JPS631176A - Video disk player - Google Patents

Abstract

PURPOSE:To obtain an excellent reproducing signal without disturbing the synchronizing signal by providing a track jump mechanism and giving a signal corresponding to a jump period to a dropout compensation circuit. CONSTITUTION:The Q output of a monostable multivibrator 15 and a Q output of a monostable multivibrator 16 are fed to an OR circuit 21 by the command signal of a track jump from a system control circuit 14. Further, an OR circuit 22 is provided to the output side of a dropout detection circuit 5 and an OR output from an OR circuit 21 is fed to the OR circuit 22 to change over a switch 6. A reproducing signal is replaced during the period into an output signal at one preceding horizontal period and an output signal without noise is extracted to eliminate the noise during the track jump period. Thus, the excellent signal reproduction is applied with a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video disc player, such as an optical type.

[Summary of the invention]

The present invention relates to a video disc player, in which a track jump mechanism is provided and a signal corresponding to the jump period is supplied to a dropout compensation circuit, thereby making it possible to obtain a good reproduction signal without synchronization signal disturbance. It is something.

[Conventional technology]

In video disc players, especially optical devices, the playback head can easily be moved between tracks.
Special playback such as still image playback, slow playback, and quick playback using so-called track jumps can be easily performed.

That is, in FIG. 7, (100) is a track on the disk, and photodetectors (1a) to (1a) facing this track (100) are used to detect the reflected light of the light beam.
1d) and <le) (lfl) are provided.These photodetectors (1a) to (1f) constitute a so-called reproducing head.The explanation of the photodetectors (1a) to (1d) will be omitted. is divided into four parts for the purpose of so-called focus serve.

The signals from the photodetectors (1a) to (1d) are sent to the adder (
2) and then sent to the demodulator (
4) and a dropout detection circuit (5) K are supplied.

In this detection circuit (5), for example, a retriggerable monostable martenobulator (mono-multi) having an inversion time slightly longer than the longest wavelength of a high-frequency signal by an FM signal is provided, and when the inversion of this mono-multi is released, a drop occurs. out is detected.

In addition, the signal from the demodulator (4) is supplied to the - fixed contact of the switch (6), and the output of this switch (6) is transmitted to the other fixed contact of the switch (6) through the delay circuit (power) of one horizontal period. Furthermore, the above-mentioned dropout detection signal is supplied to the control terminal of the switch (6), and the switch (6) is switched to the other fixed contact side during the period when the dropout is being detected.

Accordingly, the reproduced signal is replaced with an output signal from one horizontal period earlier during the dropout detection period, and dropout compensation is performed. Furthermore, this dropout compensated signal is passed through the time base correction circuit (8) to the output terminal (9).
is output to.

The signal from the photodetector (le) (If) is also fed to the difference circuit On, forming a signal corresponding to (and direction of) the tracking error. This error signal is supplied to the tracking coil 03 through an adder (111 and drive amplifier 0z), and tracking serge is performed in the direction in which this error signal becomes zero.

Furthermore, in this device, a track jump command signal (nosorus) from the system control circuit α is supplied to the first monostable multifunction generator α, and the Q output of this monostable multifunction α9 is supplied to the second monostable multifunction generator α9. This monomulti α9
The Q output of the monomulti C1e and the Q output of the monomulti C1e are added by an adder αη and supplied to the above-mentioned adder (111).

Therefore, in this device, the system control circuit α
When a command signal for a track jump is output from the side, the monomulti σ9 is first inverted and a jump/elus as shown in FIG. 8A is generated. When this pulse ends, the monomultiple σe is subsequently reversed, and a brake pulse as shown in FIG. 1B is generated. Further, these signals are added in an adder αη to produce a signal as shown in C in the same figure, and this signal is added in an adder αV to an error signal that is changed as shown in the figure from the difference circuit α1. and is supplied to the tracking coil α3.

