JPH0718057Y2 - Video disc player - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a video disc reproducing apparatus, and particularly when the disc motor is started, the disc motor is driven at a predetermined starting voltage at first, and the number of revolutions of the disc reaches a predetermined range. By the way, the present invention relates to a video disc reproducing apparatus which switches to rotation control based on a synchronizing signal in a reproduced composite video signal and thereafter synchronizes the reproduced video signal.

[Conventional technology]

Video signals including sync signals (vertical and horizontal) are pit-recorded by FM modulation on the disc to be played on the video disc playback device. The playback device side reads the disc recording signal with an optical pickup and performs FM demodulation. Obtain the composite video signal, output it to the TV device and play the screen.

Here, even if the synchronization signal is recorded on the disc, if the rotation speed of the disc is not appropriate, the reproduction frequency of the synchronization signal itself will deviate from the frequency set by the TV device side, and the reproduction screen will be defective. Invite.

For this reason, conventionally, a video disc reproducing device is provided with a rotation control device for a disc motor,
The synchronizing signal in the reproduced composite video signal can maintain a predetermined frequency.

Specifically, as shown in FIG. 2, the disk 10 on which the video signal is pit-recorded by the FM modulation is the disk motor 12 during reproduction.
Is rotated by. Optical pickup from spinning disk 10
The detection signal read in 14 is amplified by the RF amplifier 16,
Further, after the video band is taken out by the BPF 17, the FM video is detected by the FM video detector 18 and returned to the analog composite video signal.

While this composite video signal is output to the TV device side, it is first sent to the sync separation circuit 20 in the playback device to extract the horizontal sync signal, and the phase / frequency comparator 22 uses the reference signal generator.
The phase / frequency comparison between the output of 24 and the horizontal synchronizing signal is performed, and the difference signal is sent to the compensating circuit 26 for phase compensation and the like, and then the compensating signal is amplified by the amplifier 28, and the switching SW30
Is output to the motor drive circuit 32 via
12 rotation controls are performed.

As a result, the rotation speed of the disk 10 is controlled so that the frequency of the horizontal synchronizing signal in the composite video signal matches the frequency of the reference signal.

By the way, when the disk motor 12 is started, since the composite video signal cannot be reproduced, the rotation control described above does not work, and the normal reproduction cannot be performed forever.

Therefore, while the rotation speed of the disk 10 reaches a predetermined rotation range from zero, the input of the switch SW30 is switched to the starting voltage generator 34 side, and a constant voltage is applied to the motor drive circuit 32 to change the rotation speed. Is trying to get up.

That is, the rotation detector 38 provided on the table 36 on which the disk 10 is placed generates a pulse having a frequency proportional to the rotation speed,
This pulse is converted into a voltage proportional to the rotation speed by the FV converter 40, and then it is compared by the comparator 42 with the reference voltage corresponding to the predetermined rotation speed output from the reference voltage generator 44. Switch the switching signal from the comparator 42 when the reference voltage is exceeded.
It is output to 30, the switching from the starting voltage generator 34 side to the amplifier 28 side, the rotation speed of the disk 10 reaches a predetermined rotation range,
After the rotation control system can function normally, the rotation control is applied.

Of course, in the tracking control unit 48 that controls the tracking coil 46 of the optical pickup 14 and the focusing control unit 52 that controls the focus coil 50, the switching SW 30 is the amplifier 28.
The control is closed before it is switched to the side.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technique, the rotation number of the disk 10 is detected by the rotation detector 38 provided in the table 36 to generate a pulse proportional to the rotation number, and this pulse is applied to the voltage. Since it is converted to, the magnet and Hall element, or
Since a mechanical rotation detecting mechanism including a slit and a photo coupler is required, the cost of parts is high and there is a disadvantage in cost.

In view of the problems of the prior art, this invention makes it possible to electrically detect that the number of rotations of a disk has reached a predetermined rotation range, eliminates the need for a mechanical rotation detection mechanism, and achieves cost reduction. It is an object of the present invention to provide a video disc reproducing apparatus capable of performing the above.

[Means for solving problems]

In this invention, a motor drive unit that drives a disc motor, a rotation control unit that controls the motor drive unit based on a synchronization signal in a composite video signal detected from the disc, and keeps the period of the synchronization signal constant, The starting voltage generator that generates the voltage for starting the disk motor and the switching operation are performed according to the switching signal. At the time of starting, the output of the starting voltage generator drives the motor until the number of rotations of the disk reaches a predetermined range. In addition to the section, in a video disk reproducing apparatus having a switching section for adding the output of the rotation control section to the motor drive section after the number of rotations of the disk reaches a predetermined range, in the output of the video signal demodulation section, A noise detection unit that detects the nozzle level and the noise level detected by this noise detection unit are compared with a predetermined value, and when the noise level falls below a predetermined value, a switching signal is output to the switching unit. It is characterized by comprising a switching control unit for shifting the input of the motor drive from the output of the start-up voltage generator to the output of the rotation control unit.

