JPH0115943B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for transmitting light such as a laser beam to a microscopic diameter (approximately φ1 μm).
In a video signal recording and reproducing device that optically records and reproduces information signals such as video signals with high density by focusing the beam onto a disc-shaped recording medium (hereinafter referred to as a disk), the address signal is recorded in advance. When recording and reproducing a video signal superimposed on the address signal on a disk having a groove-shaped guide track attached thereto, the influence of the address signal on the video signal is removed, making it possible to safely record and reproduce the video signal. .

As seen in the conventional example of video discs,
A device that uses a light beam such as a laser on a disk to record and reproduce video signals at high density as a concentric or spiral recording locus, or as a binary signal such as unevenness or light and shade, or a device that performs only reproduction. There is a device. In such a device, for example, when recording a video signal, the video signal is a carrier signal of an appropriate frequency that is FM modulated with the video signal, converted to a binary signal using a limiter, etc., and recorded as the length of the recording pit. Regeneration is performed.

Conventionally, when recording and reproducing video signals on the disk, the color signal processing method was direct.
There are the FM method, Verizudowaroma method, low frequency conversion method, etc., but here, as an example, we will discuss the case where a video signal is recorded and reproduced using the low frequency conversion method.

FIG. 1 shows a configuration diagram of a conventional example in which a video signal is optically recorded and reproduced using a low frequency conversion method. Further, FIG. 2 shows the spectrum of each part of the video signal processing circuit of the low frequency conversion method shown in FIG. 1.

In FIG. 1, 1 to 9 are block diagrams of video signal processing circuits for recording, 10 to 18 are block diagrams of a recording and reproducing device for recording and reproducing on a disk, and 19 are block diagrams of video signal processing circuits for recording.
26 shows a block diagram of a video signal processing circuit for converting the reproduced signal from the disk into the original video signal.

First, a video signal such as an NTSC signal is input to terminal A. FIG. 2a shows the spectrum of the video signal. Y is a luminance signal and C is a 3.58MHz color signal. Next, the video signal input to terminal A in FIG.
Only the luminance signal shown in Figure b is extracted. The luminance signal is then sent to AGC circuit 2, pre-emphasis circuit 3,
The signal is input to the FM modulator 5 via the clamp circuit 4a and the white clip circuit 4b. FM modulator 5
FM with brightness signal on any frequency carrier
Modulate. At this time, the spectrum of the FM modulation signal is shown in Figure 2c.

On the other hand, from the color signal, only the 3.58 MHz color signal is extracted by the bandpass filter 7, as shown in FIG. 2d, and is input to the color signal processing circuit 8.
Color signal processing circuit 8 includes ACC circuit and 3.58M
Hz color signal, low frequency (629K as an example)
It consists of a balanced modulator etc. for converting to
As shown in FIG. 2e, a color signal converted to a low frequency is output. Next, from FM modulator 5
The color signal converted to FM modulated signal and reduced is
Mixing is performed by a mixing circuit 6. The spectrum at this time is shown in Fig. 2f. An example of a waveform diagram of the output of the mixing circuit 6 is shown in FIG. 2g. In Figure 2g, the part A forming the envelope is the color signal component that has been low-frequency converted, and the part B is the
This is an FM-modulated luminance signal component. Mixing circuit 6
The output signal is input to a recording circuit 9 comprising a limiter circuit or the like. The output waveform of the recording circuit 9 is shown in FIG. 2h. The signal shown in FIG. 2h contains the FM-modulated luminance signal and the color signal mixed in as a change in the duty of the FM-modulated signal. So-called pulse duty modulation is used. The signal from this recording circuit 9 is recorded on the disk as a binary signal to be recorded.

In order to record such a binary signal on a disk, generally, as shown in FIG. FM, which is a binary signal
The intensity of the light beam from the light source 10 is modulated by the modulation signal. The light beam from the optical modulator 11 is divided into 1 μmφ by an objective lens 12 of a microscope or the like.
The light is irradiated onto the disk 13 to perform recording and reproduction. The disk 13 is rotated by a motor 14 at a constant speed. Further, the disk 13 is transferred in the radial direction by the step motor 18 and the transfer shaft 17. 16 is a support for the disk 13, the motor 14, and the transfer shaft 17. As described above, the video signal converted into the binary signal of the FM modulation signal is converted into light intensity by the optical modulator 11, and the disc 1
3 are sequentially recorded.

