JPS62180544A - Video disk player - Google Patents

Abstract

PURPOSE:To make a stable reproducing operation possible by increasing high frequency current injected to a sensor electrode when the sticking of foreign substance is detected by the lowering of the level of reproduction output. CONSTITUTION:When foreign substance 17 is interposed in a sensor 2 and a disk 1, the distance between an electrode 14 and the disk 1 is made larger and high frequency current becomes difficult to conduct, and the level of a detection signal from a detector 3 becomes low. A level detector 7 detects the lowering of the signal level and sends an increase signal to a power control circuit 26. The power control circuit 26 raises voltage applied to a high frequency oscillator 27 based on the increasing signal. Accordingly, the oscillation output of the high frequency oscillator 27 is increased, and high frequency current injected to a central conductor 18 through an input antenna 19 is increased, and the high high frequency current is given to a sensor electrode 14 connected to the central conductor 18. Thus, the high frequency current is conducted sufficiently and the lowering of signal detection level is prevented even when the foreign substance is interposed in the sensor 2 and disk 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a capacitive video disc player such as a VHD video disc player.

Conventional technology In a capacitive video disc player, a needle equipped with an electrode (hereinafter referred to as a sensor) slides into contact with the disc in order to detect information from the rotating disc, which is an information recording medium. Information is detected as a change in capacitance.A unique problem with such a contact type reproduction method is that foreign matter such as dust attached to the disk surface and sensor may have an adverse effect on stable signal reproduction. As a means to improve this problem, for example,
As shown in the publication, a method has been proposed for increasing the sliding pressure between a sensor and a disk in a cleaning device for a reproducing needle and an information recording medium.

Hereinafter, a cleaning method for the conventional disc player as described above will be explained with reference to the drawings.

FIG. 6 shows a principle diagram of a conventional cleaning device.

In FIG. 6, reference numeral 1 denotes an information recording medium (disk) made of a conductive material, which rotates in the direction of the arrow.

A sensor 2 has electrodes formed on a diamond base material, and detects information by changing capacitance with the electrodes while sliding on the surface of the disk 1. 3 is a detector which converts the capacitance change obtained from the sensor 2 into an electric signal, and is a cavity resonator and a high frequency oscillator.

It consists of a detection circuit, etc. 4 is a head amplifier that amplifies the weak reproduction signal from the detector 3.

A signal processing circuit 5 converts the reproduced signal into a signal suitable for each terminal device (for example, a television 6). 7 is a level detector that compares increases and decreases in the signal level from the sensor 2 and sends an activation signal to the next stage when the signal level decreases. Reference numeral 8 denotes a needle pressure increasing circuit, which increases the voltage supplied to the needle pressure coil drive circuit 9 in response to an activation signal from the level detector 7. The needle pressure coil drive circuit 9 is a drive circuit for the needle pressure coil 1o, and power amplifies the signal from the needle pressure increasing circuit 8. 1° is a stylus force coil that converts the drive current into magnetism, and 011 is a cantilever that supports the sensor 2. A magnet 12 applies pressure (stylus pressure) for the sliding contact between the sensor 2 and the disk 1 by a repulsive force with the magnetic flux from the stylus pressure coil 10. 13 is a cantilever support rubber that supports the cantilever 11.

FIG. 7 is an enlarged side view of the sliding state between the sensor 2 and the disk 1, and shows an example of a state in which foreign matter is attached.

The sensor 2 is composed of an electrode 14 and a diamond base material 15. 16 is a signal bit formed on the surface of the disk 1 as information. A foreign substance 17 is attached to the surface of the disk 1 and the sensor 2.

The operation of the cleaning device configured as described above will be described below. First, when a foreign object 17 shown in FIG. 7 is interposed between the sensor 2 and the disk 1, the distance between the signal bit 16 on the surface of the disk 1 and the electrode 14 increases, and the capacitance change due to the unevenness of the signal bit is reduced.

Next, when the capacitance change decreases, the conversion level of the detector 3 into an electrical signal decreases. The signal is then amplified by the head amplifier 4 and input to the level detector 7. Level detector 7
detects a drop in the signal level and sends an activation signal to the needle pressure increase circuit 8. The zero-order needle pressure increase circuit 8 supplies a needle pressure coil drive circuit 9 with a needle pressure increase voltage. Thereby, the needle pressure coil drive circuit 9 increases the needle pressure coil current. When the current of the needle pressure coil 10 increases, the repulsive force with the magnet 12 increases,
The sliding pressure between the sensor 2 and the disk 1 increases,
The foreign matter 17 interposed between the sensor 2 and the disk 1 is pushed out, and signal detection returns to a normal state.

