JPH01285032A - Reproduction device for optical disk - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture of good S/N easily by obtaining the signal component corresponding to the crosstalk fed from an adjacent track based on the signal from which 2nd and 3rd detectors are detected and correcting the signal fed from a 1st detector by using this signal. CONSTITUTION:The detection signal transmitted from a 1st detector 11 detecting the reflection light of a main beam and the detection signal transmitted from the 2nd and 3rd detectors 12, 13 located before and behind this 1st detector 11 and by sliding to the right and left are made so that the detection time points may be coincident via delay mans 22, 25, 26. The signal detected by the 2nd and 3rd detectors 12, 13 is added by an opposite phase to the signal detected by the 1st detector 11 and taken as a RF signal by correcting the signal detected by the 1st detector 11. The noise generation due to the crosstalk of a television scope is therefore prevented. Consequently a reproduced picture of good quality with a good S/N is obtd.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention provides an improved optical type RF signal regeneration means that eliminates crosstalk signals from adjacent tracks, especially in an RF multiplied signal. The present invention relates to a disc playback device.

(Prior art) For example, in order to reproduce recorded data from an optical video disc, a laser beam is irradiated onto the recording track portion of the disc, the reflected light is detected by a pickup, and the detected signal is amplified appropriately. RF multiplied signal for television playback.

FIG. 2 shows an example of a conventional playback device, in which a 3-beam optical pickup includes a first detector 11 that detects the reflected light of the main beam directed toward the center of the track; Second and third detectors 12 are located before and after the first detector 11, respectively.
and 13. The second and third detectors are set to have a phase shift of 90'' with respect to the center of the track, and detect the reflected light of the two sub-beams directed before and after the main beam.

The first detector 11 includes four small detectors A to D corresponding to each of the four areas obtained by dividing the plane, and each of these small detectors A to D receives reflected light from the track. The signals detected by each of these small detectors A to D are combined by extracting only high frequency components, amplified by an RF amplifier 14, and then supplied to a video amplification circuit 15.

Moreover, the small detectors A-D of the first detector 11 are
By suitably synthesizing and differentially amplifying the signals from the focus servo circuit IB and supplying the signals to the focus servo circuit 16, the focus coil 17 is driven by the output signal from the focus servo circuit IB, and focus control of the focus section is performed.

Furthermore, one detector E and one F are set for the second and third detectors 12 and 13, respectively.

The signals detected by the detectors E and F are differentially amplified and supplied to the tracking servo circuit 19, which drives the tracking coil 20 according to the difference between the rain detection signals to perform tracking control of the pickup section.

In such a reproducing apparatus, when the beam spot diameter of the main beam for reproducing signals recorded on a track of a disk is not constant, the first detector 11 detects a signal from a track adjacent to the target track. Includes crosstalk. When such low talk comes to be included in the RF multiplied signal, the low frequency component of this crosstalk appears on the television screen and becomes noticeable as noise. Therefore, in order to obtain a reproduced screen with a good S/N ratio, it is necessary to manage the size of the beam spot of the main beam with high precision, which is difficult from a technical and cost perspective.

(Problems to be Solved by the Invention) The present invention was developed in view of the above points, and therefore effectively utilizes conventionally existing components to produce high-quality tracks free of crosstalk components from adjacent tracks. It is an object of the present invention to provide an optical disk reproducing device that reproduces RF multiplied signals and allows a television screen with good S/H to be easily and reliably obtained.

[Configuration of the Invention (Means for Solving the Problem) In the optical disc playback device according to the present invention,
A detection signal from a first detector that detects the reflected light of the main beam, and detection signals from second and third detectors located before and after the first detector and shifted from left to right are transmitted through a delay means. The detection time points are made to coincide, and in this state, the signals detected by the second and third detectors are added to the signal detected by the first detector in opposite phases, and the signals are detected by the first detector. The resulting signal is corrected and converted into an RF multiplied signal.