Next, a case in which a video signal is reproduced from the disk 13 will be briefly described. During reproduction, a light beam weaker than the optical modulator 11 is irradiated onto the disk 13, and the intensity of reflected light or transmitted light (shown as transmitted light in FIG. 1) from the disk 13 is transmitted to the photoelectric converter 15. Therefore, it is detected, converted into an electrical signal, and inputted to the regenerative amplifier 19. The reproduction signal from the reproduction amplifier 19 is input to a high-pass filter 20 and a low-pass filter 25. The high-pass filter 20 outputs only the FM-modulated luminance signal component, the limiter circuit 21 performs waveform shaping, the FM demodulation circuit 22 demodulates the FM, and outputs a luminance signal. In the de-emphasis circuit 23,
Compensates the frequency characteristics of the luminance signal and outputs it. On the other hand, the low-pass filter 25 outputs only the color signal components converted to low frequencies, and the color signal processing circuit 2
6, the signal is converted into a 3.58MHz color signal using a balanced modulator or the like. Next, the FM demodulated luminance signal and color signal are mixed in a mixing circuit 24 and outputted from terminal B as a video signal.

On the other hand, the address signal pre-recorded on the recording track of the disk 13 is input from the reproducing amplifier 19 to the low-pass filter 27, where only the frequency component of the address signal is extracted, and is passed through the waveform shaping circuit 28 to the address reading circuit (first (not shown in the figure).

FIG. 3 is a diagram showing a part of the disk 13. As shown in FIG. The disk 13 has a width w, a pitch p, and a depth δ.
A groove-shaped guide track a is formed concentrically or spirally. Figure 3b shows the groove.

Figure 4 shows the disc 13 along the guide track.
FIG. c is a base material portion of the disk 13, e is a recording surface coated with a photosensitive recording material, and d is a protective layer. Also recording surface e
consists of an address signal area in which address signals and the like are recorded in advance, and an information area in which no address signals and the like are recorded.

In the disk 13 as described above, video signals and the like are recorded on the recording surface e, and also in the address signal area, they are recorded over the address signal.

Next, FIG. 5 shows the relationship between the address signal and the frequency of the video signal to be recorded. Figure 5 is the same as the spectrum distribution diagram shown in Figure 2f,
The FM modulated luminance signal is shown in Y (FM), and as an example, the sync chip is 4.5MHz and the white peak is 6M.
It is set as Hz. Furthermore, the frequency of the color signal C converted to the low frequency band is, for example, 629KHz. Also, the address signal is generally phase encoded modulated.
It is processed using a code signal modulated by PE, modified FM modulation MFM, etc. Further, the address signal is generally inserted into the vertical blanking (V blank) section of the video signal or into the overscan of the receiver.

As shown in FIG. 5, the frequency of the address signal is set to about 250 KHz to 500 KHz depending on the modulation method, number of digits, etc. Also, the width of the entire address signal is 3 times the width of the video signal.
Corresponds to the ~4H interval.

Next, FIG. 6 shows an example of a waveform when a video signal is superimposed and recorded on a groove-shaped guide track on which the address signal as described above is formed.

FIG. 6a shows the reproduction signal of the grooved guide track. The part A in FIG. 6A shows the address signal part. FIG. 6b is a diagram showing a reproduced signal when a video signal or the like is recorded on the groove-shaped guide track.
The part B is the FM modulation signal part. Figure 6b
As shown in , the section of the address signal is recorded with the FM modulation signal superimposed on the address signal. When the FM modulated signal in this address signal section is FM demodulated, the 6th
As shown in Figure c, noise is generated at the rising and falling timings of the address signal. This is due to transient characteristics in the video signal processing circuit. When such noise occurs, it interferes with the screen. Also, as mentioned above, the address signal is set so that it falls within the V blank and overscan of the receiver, so when the above noise occurs,
It also affects disturbances such as vertical synchronization of the receiver. Therefore, it is desirable to correct the video signal in such an address signal section.

FIG. 7 is a typical example of a dropout waveform that occurs when a disc is optically reproduced. Figure 7a shows the disc playback signal, B shows the FM modulation signal part, and D and D' are drop-out waveform examples, typically 1 μs to 5 μs.
Many of them have a short width. Figure 7b is Figure 7a
This is a waveform diagram obtained by FM modulating the reproduced signal and converting it into a video signal.The parts E and E' are noise caused by dropout, which protects the screen from damage.

Such address signal sections and dropout sections that protect the screen from damage can generally be corrected by a dropout correction circuit. This dropout correction is generally used when playing from a disc.
This is done using an FM modulation signal, but in this case, the remaining correction occurs at the beginning of the correction interval, so recently, FM
After converting a modulated signal into a video signal, dropout correction is performed. However, with this method, when correcting long sections such as address signal sections,
There are problems such as delays in transfer due to circuit delays.

