JPS61273065A - Laser printer - Google Patents

Abstract

PURPOSE:To attain print without distortion while not being affected with fluctuated rotation of a rotary polygon mirror by using a light emitting element and a photodetector provided while clipping an encoder to detect a black line drawn on the encoder thereby forming a video clock signal. CONSTITUTION:The light emitting element 12 and the photodetector 13 provided while clipping the encoder 11 detect the black line of the rotated encoder 11 to generate a pulse-shape video clock signal, which is outputted to an optical modulator 3. The modulator 3 modulates a laserlight outputted from a laser oscillator 1 synchronously with a video clock signal (a) into ON/OFF signal corresponding to the print information and outputs the result to the rotary polygon mirror 6 via a lens 5. If the rotation of the mirror 6 slows down, the period of the video clock signal becomes longer and the deviation of print position on a face of a photosensitive body 10 is corrected and the signal is printed on a normal position. When the rotation becomes faster, the operation is executed inversely and the signal is printed on the normal position.

Description

[Detailed Description of the Invention] [Summary] A laser printer is provided with an encoder on the shaft of a rotating polygon mirror, detects position information written on the encoder at predetermined intervals by a detection means, and detects the position information written on the encoder at a predetermined interval. signal(
The modulation timing of the optical modulator is determined by a video clock signal), and by changing the modulation timing of print information in response to rotational fluctuations of the rotating polygon mirror, the deviation of the printing position on the photoconductor surface is corrected. Allows for distortion-free printing.

It is called Noh.

[Industrial application field]

The present invention relates to a laser printer, and more particularly to a laser printer that has been improved to eliminate printing deviations caused by rotational fluctuations of a rotating polygon mirror.

[Conventional technology]

FIG. 5 shows a block diagram of a laser scanning optical system of a conventional laser printer.

In FIG. 5, laser light output from a laser oscillator is focused by a lens 2 and input to an optical modulator 3.

The optical modulator 3 synchronizes with the video clock signal output from the timing signal oscillator 4 and outputs a high-power laser beam to 0N-O using an electric signal corresponding to the print information inputted from the outside.
After the FF changes and the light is focused through the lens 5, it is output to the rotating polygon mirror 6.

The rotating polygon mirror 6 is driven by a motor 7 to rotate at high speed via a rotating shaft (spindle) 8 . This rotating polygon mirror 6
The laser light that has passed through the lens 5 is sequentially irradiated onto each mirror surface, and the laser light reflected from each mirror surface passes through the projection lens 8 and prints one line at a time on the surface of the photoreceptor 10 as the mirror surface rotates.

The signal interval of the video clock signal is set to be the same as the interval between printed dots when the rotating polygon mirror rotates normally.

By ON-OFF modulating the print information into laser light in synchronization with this video clock signal, the photoreceptors 10 of each row are
The printing position and printing interval on the surface of the photoreceptor 10 are defined, and a predetermined latent image is formed on the surface of the photoreceptor 10.

[Problem that the invention seeks to solve]

In this conventional latent image method, if there is a variation in the rotation of the rotating polygon mirror, the position of the print (latent image) shifts in response to the rotational variation, as shown in the print diagram in FIG. 4, resulting in distorted printing.

The present invention was created in view of these points.
To provide a radar printer with a simple configuration that corrects deviations in ordered printing positions due to rotational fluctuations of a rotating polygon mirror and provides distortion-free printing.

(Means for solving the problem) As shown in FIG. 1, the laser printer of the present invention shown in FIG.
An encoder 11 having a pattern with a black border) is provided on the spindle 8, and position information detection means consisting of a light emitting element 12 and a light receiving element 13 is attached with the encoder 11 in between. ) controls the modulation timing of the optical modulator 3.

That is, the configuration is such that distortion-free printing can be performed by changing the modulation timing in response to rotational fluctuations of the rotating polygon mirror 6 and correcting the printing position on the surface of the photoreceptor 10.

[Effect]

A black border drawn on the encoder 11 is detected by a light emitting element 12 and a light receiving element 13 provided on both sides of the encoder 11, and a video clock signal having an interval equal to the interval between printed dots of the printer is created.

