JPH01117581A - Video signal recorder - Google Patents

Abstract

PURPOSE:To prevent a beat component by a main carrier signal and a subcarrier signal from being reproduced on a picture as a thick color stripe by shifting the phase of an FM modulation signal recorded on a recording medium such as a disk carrying video information for each line and shifting the phase by each frame. CONSTITUTION:A signal frequency-dividing an H pulse period and a field inversion signal frequency-dividing a V pulse period by 1/2 respectively are inputted to an exclusive OR gate 7 and a signal inverted by one line and one field of a video signal is outputted. Thus, an output of a switch circuit 5 becomes an FM modulation signal shifted by 180 deg. by each line and each frame. A correction video signal including a correction pulse signal based on the FM modulation signal shifted by each line is supplied to the FM modulation circuit 4, resulting that the noise on the picture of the beam component due to the distortion component after FM demodulation becomes the luminance component with fine stripe. Moreover, since the waveform of the FM modulation signal is inverted for each frame, the signal is cancelled and not eminent because of the visual characteristic.

Description

[Detailed description of the invention] Technical field The present invention relates to a video signal recording device.

Background Art Recently, in order to improve the horizontal resolution of images recorded and played back on video discs (hereinafter simply referred to as LDs), FM audio carrier signals (FM audio carrier signals recorded on LDs) have been developed.
A wideband video disc (hereinafter simply referred to as SLD) is obtained by removing 2, 3, 2, 3 [MHz] and extending the high frequency range of a color composite video signal (hereinafter simply referred to as video signal) into this vacant frequency band. ) has been proposed. According to this method, it is possible to expand the band of the recorded video signal from the conventional 4.2 MH2 to about 6 MHz.

In such an SLD, if there is distortion in the formation of pits on the disk, in the reading optical system, or even in the head amplifier, beat disturbance will occur in the demodulated video signal. This beat disturbance tends to be particularly noticeable on color screens where the spectrum is concentrated, and will be explained below with reference to the drawings.

Figure 5 shows the SL when beat disturbance occurs on the color screen.
It shows the spectrum of a high frequency signal (FM modulation signal) read by a pickup (not shown) from D.
There are upper and lower sideband components (ωC±ωSC) of the color subcarrier apart from the main carrier ωC, and the beat component due to the above distortion is the frequency component ωSC.
q (2ωC-ωSC).

The color subcarrier signal ωSC and the beat component (ωC-
The frequency relationship of ωSC) is shown in FIG. The beet ingredients are
It occurs above the color subcarrier ωSC as (ωC−ωSC).

Usually the main carrier is 8.1 to 9. 3 [MHz], the frequency of this beat component (ωC - ωSC) is 3.58 [M
Hzl, it is 4.52 to 5.72 [MHzl].

In conventional LDs, this beat component is generated in the video signal band (4
However, in SLD, the video signal band is 6 [MHz], so this beat component exists within the video signal band. This causes various problems.

For example, if the phase of the beat component (ωC - ωSC) is aligned for each section equivalent to one scan of the video signal (hereinafter simply referred to as a line), the beat component will appear as a luminance signal on the screen, and a striped pattern will appear on the screen. There is a problem that appears as noise. The frequency of the fringe at this time is 4.52 to 5.72
CMHz, resulting in fine pitch brightness stripes as shown in FIG. 7(A).

Furthermore, if the phase of the beat component (ωC-ωSC) is inverted line by line, this becomes a chroma signal and causes color stripes on the screen. At this time, the chroma subcarrier is ωSC
Therefore, the frequency of color fringes due to cross modulation is (ωC−ω5
c) -ωsc-ωC-2 (IJSC, 0.94~
2.14 [MHz]. This results in relatively wide color stripes as shown in FIG. 7(A).

In this way, in the images obtained by playing the SLD, when the beat component mentioned above occurs, there is a problem in that striped noise occurs on the screen, and it can be an eyesore, especially when it appears as thick stripes of different colors on the screen. This is a problem because the high image quality inherent to SLD cannot be demonstrated.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a video signal recording device capable of suppressing beat disturbance.

