JPS6286980A - Capstan phase control method in magnetic recording and reproducing equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a helical scan type magnetic recording/reproducing device capable of fast-forwarding playback in the forward or reverse direction, and particularly relates to a helical scan type magnetic recording/reproducing device capable of fast-forwarding playback in the forward or reverse direction. The present invention relates to a capstan phase control method suitable for use in an auto-tracking magnetic recording/reproducing device that performs tracking control using the present invention.

[Background of the invention]

In recent years, in addition to the normal recording and playback function, magnetic recording and playback devices (hereinafter referred to as VTRs) perform playback while feeding the tape in the forward or reverse direction at a faster speed than the normal recording and playback speed (hereinafter referred to as VTR). Some devices are known that have a function that enables playback (referred to as fast-forward playback). By using this function, it is convenient to grasp the recorded contents of the tape and find the necessary parts in a short amount of time.

When performing fast-forward or playback, one video head scans multiple tracks.

Noise occurs during a period when a track recorded by a head with an azimuth different from that of the head being scanned is scanned. This appears as noise par on the playback screen. This noise par usually oscillates on one screen.

), the screen would flow and become very unsightly, so
Conventionally, methods have been proposed in which the noise par is always fixed on the screen to make the screen easier to view.

As a means to achieve this, 607 control pulses recorded on the control track at the longitudinal end of the tape are detected, and the control pulses are changed to N according to the fast forward speed ratio N.
The reference signal (30H
The rotational phase of the capstan motor was controlled using this phase error signal. however.

The new standard VTR, in other words, ATF (Automatic
In VTRs that have introduced a control system (Track Finding), the magnetic tape used does not have control tracks at the ends in the longitudinal direction, so it is no longer possible to use the method described above to perform phase control by dividing the reproduction control signal. Ta.

In addition, the control pulse is used to control tranoquin y,
(Fast forward) An example of an invention aimed at improving image quality during playback is the one described in Japanese Patent Application Laid-Open No. 53-125026.

[Purpose of the invention]

It is an object of the present invention to also provide a VTR equipped with the above-mentioned control trunkless A'I'F control system.
When playing fast forward or backward.

An object of the present invention is to provide a capstan phase control method that can always fix the noise per f on a screen at a fixed position.

[Summary of the invention]

In order to achieve the above object, the present invention detects the envelope of the reproduced video signal during fast-forward υ reproduction to form a signal (hereinafter referred to as a pseudo CTL signal) corresponding to the control pulse in the conventional example. Based on this, a phase error signal for the capstan phase control system is formed to control the rotational phase of the capstan motor during playback (fast-forward).

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram schematically showing a standard speed playback/fast forward playback system in '/TR to which the present invention is applied. In this embodiment, a VTR employing the above-mentioned ATF' control system is used as an auto-tracking system.

In FIG. 1, 1 is a video tape, and 2.3 is a rotary video head, which are mounted on a one-rotation cylinder 4 at a distance of 180 degrees from each other. This rotating cylinder 4 is rotationally driven by a cylinder motor 5, and rotates in the direction of the dashed arrow. The rotating cylinder 4 is attached to a rotating shaft inclined with respect to the longitudinal direction of the video tape 1, and rotates at a frame frequency of 30&. Further, the videotape 1 is driven by the capstan 6 and runs in the direction of the solid arrow. This capstan 6 is rotationally driven by a capstan motor 7. The reproduced signal RF taken out from the video tape 1 by the rotating video head 2.3 is sent to the amplifier 8 and amplified. This amplified reproduction signal RF is transmitted to the video signal reproduction circuit 9
and low pass filter (LPF') 1
0, and pseudo-CT related to the present invention, which will be explained in detail later.
L signal forming circuit 11 (C is sent. Video signal reproducing circuit 9
Then, the reproduced video signals RF from the video heads 2 and 6 are alternately switched for each field by the head switching signal SW output from the head switching signal forming circuit 14, which will be described later, to form a continuous video signal. . terminal 12
is an output terminal for the generated reproduced video signal.

Next, the operation of the servo system will be explained. The servo system is composed of a cylinder servo and a capstan servo, and each servo is composed of a speed control system and a phase control system. In the cylinder servo, the following operations are mainly performed in the cylinder servo device 16. That is, for the speed control system, a frequency generation signal (signal Df) from the cylinder motor 5 is frequency-discriminated to generate a speed error signal, and for the phase control system, a reference signal corresponding to the video frame frequency and the aforementioned head switching are used. A phase error signal is generated by comparing the phase with the signal SW. Then, the control voltage Dc obtained by adding the two is supplied to the cylinder motor drive circuit 15, and the cylinder motor 5 is controlled to rotate accurately at a frame frequency of 307. Here, the rotational phase of the cylinder motor 5, that is, the rotational phase of the video head 2.30, is detected by the tack head 13, and based on this, the aforementioned head switching signal forming circuit 14 selects a pair of video heads 2.30 and 2.30. ! 1
A head switching signal SW representing switching timing for each field is generated.

