JPH026146B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal recording and reproducing device that sequentially records and/or reproduces video signals and the like on a disk-shaped recording medium (hereinafter referred to as a disk) as concentric or spiral recording trajectories. .

As seen in the conventional example of video discs,
A device that only records video signals on a disk at high density as a binary signal such as unevenness or light and shade using a light beam such as a laser or mechanically as a concentric or spiral recording locus, or a device that performs recording and playback. There is equipment to do it. In such a device, for example, when recording a video signal, a carrier signal with a frequency appropriate for the video signal 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 FM methods, vertical chroma methods, low-frequency conversion methods, etc., and here, as an example, a case will be described in which the low-frequency conversion method is used to record and reproduce video signals.

Figure 1 is a circuit block diagram showing the conventional overall configuration when optically recording and reproducing video signals using the low-frequency conversion method, and Figure 2 is a circuit block diagram of the video signal processing circuit of the circuit blocks shown in Figure 1. It is an explanatory diagram showing a spectrum of each part. 1 is a low bass filter, 2
is the AGC circuit, 3a is the pre-emphasis circuit, 4
a is a clamp circuit, 4b is a white clip circuit, 5 is an FM modulator, 6 is a mixing circuit, 7 is a band pass filter, 8 is a color signal processing circuit, and 9 is a recording circuit, and these low-pass filters 1 to 3 are recording circuits. 9 constitutes a video signal processing circuit for recording. 10 is a light source, 11 is a light modulator, 12 is an objective lens, 13 is a disk, 14 is a motor, 15 is a photoelectric converter, 16 is a support, 17
1 is a transport shaft, and 18 is a step motor. These light source 10 to step motor 18 constitute a recording and reproducing device for recording and reproducing data on and from the disk 13. 19 is a regenerative amplifier, 20 is a high bass filter, 21 is a limiter circuit, 22 is an FM demodulator, 23a is a de-emphasis circuit, 24 is a mixing circuit, 25 is a low bass filter, and 26 is a color signal processing circuit. 19 to color signal processing circuit 26 constitute a video signal processing circuit for converting the reproduced signal from the disk 13 into the original video signal.

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. From the video signal input to terminal A, only the luminance signal Y shown in FIG. 2b is extracted by the low-pass filter 1, and this luminance signal Y
are AGC circuit 2, pre-emphasis circuit 3a,
The signal is input to the FM modulator 5 via the clamp circuit 4a and the white clip circuit 4b. FM modulator 5
is a carrier of an arbitrary frequency as a luminance signal Y.
Modulate. The spectrum of the FM modulated signal at this time is shown in Fig. 2c.

On the other hand, from the video signal input to terminal A, the bandpass filter 7 converts the video signal as shown in Figure 2d.
Only the 3.58MHz color signal C is extracted, and this color signal C is input to the color signal processing circuit 8.
The color signal processing circuit 8 receives a 3.58MHz color signal C.
It consists of a balanced modulator, an ACC circuit, etc. for converting the signal to a low frequency (for example, 629 KHz), and outputs a color signal converted to the low frequency as shown in FIG. 2e. FM from FM modulation 5
The modulation signal and the color signal converted to low frequency are mixed by a mixing circuit 6. The spectrum at this time is shown in FIG. 2f. An example of the output waveform diagram of the mixing circuit 6 is shown in FIG. 2g. In Figure 2g,
The A part forming the envelope is the low frequency converted color signal component, and the B part is the FM modulated luminance signal component. The output signal of the mixing circuit 6 is input to a recording circuit 9 constituted by a limiter circuit or the like. The output waveform of the recording circuit 9 is
Shown in Figure h. The output signal of the recording circuit 9 contains an FM-modulated luminance signal and a color signal incorporated as a change in the duty of the FM-modulated signal (so-called pulse duty modulation). The signal from the recording circuit 9 is recorded on the disk 13 as a binary signal to be recorded.

In order to record on such a binary disc 13, generally, as shown in FIG. FM which is a value signal
The intensity of the light beam from the light source 10 is modulated by the modulation signal. A light beam from an optical modulator 11 is focused to about 1 μΦ by an objective lens 12 such as a microscope and irradiated onto a disk 13 for recording and reproduction. The disk 13 is rotated at a constant speed by a motor 14, and is transferred in the radial direction by a step motor 18 and a transfer shaft 17. The support 16 is screwed onto the transfer shaft 17 and the disk 13
and supports the motor 14. in this way,
The video signal converted into a binary signal of the FM modulation signal is converted into light intensity by the optical modulator 11,
The data are sequentially recorded on the disk 13.

