KR890004244B1 - Slow regeneration method - Google Patents

Abstract

A video tape recording-reproducing apparatus includes a first main rotary head and a second main rotary head whose azimuth angles are different to each other, a first sub-rotary head fixed adjacent the first main rotary head, and a second sub-rotary head fixed adjacent the second main rotary head, wherein in the reproduction mode a magnetic tape may be driven at a speed different from the speed in the recording mode, and wherein lower signal level sections of the reproduced signal from the first main rotary head are substituted by the reproduced signal from the first subrotary head.

Description

Slow play method

1 is a pattern diagram showing the recording trajectory of a 4-frequency pilot signal.

2 is a block diagram of a circuit for generating a tracking error signal from a 4-frequency pilot signal.

3 is a block diagram showing the circuit configuration of the magnetic recording and reproducing apparatus according to the embodiment of the present invention.

4 is a detailed view of the tracking error memory circuit in FIG.

Fig. 5 is a timing chart showing signal states of respective parts in the embodiment.

* Explanation of symbols for main parts of the drawings

A _1, B ₁ : Record magnetization trajectory f ₁ , f ₄ : 4 frequency, pilot signal

20: magnetic head 21: electro-mechanical change, element

23: tracking error detection circuit 24: tracking error, memory circuit

25: level discrimination circuit 26: drive circuit

27: FG counter 34: Capstan electric motor

35: frequency generator 44: comparator

45: micro correction circuit 46: 1 frame delay circuit

48: 2-track data memory

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slow regeneration method of a magnetic recording / reproducing apparatus (hereinafter simply referred to as a VTR). The present invention relates to a variable-speed reproducible VTR that is noise-free by two or more rotating heads and an electro-mechanical conversion element for operating each head. It is related with the slow regeneration method. Conventionally, the slow playback method in the VTR of the rotating head system is, for example, in the VHS method VTR, which performs slow playback without noise by using a control signal recorded on a control track for each frame.

That is, when the head regenerates the vertical tracking portion, the capstan motor is suddenly turned on, the tape advances two tracks (one screen), and when the two tracks are detected by the control signal, the brake is applied to the capstan motor and stopped suddenly. By realizing that there is no noise on the screen, precise control such as brake control and timing control of the capstan motor is performed.

Recently, however, various methods for performing tracking control without using a control signal have been proposed. All of them superimpose and record the pilot signal for tracking control by the same head as the magnetic head used for recording the information signal to be recorded on the tape. Therefore, in the VTRs of these systems, since there is no control signal, slow playback cannot be performed as in the prior art, and a new system needs to be devised.

The present invention provides a novel slow playback method in a tracking method that does not use a control signal.

The present invention provides a method of obtaining a tracking error signal by recording a pilot signal of tracking control together with an image signal and processing the pilot signal to be reproduced, wherein the magnetic head is displaced in an orthogonal direction with respect to the tape scanning direction. An electromechanical conversion element, which moves the magnetic head by one screen in a non-contact period with the tape, and at the same time, the average value of the amount of electricity (e.g. voltage) applied to the electromechanical conversion element. Drive the tape at low speed until When the average value of the electric charges is substantially zero, the magnetic head is moved by one screen for an additional time, and the above operation is repeated to realize slow reproduction.

For the change in the tracking error signal, a pulse signal proportional to the rotational speed of the tape drive capstan is counted, and this count value is added to the tracking error using a change in the tracking error due to tape movement as a predicted value, The electro-mechanical conversion element is driven by the addition value so as to perform tracking control and at the same time when the drive exceeds a predetermined threshold value, the rotating head causes the electro-mechanical conversion element to be in contact with the magnetic tape. By shifting one screen equivalent, slow regeneration is performed by returning the driving amount to a value which does not exceed the threshold value.

The present invention is a tracking signal method that is different from the conventional method using a control signal, and is based on a novel idea that realizes a slow regeneration method, and performs precise speed control during low speed drive of an electric motor as in the conventional method. In comparison with that, it can be easily performed, and the effect of industrialization is also great.