The optical modulator 3 modulates print information in synchronization with this video clock signal.

As a result, if the rotation of the rotating polygon mirror 6 changes,
For example, when the rotation becomes slow, the cycle of the video clock signal detected in accordance with the rotation speed of the rotating polygon mirror 6 becomes longer, and the modulation interval of the print information becomes longer, so the print position on the surface of the photoreceptor 10 becomes The positional deviation caused by the slow rotation is corrected and printing is performed at the correct position.

On the other hand, if the rotation becomes faster, the operation is opposite to the above and printing is performed at the correct position.

〔Example〕

FIG. 1 shows a block diagram of a laser scanning optical system according to an embodiment of the present invention. In this figure, the same parts as those in the conventional configuration shown in FIG. 5 are designated by the same reference numerals.

As is clear from the laser scanning optical system of this embodiment compared to the one shown in FIG.

As shown in FIG. 2, this encoder 11 has a pattern of black edges 16 drawn on the same circumference on one side of a transparent disk at the same intervals as the printing dot intervals of the printer. In addition, in this laser scanning optical system, the encoder 11
A black border 16 drawn on the encoder 11 is provided between the
A light-emitting element 12 and a light-receiving element 13 are attached to detect the signal and output a video clock signal to the optical modulator 3.

The operation is such that the black line of the rotating encoder 11 is detected by a light emitting element 12 and a light receiving element 13 provided on both sides of the encoder 11, and a pulsed video clock signal shown as a in FIG. and output it to the optical modulator 3.

The period T of this video clock signal a is set to be equal to the printing dot interval of the printer when the rotating polygon mirror 6 is rotating normally.

The optical modulator 3 adjusts the laser beam output from the laser oscillator 1 to 0 in synchronization with the video clock signal a in accordance with the print information.
The signal is modulated to N-OFF and output to the rotating polygon mirror 6 via the lens 5.

Each mirror surface of the rotating polygon mirror 6 reflects the incident laser light as it rotates, and prints by scanning the surface of the photoreceptor 10 line by line via the projection lens 9.

Now, if the rotation of the rotating polygon mirror 6 fluctuates, for example if the rotation slows down, the period of the video clock signal detected corresponding to the rotation speed of the rotating polygon mirror 6 will become longer, and the modulation interval of the printed information will change. As a result, the printing position on the surface of the photoreceptor 10 is corrected for positional deviation due to slow rotation, and printing is performed at the normal position.

If the rotation becomes faster, the operation is opposite to the above and printing is performed at the correct position.

FIG. 3 is a diagram showing another embodiment of the position detection means, and instead of the encoder having a pattern with a black border in the embodiment of FIG.
Position information is recorded on magnetic head 4, and position information is detected using magnetic head 1.
5 is used. This has the advantage that fine cycle intervals of the video clock signal can be obtained relatively easily.

〔Effect of the invention〕

As described above, according to the present invention, distortion-free printing is possible without being affected by rotational fluctuations of the rotating polygon mirror.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the laser scanning optical system of the present invention, Fig. 2 is a plan view showing an example of the configuration of an encoder, Fig. 3 is a schematic diagram showing a modified example of the position detection means, and Fig. 4 is a rotating polygon mirror. Fig. 5 is a block diagram of a conventional laser scanning optical system. In the figure, 1 is a laser oscillator, 2.5 is a lens, 3 is a photometer, 4 is a timing signal oscillator, 6 is a rotating polygon mirror, 7 is a motor, 8 is a spindle, 9 is a projection lens, 10
is a photoreceptor, 11 is an encoder, 12 is a light emitting element, 13 is a light receiving element, 14 is a magnetic recording disk, and igJl/lL4''
Lt4'tit+7-o-,7MFigure 1

Claims (1)

[Scope of Claims] A light modulator (3) that modulates laser light according to printing information, and a laser that irradiates the output light of the light modulator (3) onto a rotating polygon mirror (6) and prints with the reflected light. In the printer, an encoder (11) in which position information is written is placed on the rotation axis (8) of the rotating polygon mirror (6), and the encoder (11)
), each of the laser printers is provided with detection means (12, 13) for detecting positional information, and the modulation timing of the optical modulator is determined by the output of the detection means.