JPS60185245A - Driving method of noise at still reproducing - Google Patents

Abstract

PURPOSE:To drive the noise of a reproduced picture into both sides of a picture plane by transferring intermittently a magnetic tape until the center of a tracking error voltage obtained by processing a pilot signal enters into a set voltage range. CONSTITUTION:A tracking error signal is generated in accordance with the level difference of pilot signals reproduced as crosstalks from recording tracks adjacent to the front and back of a recording track to be reproduced and supplied to a terminal 31. A head switching signal H-SW synchronized with the rotational phase of a cylinder is inputted to a terminal 28 and a sampling pulse generated with a prescribed time delay by monostable multivibrator 29, 20 holds the tracking error signal. The holding voltage is detected by an absolute value detecting circuit 33 and a comparator 34 operates a pulse feeding circuit 36 until the holding voltage enters into the previously set up voltage range to transfer the magnetic tape intermittently. Thus, the noise can be driven into both the sides of the picture plane.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording/reproducing apparatus (hereinafter referred to as VTR), particularly a method for suppressing noise during still reproduction in a VTR that performs tracking control using a four-frequency pilot signal. It is related to.

Conventional configuration and its problems Conventionally, the method of realizing noise tracking method methylation in a VTR is to detect the presence or absence of an RF multiplied signal after reproducing the video signal.This method is explained in Figure 1. In addition, a rotating two-head type helical power scan type VT
The magnetization trajectory recorded in R is shown. In FIG. 1, 1 is a magnetic tape, and arrow 2 indicates the direction of transport of the magnetic tape. Ai・B・・人2・B2Pa.

is a recording track recorded by the human head and the B head, and arrow 3 indicates the scanning direction of the heads. The scanning trajectory of the head 4q is the trajectory when the magnetic tape is transferred at a normal speed, and the trajectory 5 is the trajectory when the transfer of the magnetic tape is stopped.The output waveform of the reproduced RF signal Kjg at this still time is , recording track width Hw1 and recording trunk position i
6 and the scanning locus of the head.

Figure 2 c and d show the positional relationship between the head trajectory and the recording track when TW: Hw, and Figure e shows the positional relationship between the head trajectory and the recording track when TW: Hw.
The above positional relationship when w is shown. In FIG. 2, B, , A2. B2 indicates the arrangement and track;
The trajectory indicated by the dashed line indicates the scanning trajectory of the head during still shooting. The azomass angle of the heads used during normal playback is t+f in the A and B heads, and heads with azimuth angles in opposite directions are used, but the heads used during still I11 playback have azimuth angles in the same direction to realize field methyl. Use a head with If the azimuth angle of the head used in the VC is equal to that of the A head, then the re-41RF obtained from the still locus shown in No. 21.
(, -i- The output of the switch 4 is proportional to the length of the diagonally shaded portion in the track width direction shown in FIG. 2.

FIG. 3 shows reproduced RF signals under various conditions. Third
In the figure, a is a head switching signal, and b is a reproduction RF during normal reproduction.

Each endogenous RF transformation 'fl-J shown as c, d, and e in Fig. 3 is
This is a regenerated RF transmission under conditions T'T shown in c, d, and e of FIG. In the reproduced image, the level of the reproduced RF signal is slightly reduced from the level during normal reproduction (even though it is possible to distinguish between the image and l~, there is noise below 4.ρ and 71). It becomes an image and it is impossible to identify the contents.ii■+
7. Limits on the level of the reproduced RF iris that can be identified as a j image.
<The value is the RF signal level I during normal playback.
Assume A. In this case, the reproduced RF signal shown in FIG. 3C results in noise on both sides. -4, the noise position is l'1lii in the image cow RF information shown in the third [me1d]
Since it is located in the 17110 ryo 1 rule, a reproduced image that is kl and better than the image in figure 0 can be obtained. A decrease in the level of the reproduced RF signal is not detected as a dropout within the video signal processing circuitry. Therefore, in the conventional noise tracking method, METEL was aiming for a dropout method (a method in which A7 and A4 are driven into the changing part of the head switching signal, that is, on both sides of the art dealer).

To reduce the noise part of the image/ζ, use 111-7
IRF (It is best to suppress the level reduction of No. 8 as much as possible.

To achieve this, the width of the head 1 is made larger than the width of the recording trunk, and the reproduced RF signal shown in Fig. 3e is reproduced. 4↑ is good. However, in the second edition of Regenerative RF I shown in Figure e, it is difficult to divide the maximum value and the decrease value of the signal level by 11 because ≠11.