In addition, by using a pulse proportional to the rotation speed of the capstan, the actual tape feed amount can be predicted and absorbed without accumulating errors between the predicted value and the actual value, and arbitrary slow regeneration is possible. Is big.

Before describing an embodiment of the present invention, a method of generating a tracking error signal using a pilot signal will be described.

As a method for preparing a tracking error signal using a pilot signal, various methods have been proposed, ranging from one type of pilot signal to four types, but the tracking error signal obtained in either method has the same shape. It can be applied to a method of generating various tracking error signals. Here, a four-frequency pilot signal method using four types of pilot signals will be described as an example.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail according to an accompanying drawing.

1, (A ₁ ), (B ₁ ), (A ₂ ), (B ₂ ). … Are heads (A) and (B), and are each recording track recorded on a magnetic tape. Arrow a indicates the scanning direction of the rotating head. In each recording track, each pilot signal indicated by (f ₁ to f ₄ ) together with a video signal is sequentially recorded every one feed. The pilot signal recording order is cycled in the order of (f ₁ ), (f ₂ ), (f ₃ ), and (f ₄ ), and (f ₁ ) is recorded after (f ₄ ). In each one-feed period, the pilot signal is recorded with a fixed type. The frequency of the pilot signal is set to the value shown in Table 1, for example. In Table 1, (f _H ) indicates the frequency of the horizontal synchronization signal in the video signal, and 6.5f _H indicates the frequency 6.5 times the horizontal period signal.

TABLE 1

The frequency difference between pilot signals between the recording tracks is a frequency of (f _H ) or (3f _H ), as shown in FIG. When the head scans the track (Ai) (i = 1, 2, ...), the frequency difference between the pilot signal of the scanning track and the pilot signal recorded in the adjacent adjacent track on the ground is always (f). _H ) and on the left it is always (3f _H ). When the head scans the (Bi) (i = 1, 2 ...) track, the relationship is the opposite of that described above, and the frequency difference between the scan track and the pilot signal between the right adjacent track is always (3f _H ), On the left it is always (f _H ).

Since the pilot signal is a relatively low frequency signal around 100 KHz, the pilot signal recorded in the adjacent track can be reproduced as a crosstalk signal without the head scanning the adjacent track image. For example, the pilot signal obtained when the head (A2) tracks the track on and replay is (f ₃ ), (f ₂ ), (f ₄ ) and the level is (f ₃ ) the most. Large, and (f ₂ ) and (f ₄ ) are reproduced by the same level. The head is slightly shifted from the track A ₂ toward the track B ₂ , so that the reproduction scan lower side and the level of the reproduction pilot signal obtained are smaller in the order of (f ₃ ) and (f ₄ ) (f ₂ ). On the contrary, when the head scans while shifting toward the track B ₁ , the pilot signal obtained becomes smaller in the order of (f ₃ ), (f ₂ ), (f ₄ ). Therefore, the difference signals f _H and 3f _H between the pilot signals on the main scan track and the pilot signals recorded on both adjacent tracks are separately drawn out, and the reproduction levels of the two signals are compared. The amount of shifting and the shifting direction of the head can be known.

의 전위를 끌어내고, 역의 경우는

의 전위를 끌어낸다.2 is a block diagram of a reproduction circuit for obtaining a tracking error signal. In Fig. 2, a signal obtained by combining a video signal and a pilot signal is input from the terminal 1. The circuit 2 is a low pass filter and derives only the pilot signal from the synthesized reproduction signal. The pilot signal obtained at this time is a composite signal between the main scan track and the pilot signals recorded on both adjacent tracks. The circuit 3 is a balanced modulation circuit, and multiplies the above-described synthesized pilot signal by the reference signal supplied from the terminal 4. The reference signal supplied from the terminal 4 supplies the same frequency signal as the pilot signal recorded on the main scan track. For example, in FIG. 1, when the head regenerates and scans the track A ₂ , the input signal of the balanced modulation circuit 3 is each signal of (f ₂ ), (f ₃ ), (f ₄ ). And the signal input from the terminal 4 is (f ₃ ). Therefore, the balanced modulation circuit 3 outputs the frequency signal of the sum and difference between the signals of (f ₂ ), (f ₃ ), and (f ₄ ) and the signal (f ₃ ). The circuit 5 is a tuning amplifier circuit that tunes to the signal of (f _H ), and the circuit 7 is a tuning amplifier circuit that tunes to the signal of (3f _H ). Circuits 6 and 8 are amplitude detection rectifier circuits, and circuit 9 is a level comparison circuit. Therefore, each pilot signal drawn out as a crosstalk signal from both adjacent tracks is drawn out as a difference signal from the pilot signal recorded on the main scan track, and then the signal according to the level difference is connected to the level comparison channel 9. Draw out (10). The signal obtained at the terminal 10 is according to the level difference when the reproduction level of (f _H ) is greater than the reproduction level of (3f _H ).

