JPS59152541A - Optical disk record reproducer - Google Patents

Abstract

PURPOSE:To attain the satisfactory tracking servo by giving limitation to the output amplitude given from a detector which produces a phase difference component signal by means of the timing using between the phase difference component signals and then stabilizing, sampling and synthesizing said output amplitude to produce a tracking error signal. CONSTITUTION:Four outputs given from a 4-split photodetector 11 are turned into two phase difference component signals by a phase or time difference component signal producing circuit 12 consisting of two adders which obtain the sum of every duagonal component. These two signals are led directly to both input terminals of a phase difference detector 13 as well as to an input terminal of each of the 1st and 2nd multipliers 14 and 15 via the 1st and 2nd amplitude limiters 10a and 10b. Here the corresponding multiplication is carried out between those two phase difference component signals, and each of these outputs is supplied to both input terminals of an adder/subtractor 16 via LPFF1 and F2. In such a way, the multiplication is performed with the amplitude component at a stage where the tracking error signal is produced by the phase difference signal. This prevents the generation of a wrong tracking error signal due to the damage of a disk to be reproduced, the drop-out, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical disc record reproducing apparatus, and particularly to an improvement of a tracking error signal detection section thereof.

[Technical background of the invention and its problems]

2. Description of the Related Art Recently, so-called video disc players, CD (conno 4 disc) players for DAD (De Zotal Audio Disc), and the like have been developed as optical disc record playback devices.

This type of reproducing apparatus requires a focus servo system and a tracking servo system in order to perform the reproducing operation well.

Among these systems, the focus servo system controls the light beam irradiated onto the signal surface of the disk via the objective lens so that it follows the surface wobbling of the disk and always stays within a predetermined depth of focus range.

Further, the tracking servo system controls the above-mentioned light beam so that it can always accurately track a predetermined track by following the eccentricity of the disk.

By the way, in this case, various methods are known for detecting the tracking error signal necessary for the latter tracking servo system, such as a three-beam method and an l-beam method.

Among these, one of the various methods used to detect tracking error signals using the 1-beam method is the so-called phase difference (
There is a method called the time difference) method.

In other words, detection of a tracking error signal using this phase difference (time difference) method is based on the tracking error signal of the phase difference (time difference) that occurs between multiple electrical signals output from a multi-segment photodetector that photoelectrically converts the reflected light from the signal surface. A phase (time) change component that changes depending on the state is detected, and tracking service is performed using this phase (time) change component as a tracking error signal.

However, when tracking error signals are detected using such a phase difference (time difference) method, if the output of the detector is reduced due to disc scratches or dropouts, erroneous tracking error signals may be generated due to noise components. This has a serious drawback in that it may cause so-called mistracking in which correct tracking search cannot be performed.

Further, there is another tracking error signal detection method based on the l-beam method, which is called a heterodyne method.

That is, the tracking error signal is detected by this heterodyne method by sampling the detector output only at the moment of the bit edge in the bit track string forming the signal surface.

However, the tracking error signal detection using such a heterodyne method has a serious drawback in that when the amplitude of the detector output decreases, the open loop of the tracking servo system decreases, and the degree of suppression decreases. had. In this case, the amplitude of the detector output is affected by the disc, information modulation degree, dirt on the disc, detector sensitivity, dirt on the lens, variations in the light source, and the like.

[Purpose of the invention]

Therefore, the present invention has been made in view of the above points, and is designed to prevent the occurrence of false tracking error signals due to disc scratches, dropouts, etc.
An improved optical disc record playback device that can detect tracking error signals that do not adversely affect the tracking servo system due to changes in the amplitude of the detector output, thereby enabling good tracking and king servo. is intended to provide.

[Summary of the invention]

That is, the optical disc-n-code reproducing apparatus according to the present invention irradiates a signal surface of a disc to be reproduced with a light beam, converts the output light from the signal surface into an electric signal, and reproduces the electric signal. A first component that generates a phase difference (time difference) component signal that changes depending on the tracking state from
means, a second means for limiting the amplitude of the phase difference (time difference) component signal from the first means, and a predetermined timing relationship from the phase difference (time difference) component whose amplitude is limited by the second means. and a third means for detecting a phase difference (time difference) signal having a phase difference (time difference) whose amplitude is limited by the second means based on the timing relationship of the phase difference (time difference) signal from the third means. and a fourth means for sampling the amplitude of the time difference) component signal, and the tracking servo is applied to the tracking error signal obtained based on the sampling output from the fourth means. There is.

