JPS61265992A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To reproduce properly the phase of the high frequency component of a luminance signal subjected to the low frequency conversion and to improve a resolution by constituting such that the phase of a high frequency luminance signal is inverted when the phase relationship between the synchronous signal of a demodulated reproduction low frequency luminance signal and the high frequency component of a synchronous signal included in the high frequency luminance signal is reverse. CONSTITUTION:The titled device is provided with a phase detecting part 1 detecting the phases of the outputs of a synchronizing separator 56 and an YCF 8, pulse width discriminating part 2 detecting that the width of the output pulse exists over the prescribed time in order to eliminate influence such as a noise and a phase control part 4 which converts normally or reversely the phase of the high frequency luminance signal due to the output. The phase relationship between the synchronous signal of the demodulated reproduction low frequency luminance signal and the high frequency component of the synchronous signal included in the high frequency luminance signal is detected. When it is reverse, the phase of the high frequency luminance signal is inverted. When the phase of the high frequency luminance signal YH is reverse in such a way, it is inverted to return to its normal phase, and the phase of the high frequency luminance signal YH is equal to that of the low frequency luminance signal YL.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an apparatus for reproducing video signals recorded using a low frequency conversion method.

2. Description of the Related Art Conventional general low-frequency conversion video signal recording and reproducing apparatuses have configurations as shown in FIGS. 8 and 9, respectively. This will be explained using FIG. 7. Figure 7(a) shows an NTSG or FA signal in which the luminance signal Y and chromaticity signal C are combined.
This shows a composite color video signal such as I, but the following is an NTS
This will be explained using the C signal.

The NTSC signal is applied to input terminal θ0 in FIG. Then, a low pass filter (hereinafter referred to as LPF) of about 3 MHz is applied.
) 61 outputs only a low-frequency luminance signal YL, which is a low-frequency component of the luminance signal Y, as shown in FIG. 7(b), which is converted into a frequency modulated signal by a frequency modulator (FM modulator) (hereinafter referred to as FM signal). On the other hand, the composite color video signal that has passed through the band pass filter (hereinafter referred to as BPF) 64 is a composite of the high frequency component YH of the luminance signal Y and the carrier color signal C, as shown in FIG. 7(C). If the chromaticity signal C is divided into a subcarrier frequency fs and a sideband component c, this can be expressed as fs+fQ+YH. From this signal, only the burst signal is extracted by the burst gate 65, and the phase comparator ee and LP7671
! PLL consisting of 68 pressure controlled crystal oscillators a (vxo)
(phase-locked loop) to obtain a continuous wave of burst frequency and subcarrier frequency fs, and from the horizontal synchronization signal fH extracted from the composite color video signal by the synchronization separator element 1, the phase comparator 72. L
A low frequency subcarrier f1 is obtained by a PLL consisting of a P F 73° voltage controlled oscillator (hereinafter referred to as VCO) and a frequency divider 75, and a signal obtained by a balanced modulator (hereinafter referred to as BM) 69 is fs+f+ This and the output of the BPF 64 are input to the 8M70 to obtain a low frequency converted signal centered on the low frequency subcarrier f. The composite of this signal and the FM signal is shown in Figure 7 (
d), this is amplified by the recording amplifier 63, and the head 6
Step 1 records on a magnetic tape or the like.

FIG. 9 is a block diagram of the playback side, in which the playback signal obtained by the head 51 is amplified by a preamplifier 62, and then filtered through a Neubus filter (hereinafter referred to as HPF) 63 and an LP.
Each signal is divided into an FM signal and a low frequency conversion signal by F6. The FM signal is amplitude limited by a limiter 64 to suppress amplitude fluctuations, and demodulated by a 7M demodulator 66 to obtain the original low-band luminance signal YL. However, it includes jitter Δ in the drive system of the magnetic tape, etc.

On the other hand, the low frequency conversion signal is returned to the carrier color signal C centered on the original subcarrier fs by the output of the local oscillator 96 and the chromaticity processing unit (PC) s, and is combined with the low frequency luminance signal YL. The output terminal 76 receives the original composite color video signal.
can get. At this time, the APC 9 operates to stabilize the phase of the subcarrier so that colors can be reproduced correctly on the receiver side. In other words, in &Pa9, 8
From the signal that has undergone frequency conversion with M91 and passed through BPF92, only the burst portion is extracted with burst gate 93,
The output of the subcarrier solid-state oscillator 96 is phase-compared with the phase comparator 94, and the obtained error signal is smoothed by the LPF 96 and drives the VCO 97.

The output of the VCO 97 is the frequency of the low subcarrier f1 plus an error, which is the frequency of the subcarrier fixed oscillator 9.
The output of 6 is frequency-converted by 8M98, and the low frequency conversion signal is frequency-converted by 8M91. Then, a carrier color signal fs-37'0 +YH is obtained as shown in the following equation.

