JPS61264522A - Tracking controller - Google Patents

Abstract

PURPOSE:To obtain a tracking controller which eliminates harmful track deviation and the occurrence of noise to trace tracks faithfully, by providing filters having such frequency characteristic that the amplitude level of a detection signal having an optical frequency characteristic is made fixed. CONSTITUTION:Filters 12 and 13 have a frequency characteristic (b) shown in the figure with respect to a detection signal (a) having the optical frequency characteristic. That is, when the primary high pass filter having the frequency characteristic opposite to that of the detection signal (a) is used, the frequency characteristic of the filter output is made flat to reduce the difference of amplitude level. Thus, the generation of an unnecessary tracking error signal is suppressed, and an actuator 8 is not unnecessarily driven, and tracks are traced faithfully without track deviation neither the occurrence of noise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a tracking control device for photoelectric compact disc (CD) players, video display players, etc., and particularly to a tracking control device for faithfully tracking tracks on a disc.

[Background of the invention]

Conventionally, as a tracking method used in an optical disc playback device, a pair of photoelectric converters that photoelectrically convert the amount of light reflected from a track and their outputs are used, as described in Japanese Patent Laid-Open No. 51-8818, for example. It is equipped with a pair of band amplifiers that respectively pass and amplify only the frequency components of recorded information from the signal, and a pair of envelope line detectors that detect the respective envelopes of the output signal waveforms of the band amplifiers. A track error signal detection method (hereinafter referred to as AM detection method) is known in which an error signal corresponding to the amount of track deviation is obtained by comparing the outputs of the detectors.

In principle, this AM detection method allows only the signal components recorded on the disc to pass through the band amplifier, and attenuates low frequency components that are harmful to tracking due to scratches unrelated to the signal components. Therefore, it is possible to prevent the optical pickup from following the scratches by deviating from the original track, and the trackability of the scratches is excellent.

However, since the detected signal components have optical frequency characteristics as shown in a&c in Figure 1 and have different amplitude levels, the pair of tracking detection light beams overlaps the signal train as shown in Figure 2, resulting in a slope. If the detected signals have a time difference, an unnecessary signal is detected as a tracking error signal. As a result, the acquisition unit is driven unnecessarily, resulting in deterioration of trackability and generation of noise, but this point was not taken into account in the above-mentioned Japanese Patent Laid-Open No. 51-8818.

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tracking control device that eliminates the above-mentioned drawbacks, avoids harmful track deviations and generates noise, and faithfully tracks a track.

[Summary of the invention]

To achieve the above object, the present invention suppresses the occurrence of unnecessary tracking error No. 1 through a filter having frequency characteristics that cancels out the amplitude level difference between a pair of detected tracking signals in the signal frequency band. It is characterized by being capable of faithful tracking.

[Embodiments of the invention]

FIG. 3 shows a tracking control device according to the present invention, in which 3 is an optical disk, 4 is a disk motor, 5 is an optical pickup, and 6 is an AM
This tracking error detection circuit includes a light receiving element 9 for photoelectrically converting the amount of light reflected from the track, a pair of current-voltage converters 10 and 11 for converting the output current of each light receiving element into voltage, and Filters 12 and 15 correct the amplitude level difference of the frequency component of the disc recording information output from the current-voltage converter, and a pair of band amplifiers 14 and 15 that pass only the frequency component of the disc recording information from the respective filter outputs. and a pair of envelope detectors 16 and 17 for detecting the envelopes of the output signal waveforms of these band amplifiers, respectively, and an error amplifier 18 for comparing the outputs of these envelope detectors.

Further, 7 is a driving amplifier, and 8 is a tracking actuator for driving the signal track of the pickup 3t disk.

In this embodiment, the filters 12 and 13 have frequency characteristics as shown in b of FIG. 1 for a detection signal having an optical frequency characteristic as shown in C of FIG. When using the first-order bypass filter shown in Fig. 4, which has a frequency characteristic of , the frequency characteristic of the filter output becomes flat,
The amplitude level difference is reduced. Therefore, generation of unnecessary tracking error signals can be suppressed, and one actuator 8 will not be driven unnecessarily, so that the track can be faithfully tracked without track deviation or noise.

5. In this embodiment, an example is shown in which the first-order bypass filters shown in FIG. 4 are used as the filters 12 and 13, but this is not particularly limited. On the other hand, it is sufficient if the frequency characteristics of the detection signal are flattened after passing through the filter.

〔Effect of the invention〕

As described above, according to the present invention, the amplitude level of a pair of track detection signals can be increased by passing a detection signal having optical frequency characteristics through a filter having a frequency characteristic such that the amplitude level N is constant. Since the difference is eliminated, unnecessary tracking error error No. 1g is no longer generated, track deviation and noise can be reduced, and the track can be faithfully tracked.

[Brief explanation of drawings]

Figure 1 is an optical frequency characteristic diagram of the track detection signal, Figure 2 is an optical frequency characteristic diagram of the track detection signal.
The figures show different positional relationships between the track and the three beams, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a diagram showing a specific example of the filter circuit shown in FIG. 12.13... Disc optical frequency characteristic correction filter ◎ Yu2 Otsu Q 811 loss (Kl-IZ)

Claims (1)

[Claims] A pair of light receiving elements corresponding to the radial direction of the disk, a photoelectric converter that photoelectrically converts reflected light corresponding to each of the light receiving elements, and an output having optical frequency characteristics of each light receiving element of the photoelectric converter. A pair of band amplifiers each passing and amplifying only the signal component of information recorded on the disk from the signal, a pair of envelope detectors each detecting the envelope of the output signal of the band amplifier, and the envelope detector. a comparator for comparing the outputs of the discs, and the output of the comparator obtains a drive signal for a track scanning drive device for driving an objective lens that projects a light beam from a light source onto the disc along an information recording track of the disc. In a disk device constructed as follows,
A correction circuit is provided in the path of the photoelectric converter to bring an output signal having an optical frequency characteristic of each light receiving element closer to a flat frequency characteristic, and the correction circuit suppresses the generation of unnecessary signals in the output of the comparator. A tracking control device that reduces track deviation from the information recording signal track of the disk and reduces noise generated due to unnecessary driving of the track scanning drive device.