KR900006672B1 - Automatic tracking circuit in video tape recorder - Google Patents

Abstract

A first (2) and second (3) image heads having different azimuth angles reproduce the radio freq. signal recorded on the video tape. The width of the head is greater than the one of the video track. The first head (2) is placed on upper side of reference line (4) which length is as much as the track width (9) and the second head (3) on the reference line. The magnitude and error voltage (Eu) of the video signal is detected by a differential amplifier (17) and envelope line detector (14) to control the phase of the capstan motor.

Description

Automatic tracking device of video cassette recorder

1 is a front view showing an embodiment in which the first and second image heads are installed in the rotating head drum by the automatic tracking device of the present invention.

(A) and (b) of FIG. 2 to FIG. 4 show the trajectory of the video head installed by the automatic tracking device of the present invention for tracking the track of the video tape and the magnitude of the high frequency signal RF reproduced according to the tracking trajectory. Illustrated diagram showing.

5 is a block diagram showing an embodiment of an error voltage detection circuit by the automatic tracking device of the present invention.

6 is a detailed circuit diagram of FIG.

(A)-(i) of FIG. 7 is a waveform diagram of each part of FIG. 5 and FIG.

8 is a circuit diagram showing another embodiment of the error voltage detection circuit by the automatic tracking device of the present invention.

(A) and (b) of FIG. 9 illustrate the trajectory of the video head tracking the track of the video tape by the automatic tracking device of the present invention and the magnitude of the radio frequency (RF) signal reproduced according to the tracking trajectory. Degree.

10 is a plan view showing another embodiment in which the first and second image heads are installed in the rotating head drum by the automatic tracking device of the present invention.

* Explanation of symbols for main parts of the drawings

1: Rotating Head Drum 2: First Image Head

3: second image head 4: reference plane

5: video tape 10-13: mono multivibrator

14: envelope detector 15,16: sample hold circuit

17: differential amplifiers A, B: video track

D: Width of the first and second video heads P: Width of the video track

HS: 30Hz Head Switching Signal RF: Regenerative High Frequency Signal

EV: Error Voltage

The present invention provides a video cassette recorder which modulates an image signal into a high frequency signal and records and reproduces it on a video track of a videotape, wherein the rotating head drum plays back a video track of a videotape recorded with a high frequency signal (RF: Raido Frequency). The present invention relates to an automatic tracking device of a video cassette recorder in which two video heads installed in the track accurately track a high frequency signal (RF) on a video tape.

In general, when a video cassette recorder plays back a high frequency signal recorded on a video tape of a videotape, two video heads installed on a rotating head drum must accurately track the video track, so that the size of the high frequency signal reproduced is the largest and clearest. The noise signal does not appear on the playback screen.

To this end, conventionally, when recording a high frequency signal on a video tape, a control signal is recorded in a control track divided into a predetermined width at the bottom of the video tape. When a high frequency signal is reproduced, the recorded control signal is reproduced for tracking. The servo circuit has a capstan delay, which is set by the variable resistor, and inputs to the servo circuit of the capstan motor which drives the video tape so that the two video heads installed on the rotating head drum accurately track the video track of the video tape. The rotation speed of the motor was controlled.

However, in the conventional tracking device as described above, the control signal is separately recorded on the video tape to record and reproduce the control signal, and the delay of the control signal reproduced by varying the tracking variable resistor while the user watches the playback screen. It was very difficult to adjust the tracking to an optimal state because the time had to be set, and it had a lot of troublesome users.

In addition, there are various tracking devices that automatically adjust the tracking so that the video head accurately tracks the video tracks of the video tape. However, there are also defects that need to set control tracks on the video tape to record control signals and play them back. there was.

It is an object of the present invention to eliminate the hassle of adjusting the tracking as well as eliminating the need to partition the control track on the videotape by automatically adjusting the tracking without using a control signal.

It is another object of the present invention to stop the running of a video tape, to increase the magnitude of the high frequency signal reproduced by the two video heads during the stop reproduction for reproducing the high frequency signal, and to make the noise signal hardly appear on the still reproduction picture.

