JPH0327980B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control pulse recording circuit for a magnetic recording/reproducing device, and more particularly to a device for recording control pulses in a double gap type magnetic recording device.

BACKGROUND TECHNOLOGY In a so-called double-gap type magnetic recording/reproducing device, during recording and normal reproduction, Fig. 5A,
Standard play mode (SP) as shown in B
(2 hour mode), video head SP1, SP2
Ex-band play mode (EP) (6
In time mode), video heads EP1 and EP2 are used. The video heads EP2 and SP1 are mounted offset by, for example, 2H on the circumference of the rotating drum.

Here, for still playback in SP mode, video heads EP2 and SP2 with the same azimuth angle are used, as shown in Figures 6A and 7G and H, and for still playback in EP mode, as shown in Figures 6B and 7H. As shown in Figures I and J, video heads EP1 and SP1 having the same azimuth angle are used. Note that G and I in FIG. 7 are video head switching modes, and H and J in the same figure are still FM levels. By doing this, the playback FM level during still is high, and field still has less blur compared to frame still.
Can be used in both SP mode and EP mode.

On the other hand, for the recording control pulse, an X value is specified to ensure compatibility of the magnetic tape. The pulse is to be recorded. As a result, in the double gap method, the time charts shown in Figure 7 A, B, C, and D are obtained in SP mode, and the time charts shown in Figure 7 A, B, and D are obtained in EP mode.
This is the time chart for B, E, and F. Note that A in the same figure is a video signal, B in the same figure is a drum PG pulse, C and E in the same figure are channel switching modes, and D and F in the same figure are recording control pulses.

Therefore, if the relative height H between the video heads SP and EP in Figure 5A is close to normal, then the heights in Figure 7B and
As shown in D and F, SP for drum PG pulse
The recording timing of the recording control pulse is set to 1 field (16.6 msec) in mode and EP mode.
It is necessary to shift it.

FIG. 8 shows a block system diagram of an example of a conventional device. The recording mode will be explained. The video signal A (FIG. 9A) inputted to the terminal 1 is separated from the vertical synchronization signal L (FIG. 9B) by the vertical synchronization signal separation circuit 2, and is driven by counting the clock from the crystal oscillator 18. The 30Hz oscillation circuit (counter) 3 generates a signal C (C in the same figure). Here, the threshold C ₄ ,
C ₅ , C ₆ (C ₄ < C ₅ < C ₆ ) are set, and the threshold C ₅
The 30Hz signal D (D in the same figure) is extracted in synchronization with the vertical synchronization signal B, and in the SP mode, it is supplied to the waveform shaping circuit 4 via switch _SW1 and becomes the signal H (E in the same figure). The signal is then supplied to the control head 6 via the recording amplifier 5 and recorded on the magnetic tape.

On the other hand, in the EP mode, the output signal 2 of the oscillation circuit 3 (D in the same figure) is delayed by one field in the delay circuit 7 to become a signal (F in the same figure), and the output signal 2 (D in the figure) is outputted by the waveform shaping circuit 4. G) in the figure, and is recorded on the magnetic tape by the control head 6.

On the other hand, in the drum servo system, a trigger pulse pulse (H in the same figure) is extracted by the threshold value _C4 of the oscillation circuit 3, is made into a signal signal (I in the same figure) in the trapezoidal wave shaping circuit 8, and a trapezoidal wave is generated in the trapezoidal wave generating circuit 9. The signal N (J in the figure) is supplied to the phase comparator circuit 10. Drum PG pulse from drum motor 13 (K in the same figure)
is taken out and made into signals wo (L in the same figure) and signal wa (M in the same figure) by the monomultis 14 and 15, respectively, and made into a signal F (N in the same figure) by the flip-flop 16, and then sent to the sample pulse generation circuit 17. This is called the sample pulse (O in the same figure).

The phase comparison circuit 10 compares the phases of the trapezoidal waveform signal NU and the sample pulse YO, and the phase comparison error signal is supplied to the drum motor 13 via a low-pass filter LPF 11 and a motor drive amplifier MDA 12 to drive and control the drum motor 13. .

On the other hand, in the capstan servo system, the clock of the crystal oscillator 18 is connected to the capstan reference oscillation circuit 19 and the trapezoidal wave shaping circuit 20 to generate a signal (S in the figure).
The trapezoidal wave generating circuit 21 generates a trapezoidal wave signal (T in the figure), and the signal is supplied to the phase comparator circuit 22. Capstan from capstan motor 25
The FG pulse is converted into a sample pulse (Q in the figure) via an amplifier 26, a frequency dividing circuit 27, and a sample pulse generating circuit 28.

