JPS61192004A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To omit the necessity for memory of grades and also to attain the automatic switching of the carrier frequencies of the frequency modulated signals in response to the grades, by deciding the carrier frequency of a frequency modulated weave based on the result obtained by recording and reproducing one or 2 single-frequency signals on a loaded magnetic tape. CONSTITUTION:A gate circuit 16 delivers the record detecting signals recorded at a part T which is reproduced by a magnetic head 4 to the band filters 17 and 18 through a gate while the incoming gate pulse (d) is kept at a low level. The filter 17 filters the 1st detection signal of a frequency f1 from the reproduction signal. While the filter 18 filters the 2nd detection signal of a frequency f2 from the reproduction signal. Both detection signals of frequencies f1 and f2 undergo the wave detection of envelope curves through wave detectors 19 and 20 respectively and are supplied to a comparator 21. The comparator 21 delivers a signal of a high level when a level ratio f2/f1 of both reproduced 1st and 2nd detection signals is larger than the prescribed value and then a signal of a low level when said ratio is smaller than the prescribed value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus, and more particularly to a magnetic recording and reproducing apparatus that automatically determines the grade of a magnetic tape used in a VTR and records and reproduces information signals. .

BACKGROUND OF THE INVENTION The current magnetic recording and reproducing bag a (for example, VT
Magnetic recording and reproducing devices, which are the mainstream among R), separate a luminance signal and a carrier color signal from a standard system (NTSC system, PAL system, or SECAM system) composite color video signal, and the brightness signal is frequency-modulated. As a frequency modulated wave,
The carrier color signal is frequency-converted to a low frequency band to produce a low-frequency converted carrier color signal, which is then frequency-division multiplexed onto the above-mentioned frequency modulated wave and recorded. During playback, signal processing is performed in the opposite direction to that during recording to restore the original signal. Obtain a reproduced composite color video signal that complies with the standard method.
This is a magnetic recording and reproducing device using a so-called low frequency conversion recording and reproducing method.

In the above-mentioned conventional magnetic recording and reproducing apparatus, the band of the frequency-modulated luminance signal to be recorded is increased compared to the conventional one to improve the image quality of the reproduced video signal. When recording and reproducing the recorded frequency-modulated luminance signal, the sideband output of the upper sideband is low because normal grade magnetic tape can record and reproduce only relatively low frequencies at a high S/N. A so-called reversal phenomenon is likely to occur.

However, in recent years, magnetic tapes (high-grade magnetic tapes, such as SXG (product name)) have been developed that can record and reproduce signals with high S/N up to higher frequency bands than normal-grade magnetic tapes. I reached the point.

When this high-grade magnetic tape is used, when the carrier frequency of the frequency-modulated luminance signal is increased higher than before and recorded and reproduced, it is possible to obtain a reproduced video signal of higher image quality than before without causing an inversion phenomenon. can. Therefore,
When using a high-grade magnetic tape, in order to fully utilize the capabilities of the tape, the carrier frequency of the frequency modulated wave of the VTR should be increased compared to the conventional one.

Problems to be Solved by the Invention However, as a means for switching the VTR to record at a higher carrier frequency of the frequency-modulated wave when using a high-grade magnetic tape than when using a normal-grade magnetic tape, the present invention has been developed. One possible method is for the user to manually change the above using a switch, but for this purpose, the user must be able to determine whether the magnetic tape produced and sold under various names by each tape manufacturer is normal grade or high grade. There were problems such as the need to memorize the following information, and the operation was manual, making it difficult to operate.

Therefore, the present invention solves the above problem by determining the carrier frequency of the frequency modulated wave based on the results obtained by recording and reproducing one or more single frequency signals on a magnetic tape attached to a VTR. The purpose of the present invention is to provide a magnetic recording/reproducing device that solves the above problems.

Means for Solving the Problems The magnetic recording/reproducing apparatus according to the present invention has one single unit set to a frequency that produces a large reproduction signal/signal level difference or C/N difference depending on at least the grade of the magnetic recording medium. Detection signals consisting of one or more single frequency signals including one frequency signal are recorded on a magnetic recording medium simultaneously or sequentially in front of the start of recording of the information signal, and then reproduced, and m number of detection signals are reproduced. The carrier frequency of the frequency modulated information signal to be recorded is variably set based on the signal obtained by comparing the detection levels or the signal obtained by detecting the C/N of one detection signal.

Further, the recording and reproduction of the detection signal is performed on the same track, or only within or near the vertical blanking period of the video signal.

Effect The detection signal consisting of the plurality of single frequency signals mentioned above is, for example, a frequency signal fI near the carrier frequency of the normal grade of the magnetic tape, and a frequency signal "2" which causes a large difference in reproduction signal level depending on the grade of the magnetic tape. , These frequency signals @f1 and f2 are recorded on a magnetic tape and then reproduced, and the grade of the magnetic tape is automatically determined based on whether the ratio of the detected signal levels 12/'r+ is greater than a predetermined value. This allows the carrier frequency of the frequency modulated information signal to be switched.