According to the present invention having the above object, the width of two video heads installed in the rotating head drum is larger than the width of the video track of the video tape, and the error voltages are compared by comparing the magnitudes of the high frequency signals reproduced by the two video heads. Can be achieved by detecting.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a front view showing an embodiment in which the image head is installed on the rotating head drum by the automatic tracking device of the present invention. Here, reference numeral 1 denotes a rotating head drum, reference numerals 2 and 3 denote first and second image heads, and the first and second image heads 2 and 3 have different azimuth angles. It is installed on the rotating head drum (1) at an angle of l80 ° to each other.

Then, the width D of the video heads 2 and 3 is formed to be slightly larger than the width P of the video track of the video tape, that is, approximately 1.5 times larger than the width of the track. The height of 3) makes the lower end of the image head 3 coincide with the reference plane 4, and the upper end of the first image head 2 is installed by the width P of the track higher than the reference plane 4.

Here, the first and second image heads 2 and 3 may be installed by changing their positions.

According to the present invention, the first and second image heads 2 and 3 are video as shown in FIG. 2A according to the head switching signal HS of 30 Hz shown in FIG. 2B. When the video tracks A and B of the tape 5 are accurately tracked, the widths of the video tracks A and B, which the first and second video heads 2 and 3 respectively track, are the same and reproduced. The magnitude of the high frequency signal is the same, and when the running speed of the video tape 5 is high, that is, as shown in FIG. 3A, the first and second image heads 2 and 3 are connected to the video track A. FIG. When tracking (B) is slightly later, the width of the video track B tracked by the second video head 3 is narrower than the width of the video track A tracked by the first video head 2. As shown in (b) of FIG. 3, the magnitude of the high frequency signal reproduced by the second image head 3 is smaller than that of the high frequency signal reproduced by the first image head 2, and (b) of FIG. As shown in When the first and second video heads 2 and 3 track the video tracks A and B slightly earlier, the magnitude of the high frequency signal reproduced by the first video head 2 is inversely different. The image head 3 becomes smaller than the size of the high frequency signal reproduced.

In addition, while the first and second image heads 2 and 3 track the video tracks A and B, respectively, the adjacent video tracks B and A are also tracked. Since the azimuth angle of) and the azimuth angle at which the video track B recorded the high frequency signal are different from each other, the high frequency signal recorded on the video track B is not reproduced by the first video head 2, and the video track The high frequency signal recorded in (A) is not reproduced by the second video head 3 as described above.

5 and 6 illustrate an error voltage according to the present invention for detecting a phase error voltage of a capstan motor when the high and high signals reproduced by the first and second image heads 2 and 3 are mixed and input. A block diagram and a detailed circuit diagram showing an embodiment of a detection circuit, in which the inverter I1 inverts the 30 Hz head switching signal Hs and the 30 Hz head switching signal Hs and the inverter I1. Mono-multivibrator integrated device (LM1) (LM2), resistors (R1, R2), (R3, R4) and large capacitors (C1-C3) (C4-C6) for outputting a pulse signal of a predetermined width in accordance with the output signal Mono multivibrator integrated element (LM3) (LNI4) for outputting a sampling pulse signal in the falling section of the mono multivibrator 10 (11) and the output signal of the mono multivibrator (10) (11). , Monomultivibrators 12 and 13 formed of resistors R3, R4, R5, R6, and large capacitors C7-C9 and C10-C12, and a reproduced high frequency signal ( An envelope detector 14 comprising a diode D1, a capacitor C13, and a resistor R9 for detecting a capture line of the RF; and the envelope detector 14 according to an output signal of the mono multivibrators 12, 13; A sample holding circuit (15) and a sample holding circuit (15) and a sample holding circuit (15) of the sample holding integrated device (SH1) (SH2) and capacitor (C14) (C15) for sampling and outputting the output signal. Comparing the magnitude of the output signal of l6), it consists of the operational amplifiers OP1 and OP2 for detecting the error voltage EV and the differential amplifiers 17 composed of the resistors R10 to R15.

