JPH0963081A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain track error signals matching with a CD and a high density disk through automatically switching. SOLUTION: An output from a laser 1 of an optical disk device is made five beams B0-B2 of 1st-order light, 2nd-order light together with zero-order light by a diffraction grating 2, and the track error signals TL, TH are obtained from a light spot by a 1st-order diffracted beam in the case of the high density disk, and from the light spot, by a 2nd-order diffracted beam in the case of the CD for the track of the optical disk 5, and the disk is decided by a comparator 11. Thus, correct track error signals are obtained automatically respectively for respective disks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc reproducing apparatus capable of reproducing both a high density recorded disc and a standard density recorded disc such as a CD.

[0002]

2. Description of the Related Art Video data and audio are recorded on a digital disk such as a CD (compact disk) to reproduce moving images and audio. Furthermore, a high-density disc that is about four times as large as a CD has been developed. The linear velocity of these density discs is about double, and the track pitch is about 1/2.
It is.

When reproducing a high density disc, it is necessary to reduce the light spot, and a laser having a short wavelength is used. Further, tracking servo is performed by obtaining a track error signal by the three-beam method matched to the track pitch.

In order to reproduce both the CD and the high density disc, it is necessary to detect which disc is loaded (mounted). For this reason, the disc is put in a cartridge in advance, and an identification mark is provided on the cartridge to detect and discriminate.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, a tracking error signal is transmitted to a disc and a high-density disc, which have different recording densities and different track pitches, so that either disc can be reproduced. An optical disk device is obtained.

[0006]

SUMMARY OF THE INVENTION The present invention comprises means for generating a plurality of light beams through a diffraction grating, a detector for detecting reflected light from an optical disc corresponding to a 0th order beam, and reflection of 1st order diffracted light. Discriminating the level of the detection signal obtained from the first set of detectors receiving the light, the second set of detectors receiving the reflection of the second-order diffracted light, and the first or second set of the detectors. The optical disc device is characterized by comprising a discriminating means for switching the tracking error signal.

Further, according to the present invention, a means for generating a plurality of light beams via a diffraction grating, a detector for detecting the reflected light from the optical disk corresponding to the 0th order beam, and a first for receiving the reflection of the 1st order diffracted light. A set of detectors, a second set of detectors that receives reflection of second-order diffracted light, and a determination unit that determines the level of a detection signal obtained from the first or second set of detectors, It is an optical disk device characterized by comprising switching means for switching the operation output of the signals detected by the first or second set of detectors by the discrimination means, and switching the tracking error signal.

Further, according to the present invention, the differential output of the output of the pair of detectors which receives the reflection of the first-order diffracted light is used as the tracking error signal of the disk recorded at high density, and the other of which receives the reflection of the second-order diffracted light. It is an optical disk device that uses a differential output of the outputs of a pair of detectors as a tracking error signal of a disk recorded at standard density.

Further, according to the present invention, the differential output of a set of detectors receiving the reflection of the first-order diffracted light and the differential output of the output of another set of detectors receiving the reflection of the second-order diffracted light are compared and discriminated. It is an optical disk device that serves as a determination unit.

The present invention is also an optical disk device which serves as a discriminating means for discriminating by comparing a differential output of signals obtained from the first or second set of detectors with a predetermined level.

Further, according to the present invention, the differential output of the signals obtained from the first or second set of detectors is discriminated and the tracking servo gain is switched based on the discrimination result.
It is the described optical disk device.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A plurality of beams are generated by passing a laser beam through a diffraction grating, and a set of beams of first-order diffracted light (first-order light) is spotted at a pitch of about 1/2 of the track pitch of a high-density disc. A detector that forms each image and detects each reflected light, and another set of detectors that detect the reflection of the beam of the secondary diffracted light (secondary light) are provided, and the differential output of the detector of the primary light is set. The tracking error signal of a high density disc and the differential output of the detector output of the secondary light are obtained as a tracking error signal of a general disc such as a CD, and these are discriminated and used to obtain a tracking error signal suitable for reproduction of a predetermined disc. obtain.

