JPS6352349A - Stylus float detecting method - Google Patents

Abstract

PURPOSE:To accurately detect the contacting state between a disk and a repro ducing stylus and to detect the float of the stylus by subtracting only a disk surface wavy component from the low frequency component of a reproduced signal indicated the disk surface wavy component and the stylus contacting state. CONSTITUTION:A resonance line 16 is coupled to a disk 1 by a floating capacity to form a resonance circuit. This floating capacity is varied only by surface waviness of the disk 1, and only the surface wavy component is outputted to the output terminal 12 of a detecting circuit 17. This signal is delayed in a delay circuit 15 by only a time corresponding to the difference between a reproducing stylus 2 and the attaching position of the resonance line 16, and the rotational frequency (fundamental wave) component of the disk 1 has the amplitude adjusted by a variable amplifier 14 and is applied to the other input terminal of a subtractor 11, thereby taking out only the contacting state between the reproducing stylus 2 and the disk 1 to the output terminal 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for detecting the state of contact between a playback stylus and a disc in a D-type video disc player or the like.

2. Description of the Related Art In recent years, video disc players have become widespread. Among them, in the contact type vHD method, detecting the contact state between the playback needle and the disc is
This is extremely important when considering the application of damage reduction to the disk and correction of fluctuations in the detection signal F characteristics. Conventionally, the detection means for this purpose has been to detect and rectify the envelope of the detection signal.

Problems to be Solved by the Invention However, with this conventional method, if there is a level difference between the upper and lower individual band waves, the envelope will fluctuate depending on the video signal, and the phenomenon caused by the moldability of the disc and the playback needle. There have been problems, such as the fact that it is impossible to separate the phenomena caused by the contact state of the disks.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a stylus floating detection method that can detect only the state of contact between a playback stylus and a disc.

Means for Solving the Problem In order to achieve this object, the stylus floating detection method of the present invention detects the surface runout component of the disk in a non-contact manner, and detects the low frequency component in the playback signal detected by the playback stylus. The needle lift is detected by subtraction. Also,
At this time, the rotational speed component of the disk is canceled out.

Effect With this configuration, only the contact state between the disk and the needle can be detected by subtracting only the disk surface runout component from the low frequency component of the reproduction signal, which includes the disk surface runout component and the contact state of the needle. will be possible.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the needle floating detection method according to the present invention. In Fig. 1, 1 is a disk;
2 is a regeneration needle, 3 is a fly lead 14 is a resonant line, 5 is an oscillator, 6 is a detection circuit, 7 is a bypass filter (HPF)
, s is an FM demodulator, 9 is a video output terminal, 10 is a low pass filter (LPF), 11 is a subtracter, 12 is an output terminal,
13 is a rectifier, 14 is a variable amplifier circuit, 15 is a delay circuit,
16 is a resonant circuit, 1 is a detection circuit, and 18 is an amplifier.

FIG. 2a shows the resonant line 49 oscillator 5 of FIG. Detection circuit 6
C is the output waveform of the detection circuit 6, and FIG. 2 is the transfer characteristic of the oscillator 5. of FIG. Resonant line 16. The transfer characteristic of the detection circuit 1, d is the output waveform of the detection circuit 1, and e is the output waveform at the output terminal 12 in FIG.

Now, the recorded information signal on the disk 1 is picked up by the reproducing needle 2, guided to the resonant line 4 through the fly lead 3, and forms a co-grinding circuit with a resonant frequency fR. In addition, a frequency f with a slope of the resonant circuit from the oscillator 5 is given. Inject the oscillation output of At this time, depending on the bit of disk 1, f
Due to the minute fluctuations in the signal 8, an output signal corresponding to the recording signal of the disk 1 is outputted from the detection circuits. This signal is input to the 7M demodulator 8 through the amplifier 18 and the HPF terminal, and a video demodulated signal is obtained at the video signal output terminal 9.

On the other hand, when the disk 1 has surface runout, the resonant frequency fR varies depending on the state of contact between the reproducing needle 2 and the disk 1. Furthermore, even when the playback needle 2 follows the surface runout of the disk 1, the resonant frequency fR fluctuates due to the deflection of the fly lead 3. That is, signals indicating the surface runout of one disk and the contact state of the reproduction stylus and recorded information are outputted to the output terminal of the detection circuit 6. Among them, the recorded information is removed by LPFlQ, and only low frequency components are input to the subtracter 11.

The resonant line 16 is coupled to the disk 1 through stray capacitance to form a resonant circuit at one resonant frequency f8 (FIG. 2b). This stray capacitance varies only due to the surface runout of the disk 1, and only the surface runout component is output from the output terminal 12 of the detection circuit 1 (FIG. 2d). When attaching the reproducing needle 2 and the resonant line 16, this signal is delayed by a delay circuit 15 by a time corresponding to the difference in position, and the component of the rotational frequency (fundamental wave) of the disk 1 is adjusted by a variable amplifier 14. By applying the voltage to the other input terminal of the subtracter 11, only the contact state between the reproducing needle 2 and the disc 1 can be taken out to the output terminal 12 (second
Figure e).

The rectifier 13 takes out the rotational frequency component of the disk 1,
This component is used to cancel the surface runout component by controlling the variable amplifier 14.

As described above, according to this embodiment, the state of contact between the disc and the playback stylus can be detected by subtracting the low frequency component of the output of the playback stylus from the output of the non-contact surface runout detection circuit. In this case, it is necessary that the coupling between the oscillator 15 and the resonant lines 4 and 16 be loosely coupled so that they do not affect each other, or that the oscillator 15 be stable against load fluctuations. It's not a vessel.

Note that if this level is a problem, the same effect can be obtained by using an optical (photocoupler) detection means for the surface runout detection means.

Effects of the Invention As described above, according to the present invention, the contact state between the disc and the playback stylus can be accurately detected by subtracting the low frequency component of the playback stylus output from the non-contact surface runout detection means. Can detect needle lift. This can be used to correct the frequency characteristics of the reproduced signal depending on the contact state and as a detection signal for the stylus skipping phenomenon that causes damage to the disc, and its practical effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a circuit implementing a needle floating detection method in an embodiment of the present invention, and FIG. 2 is a waveform diagram of each part thereof. 1...disc, 2...playback needle, 3...
...Fly lead, 4...Resonance line, 5...
Oscillator, 6...Detection circuit, 7...HPF
, 8...FM demodulator, 9...-video signal output end, 1o...LPF, 11...subtractor,
12... Output end, 13... Rectifier, 1
4...variable amplifier circuit, 15...delay circuit,
16...Resonance circuit, 17...Detection circuit,
18...Amplifier.

Claims (2)

[Claims] (1) An information recording disk that is driven to rotate, a playback needle that contacts the recording disk and picks up the recorded information, a first detection means that detects the recorded information as a change in capacity, and a surface of the recording disk. and a second detection means for detecting a shake component in a non-contact state, and the recording disk and the A method for detecting needle floating, characterized in that the amount of variation in the gap between the regenerated needle and the needle is detected. (2) The subtraction of the output of the first detection means and the output of the second detection means is performed in such a way as to cancel out the fundamental component of the rotational drive frequency of the recording disk. Needle floating detection method described in section.