When reproducing a video signal recorded on the disk 13, a light beam weaker than the optical modulator 11 is irradiated onto the disk 13, and the reflected light or transmitted light (transmitted light in the example of FIG. 1) from the disk 13 is transmitted. The strength of the signal is detected by the photoelectric modulator 15, modulated into an electrical signal, and input to the regenerative amplifier 19. The reproduced signal from the regenerative amplifier 19 is input to a high pass filter 20 and a low pass filter 25. Only the FM-modulated luminance signal component is extracted by the high-pass filter 20, and this luminance signal component is waveform-shaped by the limiter circuit 21 and then FM demodulated by the FM modulation circuit 22. The luminance signal thus obtained is output after its frequency characteristics are compensated by the de-emphasis circuit 23a. On the other hand, the low-pass filter 25 extracts only the color signal component converted to a low frequency band and inputs it to the color signal processing circuit 26. The color signal processing circuit 26 is an AFC-
It undergoes signal processing such as APC, and is further converted into a 3.58 MHz color signal by a balanced modulator or the like that constitutes a part of the color signal processing circuit 26. This color signal and the FM-modulated luminance signal are combined into a mixing circuit 2.
4 and outputted from terminal B as a reproduced video signal.

In the video signal recording and reproducing apparatus as described above, when recording and reproducing video signals, the recording and reproducing frequency characteristics of the disk 13 pose a problem in signal processing. When a signal like that shown in Figure 2h is recorded on the disk 13, if the circuit system, optical system, and recording medium system all have flat frequency characteristics, the same signal as shown in Figure 2h will be reproduced. However, if it has certain frequency characteristics, it is not possible to obtain the same reproduced signal as in Fig. 2h. Generally, circuit systems and optical systems can be made flat within the frequency band handled by the recording and reproducing apparatus (for example, 0 to 7 MHz), but high frequency components in the recording medium system are attenuated. Further, in the case of the disk 13 rotating at a constant rotation speed, the recording/reproducing frequency characteristics differ between the outer circumferential portion and the inner circumferential portion, and high frequency components are attenuated more strongly on the inner circumferential side than on the outer circumferential side. That is, it has recording/reproducing frequency characteristics as shown in FIG. Third
In the figure, the solid line C indicates the recording/reproducing frequency characteristics of the outer circumferential portion, and the solid line D indicates the recording/reproducing frequency characteristics of the inner circumferential portion. In order to record an FM modulated signal in the frequency band shown in Figure 4 (as an example, the synchronization tip is 5 MHz and the white peak is 6.5 MHz) on the disk 13 having such recording/reproducing frequency characteristics, a general method is required. As shown in FIG. 1, a pre-emphasis circuit 3a, a clamp circuit 4a for stabilizing the FM modulation frequency, a white clip circuit 4b for preventing overmodulation, etc. are provided. A waveform diagram at this time is shown in FIG. FIG. 5 shows only the luminance signal component of the color bar signal, and E is the leading edge of the synchronization signal, which corresponds to the 5MHz portion of FIG. 4 if FM modulated. This E level is the clamp circuit 4a.
clamp level. Furthermore, F is the white peak, which corresponds to the 6.5MHz portion in Figure 4.
The white clip level is the white clip level of the white clip circuit 4b.

Here, the improvement of noise characteristics after FM demodulation will be explained. When one frequency component of noise contained in an FM signal is demodulated, the frequency component of the noise component near the carrier wave is small, and the frequency component of the frequency component distant from the carrier wave becomes an output proportional to the frequency far away. It is called triangular noise because its frequency characteristics are triangular. The reason for this characteristic is analytically determined from FM demodulation theory. As a result, the frequency vs. output characteristic is the same as that of the frequency discriminator used for FM demodulation, so it is thought that the frequency discriminator causes triangular noise. Video emphasis is a method for improving the SN ratio, taking into account the fact that the reproduced video signal with triangular noise has many noise components in the high frequency region. (emphasis circuit) to enhance the high frequency components of the video signal.
The noise in the high frequency region is suppressed by emphasizing the signal before FM modulation and restoring it after demodulation using a de-emphasis circuit 23a (high-frequency suppression circuit) having the opposite characteristics to the pre-emphasis circuit 3a. FIG. 6 shows how this noise is suppressed. This method is very effective in improving the signal-to-noise ratio, but because it emphasizes the high frequency range of the video signal, the rising part of the waveform that changes from black to white, where many high frequency components are concentrated, is shown in Figure 7. Produces similar spikes. The level of this spike increases as the emphasis amount increases (the ratio of emphasizing high frequencies increases).