In a CD having a large track pitch, the detection phases of the respective light spots are just opposite phases, so that signals are added through a differential amplifier to produce a large output, and in one high-density disc, the track pitch is almost the same. 1 / CD
Therefore, the detection outputs of the respective light spots have the same phase, and the differential outputs are canceled out and hardly appear. It is possible to determine the level of the operation output and switch to the tracking error signal suitable for the disc to be reproduced from now on, and to automatically set the reproduction conditions suitable for the discs with different recording densities, and set the reliable and stable tracking. Servo can be performed.

[0014]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a diagram showing the path of a laser beam for optical pits-up in the optical disk device of the present invention, showing the flow of multiple beams. The beam from the laser diode 1 is split into a plurality of beams via a beam splitter (diffraction grating) 2. Of these, up to the second order diffracted beam is used. As a result, the 0th-order beam B0 and the beam B1 of the 1st-order diffracted light are
Similarly, one set of secondary beams B2 is generated on the left and one set of secondary beams, and the secondary beams B2 are focused on the objective lens 4 through the half mirror 3 to form spots on the information recording surface of the disk 5, respectively.

The reflected light from the information recording surface of the disk 5 passes through the opposite optical path and passes through the half mirror 3 to form an image on the photodetector 6 shown in FIG. 1B, and these five beam spots SO, SE, From the detectors O, E, F, G, H of the photodetector 6 arranged corresponding to SF, SG, SH, the detection output corresponding to the reflection of each beam spot on the information recording surface of each disk 5 is obtained. In addition, 0 shown in FIG.
A signal (HF) to be reproduced and a focus control signal (Focus) are obtained from the detection unit O at the center of the photodetector 6 corresponding to the secondary diffraction beam.

The detection outputs of the detectors E and F of the photodetector 6 corresponding to the first-order diffracted beam are IV converters 7-1 and 7
The differential signal TH is obtained by the differential amplifier 8 via -2. Similarly, a signal corresponding to the second-order diffracted beam is output from the detection outputs of the detectors G and H of the photodetector 6 through the IV converters 7-3 and 7-4 to obtain the difference signal TL by the differential amplifier 8 '. TH and TL
Is selected by the switch 9 to obtain the tracking error signal TR.

As shown in FIG. 2, a beam spot is formed on the track T of the high density disc 5-1 via the lens 4.
The beam spots SE and SF are the pitch d1 of the track T.
Are arranged at a position of an interval of about 1/2, and the tracking error signal TH is obtained from the differential output. On the other hand, in the case of the general disc 5-2 such as a CD, as shown in FIG.
Since the spots SG and SH due to the second-order diffracted beam occur at twice the angle of the first-order beam corresponding to this, the track pitch d2 is just for this disc.
Tie at 1/2 the interval as shown.

By using the track error signals TH and TL by these reflected lights by switching them with the switch 9, the track error signal TR can be correctly obtained even if the kind of the target disk is changed from high density to general standard density CD. Obtainable. The automatic switching of the switch 9 will be described based on the flow chart shown in FIG. When the disc is mounted on the optical disc device and loaded to the reproduction position on the turntable (S1), the focus servo is turned on,
A beam spot is formed on the information recording surface of the optical disc 5, and the detection unit O of the photodetector 6 detects reflection from the disc, and focus control of the optical pickup is performed (S2) (focus servo is performed while rotating the disc. You can put it in).

The spindle motor is started up and the disc is driven to rotate, and the detectors E, F and G, H of the photodetector 6 of the optical pickup detect the IV converters 7-1 and 7-.
The signals for tracking control converted into voltage signal waves at 2 and 7-3 and 7-4 are differentially amplified at differential amplifiers 8 and 8 ′ to obtain TH and TL. The TL shown in FIG. 1B is compared with the reference voltage VE by the comparator 11 via the rectifier 10 to determine the type of disk (S4).

In the case of a normal disk, as shown in FIG. 3, the spots SG and SH are positioned with respect to the track T ', and when the spots SG and SH are relatively moved from the detectors G and H of the photodetector 6 in the track cross direction due to eccentricity or the like. The detection output is obtained.
From the IV converters 7-3 and 7-4, detection outputs of sine waves of opposite polarities are obtained as shown in G and H of FIG. 5, and the output TL of the differential amplifier 8 ′ is twice that. It becomes the output a. This TL
The signal is supplied to the voltage value a ′ via the rectifier 10 and the comparator 1
At 1, the disc is compared with a predetermined small reference voltage VE to discriminate a normal disc, and tracking servo is performed (S5).

