JPH0760565B2 - Video signal playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial field B Outline of the invention C Conventional technology (Fig. 3) D Problems to be solved by the invention (Figs. 4 and 5) E Means for solving problems F Action G Implementation Example (FIGS. 1 and 2) H Effect of the Invention A Field of Industrial Application The present invention relates to a video signal reproducing device, and is particularly suitable for application to a video disc player of an optical disc system.

B. SUMMARY OF THE INVENTION The present invention relates to the above video signal from a recording medium in which an FM-modulated video signal and a low-frequency modulated signal modulated to a lower frequency band than the band of the video signal after modulation are combined and recorded. In a video signal reproducing device for reproducing and demodulating and outputting
The carrier frequency component of the low frequency modulation signal in the reproduction signal from the recording medium and the carrier frequency component of the low frequency modulation signal in the demodulated video signal are synchronously detected, and the low frequency modulation signal of the reproduction signal is detected by this synchronous detection output. By adjusting the level of the carrier frequency component and adding it to the demodulated video signal in anti-phase, and by adjusting the phase of the signal when performing synchronous detection and addition, the low frequency band of the demodulated video signal is adjusted. The spurious noise component based on the modulation signal is surely removed so that a good image can be obtained.

C Prior Art In the optical disc system, as shown in FIG. 3, the white peak frequency f _WH of the video signal in the standard television signal is 9.3 [MHz] and the sync chip frequency _SYN is 7.6 [MH].
z] FM modulation, and (modulated video signal is VID
FM), and FM-modulates the audio signal of the first channel so that the center frequency f _A1 is 2.3 [MHz] and the frequency deviation is 100 [KHz], and the audio signal of the second channel is center frequency. f _A2 is 2.8 [MHz], frequency deviation is 100
After performing FM modulation so that it becomes [kHz], adding these FM-modulated signals VIDFM, AFM1, and AMF2, converting them into pulse signals with a limiter and recording them as unevenness representing the pulse width on the video disk. ing.

D The problem to be solved by the invention is that, when the recorded information is picked up by the optical head from the video disk thus recorded in the video disk player, the spurious noise component as shown by the broken line in FIG. f _V ± f _A , f _V ± 2f _A , f
_v ± 3f _A , 2f _A , 3f _A ... may occur (note that
f _A represents the carrier frequency f _A1 of the first channel audio signal AFM1 or the carrier frequency f _A2 of the second channel audio signal AFM2). Some of these spurious noise components are, for example, 2f _A , 3f _A and f _V ± f _A components
Since it occurs within the band of the FM-modulated video signal VIDFM, even if the FM-modulated audio signal AFM is removed from the playback signal RF to take out the video FM signal VIDFM, and then demodulate to obtain the video signal VID. As shown in FIG. 5, a spurious noise component SP was generated.

Especially, in the reproduced signal RF, frequency components SPN and SPP of f _v ± f _A
Takes a large value, the spurious noise component SP of the carrier frequency f _A corresponding to that component becomes large in the modulated video signal VID, and conventionally, when the reproduced image is significantly deteriorated by the spurious noise component SP. I got it.

The spurious noise component is considered to be generated by the non-linearity of each circuit and element (for example, limiter) on the recording side and the reproducing side, but it is actually generated by the video disk and does not occur. It is difficult to prevent the occurrence on the local video disk player.

Therefore, it is conceivable to remove the generated spurious noise component SP by a noise canceller, but if this is done, the same frequency as the spurious noise component SP (2.3 [M
The video signal VID of Hz] and 2.8 [MHz]) is also removed, and in this case, the image is inevitably deteriorated.

The present invention has been made in view of the above points, and provides a video signal reproducing apparatus capable of obtaining a clear image even when a spurious noise component occurs in a video signal because an audio signal is recorded. Is what you are trying to do.