Next, the operation of the capstan servo during reproduction will be explained.

As for the speed control system, the frequency power generation signal Cf from the capstan motor 7 is frequency-discriminated by the frequency discrimination circuit 17 to generate a speed error signal CP' in the same way as the cylinder servo described above, and as for the phase control system, as will be described later. A phase error signal C1i is generated.

Then, both of them are added by an adder 20, and the resulting control voltage is supplied to a capstan motor drive circuit 21, and the capstan motor 7 is controlled by negative feedback to perform trunking control.

Next, a method of generating the phase error signal Ci will be explained. In this embodiment, the method for generating this phase error signal C1 is as follows:
It differs between normal playback and fast forward playback.

First, normal playback will be explained. As mentioned above, the reproduced signal RF output from the amplifier 8 is passed through the Ronox filter 1.
0, the high-frequency video signal is removed by the low-pass filter 10, and only the pilot signal recorded on each track on the tape 1 during recording is extracted, and then supplied to the ATF processing circuit 18. Next, the ATF processing circuit 18 generates a tracking error signal, that is, a phase error signal C1N, from the difference in the side-leading amount of the reproduced pilot signals from one adjacent track, although detailed explanation is omitted.
form. This phase error signal C1N is
9 to the adder 20 as a phase error signal C1 during normal reproduction. Here, the switch circuit 19 is operated by a control signal from the controller 22.

It is controlled to close to the N contact during normal playback and to close to the S contact during fast forward playback. Next, there is a method for forming the phase error signal C1 during fast-forward playback.
In the L signal forming circuit 11, a 30 Hz pseudo CTL signal PCT including phase information of the capstan running system is formed from the reproduced signal RF multiple outputted from the amplifier 8, and then this pseudo CTL signal PCT and a 30 Hz reference signal are combined. A phase error signal forming circuit 26 compares the phases of the two signals. The formed phase error signal Cis is sent to the adder 20 via the switch circuit 19. The detailed operation of the pseudo CTL signal forming circuit 11 will be described later, but the pseudo CTL signal PcT of 30 Hz is always obtained in response to control commands from the controller 22 even in various fast forward playback speed multipliers and forward/reverse modes. It has become. As explained above, with the configuration shown in FIG. 1, phase control can be reliably applied to the capstan running system even during fast-forward playback.

Next, the phase control operation during fast-forward playback in this embodiment will be explained in more detail.

FIG. 2 is a schematic diagram showing the head scanning locus for each turn of the recording track during fast-forward playback. Figure 2 f
al shows the case of 5x normal rotation, and Fig. 2, etc.) shows the case of 5x reverse rotation. In the figure, A is the track recorded by the video head 2, and B is the trunk recorded by the video head 3, and the azimuth recording is opposite to each other. Also, (a) shows the scanning locus of the video head 2 having the same azimuth as the trunk A, and (b) shows the scanning locus of the video head 3 having the same azimuth as the track B.

Further, FIG. 3 shows the envelope waveform of the reproduced video signal RF during the above-mentioned fast-forward reproduction and the head switching signal forming circuit 1.
4 is a waveform diagram showing the waveform of a 30 Hz head switching signal SW output from the head switching signal SW. 3(a) corresponds to the scanning of FIG. 2 [a+] in the case of 5 times normal rotation, and FIG. 3 et al.) corresponds to the scanning of FIG. 2 tb) in the case of 5 times reverse rotation.

As is clear from FIG. 3, in the case of normal rotation of 5x fast forward playback, two noise bars appear in one screen, and in the case of reverse rotation, three noise bars appear in one screen. In this way, it is generally known that in the case of N-times fast-forward playback, the number of noise bars that appear on one screen becomes too busy (however, N is an integer of IN+≧2, and A plus sign indicates a rotation, a minus sign indicates a reversal).

FIG. 4 is a block diagram showing in detail the above-mentioned pseudo CTL signal forming circuit 11 and phase error signal forming circuit 23, which are involved in phase control during fast-forward playback in the present invention. Fourth
As shown in the figure, the pseudo CTL signal forming circuit 11 includes an envelope detection circuit 24, a zero cross amplifier circuit 25. It is composed of switch circuits 26 and 29 and frequency dividing circuits 27 and 28.

The operation will be explained based on the signal waveform diagram of each part shown in FIG. Here, a method for forming a pseudo CTL signal in the case of 5x forward forward playback will be explained. The reproduced signal RF from the amplifier 8 inputted to the terminal 32 is as follows.

The signal is input to the envelope detection circuit 24, and its envelope is detected and output as a signal VD shown in FIG. The signal VD is zero-cross amplified by a zero-cross amplifier circuit 25 and output as a pulsed signal. Here, in the case of 5x forward rotation, the number of noise bars on one screen is 2 as described above, which is 6D, so the envelope detection circuit 2
The frequency of the signal VD output from 4 is 4X30=120
Hz.

