determines the point at which a latent image is drawn on the photoreceptor.The printer uses unsaturated amplification to maintain the peak value of the signal from the beam detector that instantaneously detects the laser beam. Control to control the laser output by storing time, and on the other hand to perform saturation amplification and determine the time at which the latent image is to be drawn on the photoreceptor based on the sharp rise or fall of the output waveform. method.