In the description of Fig. 6, reference numeral Vcc denotes a power supply terminal. According to one embodiment of the present invention configured as described above, when power is applied to the power supply terminal Vcc, and the 30Hz head switching signal HS as shown in FIG. 7A is input, the input 30Hz head switching signal is input. (HS) is differentiated through the differentiation of the capacitor (C1) and the resistor (R1) of the mono multivibrator 10 is applied to the trigger terminal (TI1) of the integrated device (LM1) for the mono multivibrator, and 30Hz head switching signal (HS) is inverted via inverter I1 as shown in FIG. 7 (b), is differentiated through a differentiator consisting of capacitor C4 and resistor R3 of monomultivibrator I1 and monomultivibrator Since the monolith vibrator integrated device LM1 and LM2 are applied to the trigger terminal TI2 of the integrated device LM2 according to the time constants of the resistors R2 and R3 and the capacitors C2 and C5, As shown in Figs. (C) and (d), a pulse signal is output to the output terminals OUT1 and OUT2, The pulse signal output from the integrated device LM1 (LM2) for the normal vibrator is a differentiator consisting of a capacitor C7 and a resistor R5 and a capacitor C10 and a resistor R7 of the monomultivibrator 12 and 13. The derivatives are respectively differentiated and input to the trigger terminals TI3 and TI4 of the monomultivibrator integrated device LM3 and LM4, so that the monovibrator integrated device LM3 and LM4 are connected to the resistors R6 and R8. According to the time constants of the capacitors C8 and C9, the sampling fill signal is output to the output terminals OUT3 and OUT4 as shown in FIGS. 7E and 7F, and the sample hold circuit 15 ( 16 are respectively applied to sampling terminals SP1 and SP2 of the sample-hold integrated elements SH1 and SH2.

The high frequency signal reproduced while the first video head 2 and the second video head 3 track the video tracks A and B of the video tape 5 in synchronization with the 30 Hz head switching signal HS. RF is inputted, and assuming that the envelope detector 14 detects an envelope as shown in (g) of FIG. 7 from the input high price signal RF, the sample hold circuit 15, 16 The sample-hold integrated element SH1 and SH2 output the output signal of the envelope detector 14 in accordance with the sampling pulse signal output from the integrated element LM3 and LM4 of the mono multivibrator 12 and l3. Samples are stored in the capacitors C14 and C15, respectively, and then output as shown in FIG. 7 (h) and (i), and the output of the sample-hold integrated element SH1 configured in the sample-hold circuit 15. The signal is inverted through the resistors R10 and R11 and the operational amplifier OP1 configured in the differential amplifier 17 and then input to the inverting input terminal (-) of the operational amplifier OP2 through the resistor R12. The output signal of the sample-hold integrated element SH2 configured in the sample-hold circuit 16 is input to the inverting input terminal (-) of the operational amplifier OP2 through the resistor R13 of the differential amplifier 17. The amplifier OP2 outputs an error voltage EV, that is, outputs an error voltage EV corresponding to a difference between the output signals of the sample-hold integrated devices SH1 and SH2. EV) is input to the servo circuit so that the first image head 2 and the second image head 3 track the capstan motor or drum motor so as to accurately track the video tracks (A) (B) of the video tape (5). In other words, the size of the reproduction high frequency signal RF of the first image head 2 sampled and output by the sample-hold integrated element SH1 of the sample-hold circuit 15 is equal to that of the sample-hold circuit 16. If the integrated device SH2 is larger than the reproduction high frequency signal RF of the second image head 3 sampled and output, the video tape 5 is slowed down. If the servo circuit slowly controls the phase of the canton motor and the reproduction high frequency signal RF of the first image head 2 is smaller than the reproduction high frequency signal RF of the second image head 3, The servo circuit quickly controls the phase of the capstan motor so that the videotape 5 is driven quickly so that the first and second image heads 2 and 3 are provided with the video tracks A and B of the videotape 5. Make sure you track correctly.

8 shows error voltage detection according to the present invention for detecting the phase error voltage of the capstan motor when the high price signals RF reproduced by the first and second image heads 2 and 3 are input. As a block diagram showing another embodiment of the circuit, the envelope of the high frequency signals RF1 and RF2 reproduced by the first and second image heads 2 and 3 are respectively detected, and a sample and hold circuit ( The envelope detectors 141 and 142 input to the 15 and 16 are configured.

According to another embodiment of the present invention configured as described above, the first and second image heads 2 and 3 track the high frequency code RF1 and RF2 while tracking the video tracks A and B of the video tape 5, respectively. When regenerated and input to the envelope detectors 141 and 142, the envelope detectors 141 and 142 detect the envelope of the reproduction high frequency signals RF1 and RF2, and the detected envelope is the sample hold circuit 15 (l6). ) Is sampled according to the output signal of the mono multivibrator 12 (13), is compared in the differential amplifier 17 to output the phase error voltage (EV) of the capstan motor.

