JPS6313583B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking correction device used in a magnetic reproducing device, so-called a video tape recorder.

Some video tape recorders are equipped with still playback and intermittent slow still playback functions in addition to normal recording and playback functions. When the intermittent feed slow still playback function is activated, the capstan motor repeatedly rotates and stops intermittently. Therefore, the tape also moves and stops repeatedly, but the rotary head always rotates at a constant rate. When the tape is stopped, the rotary head performs still playback, and when the tape is transferred, normal playback occurs. What is important here is to set the timing for moving or stopping the tape so that the reproduced image is not disturbed while the rotating head is rotating. For this reason, the timing at which the capstan motor is stopped by the brake pulse is important. When stopping, the regeneration control head picks up the regeneration control signal and generates a brake pulse after a certain delay time from that signal.
The tape is stopped at a position where the rotating head stably traces the recording track.

However, while slow still playback of tapes recorded by the same magnetic playback device is not a big problem, slow still playback of tapes recorded by the same magnetic playback device may cause problems with the position of the playback control head and the rotating head. The distance from the location may be different. Therefore, if the tape is stopped after a predetermined delay time after the reproduction control signal is obtained and still reproduction is performed, the rotary head may take an abnormal trace trajectory with respect to the recording track.

This invention was made to deal with the above-mentioned circumstances, and it is possible to adjust the brake pulse to the capstan motor at a good timing during slow still playback, and at the same time, this adjustment can be used during normal playback. Reference signal (control signal is phase-locked to this signal)
It is an object of the present invention to provide a tracking correction device which is also effective for timing adjustment.

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

In Fig. 1, first, the capstan motor 1
The control system for 1 will be explained first. The capstan motor 11 includes transistors Tr ₁ , Tr ₂ , Tr ₃ , Tr ₂
Its rotation and stopping are controlled by. When the transistors Tr ₁ and Tr ₂ are on, the capstan motor 11 rotates in the normal direction. Therefore, in the case of normal reproduction, a drive signal is applied to the input terminal 12. Further, when stopping the capstan motor 11, a brake pulse is applied to the input terminal 13. This results in a transistor
Tr ₃ and Tr ₄ are turned on and the capstan motor is stopped.

The rotation frequency and phase of the capstan motor 11 are controlled. In this case, a frequency detection (rotation detection) signal of the capstan motor 11 is input to the amplifier 15 via the input terminal 14 and detected by the speed detection circuit 16. As a result, frequency fluctuations of the capstan motor 11 are detected, and the detected signal is input to the amplifier 18 via the synthesizer 17. The amplifier 18 has its output drive pulse width varied or its gain adjusted in accordance with the control signal from the synthesizer 17, and applies the output to the input terminal 12.

Further, when controlling the capstan motor 11, it is necessary to correspond the reproduction control signal and the rotation phase. Therefore, the reproduction control signal from the control head 19 is input to the phase detector 21 via the amplifier 20. In the phase detector 21, the phase of the reproduction control signal and the correction reference signal is compared, and the error is extracted. The output of the phase detector 21 is input to the synthesizer 17 via the phase compensation circuit 22. In other words, the capstan motor is controlled so that the reproduction control signal is phase-locked to the correction reference signal.

The corrected reference signal is generated by a reference signal processing system, which will be described later.

First, the components related to normal playback will be explained. That is, 31 is a first time constant circuit, and is composed of a variable resistor R1 and a capacitor C1. The voltage supply section of this time constant circuit 31 includes:
One end of variable resistor 32 is connected.

This variable resistor 32 is a feature of the present invention, and its slider is connected to a power supply terminal 33.

The output terminal of the time constant circuit 31 is connected to the inverter 34 and also to the collector of the transistor _Q2 . The emitter of this transistor _Q2 is connected to the reference potential terminal. The inverter 3
The output terminal of 4 is connected to the correction reference signal output terminal 35. Further, the output terminal of the inverter 34 is connected to a reset terminal of a flip-flop circuit 37 via a mono-multivibrator circuit 36.
The set terminal of this flip-flop circuit 37 is provided with a reference signal input terminal ref.

The reference signal is, for example, a frequency-divided color subcarrier (usually output from a voltage-controlled oscillator in an APC loop) that serves as a reference for the reproduction processing circuit.
A signal converted to a frequency 1/2 that of the playback control signal is used.