E Means for Solving the Problems In order to achieve the above object, the present invention is a method in which an FM-modulated video signal and a low-frequency modulated signal which is modulated in a lower band than the band of the video signal after modulation are combined. In a video signal reproducing apparatus for reproducing and demodulating a video signal from a recorded recording medium 2 and outputting the video signal, a video signal demodulating unit 1 for separating and demodulating a video signal VID from a reproduced signal RF from the recording medium
0, the first filters 32 and 42 for separating the signal components RFA1 and RFA2 having the same frequency as the carrier frequency of the low frequency modulation signal from the reproduction signal RF, and the carrier frequency of the low frequency modulation signal from the demodulated video signal VID. Same frequency signal components VIDA1, V
The second filters 30 and 40 for separating the IDA2, the signal components RFA1 and RFA2 from the first filters 32 and 42, and the second filter 3
Spurious noise component C included in the video signal VID after demodulation by synchronously detecting signal components VIDA1 and VIDA2 from 0 and 40
Synchronous detection circuits 31 and 41 that detect ON1 and CON2, and playback signal R
A level adjustment circuit 35 that adjusts the levels of signal components RFA1 and RFA2 having the same frequency as the carrier frequency separated from F based on the detection signals CON1 and CON2 from the synchronous detection circuits 31 and 41.
45 and the level adjustment circuit 35, 45 after demodulation and for the video signal VID
Adder circuit 22 for obtaining the output video signal VIDOUT by adding the correction signals S35, S45 from the
And and or phase detection of the signal components RFA1, RFA2 and or VIDA1, VIDA2 from the second filter 32, 42 and or 30, 40, the signal RFA1 when performing synchronous detection and addition based on this detection result PCON, RFA2, VIDA1, VIDA2, and S35, S45,
Phase adjusting units 36 to 39 for adjusting the phase of the VID are provided.

F-action Video signal VID has the same frequency components VIDA1 and VIDA2 as the carrier frequency of the low-frequency modulated signal, as shown in FIG. 5, in addition to the original component of the video signal VID, spurious noise component SP applied to the low-frequency modulated signal AFM Mixed. Since this spurious noise component SP is caused by the low frequency modulation signal AFM,
It has the same phase as the low-frequency modulation signal AFM in the reproduction signal RF shown in FIG.

Therefore, in the present invention, the second frequency components VIDA1 and VIDA2 that are the same as the carrier frequency of the low-frequency modulated signal from the video signal VID are used.
Filters 30 and 40 of the same frequency component RFA1 and RF from the reproduction signal RF to the carrier frequency of the low frequency modulation signal.
A2 is separated by the first filters 32 and 42, and both frequency components VIDA1 and RFA1 and VIDA2 and RFA2 are synchronously detected by the synchronous detection circuits 31 and 41 to detect the spurious noise component SP, and the detection signal CON1 Level adjustment circuit 3 based on CON2
The spurious noise component SP is canceled from the video signal VID by the number 5 and 45 and the adder circuit 22.

Further, in the present invention, the phase adjustment units 36 to 39 adjust the phase of the signal at the time of performing synchronous detection and addition, so that the precision of the cancellation of the spurious noise component SP is improved.

As a result, a good reproduced image can be obtained.

G Embodiment One embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, a reproduction signal RF picked up by an optical head 3 from a video disk 2 which is rotationally driven by a motor 1 is given to a video signal demodulation section 10.

In the video signal demodulation unit 10, a video FM signal VIDFM (for example, 3.5
[MHz] to 15 [MHz]) are separated. This video FM signal
VIDFM is FM demodulated in the demodulation circuit 12, the noise component in the predetermined band is removed through the low pulse filter 13 and is given to the first input terminal a of the switching circuit 14, and the video FM signal VI
DFM is F in the second demodulation circuit 16 via the 1H delay circuit 15.
M is demodulated and applied to the second input terminal b of the switching circuit 14 via the low-pass filter 17.

The dropout detection circuit 18 detects the dropout of the video FM signal VIDFM, and when it detects it, the switching circuit 14
Is supplied with a switching control signal COM to switch to the second input terminal b, and this period is replaced with the video signal VID which is one horizontal scanning period before 1H. The video signal VID thus obtained is provided to the video signal correction section 20.

In the video signal correction unit 20, the bandpass filter 30
(Center frequency 2.3 [MHz]) is the same frequency component as the audio frequency of the first channel from the video signal VID (hereinafter simply referred to as audio frequency component) VI
DA1 is separated and given to the synchronous detection circuit 31. Synchronous detection circuit 3
1 also has a bandpass filter 32 (center middle frequency 2.3
After being separated from the reproduction signal RF at [MHz]), the delay circuit 33 provides the audio channel frequency component RFA1 of the first channel delayed in phase with the audio channel frequency component VIDA1.

The synchronous detection circuit 31 synchronously detects the audio signal frequency component VIDA1 separated from the video signal VID and the audio signal frequency component RFA1 separated from the reproduction signal RF, and the output signal CON1 is gain-controlled via the low-pass filter 34. It is given to the level adjusting circuit 35 having an amplifier circuit configuration.