In the above description, the phase of the capstan motor is controlled by the error voltage EV output from the differential amplifier 17. However, in the embodiment of the present invention, the error voltage EV output from the differential amplifier 17 is rotated. The first image head 2 and the second image head 3 are controlled by the video track A of the video tape 5 by inputting the head motor 1 to the servo circuit of the drum motor for controlling the drum drum. (B) can also be controlled to accurately track.

In the case of the still reproduction using the present invention as described above, the output signals of the sample hold circuits 15 and 16 are inputted to a comparator and compared, and the magnitudes of the compared two signals are the same, that is, (a) of FIG. The first and second image heads 2 and 3 track the video tracks A and B of the video tape 5, as shown in FIG. And when the driving of the video tape 5 is stopped by stopping the driving of the capstan motor when the magnitudes of the high frequency signals RF reproduced by the second image heads 2 and 3 are the same, the first and second images. The width of the video tracks A and B tracked by the heads 2 and 3 is widest so that the size of the reproduction high frequency signal RF becomes very large, and the noise signal hardly appears on the reproduction screen.

In carrying out the present invention, as shown in FIG. 10, a high frequency signal (RF) recording video head (6) 7 is provided in the rotating head drum (1), and the recording video head (6) is provided. The first and second image heads 2 and 3 may be provided and used while maintaining a constant angle θ with (7).

As described in detail above, the present invention forms the width of the first and second image hedges slightly larger than the width of the video track, and reproduces the first and second image heads respectively while the first and second image heads track the video track. By comparing the magnitudes of the two signals and adjusting the tracking so that the two signals are the same, the control signal is not used when adjusting the tracking. Therefore, it is not necessary to record and reproduce the high frequency signal by dividing the control track separately on the video tape. In addition, in the case of still playback, the high frequency signal RF can be reproduced very largely, so that a noise signal hardly appears on the playback screen.

Claims (3)

The first and second image heads 2 and 3 having different azimuth angles are installed in the rotating head drum 1 at an angle of 180 °, and the first and second image heads 2 and 3 are In a video cassette recorder in which a high frequency signal (RF) is reproduced while tracking video tracks (A) and (B) of a video tape 5, the widths of the first and second image heads 2 and 3 ( D) is formed larger than the width (P) of the video tracks (A) (B), the upper end of the first image head (2) is the width (P) of the video tracks (A) (B) at the reference plane (4) The second image head 3 is installed at a position as high as possible, and the second image head 3 is installed at a position at which a lower end thereof coincides with the reference plane 4, while the first and second image heads 2 and 3 are connected to the video track. The error voltage detection circuit compares the magnitudes of the high frequency signals RF reproduced in (A) and (B) to detect the error voltage EV, and the servo circuit is set so that the detected error voltage EV is minimized. To control the phase of the capstan motor. Automatic tracking apparatus of the video cassette recorder, characterized in that the configuration. The error voltage detection circuit of claim 1, wherein the error voltage detection circuit has a predetermined width in accordance with an inverter I1 for inverting the 30 Hz head switching signal HS and the output signal of the inverter 30 in the 30 Hz head switching signal HS. Monaural vibrator (10) (11) which outputs a pulse signal, and monomultivibrator (12) (13) which outputs a sampling pulse signal in a falling section of the output signal of the monomultivibrator (10) (11); An envelope detector 14 for detecting the envelope of the high frequency signal RF reproduced by the first and second image heads 2 and 3, and the envelope according to the output signal of the mono multivibrator 12, 13; Sampling hold circuits 15 and 16 for sampling and outputting the output signal of the detector 14 and output signals of the sample hold circuits 15 and 16 are compared with each other, and an error corresponding to the difference between the two signals. Video cassette recorder comprising a differential amplifier 17 for outputting a voltage EV Auto-tracking device. 3. The driving of the video tape 5 according to claim 2, wherein the magnitudes of the output signals of the sample holding circuits 15 and 16 are compared during the stop reproduction, and the driving of the capstan motor is stopped when the magnitudes of the two signals are the same. Automatic tracking device for a video cassette recorder, characterized in that it is configured to stop.

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