JPS6247284A - Tracking signal reproducing circuit - Google Patents

Abstract

PURPOSE:To perform surely tracking control and to prevent the time lag of tracking by taking out a tracking signal and an index signal set to a frequency of odd number times a horizontal scanning frequency fH/2 by a comb line filter. CONSTITUTION:Tracking signals fp1, fp2 and an index signal fp3 separated by a low pass filter 4 are supplied to a comb line filter consisting of an 1H delay circuit 71, an inverter 72, and an adder 73. Then, from the filter 7, only a signal component of odd number times fH is taken out. The tracking signals fp1, fp2, and the index signal fp3 are supplied to a tracking control circuit 8 to be a tracking error signal according to a tracking state of a sensor 2. This tracking signal is supplied to a tracking coil 2a of the sensor 2, and displaces the sensor to a tracking direction to perform a tracking control.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a racking signal reproducing circuit, which reproduces an index signal set to a frequency that is an odd multiple of 1/2 of the horizontal scanning frequency (hereinafter referred to as fH). Regarding the resulting circuit.

A conventional technical information signal is recorded in a spiral, and two types of tracking signals fPI with different frequencies are placed on the left and right sides.

The tracking signal fPI is obtained by recording fρ2 at a position i in synchronization with the horizontal synchronization signal by switching it left and right every rotation.

There is a video disc (information signal recording medium) on which an index signal fP3 for switching the switch is recorded at the replacement position of fP2. These 1 ~ racking signals fPI, fP2
, each frequency of the index signal fP3 is f +−+
= 15.73426 kl-I Z, then r
p + -(65/2)・1゛I(Yu511.3635
kl-(Zf p 2= (91/2) ・f'
+1: 715.9088 kl-1zf P
3 - (:35/2) φ f H nigo 275
．． It is set to an odd multiple of 1/2 of fH, such as 3496 kHz.

When playing back this video disc, two types of playback] - The racking signals fPI and fP2 are switched every rotation by the index signal fP3 and supplied to each detection circuit, and the racking signals 1 to fP+ are output from each detection circuit. , f
A tracking error signal corresponding to the level difference of p2 is taken out, and based on this tracking error signal, a sensor 4 such as a playback button is tracking-controlled so as to correctly track the information signal track.

Problems to be Solved by the Invention The output of the circuit that takes out the reproduced tracking signal f'pl, 1'p2 and the index signal fP3 may contain noise components due to a number of reasons, and as a result, the reproduction tracking signal becomes There is a problem in that the SN ratio becomes poor, 1-ranking control cannot be performed accurately, and tracking deviation may occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tracking signal reproducing circuit that can extract a reproduced tracking signal with a high signal-to-noise ratio.

In the diagram of means for solving the problem, the comb filter 7 is an example of means for extracting signals of odd multiples of fH.

A tracking signal fp+ and an fp2 index signal fP3 set to a frequency that is an odd multiple of f z /2 are extracted by a working comb filter 7 .

Embodiment The figure shows an embodiment of the circuit of the present invention in a video disc brake A7.
A block system diagram applied to the system is shown. At d3 in the figure, the signal reproduced by a sensor such as the reproduction button 2 from the video disc 1 on which the above-mentioned information signal and the racking signals fp+, fp2, and index signal fP3 are recorded is sent to the reproduction circuit 3 as an RF multiplied signal. 1 to racking signals f'pl, fp2, and index signal fp3 are divided by a low-pass filter 4 of 1M l-1y, while an information signal valve N(
The information signal is divided and FM demodulated in the circuit 5, and processed in the signal processing circuit 6 to be converted into a video signal and an audio signal.

I ~ racking signal fp divided by low-pass filter 4
+, fp2, index trust? 'if P 3 is 1
1” Chikanobu circuit 7+, inverter 72. The signal is supplied to a comb filter 7 constituted by an adder 73, where only signal components that are odd multiples of fH are extracted.

As mentioned above, since the tracking signals fρI, fP2, and index signal fP3 are set to an odd multiple of 1/2 of I'H, they are divided by the comb filter 7 and taken out, and the Signal components and noise components that are even multiples of 1/2 are not extracted.

In this case, the tracking signal f is output from the comb filter 7.
In addition to P+', fP2, and index signal fP3, fH
Noise components that are odd multiples of 1/2 are also extracted, but the total noise component is 1/2 of the conventional one, so
i ~ racking signals f'pl, f'p with high SN ratio
2, the index signal rp3 can be taken out.

1 to racking signal f taken out from the comb filter 7
P+, fP2, and index signal fP3 are supplied to the tracking control circuit 8, and are supplied as a tracking error signal according to the tracking state of the sensor 2 to the tracking coil 2a of the sensor 2, which displaces the sensor 2 in the tracking direction and performs tracking. Control.

Note that the frequencies of the tracking signals fPI, fP2 and index signal fP3 may be set to odd multiples of f'H.

Effects of the Invention According to the circuit of the present invention, since a comb filter is provided, the reproduction 1 to racking signals set to a frequency that is an odd multiple of 1/2 of l'z (or fl-1) are It has features such as being able to obtain a good S/N ratio, being able to perform tracking control reliably, and not causing tracking deviation.

[Brief explanation of the drawing]

The figure shows an embodiment of the circuit of the present invention.
It is a block system diagram applied to. 1...Video disc, 2...Playback needle (sensor)
, 4...Low pass filter, 7...Comb filter, 8
...Tracking control circuit. Patent applicant: Victor Japan Co., Ltd. -6=

Claims (1)

[Claims] The reproduced tracking signal reproduced from the information signal recording medium and set to a frequency that is an odd multiple of 1/2 of the horizontal scanning frequency (or the horizontal scanning frequency) in order to cause the sensor to correctly trace the information signal track is passed through a comb filter. A tracking signal reproducing circuit characterized in that the tracking signal reproducing circuit is configured to output the tracking signal through the.