JPH01319377A - Recording and reproducing device for video disk - Google Patents

Abstract

PURPOSE:To halve the linear velocity (number of revolutions) of a disk by dividing a video signal into 2 channels and recording and reproducing the result. CONSTITUTION:A video signal is split into 2 channels for each line, the time axis of the signal of each channel is expanded and recorded on two tracks 37, 38. That is, spots 35, 36 of two laser beams form recording pits along the tracks 37, 38. In the case of reproducing the recorded video disk, a reproducing laser beam 4 radiated respectively onto the two tracks 37, 38 on the video disk to reproduce the signal of the 2 channels, the time axis of the signal of each channel is compressed to reproduce the original signal. Thus, the video signal is recorded and reproduced while it is divided into two channels, then the signal band at each channel is halved into that of the original signal and the linear velocity is halved even if the shortest recording wavelength is the same.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording and reproducing apparatus for a video disc in which a pilot signal is frequency-multiplexed and recorded together with a video signal.

2. Description of the Related Art In recent years, a high-definition television system (high-visibility) has been proposed that can display wider images with higher definition than current television systems. This high-definition television system has more than five times the amount of information compared to the current television system, so even if it is recorded on a conventional video disc, it can only be recorded for a very short time.

On the other hand, MU allows NHK to band-compress high-definition television signals and broadcast them using one channel of satellite broadcasting.
The SE method was developed. By using a MUSE signal obtained by band-compressing a high-definition television signal using this method, it is possible to extend the recording time of a video disc.

However, since the MUSE system was developed for satellite broadcasting, the synchronization signal has positive polarity. For this reason, it is not possible to easily extract a synchronization signal by amplitude separation as in the case of current television signals, and it is difficult to use this synchronization signal to control the rotational speed of the disk or correct the time axis (jitter). Therefore, a pilot signal is frequency-multiplexed with the MUSE signal and recorded on the disk, and this pilot signal is used to control disk rotation and jitter during playback (
For example, Ninomiya et al.: Optical video disc for high-definition television using MUSE system IPA73-8).

Generally, when recording a video signal such as a MUSE signal on a disk, FM modulation is performed, and the pilot signal is frequency-multiplexed in a frequency lower than the lower sideband of the FM modulated wave. Therefore, when the FM-modulated MUSE signal and the pilot signal are frequency-multiplexed and recorded on and reproduced from a disk, intermodulation components are generated.

This intermodulation component becomes an interfering pattern on the demodulated screen and significantly degrades the image quality. In order to make this interference visually inconspicuous, the frequency fp of the pilot signal is
is a half-integer multiple of the horizontal synchronization frequency fh of the video signal (fp=
(k+1/2) fh: k is a positive integer). In this case, the phase of the pilot signal is inverted line by line and frame by frame on the playback screen.

Problems to be Solved by the Invention If a high-definition television signal is band-compressed using the MUSE method, it becomes an analog signal with a maximum frequency of 8.1 MHz.

The band of this MUSE signal is approximately twice that of current television signals. Therefore, if the same shortest recording wavelength as the current video disc used for recording television signals is used, the linear velocity during recording and playback will be approximately twice as high. To accommodate this, either the radius of the innermost circumference must be increased or the rotational speed of the disk must be increased. Therefore, the MUSE signal is divided into two channels, and the time axis of the recording signal of each channel is expanded.
It is conceivable to record on a disc by lowering the recording frequency band per channel. Since the MUSE signal is an analog signal, it is desirable to divide channels in units of lines. However, if each line is divided into two channels, there will be one extra line in one frame. Therefore, the phase of the pilot signal cannot be selected to be inverted line by line or frame by frame on the playback screen.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a video disc and a recording/reproducing apparatus thereof that can reduce the number of rotations of the disc and further reduce interference caused by pilot signals.