Therefore, the frequency of the signal is also 120Hz.

To state this generally, as is clear from the above, in the case of N-times fast-forward playback, the signal frequency is 1N-11X30Hz (however, N is IN+≧
It is an integer of 2, and forward rotation is represented by a plus sign, and reverse rotation is represented by a minus sign). Therefore, in general, in the case of N-times fast forwarding, the signal PD is frequency-divided by lN-11 to generate a 30Hz pseudo (
1c'I'L signal PC? can be generated. Since this frequency division number is different for forward rotation and reverse rotation, the switch circuit 2
6.29 is provided and the command signal from the controller 22,
This frequency division number is changed over. In other words, both switch circuits 26 and 29 are closed to the C contact in the case of 5x forward fast forward playback, and the signal Pn is divided by Nc = 4 in the frequency divider circuit 27, and in the case of 5x reverse fast forward playback. .

The switch circuits 26 and 29 are both closed to R contacts, and the signal Pni frequency dividing circuit 28 divides the frequency by NR=6, so that a pseudo C'I'L signal PCT of 30 Hz is always obtained in both modes. Note that since FIG. 5 shows the case of 5x forward rotation and fast forwarding, the switch circuit 26 shown in FIG.
．． 29 is closed to the C contact, and the frequency division number Nc of the frequency dividing circuit 27 is N.
c=4.

Next, a description will be given of the phase error signal forming circuit 23 which forms the shadow of the phase error signal Cis'x using the pseudo CTL signal PCTk. As shown in FIG. 4, the pseudo CTL signal PCT from the pseudo CTL signal forming circuit 11 is as follows.

The signal is input as a comparison signal to the phase comparator 30 in the phase error signal forming circuit 23. In the phase comparator 30.

a 30Hz reference signal S output from the reference signal generation circuit 33 and a pseudo CTL signal PCT as the comparison signal;
! : are compared in phase, and a phase error signal C1's k is generated according to the phase difference. Normally, this signal C1'a includes an alternating current component, so the alternating current component is cut by the low-pass filter 31, and the phase error signal C1s is output from the terminal 34 as a smoothed DC voltage.

The subsequent operation is as described above with reference to FIG. Input to motor 7, rotation phase of capstan motor 7.

That is, the rotation phase of the capstan 6 is controlled. By accurately controlling the phase of the capstan travel system in this manner, the noise bar that appears on the screen during fast-forward playback can be fixed at a fixed position.

[Effects of the Invention J] As explained above, according to the present invention, even in a VTR equipped with a control trackless ATF control system, the pseudo C
By using the TL signal, it is possible to control the phase of the tape running during fast-forward playback, so it is possible to prevent the fluctuation and flow of multiple noise pars that appear on the screen, and to fix them on the screen. The screen during playback can be made very easy to see.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a schematic diagram showing the track pattern and the head scanning locus during 5x fast forward playback, and FIG. 6 is a waveform diagram showing the waveform of the envelope of the playback signal and the waveform of the head switching signal during 5x fast forward playback. Figure 4 is the pseudo-CTL of Figure 1.
FIG. 5 is a block diagram showing a signal forming circuit and a phase error signal forming circuit, and FIG. 5 is a waveform diagram showing signal waveforms of operation signals of each part in FIG. 4. 6...Capstan, 7...Capstan motor. 11... Pseudo CTL signal forming circuit, 19.26.29... Switch circuit. 23... Phase error signal forming circuit, 24... Envelope detection circuit, 25... Zero cross amplifier circuit. 27.28... Frequency divider circuit. 30... Phase comparator, 51... Low pass filter, 33... Reference signal generation circuit. Representative Patent Attorney Katsuo Ogawa ＼、゛、゛deceased１
Mouth Output ITII No. 51 Sword 2□ ” ° “

Claims (1)

[Scope of Claims] 1) It has a capstan for running a magnetic tape and a capstan motor for driving the capstan, and the tape running speed is higher than the recording speed to perform forward rotation or reverse playback. In a helical scan magnetic recording and reproducing device capable of fast-forward reproduction, a detection means detects an envelope of a reproduction signal reproduced from a video head;
A waveform shaping means that shapes the waveform of the detected signal, a frequency dividing means that divides the waveformed signal into a predetermined frequency, and a phase comparison between the frequency-divided signal and a reference signal that provides a reference phase, and the phase difference is calculated. and a phase comparison means for outputting a corresponding phase error signal, and the rotational phase of the capstan motor is controlled by the phase error signal from the phase comparison means during the fast-forward playback. Capstan phase control method in magnetic recording and reproducing devices. 2) In the capstan phase control method according to claim 1, when the tape running speed during fast-forward playback is set to N times the speed during recording (N is a positive integer of N≧2), A capstan phase control system in a magnetic recording/reproducing apparatus, wherein the frequency dividing means switches the frequency division number to N-1 during normal fast-forward playback and N+1 during reverse fast-forward playback.