JPH0531233B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a disk-shaped information recording carrier (hereinafter referred to as a disk) on which information signals including periodic synchronization signals are recorded concentrically or spirally. The present invention relates to a reproducing device that reproduces an information signal using a reproducing needle that is in contact with the disc, and is particularly characterized by a control means that controls the pressing force between the reproducing needle and the disk.

Conventional configuration and its problems In a reproducing device that reproduces information recorded by a reproducing needle that slides into contact with a disk on which an information signal is recorded, in particular, a reproducing needle equipped with an electrode is used to record information on a conductive disk surface. In the method of reading the change in the unevenness as a change in capacitance, it is necessary that the disk surface and the electrode surface of the reproduction needle are always in close contact with each other. However, if foreign matter such as dust in the air adheres to the signal surface of the disk or the electrode surface of the reproducing needle, the signal recorded on the disk surface cannot be detected as a normal capacitance change. It disappears. Therefore, when reproducing information signals, we remove foreign objects between the signal surface of the disk and the sliding surface of the reproducing needle.
Patent Application No. 56-154311 and No. 57-145011 aimed at realizing stable signal detection while having the effect of simultaneously cleaning both the regenerated needle slide contact surface and the signal surface of the disk. is proposed. 1st
The figure shows the conventional basic configuration. Normally, playback of a capacitive disk is performed in the following manner. First, the unevenness on the disk surface is read as a change in capacitance between the reproducing needle 7 and the electrode sliding surface, and the detector 6 converts it into a constant signal level.
It becomes an RF signal in the head amplifier 1. This RF
The signal is converted into a video signal and an audio signal by a signal processing circuit 5, and the video and audio signals are reproduced by a display means 3 consisting of a video tube, a speaker, and the like. If a foreign object exists between the sliding contact surface of the reproducing needle electrode and the disk surface, the RF output signal level of the head amplifier 1 decreases depending on the degree of the foreign object. Therefore, when the RF signal level decreases by the stylus force supplement circuit 4,
To generate a signal that increases the contact force (stylus pressure) between the playback needle and the disk, input that signal to the stylus pressure application circuit 8, increase the stylus pressure, eliminate foreign matter, and realize stable playback. circuit has been proposed. The stylus pressure regulation circuit 5 is a circuit that generates a signal for applying stylus pressure during normal reproduction.

In the above method, the stylus force is controlled by the output level of the RF signal, but the problem is that highly accurate control cannot be expected because the output level of the RF signal is detected by methods such as envelope detection. There is.

In other words, since the stylus pressure between the playback stylus and the disk is controlled by the relative level change of the envelope-detected RF output signal, for example, even if the S/N of the video signal decreases, the noise component increases. By doing so,
The output level of the envelope-detected RF signal may not decrease. In this case, there was a drawback that the desired stylus pressure that should be applied was not applied. Also,
Even if the output level of the RF signal decreases, the S/N ratio of the video signal may not decrease, and in this case, unnecessary stylus pressure is applied, which shortens the life of the reproduction stylus. As described above, the stylus force control using the envelope-detected RF output signal has the problem that an appropriate oblique force is not applied.

OBJECTS OF THE INVENTION The present invention aims to solve the above-mentioned conventional problems, and aims to stably and accurately control the pressure contact force between the regeneration needle and the disk.

Composition of the Invention The present invention extracts a reproduced signal from a reproduced signal output from a signal processing circuit only during a synchronization signal period periodically included in the signal, and extracts noise components contained in the extracted signal. It detects the magnitude of the amplitude and controls the pressing force between the playback needle and the disk based on it.

DESCRIPTION OF THE EMBODIMENT FIG. 2 shows an embodiment of the control device of the present invention. In FIG. 2, block diagrams designated by the same reference numerals as in FIG. 1 have the same functions as in FIG. 1. The feature of this embodiment lies in the difference between the stylus force supplement circuit 4 shown in FIG. 1 and the stylus force supplement circuit 9 shown in FIG.
In Figure 1, the head amplifier 1 is
Detects the amplitude of the RF signal output from the
When the RF signal amplitude becomes small, a signal is generated to increase the stylus pressure between the playback stylus and the disk. In FIG. A supplementary stylus force signal is generated from the stylus pressure signal that controls the stylus force between the regenerated needle and the disk. FIG. 3 shows a specific example of a configuration for generating a stylus pressure supplementary signal. Using the reproduced horizontal synchronization signal 11 from the video reproduction signal 10 outputted from the signal processing circuit 2, the reproduction signal is transmitted to the gate circuit 1 only during the synchronization signal period.
Remove by 2. The extracted signal contains noise components and is detected by the detection circuit 13.
The voltage is amplified to an appropriate voltage by the amplifier circuit 14. In this case, a signal appears that is proportional to the amplitude of the noise component of the extracted signal. The amplified signal is held by the level hold circuit 15 for 1H. The level hold circuit 15 is simply constituted by a charging/discharging circuit made of CR, with a small charging time constant and a large discharging time constant, and holds the amplified output signal level. The output signal from the level hold circuit 15 is voltage-compared with a reference voltage 18 in a voltage comparison circuit 16 . The differential voltage signal 17 between the two becomes an application signal for supplementing the stylus pressure applied to the stylus pressure applying circuit 88 in FIG. That is, when the level-held signal becomes smaller than the reference voltage, the applied voltage is applied to supplement the stylus pressure by the voltage difference, and the stylus pressure is increased and controlled to become equal to the reference voltage.

Effects of the Invention The conventional control method for applying stylus pressure uses a signal obtained by envelope detection of the RF signal output from the head amplifier, so there is a problem in that the stylus pressure between the playback needle and the disk is controlled only with respect to relative changes. However, the present invention extracts the noise component of the signal during the synchronization signal period of the information signal after passing through the signal processing circuit, focuses on the magnitude of the amplitude of the noise component, and uses the detected and amplified signal. Since it generates an applied signal that changes the stylus pressure, that is, by changing the stylus pressure level according to the S/N of the information signal, unnecessary stylus pressure is not applied and stable accuracy is achieved. High stylus force control can be expected.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional stylus pressure control device that controls the pressure contact force between a regenerating stylus and a disk;
The figure is a block diagram showing a stylus force control device according to an embodiment of the present invention, and FIG. 3 is a concrete block diagram of the main parts thereof. 1...Head amplifier, 2...Signal processing circuit, 6
...Detector, 7...Regeneration needle, 8...Stylus pressure application circuit, 9...Stylus pressure supplementary circuit, 12...Gate circuit,
13...Detection circuit, 14...Amplifier, 15...Level hold circuit, 16...Comparator.

Claims (1)

[Claims] 1. A reproducing needle that reproduces information by slidingly contacting a rotationally driven information recording carrier extracts information signals from sequentially reproduced information signals only during synchronization signal periods periodically included in the reproduced signals, and extracts the information signals. detects the noise components contained in the detected signal,
A stylus pressure control device, characterized in that the pressure contact force between the reproduction stylus and the information recording carrier is controlled according to the level of the noise component.