To draw the potential of the reverse

To draw the potential of.

Since the signal output to the terminal 10 includes information of the track shift amount and the shift direction of the head, it can be used as a tracking error signal. In practice, however, a tracking error signal suitable for practical use requires processing again.

This is because, as is apparent from the first, in the (Ai) track and the (bI) track, the relationship between the shifting direction of the head and the multiplication output f _H or 3f _H O obtained at that time is inversely related to each other. For this reason, the analog inverting circuit 11 and the switch 12 are used to analytically invert the signal of the terminal 10 when the head scans the (Ai) track and the (Bi) track. You can do it. That is, the terminal (! 4) is connected to the terminal 10 during the (Ai) track scan through the switch 12 and to the output of the analog inverting circuit 11 during the (Bi) track scan. do.

의 전위가 좌측으로 어긋나 있을 경우는 항상

의 전위가 나타난다. 따라서 단자(14)에 얻어지는 트랙킹오차 신호를 사용하여, 캡스턴 전동기나 자기헤드의 변위량을 제어해주면, 헤드를 항상 주주사트랙상을 온트랙해서 주사할 수 있다.In this way, the output signal of the terminal 14 is always shifted to the right from the track to be scanned regardless of the tracks (Ai) and (Bi).

If the potential of is shifted to the left, always

The potential of appears. Therefore, if the displacement amount of the capstan electric motor or the magnetic head is controlled by using the tracking error signal obtained at the terminal 14, the head can always be on-track and scanned on the main scanning track.

The above description is an outline of a method of obtaining a tracking error signal using four types of pilot signals.

The present invention provides a novel slow regeneration method by attaching a magnetic head onto an electro-mechanical conversion element and controlling the electro-mechanical conversion element by a signal obtained by performing the signal processing described below for the tracking error signal. To provide. Hereinafter, embodiments of the present invention will be described in detail.

3 is a circuit block diagram showing an outline of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, wherein a reproduction signal from the magnetic head 20 is amplified by the RF signal processing circuit 22 and then tracked. The error detection circuit 23 outputs a tracking error signal. This tracking error signal is accumulated in the tracking error memory circuit 24. The output of the tracking error memory circuit 24 adds the output of the steel pattern preparation circuit 28 to the driving circuit 26 to drive the electro-mechanical conversion element 21 and displaces the magnetic head 20. Gives. The output value of the tracking error memory circuit 24 is input to the level discrimination circuit 25. In the level discriminating circuit 25, it is judged whether or not to move the magnetic head 20 in the non-contact period based on the input signal level. That is, when two tracks are moved, the change signal is output from the level discrimination circuit 25 to the reference signal generation circuit 29 and the tracking error memory circuit 24, respectively. The capstan electric motor 34 is controlled by the frequency generator (FG) 35, the capstan servo circuit 33, and the capstan drive circuit 32 except during slow regeneration. The output pulse is input to the FG counter 27 and the output value of the counter is input to the tracking error memory circuit 24. Numeral 30 denotes a head switch signal input terminal 31 and a switch circuit for switching a signal applied to the capstan driving circuit 32 when a slow command is given.

4 is a detailed diagram of the tracking error memory circuit 24, and this operation will be described.

