JPS6132029A - Hologram scanner control device - Google Patents

Abstract

PURPOSE:To enable to correct magnification error due to variance of laser oscillation wavelength by changing number of rotation of a hologram scanner motor. CONSTITUTION:When the frequency of master clock signal generated by a master clock signal generator 16 is made to correspond to oscillation wavelength of a semiconductor laser by a master frequency selector switch 21, number of rotation of the motor of the hologram scanner is changed according to laser oscillation wavelegth through a detecting circuit 17 etc. that detects phase difference between output of a motor rotation detector 15 and master clock. Accordingly, scanning speed of the hologram scanner is varied corresponding to laser oscillation wavelength, and magnification error in the direction of main scanning is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hologram scanner control device in an optical recording device using a semiconductor laser and a hologram scanner.

(Prior Art) Semiconductor lasers are attracting attention as small, low-cost power supplies, but they also have problems. The problem is that when semiconductor lasers are mass-produced, variations occur in the oscillation wavelength of each semiconductor laser. GaA n As is the most popular semiconductor laser.
In the system, the oscillation wavelength can be changed by changing the mixed crystal ratio of GaAs and AflAs. On the other hand, when semiconductor lasers with a certain oscillation wavelength are mass-produced, the above-mentioned mixed crystal ratio varies slightly during the manufacturing stage, resulting in variation in the oscillation wavelength. FIG. 5 is an example of this, and shows data when the total number of samples is 700.

In an optical recording device such as a laser printer that uses such a semiconductor laser as a light source and a hologram scanner as an optical scanning device, if the oscillation wavelength of the semiconductor laser deviates from a set value, a scanning line will be distorted. Although the hologram grating pitch and scanning optical system have been optimized to minimize the curvature of the scanning line based on the set value of the oscillation wavelength of the semiconductor laser, the laser beam is This is because the diffraction angle changes from the set value, resulting in a curved scanning line.

FIG. 6 shows the relationship between the variation in the oscillation wavelength of the semiconductor laser and the image writing length in the main scanning direction in an optical recording apparatus in which the hologram scanner is optimized for the oscillation wavelength of the semiconductor laser of 790 nm.

(Objective) An object of the present invention is to provide a hologram scanner control device that can correct magnification errors due to variations in the oscillation wavelength of the semiconductor laser in an optical recording device using a semiconductor laser and a hologram scanner.

(Structure) The present invention is provided with means for varying the motor rotation speed of the hologram scanner in an optical recording apparatus having a semiconductor laser and a hologram scanner. Correct the magnification error due to

FIG. 2 shows an example of an optical recording device to which the present invention is applied.

A semiconductor laser drive circuit 1 drives a semiconductor laser 3 using a modulation signal from a phase synchronization circuit 2 to emit a laser beam modulated by the modulation signal.

This laser beam is reflected by a mirror 6 via a collimating lens 4 and a cylindrical lens 5, is deflected by a hologram scanner 7, and is irradiated onto the charged surface of a photoreceptor drum 11 via a mirror 8, a spherical lens 9, and a cylindrical lens 10. be done.

The hologram scanner 7 has a plurality of holograms made of linear gratings arranged at equal intervals on a flat substrate, arranged concentrically around a rotation axis, and a hologram disk 7a that deflects a laser beam, and this hologram disk 7a are attached coaxially. It consists of a motor 7b that rotates the hologram disk 7a in the same direction, and a motor drive circuit 7c that drives the motor 7b. Photosensitive drum 11
is rotationally driven by a main motor, and the irradiation spot of the laser beam moves repeatedly in the width direction by the rotation of the hologram disk 7a, thereby forming an electrostatic latent image.

This electrostatic latent image is developed by a developing device and transferred to a transfer paper or the like by a transfer device. The synchronization detector 12 is provided outside the image recording area, detects the laser beam deflected by the hologram disk 7a, and outputs a synchronization detection signal. The phase synchronization circuit 2 sends the synchronization detection modulation signal of a predetermined period generated by the synchronization detection modulation signal generation section to the semiconductor laser drive circuit 1 as a modulation signal, and also transmits the synchronization detection signal every time the synchronization detection signal is input from the synchronization detector 12. The video signal for one line is synchronized with the clock signal from the clock signal generation circuit 13 (
(one pixel at a time) in response to a clock signal, which is sent to the semiconductor laser drive circuit 1 as a modulation signal.

FIG. 1 shows the motor drive circuit 7c, and FIG. 3 is its time chart.

