JPS62183687A - Fh correction circuit - Google Patents

Abstract

PURPOSE:To realize an fH correction circuit of simple constitution by providing a means for detecting a change of a tracking error signal and a means for controlling a rotating speed of a rotating head based on the change and correcting the rotating speed of the rotating head based on the change of this tracking error signal. CONSTITUTION:The rotating speed VH of a head motor 2 is converted into a voltage by an F/V converting circuit 4. The output of this f/V converting circuit 4 is impressed to a comparison circuit 5. A correction speed reference voltage V2 is impressed to the comparison circuit 5 from a horizontal synchroniz ing signal frequency fH correction circuit 6. In the fH correction circuit 6, a speed reference voltage V1 during an ordinary time is impressed to an end of a resistance R and the tracking error signal Ev is impressed to an end of a capacitor C. The voltage at the connecting point of the resistance R and the capacitor C is the correction speed reference voltage V2. The head rotating speed VH can be represented by KV2 and the V2 can be represented by an expression I, so that the head rotating speed can be corrected by using the tracking error signal Ev.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an fH correction circuit in a video tape recorder.

(b) Conventional technology 2-head helical scan type video tape recorder (
(VTR), by making the tape movement speed different from that during recording, m special playback can be realized. For example, if you stop tape running, still playback will start at 2.
Each slow speed or double speed playback can be performed by running at a speed of 1 or twice the speed.

By the way, in these special reproductions, the relative speed between the rotating head and the tape is different from that during recording, so the horizontal synchronizing signal frequency (fH) in the reproduced video signal differs from the normal one. Therefore, depending on the television receiver used for monitoring, there is a possibility that the reproduced image may be distorted.

Therefore, in the past, fH in the reproduced video signal has been corrected by changing the rotational speed of the rotary head in accordance with the change in relative speed.

As a configuration for this purpose, for example, Japanese Patent Laid-Open No. 57-1387
No. 2 discloses a configuration in which the rotation of a rotary head is controlled by detecting a frequency shift of a horizontal synchronizing signal in a reproduced video signal with respect to a normal one.

(c) Problems to be Solved by the Invention The above-mentioned prior art requires an error signal generation circuit based on the horizontal synchronization signal in the reproduced video signal, that is, a monomulti, a trapezoidal wave generation circuit, and a sample hold circuit. , the configuration becomes complicated.

Therefore, in the present invention, a tracking error signal based on a tracking method adopted in 8mm video is used.
Perform fH correction. and means for detecting a change in the tracking error signal.

A means is provided for controlling the rotational speed of the rotary head based on this variation.

(E) Effect Since the tracking error signal indicates the deviation between the rotary head and the track, changes in this tracking error signal are related to the inclination of the track and the rotary head in the scanning direction. Therefore, fH correction can be performed by correcting the rotating head rotation speed based on this change.

(f) Implementation example Examples will be described below with reference to the drawings.

Figure 1 is a block diagram of the embodiment, Figures 2, 3, and 4.
The figure is a diagram for explaining the principle.

First, the principle will be explained according to FIGS. 2 and 6. In FIG. 2, σV indicates the relative speed between the tape and the head in the normal playback state. Further, σ and n' indicate the relative speed when the tape speed is different from the normal speed. For example, OQ is double speed, and OQ is still playback.

Since the relative velocity changes in this way, fH changes as described above. The rate of this change is expressed as /1, as is clear from Figure P2. Therefore, if the normal l rotation head speed is VH, and after II correction is vH', then V H = VH ...(2)
It is indicated by. In other words, OP −□ vH”vH”(OP-PQcosi9)*Va(1+(
PQ/a))-(3 Divided, a=('P/), and the approximate formula is PQC
OSθ Let us now consider PQ. In the 4-frequency pilot signal tracking method adopted in 8mm video, f
Pilot signals of different frequencies, l, f, , f, , f, are made to correspond to recording tracks and are recorded sequentially (FIG. 5). During playback, pilot signals from adjacent tracks (f and f in the case of Fig. 6) and a reference signal (created inside V'l'R) having the same frequency as the pilot signal recorded on the track to be traced are used. ) Create a tracking error signal based on the beat signals (16KHz and 47KHz) (see Figure 5)
.

This tracking error signal becomes an output as shown in FIG. 4 in response to the deviation of the head (1) in the X direction in FIG.

Here, since PQ is nothing but the velocity component in the tape running direction, PQ is proportional to the change in the tracking error signal. In other words, the amount of change in the tracking error signal can be used to correct the rotating head speed.

In the embodiment shown in FIG. 1, the rotation speed VH of the head motor (21) is converted into voltage by the F/V conversion circuit (41).The output of this F/V conversion circuit (4) is 5).In addition, the comparator circuit (51)
A corrected speed reference voltage (■,) is applied from the fH correction circuit (6).

In the fH correction circuit (6), 1 normal speed reference voltage (Vl
) is the resistance (1 cell), and the tracking error signal (
EV) is applied to one end of the capacitor (C). Then, the voltage at the connection point between the resistor (R) and the capacitor CC) becomes the corrected speed reference voltage (V, ).

In FIG. 1, the head rotational speed VH can be expressed as KV, -t'. And since vt can be expressed as jdanL V, = V, (1+CR) ·mi, the head rotation speed is corrected using the tracking error signal (Ev).

With the above configuration, not only can fH correction be easily performed during special playback such as stills and intermittent slow play, but also the poor track linearity during normal playback is caused by the accuracy of the tape running system, cylinders, and other mechanisms. ) can also compensate for variations in the horizontal synchronization signal.

That is, by using the tracking error signal of the ATF used in 8M video, it is possible to configure the fH correction circuit by simply adding a differentiation circuit.

(g) Effects of the Invention As described above, according to the present invention, an fH correction circuit with a simple configuration can be realized by using the ATF racking error signal, and the effect is great.

[Brief explanation of drawings]

Figure 1 is a block diagram of the embodiment, Figures 2, 3, and 4.
The figure is an explanatory diagram for explaining the principle, and FIG. 5 is a circuit block diagram of a tracking error signal generation circuit. (2)... Head motor, (4)... F/V conversion circuit, (51... Comparison circuit, (6)... fH correction circuit. Dispatcher Sanyo Electric Co., Ltd.

Claims (1)

[Claims] (1) An fH correction circuit comprising a detection means for detecting a change in a tracking error signal representing a deviation of the rotary head with respect to a recorded track during reproduction, and a control means for controlling the rotational speed of the rotary head based on the output of the detection means.