Embodiment FIG. 1 shows a block system diagram of an embodiment of a magnetic recording/reproducing apparatus according to the present invention. First, when the user presses the record button, the magnetic tape 1 is transferred to the guide ball 2 as shown in FIG.
a and 2b, the magnetic head 4a (first The magnetic head 4 shown in the figure (consisting of this magnetic head 4a, etc.) begins to rotate at high speed in the direction of arrow B. As a result, a drum pulse a having one frame period as shown in FIG. 2(A) generated by a known means is transmitted to the waveform shaping circuit 5 via the input terminal 5 shown in FIG.
Here, it is converted into a pulse b with a narrow pulse width as shown in FIG. 2(B). This pulse b is supplied to the recording/reproduction switching pulse generation circuit 7 and the gate pulse generation circuit 8, respectively. The recording/reproduction switching pulse generating circuit 7 has a predetermined width as shown in FIG. 2(C) so that it rises only after a certain period of time after the first input of pulse b, and falls in approximately phase synchronization with the fall of drum pulse a. The recording/reproducing switching pulse C shown in FIG. While this recording/reproduction switching pulse C is at a high level, the switch circuit 9 switches to the terminal 9a side to open one end of the resistor R1, and the switch circuit 10 is connected to the terminal 10a side to connect one end of the magnetic head 4 to the resistor. It is grounded through R2 and the switch circuit 10, and at the same time the switch circuit 11 is turned on. This puts the device into the recording state. Here, the single frequencies f1 and 2 outputted from the oscillators 12 and 13 are, for example, the fourth
As shown in FIG. The frequencies are selected to cause a large difference in reproduction signal level depending on the grade of the tape.These single frequencies "1" and "f2" are supplied to the magnetic head 4 via the switch circuit 11 and the recording amplifier 14, respectively.

As a result, the composite signal of the single frequency "1" and "2" is detected by the magnetic head 4 (4a in FIG. 3) on the magnetic tape 1 whose running is stopped only during the high level period of the pulse C. Here, the high level period of pulse C is selected to be near the end of one field, for example, the vertical blanking period, as shown in FIGS. 2(A) and 2(C). As a result, the composite signal (detection signal) of the single frequencies ``l'' and ``2'' is generated in the area on the magnetic tape 1 (near the last vertical blanking period of one track) indicated by the circle in Figure 3. part) as a detection signal.

However, when the pulse C output from the recording/reproduction switching pulse generation circuit 7 becomes low level at time [1], the switch circuit 9 switches to the terminal 9b side, and the recording amplifier 14
The output end of the resistor R2 is grounded via the resistor R+ and the switch circuit 9, and the switch circuit 10 is switched to the terminal 10b side, thereby opening one end of the resistor R2 and putting the 5A position into the regeneration state.

At the same time, the switch circuit 11 is turned off. As a result, the detection signal t recorded on the magnetic tape 1,
, r2 are still reproduced by the magnetic head 4 and supplied to the gate circuit 16 via the preamplifier 15. on the other hand,
The gate pulse generating circuit 8 responds only to the second and subsequent pulses among the pulses b, and responds only to the second and subsequent pulses b.
falls after a certain period of time from each input point of time, and the trailing edge time t2. of the drum pulse a shown in FIG. 2(A). Rising at t3 etc.
A gate pulse d as shown in FIG. 2(D) is applied to the gate circuit 1.
Output to 6. The negative pulse width of this gate pulse d is equal to the pulse width of pulse C, and the drum pulse a
The position for pulse C is also chosen to be equal to that of pulse C.

The gate circuit 16 gate-outputs the recording detection signal of the recording part molecule reproduced by the magnetic head 4 while the incoming gate pulse d is at a low level, and outputs it to the bandpass filters 17 and 18 . The bandpass filter 17 converts the first detection signal of frequency "i" into a P wave from the reproduced signal, while the bandpass filter 1
8 converts the second detection signal of frequency f2 from the reproduced signal into a P wave. After the detection signals of the frequencies "1" and "2" are envelope-detected by the detectors 19 and 20, respectively, the comparator circuit 21
supplied to The comparator circuit 21 outputs a high level signal when the level ratio f2/fI of the reproduced first and second detection signals is greater than or equal to a predetermined value, and outputs a low level signal when it is smaller than a predetermined value. Outputs the signal. Comparison circuit 21
The grade of the magnetic tape 1 can be automatically determined based on the output signal level. The output signal of the comparison circuit 21 is held by the hold circuit 22 and then supplied to the FM modulation circuit 23.