This reference signal is corrected by the time constant circuit 31 and output to the output terminal 35, and is used for controlling the capstan motor 11 described above.

Now, to explain about normal reproduction, the reference signal is a pulse as shown in FIG. 2a. When this reference signal is supplied to the input terminal ref, the flip-flop circuit 37 is set and the transistor
Q ₂ turns on. Therefore, the charge stored in the capacitor C1 from the power supply +B is discharged, and the signal shown in FIG. 2b is input to the inverter 34. An appropriate threshold voltage is set in the inverter 34, and an output as shown in FIG. 2c is obtained. The fall timing of the output of the inverter 34 can be adjusted by adjusting the time constant of the time constant circuit 31 using the variable resistor 32. When the output of the inverter 34 rises, the mono-multivibrator circuit 36 is activated and the flip-flop circuit 37 is reset, turning off the transistor _Q2 .
Charging of capacitor C1 is started. By adjusting the time constant at this time, the phase of the reference signal (corrected reference signal) can be variably adjusted with respect to the phase of the reproduction control signal (FIG. 2d). This phase difference is detected by the phase detector 21.

This means that the relative position of the rotating head and the rotating head (control head) can be adjusted, resulting in compatibility of video tape recorders with different spacings between the two heads.

Next, a description will be given of the path that operates when the video tape recorder is operated in an intermittent feed slow still mode.

In FIG. 1, 41 is a second time constant circuit, which is composed of a variable resistor R2 and a capacitor C2. The power supply +B is supplied to the power supply terminal of the second time constant circuit 41 via the other terminal of the variable resistor 32, the resistor 42, and the diode 43.

The output terminal of this second time constant circuit 41 is connected to an inverter 44 and a transistor
Connected to the collector of Q ₁ . this transistor
The emitter of _Q1 is connected to the reference potential terminal.
The output of the inverter 44 is connected to a brake pulse output terminal 45 and is also connected to a flip-flop circuit 47 via a mono multivibrator circuit 46.
connected to the reset end of the The output terminal of this flip-flop circuit 47 is the transistor _Q1
A control signal input terminal cnt is connected to the base of the controller, and a control signal input terminal cnt is provided at its set input end.

The brake pulse generation system B described above also obtains the same operation as the correction reference signal processing system A described above. That is, when the playback control signal is input to the input terminal cnt, the transistor _Q1 turns on and the capacitor C2
(Figure 3b). A delayed pulse (see FIG. 3c) appears at the output end of the inverter 44. A brake pulse (FIG. 3d) is generated from the trailing edge of this delayed pulse. this is,
Although not shown, it can be easily obtained using a mono-multivibrator circuit. FIG. 3a shows a reproduction control signal.

By such an operation, a brake pulse can be obtained for good tracking after the regeneration control signal is obtained. That is, in the case of intermittent feed slow still playback operation, first, still playback is performed when the tape stops, and then still playback is repeated after the tape has been advanced by one track. Further, when the tape is moved, normal playback is performed. Therefore, the capstan is subjected to repeated control of constant speed and stopping, but if the rotary head is not in a good tracking position when stopping, the image quality will deteriorate. Brake pulses are used for such stopping, and the timing of their generation is important in determining the stopping position.

In FIG. 1, 50 is a remote control connector, and when the remote control circuit 51 is connected, the transistor _Q3 is turned on, and the time constant of the second time constant circuit 41 is set to the remote control circuit 51. Adjustment is possible by variable resistor R3. That is, this variable resistance R
Power is applied to one end of 3 through a resistor 52 and a diode 53. The diode 43 is
In this case, it functions as a current blocker.

The device of the present invention described above uses one variable resistor 32 in common as a signal timing adjustment means for the correction reference signal processing system A that operates during normal playback and the brake pulse generation system B that operates during intermittent feed slow still playback. It is characterized by its unique features.

In this case, the slider position is not simply shared, but the slider position adjusted during normal playback is also applied as is during slow still playback, and the effort of adjusting each time can be omitted.