In order to eliminate the above-mentioned problems, the present invention provides a first correction circuit that corrects long correction sections such as address signals, and a second correction circuit that corrects short dropouts that typically occur when playing a disc. By installing a circuit, the influence on the screen etc. is eliminated.

The present invention will be described below with reference to the drawings.

FIG. 8 shows a block diagram of an embodiment of the video signal recording and reproducing apparatus of the present invention. In Figure 8, the first
Components similar to those in the figures are given the same numbers and detailed explanations will be omitted. FIG. 9 shows a waveform diagram of each part, and the operation will be described according to the waveform diagram.

11 is a light modulator, 12 is an objective lens, 13 is a disk, 14 is a motor, 15 is a photoelectric converter, 1
6 is a support, 17 is a transfer shaft, and 19 is a regenerative amplifier.

The reproduced signal from the disk 13 is transmitted to the photoelectric converter 1
5 into an electrical signal, and the regenerative amplifier 19
The width is increased by A waveform diagram of this reproduced signal f is shown in FIG. 9f. F is the dropout portion, and G is the address signal section. The reproduced signal f is
amplifier 50, dropout period detection circuit 51,
It is input to the address signal section detection circuit 52. Amplifier 5
0 is an amplifier for compensating for the recording/reproducing characteristics of the disk 13, etc. Dropout period detection circuit 51
is a circuit for detecting the period to dropout in the reproduced signal f, and the waveform diagram of the output signal is shown in FIG. 9g. The address signal section detection circuit 52 is
FIG. 9h shows a waveform diagram of the output signal of a circuit that detects only the section of the address signal (portion G in FIG. 9f). The mixing circuit 53 mixes the outputs of the dropout period detection circuit 51 and the address signal section detection circuit 52. Terminal
(FIG. 9i) is input from a control circuit (not shown). The address signal extraction pulse i is generated by the gate circuit 54
and a gate circuit 56 via an inverter circuit 55.
Enter. On the other hand, the output signal from the mixing circuit 53 is input to the gate circuits 54 and 56, and the gate circuit 54 receives the address signal section detection signal j (9th
(shown in FIG. j), and the gate circuit 56 outputs only
A dropout detection signal k (shown in FIG. 9k) generated in an interval other than the address signal sampling pulse i is output. The address signal section detection signal j is input to the first correction circuit 57. This first correction circuit 57 is
It has the same configuration as the dropout correction circuit for FM modulated signals, and performs correction using a signal one horizontal scanning period 1H before the address signal section detection signal j.
This first correction circuit 57 corrects and outputs only the address signal section. The output signal of the first correction circuit 57 is subjected to a high-pass filter 20 to remove color signal components, a limiter circuit 21 to waveform shaping,
Input to FM demodulator 22. In the FM demodulator 22,
Converts the FM modulation signal to the original luminance signal and sends it to the second correction circuit 5 via the de-emphasis circuit 23.
Enter into 8. This second correction circuit 58 is a dropout correction circuit for brightness signals,
A dropout section occurring at a location other than the address signal sampling pulse i is corrected.

The luminance signal whose dropout section has been corrected by the second correction circuit 58 is input to the mixing circuit 24. On the other hand, from the color signal, only the color signal component is extracted by a low-pass filter 25, and the color signal processing circuit 26 extracts only the color signal component.
Then, the signal is converted into a 3.58MHz color signal, inputted to the mixing circuit 24, mixed with a luminance signal, and outputted from terminal B as a reproduced video signal 1. A waveform diagram of the reproduced video signal is shown in FIG. 9l.

FIG. 10 shows a block diagram of an embodiment of the dropout period detection circuit 51. Further, FIG. 11 shows a waveform diagram of each part.

In FIG. 10, 60 and 61 are comparison circuits;
2 is a mixing circuit. The reproduction signal f from the disk applied to the terminal F is input to comparison circuits 60 and 61. In the comparison circuits 60 and 61, the volume
The reference voltages set by VR ₁ and VR ₂ (dotted lines P and Q in Fig. 11f) are compared with the dropout included in the reproduced signal f (f in Fig. 11f), and the dropout detection signals g', g'' output, mixing circuit 6
2 and output from terminal G as a dropout detection signal g.

FIG. 12 shows a block diagram of an embodiment of the address signal section detection circuit 52. FIG. 13 shows waveform diagrams of each part.

