JPH057831Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a tracking circuit for a video tape recorder (VTR) that performs intermittent slowing.

(b) Prior Art A conventional circuit will be explained with reference to FIG. In Figure 2, 10 is the control head, 12
14 is a switch that supplies a control signal during recording, and 14 is a tracking servo circuit that matches the rotational phase (RF switching signal) of the rotary head with the reproduction control signal. 16 is a hysteresis amplifier that shapes the playback control signal; 18
is a monomulti for tracking triggered by a playback control signal. The pulse width of the pulse output from this tracking mono-multi 18 is determined by the capacitor C1 constituting the mono-multi,
It is defined by a semi-fixed volume R1 and a variable resistor (tracking volume) VR1. 2
0 is also a monomulti.

22 is an intermittent slow servo circuit. 24 is a mono multi for throat tracking. The pulse width of the pulse output from this monomulti 24 for slow tracking is determined by the capacitor C2, semi-fixed volume R2, and variable resistor (slow tracking volume) VR2 that make up the monomulti.
Defined by 26 is also a monomulti, and this monomulti 26 is for creating brake pulses.

The functions of the tracking volume VR1 and the slow tracking volume VR2 will be explained with reference to FIGS. 3 and 4.

Figure 3 shows the tape recorded by this VTR.
These are the waveforms of each part during self-recording and playback when played back on a VTR. Note that this waveform is a waveform when tracking is correct. Further, RF-SW is a signal (RF switching signal) indicating the phase of the rotating head.

Figure 4 shows tapes recorded with different VTRs.
These are the waveforms of each part when played back with this VTR (hereinafter referred to as compatible playback). Note that this waveform is a waveform when tracking is correct.

In other words, the playback control signal during compatible playback
The phase (timing) difference of the RF switching signal is
It may be different from when recording and playing by yourself. Therefore, during normal reproduction, tracking adjustment is performed by adjusting the tracking volume VR1 and varying the pulse width (T'STD in FIG. 4b). Also, during intermittent slow playback, slow tracking volume VR2
is adjusted to vary the pulse width (T'SLOW in Figure 4d) to perform slow tracking adjustment.

In this way, conventionally, the tracking volume is adjusted so that the timing of the fall of the output b of the tracking mono multi 18 and the fall of the output d of the slow tracking mono multi 24 are the same as during self-recording and playback. I was adjusting VR1 and throat tracking volume VR2.

(c) Problems to be solved by the invention However, in the above example, both the tracking volume VR1 and the slow tracking volume VR2 had to be adjusted during compatible playback.

The present invention has been made in view of the above points, and proposes a tracking circuit that serves both as a tracking volume and a slow tracking volume.

(d) Means for Solving the Problems The present invention provides a tracking circuit for a video tape recorder that performs intermittent slowing by using a mono multi-circuit that is triggered by a playback control signal from a control head, and a mono multi-circuit that is triggered by a playback control signal from a control head. a variable resistor for tracking adjustment connected to the capacitor to configure the time constant circuit of the mono-multi circuit together with the capacitor, and a slider of the variable resistor for intermittent slow and normal playback. a time constant switching means that switches the time constant by supplying a switching voltage through different resistances at different times; a servo circuit that performs tracking using the output of the mono multi circuit during normal playback; and an output of the mono multi circuit during intermittent slow play. This tracking circuit is characterized by comprising an intermittent slow servo circuit that generates brake pulses.

(e) Action As is clear from Figures 3 and 4, TSTD-TSLOW=T'STD-T'SLOW TSTD-T'STD=TSLOW-T'SLOW. In other words, if TSTD−TSLOW=ΔT1 and TSTD−T′STD=ΔT2, then ΔT1=TSTD−TSLOW=T′STD−T′SLOW ΔT2=TSTD−T′STD=TSLOW−T′SLOW. And ΔT1 is always constant and ΔT2
varies depending on the tape being played.

In other words, by varying the pulse width by ΔT1 during normal playback and intermittent slow playback, and adjusting ΔT2 with a variable resistor, it can be used as a monomulti.

Therefore, in the present invention, the time constant of the monomulti circuit is switched by ΔT1 using the time constant switching circuit,
Adjust ΔT2 with a variable resistor.

(F) Embodiment An embodiment of the present invention will be described with reference to FIG. Note that the same parts as in FIG. 2 are given the same reference numerals, and redundant explanation will be omitted. 30 is a monomulti circuit for both tracking, and VR3 is a variable resistor (tracking volume) that adjusts slow tracking and normal tracking;
VR3 constitutes a time constant circuit of the monomulti circuit 30. 31 is a slider of tracking volume VR3. 34 is a terminal, to which a high level signal +B is applied during intermittent slow playback, and a low level signal is applied during normal playback. 32 is an inverter circuit, D1 and D2 are diodes, and R3 and R4 are semi-fixed resistors.

