JPS633594A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the variance of the overlap period of head switching signals by providing a decoder which outputs a pulse in accordance with the output of a counter which counts a chrominance subcarrier and determining the head switching timing by the output of this decoder to generate head switching signals. CONSTITUTION:30Hz square wave signal SW30 is supplied to an edge detecting circuit 4 to generate pulses 5 of leading and trailing edges of the signal SW30, and a counter 6 which uses a chrominance subcarrier fsc as the clock is reset by the pulse 5 to measure the time from the edge of the signal SW30, and the measured value is outputted. A pulse 9 a prescribed time before the edge of the signal SW30 and a pulse 8 a prescribed time after it are obtained from a decoder 7. These pulses 8 and 9, the signal SW30, and 15Hz square wave signal SW15 are used to generate 4-channel (ch1-ch4) head switching signals (H.SW) corresponding to four heads.

Description

[Detailed Description of the Invention] [Field of Application] The present invention relates to 8-key recording and playback of camera-type VTRs, etc., and generates switching signals for four heads that are sometimes used for recording and playback. The present invention relates to a 6-ki recording and reproducing device suitable for recording and reproducing data.

[Conventional technology]

In miniaturized magnetic recording and reproducing devices such as camera-type VTRs, small head cylinders are used.
A head out-of-order recording system is used. In this arrangement, the diameter of the head cylinder is made smaller than that of the conventional VHS system, and two pairs of azimuth angles, each with a different azimuth angle, are placed at 90° intervals on the circumference, making a total of four video cameras. The heads are arranged so that the four heads alternately run over the tape to perform recording or reproduction according to the VHS format.

Then, just before one of the four heads finishes running, the tape is already wound so that the next head reaches the starting point and records the next track.
At the beginning and end of each track, overlapping signals are recorded [and during playback, by appropriately switching the played signals, it is possible to extract them as a complete video signal. There is.

Conventionally, the switching signals for the four heads mentioned above were the national
Technical Report, M31S, t6g, December 1985, pp. 62 @ - 63 (NationalLal
Technical Report Vol. 31.
tψ0.6 Dec, 19851P, P, 62-
As described in 63), it is created to overlap the J-reconnaissance, and the time of the overlap is:
PG jf Al (monostable multivibrator)
It is configured to be determined by the operating period of (determined by the time constant of the capacitance and resistance R) and the reference voltage of the comparator.

[Problem that the invention seeks to solve]

In the conventional VC described above, since the overlapping period of the head switching signals is determined using a monomultiplier using a time constant and a comparator, variations in the capacitance value and resistance value or the ambient temperature of the house may occur. In addition, variations in the characteristics of the comparator and the influence of ambient temperature can cause large variations in the overlap period. Therefore, it is necessary to determine the time constant by taking into account the variation in the overlap period, and the weir must be large enough for the minimum required value of the overlap, which will cause a recording current and a stalk between the signals due to the overlap. There was a problem that the period increased.

The present invention reduces the variation in the overlap period of the head switching signal, and by bringing this overlap period to the minimum necessary level with good accuracy, it saves power by reducing the recording current, and improves image quality by reducing the period during which α-stoke occurs. The purpose of the present invention is to provide a five-chip energy regeneration device that achieves the following.

[Means for solving problems]

The above purpose is to use the color subcarrier signal Cf5c) as a clock, and to enable measurement over the period of one field of the video signal WQ TK
A counter, a decoder that outputs a pulse at a certain counter value, this pulse and a 5oHz rectangular wave signal, 15H2
This is achieved by creating head switching signals for each of the four heads from the rectangle i2f: signal.

[Effect]

The counter that uses the color subcarrier signal as a counter is 30H2.
(7) Counting starts from the edge of the square wave signal (SF30) and is reset at the next edge of :f#'500. The decoder fails to read the value of the counter, and after time T1 and Tr from the edge of 5vso (however, T.

(T; Outputs a pulse during (one field period).

Then, the above 5W30 and 15H2 square wave signals (,5F
The signal created by the combination of 15), the above pulse ￥
By selecting CHl, CH2, CH5, CHa
outputs a signal to set or reset each head switch. Use this signal, Cf11, CH2
,CHs,(,'H4(1) Each head switching signal is output from each RS flip-flop by cent or resetting the four RS flip knobs, each of which creates a head switching signal.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a main part of an example of an S-air recording and reproducing apparatus according to the present invention, in which 1 to 3 are signal input terminals, 4 is an edge detection circuit, 6 is a counter, 7 is a decoder, and 10 and 1
1 is NOT gates 12-15 and 20-27
is an AND gate, 30 to 33 are RS flips 70, and 34 to 37 are output signals.

