JPS6119591Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a SECAM signal recording device, particularly
When performing high-density H alignment recording of SECAM signals for each field using an azimuth recording method, etc., after converting the chroma signal into low-frequency subcarriers having different 1/4f _H phases for each adjacent field, for example, In a SECAM signal magnetic recording device that records the signal mixed with the FM luminance signal, the phases of the low-range color subcarrier signals are aligned in advance, and the low-range color subcarrier signals recorded on adjacent tracks are interleaved with each other. By keeping the record as much as possible to eliminate the effects of crosstalk during playback, it is possible to record with good color reproducibility.
The purpose is to obtain a SECAM signal magnetic recording device. It is called the so-called β method or VHS method.
The azimuth recording method used in VTRs uses magnetic heads with different magnetic gaps with different inclinations, without providing a guard band between adjacent recording tracks.
Alternatively, it is a method in which signals are recorded sequentially, for example, in units of one field, with partial overlap, and in the high frequency range, the azimuth loss of the magnetic head is effectively used, and crosstalk between adjacent tracks is practically eliminated. can do. However, in the region of low-range color subcarrier signals, the influence of crosstalk cannot be avoided because the azimuth loss with respect to the reproduced signals of adjacent recording tracks is insufficient. For this reason, a so-called H alignment recording method is adopted in which the horizontal synchronization signals of signals recorded on adjacent recording tracks are aligned, and the phases of the subcarriers of the chroma signals to be low frequency converted are mutually adjusted to 1/ _4fH. (However, f _H is the frequency of the horizontal synchronization signal) By shifting the phase of the subcarrier of the restored chroma signal during reproduction, the signal that should originally be reproduced in the reproduced signal is in the same phase relationship, and the crosstalk signal is The crosstalk can be reduced by selecting the frequency of the idling signal so that it has an opposite phase every 1H, and passing it through a comb-type filter equipped with a 2H delay line (where H is the horizontal scanning time). It is conceivable to adopt a method of removing only the By the way, in the SECAM signal, as is well known, the color signal is line sequential. For example, in the n-th scanning line, the (B-Y) signal is generated with 272f _H as the FM subcarrier, and in the (n+1)th scanning line, the (B-Y) signal is , 282f _H as subcarriers, (RY) signals are transmitted alternately. The FM modulator on the transmitting side is driven by start and stop for each line, and each FM signal is 1H.
Since it has a phase correlation with the previous signal, its frequency distribution is discrete, and basically the above-mentioned interleaved recording method can be used. However, in the SECAM signal, the phase of one color subcarrier in a set of three scanning lines is set, for example, 0, 0, π( π, π, 0). Therefore, the long-term average SECAM
The frequency spectrum of the signal is distributed at an interval of f _H /3, but in addition to the fact that the color difference signals transmitted alternately on the scanning lines are distributed at an interval of f _H /2, the frequency spectrum of the signal is eventually distributed at an interval of 1/6 f _H It will be distributed as follows. Record and play back such signals, and remove the crosstalk.