[Embodiment of the Invention] An embodiment of the invention will be described in detail below with reference to the drawings.

That is, FIG. 1 shows a tracking error signal detection unit applied to a tracking servo system in the f-layer of a CD-based DAD as an example of an optical disc record/playback device, and numeral 11 indicates its pickup (optical system). This is a four-segment photodetector provided in the light receiving section. The four outputs from the four-division photodetector 11 are converted into two phase difference (time difference) component signals by a phase difference (time difference) component signal generation circuit 12, which is composed of two adders, etc., each of which calculates the sum of each diagonal component. It is said that

The two phase difference (time difference) component signals from the phase difference (time difference) component signal generation circuit 12 are directly guided to both input ends of the phase difference (time difference) detector 13, and the first and second are led to the input terminals of each one of the first and second multipliers 14, 15 via amplitude limiters 1θtr and 1θb.

Here, the first and second multipliers 14.15 have their respective other input terminals connected to the phase difference (time difference) detector 1.
By leading the two phase difference (time difference) signals from 3, corresponding multiplication is performed with the above two phase difference (time difference) component signals, and each of these outputs can be adjusted as necessary. Low-pass filter Fr + F2 K
1'' to both input ends of the adder/subtractor 16.

That is, the multiplication in the first and second multipliers 14 and 15 described above substantially uses the timing between the phase difference (time difference) component signals, and from the detector 1 which provides the phase difference (time difference) component signal. The output of the adder/subtractor 16 which completely synthesizes these sampling outputs becomes a tracking error signal.

In this way, at the stage of generating the tracking error signal from the phase difference (time difference) signal, the amplitude component and the multiplication (
By performing sampling, the amplitude information of the detector output is essentially added, which prevents the generation of erroneous tracking error signals due to scratches or dropouts on the disc being played. can.

In addition, since the amplitude of the detector output decreases evenly due to dirt, scratches, dropouts, etc. on the disk surface, it is possible to reduce the amplitude of the mistrack signal and eliminate the influence on the tracking servo system as much as possible. can.

However, as it is, it tends to be affected by changes in the (optical) output from the detector 11, but before sampling, the phase difference (time difference) component signal is transferred to the first and second amplitude limiters 10a.

By limiting the amplitude by 10b, the detector 11
Since we are trying to stabilize the (light) output from the (light)
This has the advantage that it is possible to further improve the stable operation of the above-mentioned tracking servo system by minimizing the effects of changes in output.

FIG. 2 shows a specific example of FIG. 1, in which phase difference (time difference) component signals S1 and S2 are transmitted from the first and second amplitude limiters 10. , l Ob is configured by limiter amplifier 2
The amplitude-limited signal S1d passes through 0a and 20b,
After S2d, the phase difference (time difference) is output as a signal Sc1 + Se2 via comparators 21 and 22.
The first
and first, third, second and fourth switches sw, , sw3 and SW2 . that constitute the second multipliers 14', 15'. It is correspondingly led to each end of SW4.

In this case, the phase difference (time difference) detector 13' is configured to be able to output four phase difference (time difference) signals, φ1, φ2, φ3, and φ4, as described later. The first and fourth switches SWI, SW4 are commonly controlled by outputting the (time difference) signals φ1 and φ2 via the first OR circuit 23.

Further, the remaining two phase difference (time difference) signals φ3 and φ4 are outputted via the second OR circuit 24 to the second and third signals.
switch SW2. SW3 is commonly controlled.

Then, the output vlD from the first and fourth switches SW, SW4 is thereby outputted.

V4D and second and third switch SW2゜SW
The outputs v2D and ■3D from 3 are each added/subtracted by adder/subtractor 16'
The first and second adders 25 and 260 constituting the subtracter 25 and 260 are guided correspondingly to both input terminals, and both outputs of the first and second adders 25 and 26 are guided to both input terminals of the subtracter 27. As a result, only the above-mentioned normal tracking error signal is derived from the output terminal of the X-reducer 27.

Figure 3 shows the phase difference (time difference) detector 13 used in Figure 2.
' This shows a specific example of the controller 21, 2.
S01 from 2. The phase difference (time difference) component signal S02 is passed through four D-type frits 70 horn circuits FF, , FF2
. S01 + Sc2 f are alternately arranged and supplied in the same relationship as the supply to each clock input terminal CK described above. In this case, each flip-flop circuit FFl, FF2 . FF3.
The FFs are supplied with the power supply voltage VCe at their respective input terminals, and the above-mentioned φ1 is supplied from their respective Q output terminals.
, φ2, φ3, and φ4 are derived.

