JPH0525076Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a drum servo circuit for a rotary head type VTR, and particularly relates to a configuration for shortening the drum servo start-up time.

[Conventional technology]

Some conventional camera-integrated VTRs have only a recording function. The drum servo circuit for the rotating drum in this VTR detects the rotational speed of the rotating drum using a rotation detector, and controls the speed of the rotating drum to a set value based on the detection signal. At the same time, the detection signal of the rotation detector and the servo reference signal obtained by dividing the output signal of the crystal oscillator of the sync generator are phase-compared, and a phase error signal corresponding to the phase difference is used to detect the rotating drum. The rotational phase of the servo was made to match the phase of the servo reference signal.

[Problem that the invention attempts to solve]

In the drum servo circuit as described above, it takes time from t ₀ to t ₁ as shown in FIG. 3 until the rotational speed reaches the set speed when the rotating drum starts up. Furthermore, the comparison signal from the detection head is then gradually brought into synchronization with the servo reference signal from the sync generator. As shown in Figure 3, the phase shift between the detection signal and the servo reference signal is
A time period of t ₁ to t ₂ was required for the phase shift to fall within the allowable phase shift range Aθ.

For this reason, a time of about 3 seconds, for example, is required from when the record button is pressed until recording actually starts.

Also, if you want to take continuous shots, press the pause button, etc., and wait until the pause button is pressed.
Recording continues for only 10CTL (control) signals, and after recording stops, the mechanical mechanism operates.
It is rewound by 10 CTL signals. The rotating drum is
It remains rotating and is in recording standby mode. When the record button is pressed again, only 7CTL minutes are recorded.
After detecting the CTL signal, timing the tape run, and stopping the tape, continuous recording was started after the period t ₁ to _{t 2} shown in Figure 3 in synchronization with the reference signal of the sync generator. .

For this reason, even when taking continuous shots, there was a problem in that there was a delay between when the record button was pressed and when recording actually started.

Accordingly, an object of this invention is to provide a drum servo circuit for a rotary head type VTR that can synchronize the rotation of a rotary drum with a servo reference signal generated by a sync generator in a shorter time than before.

[Means for solving problems]

This invention consists of a television camera, a rotary head type VTR that records the output video signal of the television camera, a synchronization signal generation circuit 6 that generates a servo reference signal for the drum phase servo of the rotary head type VTR, and a rotation A detection means for detecting the rotational phase of the head, a means for comparing the phase of the output signal of the detection means with a servo reference signal, and a means for controlling the drum phase based on the comparison output, and a means for controlling the drum phase immediately after the start of recording using the output signal of the detection means. Means 1, 2, 3, for resetting the synchronization signal generation circuit 6;
This is a drum servo circuit equipped with 4 and 5.

[Effect]

One input terminal of the AND circuit 5 is connected to the waveform shaping circuit 14, and the other input terminal is connected to a gate pulse generation circuit constituted by the monomulti 3, 4 and the switch circuits 1, 2. AND
The output terminal of the circuit 5 is connected to the reset input terminal of the frequency division counter of the sync generator. The frequency division counter of the sync generator 6 is reset by the output from the AND circuit 5 generated during the pull-in operation of the phase servo circuit.

〔Example〕

An embodiment in which this invention is applied to a camera-integrated VTR will be described below with reference to the drawings.

In FIG. 1, numeral 11 is a drum motor having a DC motor configuration. The drum motor 11 is driven by a drive amplifier 10, and the rotation period and rotation phase of the drum motor 11 are detected by a detection head 12. A detection signal (PG pulse) generated in the detection head corresponding to the rotation period of the drum motor 11 is sent to the amplifier 13 and the waveform shaping circuit 1.
The signal is supplied to the speed servo circuit 15 and the phase comparator circuit 7 via the signal line 4.

A reference signal is supplied from the sync generator 6 to the phase comparator circuit 7, and this reference signal is compared with a detection signal supplied from the waveform shaping circuit 14.
A phase error signal corresponding to the phase shift is supplied to an adder 9 via a low-pass filter 8.

Further, a speed error signal corresponding to the error between the actual rotational speed of the drum motor 11 and the predetermined rotational speed is supplied from the speed servo circuit 15 to the adder 9. In the adder 9, the phase error signal and the speed error signal are added, and the added output is supplied to the drive amplifier 10.

The sync generator 6 is a one-chip IC having a crystal oscillator and a plurality of frequency division counters, and divides the output signal of the crystal oscillator by the frequency division counter to generate a horizontal synchronization signal, a vertical synchronization signal, a camera polarization signal, It generates servo reference signals, etc.
The sync generator 6 also has a reset input terminal for resetting each frequency division counter to its initial state. For example, when a high level signal is supplied to this reset input terminal, each frequency division counter is set to an initial state.

One terminal of the switch circuit 1 is connected to a power supply terminal 16 via a resistor, and the other terminal is grounded via a resistor. The input terminal of a monostable multivibrator (hereinafter referred to as monomulti) 3 is connected to the other terminal of the switch circuit 1, and the output terminal of the monostable multivibrator 3 is connected to one input terminal 2a of the switch circuit 2. In addition, switch circuit 2
The other input terminal 2b of is connected to the other terminal of the switch circuit 1. Output terminal 2 of switch circuit 2
c is connected to the input terminal of mono multi 4. The Q output terminal of the monomulti 4 is connected to one input terminal of the AND circuit 5. The other input terminal of the AND circuit 5 is connected to the output terminal of the waveform shaping circuit 14,
The output terminal of the AND circuit 5 is the sink generator 6
Connected to the reset input terminal of the

The switch circuit 1 is a non-lock type switch circuit that is turned on when the REC (recording) button is pressed. When the REC button is pressed, a high level start pulse is supplied to the monomulti 3.