〔Example〕

 An embodiment of the present invention will be described with reference to FIG.

The disk 10 on which the video signal is pit-recorded by the FM modulation is placed on the table 36 provided on the rotation shaft of the disk motor 12. A motor drive circuit 32 is connected to the disk motor 12, and drives the disk motor 12 to rotate and rotate the disk 10 during reproduction.

An optical pickup 14 is provided on the lower surface side of the disk 10 to read a signal bit-recorded on the disk 10. From the optical pickup 14, A + by the main beam
Two diagonal signals C and B + D and A and B by side beams
The signal is output.

An RF amplifier 16 is connected to the output side of the optical pickup 14 and amplifies the RF signal of A + B + C + D. A BPF 17 is connected to the output side of the RF amplifier 16 to take out a predetermined video band in the RF signal. An FM video detector 18 is connected to the output side of the BPF 17, and FM detection is applied to the output of the BPF 17 to obtain an analog composite video signal.

This composite video signal is externally output to the TV device side.

A sync separation circuit 20 is connected to the output side of the FM video detector 18 and extracts a horizontal sync signal from the composite video signal.
The output side of this sync separation circuit 20 has a phase / frequency comparator.
22 is connected.

This phase / frequency comparator 22 also includes a reference signal generator.
24 is connected, and the phase / frequency comparison between the predetermined reference signal output from the reference signal generator 24 and the horizontal synchronizing signal is performed to obtain the difference signal. A compensating circuit 26 is connected to the output side of the phase / frequency comparator 22 to perform phase compensation and the like.

An amplifier 28 is connected to the output side of the compensation circuit 26,
After amplification here, the motor drive circuit via the switching SW30
It is output to 32, and rotation control of the disk motor 12 is performed.

As a result, during steady reproduction, the rotation speed of the disk 10 is controlled so that the frequency of the horizontal sync signal in the composite video signal matches the frequency of the reference signal.

By the way, since the composite video signal cannot be reproduced when the disk motor 12 is started, normal reproduction cannot be performed by the above rotation control forever.

Therefore, while the rotation speed of the disk 10 reaches a predetermined rotation range from zero, the input of the switching SW30 is switched to the starting voltage generator 34 side, and a predetermined constant voltage is applied to the motor drive circuit 32, The rotation speed is set to rise.

That is, on the output side of the FM video detector 18, BPF or HPF
Is connected to the noise detector 50, and detects a noise component in a predetermined band (for example, a frequency range higher than a normal video signal band) in the output of the FM video detector 18.

An AM detection circuit 52 is connected to the output side of the noise detector 50, and converts the noise component detected by the noise detector 50 into a DC noise level signal proportional to the level thereof.

A voltage comparator 54 is connected to the output side of the AM detection circuit 52. A reference voltage generator 56 is connected to the voltage comparator 54, and a magnitude of the noise level signal is compared with a predetermined reference voltage generated by the reference voltage generator 56. Switch the switching control signal
Output to SW30 and switch to control voltage side.

Here, when the disk 10 is in a steady rotation state, the frequency of the image component in the RF signal read by the optical pickup 14 and amplified by the RF amplifier 16 is within a normal predetermined band, and therefore passes through the BPF 17. , FM video detector 18 input. In this case, the noise component in the output of the FM video detector 18 is very small.

On the contrary, as the rotation of the disk 10 becomes slower than the steady state, the frequency of the image component in the RF signal of the RF amplifier 16 output becomes lower, it does not pass through the BPF 17, and the input of the FM image detector 18 decreases. Go. Then, the random noise component in the output of the FM video detector 18 increases, and the AM detection circuit 52
The output level of increases.

The predetermined reference voltage generated by the reference signal generator 56 reaches a predetermined range where the rotation speed of the disk 10 is near a steady value, and the switching SW
Even if 30 is switched to the rotation control side, the output level of the AM detection circuit 52 at which the control is reliably applied is set.

A tracking control unit 48 is connected to the other output side of the optical pickup 14, and based on the A and B signals of the sub beam,
Tracking control for the tracking coil 46 is performed. Further, a focusing control unit 52 is connected to the other output side of the optical pickup 14, and A + C of the main beam is used.
Focusing control for the focus coil 50 is performed based on the difference between the B and D signals. The tracking control unit 48 and the focusing control unit 52 are closed before the switching SW 30 is switched to the rotation control side.

Next, the operation of the above embodiment will be described.

It is assumed that the switch SW30 has been switched to the disconnection position in advance.

When the device is played, first, the optical pickup 14 is moved to the optimum position in the height direction with respect to the disc 10, and focusing control is applied.

Then, the switch SW30 is switched to the starting voltage generator 34 side by the control of the system microcomputer (not shown), and the disk motor 12 is driven at a constant voltage.

As a result, the rotation speed of the disk 10 rises from zero.
Tracking control is applied during the start of rotation of the disk 10.

Initially, when the rotation speed of the disk 10 is near zero, the RF amplifier
The frequency of the video component in the RF signal output by 16 is biased to the lower side and cannot pass through BPF 17.

