JPS5999891A - Tracking error detecting circuit - Google Patents

Abstract

PURPOSE:To simplify the constitution of a detecting circuit by reversing the switching order of an injecting signal to that of a reproduced pilot signal so as to eliminate the polarity switching circuit at each field of a comparison output. CONSTITUTION:A reversible counter 3 is provided to a tracking error detecting circuit, and an RF switching pulse is inputted to a counter 3. A count mode designating output D is inputted to the counter 3, a high level designated output D is inputted at the reproduction with (4m+1) times speed to attain the subtraction mode and a low level of designated output D is inputted at the reproduction with (4m-1) times speed to form the addition mode. The count output of the counter 3 is inputted to an injection oscillating circuit 4, and the injection signal is inputted to a multiplication circuit 2 in the reverse switching order as a reproducing pilot signal by the circuit 4. The frequency difference component obtained by the multiplication is separated into 16kHz and 46kHz component by a 16kHz filter 5 and a 46kHz filter 6, so as to eliminate the need for a polarity switching circuit at each field and to simplify the circuit constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention provides
The present invention relates to a tracking error detection circuit with a simple configuration for use in 8 mm video that records a tracking pilot signal on a video track.

(b) Conventional technology 8mm video records four types of tracking pilot signals on a video track and a PCM rack instead of a control track, and a DTP servo that controls the vertical position of the video head. , and an ATF servo (capstan servo) that controls the tape speed. The DTP servo operates so that the video head correctly scans the center of the track during normal playback and scans a single track during special playback. Further, the ATF servo controls the rotational phase of the capstan motor in accordance with a tracking error output obtained by reproducing a tracking pilot signal. normal V
In TR, when performing high-speed playback, the divided output of the playback control signal is used as the capstan servo comparison signal, but the dragging error output is used for ATF servo in 8 mm video. This tracking error output is used. This tracking error output uses four types of tracking pilot signal frequencies, and as shown in FIG. 1, the first to fourth tracking pilot signals are defined. That is, the first signal f1 is l Q 2 K H7, and the second signal f2 is 1
111iKH, cl:, third signal f51 (34KH2i
, the fourth signal f4 is 148KH2; As shown in FIG. 2, these signals are cyclically switched at field cycles +E, and the video signal is superimposed and recorded on the signal. This t4. When scanning a track pattern, the difference frequency between the tracking pilot signal recorded on the preceding track and the following track and the tracking pilot signal of the corresponding track is l (3KH
At t, the other becomes 45KH-1. Therefore, the scanning position of the video head with respect to the track is divided into IQKHz two components and four components.
FIG. 3 shows a circuit block diagram of a tracking error detection circuit for normal playback. The playback output is 200xu,i'
; Input to a low-pass filter fl with the following as a passband, and derive a regenerated pilot signal containing a crosstalk component. This old cow pilot signal is transmitted to the multiplication circuit (2
) is input. An injection signal matching the pilot signal frequency of the corresponding track is input to this multiplication circuit. This injection signal is derived by inputting the RF switching pulse to a 2-bit counter (3) and switching the division frequency of the injection signal oscillation circuit (4) based on the counted output.

The multiplication output is filtered by filter (5) at 16 and filter (5) at 46.
6) The difference frequency component of 11.16xHt: input at ζ and 4
The difference frequency components of 6KHK- are separately detected. Both shear wave outputs are input to a comparator circuit (7), their levels are compared, and the comparison output is input to a polarity switching circuit (8).

This polarity switching circuit (8) derives a tracking error output by inverting the switching state for each field using the output of a flip-flop (9) which receives the RF switching pulse as input. The reason why this polarity switching circuit (8) must be provided is that the difference frequency components obtained from the preceding or following tracks are inverted for each field.

The dragging error output obtained from the above circuit is
It is used as a control signal for the DTP servo that controls the displacement of the video/rad in the width direction and the ATF servo that controls the running of the tape.

In such a conventional circuit, a polarity switching circuit (8) must be provided.
Tracking control cannot be executed.

However, this polarity switching circuit (8)
``S switching means must be provided, which results in a complicated circuit and high cost.

(c) Purpose Therefore, the present invention provides a simple tracking error circuit configured to eliminate the polarity switching circuit for each field of comparison output by trapping the switching order of the injection signal in the opposite order to the switching order of the reproduced pilot signal. This is a proposal.