Further, FIG. 2 is a timing chart of signals of each part in FIG. 1, and signals corresponding to those in FIG. 1 are denoted by the same reference numerals.

1 and 2, the input terminal 5 has a 30H
A rectangular wave signal (,5F50) of S f50 is supplied, and passes through an edge detection circuit 4 to generate pulses 5 of both rising and falling edges of S f50. Now, the color subcarrier input to input terminal 1 (fsc = 3.5814z,
CLOCK (which is the reference CLOCK of the VTR's servo circuit)
C, a half cycle of 1,5F30 (approximately 16.6m5e
c) Prepare a counter 6 capable of counting.

By resetting this counter with pulse 5, S
Measure the time from the edge of F2O and output the value to terminal Q. , Q0 to Qn, and output from Qn. Then, using the decoder 7, from the edge of 1.5F30, f.

Generate a time-delayed pulse 8 and a Tζ-delayed pulse 9. 5AVso period is 55. S5rnsgc
(Electric.

sec), pulse 9 can be said to be a signal that is 33.33-T1' (mzac) (this value is taken as T) ahead of the edge of SIF'so.

Pulse 9, which is 12 hours ahead and pulse 8, which is 12 hours late, for the 5F5oHzs edge created using the above method.
4 channels (cAl
, Cn2, ch3, cha) A certain head switching signal (
(hereinafter referred to as H-SF). First, two signals,
15Hz square wave signal (5r1s) to input terminal 2 and 5
From Wso, using gates 10 to 15 in FIG.
I E +1SF 16 t cA2 HeSfF'
17, ch5H-SF'1B, ch4H-SF
Create '19.

Now, chlH-S F 34 is cAI H@S W
It is a signal that rises quickly and falls later than '16.

Therefore, pulse 28 and pulse 29, 5W50(r)
The leading pulse 9 and the delayed pulse 8 with respect to the edge are extracted by ANDENT 20 and 21, and chlH,.5M7s4 is created from these two signals.

In other words, when creating cAI H-5F1a, CAI H-5F'16 Yor)
Create pulse 28 at the rising timing of chlH・5Wsa, and cAI H@S W 1
ch2 H-S F17 delayed from 6 and pulse 8 to c
Create pulse 29 at the falling timing of AI HIIS F1a.

Pulse 28 is then input to the set input of the RS flip-flop 300, and pulse 29 is input to the reset input. The output of this RS flip 7a knob 30 is cAI HI
ISWS2.

. No L2 H, SFF' 35, c no 3
H fist s W 56 t c A4'
”S F 57 as well, chlHm S F'16
, ch2 He SF'17, ch5H-,5F
'18, ch4H-SF'19, and pulses created by combining pulses 8 and 9 are created by inputting them to the RS flip-flops 61-53.

〔Effect of the invention〕

As explained above, according to the present invention, the clock generated by the crystal oscillator (fzc = 5.5795d5tW
Since the overlap is determined by counting Hx ), the variation is the B equipment error o, 28μsgc (=
'4. With c), the overlap period of the head switching signal can be reduced to the nth degree (to the minimum necessary), power can be saved by reducing the recording current, and image quality can be improved by reducing the period during which rear stalk occurs. It is possible to solve the drawbacks of the prior art and provide a magnetic recording/reproducing device with excellent functions.

[Brief explanation of drawings]

FIG. 1 is a main circuit diagram showing an embodiment of a magnetic recording/reproducing apparatus according to the present invention, and FIG. 2 is a timing chart illustrating the operation of the configuration shown in FIG. 1... Color subcarrier signal (fsc) input terminal 2 ・=
15Hz square wave (,5F15) input terminal 5-5OHz
Square wave (,5F30) input terminal 6...Counter 7...Decoder 50-33...R57 lip 7a tube 1, fsc
Input 143 G17 Kung? , r5Hz
1f155 good input γ decoder 3.50H
XnM3 included Jt%chi 5ty-yy shaku S7
Lee, +7” 7D F γ4 Edge-Jiko rotation straddle

Claims (1)

[Claims] 1. A total of four heads, two sets with different azimuth angles, are placed in order at 90° intervals on the cylinder circumference, and the VHS
A magnetic recording and reproducing device that enables recording and reproducing according to a recording format is provided with a counter that counts color subcarriers and a decoder that outputs pulses according to the count output of this counter, and head switching is performed using the output of the decoder. A magnetic recording/reproducing device characterized in that it is provided with a circuit that generates a head switching signal at a determined timing.