As a result, the tracking coil 131 is accelerated at the time when the no-yump noise is first generated, and tracking is forced in a desired direction. Next, the coil 031 is decelerated by the brake A and stopped at a desired track position. In this way, a track jump is performed. For this reason, the above-mentioned inversion time of the mono multi-track α9 is set to be the time required for the reproducing head to reach the middle of the desired track, and the inversion time of the mono multi-track αG is also set to be equal to this.

Furthermore, even if the track jump is not performed completely accurately, the desired track will be tracked by the subsequent tracking search.

In this way, a track jump is performed, and the so-called angular velocity -
If a fixed disc is being played back (for example, by jumping in the IJ/A direction once every revolution of the disc, still images can be played back, and it is possible to play back a still image by jumping in the forward direction. K allows quick playback at double speed.

In this case, when a track jump is performed, the level of the reproduced signal decreases during the jump period as shown by E in the waveform diagram above, and when this level falls below the detection limit shown in the diagram, the signal is demodulated. A large level of noise occurs in the signal as shown in F in the same figure. Therefore, when viewing images by inputting this reproduced signal to a television receiver, the operation of the system control circuit I is adjusted so that the above-mentioned track jump is performed within the so-called vertical blanking period. Noise was prevented from appearing on the playback screen, so that an apparently good playback image could be obtained.

However, when trying to input this reproduced signal to a device that processes in synchronization with the vertical synchronization signal, such as a special effects generator or chromakey device, the above-mentioned noise causes the synchronization separation circuit to malfunction, causing various troubles. It turns out that there is a risk.

Note that when a dropout compensation circuit is provided as described above, the circuit operates to perform compensation when the level of the reproduced signal decreases. However, the detection limit of the dropout compensation circuit is generally set to an extremely low level that makes the image unrecognizable, so noise occurs before the compensation circuit works, and the vertical synchronization separation circuit of the subsequent device is There was a great risk that it would malfunction.

[Problem that the invention seeks to solve]

As described above, the conventional technology has the problem that the synchronization separation circuit of the subsequent device malfunctions due to the noise during track jumps, and the processing of the subsequent device cannot be carried out satisfactorily.

Means for Solving Problem C] The present invention detects dropouts in reproduced signals (circuit (
5)) During this detection period, replace the above playback signal with the playback signal of the circuit (force) before a predetermined horizontal period (switch (6))
In a video disc player having a dropout compensation circuit configured to perform compensation using a command signal (circuit I
) is provided with a track jump mechanism (multivibrator Q5, (18, drive amplifier (13, tracking filter α3)) that jumps to a track different from the track that is normally reproduced continuously, and In the video disc player, a signal corresponding to the track jump period formed (OR circuit (2D)) is added (OR circuit @) to the dropout detection signal and the resultant signal is supplied to the dropout compensation circuit.

[Effect]

According to this, since the position of a drop in signal level caused by a track jump is estimated in advance and compensated for, it is possible to reproduce a good signal with a relatively simple configuration.

〔Example〕

In FIG. 1, the Q output of the monomulti α9 and the Q output of the monomulti+161 of the devices described in the prior art described above are supplied to a newly provided OR circuit C11. Further, an OR circuit is provided on the output side of the dropout detection circuit (5), and the OR output from the above-mentioned OR circuit is supplied to this OR circuit. This OR output switches SIN≠(6).

Therefore, in this device, when noise occurs during the jump period as shown in FIG. 2A-F, the OR circuit 1211 outputs a Q output of Figure A) and the Q output of the monomulti a61 (Figure B
During this signal period, the reproduced signal is replaced with an output signal from one horizontal period before, and a noise-free output signal is obtained as shown in H in the figure.

In this way, the noise during the track jump period is removed. According to the above-mentioned device, a signal including the noise period is formed from the track jump command signal from the system control circuit I, and this signal is used to detect dropout. The signal is added to the signal and replaced with the signal, and a good output signal can be obtained with an extremely simple configuration.

Note that since a track jump is normally performed in the equalization node part during the vertical blanking period, the waveform of the signal one horizontal period ago is exactly the same, and therefore, as mentioned above, the entire track jump period is No problem will occur even if the signal is replaced with a signal from one horizontal period ago.