In other words, the conventional noise tracking method using the Machito RF signal suppresses the decrease in the output level of the reproduced RF signal.
Head width and description &? ) VTR with rack width no set
There were some drawbacks that made it difficult to apply in the VC episode.

OBJECTS OF THE INVENTION The purpose of the present invention is to reproduce video signals and reproduce still images using a noise tracking method without using RF i1-1.
The purpose of the present invention is to provide a new method for IjV.

According to the present invention, a pilot signal for tracking control is recorded together with a video signal, and the pilot signal to be reproduced is processed by a 7 for tracking control. I was obtained, and this l-racking error signal was sampled and held using a pulse No. 4M synchronized with the head switching signal (H-SW double signal, and the hole obtained)? This is a method of eliminating noise by using 4-t ti'.

Description of a Practical Guessing Example Before a detailed description of the present invention, a tracking method using four types of pilot signals will be described.

FIG. 4 shows a recorded magnetization trajectory by the four-frequency pilot signal tracking method, and FIG. 6 is a block diagram of a reproducing circuit for obtaining a tracking error signal.

In Fig. 5, A,,B,,A,,,B2...
d: Each recording (rack) is recorded on a magnetic tape by A head and B head having different predetermined azimuth angles.

Arrow 6 indicates that the scanning direction of the rotary head is set to 3, and the C1-1 video signal along with the C1-1 video signal to the valley track is set to 1. The order shown in Figure 4 is as shown in Figure 4, and between 1 file M l!, and Ii, type 1) top pylon l.
-48 is continuously turned L1'' green.The frequency of the pilot signal is set to the value shown in Table 1, for example.

Table 1 In Table 1, fH indicates the frequency of the horizontal synchronization signal, and 6.5fH indicates a frequency that is 6.5 times the frequency of the horizontal synchronization signal.

The frequency difference of the pilot signal between each recording track is the fourth
As shown in the figure, it indicates a frequency of f□ or 3fH.

The frequency difference of the pilot signal between each recording track is the fourth
As shown in the figure, the frequency is fH or 3fH. When the head scans Ai (i=1.2...) tracks, the frequency difference between the pilot signal of the scanning track and the pilot signal recorded on the adjacent track on the right side on the paper is always fH, and that on the left is always 3 fH. When the head scans the Bi track, the relationship is inverse to that described above, and the frequency difference in the pilot frequency between the scanning track and the adjacent track on the right is always 3 fH, and that on the left is always fH.

Since the pilot signal is a relatively low frequency signal around 100 KHz, the pilot signal recorded on the adjacent track can be reproduced as a crosstalk signal without the head scanning the adjacent track.

For example, the pilot signal obtained when the head on-tracks and scans the A2 head is f3° f2. f
It is a composite signal of 4, and its level is the strongest at f3,
Next f2. f4 is played back for times - levels.

When the head slightly deviates from trunk A2 toward track B and performs reproduction scanning, the level of the obtained square pilot signal is f3. f4. It becomes smaller in the order of f2.

Conversely, the level of the pilot signal obtained when the head shifts and scans above trunk A2 is f3. It decreases in the order of f2° f4. Therefore, by separating and extracting the difference frequency signals fH and s fH between the pilot signal on the main scanning trunk and each pilot signal recorded on both adjacent tracks, and comparing the reproduction levels of both signals, the main scanning track It is possible to know the amount and direction of head deviation from the position.

FIG. 6 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In FIG. 5, an RF multiplied signal in which a video signal and Pyro No. 7848 are combined is input from terminal 7. Circuit 8 is a low-pass filter, and reproduces RF
Separate and extract only the pilot signal from the signal. The pilot signal obtained at this time is a composite signal of the main scanning trunk and the pilot signals recorded on both adjacent tracks.

The circuit 9 is a balanced modulation circuit and multiplies the above-mentioned composite signal by the reference signal supplied from the terminal 10. terminal 1o
The reference signal supplied from the main scanning track is a pilot signal having the same frequency as the pilot signal recorded on the main scanning track. For example, in FIG. 4, when the head is reproducing scanned over the trunk A2, the input signal to the balanced modulation circuit 9 is f2° f3114, which is the reference signal f3 supplied from the terminal 10. Therefore, the output signal of the balanced modulation circuit 9 is a frequency sum and difference signal between each signal of f2 ``3'' 4 and the signal of f4.

The circuit 11 is a tuned amplifier circuit tuned to an fH signal, and the circuit 12 is a tuned amplifier circuit of fH. circuit 13
．． 14 is a detection rectifier circuit, and circuit 15 is a level comparison circuit.