The monomulti 3 has a time constant circuit made up of an externally attached resistor and a capacitor, and this time constant circuit determines the first period in which the output of the monomulti 3 is at a low level. This first period is
The drum motor starts rotating from a stationary state,
This is approximately equal to the time required to reach the predetermined rotation speed.

In the case of normal recording, the switch circuit 2 is in a state where the input terminal 2a and the output terminal 2c are connected. However, in the case of continuous shooting, if the pause button is pressed in a recording state where the REC button is pressed, the switch circuit 2 is placed in a state where the input terminal 2b and the output terminal 2c are connected. That is, the timing of generation of the gate pulse supplied to the AND circuit 5 is switched by the switch circuit 2.

Also, recording starts after the pause button is pressed.
After receiving 10 CTL signals, the magnetic tape is stopped, and then the magnetic tape is rewound by 10 CTL signals by the operation of the mechanism, and is placed in a standby state. At this time, the drum motor 11 continues to rotate.

Incidentally, when the switch circuit 2 is pressed, for example, a stop button, the drum motor 11 is stopped and the input terminal 2a and the output terminal 2c are returned to the connected state.

The monomulti 4 has a time constant circuit consisting of an externally attached resistor and capacitor. This time constant circuit determines the second period in which the Q output of the monomulti 4 is at a high level. This second period is set to be somewhat longer than the period of the drum motor 11, that is, the period of the detection signal (PG pulse).

The operation of one embodiment of the invention described above will be explained with reference to FIG. FIG. 2 shows the phase shift between the servo reference signal and the detection signal.

When the REC button is pressed at timing _t0 in FIG. 2, the stopped drum motor starts rotating, the switch circuit 1 is turned on, and a start pulse rising to a high level is supplied to the monomulti 3. At the same time that the star pulse is supplied to the monomulti 3, the monomulti 3 falls to a low level. Thereafter, the rotational speed of the rotating drum reaches a predetermined speed at the timing _t11 in Fig. 2, that is, the timing _t0.
At a timing when a predetermined first period has elapsed, the output of the monomulti 3 rises to a high level.

When the output of the monomulti 3 becomes high level, the Q output of the mono multi 4 becomes high level, and this output is supplied to one input terminal of the AND circuit 5. The detection pulse from the waveform shaping circuit 14 supplied to the other input terminal of the AND circuit 5 causes the Q output of the monomulti 4 to be at a high level.
Appears at the output of AND circuit 5. This output is supplied to the reset input terminal of the sink generator 6,
The frequency division counter of the sync generator 6 is reset to the initial state.

A reference signal synchronized with the rotation period of the drum motor 11 is supplied to the phase comparator circuit 7, and the Q output of the monomulti 4 goes low at timing _t12 after a predetermined second period has elapsed from timing _t1 in FIG. level, and the reset of the sink generator 6 is completed. By this reset, the phase shift between the detection signal and the servo reference signal is immediately adjusted to the allowable phase shift range Aθ.
The lock state is reached. Recording operation is started after this phase servo is locked.

When the pause button is pressed in the above-mentioned recording state when it becomes necessary to take continuous shots. The output terminal 2c and input terminal 2b of the switch circuit 2 are connected. At this time, recording continues for 10 CTL signals, and this
The magnetic tape is rewound by 10 CTL, the drum motor continues to rotate, and is placed in a standby state.

Thereafter, when the REC button is pressed again, the switch circuit 1 is turned on, and a start pulse rising to a high level is supplied to the monomulti 4 via the switch circuit 2. At the same time as the start pulse is supplied to the mono multi 4, the Q output of the mono multi 4 is set to high level, and this output is sent to the AND circuit 5.
is supplied as a gate pulse to one input terminal of. As the detection pulse rises thereafter, the frequency division counter of the sync generator 6 is reset to the initial state as in the case described above, and the phase servo is immediately brought into the locked state. and
CTL signals are detected for 7 CTL signals, the timing for tape running is determined, and then recording starts again.

[Effect of idea]

According to this invention, one input terminal of the AND circuit 5 is supplied with a detection signal corresponding to the rotation period and rotation phase of the drum motor, and the other input terminal is supplied with the monomulti 3, 4 and the switch circuit 1, A gate pulse formed by 2 is applied. AND
The output terminal of the circuit 5 is connected to the reset input terminal of the frequency division counter of the sink generator 6.
By the detection signal passed through the output of the AND circuit 5,
The sink generator 6 is reset by tamping immediately after the rotational speed of the drum motor 11 rises to the set speed. Therefore, the rotational phase of the rotating drum and the servo reference signal from the sync generator 6 are forced to match. That is, recording can be performed immediately without going through the pull-in operation at the time of startup of the phase servo of the drum motor, and the time in the recording standby state can be shortened.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an embodiment of this invention, Figure 2 is a waveform diagram used to explain the operation of an embodiment of this invention, and Figure 3 is a waveform diagram used to explain a conventional drum servo circuit. . 1, 2... Switch circuit, 3, 4... Monostable multivibrator, 5... AND circuit, 6... Sink generator, 11... Drum motor, 12
...Detection head.

Claims (1)

[Scope of utility model registration request] A television camera and a rotary head VTR that records the output video signal of the television camera.
a synchronizing signal generation circuit for generating a servo reference signal for the drum phase servo of the rotary head type VTR, a detection means for detecting the rotational phase of the rotary head, an output signal of the detection means and the servo reference signal. After the drum motor starts rotating at the start of recording and reaches a predetermined speed, the output signal of the detection means controls the synchronization signal. A drum servo circuit comprising reset timing setting means for resetting a generation circuit.