JPS59138185A - Recording circuit of video tape recorder - Google Patents

Abstract

PURPOSE:To arrange the reproducing level of a signal to be recorded by taking a frequency-modulated luminance signal as a bias, by providing a recording level switching circuit to arrange the recording characteristic of a metal coated tape and a vapor deposited tape. CONSTITUTION:The recording level switching circuit 52 is provided at the output side of a mixer 54. The type of a tape is detected by a tape discriminator 67 detecting the type of the tape, and when a signal is recorded on the coat tape, a control terminal 75 is controlled so as to make a transistor (TR) Q1 conductive and when the signal is recorded on the vapor deposited tape, the control terminal 75 is controlled so as to cut off the TRQ1. In setting 20log [R2/(R1+ R2)] to -4dB, the characteristic is as shown in Figure, where dotted lines show the vapor deposited tape, solid lines indicate the coated tape, 3 is a pilot signal, 4 is a chroma signal (CL), 5 is a sound signal, and 6-8 are luminance signals.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention is applicable to luminance signals, color signals, audio signals, and pie signals.

Regarding the recording circuit of a video table recorder that records loft signals and the like on a video track, the above-mentioned Shinto Automobile Co., Ltd. is particularly interested in coated metal tapes and vapor-deposited tapes.

The present invention relates to a recording circuit suitable for recording.

[Traditional search technique]

Conventional video tape recorders are designed to use only iron oxide tape, so it is not possible to use different types of tape such as high-performance coated metal tape or vapor-deposited tape.

The signals recorded on the video track on the videotape include a frequency-modulated luminance signal rate audio signal, a low-frequency converted chroma signal, a tracking control pilot signal, and a PCM signal.
A possible example is an audio signal that has been converted into . These signals each have the optimum recording level and equalization characteristics for the tape being used, so the recording circuit of the video tape recorder has the optimum recording level and equalization characteristics for each tape.

It needs to be switched to ensure timeliness.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and to provide a recording circuit for a video tape recorder that makes it possible to write each signal on a metal-coated tape or a vapor-deposited tape under optimal conditions.

[Summary of the invention]

In the present invention, by using a metal head for both recording and playback with excellent saturation characteristics, the recording current value of the frequency-modulated luminance signal for saturation recording and the audio signal converted to PCM is selected equally for the metal-coated tape and the vapor-deposited tape. At the same time, the recording level is set for each tape after mixing the above signal with multiple signals (for example, a low frequency converted chroma signal, a frequency modulated audio signal, and a pilot signal) to be recorded as a high frequency bias. A current level switching circuit is provided to change the current level.

Conventionally, the optimum recording current for saturation recording signals of metal-coated tapes is 2 to 3 dB higher than that of vapor-deposited tapes, and conversely, the optimum recording current for bias-recording signals is 1-2 dB higher for vapor-deposited tapes, and even lower. The side wave enhancement effect was smaller with vapor-deposited tape, and it was thought that compensation for this was necessary.

This was estimated from the fact that the magnetic layer thickness of the metal-coated tape is 3) 6 .mu.m, while that of the vapor-deposited tape is about 0.1 .mu.m, and that the thickness of the magnetic layer is about 1,300 and 900, respectively. When we actually conducted experiments using ferrite hedads and sendust bulkheads, we obtained results consistent with the above common knowledge.

However, when we found the optimal recording conditions for metal-coated tape and vapor-deposited tape using a video head made by sputtering Sendust thin films with a thickness of 5 to 10 μm and laminating them, we found that metal-coated tapes and vapor-deposited tapes were not suitable for signals recorded in saturation. It was found that when the optimum recording current determined for the evaporated tape was used for the vapor-deposited tape, there was almost no deterioration of C and the lower side wave enhancement effect was extremely similar to that of the coated tape. The optimum recording current for actual vapor-deposited tape is 1
~2dB lower, but even with 1~2dB overcurrent, the % deterioration is 1
In contrast, in the case of a frequency-modulated luminance signal, the lower sideband Q energy is well emphasized, resembling the characteristics of a coated tape. Furthermore, the recording current of the bias-recorded signal can be set to a large value, so that the reproduction level when the vapor-deposited tape is reproduced can be increased, and the difference from the reproduction level of the coated tape can be reduced.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained using the drawings. 1st
The figure shows the frequency characteristics when recording and reproducing the metal-coated tape and the vapor-deposited tape used in the present invention using a Sendust sputter head.