Although it is theoretically conceivable to adopt a method of removing the light using a comb-type filter having a 6H delay line, it is impractical due to poor color reproducibility and fidelity. In view of this, the present invention has been developed based on the above-mentioned recording method, and has an improved circuit configuration for recording with the subcarriers aligned in phase during the process of low-frequency conversion of the chroma signal in the SECAM signal. This is what we propose. The applicant filed an application on July 12, 1972 for a SECAM signal recording device that takes into account the above points. The outline is as follows. Utilizing the fact that the phase of the unmodulated carrier in the SECAM signal is switched and transmitted as 00π, (or ππ0) like the chroma signal, the first and second This switching phase is reproduced in the output of the oscillator circuit, and the output is
The output of the bistable multi-circuit triggered by the horizontal synchronization signal of the signal and reset by the output of the FM detection circuit is applied to the frequency conversion circuit for controlling the electronic switch 7 and generating the idling signal. The color order and switching phase of the output of the oscillator are determined by the color order of the chroma signal (for example, D _B ', D _R ', D
_B ′, D _R ′...) and the switching phase (00π,...) are assumed to match exactly. Therefore, in any period, the switching phases of the (low-band converted) subcarrier signals in the low-band converted chroma signal are canceled out and all become in phase. This low-frequency conversion signal V _SL is applied to the magnetic head H in a frequency-multiplexed form with a luminance signal component which is separately FM-modulated, and is recorded on the magnetic tape T. The above-mentioned embodiment has the advantage that it has a simpler configuration than the conventional circuit, and has better color reproducibility and reliability to some extent, but the non-modulated carrier has the same low-frequency conversion frequency for each line. Therefore, in the reproduction system, it is essential to apply the outputs of the 272f _H and 282f _H oscillators as inputs to the up-conversion frequency conversion circuit in accordance with the order of the color difference signals for each line. For this reason, a configuration is adopted in which a field ID (discrimination) signal is extracted from the output restored by up-conversion, and the bistable circuit is reset using the FM identification output. There is no means for correcting malfunctions caused by deletion of the field, and the drawback is that accurate color reproduction cannot be achieved in that field section. From this point of view, when recording SECAM signals,
It is preferable to convert the frequency difference between the FM modulation frequencies 282f _H and 272f _H and record it. The present invention has been improved by taking these points into consideration. The main block diagram of the embodiment (recording system) shown in FIG. 1 will be explained below. This block diagram is basically
A chroma signal separation circuit 10 separates a chroma signal (color difference FM signal) from a SECAM signal, the separation output is used as one input, and the output of the idling signal generation circuit 30 is used as another input, and the chroma signal is divided into (44+1/ 8) It is composed of a first frequency conversion circuit 20 that converts into a low frequency color difference FM signal of _fH or (44-1/8) _fH . The idling signal generation circuit 30 includes a non-modulated carrier separation circuit 31 that separates a non-modulated carrier component for an achromatic level reference which is inserted for approximately 4.5 μsec from the pack port of the horizontal synchronizing signal to the beginning of the image signal; As shown in FIGS. 3A and 3B, a bandpass filter 32 extracts only the energy component in the vicinity of 282f _H from the frequency spectrum component of the unmodulated carrier component, a limiter 33 regulates the output at a constant level, and An injection type oscillation circuit 34 which takes the limiter output as input, allows a clap type or ringing type, and is tuned to 282f _H , and uses the horizontal synchronization signal in the SECAM signal as a reference input, and has (44 + 1/8) f _H for each field. , or a PLL circuit 35 which performs phase-locked oscillation at a frequency of (44-1/8) _fH , and a circuit which inputs the output of the PLL circuit and the output of the injection type oscillation circuit 34 and converts it into a beat-up idling signal. It is composed of a two-frequency conversion circuit 36. A delay circuit 40 is inserted between the chroma signal separation circuit 10 and the first frequency conversion circuit 20 to compensate for the delay characteristics of the bandpass filter 32 in the idling signal generation circuit, thereby preventing color shift, blurring, etc. prevent. Therefore, the frequency spectrum of the above unmodulated carrier is However, WO: carrier frequency WH: horizontal frequency (=2π/T _H ) an=2/nπsin nπα α=τ/T _H τ: According to the width of the unmodulated carrier, under the condition of τ<< _TH , the center frequency There is no large difference between the intensity of the waveform and the sideband intensity, and the energy spreads widely over the sideband area, as schematically shown in FIGS. 3A and 3B. That is, the distribution of the section where the unmodulated carrier of 272f _H exists is as shown in FIG. 3A, and the distribution of the section where the unmodulated carrier of 282f _H exists is as shown in FIG. 3B.
