JPH01107230A - Light beam scanning device - Google Patents

Abstract

PURPOSE:To improve the quality of a reproduced image by correcting the frequency of a picture element clock with respect to the variance in the light beam scanning time of every plane of a polygon mirror and the position of the picture element clock with respect to the variance in the scanning time in a scanning image plane respectively. CONSTITUTION:A thinning circuit 8 is provided with a flipflop and a gate circuit and outputs two-phase signals PCKa and PCKb obtained by thinning the picture element clock PCK from a synthesizer 7 into half to a phase modulation circuit 9. A clock synthesis circuit 11 is constituted by providing a gate circuit and synthesizing two-phase signals PCKa' and PCKb' which are modulated in terms of phase from the phase modulation circuit 9 into one-phase signal so as to output from a terminal T3. In case of using the signal from the terminal T3 in a printer device, it is impressed on an A/O optical modulation part and in case of using said signal in a scanner device, it is impressed on a circuit which samples a read image signal so as to correct a scanning position in a main scanning direction. Thus, the quality of the reproduced image can be prevented from being deteriorated.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a light beam scanning device, and particularly to a light beam scanning device used in a scanner device or printer device that scans a light beam using a rotating polygon mirror and controls a pixel clock. Regarding equipment.

[Conventional technology]

Conventional light beam scanning devices are used in scanner devices that read images by scanning a light beam from a laser with a rotating polygon mirror, and in printer devices that record images, and generate pixel clocks in synchronization with the scanning of the frontispiece polygon mirror. . in this case,
The scanning time of the light beam differs for each face of the rotating polygon mirror due to the rotational accuracy of the motor that drives the rotating polygon mirror, so-called rotational unevenness, so if pixel clocks with the same frequency are used, so-called judder will occur and the reproduced image quality will deteriorate. 0 Conventionally, as a means to solve this drawback, the scanning time of the light beam for each surface of the rotating polygon mirror is measured in advance.
There is a pixel clock control method in which a frequency value for each surface is set in synchronization with the operation of a rotating polygon mirror in accordance with the amount of deviation from the frequency of a reference pixel clock.

[Problem that the invention seeks to solve]

The pixel clock control method of the conventional light beam scanning device described above sets the pixel clock frequency for each face of the rotating polygon mirror, so variations in scanning time within the scanning screen cannot be corrected, so the reproduced image There is a problem that the image quality deteriorates.

An object of the present invention is to provide a light beam scanning device that can correct variations in the scanning time of a light beam on each surface of a rotating polygon mirror and the scanning time within a scanning screen.

[Means for solving problems]

The light beam scanning device of the present invention includes a scanning surface detector that identifies each surface of a rotating polygon mirror for main scanning with a light beam and outputs surface information; A frequency value generator that sets a pixel clock frequency value proportional to the beam scanning time and outputs the pixel clock to the synthesizer, and outputs an n-phase signal by thinning the pixel clock to l/n (n is a positive integer). a thinning circuit that modulates the phase of the signal from the frequency value generator using a position correction signal for each surface of the rotating polygon mirror from a correction signal generator, and a phase modulation circuit that modulates the phase of the signal from the frequency value generator and outputs the signal; It has a clock synthesis circuit that synthesizes and outputs a one-phase signal.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a signal waveform diagram for explaining the operation of this embodiment. This will be explained with reference to FIGS. 1 and 2.

The photodetector 1 includes a photodiode and a comparator, and outputs a signal obtained by detecting the reflected light of the light beam irradiated onto the rotating polygon mirror 4 from the laser 5 to the scanning surface detector 2.

The scanning surface detector 2 is configured with a counter circuit and a gate circuit, and detects the rotation being scanned by a signal MPH8 representing one rotation of the main scanning motor 3 that drives the rotating polygon mirror 4 and a signal from the photodetector 1. Polygonal mirror.

The surface information identifying each surface of is output to a frequency value generator.

The frequency value generator 6 includes a memory, a counter circuit, and a gate circuit, and stores in advance a pixel clock frequency value proportional to the light beam scanning time of each surface of the rotating polygon mirror 4 from the terminal T1 in the memory. The stored pixel clock frequency value is synchronized with each surface of the rotating polygon mirror 4 and output to the synthesizer 7.

The synthesizer 7 generates a pixel clock PCK based on the pixel clock frequency value from the frequency value generator 6 and outputs it to the thinning circuit 8 .

The thinning circuit 8 includes a flip 70 tube and a gate circuit, and receives the pixel clock PCK't from the synthesizer 7.
- Signals PCKa and PCK thinned out to 1/2 and converted into two-phase 17
b is output to the phase modulation circuit 9.

The correction signal generator 1o includes a memory, a counter circuit, and a gate circuit, and stores in advance the deviation value of the scanning speed within the scanning screen for each surface of the rotating polygon mirror 4 from the terminal T2 in the memory. The deviation value is used as the position correction signal C8G.
The signal is outputted to the phase modulation circuit 9 in correspondence with the light beam scanning position.

The phase modulation circuit 9 includes a sawtooth wave generation circuit, an adder circuit, and a comparator. Two-phase pixel clock PCKa, PC
Two-phase signals PCKa', PCKb' obtained by phase modulating Kb
is output to the black signal synthesis circuit 11.

The clock synthesis circuit 11 includes a gate circuit,
A two-phase signal PCKa phase-modulated from the phase modulation circuit 9
', PCKb' are combined into a one-phase signal and output from terminal T3.

In the above embodiment, the example of thinning out by the thinning circuit 80 is 1/2, but the thinning value may be a natural number of 2 or more.

The signal from terminal '11'3 obtained in this way is
When used in a printer device, it is applied to the A10 light modulation section, and when used in a scanner device, it is applied to a circuit that samples the read image signal to correct the scanning position in the main scanning direction. Can be done.

〔Effect of the invention〕

As explained above, the present invention adjusts the frequency of the pixel clock to deal with variations in the light beam scanning time for each surface of a rotating polygon mirror, and adjusts the position of the pixel clock to deal with variations in the scanning time within the scanning screen. By correcting f respectively, the scanning position of each surface of the rotating polygon mirror can be corrected, which has the effect of improving the quality of the reproduced image.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a signal waveform diagram for explaining the operation of this embodiment. 1...Photodetector, 2...Scanning surface detector, 3...Main scanning motor, 4...Rotating polygon mirror, 5...Old... Laser, 6... Frequency value generator, 7... Synthesizer, 8... Thinning circuit, 9... Phase modulator, 1o... ...Correction signal generator 111...Clock synthesis circuit. Agent Patent Attorney Uchihara Kai

Claims (1)

[Claims] a scanning surface detector that identifies each surface of a rotating polygon mirror for main scanning with a light beam and outputs surface information; and a pixel clock frequency that corresponds to the surface information and is proportional to the light beam scanning time of each surface of the rotating polygon mirror. a frequency value generator that sets a value and outputs a pixel clock to a synthesizer, and a frequency value generator that outputs a pixel clock to a synthesizer;
(n is a positive integer) and a decimation circuit that outputs a signal that has been decimated into n-phase signals; A light beam scanning device comprising: a phase modulation circuit that modulates and outputs the signal; and a clock synthesis circuit that combines the output from the phase modulation circuit into a one-phase signal and outputs the signal.