Furthermore, FIG. 3 shows a case where only the predicted noise period is replaced instead of the entire jump period mentioned above, and in this example, the track jump command signal from the system control circuit 0 is replaced as shown in FIG. As shown in the figure, the signal is supplied to the monomulti 3, which has a reciprocating inversion time just before the noise period, and the Q output of this mono multiplier has an inversion time slightly longer than the length of the noise period, as shown in BK of the same figure. The Q output of this monomulti Q4 is supplied to the OR circuit (2).

Therefore, in this device, the signal of the noise period is replaced with the signal of one horizontal period before, and a noise-free signal is extracted as shown in FIG.

By the way, in the above-mentioned apparatus, the switching from the track jump signal to the brake/# signal may be performed by detecting the zero cross point of the tracking error signal. In this case, the detection of the zero cross point is prohibited for a predetermined period after the jump command signal because the error signal is at a low level and there is a risk of malfunction.

Therefore, if such an inhibit pulse is obtained, the noise during the jive period can also be removed as follows.

That is, in FIG. 5, the terminal Gυ to which the pulse is supplied to the above-mentioned prohibited node is connected to one end of the capacitor 3a, and the other end of this capacitor C33 is connected to the power supply terminal (b) through the diode. The resistor ω is connected to the power supply terminal (to) through a series circuit, and the voltage dividing point of this resistor (to) is connected to the pace of the pnp transistor t3η. The emitter of this transistor 61 is connected to the power supply terminal (2).

Also, the terminal Q to which the above-mentioned dropout detection signal is supplied
is connected to one input of a NAND circuit (40) through a resistor 131, and the collector of the transistor 61 is connected to one input of this NAND circuit t4G and a resistor C39.
Connected to the midpoint of the connection. Furthermore, a terminal to which a signal that is at a low level during a period during which dropout compensation is not desired, such as a frame number period of a reproduced signal, is supplied is connected to the other input of the output circuit. The output of this NAND circuit (4(I) is connected to the control terminal of the switch (6).

Therefore, in this device, when detecting the zero cross point of an error signal as shown in FIG.
The inhibit/# pulse supplied to υ is as shown in BK in the same figure, and thereby the potential at the other end of the capacitor 62 is changed as shown in C in the same figure. And transistor 07
) becomes K as shown in the figure, and the noise period signal is replaced as shown in the figure F with respect to the reproduced signal shown in the figure E.

In this manner, also in this device, by exchanging the signals during the noise period, it is possible to obtain a good reproduced signal without affecting subsequent devices, etc. In this case, only six new component elements are provided: the capacitor 32, the diode G9, the resistor G9, and the transistor 13D, which can be realized with an extremely simple configuration.

〔Effect of the invention〕

According to this invention, the position of the drop in signal level caused by a track jump is estimated in advance and compensated for, making it possible to reproduce a good signal with an extremely simple configuration. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of the present invention, FIGS. 2 to 6 are diagrams for explaining the same, and FIGS. 7 and 8 are diagrams for explaining the conventional technology. (100) is a track, (la) ~ (lfl is a photodetector, (2) αυαη is an adder, f3) Q[) 03 is an amplifier, (4) is a demodulator, (5) is a dropout detection circuit, (6) is a switch, (7) is a delay circuit, (8) is a time axis correction circuit, (9) is an output terminal, [3 is a tracking coil, Q4) is a system control circuit, n5c
e is a monostable multi-nobbler, and CI'll is an OR circuit.

Claims (1)

[Scope of Claims] A video disc player having a dropout compensation circuit that detects a dropout in a playback signal and compensates by replacing the playback signal with a playback signal from a predetermined horizontal period earlier during the detection period. , a track jump mechanism is provided which jumps to a track different from the track that is normally and continuously reproduced in accordance with the command signal, and a signal corresponding to the track jump period formed from the command signal is transmitted to the track jump period. A video disc player which adds the signal to the dropout detection signal and supplies the signal to the dropout compensation circuit.