Means for Solving the Problems The present invention solves the above-mentioned problems by
A switching circuit that divides each line into two channels, a memory that extends the time axis of the signal of each divided channel, a clock conversion circuit that makes the horizontal synchronization frequency fr of the recording signal an even multiple of the frame frequency, and A pilot signal oscillation circuit that oscillates a pilot signal of (1/2 above m) fr (where m is a natural number), a multiplexing circuit that frequency multiplexes the pilot signal on the signal of one channel, and a recording signal in which the pilot signal is multiplexed. a first optical modulator that modulates with a recording signal on which a pilot signal is not multiplexed, and a second optical modulator that modulates with a recording signal on which a pilot signal is not multiplexed. Using a video disc recording device that records a video signal by irradiating it onto two tracks, the video signal is frequency-multiplexed with a pilot signal and recorded on a master video disc.

When playing back a video disc recorded in this way, two tracks on the video disc are each irradiated with a playback laser beam, a photodetector receives the reflected light from each track, and a photodetector is used to detect the playback signal from one of the tracks. A filter that extracts a pilot signal, a clock regeneration circuit that regenerates a clock signal from this pilot signal, and a memory that writes two channels of regenerated signals using the regenerated clock and reads them using an internal reference clock to compress the time axis. ,
There is a switching circuit that sequentially switches and reads two channels of reproduced signals from memory for each line of the video signal, a phase comparison circuit that compares the phases of the pilot signal generated from the reference clock and the reproduced pilot signal, and the motor is activated based on this phase difference. A video disc playback device is used, which is characterized by having a motor servo for controlling.

In the present invention, a video signal is divided into two channels line by line, the time axis of each channel's signal is extended, and the signal is recorded on two tracks. When playing back a video disc recorded in this way, it is possible to irradiate each of the two tracks on the video disc with a playback laser beam, play back two channels of signals, and compress the time axis of each channel's signal. and play the signal. By recording and reproducing the video signal in two channels in this way, the signal band in each channel becomes half of the original signal. Therefore, even if the shortest recording wavelength is the same, the linear velocity can be halved.

Furthermore, since two channels of signals are reproduced by simultaneously irradiating each track with a reproduction laser beam, the fluctuations in the time axis occurring in each channel are approximately equal. Therefore, it is possible to multiplex and record a pilot signal on one channel and use the time axis fluctuation component detected from this pilot signal during playback to correct the time axis fluctuation of the two channels.

If the video signal is divided into two channels per line, only one channel will be affected by the pilot signal, so that each line without interference will be reproduced on the playback screen.

In addition, the horizontal synchronization frequency fr of the recording signal is set to an even multiple of the frame frequency, and the frequency of the pilot signal is set to (1/2 above m).
) fr (where m is a natural number), the phase of the pilot signal on the playback screen can be inverted line by line and frame by frame.

Examples Examples of the present invention will be described below. In this example,
A MUSE signal is used as the video signal.

First, a recording device for recording video signals onto a master disc will be described. FIG. 1 is a block diagram showing the configuration of a disc recording apparatus in this embodiment. In FIG. 1, 1 is an input terminal, 5 is a switching circuit, 12 is a pilot signal generation circuit, 13 is a multiplex circuit, 18117 is an optical modulator,
20 is a master disk, and 32 is a clock conversion circuit.

A high-definition television signal is band-compressed by a MUSE encoder and converted into a MUSE signal, which is then applied to an input terminal 1. Furthermore, a transmission lock signal corresponding to the pixel of the MUSE signal is applied to the input terminal 30. The clock conversion circuit 32 records the transmitted lock signal as a clock signal! Convert to The input MUSE signal a is subjected to DC regeneration by a clamp 2, unnecessary components are removed by a low-pass filter 3, and converted into a digital signal by an A/D converter 4 every time a lock signal is transmitted. The switching circuit 5 switches the digitized MUSE signal to 1.
The output destination for each line is switched between the memory 6 and the memo IJ 7, and data is sequentially written. The two memories sequentially transmit the data of each pixel sent line by line from the switching circuit 5, write it in accordance with the lock signal, extend the time axis, and read out the data of each pixel in accordance with the recording clock signal i. .