In FIG. 1, 1 is the characteristic of the metal-coated tape, and 2 is the characteristic of the vapor-deposited tape. Below 2MH2, the reproduction level of the coated tape is higher, and above 2MH210, the reproduction level of the vapor-deposited tape is higher.

FIG. 2 shows the output signal spectrum of the recording circuit of the present invention.

7 is a diagram illustrating an embodiment of the present invention, in which the signals recorded on the video track shown in FIG. is the current level. In Figure 2, 3 is a pilot signal, and the frequency is 6 in f1.
．． 5fH.

Z5fkh in f2 j 05fH in f3, p in f4,
5fH (f□ is the horizontal cyclic frequency), and the recording level is the carrier level of a frequency-modulated Nine Diameter signal (hereinafter referred to as YFM).

In terms of odB, the applied tape is about -29 dB, and the vapor-deposited tape is about -25 dB. 4 is a low frequency converted chroma signal (hereinafter referred to as CL), and the frequency ldN T
S C Te(47+j-)7n, CCI4 Te(47-
i) I have selected k, and the recording level is = 1 with coated tape.
4 dB, and -10 dB for the vapor-deposited tape. 5 is a frequency-modulated audio signal (hereinafter referred to as AFM), the frequency is selected to be 1.5±0.1 MH2, and the recording level is -25 dBs for coated tape, -21 dBs for vapor-deposited tape.
It has been selected as B. 6 is YFM lower side band wave, 7 is YFM
The carrier, 8 is the upper sideband wave of YFM, and the carrier frequency is 4.2 MH2 at the synchronous peak and 54 MH2 at the white peak.
The recording level was OdB, and the coating type tape was selected as
It has been selected to have the same recording level as vapor-deposited tape.

FIG. 3 is a diagram showing an embodiment of the output vector of the recording circuit of the present invention, and shows signals recorded on the overlap track shown in FIG. 7.

In Figure 3, 3 is recorded as a pilot signal and Pel is -
The recording level was chosen to be 25 dB, and the same recording level was chosen for both coated tape and vapor-deposited tape. 9 is the lower sideband of the audio signal converted to PCM (hereinafter referred to as AP (referred to as M));
10 is the APCM carrier, 11. is the APCM upper side band wave, and the recording level is selected to be OdB, which is the same for both the coated tape and the vapor-deposited tape.

There is.

FIG. 4 is a diagram showing the relationship between the recording current and the reproduction level of 5MH2, with reference numeral 12 indicating the characteristics of the coated tape and reference numeral 16 indicating the characteristics of the vapor-deposited tape. The suitable recording current of vapor-deposited tape is about 2 dB lower than that of coated tape. However, even when recording a coated tape deposited at the optimum current, the playback level deteriorates by 0.5 dB or less, which is quite acceptable.

Figures 5 and 6 show the cross-modulation characteristics of the tape head system. Figure 5 is a recording spectrum diagram, and Figure 6 is a reproduction signal spectrum diagram. The solid line is the level of the coated tape, and the dotted line is indicates the level of the vaporized tape. In the figure, 14 is CL
carrier, 15 is YFM carrier, 16 is (YFM-
spurious with a frequency of 2Ct, ), 17 is (YFM
-CL).

Y! -□If the recording level of the carrier 15 is selected as the optimum recording current for the coated tape, the reproduction level of the YFM carrier will be approximately +3 dB, assuming that the coated tape is OdB.

