JPH0352668B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a tracking servo control device for a video disc player.

Conventional general video disc players require highly accurate tracking servo, regardless of whether the system is optical or capacitive.

<Prior Art> Therefore, in conventional video disk players, a tracking servo control device as shown in FIG. 1 is usually used. That is, in FIG. 1, 1 is a disk, 2 is a pickup device including a needle 2a, 3 is a gain control amplifier, 4 is a tracking error detection circuit, 5 is a phase compensation circuit, and 6 is a needle drive circuit including a tracking drive coil 6a. A tracking servo loop is formed by these.

In this case, a tracking signal is recorded in advance on each track of the disk along with video information, and when a predetermined track on the disk surface is scanned by the pick-up device 2 in playback mode, the tracking signal is picked up and played back along with the video information. , here, in particular, only the tracking signal from the pickup device 2 is sent to the gain control amplifier 3.
The tracking error signal is supplied to the tracking error detection circuit 4 via the tracking error detection circuit 4, where the tracking error signal is detected.
The tracking error signal thus detected is supplied to the needle drive circuit 6 via the phase compensation circuit 5, and the drive coil 6a controls the tracking of the needle 2a on a predetermined track.

<Problems to be Solved by the Invention> In the conventional tracking servo control device as described above, the loop gain of the servo loop is set to an appropriate value by the gain control amplifier 3. There are considerable variations in the characteristics of the disk 1 and the pick-up needle 2a, and since the disks in particular are replaced on a daily basis, there have been cases where the margins of the servo system alone cannot sufficiently compensate. Furthermore, even when the same disc is played back, the loop gain varies between the inner and outer circumferences of the disc, and no countermeasures have been taken for such gain variations.

<Means for Solving the Problems> In order to solve the above problems, the present invention provides a tracking servo control device for a video disc player, which includes a reference signal generating means for generating a reference signal having a specific frequency; addition means for adding and mixing the reference signal generated by the generation means into the servo loop during the vertical blanking period; extraction means for extracting the reference signal mixed in by the addition means from the servo loop; and extraction by the extraction means. and gain control means for detecting the magnitude of the detected reference signal and controlling the loop gain of the servo loop based on the detected output.

<Function> According to the present invention, it is possible to deal with variations in characteristics between the inner and outer circumferences of the disk, and it is possible to keep the tracking servo loop gain constant at all times.

<Example> The present invention will be described below according to an example shown in the drawings. FIG. 2 shows one embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In particular, an adder circuit 7 is inserted between the tracking error detection circuit 4 and the phase compensation circuit 5 in the tracking servo loop, and the error detection signal obtained from the tracking error detection circuit 4 in the servo loop is added to the error detection signal obtained from the tracking error detection circuit 4 in the servo loop at a predetermined timing. The reference signal generated by the reference signal generator 8 is added and mixed as a disturbance.

On the other hand, the reference signal mixed into the tracking servo loop is extracted from the input side of the adder circuit 7 via the bandpass filter 9, and this reference signal is added to the detection and amplification circuit 10 to be detected and amplified, and then held. Supply to circuit 1. The hold circuit 11 always holds the value at that time, and controls the gain of the gain control amplifier 3 based on this value.

Here, for example, a vertical flanking signal is generated from the timing signal generator 12,
As a result, the switch 13 is temporarily turned on, and the reference signal generated by the reference signal generator 8 during this vertical blanking period is added and mixed into the tracking servo loop. At the same time, the vertical blanking signal is also supplied to the hold circuit 11, and the hold value in the hold circuit 11 is updated each time.

As described above, by automatically resetting the gain of the gain control amplifier 3 in the servo loop every vertical blanking period, the loop gain of the servo loop can be maintained at all times regardless of variations in characteristics between the inner and outer circumferences of the disk 1. can be kept constant.

<Effects of the Invention> According to the tracking servo control device of the present invention, a reference signal of a specific frequency is added and mixed into the servo loop during the vertical blanking period as described above, and this mixed reference signal is added into the servo loop. Since the loop gain in the servo loop is automatically corrected each time based on this reference signal, the loop gain of the tracking servo loop is always adjusted regardless of variations in characteristics between the inner and outer circumferences of the disk. It is possible to keep it constant.

Further, in the present invention, since the reference signal is added and mixed into the servo loop during the vertical blanking period, there is no fear that this reference signal will become a disturbance and adversely affect the image.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional tracking servo control device, and FIG. 2 is a block diagram of an embodiment of the present invention. 1...Disk, 2...Pickup device, 3
... Gain control amplifier, 4 ... Tracking error detection circuit, 5 ... Phase compensation circuit, 6 ... Needle drive circuit, 7 ... Addition circuit, 8 ... Reference signal generator,
9... Band pass filter, 10... Detection amplifier circuit, 11... Hold circuit, 12... Timing signal generator.

Claims (1)

[Claims] 1. In a tracking servo system of a video disc player, there is provided a reference signal generating means for generating a reference signal having a specific frequency, and a reference signal generated by the generating means during a vertical blanking period. Adding means for adding and mixing into the servo loop; Extracting means for extracting the reference signal mixed in by the adding means from the servo loop; Detecting the magnitude of the reference signal extracted by the extracting means, and outputting this detection output. A tracking servo control device comprising: gain control means for controlling the loop gain of the servo loop based on the following: A tracking servo control device, characterized in that the tracking servo loop gain is always kept constant.