The D/A converter 8 converts the data read from the memory 6 into an analog signal for each recording clock signal i. This time-axis expanded MUSE signal C is modulated by the inter-signal modulator IO, converted into a rectangular wave by the waveform shaping circuit I4, and then input to the optical modulator 1B as the recording signal d. Similarly, the D/A converter 9 converts the data read from the memory 7 into an analog signal for each recording clock signal i. This time-base expanded MUSE signal e is modulated by an FM modulator 11 and applied to a multiplex circuit 13. The paoloft signal generating circuit 12 generates a pilot signal synchronized with the recording cook signal i. The multiplexing circuit 13 frequency-multiplexes the pilot signal on this FM modulated wave to obtain a multiplexed signal f. After converting into a rectangular wave in the waveform circuit 15, the recording signals g and 1 are input to the optical modulator 17.

The laser beam oscillated by the argon laser 1B is divided into two laser beams by optical components 22, 23, and 24, and passes through an optical modulator 16 and an optical modulator 17, respectively. Optical modulator 1
6. The optical modulator 17 receives the recording signal d1 and the recording signal g, respectively.
The intensity of the laser light is modulated according to

Optical component 25.2[i combines the laser beams that have passed through each optical modulator into one laser beam. The mirror objective lens 19 controls the combined laser beams so that they are focused on a desired position on the disk master 20. As a result, the optical modulators 1 [i,
Two intensity-modulated laser beam spots are formed by the optical modulator I7. The motor 21 rotates the disk master 20 and records two tracks at two spots.

FIG. 2 is a schematic diagram showing the recording surface of a video disc on which video signals are recorded as described above.

In FIG. 2, two laser beam spots 35 and 36 form recording pits along tracks 37 and 38, respectively. Note that since the actual recording is performed by applying a photoresist onto the die-free master and exposing it to laser light, the recording pits are not visible before development, but they are shown schematically here. Also,
The method for creating a video disc for playback from such a master disc is the same as that for conventional video discs, so the explanation will be omitted.

Next, the recording clock when recording the MUSE signal by dividing it into two channels for each line will be explained. In order to make image quality deterioration due to the interference pattern of the pilot signal less noticeable on the playback screen, the phase of the pilot signal may be inverted line by line and frame by frame. Therefore,
In the method described above, in which the video signal is divided into two channels per line and the pilot signal is multiplexed and recorded on the recording signal of one channel, the phase of the pilot signal is inverted for each line in one channel, and It is sufficient that an odd number of lines exist in one frame period. Therefore, in a 2-channel recording signal, 2 (2 + 1)
[K: Positive integer lines are required. One frame of the MUSE signal has 1125 lines, so when recording all lines, one frame of the recording signal has 1125 lines.
26 lines are required. In this case, the horizontal synchronization frequency fr of the recording signal is 563 times the frame synchronization frequency, and if the horizontal synchronization frequency of the MUSE signal is fh, then the following equation is obtained.

fr = (563/1125) fh Similarly, if the transmission lock is fsl and the recording clock is fk, then the following is obtained.

fk=(563/1125)fs In addition, line inversion and frame inversion can be performed by setting the frequency fr of the pilot signal as follows.

FIG. 3 shows a timing diagram under the condition of fp=(mf:l/2) fr (where m is a positive integer) or more.

In Figure 3, the two channels are channel A1
Channel B is assumed, and the numbers on the lines in the figure represent the timing at which data on the line with that number is recorded.

As shown in the figure, in each frame, odd-numbered lines are recorded on channel A1 and even-numbered lines are recorded on channel B. In this embodiment, it is assumed that a pilot signal is multiplexed and recorded on track B.

Furthermore, in this embodiment, the cycle required to input two lines of the MUSE signal is longer than the cycle required to record one line of signals on two channels. This deviation becomes the largest at the time when the last even line is read. From the starting point A of the frame as shown in Figure 3! The time to readout point B of the 124th line is as follows.

T (B - A) = 5G1* (11251563)
*(+#h)>1121(1/rh) From this result, in order to read 1124 lines, it is necessary to delay the input MUSE signal by 3 lines or more. In this embodiment, the signal is delayed by 4 lines.

The operation of the memory at this time is shown in FIG. In FIG. 5, 5 is a switching circuit, and 6.7 is a memory. The memory 6 and the memory 7 each have a capacity for three lines, and the numbers in the figure are the numbers of the lines stored at that time.

FIG. 5(a) represents point A in FIG. The switching circuit 5 writes the fifth line of the MUSE signal into the memory 6, and reads the first line from the memory 6 and the second line from the memory 7. FIG. 5(b) represents point B in FIG.