The address signal section detection circuit 52 includes a low-pass filter 63, an amplifier 64, and a mimit trigger circuit 6.
5. Consists of a multi-vibrator 66. A reproduction signal f from the disk is input to the terminal H. FIG. 13f shows a waveform diagram of the reproduced signal f, in which the top part is the address signal part and the bottom part is the dropout part. The FM modulation signal component is removed by the low-pass filter 63, and a signal m containing only the address signal component is output (waveform shown in FIG. 13 m). The signal is amplified by an amplifier 64, subjected to waveform shaping by a Schmitt trigger circuit 65, and inputted to a multivibrator 66. The output signal of the Schmitt trigger circuit is
Shown in Figure n. In the multivibrator 66, the time constant is set to be slower than the frequency of the address signal so that the address signal section becomes one pulse. The output signal h of the multivibrator 66 is shown in FIG. 13h.

FIG. 14 is a block diagram showing one embodiment of the first correction circuit 57. An FM modulated reproduction signal from the amplifier 50 shown in FIG. 8 is input to the terminal J. The switching circuit 67 outputs the signal input from the 1H delay line 68 only during the address signal section detection signal j input from the terminal L, and otherwise switches to output the reproduced signal input from the terminal j. . Terminal K is the output terminal of the first correction circuit 57.

FIG. 15 is a block diagram showing one embodiment of the second correction circuit 58. A terminal M receives an FM demodulated luminance signal. Terminal 0 of switching circuit 69
A dropout period detection signal k is input to the . The brightness signal output from the switching circuit 69 is AM
As an example, the modulator 70 performs AM modulation using a 3.58 MHz carrier wave input from terminal R. The AM modulated signal is delayed by 1H by a 1H delay line 71, converted into an original luminance signal by an AM demodulator 72, and inputted to a switching circuit 69. The switching circuit 69 selects 1H only during the dropout period detection signal k.
It outputs the delayed luminance signal, and otherwise switches to output the original luminance signal. Terminal N is the output terminal of the second correction circuit 58.

As described above, in the present invention, two correction circuits are provided,
The first correction circuit corrects a relatively long address signal period in the FM modulation signal state, and the second correction circuit corrects a relatively short dropout other than the address signal in the demodulated video signal state. By correcting the above, it is possible to remove the influence on the screen due to the correction remaining by the correction circuit. Furthermore, since the long width of the address signal section can be corrected, disturbances such as vertical synchronization occurring in a receiver or the like can also be removed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional video signal recording and reproducing device, FIG. 2 is a diagram showing the spectrum of each part of the video signal processing circuit of the video signal recording and reproducing device shown in FIG. FIG. 4 is a cutaway perspective view of a disk provided with a shaped guide track; FIG. 4 is a sectional view along the guide track of the disk shown in FIG. 3; FIG.
Figure 6 is a spectrum diagram showing the relationship between the video signal to be recorded and the address signal, Figure 6 is a waveform diagram of the address signal reproduced from the disc, Figure 7 is a waveform diagram showing the effect of dropout on the reproduced signal, and Figure 8 is a waveform diagram showing the influence of dropout on the reproduced signal. 9 is a block diagram showing an embodiment of the video signal recording and reproducing device of the present invention, FIG. 9 is a waveform diagram of each part of the video signal recording and reproducing device shown in FIG. 8, and FIG. 10 is a dropout period in FIG. 8. FIG. 11 is a block diagram showing one embodiment of the detection circuit, and FIG. 12 is a waveform diagram of each part of the dropout period detection circuit shown in FIG.
13 is a block diagram showing one embodiment of the address signal section detection circuit, FIG. 13 is an operation waveform diagram of each part of the address signal section detection circuit shown in FIG. 12, and FIG. FIG. 15 is a block diagram showing an embodiment of the second correction circuit in FIG. 8. FIG. 19...Regeneration amplifier, 20...HPF, 21...
... Limiter, 22 ... FM demodulation circuit, 23 ... De-emphasis circuit, 24, 53 ... Mixing circuit, 25 ... LPF, 26 ... Color signal processing circuit, 50 ... Amplifier, 51 ... Dropout period Detection circuit, 52...Address signal section detection circuit, 5
7...first dropout correction circuit, 58...
Second dropout correction circuit.

Claims (1)

[Claims] 1. A means for reproducing recorded signals from a disc-shaped record carrier on which a frequency-modulated video signal is recorded superimposed on the address signal on a guide track on which an address signal is recorded, and a dropout period in the reproduced signal. dropout period detection means for detecting the address signal period, address signal period detection means for detecting the address signal period, and a first method for correcting dropout by converting the reproduced signal into a frequency modulated signal only during the detection period of the address signal period detection means. A video signal reproducing device comprising dropout correcting means and second dropout correcting means for correcting dropout in a state in which the reproduced signal is demodulated by the output of the dropout period detecting means during a period other than the address signal section.