Problems to be Solved by the Invention However, this phenomenon of adhesion of foreign matter 17 can also result in the attachment of strong foreign matter, and the above-mentioned conventional method has not been able to provide a sufficient effect in such cases. .

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a video disc player that can maintain stable playback operation even when a strong foreign object is attached to the video disc player.

Means for Solving the Problem In order to achieve this object, the video disc player of the present invention increases the high frequency current injected into the sensor electrode when the presence of a foreign object is detected by a decrease in the level of the playback output. The apparatus is configured to include means for enhancing the reproducing operation in such a manner that the reproducing operation is enhanced.

According to the present invention, by increasing the high-frequency current injected into the sensor electrode when foreign matter is attached, the high-frequency current between the sensor electrode and the disk is prevented from decreasing due to the attachment of foreign matter, and stable reproduction operation is achieved. It will come true.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a principle diagram of a signal detection and compensation section of a video disc player in an embodiment of the present invention. 1
is a disk, 2 is a sensor, 3 is a detector, 4 is a head amplifier, 6 is a signal processing circuit, 6 is a television, 8 is a needle pressure increasing circuit, 9 is a needle pressure coil drive, 1o is a needle pressure coil, 11
12 is a cantilever, 12 is a magnet, and 13 is a cantilever support rubber, which is the same as the configuration of the conventional example shown in FIG. It is electrically connected to the electrode 14 of the sensor 2 by a wire. Reference numeral 19 denotes an input antenna that injects high-frequency carriers into the center conductor 18. 20 is an output antenna, and a zero diode 21. The resistor R22 and the capacitor C123 constitute a detection circuit, which detects the AM modulated wave of the high frequency carrier due to the capacitance change from the sensor 2, and converts it into an electric signal corresponding to the capacitance change. 24 is a feedback capacitor C2, and a high frequency current flows from the center conductor 18 via the sensor electrode and the disk 1, and falls to the ground through the feedback capacitor 24.

25 is a stray capacitance C3, which connects the center conductor 18 to the L component of the lead wire of the sensor 2 to create a resonator (its resonant frequency is fo
). The electrical signal from detector 3 is
The signal is input to head amplifier 4. A level detector 7 detects a decrease in the signal amplitude level from the head amplifier 4. 2
A power control circuit 6 increases the oscillation output of the high frequency oscillator 27 based on a signal from the level detector 7. In this example, the voltage applied to the oscillator 27 is controlled. 27 is a high frequency oscillator, and in a VHD video disc player, the oscillation frequency is 10110l3.
I am using sc.

FIG. 2 shows the resonance characteristics of the cavity resonator, and compares when the oscillator output is increased and when it is in normal operation. The operation of a signal detection and compensation circuit for a video disc player configured such that the horizontal axis represents frequency and the vertical axis represents DC detection voltage will be described below.

First, as shown in FIG. 7, when a foreign object 17 is present between the sensor 2 and the disk 1, the distance between the electrode 14 and the disk 1 increases, making it difficult for high-frequency current to flow. The level becomes smaller. When the signal level decreases, the level detector 7 detects the decrease in the signal level and sends an increase signal to the power control circuit 26. The power control circuit 26 increases the voltage applied to the high frequency oscillator 27 based on the increase signal. This increases the oscillation output of the high frequency oscillator 2T, increases the high frequency current injected into the center conductor 18 through the input antenna 19, and provides the high frequency current to the sensor electrode 14 connected to the center conductor 18. Therefore, even if a foreign object 17 is present between the sensor 2 and the disk 1, a sufficient high frequency current flows to prevent the signal detection level from decreasing.

FIG. 2 shows the resonance characteristics of the cavity resonator when the output of the oscillator 27 is increased and during normal operation, and the detected DC voltage increases by increasing the output of the oscillator. The high frequency induced voltage of the output antenna 20 is proportional to the high frequency current flowing through the center conductor 18, and therefore the high frequency current flowing to the sensor electrode also increases.