Here, the audio carrier frequency component VIDA1 separated from the video signal VID includes a spurious noise component SP in addition to the original video signal having the frequency as shown in FIG. This spurious noise component SP is in phase with the audio FM signal AFM (Fig. 4). In addition, the audio frequency component RFA1 separated from the playback signal RF
Represents the audio FM signal AFM shown in FIG. Thus, when the video signal VID has a spurious noise component, the synchronous detection circuit 31 outputs the detection signal CON1 according to the value.

The level adjusting circuit 35 adjusts the level of the audio carrier frequency component RFA1 according to the value of the detection signal CON1 so as to be the same level as the spurious noise component included in the video signal VID, and supplies it to the adding circuit 22. The adder circuit 22 is a video signal VID given through the delay circuit 21 for timing adjustment.
Then, the correction signal S35 from the level adjusting circuit 35 is added in the opposite phase, and the spurious noise component in the video signal VID is canceled to output the output video signal VIDOUT.

Similarly, the video signal correction unit 20 has a configuration for correcting the audio channel frequency component of the second channel, which is similar to the configuration for correcting the audio channel frequency component of the first channel. That is, from the video signal VID, the frequency component VIDA2 of the audio channel of the second channel
(2.8 [MHz]) separating bandpass filter 40, bandpass filter 42 separating the second channel audio carrier frequency component RFA2 from the reproduction signal RF, delay circuit 43 delaying the audio carrier frequency component RFA2, second Both channels of the channel Audio frequency components VIDA2, R
Synchronous detection circuit 41 that synchronously detects FA2, its synchronous detection output C
Low-pal filter 44, which removes the video signal component of ON2,
The level adjusting circuit 45 adjusts the level of the audio carrier frequency component RFA2 according to the value of the synchronous detection signal CON2 and supplies it to the adding circuit 22.

In the configuration of FIG. 1, the reproduction signal RF picked up from the video disk 2 by the head 3 is given to the video signal demodulation unit 10 and the video signal correction unit 20, and the reproduction signal RF is reproduced.
RF is demodulated into a video signal VID in the video signal demodulation unit 10 and given to the video signal correction unit 20.

If this demodulated video signal VID contains spurious noise components, audio frequency components RFA1 and RFA2 separated from the reproduction signal RF and audio frequency components VIDA1 and VID separated from the video signal VID
There is a component in phase depending on the spurious noise component with A2, and accordingly, the detection signal CO with a large value from the synchronous detection circuit 31
N1 and CON2 are output.

According to the detection signals CON1 and CON2, the audio carrier frequency components RFA1 and RFA2 separated from the reproduction signal RF are adjusted to be equal to the level amount of the spurious noise component included in the video signal VID, and the addition circuit 22 Thus, the spurious noise component is canceled from the video signal VID in the adder circuit 22 and output.

On the other hand, if the video signal VID does not contain spurious noise components, the separated audio carrier frequency components RFA1 and RFA2 from the playback signal RF and the video signal VI
Separating from D Audio frequency component VIDA1, VIDA
Since there is almost no common-mode component between 2 and
1 and CON2 are almost zero. Therefore, the level adjustment circuits 35 and 4
The correction signals S35 and S45 from 5 also become almost zero, and the video signal V
The ID is transmitted as it is as the output video signal VIDOUT.

According to the circuit of FIG. 1, when the video signal VID includes a spurious noise component, the spurious noise component can be canceled to obtain a good image, and the spurious noise component is included. If not, the video signal VID can be output as it is, and a good image can be maintained without removing the original video signal VID as in the conventional case. Therefore, a good image can be obtained for various video disks from a video disk in which no spurious noise component appears to a video disk in which a spurious noise component is very large.

FIG. 2 shows the configuration for forming the correction signal S35 of the audio channel frequency component of the first channel in the video signal correction unit 20. The configuration for forming the correction signal S45 of the audio channel frequency component of the second channel has the same configuration, and the description thereof will be omitted.

In FIG. 2, a closed loop for controlling the phase of the correction signal S35 is formed. That is, the correction signal S35 from the level adjustment circuit 35 is transmitted through the π / 4 phase shift circuit 36 to π /
The phase is shifted by 4 and supplied to the phase detection circuit 37. The phase detection circuit 37 is also supplied with the audio frequency component VIDA1 of the video signal VID, and the phase detection circuit 37 outputs the correction signal S35.
And an audio carrier frequency component VIDA1 are phase-detected, and the phase difference output (voltage signal) PCON1 is given to a variable delay circuit 39 via a low-pass filter 38.

The variable delay circuit 39 is inserted between the band pass filter 32 and the level adjusting circuit 35 instead of the delay circuit 33 and delays the audio signal frequency component RFA1 of the reproduction signal RF according to the phase difference output PCON to adjust the level. Is designed to give to.