(Function) In the playback device configured as described above, a signal component corresponding to crosstalk from adjacent tracks is obtained based on the signals detected by the second and third detectors. Therefore, by correcting the signal from the first detector using this signal, an RF multiplied signal with the crosstalk component canceled can be obtained.
/N good television screen can be obtained.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the circuit configuration of an optical disk reproducing apparatus according to the present invention, which includes a first detector 11 similar to the conventional apparatus, and second and third detectors 12 and 13.

The detection signals from each of the four small detectors A to D of the first detector 11 are used to extract only the high frequency components by a capacitor circuit and are added together. The signal is appropriately amplified and supplied to the first delay circuit 22.

In addition, the signals detected by the second and third detectors 12 and 13, detectors E and F, respectively, are filtered through capacitor circuits to extract high-frequency components, and then filtered through bandpass filters 23 and 24, respectively, which have the greatest influence on the video signal. Extracts only the low-frequency signal that gives . The second detector 11 is located at a position preceding the first detector 11.
The output signal from the band-pass filter 23 to which the detection signal from the detector 12 is supplied is taken out via the second and third delay circuits 25 and 26 set in series, and is output from the band-pass filter 24. The detection signal from the third detector 13 is combined with the detected signal from the third detector 13. Then, in the differential amplifier 27, the detection signal from the first detector 11 from the delay circuit 22 and the above-mentioned combined signal are added in opposite phase. That is, the signal detected by the first detector 11 is corrected by subtracting the signal detected by the second and third detectors 12 and 13, and then amplified by the RF amplifier 14 and then transmitted to the video circuit 1.
5.

Here, the first to third delay circuits 11.25.26
The respective delay times T1 are set to be the same. This delay time Tl is the difference between the main beam detected by the first detector 11 and the second and third detectors 12 and 1.
It is set based on the relationship between the distance to the sub-beams detected in step 3 and the linear velocity at which the tracks set on the disk are scanned. For example, the linear velocity is 11 to 14 m/see
If the distance between the main beam and the sub-beam is 20 μm, the delay time TI is Tl - (20/1 B) x 10-6 (μsec
).

Using the rear sub-beam as a reference, two stages of delay circuits with a delay time T1 are set for the preceding sub-beam, and one stage delay circuit is set for the main beam, so that each beam can be detected. Signals for detecting time points, ie, the same points on the track, can be obtained at the same time points.

Note that the focus control and tracking control of the optical pickup including the generation source of each beam and each detector can be configured in the same manner as the conventional one described above.

That is, in a disc playback device configured in this manner, the signal detected by the second detector 12, which precedes the main beam and detects the sub-beam with a phase shift of 90°, particularly affects the video signal. The low-frequency component and the low-frequency component that particularly affects the video signal of the signal detected by the third detector 13 that detects the sub-beam located behind the main beam and with a phase shift of 190° are detected. The images are synthesized with the detection time points matched. and,
The combined signal component is further subtracted from the signal component detected by the first detector 11 with the detection time points coincident. Therefore, through this step, an RF multiplied signal from which crosstalk components from adjacent tracks have been removed is obtained,
This RF multiplied signal is supplied to the video circuit 15.

[Effects of the Invention] As described above, according to the optical disc reproducing apparatus according to the present invention, crosstalk signal components from adjacent tracks are canceled out, which is useful when reproducing a video signal, for example. Therefore, noise due to crosstalk does not occur on the television screen, and a high-quality reproduction screen with a good S/N ratio can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for explaining an optical disk reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional reproducing apparatus. 11...First detector, 12.13...Second and third detector, 14...RF amplifier, 22.
25.2B...Delay circuit, 23.24...Band pass filter. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Scope of Claims] A first detector that detects reflected light of a main beam directed toward the center of a recording track of an optical disc; second and third detectors that detect the respective reflected lights of the two sub-beams whose phase is shifted by 90 degrees with respect to the center of the recording track; and detection signals from the first to third detectors;
a delay means that sets a predetermined delay time corresponding to the interval between these detectors and the scanning line velocity, and matches the detection time points of each detection signal; and a correction means for adding the signals detected by the second and third detectors in opposite phase to the signal detected by the first detector, and the correction means adds the signals detected by the second and third detectors in reverse phase. An optical disc playback device characterized in that crosstalk components from tracks are canceled.