As described above, according to this embodiment, even if a strong foreign object exists between the sensor 2 and the disk, the signal detection level can be prevented from decreasing and stable reproduction can be performed.

Next, other embodiments of the present invention will be described with reference to the drawings.

FIG. 3 shows another means of increasing the high frequency current injected into the electrode 14 of the sensor 2, which increases the resonant frequency f of the cavity resonator. The oscillation frequency f. It can be obtained by bringing it closer to SC.

FIG. 4 shows the detected DC voltage when the oscillation output and the resonance frequency 10 are changed simultaneously. With this method, the amount of high frequency waves injected into the sensor electrode 14 can be effectively increased.

Figure 6 shows the oscillation output and resonance frequency f. Change sensor 2
A principle diagram of increasing the amount of radio frequency injected into the electrode 14 of FIG. 18 is a center conductor, 19 is an input antenna, 20 is an output antenna, 21 is a detection diode, 22 is a rectifier resistor R1
23 is a rectifier capacitor C1, and 21, 22, and 23 constitute a detection circuit. 26 is a stray capacitance C3, 26 is a variable capacitance diode whose capacitance changes depending on the voltage, and the resonant frequency f0 of the cavity resonator changes. 27 is f. High frequency coupling is performed with the center conductor 18 using a variable antenna. 28 is a capacitor C connected to the variable capacitance diode 26, and 29 is f. The operation of the signal detection and compensation means for a video disc player configured as 0 or more, which is a voltage generator for changing the resonant frequency fo by a control circuit, will be described below. First, when a foreign object is present between the sensor 2 and the disk 1, the detection sensitivity of the detector 3 decreases. Then, the level detector 7 detects the level drop and sends the f0 control signal to the f□ control circuit 29. The f0 control circuit 29 increases the voltage applied to the variable capacitance diode 26 to change the resonant frequency f0 of the resonator to the oscillation frequency fo.
Close to 8 degrees. On the other hand, the output of the high frequency oscillator 27 is increased by the signal from the level detector 7, and the input antenna 1
9 into the center conductor 18.

As described above, as shown in FIG. 4, by increasing the detected DC voltage and increasing the amount of high-frequency current injected into the sensor electrode 14,
It is possible to prevent a decrease in output due to foreign matter getting caught.

As described above, according to this embodiment, the sensor 2 and the disk 1
By increasing the high frequency current injected into the sensor 2, it is possible to prevent the level of the reproduced signal from decreasing and achieve a more stable reproduction operation.

Note that although the present embodiment does not specifically explain the use in combination with the increased pressure, it goes without saying that the effects can be further exhibited by combining the increased pressure and the means of the present invention.

Effects of the Invention As described above, according to the present invention, the potential of the sensor electrode is increased by detecting a drop in the level of the output reproduction signal when foreign matter is attached to the disk and increasing the high-frequency current injected into the sensor. It is possible to prevent the high frequency current between the sensor electrode and the disk from decreasing even when foreign matter is attached.
This makes it possible to eliminate unstable conditions such as the needle and the playback screen being disturbed due to adhesion of foreign matter.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram of a video disc player according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing its operating principle, and Fig. 3 is a characteristic diagram showing the principle of operation thereof.
Fig. 4 is a characteristic diagram showing the operating principle of another embodiment of the present invention, Fig. 5 is a main part configuration diagram showing another embodiment of the present invention, and Fig. 6 shows a conventional cleaning device. The circuit diagram and FIG. 7 are enlarged views of main parts showing the state of adhesion of foreign matter. 1...disc, 2...sensor, 3.
...Detector, 4...Head amplifier,
7... Level detector, 14... Electrode,
26... Power control circuit, 27...
... High frequency oscillator, 18 ... Center conductor, 19
...Input antenna, 2o...Output antenna, 21...Detection diode, 22...
・-R rectifier resistor, 23... Rectifier capacitor C1
, 24... Feedback capacitance C2, 25... Stray capacitance C3, 26... Variable capacitance diode, 2
7...f0 variable antenna, 29...f
0 control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 6 TV Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A sensor for reproducing a signal from a capacitive video disc, means for detecting a drop in the level of the reproduced signal, and injecting into an electrode of the sensor in response to a detection signal indicating a drop in the signal level of the drop detecting means. and means for increasing high frequency current.