In the configuration of FIG. 2, the correction signal S35 and the video signal V
If the audio component frequency component VIDA1 in the ID is in phase, the phase detection circuit 37 will detect both signals with a phase difference of π / 4, and therefore the phase difference output PCON will be almost zero. Frequency component
RFA1 is supplied to the level adjusting circuit 35 without being delayed.

On the other hand, if there is a phase difference between the correction signal S35 and the audio carrier frequency component VIDA1, a phase difference output PCON corresponding to the phase difference is obtained from the phase detection circuit 37, and according to this phase difference output PCON. The variable delay circuit 39 delays the audio carrier frequency component RFA1 and thus controls the correction signal S35 and the audio carrier frequency component VDA1 in the video signal VID to be in phase.

Therefore, according to the circuit of FIG. 2, the adder circuit 22 (first
The phase is controlled so that the phase of the spurious noise component in the video signal VID added in the figure) and the phase of the correction signal S35 are opposite to each other, so compared to the addition circuit of FIG.
It is possible to obtain a good image in which the noise component can be more reliably canceled. In addition, both audio carrier frequency components RFA1, which are synchronously detected by the synchronous detection circuit 31,
It means that VIDA1 is controlled to be in phase,
The spurious noise component can be accurately detected.

In the above embodiment, the video signal VID and the correction signal S
Although the video signal VID is delayed by the delay circuit 21 when adding 35 and S45 in opposite phase, the correction signals S35 and S45 are actually used depending on the elements constituting the circuit.
May lead the video signal VID, and in that case, a delay circuit may be inserted in the next stage of the level adjusting circuits 35 and 45.

Further, in the above embodiment, the reproduction signal from the video disc in which the first channel audio signal and the second channel audio signal are recorded as the low frequency modulation signal recorded in the low frequency band of the FM-modulated video signal. However, the present invention is not limited to this, and further, for example,
It can also be applied to the one that processes a reproduction signal from a video disk in which a signal modulated in a low frequency range such that a carrier frequency is reproduced and demodulated within the band of a video signal VID like a PCM audio signal is recorded.

〔The invention's effect〕

As described above, according to the present invention, the spurious noise component based on the carrier frequency of the low frequency modulation signal included in the demodulated video signal is the carrier frequency component included in the reproduction frequency and the carrier frequency component of the video signal. The spurious noise component is reliably removed without deteriorating the image quality by providing the phase adjustment unit that detects and cancels by the synchronous detection of and also adjusts the phase of the signal when performing the synchronous detection and cancellation. It is possible to obtain a video signal reproducing device capable of

[Brief description of drawings]

1 and 2 are block diagrams showing an embodiment of a video signal reproducing apparatus according to the present invention, and FIGS. 3 to 5 are schematic diagrams showing frequency spectra for explaining the drawbacks of the conventional apparatus. 2 ... Video disc, 3 ... Optical head, 10 ... Video signal demodulation unit, 20 ... Video signal correction unit, 22 ... Addition circuit, 30, 32, 40, 42 ... Band pass filter, 31, 41 …
… Synchronous detection circuit, 35, 45 …… Level adjustment circuit, RF …… Playback signal, VID …… Video signal, S35, S45 …… Correction signal, V
IDOUT: Output video signal.

Claims (1)

[Claims] 1. A video signal is reproduced and demodulated from a recording medium in which an FM-modulated video signal and a low-frequency modulated signal which is modulated to a lower frequency band than the modulated video signal are combined and recorded. In the video signal reproducing apparatus that outputs the video signal, a video signal demodulating unit that separates and demodulates the video signal from the reproduction signal from the recording medium, and a signal having the same frequency as the carrier frequency of the low frequency modulation signal from the reproduction signal. A first filter for separating the components, a second filter for separating a signal component having the same frequency as the carrier frequency of the low-frequency modulated signal from the demodulated video signal, and a signal component from the first filter. A synchronous detection circuit for synchronously detecting a signal component from the second filter and detecting a spurious noise component included in the demodulated video signal, and the reproduction signal. The level adjustment circuit that adjusts the level of the signal component of the same frequency as the carrier frequency separated from the above based on the detection signal from the synchronous detection circuit, and the correction signal from the level adjustment circuit to the demodulated video signal. An adder circuit for adding in an opposite phase to obtain an output video signal, phase detection of the correction signal and the signal component from the first and / or second filters, and the synchronous detection and the addition based on the detection result. A video signal reproducing device, comprising: a phase adjusting unit that adjusts the phase of a signal when performing.