Therefore, when the luminance signal shown in FIG. 7 is subjected to FM modulation, the FM modulator causes an inversion phenomenon due to overmodulation, such as when the black level suddenly changes to the white level, resulting in so-called "blurring". Furthermore, due to the recording and reproducing frequency characteristics of the disk 13, the level of the reproduced signal changes drastically, making it easy to cause "blurring". In order to prevent such a phenomenon from occurring, the amount of emphasis is adjusted by the pre-emphasis circuit 3a and the de-emphasis circuit 23a, but as shown in Fig. 3, the recording and reproducing frequency characteristics differ between the outer circumference and the inner circumference of the disk 13. Therefore, if the amount of emphasis is adjusted so that "wobble" does not occur at the outer circumference of the disk 13, "wobble" is likely to occur at the inner circumference. There is also "tearing" on the inner periphery.
If the amount of emphasis is adjusted to prevent blurring, no blurring will occur on either the outer or inner periphery, but the overall image quality will deteriorate, which is not optimal.

In view of the above points, the present invention provides a method for obtaining stable video signals at both the outer and inner circumferences of the disk by automatically changing the amount of emphasis depending on the recording and/or playback position in the radial direction of the disk. The purpose of the present invention is to provide a video signal recording and reproducing apparatus that can perform video signal recording and reproducing apparatus, and one embodiment thereof will be described below based on the drawings.

FIG. 8 is an overall circuit block diagram, and the same components as those shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. 27 is disk 1
A position detector 28 detects the recording and reproducing position in the radial direction of the position detector 27, and 28 is a DC voltage generation circuit that generates a DC voltage Sv according to the detection output of the position detector 27 and supplies it to the pre-emphasis circuit 3b and the de-emphasis circuit 23b. be. The position detector 27
consists of, for example, a potentiometer or the like, and is connected to the support 16. This position detector 27 is
It may be connected to the motor 14, the transfer shaft 17, or the step motor 18 to obtain a signal corresponding to the amount of transfer by the step motor 18. If the position detector 27 is composed of a potentiometer or the like and outputs a DC voltage, the DC voltage generation circuit 28 only controls the DC voltage level to the voltage required for the pre-emphasis circuit 3b and the de-emphasis circuit 23b. That's fine. Furthermore, when the output of the position detector 27 is output as digital information, it is necessary to convert it into a DC voltage using a D/A converter or the like.

FIG. 10 shows a general concrete circuit example of the pre-emphasis circuit 3a. Transistors Tr ₁ to _{Tr 3} constitute a differential amplifier circuit, and transistor Tr ₁
Bias resistors R ₁ and R ₂ and a coupling capacitor C ₁ are connected to the base of the circuit, and a video signal is inputted via the coupling capacitor C ₁ .
_C2 is a bypass capacitor. transistor
A part of the high-frequency component of the video signal input to Tr ₁ is output from the collector of transistor Tr ₃ via a high-pass filter consisting of collector resistor R ₃ , peaking coil L ₁ , and coupling capacitor C ₃ . The rest of the video signal is transferred to transistor Tr ₁
is output from the emitter of R4 through resistor _R4 , and these two outputs are combined and coupled to
Output via _C4 . Resistors R ₅ and R ₆ are bias resistors for transistor Tr ₂ , variable resistor VR ₁ is a bias resistor for transistor Tr ₃ , and resistor R ₇ is a balance resistor. By varying the potential at the midpoint of the variable resistor _VR1 , the high-frequency level of the video signal output through the high-pass filter increases or decreases, and the amount of pre-emphasis can be varied.

FIG. 11 shows a typical specific circuit example of the de-emphasis circuit 23a, and the same components as those shown in FIG. 10 are given the same reference numerals and their explanations will be omitted. In order to attenuate high frequency components of the reproduced video signal on the emitter side of the transistor Tr ₁ , a capacitor C ₅ and a resistor R ₉ are inserted. By varying variable resistor VR ₁ , capacitor C ₄
Controls the frequency characteristics (de-emphasis amount) of the reproduced video signal output through the .

FIG. 12 shows a specific circuit example of the pre-emphasis circuit 3b and the de-emphasis circuit 23b in the video signal recording and reproducing apparatus according to the present invention.
Components that are the same as those in FIG. 0 and FIG. In the conventional general pre-emphasis circuit 3a and de-emphasis circuit 23a shown in FIGS. 10 and 11, the amount of emphasis is determined by the variable resistor VR ₁ . The amount of emphasis is determined by Sv. A recorded video signal is input to the capacitor _C1 of the pre-emphasis circuit 3b during recording,
A reproduced video signal is input to the capacitor _C1 of the de-emphasis circuit 23b during reproduction. Base of transistor Tr ₃ of pre-emphasis circuit 3b and transistor of de-emphasis circuit 23b
A voltage corresponding to the disk position is inputted to the base of Tr ₃ from the DC voltage generation circuit 28, respectively.
13A and 13B show the frequency characteristics of the video signals of the pre-emphasis circuit 3b and the de-emphasis circuit 23b with respect to the voltage from the DC voltage generation circuit 28. The amount of de-emphasis of the de-emphasis circuit 23b increases as the playback position moves toward the outer circumference of the disk 13. In this manner, by changing the emphasis amount depending on the recording/reproducing position in the radial direction of the disk 13, stable recording/reproducing can be performed over the entire surface of the disk 13.