2) Structure As shown in FIG. 4, in the present invention, when reproducing at a speed of (4m+1) times (where m is an integer), the regenerated pilot signal is f1→f2→f3−+f4→...・When reproducing at a speed of <4m-1), the reproduction pilot signal switches in the opposite direction as f4→f5→f2→f1→..., so the injected signal is This is to reverse the switching and reproduction pilot signal switching.

FIG. 5 explains this switching principle.

First, when Pilot A (Pl) switches to the forward direction, following this, a conventional injection signal σ・)
1QKH3; component CF+) obtained by switching
k'': Alternate Q' from the preceding side and the following side.

death.

However, if the injection signal (11) is switched in the reverse direction (τ) as in the present invention, the 1QKH2 component (fl) will always be obtained from the preceding track.

Furthermore, when the regenerated pilot signal cP2) is switched in the reverse direction, the injection signal σ2) that follows it is inputted, and 16xag components (F2>) are obtained alternately, but when injected in the forward direction as in the present invention, If you switch the signal (12), 15
KHX: Components are uniformly obtained from the preceding track.
iru.

Therefore, it is easy to understand that if the injection signal is switched in the reverse order of the switching order of the regenerated pilot signal, the polarity switching circuit that was conventionally required can be eliminated.

The above-mentioned tracking error is based on the case where a single track is played back even when the DT'F servo machine is set up next to the DT'F servo machine. The error output can be 1) each ai control input of TF servo and ATF servo.

However, it goes without saying that even if only the ATF servo is provided, the ATF servo can be controlled manually by averaging the tracking error output.

(e) Examples Hereinafter, the present invention will be explained according to an illustrative embodiment.

FIG. 5 shows a circuit block diagram of a tracking error detection circuit according to an embodiment of the present invention. The features of this embodiment are as follows:
The point is that a reversible counter (3) is used instead of the counter in the conventional circuit.

In this embodiment, when all modes of normal playback or special playback are set, the tape runs at a predetermined healing tape speed. At the same time, the reversible color/tar (31) counting mode is designated according to the tape speed. This designation is made by the counting mode designation output (D), and when playing at 4m + 1x speed, the counting mode designation output of High 1 Novel is output. ) is input to enter the subtraction mode, and during 4m-1 times speed playback, the low level counting mode designation output CD) is input to enter the addition mode. The counter output for counting RF switching pulses (RF) is input to the injection oscillation circuit (4) as in the conventional example.

The injection oscillation circuit (4) inputs the injection signal to the multiplication circuit (2) in a switching order opposite to that of the regenerated pilot signal. Of the difference frequency components obtained by this multiplication,
The 1 (3 KHf component) and the 45 KHf component are separated by filter [5] at 16 and filter (6) at 46.

The 16xat: component is a crosstalk component obtained from the preceding track, and the 46KH: component is a crosstalk component obtained from the following track, and the comparator circuit (
The output of 7) does not require polarity reversal.

(F) According to the present invention, the polarity inversion circuit can be eliminated by simply switching the injection signal in the reverse switching order from that of the regenerated pilot signal, and the effect is excellent.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the tracking pilot signal frequency,
Figure 2 is an explanatory diagram of switching the tracking pilot signal.
FIG. 3 is a circuit block diagram of a conventional tracking error detection circuit, FIG. 4 is a diagram explaining the regenerated pilot signal, FIG. 5 is a diagram explaining polarity of tracking error, and FIG. 6 is a circuit block diagram of the tracking error detection circuit of the present invention. Reveal each figure. Explanation of main figure numbers (3)...Reversible counter, (4)...Injection oscillation circuit, (2)...Multiplication circuit, (5)...Filter at 16, (6)... 46, filter, (7)...comparison circuit. 2nd diagram 2ji2 0-1----------
−−−−−−−−−−−−−−−−−−−−−−−−−−
1----Figure δ

Claims (1)

[Claims] In a video tape recorder that forms a recording track in units of fields together with a video signal while changing the racking pilot signal frequency at a field period, during playback at (4m+1) times the speed (m is an integer), An injection oscillation circuit that supplies the injection signal in the reverse switching order and supplies the injection signal in the same order as during recording during (4m-1) double speed playback, a multiplication circuit that multiplies the injection signal and the reproduction pilot signal, and a multiplication output. 15KHz component and 46KHz component: Separate and derive the components with a filter at 16 and a filter at 46,
A tracking error detection circuit comprising a comparison circuit that compares the output levels of both filters and outputs a direct tracking error output.