The FM modulation circuit 23 is configured so that its carrier frequency is changed according to the output signal level of the hold circuit 22, and when the output signal of the hold circuit 22 is at a low level, the solid line ■ in FIG. The carrier frequency deviation band of the frequency-modulated luminance signal in the normal grade tape shown in FIG. The transfer band is switched from "4" to "6" (however, f3 < f, < f5 < 16). At the same time, the VTR is switched to the normal recording mode and the magnetic tape 1 starts running.

As a result, the luminance signal that has entered the input terminal 24 and is to be recorded is FM-modulated by the FM modulation circuit 23 at a carrier frequency that matches the grade of the magnetic tape 1, and then supplied to the mixer 25. 4 from terminal 26 (A
＞ is mixed with the low-pass conversion carrier color signal in the band shown by .

The frequency division multiplexed signal consisting of the low-pass converted carrier chrominance signal and the frequency-modulated luminance signal extracted from the mixer 25 is as follows:
The signal is supplied to the magnetic head 4 via the recording amplifier 14, and is thereby recorded on the magnetic tape 1. Here, the band of the above-mentioned frequency-modulated luminance signal is as shown by the solid line ■ in Figure 4 (A>) when using a normal grade tape, and as shown by the broken line ■ in Figure 4 (A>) when using a high-grade magnetic tape. It will be as shown.

Note that the signal frequency-modulated and recorded by the magnetic recording/reproducing device of the present invention is not limited to a luminance signal, and may be other information signals (for example, an audio signal, a video signal),
Furthermore, the detection signal is not limited to the two single frequencies r1 and r2, but may be a plurality of single frequency signals, and may be recorded and reproduced sequentially. disc, etc.) may also be used.Furthermore,
The method of recording and reproducing the detection signal is not limited to that of the embodiment. For example, after running the magnetic tape and recording the detection signal for a certain period of time, the magnetic tape is automatically rewound, and then the reproducing state is set. It is also possible to adopt a configuration in which the detection signal is regenerated by switching to . Further, the above two detection signals may be set to only one single frequency fx that causes a large C/N difference depending on the grade of the magnetic recording medium. In this case, instead of the bandpass filters 17 and 18, a trap circuit that removes the detection signal of the frequency rx and a bandpass filter that sends the detection signal of the frequency "X" are used. In this case, the C/N
When is above a predetermined value, F is applied regardless of the magnitude of the detection level.
Change the M carrier frequency to a higher value. Furthermore, the detection signal may be recorded within the vertical blanking period avoiding the vertical synchronization signal position.

Effects of the Invention As described above, according to the present invention, the grade of a magnetic recording medium can be automatically determined in advance before recording an information signal, and therefore users of magnetic recording and reproducing apparatuses differ from manufacturer to manufacturer. There is no need to memorize all the grades of magnetic recording media produced and sold under different names, and the carrier frequency of the frequency modulated signal can be automatically switched according to the grade of the magnetic recording medium. Black-and-white reversal coloring occurs in magnetic recording media, and when using high-grade magnetic recording media that can record or reproduce even in frequency bands that cannot be recorded or reproduced, the FM carrier frequency can be set higher than before, so its performance can be improved. It has features such as being able to maximize its performance.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing an embodiment of the magnetic recording/reproducing apparatus according to the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the block system shown in FIG. 1, and FIG. 3 is a magnetic recording system according to the present invention. FIG. 4, which is a schematic perspective view of the reproducing apparatus, is a frequency spectrum diagram of each signal recorded on the magnetic tape. 1... Magnetic tape, 4, 4a... Magnetic head, 5.
...Drum pulse input terminal, 6...Waveform shaping circuit, 7
...Record/reproduction switching pulse generation circuit, 8...Gate pulse generation circuit, 9.10.11...Switch circuit, 1
2゜13... Oscillator, 16... Gate circuit, 17.
18...Band filter, 19.20...Detector, 2
1... Comparison circuit, 22... Hold circuit, 24...
- Luminance signal input terminal, 26...Low frequency conversion carrier color signal input terminal, 27... Reproduction video signal output terminal.

Claims (3)

[Claims] (1) Detection consisting of one or more single frequency signals, including one single frequency signal selected at a frequency that produces a large playback signal level difference or C/N difference depending on the grade of the magnetic recording medium. A signal obtained by recording signals simultaneously or sequentially on a magnetic recording medium immediately before starting recording of an information signal and then reproducing the signals and comparing the detection levels of a plurality of reproduced detection signals or the C/C of one detection signal. A magnetic recording/reproducing apparatus characterized in that the carrier frequency of a frequency-modulated information signal to be recorded is variably set based on a signal obtained by detecting N. (2) The magnetic recording and reproducing apparatus according to claim 1, wherein the recording and reproducing of the detection signal is performed on the same track. (3) The magnetic recording and reproducing apparatus according to claim 1 or 2, wherein the recording and reproducing of the detection signal is performed only within or near the vertical blanking period of the video signal.