The phase comparison circuit 22 compares the phases of the trapezoidal wave signal and the sample pulse, and the phase comparison error signal is supplied to the capstan motor 25 via a low-pass filter (LPF) 23 and a motor drive amplifier (MDA) 24. Drive control of the capstan motor 25.

On the other hand, in the reproduction mode, _the tracking monomulti 2
The signal S (R in the same figure) is obtained at 9, and the trapezoidal wave signal generated from the signal S and the reproduction control pulser (P in the same figure) from the control head 6 are sent to the amplifier 3.
The phase comparison error signal is used to drive and control the capstan motor 25 using the phase comparison error signal obtained as a result. Note that the tracking monomulti 29 can adjust the tracking deviation, and the signal can have a tracking variable range τ ₁ .

Problems to be Solved by the Invention The conventional circuit described above requires a one-field delay circuit 7, and has a problem that it cannot be constructed at low cost.

The present invention uses a 60Hz oscillation circuit to
The purpose of the present invention is to provide a control pulse recording circuit for a magnetic recording/reproducing device that can obtain control pulses necessary for SP mode and EP mode without using a delay circuit, and can be constructed more simply and at lower cost than conventional circuits. do.

Means for Solving the Problems In FIG. 1, the oscillation circuit (counter) 31 counts signals with a higher frequency than the vertical synchronizing signal separated from the video signal, and is reset by the vertical synchronizing signal during recording. During reproduction, the flip-flop 32 is a means for self-running and outputting a 60Hz oscillation output, a means for outputting a 30Hz signal whose polarity is inverted when the count value of the counter reaches a threshold, a switch SW ₁ , an inverter 35, an AND gate 33 , the control pulse generation circuit 34, and the control head 6 are 2
30Hz synchronized with one polarity of the 30Hz output signal according to the usage mode switching for each video head in the set.
3 is an embodiment of a means for generating and recording a 30 Hz control pulse or a 30 Hz control pulse synchronized to the other polarity of the 30 Hz output signal.

Operation: The oscillation circuit 31 takes out a 60Hz oscillation output, and the flip-flop 32 outputs a 30Hz signal whose polarity is inverted when the count value of the counter reaches the threshold, and the switch _SW1 , inverter 35, AND gate 33, and control Pulse generation circuit 34 and control head 6 control one of two sets of video heads.
30Hz control pulse synchronized with one polarity of the 30Hz output signal or synchronized with the other polarity of the 30Hz output signal depending on the usage mode switching for each set.
Generate and record a 30Hz control pulse.

Embodiment FIG. 1 shows a block system diagram of a first embodiment of the circuit of the present invention. In the figure, the same components as in FIG. 8 are given the same numbers, and the same signals are given the same symbols. Therefore, the explanation will be omitted. The recording mode will be explained. The vertical synchronizing signal RO (FIG. 2B) is converted into a signal c (FIG. 2C) by a 60 Hz oscillation circuit (counter) 31. The oscillation circuit 31 has threshold values C ₁ , C ₂ , C ₃ (C ₁ <
C ₂ <C ₃ ) is set, and a 30Hz signal d (D in the same figure) is taken out from the flip-flop 32 by the threshold _C1 , and a 60Hz signal f (F in the same figure) is taken out by the threshold _C3 . Ru.

In the SP mode, the signal d and the signal f are ANDed at the AND gate 33 to generate the signal g (G in the figure), and the control pulse generating circuit 34 generates the recording control pulse h (H in the figure). be done.
In the EP mode, a signal obtained by inverting the polarity of the output signal d of the flip-flop 32 by the inverter 35 and the signal f are ANDed by the AND gate 33 to become the signal i (I in the figure), and a control pulse is generated. Recording control pulse j in circuit 34
(J in the same figure).

In this way, in the present invention, the 60 Hz oscillation circuit 31 is used to generate the 60 Hz signal f, and the signal f and the signal d, and the signal f and the signal obtained by inverting the polarity of the signal d are respectively switched using the switch SW ₁ to perform the AND operation. As a result, the SP mode control pulse h and the EP mode control pulse j delayed by one field can be obtained, and there is no need to provide a particular delay circuit as in the conventional device.

