JPS5857639A - Information reproducer - Google Patents

Abstract

PURPOSE:To detect an error of the track fluctuation, by receiving the reflected light given from a recording medium at a detector which is divided by a dividing line parallel to a track and passing through the optical axis of an optical system and feeding back the amplitude difference of a reproduced signal to the optical system. CONSTITUTION:The optical axis of the reflected light given from a rotary disk 8 is bent via a polarizer 10 and a beam splitter 5', and the reflected light is received at a light detector 6' which is divided by a dividing line passing through the optical axis of an optical system. The information signals read out of the detector 6' are filtered 11 and 12, and the output of addition 13 of these signals is used as an information reproducing signal 14. On the other hand, the outputs of the filters 11 and 12 are fed to absolute value circuits 15 and 16 to be filtered 17 and 18 for rectification. Thus an envelope curve is obtained, and the output of a differential amplifier 19 set between envelope curves is fed back to a polarizer 10 in the form of a track error signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup device for an optical video disc device.

A video disk device irradiates a focused light spot onto minute accumulated information spirally recorded as a rotating groove pattern or a pattern of appropriate refractive index changes on a disk-shaped recording medium, and then produces a modulated reflection. The information stored in the recording medium is read by detecting light or transmitted light as a reproduction signal corresponding to the stored information. A pickup device that irradiates a focused light spot and detects information uses a gas laser such as He-Ne or a semiconductor laser as a light source, and includes an objective lens, a photodetector, etc.

FIG. 1 shows an example of a pickup device using a semiconductor laser as a light source. This pickup device uses a semiconductor laser 1
A condensing system that condenses and irradiates the output light onto an information recording surface on a recording medium through a collimator lens 2, a quarter-wave plate 3, and an objective lens 4, and a beam splitter 5 splits the reflected light from the information recording surface. , and a detection system leading to the detector 6. A collimating lens 2, a wave plate 3, an objective lens 4, a beam splitter 5, etc. are housed in a lens barrel 7. In an optical video disc device having such a pickup device, in order to accurately reproduce the information stored on the R1 recording medium, a condensed light spot is recorded in a spiral shape on the recording medium. It is necessary to carry out track control so as to accurately track and irradiate the information array that has been created, and at the same time, it is necessary to reliably control the focus of the irradiated light. However, in actual use, the focal position of the light spot cannot be adjusted if the light spot is fixed at one point and irradiated due to the effects of surface runout during high-speed rotation of the recording medium disk, external vibrations, etc. It is more likely that the information will be matched exactly to the example.

Therefore, it is necessary to add a fluctuation error detection control system to the optical video disc device for automatically correcting the irradiation position of the light spot by following positional fluctuations caused by vibrations of the disc, etc. The present invention In view of the above-mentioned problems, it is an object of the present invention to provide a new and useful pickup device capable of detecting track fluctuation errors in track control.

Hereinafter, the present invention will be explained in detail according to embodiments with reference to the drawings.

FIG. 2 explains one embodiment of the present invention, and is a block diagram of an information reproducing apparatus that reads information while tracking a specific groove.

In FIG. 2, 8 is a rotating disk, 9 is a track on the disk, and information is frequency-modulated or pulse-modulated by irregularities or shading. Semiconductor laser 1'
The light beam that exits passes through the collimating lens 2',
After the light lqi is bent by 0, it is focused by an objective lens 4') and is irradiated onto a trunk 9 on a disk 8. The optical axis of the light reflected from the disk 8 is bent by a beam splitter 5', and the light is directed to a photodetector 6'.

The photodetector 6' is arranged in the direction of the second track of the disk.
It is divided into two parts by a dividing line that passes through the optical axis. The output of each photodetector passes through a bandpass filter I+, +2.

