Automatic tracking device for video cassette tape recorder

Claim 2

An automatic tracking device for a video cassette tape recorder comprising: a rotating head drum; first and second video heads mounted on said rotating head drum having different azimuth angles; said first and second video heads tracking corresponding video tracks on a video tape to reproduce first and second FM video signals, respectively; each of said video heads having a width larger than a width of said video tracks; error voltage detector means, operatively connected to said first and second video heads, for detecting a presence of an error voltage in said first and second FM video signals produced by said first and second video heads; and servo circuit control means, operatively connected to said error voltage detector means, for controlling a phase of a capstan motor to minimize said error voltage in said first and second FM video signal; said error voltage detector means delaying one of said FM video signals produced by said first and second video heads such that said first and second FM video signals are compared together.

Claim 3

The automatic tracking device as claimed in claim 1 further comprising: head switching signal means, operatively connected to said error voltage detector means, for producing a head switching signal; said error voltage detector means including, inverter means, operatively connected to said head switching signal means, for inverting said head switching signal; monostablevibrator means, operatively connected to said inverter means and said head switching signal means, for producing sample pulse signals in accordance with said head switching signal and the inverted head switching signal; envelope detector means, operatively connected to said first and second video heads, for detecting an envelope of said first and second FM video signals and producing first and second voltage signals representing the detected envelope of said first and second FM video signals, respectively; sample and hold means, operatively connected to said envelope detector means and said monostablevibrator means, for sampling and holding either said first voltage signal or said second voltage signal in accordance with said sample pulse signals, thereby causing said first and second voltage signals to be simultaneously present at outputs of said sample and hold means; and comparator means, operatively connected to said sample and hold means, for comparing said first and second voltage signals and producing said error voltage from the comparison.

Claim 4

The automatic tracking device as claimed in claim 2, wherein said head switching signal has a frequency of 30 Hz.

Claim 5

The automatic tracking device as claimed in claim 2, wherein said error voltage detector means causes said servo control circuit to stop the capstan motor to produce a still picture only when said first and second voltage signals are determined to have a same magnitude.

Claim 6

The automatic tracking device as claimed in claim 2, wherein said sample and hold means sample and hold both said first and second voltage signal.

Claim 7

An automatic tracking device for a video cassette tape recorder comprising: a plurality of video heads mounted on a rotating head drum, each video head having a different azimuth angle and a width larger than a width of a video track on the video cassette tape, said video heads producing a FM video signal from the video cassette tape; envelope detector means, operatively connected to said plurality of video heads, to detect an envelope of said FM video signals and to produce a separate voltage signal for each detected envelope; sample and hold means, operatively connected to said envelope detector means, for sampling and holding each voltage signal produced by said envelope detector means, thereby causing said voltage signals to be simultaneously present at outputs of said sample and hold means; and motor control means, operatively connected to said sample and hold means, for comparing said voltage signals to determine an error between magnitudes of said voltage signals; said motor control means controlling a speed of tracking in accordance with said error.

Claim 8

An automatic tracking device for a video cassette tape recorder comprising: a plurality of video heads mounted on a rotating head drum, each video head having a different azimuth angle and a width larger than a width of a video track on the video cassette tape, said video heads producing a FM video signal from the video cassette tape; envelope detector means, operatively connected to said plurality of video heads, to detect an envelope of said FM video signals and to produce a separate voltage signal for each detected envelope; sample and hold means, operatively connected to said envelope detector means, for sampling and holding each voltage signal produced by said envelope detector means, thereby causing said voltage signals to be simultaneously present at outputs of said sample and hold means; and motor control means, operatively connected to said sample and hold means, for comparing said voltage signals to determine an error between magnitudes of said voltage signals; said motor control means controlling a speed of tracking in accordance with said error.

Claim 9

The automatic tracking device as claimed in claim 6 further comprising: head switching signal means for producing a head switching signal; inverter means, operatively connected to said head switching signal means, for inverting said head switching signal; and monostablevibrator means, operatively connected to said inverter means and said envelope detector means, for producing sample pulse signals in accordance with said head switching signal and the inverted head switching signal, said sample pulse signals controlling the sampling and holding operations of said sample and hold means.

Claim 10

The automatic tracking device as claimed in claim 7, wherein said head switching signal has a frequency of 30 Hz.

Claim 11

The automatic tracking device as claimed in claim 6, wherein said motor control means comprises: comparator means, operatively connected to said sample and hold means for comparing said voltage signals and producing said error from the comparison; and servo control means, operatively connected to said comparator means, for controlling a phase of a capstan motor in accordance with said error.

Claim 12

The automatic tracking device as claimed in claim 6, wherein said motor control means controls a speed of rotation for said rotating drum.

Claim 13

The automatic tracking device as claimed in claim 6, wherein said motor control means controls a speed of the video tape.

Claim 16

The method as claimed in claim 12, further comprising the steps of: (h) producing a head switching signal; (i) inverting the head switching signal; and (j) producing sample pulse signals in accordance with the head switching signal produced in said step (h) and the inverted head switching signal produced in said step (i); wherein the sample pulse signals control the execution of said step (e).

Claim 17

The method as claimed in claim 13, wherein said step (h) produces a head switching signal having a frequency of 30 Hz.

Claim 18

The method as claimed in claim 12, wherein said step (g) controls a speed of rotation of the rotating drum.

Claim 19

The method as claimed in claim 12, wherein said step (g) controls a speed of the video cassette tape.