In other words, to explain the normal playback operation,
When playing back video tapes recorded on different video tape recorders, the distances between the rotary head and the rotating head (discarding playback control signals) of each video tape recorder may be different. In such a case, the phase of the reproduction control signal may be obtained at an early stage even though the rotary head and the recording track are in the correct position. If this relationship is maintained as it is, the capstan motor control loop will incorrectly determine that the playback control signal is out of phase, causing an unnecessary operation to slow down or speed up the tape advance. It turns out. Therefore, in this case, the phase of the reference signal whose phase is being compared with the reproduction control signal is corrected by adjusting the variable resistor 32 in the correction reference signal processing system A described above. Now, move the tape recorded at distance X1 between the rotary head and the rotating head at distance X2.
Consider the case of playback on a video tape recorder.

If X1<X2, the control signal is obtained with a delay with respect to the best tracking point, so it is necessary to delay the phase of the reference signal.

On the other hand, when slow still playback is performed, the capstan of the video tape recorder repeatedly rotates and stops, and the tape is advanced intermittently. In this case, the rotary head is preferably located at the best tracking point when the tape is stopped. However, as mentioned above, if there is a relationship of X1<X2, the playback control signal will be picked up with a delay with respect to the best tracking point when the tape is fed. Therefore, it is not enough to constantly output a brake pulse after picking up the reproduction control signal, and the relationship between the rotary head and the recording track will be such that it has passed the best tracking point. Therefore, in such a case, the rotary head can be positioned at the best tracking point by making the generation phase of the brake pulse earlier, that is, by making the delay time faster.

Note that in the case of the relationship X1>X2, the above is the opposite, and the phase of the reference signal may be accelerated and the phase of the brake pulse may be delayed.

As described above, the adjustment of the reference signal during normal playback and the adjustment of the brake pulse during slow still playback are related to each other, and the directions (phases) of the adjustments are opposite to each other. In other words, the fourth
As shown in the figure, when increasing the phase of the reference signal during normal reproduction, it is necessary to slow down the phase of the brake pulse and make the correction amount have an inverse relationship.
The line (PLAY) shown in Figure 4 represents the amount of correction of the reference signal during normal playback with respect to the rotation angle of the rotary head.
The line (SLOW) is the brake pulse correction amount during slow still playback.

In the present invention, correction of the reference signal in the normal playback mode and correction of the brake pulse in the slow still playback mode as described above are performed in accordance with 1.
It is characterized in that it is simultaneously adjusted by two variable resistors 32. If the variable resistor 32 is used to adjust the phase of the reference signal to be early, this also serves as an adjustment to slow down the phase of the brake pulse. In other words, the characteristics shown in FIG. 4 can be obtained by adjusting one variable resistor 32, making the adjustment operation easy.

As described above, the present invention makes it possible to adjust the brake pulse to the capstan motor at good timing during slow still playback, and at the same time adjust the timing of the reference signal used during normal playback. It is possible to provide a tracking correction device that can also be applied to

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, FIGS. 2 a to d are signal waveform diagrams of various parts for explaining the operation of the correction reference signal processing system in FIG. 1, and FIGS. 3 a to 3
d is a signal waveform diagram of various parts for explaining the operation of the brake pulse generation system shown in FIG. 1, and FIG. 4 is a tracking correction characteristic diagram of the device of the present invention. DESCRIPTION OF SYMBOLS 11... Capstan motor, 13... Brake pulse input terminal, 21... Phase detector, A... Correction reference signal processing system, B... Brake pulse generation system, 3
1, 41...first and second time constant circuits.

Claims (1)

[Claims] 1. In a helical scan type magnetic recording and reproducing device, means for adjusting the phase of a constant frequency reference signal by a first time constant circuit to obtain a corrected reference signal; Means for inputting a comparison signal with a playback control signal to a rotation control circuit forming a loop for controlling the rotation of a capstan motor; means for obtaining a brake pulse by adjusting the phase using a constant circuit; means for inputting the brake pulse to a brake circuit of the capstan motor; and a power supply terminal of the first time constant circuit; a variable resistor to which a terminal is connected, the other terminal is connected to a power supply terminal of the second time constant circuit, and a slider is connected to a common DC power supply,
A tracking correction device characterized in that the variable resistor causes the direction of phase shift adjustment of the correction reference signal and the phase shift adjustment direction of the brake pulse to be opposite to each other, thereby serving as adjustment in normal playback and slow still playback. .