Therefore, each pilot signal taken out as a crosstalk signal from both adjacent tracks is separated and output as a difference signal from the pilot signal recorded on the main scanning track, and then sent to the level comparison circuit 15. A signal corresponding to the level difference is extracted. The reproduction level of the signal fH obtained by the level comparison circuit 15 is 3fH.
When the reproduction level is higher than the reproduction level, a positive voltage corresponding to the level difference is extracted, and in the opposite case, a negative potential is extracted. Note that the signal obtained by the level comparison circuit 15 includes information on the amount and direction of track deviation of the head, and therefore can be used as a tracking error signal. However, the tracking error signal suitable for practical use requires further processing.

This is because, as is clear from Fig. 1, the relationship between the direction of head deviation and the crosstalk signal (fB or 5fH) obtained at that time is opposite to that of track A and track B. It's a good thing.

In FIG. 5, circuit 16 is an analog inversion circuit, and circuit 17 is a switch circuit that is switched by a head switching signal supplied from terminal 18.

Therefore, for example, when the head reproduces and scans the A track, the output of the level comparison circuit 15 is output as is, and when the head reproduces and scans the B trunk, the output signal of the level comparison circuit 15 is output in analog form to the terminal 19. It is inverted and output.

Therefore, the signal obtained at the terminal 19 is always a positive potential when the head deviates to the right from the track to be scanned, and a negative potential is always output when the head deviates to the left, regardless of the A or B track.

Therefore, if the unobtainable signal is supplied to the terminal 19 as a dragging error signal to control the tape feeding speed, the head will always scan on the main scanning track.

The above is an outline of the method for obtaining the l-racking error signal using four types of pilot signals.

The present invention is a method for tracking noise during still reproduction in a tracking method configuration as shown in FIG. 5, for example.

The present invention will be explained in detail below.

FIG. 6 shows the recording track and the scanning locus of the head center during still operation. In the figure, B1. ,
A2. B2... is for each track, f21f
4. f3... indicates the frequency of the pilot signal recorded on each recording trunk. Arrow 21 indicates the scanning direction of the head, and arrow 22 indicates the tape transport direction. The trajectories 23 to 27 are the trajectories of the head center in various still states relative to the recording trunk.

FIG. 7 shows waveforms showing tracking error signal voltage changes in the various still states shown in FIG.

In Fig. 7, the signal indicated by a is a 1-3W signal, and during the Hl period, the A head is in contact with the tape, and during the Low period, the B' head, which has the same azimuth angle as the A head, is in contact with the tape and reproduced. This is the period during which

The sawtooth wave shown in b is a tracking error signal output to the terminal 2Q shown in FIG. 5 when the center of the head scans the methyl locus 24 shown in FIG. In addition, in the still mode, the reference signal inputted from the terminal 10 shown in FIG. 6 always has a constant frequency, and is, for example, a signal of f4.

When the head scans the methyl locus 24, at the point where the head starts to come into contact with the tape, the crosstalk signal of the pilot signal f3 recorded on track B2 is
larger than the pilot signal recorded on track B1. In other words, in terms of the difference signal from the reference signal f4, fH
is higher than the reproduction level of 3 fH. When the head scans the center of the track, fH and 3
The reproduction levels of fH are equal, and the reproduction level of 3fH is higher than the reproduction level of r)I at the point where the head leaves the tape. Therefore, when the still trajectory is the trajectory shown by 24,
The tracking error signal obtained at the terminal 20 has a sawtooth waveform as shown in FIG. The same applies when the head is B'.

In Figure 7, the voltage is V. is the voltage value when the crosstalk signal levels of the pilot signals reproduced from both adjacent tracks are equal.

Using the same concept as above, if we show the tracking error signal obtained at terminal 2Q when the head scans methyl loci 23 to 26 shown in FIG. 6, if the still locus is 23, then C.
1 still locus 24, d1 still locus 25, a sawtooth wave as shown in e.

When the head scans the methyl locus 27 shown in Fig. 6, f
becomes. The tin-shaped wave of the tracking error signal obtained at this time has an upward-sloping waveform, which is opposite to that when the methyl locus 24 is scanned.

This is because, in Fig. 6, the head is recording L/Rack A.
Even when scanning three soils, the reference signal input to the balanced modulation circuit 9 must be f4, so the f of the output signal of the balanced modulation circuit 9 must be f4.
This is because the H acid component reaches its maximum level at the point where the head separates from the tape.

In the above, the still trajectories where the reproduced video signal level is maximum at the center of the head switching signal and no noise occurs on the screen are 24 and 2T, and the head scans still trajectories other than 24 and 2T. At times, it is necessary to feed the magnetic tape until the noise is pushed to either side of the screen.