Record level of CL carrier 14 is spurious 16.17
It is better to set it as high as possible within the range that is below the allowable value.

In Figure 5, the CL recording level of the coated tape is -14 dB.
and that of vapor-deposited tape is -10 dB.

At this time, as shown in FIG. 6, the CL reproduction level is approximately the same regardless of the tape. The spurious level is about +3 dB higher than that of the applied type.

Since the permissible value of spurious is determined by the value relative to the carrier level of YFIII, substantially the same spurious characteristics are obtained in this state.

If the YFM recording level of the vapor-deposited tape is selected as the optimum recording current of the vapor-deposited tape, the CL recording level needs to be -12 dB in order to make Sgelius 16.17 equal to that in Figure 6. . The reproduction level of CL at this time is -2 dB lower than that of the coated tape. In this way, selecting the gastrogram recording current of the vapor-deposited tape as the optimum recording current of the coated tape is effective for bias-recording CI, XAF, etc.
As shown in Figure 1, there is also a difference in frequency characteristics between coated tape and vapor-deposited tape. This difference records the YFM signal at the optimum recording current for each tape.

There is no problem with the reproduced image quality of coated tape, but the reproduced image quality of vapor-deposited tape lacks resolution and becomes blurry. Conversely, the optimum recording current for coated tape.

If the signal is recorded on both tapes, it is the vapor-deposited tape.

The playback image quality is similar to that of painted tape.

Therefore, there will be no problem. This reduces the recording current to about 2d! ! This is due to the fact that the lower sideband was recorded with emphasis, and from this point of view, the YFM recording current was turned off using the tape. It is desirable that this is not possible.

FIG. 7 is a diagram showing an embodiment of a tape button formed on a video tape by the recording circuit of the present invention. In FIG. 7, the diagonal track 19.2C is formed by wrapping the video tape around a rotary cylinder for 2011f or more.
9 is a video track that corresponds to a corner with a wrap of approximately 180°,
20 is an overlap track corresponding to the overlap winding section, 21.22 is an optional track provided at both ends of the tape, 23 is a tracing direction of the video head,
24° indicates the running direction of the videotape.

FIG. 8 is a diagram showing an example of the frequency characteristics of the recording equalizer used in the present invention. FIG. 9 is a diagram showing an example of the frequency characteristics of the recording equalizer used in the present invention.

In FIG. 9, 70 is an input terminal for an audio signal, 42 is a circuit that converts an analog audio signal into PCM and compresses the time to approximately γ, and 3B is a # 71 is a video signal input terminal; 51 is an AGC (Automation Galn) that controls the brightness signal level to a constant value;
Control), 49 is an LP for extracting the luminance signal.
F, 48 is a C8, lb filter for removing the NTSC color subcarrier, 47 is a clamp circuit that fixes the voltage of the synchronous peak to a constant value, 46 is a dynamic emphasis circuit, 45 is a main emphasis circuit, 44
43 is a frequency modulator, 43 is an HP, Fl 39 is a YFM recording current setting circuit, 62 is a BPF for extracting chroma signals, 6
0 is AC that controls the burst level to be kept at a constant value.
C (Automatic Cn1orControl
) 1.59 is a circuit that boosts only the burst level by 6 dB, 58 is a dynamic amplifier 7 assist circuit, 57 is a frequency converter, and 56 is a carrier generator ((47+)
fH+fe), ((47-T)A+fac
) frequency is generated. fme is the color subcarrier frequency. 55 is an LPF, 72 is an audio signal input terminal, 66 is a non-linear circuit, 65 is an emphasis circuit, 6
4 is a frequency modulator, 69 is a pilot signal generator, 54
is a mixer, 55 is a recording equalizer, an example of which is shown in FIG. 8, 52.68 is a recording level switching circuit, 67 is a device for detecting the type of tape, 40.41 is a recording current level setting circuit, 34.65. 56 and 57 are signal switching circuits, which are connected to the black circle (upper side) when the video head is recording an overlap track, and to the white circle (lower side) when recording a video track. . 50.31.32
．． Reference numeral 33 designates a buffer amplifier with a flat amplitude characteristic, 28 and 29 a write amplifier with a flat amplitude characteristic, 27 a rotary transformer, and 26 a video head. 50 is a detector that detects the amplitude of the luminance signal.