At this time, the output of the FM video detector 18 becomes a large random noise, of which components in a predetermined frequency band higher than the video band pass through the noise detector 20. And AM detection circuit
At 52, it is converted into a large DC noise level signal proportional to the noise level.

Therefore, the noise level signal far exceeds the reference voltage output by the reference voltage generator 56, and the voltage comparator 54 does not output the switching signal.

After that, as the rotation speed of the disk 10 rises, the frequency of the video component in the RF signal output from the RF amplifier 16 gradually rises, and eventually a part of the video component passes through the BPF 17.

Then, the level of random noise in the output of the FM video detector 18 becomes smaller, and the noise level signal output from the AM detection circuit 52 approaches the reference voltage.

Then, when the rotation speed of the disk 10 reaches a predetermined range near the steady reproduction state about 5 seconds after the start of the disk motor 12, the frequency of the image component in the RF signal output from the RF amplifier 16 further increases. Then, most of them pass through the BPF 17, and the analog composite video signal is output from the FM video detector 18, and the level of random noise during output becomes extremely small, and finally the AM detection circuit. The noise level signal output by 52 falls below the reference voltage. Then, the voltage comparator 54 outputs a switching signal to the switching SW 30 to switch to the amplifier 28 side.

At this time, since the FM video detector 18 outputs a composite video signal in a substantially normal band, the sync separation circuit 20 outputs
A horizontal sync signal near the regular frequency is output. Therefore, the phase / frequency comparator 22 can perform phase / frequency comparison. The difference signal output by the phase / frequency comparator 22 is compensated by the compensation circuit 26, amplified by the amplifier 28, and then driven by the switching SW10 to drive the motor. It can be output to the circuit 32 and can be subjected to rotation control.

With this rotation control, the frequency of the horizontal synchronizing signal in the composite video signal is matched with the frequency of the reference signal, so that a stable playback screen can be obtained on the TV device side.

According to this embodiment, the noise component of the output of the FM video detector 18 is detected by the noise detector 50, converted into a direct current noise level signal by the AM detection circuit 52, and then a predetermined reference voltage by the voltage comparator 54. In comparison with the above, when the noise level signal falls below the reference voltage, a switching signal is output to the switching SW30 to close the rotation control system, so that a mechanical rotation detection mechanism for detecting the rotation speed of the disk 10. Is unnecessary,
The parts cost is low and the assembly is easy.

[Effect of device]

According to this invention, the motor drive unit for driving the disc motor, and the rotation control unit for controlling the motor drive unit based on the synchronization signal in the composite video signal detected from the disc to keep the synchronization of the synchronization signal constant. And a starting voltage generating section for generating a voltage for starting the disk motor and a switching operation according to a switching signal, and at the time of starting, the output of the starting voltage generating section is output until the number of rotations of the disk reaches a predetermined range. In addition to the motor drive unit, a switching unit for applying the output of the rotation control unit to the motor drive unit after the number of rotations of the disc reaches a predetermined range, The noise level in the output of the signal demodulation unit is detected, and the switching control unit compares the noise level detected by the noise detection unit with a predetermined value. By outputting a signal and switching the input of the motor drive unit from the output of the starting voltage generation unit to the output of the rotation control unit, it is not necessary to provide a special rotation detection mechanism for detecting the number of rotations of the disk. Even
With an extremely simple configuration, it is possible to switch the switching unit by detecting that the number of rotations of the disk has reached a predetermined range at the time of startup, so that there is an excellent effect that the cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a rotation control system of a video disc reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a rotation control system of a conventional video disc reproducing apparatus. 10: Disc, 12: Disc motor, 18: FM video detector, 2
0: Horizontal sync separation circuit, 22: Phase / frequency comparator, 30: Switching
SW, 32: Motor drive circuit, 34: Starting voltage generator, 50: Noise detector, 52: AM detector, 54: Voltage comparator, 56: Reference voltage generator.

Claims (1)

[Scope of utility model registration request] 1. A motor drive unit for driving a disc motor, and a rotation control unit for controlling the motor drive unit on the basis of a synchronization signal in a composite video signal detected from a disc so as to keep the period of the synchronization signal constant. , A starting voltage generating section for generating a voltage for starting the disk motor and a switching operation according to a switching signal, and at the time of starting, the output of the starting voltage generating section is output until the number of rotations of the disk reaches a predetermined range. In addition to the drive unit, in a video disc reproducing apparatus having a switching unit for adding the output of the rotation control unit to the motor drive unit after the number of rotations of the disc reaches a predetermined range, in the output of the video signal demodulation unit, A noise detection unit that detects a noise level and a noise level detected by this noise detection unit are compared with a predetermined value, and when the noise level falls below a predetermined value, a switching signal is output to the switching unit, Video disk reproducing apparatus comprising: the switching controller for shifting the output of the rotation control unit input over motor drive unit from the output of the start-up voltage generating unit.