The switching circuit 5 writes the first line of the MUSE signal into the memory 6, and reads the 1123rd line from the memory 6 and the 1124th line from the memory 7. Also, the 1126th
Since the line is not included in the original MUSE signal, disc-specific information can be recorded as a disc control signal. Address, chapter number, time code, CL as disc control signals
There are V/CAV discrimination codes, etc. The disk control signal is generated by the control signal generation circuit 3I in FIG. 1, and when the memory 7 reads the 1126th line,
Data on the 112th B line is read not from the memory 7 but from the control signal generation circuit 31.

Next, a reproducing apparatus for reproducing a video disc on which video signals have been recorded as described above will be described. FIG. 4 is a block diagram showing the configuration of the disc playback device in this embodiment. In FIG. 4, 40 is a video disk;
2 is a semiconductor laser, 45 is a photodetector, 54 is a bandpass filter, 58 is a clock regeneration circuit, 52.57 is a memo 1c, 59 is a switching circuit, 64 is a phase comparison circuit, and 85 is a motor servo.

The video disc 40 is rotated by the motor 6B. The semiconductor laser 42 emits two reproduction laser beams.

The reproduction laser beam is directed onto the disk by the objective lens 4I. The objective lens 41 controls the spot of the reproducing laser beam so as to follow each track as in the case of FIG. Optical components 43 and 44 separate the laser light emitted from the semiconductor laser 42 and the laser light reflected from the disk, and make the reflected light enter the photodetector 45. The photodetector 45 receives reflected light from the two tracks, performs photoelectric conversion, and then outputs it to each preamplifier.

The reproduced signal j reproduced from track A shown in FIG.
Amplify with preamplifier 4B, equalize with equalizer 48,
The signal is demodulated by an FM demodulator 50 and becomes a MUSE signal l. Similarly, for the playback signal played from track B, the preamplifier 4
7, equalized by an equalizer 49, and applied to a bypass filter 53 and a bandpass filter 54. Since the pilot signal is multiplexed on the FM modulation signal in this reproduced signal k, the FM modulation signal is extracted by the bypass filter 53, and the pilot signal p is extracted by the bandpass filter 54.
Extract. The extracted FM modulated signal is demodulated by an FM demodulator 55 and is used as a MUSE signal m.

The clock reproducing circuit 58 generates a recording clock n corresponding to a pixel of the MUSE signal recorded by time-axis expanding the extracted pilot signal p. The A/D converter 51 converts the MUSE signal l demodulated by the recording clock n into a digital signal and writes it into the memory 52. Similarly, A/
The D converter 56 converts the MUSE signal m demodulated by the clock n into a digital signal and writes it into the memory 57.

The control signal detection circuit 68 detects the disk control signal recorded on the 1128th line of the MUSE signal m. In addition, the reference clock generation circuit 62 is the original MU
A transmission lock 0 corresponding to the pixel of the SE signal is generated.

The switching circuit 53 selects the input destination for each line from the memory 52.
and switches to memory 57 and reads out according to transmission lock 0. The D/A converter 60 converts the data of the read MUSE signal into an analog signal, amplifies it with the amplifier 61, and outputs it from the output terminal 67. The output MUSE signal is
The SE decoder performs reproduction processing to reproduce a high-definition television signal. Further, the reference pilot signal generation circuit 63 generates a pilot signal q synchronized with this clock from transmission lock 0.
to occur. The phase comparison circuit 64 compares the phases of the internally generated pilot signal q and the reproduced pilot signal p, and generates a phase error signal r. The motor servo circuit 65 controls the rotation speed of the motor so that the phase error signal r does not accumulate.

Furthermore, in this embodiment, the cycle for reproducing one line of signals from each of the two channels is shorter than the cycle required for outputting two lines of MUSE signals.

Therefore, there is no need to adjust the delay time in memory,
After reproducing one line of signals from each of the two channels,
Just read this out.