On the other hand, in the drum servo system, the oscillation circuit 31
A trigger pulse k (K in the same figure) is taken out by the threshold value C ₂ of , and is supplied to the flip-flop 36. The output signal d of the flip-flop 32 is converted into a reset pulse e (E in the figure) by the reset pulse generation circuit 37, and is supplied to the flip-flop 36. The signal l (L in the figure) is taken out from the flip-flop 36, and is sent to the trapezoidal wave generation circuit. Trapezoidal wave signal m at 9 (M in the same figure)
It is said that

The drum PG pulse n (N in the same figure) from the drum motor 13 is sent to the monomultis 14 and 15 as signals o and 15, respectively.
p (O, P in the same figure), and the flip-flop 16
The sample pulse generating circuit 17 generates a signal q (Q in the figure), and the sample pulse generating circuit 17 generates a sample pulse r (R in the figure).

On the other hand, the capstan servo system performs the same operation as the conventional circuit, and the capstan motor 25 is driven and controlled by the same operation as described above.

FIG. 3 shows a block system diagram of a second embodiment of the circuit of the present invention, in which the same components as those in FIG. omitted. Battle values C ₁ , C ₂ , C ₉ , C ₃ (C ₁ <C ₂ <C ₉ <C ₃ ) are set in the 60Hz oscillation circuit 41, and the flip-flop 43 is set according to the threshold value _C9.
A drum FF signal q' (FIG. 4G) is extracted from.

Also, the signal y from the monomulti ₄₂ is determined by the threshold value C2.
(H in the figure) is taken out and made into a signal l' (I in the figure) by the flip-flop 36, and made into a signal m' (J in the figure) by the trapezoidal wave generating circuit 9. drum motor 13
The drum PG pulse n (K in the same figure) from is converted into a sample pulse r' (L in the same figure) in the waveform shaping circuit 44 and the sample pulse generation circuit 17, and its phase is compared with the signal m' in the phase comparator circuit 10. .

Note that the present invention is not limited to what is shown in the above embodiments; for example, the threshold value C ₂ of the oscillation circuit
The configuration may be such that control pulses for SP mode and EP mode and a trapezoidal wave signal for drum servo are obtained using only the following.

Effects of the Invention According to the circuit of the present invention, even without using a delay circuit,
It has the advantage of being able to obtain the control pulses required for each of the SP mode and EP mode, and being simpler and cheaper to construct than conventional circuits.

[Brief explanation of drawings]

1 and 2 are block system diagrams and their signal waveform diagrams, respectively, of a first embodiment of the circuit of the present invention, and FIGS. 3 and 4 are block system diagrams and their signal waveform diagrams, respectively, of a second embodiment of the circuit of the present invention. A signal waveform diagram, FIG. 5 is a configuration diagram of a video head of a double-gap type magnetic recording/reproducing device, FIG. 6 is a diagram showing its track pattern, FIG. 7 is a diagram showing the relationship between its control pulses and head switching, and FIGS. FIG. 9 is a block system diagram and a signal waveform diagram of an example of a conventional circuit, respectively. 1...Video signal input terminal, 2...Vertical synchronization signal separation circuit, 6...Control head, 9...
Trapezoidal wave generation circuit, 10... Phase comparison circuit, 13...
...Drum motor, 17...Sample pulse generation circuit, 31...60Hz oscillation circuit, 32, 36...Flip-flop, 33...And gate, 34...
Control pulse generation circuit, 35... Inverter, 37... Reset pulse generation circuit, SW ₁ ...
Switch.

Claims (1)

[Scope of Claims] 1. Two pairs of video heads having different azimuth angle gaps are provided, and video signals are recorded and played back by switching the two video heads according to different magnetic tape speeds. In a control pulse recording circuit of a magnetic recording/reproducing device, a signal having a higher frequency than a vertical synchronizing signal separated from the video signal is counted, and is reset by the vertical synchronizing signal during recording, and free-running during playback. A circuit that outputs a 30Hz signal whose polarity is inverted when the count value of the counter reaches a threshold value, and a circuit that outputs a 30Hz signal whose polarity is inverted when the count value of the counter reaches a threshold value. and a circuit that generates and records a 30Hz control pulse synchronized with one polarity of the output signal of the circuit or a 30Hz control pulse synchronized with the other polarity of the output signal of the circuit. Control pulse recording circuit for magnetic recording and reproducing equipment.