In order to achieve the above object, in the video signal recording device of the present invention, an FM-modulated F
A video signal recording device for recording an M carrier signal on a recording medium, comprising: a phase shift circuit for shifting the phase of the modulated carrier signal; a separation means for separating a synchronization signal from the composite video signal; a signal selection circuit that alternately selects the FM carrier signal and the phase-shifted FM carrier signal based on the synchronization signal; The present invention is characterized by comprising a phase difference detection circuit that detects a phase difference between the output signal and the comparison reference signal, and a phase control means that controls the phase of the modulated FM carrier according to the detected phase difference.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

A video signal to be recorded on a recording medium such as an SLD is supplied to one input terminal of an adder circuit 1 and a synchronizing signal generating circuit 2. The other input terminal of the adder 1 is supplied with a variable amplitude correction pulse from a pulse amplitude modulation circuit 3 corresponding to a predetermined position on the time axis of the video signal, for example, a front porch portion of a synchronizing pulse. The adder circuit 1 superimposes the correction pulse on the video signal to obtain a corrected video signal and supplies this to the modulation input of the FM modulation circuit 4.

The FM modulation circuit 4 biases the frequency of a predetermined carrier signal using this corrected video signal, obtains an FM modulation signal, and supplies the signal to a known recording means (not shown). The recording means includes, for example, a limiter that limits the amplitude of the FM signal to obtain an on-off signal, an optical modulator that cuts off a laser beam in accordance with the on-off signal, a photosensitive recording film that forms pits with the laser beam, and the like. be done.

Further, the FM modulation signal is supplied to the other input terminal of the switch circuit 5 via one input terminal of the switch circuit 5 and a phase shift circuit 6 that shifts the phase of the signal by 180 degrees. The switch circuit 5 selects the above FM according to the output of the exclusive OR gate 7.
Either the modulated signal or its phase-shifted signal is selected and supplied to one comparison input terminal of the phase comparison circuit 8.

The synchronization signal generation circuit 2 separates the synchronization signal from the video signal and generates an H pulse synchronized with the horizontal synchronization signal, a V pulse synchronized with the vertical synchronization signal, and a composite blanking pulse (hereinafter referred to as "composite blanking pulse" synchronized with the control information area of the video signal). , simply referred to as the BLK pulse). The BLK pulse is supplied to the other comparison input terminal of the phase difference detection circuit 8. The above-mentioned H pulse is supplied to a divide-by-two circuit 9 which is constituted by, for example, a flip-flop circuit and whose output is supplied to one input terminal of an exclusive OR gate 7. The V pulse is supplied to a divide-by-two circuit 10 whose output is supplied to one input terminal of the switch circuit 13 and to the input terminal of the frequency divider circuit 11 . The output of the divide-by-2 circuit 11 is supplied to the other input terminal of the switch circuit 13. The switch circuit 13 selects either the field inversion signal of the divide-by-2 circuit 10 or the frame inversion signal of the divide-by-2 circuit 11 according to the setting signal supplied from the switch circuit 14, and selects the other input of the exclusive OR gate 7. feed at the end. The output of the exclusive OR gate 7 becomes the control input of the switch circuit 5. Circuits 5 to 7 and circuits 9 to 14 constitute a signal selection circuit.

The phase difference detection circuit 8 monitors the BLK pulse and the FM modulation signal, detects the time difference from the rising edge of the BLK pulse to the zero cross point of the rise of the FM modulation signal, as shown in FIG. A phase difference voltage conversion circuit 1 that generates a phase difference pulse with a width corresponding to the time difference.
Supply to 5.

The phase difference voltage conversion circuit 15 generates a voltage corresponding to the pulse width of the phase difference pulse and applies it to the modulation input terminal of the pulse amplitude modulation circuit 3. The pulse amplitude modulation circuit 3 generates a correction pulse with an amplitude corresponding to the voltage and supplies it to the addition circuit 1.

The addition circuit 1, the phase difference voltage conversion circuit 1, and the pulse amplitude modulation circuit 3 constitute phase control means.