The rotation of the motor 7b is detected by a motor rotation detector 15 using a tachogenerator as a motor rotation sensor, and the motor rotation detector 15 outputs a pulse signal with a frequency proportional to the rotation speed of the motor 7b. On the other hand, the reference clock signal generator 16 generates a reference clock signal with a frequency corresponding to the oscillation wavelength of the semiconductor laser 3, and the phase difference between this reference clock signal and the output signal of the motor rotation detector 15 is detected by the phase detection circuit 17. Detected. This phase detection circuit 17
The output signal is applied to a pulse control circuit 19 through a low-pass filter 18, and the pulse width control circuit 19 outputs a pulse signal having a pulse width corresponding to the applied voltage.

The driver 20 drives the motor 7b using the output pulse of the pulse width control circuit 19, and the motor 7b drives the motor 7b so that the phase difference between the reference clock signal from the reference clock signal generator 16 and the output signal of the motor rotation detector 15 is constant. The rotation speed is controlled to be constant.

In this optical recording device, the oscillation wavelength of the semiconductor laser 3 is 79.
However, as mentioned earlier, the oscillation wavelength of semiconductor lasers varies from 780 to 800 nm, so if the scanning speed of the hologram scanner is selected for each semiconductor laser, the oscillation wavelength of the semiconductor laser can be adjusted. It is possible to correct magnification errors in the main scanning direction due to variations in the images. The ±10 nm oscillation wavelength variation of semiconductor lasers is ±1 magnification error with respect to the specified image writing length in the main scanning direction.
．． It is about 3%. Therefore, 780 to 800 nm is divided into a plurality of divisions, and a bridge is constructed so that the frequency of the reference clock signal generated by the reference clock signal generator 16 corresponding to each division can be arbitrarily selected using the reference frequency selection switch 21. If the frequency of the reference clock signal generated by the reference clock signal generator 16 is varied by the reference frequency selection switch 21 so as to correspond to the oscillation wavelength of the semiconductor laser 3, the scanning speed of the hologram scanner 7 can be adjusted to match the oscillation wavelength of the semiconductor laser. The magnification error in the main scanning direction is corrected.

FIG. 4 shows a motor drive circuit in another example of an optical recording device to which the present invention is applied. In this optical recording device, the magnification error in the sub-scanning direction is controlled by the main motor control circuit 22 in the above example.
This is corrected by . The main motor control circuit 22 is a PLL (Phase Lock-ed Loo).
p), and the reference clock signal generator 16
The main motor is driven in the same manner as the motor 7b described above by the reference clock signal from the main motor. That is, the rotation of the main motor is detected by a main motor rotation detector using a tacho generator of the motor rotation sensor, and the phase difference between its output signal and the reference clock signal from the reference clock signal generator 16 is detected by the phase detector. Ru. The output signal of this phase detector is applied to the pulse width control circuit via a low-pass filter, and the pulse width control circuit outputs a pulse signal with a pulse width corresponding to the applied voltage.This pulse signal causes the driver to control the main motor. is driven. Therefore, by varying the frequency of the reference clock signal with the reference frequency selection switch 21, not only the magnification error in the main scanning direction is corrected, but also the rotational speed of the photoreceptor drum 11 is changed to correct the magnification error in the sub-scanning direction. Ru.

(Effects) As described above, according to the present invention, a means for varying the motor rotation speed of the hologram scanner is provided in an optical scanning device having a semiconductor laser and a hologram scanner. It is possible to correct magnification errors due to variations in the oscillation wavelength of the semiconductor laser.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a motor drive circuit in an example of an optical recording device to which the present invention is applied, FIG. 2 is a block diagram showing the optical recording device, FIG. 3 is a time chart of the motor drive circuit, and FIG. Figure 5 is a block diagram showing a motor drive circuit in another example of an optical recording device to which the present invention is applied.
The figure shows an example of data on variations in the oscillation wavelength of a semiconductor laser, and FIG. 6 is a diagram showing an example of the relationship between the deviation of the semiconductor laser oscillation wavelength and the main scanning position deviation in a conventional optical recording device. 21...Reference frequency selection switch. 1σ Illusion ÷ 4 昶fFf;)D Agony most G interest

Claims (1)

[Claims] In an optical recording device that modulates the output beam of a semiconductor laser using a video signal and scans this beam with a hologram scanner, the hologram scanner control device includes means for correcting a magnification error by varying the rotational speed of a motor of the hologram scanner. .