A part of them is added by an adding circuit 13 and becomes an information reproduction signal 14. Another part of the output of the bandpass filter 11.12 is rectified by an absolute value circuit 15.16 and then enveloped by a low-pass filter 17.18. The envelope of each photodetector output is differentially amplified by a differential amplifier 19, and the differential output is used to deflect the optical deflector 10.

The functions of each element in the configuration shown in FIG. 2 will be explained in detail below. As shown in FIG.
Consider the case outside of . In this case, the information signals read out by the photodetector 6' are shown in FIGS. 3(a) and 3(a), respectively.
The waveform is shown in b). That is, when the irradiation beam 20 irradiates a location shifted from the center of the track 9, a difference appears in the amplitudes of the two information signals.

If the center of the trunk is still being illuminated, the amplitudes are equal; conversely, if the inside of the truck is being illuminated, the difference in amplitude is the opposite. Therefore, the trunk error signal can be obtained using this amplitude. Of the output of the photodetector 6', only the signal in the frequency band of the information signal is filtered by the bandpass filter 11, 12.

Thereafter, when each of the two information signals is input to the absolute value circuits 15 and 16, the outputs have the waveforms shown in FIGS. 3(c) and 3(d). A low-pass filter 17 extracts components in a frequency band equal to the track fluctuation frequency from this output signal.
After filtering at 18, differential amplification is performed at a differential amplifier 19. The outputs of the low-pass filter are shown in FIGS. 3(e) and 3(f), and the output of the differential amplifier 19 is shown in FIG. 3(g).

With the above configuration, it is possible to extract the difference in amplitude of the information reproduction signal from the photodetector 6'. As described above, this difference in amplitude corresponds to the trunk error, so this differential signal is used as a tracking error signal to drive the optical deflector 10. That is, in response to the tracking error signal shown in FIG. 3(g), the optical deflector 10 rotates toward the inside of the disk and moves the irradiation spot 20 inward. If the illumination spot 20 passes more inside the track 9, a tracking error signal will appear as well, causing the optical deflector 10 to rotate to the outside of the disk and move the illumination spot 20 outwards1, so that the light beam will move past the rotating disk. Even if the disc 8 is unevenly distributed, it is possible to automatically track the specific track to be reproduced without deviating from it, and it is possible to read and reproduce the information recorded on the rotary disk 8 without error.

As described in detail above, according to the present invention, it is possible to correctly reproduce information from a disk on which information is recorded at high density while controlling the track of desired information even if the rotating disk is vibrated due to disturbance. This established a highly reliable technology for reproducing recorded information.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional pink-up device. FIG. 2 is a configuration diagram of an information reproducing apparatus showing one embodiment of the present invention. Figures 3(a) and (b) are waveform diagrams showing the output of the information reproduction signal of the photodetector divided into two, Figure 3(C), and (a) are waveform diagrams showing the output of the information reproduction signal of the photodetector divided into two. 3(e) and 3(f) are waveform diagrams showing the envelopes of FIG. e
) and (f) are waveform diagrams showing differential signals. 1.1'...Semiconductor laser, 2.2'...Collimating lens, 3...1/4 wavelength plate, 4. '4'...Objective lens, 5°5'...Beam splitter, 6,6'...
Photodetector, 8... Optical deflector, 11.12... Bandpass filter, 13... Adder, 14... Information reproduction signal, 15++6... Absolute value circuit, 17.18 ...Low pass filter, I9/differential amplifier, 20...Irradiation spot. Agent Ben J! 11th Master Fukushi Ai Produced Rice 181- -7

Claims (1)

[Claims] 1. In an information reproducing device that reproduces the information through an optical system from reflected light or transmitted light of focused light irradiated onto a recording medium on which information is recorded, reflected light or transmitted light from the recording medium is used. The light is received by photodetectors parallel to the recording information track and divided by a dividing line passing through the optical axis of the optical system, and the information signals read from each photodetector are rectified and the rectified output is rectified. An information reproducing device characterized in that track control is performed by feeding back to an optical system using differential output between envelopes.