The feature of FIG. 9 is that the recording level switching circuit 52 is installed on the output side of the mixer 54.

By doing so, the recording level switching circuit can have an extremely simple configuration.

FIG. 10 shows an example of a recording level switching circuit.

In FIG. 10, 76 is an input terminal, 74 is an output terminal,
75 is a control terminal.When recording on coated tape,
Ql is conductive, and when recording on vapor-deposited tape 2, Ql is cut off. 2 o. f(R1+R2) -4dB
If selected, the characteristics shown in Fig. 2 can be obtained.

Another feature of FIG. 9 is the location of the recording equalizer 53. The recording equalizer 53 is necessary for the CL which is the output signal of the LPF 55, but it may also equalize the AFM and pilot signals. In this case, the equalization circuit acts as a suppressor of harmonic spurious, so
There is no need to separately provide a spurious suppression filter.

41.68 in Figure 9 is necessary to accurately set the level of the signal (recorded in the lap track section), but even if the recording level of the signal is increased, the error rate of the arm is still small. 41.68 may not be necessary as long as it is set to a level higher than the level recorded on the video track. Figure 11 is.

FIG. 3 is a block diagram showing an embodiment of the recording circuit of the present invention when there is no need to record APCM. In FIG. 11, the switches 34, 55, 3 (S, 57) in FIG. 9 are deleted, and their explanation will be omitted.

〔Effect of the invention〕

According to the present invention, it is possible to make the recording characteristics of metal-coated tape and vapor-deposited tape the same without using a simple recording level switching circuit, and it is possible not only to make the reproduction quality of the luminance signal the same, but also to make the reproduction quality of the luminance signal It is also possible to equalize the reproduction level of recorded signals by using the signal as a bias.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing an example of the characteristics of the tape used in the present invention, FIGS. 2 and 6 are characteristic diagrams showing an example of the recording current spectrum generated from the recording circuit of the present invention, and FIG. 4 is a characteristic diagram showing an example of the characteristics of the tape used in the present invention. FIG. 5 is a characteristic diagram showing an example of the recording current spectrum; FIG. 6 is a characteristic diagram showing an example of the spurious characteristics of the tape and head system used in the present invention; FIG. is a diagram showing an example of a tape pattern formed by the recording circuit of the present invention, FIG. 8 is a characteristic diagram showing an example of the characteristics of a recording equalizer used in the present invention, and FIGS. 9 and 11 are diagrams showing an example of the tape pattern formed by the recording circuit of the present invention. A block diagram showing an embodiment of the 10th
The figure shows an embodiment of a recording level switching circuit used in the present invention. FIG. Explanation of symbols 49...LPF for brightness signal sampling. 44... Frequency modulator, 57... Frequency converter for chroma signal low frequency conversion,
69... Pilot signal generator, 54...
...Mixing circuit, 52... Recording level switching circuit, 67...
- Tape discrimination device. Representative Patent Attorney Akira Takahashi Ima≦ijuyamiliuneCMH')

Claims (1)

[Claims] The chroma signal and the pilot signal are recorded in a two-head helical scan type video precoder that records the frequency-modulated luminance signal in saturation, uses the pattern luminance signal as a high-frequency bias, and records at least the low frequency converted chroma signal and pilot signal. The recording level switching circuit is provided with a mixing circuit, a recording level switching circuit, and a device for determining the type of tape, and the recording level switching circuit is provided on the output side of the mixing circuit, and the recording level is switched according to the output signal of the discrimination device. A recording circuit for a video tape recorder, characterized by controlling the circuit.