JPH0728624Y2 - Tracking controller - Google Patents

Description

The present invention relates to a tracking control device for a video disc player.

(Prior Art) In a conventional video disc player, normally,
A tracking controller as shown is used. That is, in the figure, a is a disk-shaped recording medium (hereinafter simply referred to as a disk), b is a pickup circuit including a pickup sensor c, d is a gain control amplifier circuit (AGC circuit), e is a tracking signal error detection circuit, and f is Phase compensation circuit, g is a tracking drive circuit, h is a tracking signal detection circuit, i is a tracking signal detection circuit, j
Is a balance adjustment circuit for the tracking signal detection level, and these circuits form a tracking servo loop.

A tracking signal is recorded in advance on each track of the disk a together with video information. Now, when the pickup circuit b scans a predetermined track on the disk surface in the reproduction mode, the tracking signal is picked up and reproduced together with the video information. Here, in particular, only the tracking signal is transferred from the pickup circuit b to the gain control amplifier circuit d,
It is supplied to the tracking signal error detection circuit e through the tracking signal detection circuit h and the tracking signal detection circuit i, where the tracking error signal is detected.
As for the tracking error signal, two types of tracking signals recorded on both ends of the track are detected by the tracking signal detection circuit h, and are detected by the tracking signal detection circuit i at the next stage, and then the tracking signal error detection circuit e is detected.
Obtained as the output of. The tracking error signal thus detected is supplied to the tracking drive circuit g through the phase compensation circuit f, and the drive coil 1 controls the tracking so that the pickup sensor c scans a predetermined track position.

In this case, since the characteristics of the tracking signal detection circuit h and the tracking signal detection circuit i do not always match, the balance adjustment circuit j manually adjusts the balance of both circuits h and i.

(Problems to be Solved by the Invention) By the way, it is ideal that the recording levels of the above-mentioned two types of tracking signals are always the same. However, in practice, this recording level varies greatly depending on the disc. Therefore, even if the characteristics of the tracking signal detection circuit h are initially matched by the balance adjustment circuit j, the conventional tracking control device cannot cope with such variations in the disc itself.

(Means for Solving Problems) The tracking control device of the present invention includes a holding means for holding an average value of detection levels of two types of tracking signals detected from a recording medium for a predetermined time, and Detecting means for detecting the difference between the signal levels obtained by the holding means, and the balance of the detecting levels so as to eliminate malfunction due to the level difference at the time of recording of the two types of tracking signals by the signal level difference detected by the detecting means. And a balance adjusting means for adjusting.

(Operation) The holding means holds the average value of the detection levels of the two types of tracking signals detected from the recording medium for a predetermined time. Here, the predetermined time is a certain long time which is not affected by the tracking control. In other words, the tracking control controls the tracking sensor so that the tracking deviation is always eliminated by instantaneously following the pickup sensor according to the detection level difference between the tracking signals. , The average level should converge to the level when there is almost no tracking error. Therefore, when taking the average of the predetermined time,
Only the recording level difference of each tracking signal at the time of recording is obtained as the difference of the average value level without being affected by the tracking error.

The detecting means detects the difference between the average value levels held by the holding means in this way. The detected level difference is converted into a signal suitable for balance adjustment by the balance adjusting means, and the balance of the detection levels of the two types of tracking signals is adjusted by the converted signal. That is, the adjustment is made so as to eliminate the level difference during recording.

As a result, it is possible to eliminate the variations in the recording levels of the two types of tracking signals due to the variations in the recording medium itself, so that the tracking control is not affected by the variations in the recording levels.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of the tracking control device of the present invention.

In the figure, 1 is a disc, 2 is a pickup circuit including a pickup sensor 3, and 4 is a gain control amplifier circuit (AG
C circuit), 5 is a tracking signal error detection circuit, 6 is a phase compensation circuit, 7 is a tracking drive circuit, 8a and 8b are tracking signal detection circuits, 9a and 9b are tracking signal detection circuits, and 10 is a balance adjustment circuit. Since these are the same as the conventional tracking control device described above, details thereof will be omitted here.

In the present invention, in addition to the above circuits, a hold circuit 20
a, 20b and a differential amplifier circuit 21 are added.

Next, the operation of the tracking control device having the above configuration will be described.

When the pickup circuit 2 scans a predetermined track on the disk 1 in the reproduction mode, the pickup circuit 2 reproduces the two types of tracking signals recorded together with the video information on the disk 1. The two reproduced tracking signals are properly amplified by the gain control amplifier circuit 4, and then the tracking signal detection circuit
Two types of tracking signals are individually detected by 8a and 8b, further detected individually by tracking signal detection circuits 9a and 9b, and input to the tracking signal error detection circuit 5 and hold circuits 20a and 20b, respectively.

Each of the hold circuits 20a and 20b holds the average value of the detection level of each tracking signal for a predetermined time, and inputs the average value to the differential amplifier circuit 21. Here, the predetermined time is a certain long time which is not affected by the tracking control. That is, since the tracking control is a control for constantly eliminating the tracking deviation by instantaneously following the pickup sensor 3 according to the detection level difference of the tracking signal, the tracking control was observed in a certain long time. In that case, the average level should converge to the level when there is almost no tracking error. Therefore, when the average of the predetermined time is taken, it is not affected by the tracking error, and only the recording level difference of each tracking signal at the time of recording is obtained as the difference of the average value level.

The differential amplifier circuit 21 detects the difference between the average levels of the two types of tracking signals obtained by the hold circuits 20a and 20b in the preceding stage, and inputs it to the balance adjustment circuit 10. The balance adjustment circuit 10 converts the difference between the average levels of the tracking signals into a signal suitable for balance adjustment, inputs the converted balance adjustment signals to the tracking signal detection circuits 8a and 8b, and outputs the two types of tracking signals. Controls the balance of detection levels.

In this way, the control for eliminating the malfunction due to the level difference at the time of recording the two types of tracking signals is performed, so that the tracking signal error detection circuit 5 is affected by the recording level difference (recording level imbalance). Instead, it is possible to detect the tracking error signal indicating the actual tracking deviation. The detected tracking error signal is supplied to the tracking drive circuit 7 via the phase compensation circuit 6, and the drive coil 11 performs tracking control so that the pickup sensor 3 scans the track accurately.

(Effect of the Invention) As described above, according to the tracking control device of the present invention, the balance of the detection levels of the two types of tracking signals can be automatically controlled, so that the tracking signal detection circuit and the tracking signal detection circuit Not only the imbalance but also the imbalance of the recording level of the tracking signal recorded on the recording medium can be automatically adjusted.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a tracking control device of the present invention, and FIG. 2 is a schematic block diagram of a conventional tracking control device. 1 ... Disc (recording medium) 2 ... Pickup circuit 4 ... Gain control amplification circuit 5 ... Tracking signal error detection circuit 6 ... Phase compensation circuit 7 ... Tracking drive circuit 8a, 8b ... Tracking signal detection circuit 9a , 9b …… Tracking signal detection circuit 10 …… Balance adjustment circuit 20a, 20b …… Hold circuit 21 …… Differential amplifier circuit

Claims (1)

[Scope of utility model registration request] 1. A holding means for holding an average value of detection levels of two types of tracking signals detected from a recording medium, and a difference between signal levels obtained by the holding means. And a balance adjusting unit for adjusting the balance of the detection levels so as to eliminate the malfunction due to the level difference at the time of recording of the two types of tracking signals due to the signal level difference detected by the detecting unit. And tracking control device.