As described above, according to this embodiment, since two channels of signals are reproduced by simultaneously irradiating each track with the reproducing laser beam, the fluctuations in the time axis occurring in each channel are approximately equal. Therefore, the demodulated reproduced signals of the two channels were written to the memory using the clock reproduced from the pilot signal multiplexed and recorded on one channel, and the time axis was expanded and recorded by reading them from the memory using the reference clock. At the same time as compressing the time axis of the MUSE signal and converting it to the original MUSE signal, it is possible to remove time axis fluctuations (jitter) contained in the reproduced signal. Regular fluctuations in the time axis can be removed by controlling the rotation speed of the motor so that the phase error signal of the pilot signal becomes small.

As shown in Figure 3, only the line recorded on track B is affected by the pilot signal, and the MUSE
Since the signal is divided line by line, the pilot signal is mixed only in the even numbered lines at the top of the playback screen, but no pilot signal is mixed in the odd numbered lines. Moreover, the phase is reversed between even lines, and the phase is reversed between frames on the same line, so the interference pattern caused by the pilot signal becomes conspicuous. Even if interpolation is performed between fields, there is a line without interference for each line, so it is possible to reduce image quality deterioration caused by pilot signals.Also, when interpolating between frames, motion vectors
Although the signal before the frame moves, the phase of the pilot signal matches and the probability that interference is emphasized can be reduced.

Note that although the MUSE signal is used as the video signal in this embodiment, the present invention is not limited to this, and can be applied to the case where pilot signals are multiplexed and recorded.

Effects of the Invention As described above, according to the present invention, by dividing the video signal into two channels and recording and reproducing it, the linear velocity (rotational speed) of the disk can be halved, which has a great practical effect. .

In addition, the video signal is divided into two channels per line,
By multiplexing and recording a pilot signal on one channel, only one channel is affected by the pilot signal, and each line without interference is reproduced on the reproduction screen. Therefore, regardless of the MUSE method interpolation processing, image quality deterioration due to pilot signal mixing can be reduced.

Furthermore, the horizontal synchronization frequency fr of the recording signal is set to an even multiple of the frame frequency, and the frequency of the pilot signal is set to (1/1 on m).
2) By setting fr (where m is a natural number), the phase of the pilot signal on the playback screen can be reversed line by line and frame by frame.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a disc recording device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the recording surface of a video disc in the same device, and FIG. 3 is a timing diagram of the same device. FIG. 4 is a block diagram showing the configuration of a disc playback device according to an embodiment of the present invention, and FIG.
- Pilot signal generation circuit, 13... multiplex circuit, 16.
17... Optical modulator, 20... Disk master, 40... Video disk, 42... Semiconductor laser, 45... Photodetector, 54... Bandpass filter, 58... Clock regeneration circuit, 52.57.・Memory, 59...Switching circuit,
64... Phase comparator circuit, 65... Motor servo. Name of agent Patent attorney Toshio Nakao One idiot Figure 2 37 No. 50

Claims (2)

[Claims] (1) A switching circuit that divides each line of the video signal into two channels, a memory that stores the signals of each divided channel, and a clock conversion circuit that sets the horizontal synchronization frequency fr of the recording signal to an even multiple of the frame frequency. , the frequency is (
A pilot signal oscillation circuit that oscillates a pilot signal of m±1/2)fr (where m is a natural number) and a signal of one channel read out from the previous memory with time axis expanded using the clock of the previous clock conversion circuit. a multiplexing circuit that frequency multiplexes the pilot signal; a first optical modulator that modulates the recorded signal with the pilot signal multiplexed thereon; and a first optical modulator that modulates the pilot signal with the readout recording signal of the other channel on which the pilot signal is not multiplexed. 1. A video disc recording device, comprising: a second optical modulator, and records a video signal by irradiating two tracks on a master disc with a light beam modulated by each optical modulator. (2) A device that plays back a video disc recorded by frequency multiplexing a pilot signal with a video signal, which irradiates each of the two tracks on the video disc with a playback light beam and receives the reflected light from each track. a photodetector that extracts a pilot signal from one of the regenerated signals, a clock regeneration circuit that regenerates a clock signal from this pilot signal, and an internal reference clock that writes two channels of regenerated signals using the regenerated clock. 1. A video disc playback device comprising: a memory that compresses the time axis by reading the video signal; and a switching circuit that sequentially switches and reads two channels of playback signals from the memory for each line of a video signal.