In the case of a high density disc, the spots SG and SH are at the same relative positions with respect to the track T shown in FIG.
As the detection signal from H, the in-phase waveforms of G'and H'shown in FIG. 5 are obtained, the output of the differential amplifier 8'is a signal of a minimum level, and the rectified voltage b'through the rectifier 10 is the reference voltage. VE
Since it is extremely smaller than that of, the track servo is performed by discriminating it as a high density disc (S6).

The output of the comparator 11 is sent as discrimination data to a control computer (not shown) to switch the switch 9, and in the case of a normal disc, TL is output as a reproduction servo output TR and S5 and tracking servo are performed. It Further, in the case of a high density disc, TH is output as a reproduction servo output TR and S6, a tracking servo is performed.

Further, based on the discrimination output information obtained by the present invention, the size of the beam spot of the optical pickup is expanded or reduced, and the gain of the servo loop is switched so that the disc and the beam having different track pitches are reflected. It is possible to switch the setting to reproduction conditions that suit different discs. Although the above description has explained the discrimination using the second-order diffracted light, it is possible to make the discrimination using the first-order diffracted light, but the margin for the determination becomes small.

[0024]

According to the present invention, it is possible to automatically switch the track error signals which are suitable for the optical disks having different densities.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part of an optical disk device of the present invention, (a) is a diagram showing a beam path, and (b) is a block diagram for detecting a track error signal.

FIG. 2 is a diagram showing a beam spot on an information recording surface of a high density disc.

FIG. 3 is a diagram showing a beam spot on an information recording surface of a general disc.

FIG. 4 is a flowchart of a main part of tracking servo switching of the optical disk device of the present invention.

FIG. 5 is a diagram illustrating a tracking error signal waveform and discrimination.

[Explanation of symbols]

 1 laser diode 2 beam splitter 3 half mirror 4 objective lens 5 disk 5-1 high density disk 5-2 general disk 6 photodetector 7-1 to 4 IV converter 8, 8'differential amplifier 9 switch 10 rectifier 11 comparator

Claims (6)

[Claims] 1. A means for generating a plurality of light beams via a diffraction grating, a detector for detecting reflected light from an optical disc corresponding to a 0th order beam, and a first set of a first set receiving a reflection of 1st order diffracted light. A tracking error is provided which includes a detector, a second set of detectors that receives the reflection of the second-order diffracted light, and a determination unit that determines the level of a detection signal obtained from the first or second set of detectors. An optical disk device characterized by switching signals. 2. A means for generating a plurality of light beams via a diffraction grating, a detector for detecting reflected light from an optical disk corresponding to a 0th order beam, and a first set of a first set for receiving reflection of the 1st order diffracted light. A detector, a second set of detectors that receives the reflection of the second-order diffracted light, a determination unit that determines the level of a detection signal obtained from the first or second set of detectors, and the determination unit. An optical disk device comprising switching means for switching the differential output of the signals detected by the first or second set of detectors, and switching the tracking error signal. 3. A pair of detectors that receive the reflection of the second-order diffracted light by using the differential output of the outputs of the pair of detectors that receive the reflection of the first-order diffracted light as a tracking error signal of the disc recorded at high density. 3. The optical disk device according to claim 1, wherein the differential output of the output of the container is used as a tracking error signal of a disk recorded at a standard density. 4. Discrimination means for comparing and discriminating between the differential output of a set of detectors receiving the reflection of the first-order diffracted light and the differential output of the output of another set of detectors receiving the reflection of the second-order diffracted light. The optical disk device according to claim 1 or 2. 5. The optical disk device according to claim 1, wherein the discriminating means discriminates by comparing the differential output of the signals obtained from the first or second set of detectors with a predetermined level. 6. The optical disk device according to claim 1, wherein the differential output of the signals obtained from the first or second pair of detectors is discriminated and the tracking servo gain is switched based on the discrimination result.