(fs+f1+Δ)-(f+fc-YH+Δ)=
f s + f c + Y H Since this loop performs a negative feedback operation to eliminate errors, a signal without jitter components is obtained at the output. This is generally called the human PC loop. These are described in Japanese Patent Publication No. 60-14852.

Now, since the jitter of the carrier color signal has been removed, the colors are correctly reproduced, and the FM demodulated low-band luminance signal YL+Δ
Although it contains jitter, it can be tracked on the receiver side, so the image can be reproduced.

Incidentally, jitter has been removed from the high-frequency luminance signal YH included in the carrier color signal band signal by frequency-converting the low-frequency conversion signal, but the receiver tracks the jitter of the low-frequency luminance signal YL+Δ. Therefore, it appears to be distorted, as if there is jitter, and the reproduced high-frequency luminance signal YH
Not being able to make full use of it. A method of making use of this high-range luminance signal YH is also described in JP-A-57-89387-8, but it requires setting the frequency of the carrier wave for frequency conversion to be an integral multiple of the synchronization signal. As described above, this method cannot be applied to cases where the subcarrier fs of the NTSG signal is used as the carrier.

Problems to be Solved by the Invention When using the subcarrier fs of the NTSC signal, (1
), there are two possible phase relationships with the synchronization signal, so on the one hand, the high-frequency luminance signal Yl (and the low-frequency luminance signal YL
Even if the phases of YH and YL are adjusted and matched, if the other phase relationship occurs, the phases of YH and YL will be shifted by 18o0.

fs” fH (1) The present invention has been made in view of the above points, and it is possible to obtain a reproduced composite color video signal in which the high-frequency luminance signal YH and the low-frequency luminance signal YL are in phase with each other with a simple configuration. The purpose of the present invention is to provide a video signal reproducing device that can perform the following functions.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention always has a constant phase relationship between the synchronization signal and the luminance signal, and as described above, the phase relationship between the synchronization signal and the carrier wave for frequency conversion is twofold. Focusing on the fact that there are only two types, we have developed a phase detection unit that detects the phase relationship between the synchronization signal of the demodulated reproduced low-band luminance signal and the high-frequency component of the synchronization signal included in the high-band luminance signal, and its output pulse. A pulse width discriminator that detects that the width of the signal is longer than a predetermined time, and a phase control section that inverts or normalizes the phase of the high frequency luminance signal depending on the output of the pulse width discriminator, and generates a synchronization signal for the demodulated reproduced low frequency luminance signal. If the phase relationship between the high-frequency component and the high-frequency component of the synchronization signal included in the high-frequency luminance signal is reversed, the phase of the high-frequency luminance signal is inverted. The signal is also made so that its low-frequency and high-frequency components are in phase.

Effect of the Invention With the above-described configuration, the present invention can reproduce a composite color video signal without shifting the phase of the reproduced luminance signal and the high-frequency components of the low-frequency converted luminance signal, and the luminance signal included in the low-frequency converted signal can be reproduced. It is possible to effectively restore the high frequency components of the image and dramatically improve the resolution.

Embodiment FIG. 1 is a block diagram showing an embodiment of the video signal reproduction system of the present invention. In FIG. 1, the same components as in FIG. 9 are given the same numbers, and their explanations will be omitted.

Nitsunomu PCs 901 and 902 in Figure 1 are APCs in Figure 9.
It has the same configuration as i9.

The case of an NTSG signal will be explained with reference to FIG.

The signal passing through LPF6 is sent to Mu PC901 and Mu PC9.
02. In AP-Ce O2, as in FIG.
CF) 7 outputs only the chromaticity signal. As is well known in this method, since the chromaticity signal and the luminance signal have a frequency interleaved relationship as shown in FIG. 6(b),
) can easily pass only the chromaticity signal.

On the other hand, in the human PC 901, from the output of the 7M demodulator 66,
PLL based on the horizontal synchronization signal obtained by the synchronization separator 66
The frequency of the subcarrier fs is 227.5 times that of the horizontal synchronization signal by the 466 multiplier 67° 1/2 frequency divider 68, which is composed of the following:
Frequency conversion is performed with jitter, and the same figure (2L)
Luminance signal comb filter (
Only the luminance signal is extracted by YCF)8. By combining these two signals and the low-frequency luminance signal YL that is the output of the 7M demodulator 66, the output terminal 76 receives a jitter-free carrier color signal, and both the high-frequency component and the low-frequency component of the luminance signal. A luminance signal with the same jitter is obtained, and when viewed on a receiver, the color is correctly reproduced because the chromaticity signal has no jitter, and it follows the jitter of the luminance signal, so the high-frequency range of the luminance signal is You will be able to see it without wavering.

