JPS6038747A - Abnormality detector for signal detector - Google Patents

Abstract

PURPOSE:To detect accurately the abnormality of a signal detector with a simple constitution and to apply this detector to an ordinary reproducer and to accelerate effectively the removal of an unrequired signal being introduced, by detecting the abnormality of the signal detector such as introduction of an unrequired signal by using the signal of a drop-out detector. CONSTITUTION:The signal detected by a drop-out detector 11 is integrated by an integrator 12, and the time difference of the integrated signal is converted into a DC component. This voltage is decided by a comparator 13. Thus the abnormality of a signal detector such as the introduction of an unrequired signal, etc. can be detected. In this case, the time constant of the integrator 12 is selected properly. As a result, this detector has no response to the drop-outs which arise irregularly with a comparatively short time duration and responds only to a fault of the signal detector. In such a way, the signal of the detector 11 is used to detect accurately the abnormality of a signal detector such as the introduction of an unrequired signal, etc. with a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an abnormality detection device for detecting an abnormality in a signal detector such as a big-up in a reproducing apparatus that reproduces signals from a record carrier such as a disk. .

Conventional configurations and their problems In general, in a system in which a disc is played back using a contact type pick amplifier such as a stylus, if dust or other foreign matter gets on the stylus tip, it will affect the playback signal and cause serious problems. This will degrade the signal. Furthermore, dirt and the like attached to the tip of the needle are rarely removed naturally during playback, and once they are present, they continue to degrade the playback signal.

This problem will be explained regarding video disc players. Of course, it is obvious that the same applies to other magnetic reproducing devices.

Now, in some types of video disc players, the eye structure is
Regeneration (ij'
>i and a tunneling signal is detected. If this happens, dust may accumulate on the signal detector, and in that case, not only the video and audio signals but also control signals such as tracking will be significantly interfered with. This is extremely inconvenient as it can cause damage to the chime. In contrast, the needle tip has a special shape that makes it difficult for dirt to stick, and if it does occur, we have taken measures to detect dirt and remove it as quickly as possible. It may be equipped with equipment.

For example, when dust is detected, the detection signal is used to control the stylus pressure to be higher than normal, which solves this problem and is effective.

In this case, if the stylus tip has dust on it (
It plays an important role to reliably detect abnormalities in the signal detector).

This conventional method for detecting abnormalities such as dirt will be explained with reference to FIG.

The signal detected by the signal detector 1 is sent to the signal processing circuit 5 after being detected by a second detector. At this time, in order to keep the detected signal amplitude constant, an automatic gain control circuit (A
GO circuit) f::, may be configured by adding it in the middle. In this case, the signal amplitude is detected by the envelope detector No. 4, and the voltage control amplifier No. 3 (v
c) is controlled to keep the amplitude of the detected signal constant. The control signal VS at this time is used to detect abnormalities in the signal detector. Specifically, the control signal VS is detected when the amount of variation in the control signal V, which is obtained by detecting the envelope of the signal, has a certain value. In this case, it is determined that an abnormality has occurred in the signal detector and the lateral pressure control circuit is controlled. That is, the control signal vs is smoothed by a diode 6 and a capacitor 7 with a time constant that is sufficiently larger than the response time constant of the AGO circuit, and then the negative level shift circuit 8 smoothes the voltage -v71! A comparator 9 compares the voltages of Vs and VC, and the difference between VS and the smoothed voltage vcO is determined as Vl.
When this occurs, it is determined that there is an abnormality in the signal detector, and the rotation control circuit 10 is operated. For example, as shown in Figure 2a, if an abnormality occurs in the detector due to dust, the level of the input signal will decrease over a long period of time, so the control signal V
s changes significantly. On the other hand, V.

Since the time constant is large, it changes slowly, and when VC>Vs, the comparator 9 is turned on and the stylus force control circuit 10 is operated. In this way, abnormalities such as dust on the signal detector are detected.

However, in the conventional method, the circuit is complicated, there are many elements for determining when an abnormality occurs, and the setting thereof is not easy. Furthermore, it requires an automatic gain control circuit, and it has the disadvantage that it is difficult to take measures without an automatic gain control circuit.

OBJECTS OF THE INVENTION The present invention eliminates the drawbacks of the prior art, and provides a detection device that accurately detects abnormalities in a detector with a simple configuration.