Next, the operation of the device will be explained. First, the exclusive OR gate 7 is input with a signal obtained by dividing the H pulse period by 2 and a field inversion signal obtained by dividing the pulse period by 2 (or a frame inversion signal obtained by dividing the frequency by 4). The output of the OR gate 7 is a signal that is inverted every line of the video signal and every frame (or field). Whether the gate output is inverted every frame or every field is determined by the settings of the switch circuit 14. Since the output of this exclusive OR gate 7 serves as a control signal for the switch circuit 5, the output of the switch circuit 5 becomes an FM modulated signal whose phase shifts by 180 degrees for each line and for each frame (or field). ing.

FIG. 2 shows the mutual correspondence among the video signal, BLK pulse, and FM modulation signal. The frequency of the FM modulation signal at the blanking level of the video signal (corresponding to the rising position of the BLK pulse) is normally determined to be 8.1 [MHz], so for example
As shown in the figure, the phase difference of the FM modulation signal can be detected. Width Δt of the phase difference pulse generated by the phase difference detection circuit 8
indicates the phase difference between the rising edge of the BLK pulse and the FM modulation signal from the switch circuit 5, and the phase difference Δφ is Δφ−Δ1×2π 8, lXl06 (rad).

A voltage output proportional to this phase difference is obtained by the next stage phase difference voltage conversion circuit 15, and this voltage output is applied to the modulation input of the pulse amplitude modulation circuit 3, so that the correction pulse generated by the pulse amplitude modulation circuit 3 is input to the adder 1 as a pulse having an amplitude proportional to the phase difference between the FM modulation signal and the BLK pulse.

As a result, a corrected video signal in which a correction pulse is superimposed on the front porch section of the video signal is obtained. Fourth
The figure shows the relationship among the video signal, BLK pulse, correction pulse, and correction video signal.

Next, the role of the correction pulse will be explained. When the corrected video signal to which this correction pulse is added is input to the FM modulation circuit 4, the FM modulation signal FP outputted from the FM modulation circuit 4 has the input video signal as V(t) and the correction pulse as p(t). , the amplitude and width of the correction pulse are K and T, then F p −As:n (ωc is 10Ωd, I'f″U(
r) 10pCt)l dt)...(1). Here, A is a constant, ωC is a main carrier, and Ωd is a frequency deviation.

On the other hand, F when no correction pulse is added to the video signal
The M modulation signal F is F''As;n (ω(1ΩdflJ CF) dt'
J...(2) It is expressed as:

The phase change Δma of the FM modulation signal due to the insertion of the correction pulse is the difference between the phase terms in equations (1) and (2), so Δ'V−Cωct+Ωdf (V (z') +p (
z') 1dt) (ωc t+ΩdflJ (t
)dt)-ΩdfpCt)dt Since the correction pulse p (t) has one pulse width T in height for each line, ΔVtsuΩdKT (3) In other words, since ΩdST is a constant, FM The phase of the modulation signal changes in proportion to the amplitude K of the correction pulse.

As mentioned above, the amplitude of the correction pulse includes the FM modulation signal and BLK.
Since it is proportional to the phase difference Δφ with the pulse, ΔW−Δφ
By determining the amplitude K of the correction pulse so that the correction pulse has the following effect, the correction pulse acts to make the phase of the FM modulation signal output from the FM modulation circuit 4 constant after the correction pulse.

By the way, the FM modulation signal supplied to the phase comparison circuit 8 is changed to the FM modulation circuit 4 by the signal selection operation of the switch circuit 5.
The output waveform of is inverted for each line and each frame (or field).

A corrected video signal including a corrected pulse signal based on the FM modulated signal whose phase is shifted for each line is supplied to the FM modulating circuit 4, and as a result, the FM modulated signal supplied from the FM modulating circuit 4 to the external recording device is as follows. The phase is inverted for each line and each frame (or field).

The effect of doing this will be explained. First, let us consider a case in which distortion components occur when a video signal of a color image is FM modulated, subjected to the signal processing described above, and recorded on a recording medium such as a disk. The beat frequency of the distortion component after FM demodulation by a recording medium playing device (not shown) is (ωC-ωSC) as shown in FIG. ωSC is a chroma signal and is interleaved for each line (
The waveform of the chroma signal ωSC is inverted line by line).