Furthermore, a phase detection section 1 that detects the phase of the output of the synchronous separator 56 and the output of the YCF 8, and a pulse width discrimination section that detects that the width of the output pulse is longer than a predetermined time in order to eliminate the influence of noise etc. s2 and a phase control section 4 that inverts or normalizes the phase of the high-frequency luminance signal according to its output, and controls the synchronization signal of the demodulated reproduced low-frequency luminance signal and the high-frequency component of the synchronization signal included in the high-frequency luminance signal. By inverting the phase of the high-frequency luminance signal when the phase relationship between the high-frequency component and the high-frequency component is opposite, it is possible to match the phases of the low-frequency component and the high-frequency component of the luminance signal.

This will be further explained with reference to FIGS. 2, 3 and 4. FIG. 2 shows an embodiment of the phase adjustment section of the present invention, and FIGS. 3 and 4 are waveform diagrams of each part in FIG. 2. Third
Figure (a) shows the output of the FM demodulator 56, and when this is passed through the synchronous separator 6θ, it becomes the output shown in figure (C), which becomes the trigger input for the flip 70 tube 12.

The output of the YCFs is shown in the figure ('b), and is passed through the time adjustment section 11 in Fig. 2 to match the synchronization signal in time as shown in Fig. 3 (d), and then input as data to the 7-lip-flop 12. . The flip-flop 12 is a phase detector, and when it is normal, the output is "0" as shown in Figure 3 (a), and the output is "0" as shown in the figure (θ), and when the phase is reversed, it is as shown in the figure (b). As in, it becomes “1”.

In FIG. 4, the output of the phase detection section 1 is shown in FIG. The voltage of the integrating circuit is the Schmitt trigger circuit 26
(g) beyond the threshold voltages v1 and v2 of
become that way. And an inverting amplifier 41. The phase control section 4, which is comprised of a changeover switch 42, inverts or rotates the phase of the high-frequency luminance signal to return it to the normal phase. Even if the phase detection section 1 malfunctions due to noise etc.,
The voltage of the integrating circuit is the threshold voltage V, , V2
not exceed.

In this way, when the phase of the high frequency luminance signal YH is reversed, it is inverted and returned to the normal phase, so that the phases of the high frequency luminance signal YH and the low frequency luminance signal YL match.

FIG. 5 shows an example using a time base collector 80 with a subcarrier feedback terminal, which is a method of inputting an external carrier wave to the PCs in a conventional circuit. In this case, both the luminance signal and the carrier color signal with jitter are outputted to the output terminal 76, and the jitter is removed by the connected time base collector 8o to obtain a jitter-free composite color video signal. Even in this case, since the carrier wave for frequency conversion can take two different phases, it is necessary to arbitrarily determine the phase, and the present invention can be applied.

Phase detection section 1, pulse width discrimination section 2, and phase control section 4
has the same configuration as in FIG. 1 and performs the same operation, and can also match the phases of the high-range luminance signal YH and the low-range luminance signal YL.

Effects of the Invention As described above, according to the present invention, with an extremely simple configuration, the high-frequency components of the low-frequency converted luminance signal are reproduced with correct phase, and the resolution is dramatically improved, making it practical. To,
Extremely useful.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a video signal reproducing device according to an embodiment of the present invention, FIG. 2 is a detailed block diagram of a portion of FIG. 1, and FIGS. Voltage waveform diagram, Figure 6 is a block diagram showing a video signal reproducing device in another embodiment of the present invention, Figure 6 is a diagram showing the relationship between the characteristics of the comb filter and frequency interleaving, and Figure 7 is the frequency of each signal. FIG. 8 is a block diagram showing a conventional video signal recording device, and FIG. 9 is a block diagram showing a conventional video signal reproducing device. 1... Phase detection section, 2... Pulse width discrimination section, 4... Phase control section. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 (a)
([1) Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] A carrier wave is frequency-modulated using a low-frequency conversion signal obtained by frequency-converting a carrier color signal band signal separated from a composite color video signal to a low frequency band, and a luminance signal separated from the composite color video signal by a low-pass filter. The reproduction carrier color signal band signal obtained by frequency converting the reproduced low-pass conversion signal separated from the reproduced signal obtained by reproducing it into the original frequency band, and the reproduced In a video recording and reproducing device that obtains a reproduced composite color video signal by mixing a reproduced luminance signal obtained by demodulating a reproduced frequency modulated signal separated from the signal, a synchronization signal of the reproduced luminance signal and a reproduced carrier color signal band are mixed. a phase detection unit that detects a phase difference with a high-frequency component of a synchronization signal included in the signal; a pulse width discrimination unit that detects that the pulse width of the output of the phase detection unit is longer than a predetermined time; By providing a phase control section that inverts or normalizes the phase of the high-frequency luminance signal according to the output of the width discrimination section, the high-frequency component of the luminance signal existing in the carrier color signal band can be effectively restored, and A video signal reproducing device characterized by being in phase with a reproduced luminance signal.