Composition of the Invention The signal detector abnormality detection device of the present invention uses a signal called a dropout detection signal to detect when a signal from a disk or tape is missing, and detects an abnormality in the signal detector. Since the dropout detection signal and the abnormality of the signal detector are closely related, it can accurately and effectively detect the abnormality of the No. 17i detector and promptly detect the problem due to dust buildup etc. This leads to the cancellation of signal deterioration.

DESCRIPTION OF EMBODIMENTS An abnormality detection device according to an embodiment of the present invention will be described below with reference to the drawings. In general, a drop-out compensation circuit is essential for players that play discs.

This is because the pressed disc has defects due to impurities in the sample, defects in the stamper, dust on the surface of the disc, etc., resulting in signal defects and signal loss. In this case, the signal loss is detected and the compensation device is operated. As the detection method, there are known methods such as one that utilizes a change in the input RF multiplied signal envelope and one that detects a change in phase. As shown in Fig. 3, there may be only a few detected signals in one horizontal scanning section (hereinafter referred to as 1H section), and the missing 18 signals are generally 17zS.
They range from 60 or less to several H, but they are characterized by occurring irregularly and not lasting for a long time.

On the other hand, the drop-out detector also operates when an abnormal phenomenon other than a disk defect occurs, such as dust on the stylus tip of the signal detector.

This dust build-up phenomenon is a phenomenon in which when dust adheres to the signal detector, an abnormal drop in the output signal continues until the dust is removed naturally, and is determined as a type of signal loss. Moreover, the dust attached to the signal detector is difficult to remove naturally, and the duration of the abnormal output signal's low output signal is short, unlike in the case of a dropout, as shown in Figure 4. However, it can range from a few frames to a few seconds or more. Therefore, there is a clear difference between when a dropout is detected and when there is an abnormality in the signal detector.

Therefore, the present invention aims to generate a big signal using the signal of a dropout detector, which is an essential circuit for video signal playback equipment.
It detects abnormalities in signal detectors such as amplifiers and heads, and an example of the determination means is as shown in FIG. The voltage is integrated, the time difference is converted into a DC component, and the voltage is determined by the comparator 13, making it possible to easily detect abnormalities in the signal detector such as dust. In this case, by appropriately selecting the time constant of the integrator 12, it is possible to stably detect only abnormalities in the signal detector without responding to dropouts that occur irregularly and have a relatively short duration. FIG. 6 shows another embodiment of the invention. In the embodiment shown in the figure, when there is an abnormality in the signal detector, the pulse width of the output signal of the dropout detector 11 becomes clearly wider than when there is a dropout. The signal is input to the signal detector, and pulses with a constant width are detected as abnormalities in the signal detector. This allows us to detect dropouts from any number of months.
The present invention is capable of stably detecting abnormal conditions in a signal detector.The present invention has the advantage of being able to stably detect abnormal conditions in a signal detector. By detecting abnormalities in the signal detector, accurate detection can be performed with a simple configuration, and
Conventionally, detection thresholds can be easily set, and most playback devices are equipped with a dropout detector.

The present invention can be easily applied to recycling equipment, and can effectively promote removal of dust removal, making it extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional abnormality detection device, Fig. 2 is a diagram showing internal signal changes in the conventional example, and Fig. 3 is a schematic diagram of an example of a dropout detection signal at the time of dropout. FIG. 4 is a diagram schematically showing an example of a dropout detection signal when an abnormality occurs in a signal detector, and FIGS. Zubu
Figure 112 shows 11...Dropout detector, 12...A(
1 [divider, 13... comparator, 14...
Reference voltage 1 upper source, 15...Pulse width judger. Name of agent: Patent attorney Toshio Nakao Haga 1st person
1 Figure 1 Figure 3 Figure I, = 4 Figure 1F ward bar ε15 Figure 6

Claims (3)

[Claims] (1) An abnormality detection device for a signal detector, characterized in that an abnormality in the signal detector is detected based on a signal that detects a lack of a reproduced signal. (2) An abnormality in the signal detector is detected by integrating a signal in which a missing reproduction signal is detected and comparing the integrated signal with a reference voltage. Abnormality detection device for signal detector. (3) The apparatus for detecting abnormality in a signal detector according to claim 1, wherein abnormality in the signal detector is detected based on the response width of the signal in which the missing reproduction signal is detected.