Therefore, in any of the examples, (R-
During the horizontal scanning interval where the unmodulated carrier of 282f _H exists, the color difference signal transmission interval of (B-Y) is the center frequency of 282f _H , and the color difference signal transmission interval of (B-Y) is the horizontal scanning interval where the unmodulated carrier of 272f _H exists. 272f _H during scanning section
The energy of the sideband components of the intermittent carrier is injected into oscillation, producing a synchronous oscillation output. With this configuration, when the output vi of the idling signal generation circuit 30 and the output vC of the chroma signal separation circuit 10 are added to the first frequency conversion circuit 20, one horizontal scan can be achieved by the multiplication effect in combination with the low-pass filter. For each line, a low frequency conversion signal with a frequency difference of _10fH is extracted. The signal is recorded in a magnetic recording/reproducing system having predetermined frequency characteristics in the form of frequency multiplexing with a luminance signal that is FM modulated using a well-known configuration. (Since the frequency multiplex recording system is well known in VTRs and the like known as the so-called β or VHS system, a detailed description thereof will be avoided.) Next, the embodiment shown in FIG. 2 will be described. Components in this embodiment that are common to those in the embodiment of FIG. 1 will be designated by the same reference numerals and their explanation will be omitted. The feature of the configuration of the embodiment shown in FIG. 1 is that the idling signal is
In place of the bandpass filter 32 that constitutes 0,
The point is that a band redirection filter 32 is used which eliminates and transmits the 272f _H signal or its frequency sideband components. Such a configuration has the effect that the delay time of the delay circuit 40 in the embodiment of FIG. 2 can be shortened. The output of the second frequency conversion circuit is Vi=βcos{WI+(44±1/8)W _H・t}...(1) or vi=βcos{WI+(44±1/8)W _H・t+π}... (2) becomes. [Here, WI is WI=282f _H (1) is in phase,
(2) represents the signal waveform when the phase is reversed. ] Also, to simplify the explanation, considering the case where the input chroma signal is monochromatic, the output vc of the chroma signal separation circuit 1 is as follows: vc=AsinWct...(1)'vc=Asin(Wct+π)...(2)' Become. Since the contents of equations (1) and (1)' and (2) and (2)' correspond in time, the output of the frequency conversion circuit for downconversion (which functions as a multiplier) is filtered by a low-pass filter. If _only the difference _output component is taken out via will be played. Note that during reproduction, it is not actually necessary to switch and restore the phase of the color difference line sequential FM signal again to 00π or the like. In the reproduction circuit, the idling signal is the output of the 282f _H crystal oscillation circuit, the horizontal synchronization signal in the reproduction signal is used as the reference input, and (44 + 1/8) f _H and (44 - 1/8) f H for each field. The output of the PLL oscillation circuit that generates the phase-locked oscillation output of _fH may be created using a frequency conversion circuit that beats up, and the converted idling signal may be used to inversely convert (beat up) the low frequency converted chroma signal. Note that the above-mentioned injection type oscillator may be replaced with a Clapp type oscillator tuned to 272f _H , and in that case, the bandpass filter 32 in each embodiment may be replaced.
It goes without saying that in the 272f _H bandpass filter, the band rejudgement filter 32 should be replaced with a 282f _H band pass filter. Since the present invention has the above-mentioned configuration, it not only makes it possible to eliminate synchronous switching circuits, etc., but also uses a single injection type oscillation circuit, so SECAM signals with high reliability and color reproducibility are obtained. This not only makes it possible to realize a recording device, but also greatly contributes to cost reduction.

[Brief explanation of the drawing]

The drawings all relate to the device of the present invention, and include Fig. 1,
FIG. 2 is a circuit diagram of a main part of each different embodiment, and FIG. 3 is a spectrum distribution diagram. 10...Chroma signal separation circuit, 20...First frequency conversion circuit, 30 ...Idling signal generation circuit.

Claims (1)

[Claims for Utility Model Registration] One carrier component of the intermittent non-modulated carriers at frequencies F ₁ and F ₂ in the SECAM signal and the sideband component of the other carrier are input to a limiter circuit, and the output of this limiter circuit is A PLL that uses the output of an oscillator that oscillates at a single frequency as an injection input and the horizontal synchronization signal in the SECAM signal as a reference signal and oscillates in phase synchronization at a low frequency with a difference of 1/4 f _H for each field. Using the beat-up output of a frequency conversion circuit with two inputs as the idling signal, the line-sequential chrominance FM signal in the SECAM signal is low-pass converted, frequency-multiplexed with the FM luminance signal, and converted to H for each field. SECAM signal recording device configured for high-density recording due to alignment.