This terminal 34 inverter circuit 32 diode D
1, D2 semi-fixed resistors R3 and R4 form a time constant switching circuit 33.

The above operation will be explained. When performing normal playback during self-recording and playback, the terminal 34 is at low level,
Diode D2 is turned off. Also, the inverter circuit 32 sends a high level signal +B to the tracking volume of diode D1 and semi-fixed resistor R3.
It is applied to the monomulti 30 via VR3.
At this time, the tracking volume VR3 configures the values of each element so that it is located at the center click point.

At this time, the values of semi-fixed resistor R3, tracking volume VR3, and capacitor C3 are R3,
Assuming VR3 and C3, the time constant (corresponding to the pulse width) at this time is as follows.

TSTD=(VR3+R3)×C3 Then, the signal from this monomulti 30 is input to the monomulti 20.

Further, when performing intermittent slow playback during self-recording and playback, a high level signal is input to the terminal 34 and the diode D2 is turned on. And semi-fixed resistor R4
Letting the value of R4 be as follows.

TSLOW=(VR3+R4)×C3 Then, the signal from this monomulti 30 is input to the monomulti 26.

In addition, the resistor R is set so that the pulse width of the mono multi 30 is different during slow and normal playback by ΔT1.
3. The value of R4 has been adjusted.

TSTD−TSLOW=(R3−R4)×C3=ΔT1 Also, during compatible playback, tracking volume
By adjusting VR3, the pulse width of the monomulti 30 can be changed by the same amount of time ΔT2 regardless of whether it is during normal playback or slow playback. For example, when the amount of change in tracking volume VR3 is ΔVR3, the values of T'STD and T'SLOW are shown below for reference.

T′STD=(VR3+ΔVR3+R3)×C3 T′SLOW=(VR3+ΔVR3+R4)×C3 Thus, according to the present invention, the time constant switching circuit 3
3 corrects the pulse width of the monomulti 30 during intermittent slow playback and normal playback. Then,
The tracking volume can be used both during normal playback and during intermittent slow play.

Another example is shown in FIG. In FIG. 5, the same parts as in FIG. 1 or 2 are given the same reference numerals.

In FIG. 5, 40 is a tracking monomulti, and the pulse width of its output pulse is determined by a capacitor C3, a tracking volume VR3, and a semi-fixed resistor R3 connected thereto, which constitute the monomulti. 20 is mono multi,
The resistor R5 and capacitor C5 are selected so that the pulse width is longer by ΔT1 than in the monomulti 20 of FIGS. 1 and 2. FIG. 6 shows the waveforms of each part. That is, in the example shown in FIG. 5, the difference in pulse width (ΔT1) between intermittent slow playback and normal playback is corrected by setting the time constant of the monomulti 42 longer by ΔT1.

(g) Effects of the invention As described above, according to the invention, the monomulti for tracking can be used both during normal playback and during intermittent slow playback, so the circuit can be simplified. Moreover, tracking volume 1
Tracking can be adjusted during normal playback and intermittent slow playback, making it easy to use.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 is a diagram showing a conventional example, and FIGS. 3 and 4 are diagrams showing waveforms at various parts. FIG. 5 is a diagram showing another example, and FIG. 6 is a diagram showing waveforms at various parts in FIG. 10... Control head, 14... Tracking servo circuit (servo circuit), 22... Intermittent slow servo circuit, 26... Mono multi (intermittent slow servo circuit), 30... Mono multi circuit, 3
1...Slider, 33...Time constant switching circuit, C
3... Capacitor, VR3... Variable resistor.

Claims (1)

[Scope of Claim for Utility Model Registration] In a tracking circuit of a video tape recorder that performs intermittent slowing, a mono multi-circuit triggered by a playback control signal from a control head, a capacitor constituting this mono multi-circuit, and this capacitor. Also, a variable resistor for tracking adjustment is connected to the capacitor to form a time constant circuit of the monomulti circuit, and a slider of the variable resistor is switched via different resistors during intermittent throw and normal playback. a time constant switching means for switching a time constant by supplying a voltage; a servo circuit for performing tracking using the output of the monomulti circuit during normal playback; and an intermittent servo circuit for creating a brake pulse using the output of the monomultiple circuit during intermittent slow playback. A tracking circuit comprising a slow servo circuit.