Correspondingly, the waveform of the FM modulation signal ωC is inverted line by line by the signal processing described above, and as a result, the waveform of the beat component (ωC-ωSC) is no longer inverted line by line. Therefore, the noise on the screen due to this beat component becomes the luminance component of the fine stripes described above. Furthermore, since the waveform of the FM modulation signal is inverted for each frame (or field), the brightness and darkness of these thin brightness stripes is reversed for each frame (or field), and due to visual characteristics, they cancel each other out and become less noticeable.

Such a visual integral effect can be made to a certain extent by reversing the brightness and darkness of the stripes caused by noise on a frame-by-frame or field-by-field basis, so the switch circuit 14
Either one is selected depending on the settings.

In the embodiment, a correction pulse that is pulse amplitude modulated is used in the front porch to correct the phase of the FM modulated signal, but as is clear from equation (3), a correction pulse that is pulse width modulated is used. A correction signal component may be added to the video signal itself to provide a similar effect.

Alternatively, a configuration may be adopted in which the correction pulse is directly applied to the FM modulation circuit 4 to control the phase of the FM modulation signal.

Further, even in a PAL type LD, there is a problem in that beat interference between the color subcarrier and the main carrier occurs within the video band (eg, 2.7 to B, 5 MHz). In this case, in the phase shift circuit 4 of this embodiment, F
A similar noise suppression effect can be obtained by taking measures such as changing the phase of the M modulation signal by 900 degrees.

The present invention is also applicable to cases where a magnetic recording medium, a magneto-optical recording medium, or the like is employed as the recording medium.

Effects of the Invention As described above, the video signal recording device of the present invention shifts the phase of the FM modulated signal carrying video information and recorded on a recording medium such as a disk line by line, and further shifts the phase of the FM modulation signal for each frame (or field). Since the phase is shifted to
For example, beat components caused by the main carrier signal and subcarrier signal may be reproduced as thick colored stripes on the screen, which may occur due to distortion in the pit shape cut on an optical disc or nonlinear distortion in the demodulation circuit of a performance device. Moreover, since the brightness of fine brightness stripes caused by the beat component is reversed for each frame (or field), they are visually offset and beat interference is suppressed. Further, it is preferable that the above-mentioned signal processing is only performed when producing a recording medium such as a disk, and there is no need to modify the performance device in any way.

[Brief explanation of the drawing]

Figure 1 is a block circuit diagram showing an embodiment of the present invention, Figure 2 is a signal waveform diagram to explain each signal, Figure 3 is a signal waveform diagram to explain phase difference detection, and Figure 4 is a signal waveform diagram to explain phase difference detection. A signal waveform diagram to explain the correction pulse, Figure 5 is a diagram to explain the beat component in the FM modulation signal, Figure 6 is a diagram to explain the beat component after demodulation, and Figure 7 is the beat component. TV by
FIG. 4 is a diagram for explaining the influence on the screen. Explanation of symbols of main parts 1...Addition circuit 3...Pulse amplitude modulation circuit 4...FM modulation circuit 8...Phase difference detection circuit Applicant: Pioneer Co., Ltd.

Claims (3)

[Claims] (1) A video signal recording device that records an FM modulated signal FM modulated by a composite video signal on a recording medium, which includes a phase shift circuit that shifts the phase of the FM modulated signal, and a synchronization signal that separates the synchronization signal from the composite video signal. a separation means for generating a comparison reference signal when the composite video signal reaches a predetermined level; and a comparison reference signal generation means for generating a comparison reference signal when the composite video signal reaches a predetermined level; a signal selection circuit to select, a phase difference detection circuit to detect a phase difference between the output signal of the signal selection circuit and the comparison reference signal, and a phase control to control the phase of the modulated FM signal according to the detected phase difference. 1. A video signal recording device comprising: means. (2) The video signal recording device according to claim 1, wherein the phase control means superimposes a pulse signal having a shape corresponding to the detected phase difference on a synchronization information area of the composite video signal. . (3) The video signal recording apparatus according to claim 1, wherein the phase shift circuit shifts the phase of the FM modulation signal by 180 degrees.