Figure 4 shows the first and second multiplier '4'r15 in Figure 2.
' and a specific example of the adder/subtractor 16'. That is, the first to fourth switches SW1 to SW4 included in the first and second multipliers 14'r15' are respectively field effect transistors FET! ~FET 4 are used, and the first and second adders 25, 26 forming the adder/subtractor 16' are connected to resistors R1, R4 and R2, respectively.
A resistor matrix circuit consisting of R3 is used, and the subtracter 27
As such, an operational amplifier 0P1 (a comparator may also be used) is used.

FIG. 5 shows waveforms of various parts in FIGS. 2, 3, and 4 in the form of a timing chart.

That is, FIG. 5(,) shows the high frequency signal R obtained by adding all four outputs of the four-division photodetector 11.
F (main reproduction signal) is shown for reference, as shown in Figure (b).
, As shown in (c), the phase difference (time difference) component signal Sl
, S2 are given as having a 90° lead or lag relationship with respect to the RF multiplied signal. These phase difference (time difference) component signals s1. s2 are first and second limiter amplifiers 20a, 20, respectively;
By limiting the amplitude at b, Fig. 5(d), (
As shown in e), above a certain level, the signals Sld and Sad become limited and distorted.

5(f) to (1) show four phase difference (time difference) signals φ1, φ2, φ3, and φ4 obtained from the phase difference (time difference) detector 13', respectively. Phase difference (time difference) component signal St of (b) and (c)
, 82 has a variable pulse width corresponding to the whisker-like portions.

Furthermore, the first to fourth stages are shown in FIGS. 5(j) to 5(c).
VID to V4D obtained from switches SW1 to SW4 of
The above variable ! shown in (f) to (g) of the same figure, respectively. 4 phase differences (time differences) with Lux width
Depending on the timing of the signals φl, φ2, φ3, and φ4, the above phase difference (time difference) shown in Figures (b) and (C)
The output is obtained by sampling the output amplitudes of the component signals S1 and S2.

Although not shown, it is obvious that a desired tracking error signal can be obtained by adding these v1 to v4 outputs in the above-described combination and subtracting the added outputs.

It goes without saying that this invention is not limited to the embodiments described above and illustrated, and that the loincloth can be modified and applied without departing from the gist of the invention.

〔Effect of the invention〕

Therefore, as described in detail above, according to the present invention, it is possible to prevent the generation of erroneous tracking error signals due to disc scratches, dropouts, etc., and also to prevent the tracking serve system from being adversely affected by changes in the amplitude of the detector output. Therefore, it is possible to provide an improved optical disc record reproducing apparatus that can detect all tracking error signals and thereby perform good tracking servo.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a configuration explanatory diagram showing a tracking error signal detection section as an embodiment of the optical disc record playback device according to the present invention, and FIG. 2 is a configuration diagram showing a specific example of FIG. 1. The explanatory drawings, FIG. 3, and FIG. 4 are configuration explanatory diagrams each showing a specific example of a part of FIG. 2, and FIG. 5 is a timing chart showing waveforms of each part in FIGS. 2 to 4. 11...4-division photodetector, 12...phase difference (
time difference) component signal generation circuit, 13... phase difference (time difference) detector, 14.15... multiplier, 16... adder/subtractor, 10a, 10b... amplitude limiter. Applicant's agent Patent attorney Takehiko Suzue ('l') -
s

Claims (1)

[Claims] In an optical disc record playback device that irradiates a signal surface of a disc to be played with a light beam, converts the output light from the signal surface into an electrical signal, and plays it back, the hypochondriacal signal changes according to the tracking state. a first means for generating a phase difference (time difference) component signal; a second means for limiting the amplitude of the phase difference (time difference) component signal from the first means; a third means for detecting all phase difference (time difference) signals having a predetermined timing relationship from the phase difference (time difference) component signals; and based on the timing relationship of the phase difference (time difference) signals from the third means. and fourth means for sampling the amplitude of the phase difference (time difference) signal whose amplitude has been limited by the second means, and the tracking servo is controlled by a tracking error signal obtained based on the sampling output by the fourth means. What is claimed is: 1. An optical disc record playback device characterized in that the device is configured to play.