That is, when the output voltage of the DC voltage generation circuit 28 changes as shown in FIG. 9 due to the disk position detection voltage, the pre-emphasis circuit 3b:
As shown in FIG. 13A, the recording position is on disk 1.
The output from the collector of the transistor Tr ₃ of the differential amplifier circuit, that is, the amount of pre-emphasis of the high-frequency component of the video signal decreases as one goes from the outer circumference to the inner circumference of the differential amplifier circuit. Further, in the de-emphasis circuit 23b, as shown in FIG. 13B, the recording position is
From the outer circumference to the inner circumference, the output from the collector of the transistor Tr ₃ of the differential amplifier circuit, that is, the de-emphasis amount of the high frequency component of the video signal decreases. In this way, during recording, the pre-emphasis amount is made smaller on the inner circumference of the disk 13 than on the outer circumference, and during playback, the de-emphasis amount is made smaller on the inner circumference of the disk 13.
By making the inner circumference smaller than the outer circumference,
This solves the problem that because the frequency characteristics of the disc 13 are such that high frequencies are attenuated towards the inner circumference, if a large amount of emphasis (same level as the outer circumference) is applied to the inner circumference, "blurring" will occur. Yes, disk 13
Since it is possible to obtain a sufficient amount of emphasis to the extent that "tearing" does not occur over the entire surface of the
Excellent playback video signals can be obtained.

In the above embodiment, the DC voltage Sv corresponding to the recording/reproducing position in the radial direction of the disk 13 is
Although an example has been described in which the curve is configured to change linearly as shown in FIG. 9, it may be configured to change in a parabolic manner as shown in FIG. 14.

Further, in the above embodiments, an optical recording/reproducing apparatus has been described, but it goes without saying that similar effects can be obtained with a mechanical recording/reproducing apparatus.

Furthermore, in the above embodiment, an example was explained in which the recording/reproducing position in the radial direction of the disk 13 was detected using a potentiometer or the like, but a digital address signal was previously recorded on the disk 13 along the radial direction. Then play this and D-
It may be configured to perform A conversion to obtain a DC voltage.

As explained above, according to the video signal recording and reproducing apparatus according to the present invention, the amount of emphasis is controlled according to the recording and/or reproducing position in the radial direction of the disc-shaped recording medium. An appropriate amount of emphasis can be obtained over the entire surface, and therefore an excellent reproduced video signal can be obtained.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram of a conventional device, Fig. 2 is an explanatory diagram of the spectrum of each part of the circuit block shown in Fig. 1, Fig. 3 is an explanatory diagram of the recording and reproducing frequency characteristics of a disk-shaped recording medium, and Fig. 4 is an explanatory diagram of the spectrum of the FM modulation signal for recording with the low frequency conversion method, Fig. 5 is a waveform diagram of the clamp and white clip circuit, Fig. 6 is an explanatory diagram of the process of noise suppression by video emphasis, and Fig. FIG. 7 is an explanatory diagram of the output waveform of the pre-emphasis circuit, FIG. 8 is a circuit block diagram showing an embodiment of the present invention, FIG. 9 is an explanatory diagram of the output voltage of the DC voltage generation circuit, and FIG.
FIG. 11 is a circuit diagram showing a specific example of the pre-emphasis circuit in FIG. 1, FIG. 12 is a circuit diagram showing a specific example of the de-emphasis circuit in FIG. A circuit diagram showing a specific example of the circuit, FIG. 13 is an explanatory diagram of frequency characteristics of a pre-emphasis circuit and a de-emphasis circuit, and FIG. 14 is an explanatory diagram of an output voltage of a DC voltage generation circuit in another embodiment. 3b...Pre-emphasis circuit, 13...Disk (disk-shaped recording medium), 23b...De-emphasis circuit, 27...Position detector, 28...DC voltage generation circuit.

Claims (1)

[Claims] 1. A disk-shaped recording medium that rotates at a constant rotation speed and a head that records and/or reproduces video signals concentrically or spirally on the disk-shaped recording medium are relatively aligned along the radial direction of the disk-shaped recording medium. The video signal is recorded on the disc-shaped recording medium through a pre-emphasis circuit, and/or the video information recorded on the disc-shaped recording medium is reproduced to obtain a reproduced video signal through a de-emphasis circuit. In the video signal recording and reproducing apparatus configured, a position detecting means for detecting a recording and/or reproducing position in a radial direction of the disk-shaped recording medium, and a DC voltage for generating a DC voltage according to a signal from the position detecting means. 1. A video signal recording and reproducing apparatus, characterized in that a video signal recording and reproducing apparatus is provided with a generating means, and is configured to control an emphasis amount of the pre-emphasis circuit and/or the de-emphasis circuit using the DC voltage from the DC voltage generating means.