The tracking error signal input from the terminal 40 is compared by the comparator 44 with the output value of the one-frame delay circuit 46. By the output of the comparator 45, the output value of the one-frame delay circuit 46 is minutely corrected ( ⁺¹ / -1) and input again to one frame 46. The output value of the FG counter 27 is input from the terminal 41 and input to the one-frame delay circuit 46. When the command from the level discrimination circuit 25 is input from the terminal 42, the switch 47 is turned on for one frame period, and the tracking error amount corresponding to two tracks is transmitted to the one frame delay circuit 46. Enter it. The terminal 43 is an output of the tracking error memory circuit 24 and is input to the driving circuit 26 and the level discriminating circuit 25.

5 is a timing diagram showing the operation principle of the embodiment, and shows the waveforms of the respective parts shown in FIGS. That is, in FIG. 5, (HSW) is a head switch signal, which is a signal synchronized with the frame frequency of the video signal. At the timing a, since the head drive amount in the previous frame was negative, the head was moved two tracks by an instruction from the level discrimination circuit 25, and the head was subjected to the track error detection reference signal. Change to the same signal as the track being scanned. In each frame, the number of FG pulses counted in the previous frame is added to the tracking error. This addition predicts the variation in tracking error during slow playback. In other words, the predicted value predicts a change in tracking error that cannot be followed by only a minute correction by comparing the delayed value of one frame with the current tracking error. For example, if the amount of minute correction is 1/10 of the tracking width, if the prediction is not used, if the tape speed progresses 1/10 track width to 1 feed, that is, slow playback is faster than 1/10 slow playback, Can't track The error between the predicted value and the actual tracking error is absorbed by the minute correction unit 45. This prediction value is updated every frame, and no error is accumulated because the previous prediction value is not used. Since the iso of the tape by the electric motor 34 cannot take an extremely small value as compared to the frame period, this predicted value does not generate a large error even with a time delay of one frame.

However, if the tape is driven at a slow speed after moving the head two tracks at time a, the tracking error amount and the head drive amount decrease with tape movement, and at timing b, the head drive amount is negative (level discrimination circuit). It becomes (about the threshold sound in (25)). When the head drive amount is added, at the timing C of the next frame, the head drive amount of 2 tracks is added again, and the reference signal is changed by 2 tracks, similarly to the timing a. By repeating this method, the head can always track on the track, so that a slow noise can be realized.

In the above description, the case where the number of FG pulses can be directly input to the one-frame delay circuit 46 is shown. However, the numerical values of the number of FG pulses, the steel pattern creation circuit 28, and the two-track data memory 48 are different. If it cannot cope with one-to-one, the number of FG pulses may be multiplied by a constant coefficient. This counter is fixed and easy to multiply because the number of FG pulses per track does not change.

In addition, the embodiment of the present invention can perform the same processing by software using a microprocessor in addition to the embodiments described herein, and the examples are not limited to those described above.

Claims (3)

A group of discontinuous recording tracks inclined on a magnetic tape using the rotating head 20. The pilot signal is superimposed on the information signal and the information signal, and recorded on the above-described recording track for the recording track to be reproduced during reproduction. In the magnetic recording and reproducing apparatus of the method for obtaining the tracking error signal by the level difference of the reproduced crosstalk signal of the reproduced signal, the mechanical track of the rotating head 20 is moved by the electro-mechanical conversion element 21 to the recording track. A displacement amount corresponding to one screen is given to the electromechanical conversion element 21 and the head 20, and a tape feed is started at a low speed, 21. The slow regeneration method according to claim 1, wherein the tape transfer is stopped when the average value of the amount of electricity applied to 21) becomes almost zero. The slow regeneration method according to claim 1, wherein after the tape transfer stops, the operation of claim 1 is repeated by giving the head (20) an amount of displacement equivalent to one screen. A pulse signal proportional to the number of revolutions of the magnetic tape driving cap stub 34 is counted, and the count value is added to the tracking error signal, and the added signal is added to the tracking error signal. If the drive amount exceeds the preset threshold value while driving the mechanical conversion element 21, the electro-mechanical conversion element 21 corresponds to one screen in the non-contact period between the rotating head 20 and the tape. Slow regeneration method characterized in that the minute displacement.

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