An embodiment of the present invention in which the magnetic tape is intermittently fed to the extent that the noise during stills is pushed to both ends of the screen is shown in FIG. 8 and will be described.

To explain the configuration without switching, H-8 is connected via terminal 28.
W signal is triggered by rising or falling, H, S
The signal is input to the monostable monomulti 29 which is set to be delayed by the A time width To of the W-fold signal Hl or Low period. The output of the monostable monomulti 29 is a monostable monomulti 3 that generates a short pulse at the rising or falling edge.
This short pulse output is input to the sample hold circuit 3 as a pulse for sampling the tracking error signal shown in FIG. 7 which is input from the terminal 31.
2 and holds the tracking error signal.

The output of this sample hold circuit 32 is input to an absolute value detection circuit 33 having the characteristics shown in FIG. The output of this absolute value detection circuit 33 is at output level V.

slightly higher level v? It is input to a level comparison circuit 34 which obtains a Hi output if it is equal to or higher than L, and a Low output if it is lower.

The output of this level comparison circuit 34 is H, SW multiplied signal,
Whether or not the intermittent feed pulse output of the monostable multi 36 that generates pulses for intermittently sending the motor is input to the pulse sending circuit 36, and the intermittent feeding noculus is output from the output terminal 37 of the pulse sending circuit 36. control. The output of this terminal 3γ is sent to a capstan motor drive circuit, and the motor is intermittently sent to transport the magnetic tape only when a Norculus output is being obtained.

Here, the configuration is such that a missing feed pulse can be obtained from the terminal 3 only during the period when the output of the level comparison circuit 34 is Hi.

The operating principle of the embodiment of the present invention whose configuration has been described above will be explained using FIGS. 6 to 9.

As mentioned above, the reproduced video signal level reaches its maximum in the middle-heat section of the H and SW double signals, and the trajectories where no noise occurs on the screen are 24 and 2 ends.

Now, the tracking error signal when scanning the methyl trajectory of 024 is explained to explain the noise chasing operation from the state when scanning the methyl trajectory of 024 to the state of scanning the still trajectory of 27 by performing frame advance. ,b shown in FIG.
The waveform of this signal is T from the rising (or falling) position of the H-3W signal. Sample and hold circuit 32 that samples and holds at a time-delayed position
The voltage of is V. This hold voltage υ. is input to the level comparison circuit 34 via the absolute value detection circuit 33,
Levels are compared. Output level 7 of absolute value detection circuit 33
of. Is the comparison level of the level comparison circuit 34 set in advance? Since it is lower than 7a, the output of the level comparison circuit 34 is Low, and no intermittent transmission signal is output to the terminal 37.

Therefore, the capstan motor is stopped because it is not intermittently fed.

If frame-by-frame advance is performed and the tape is transferred from this state, for example, if 25 methyl loci shown in FIG. 6 are scanned, the tracking error signal will have the waveform d shown in FIG. 7.

This waveform d is sampled and held by the sample and hold circuit 32 in the same manner as described above to obtain a hold voltage Z)2. 2 digit absolute value detection circuit 3 of this hold voltage 7
3 to the level comparison circuit 34, where it is compared with v level. Since the v2 voltage becomes higher than υyu, the output of the level comparison circuit 34 becomes 'H1, and the intermittent feed pulse created by the monostable monomulti 35 is output from the terminal 37.
Starts to drive the capstan motor intermittently.

Next, even if 26 still trajectories shown in FIG. 6 are scanned, the hold voltage obtained from the sample and hold circuit 32 is v
3, which is higher than the comparison level of the level comparison circuit 34, and the output of the level comparison circuit 34 remains in the Hi state, and the intermittent feed pulse continues to be sent from the terminal 37.

Further, the hold voltage obtained from the sample hold circuit 32 when the tape is transported and scans the methyl locus shown in FIG.
At the moment when the output QL of the level comparison circuit 34 becomes lower than 4.
The state becomes OW, and the intermittent feed pulse output from the terminal 37 is stopped.

Therefore, if frame advance is performed from the time when the methyl locus 24 shown in FIG. When this happens, tape transport is stopped.

When frame advance is performed from the methyl locus 27, the output of the sample hold circuit 32 is υ. Although it is lower than the voltage, the absolute value detection circuit 33 is set to V. If the configuration is configured so that the differential voltage can be detected based on , then an intermittent feed pulse can be output from the terminal 37 in the same way as described above, and a still locus without noise can be scanned on the screen.

Effects of the Invention As explained above, in the present invention, the pilot signal for tracking is processed and the obtained tracking error voltage is used to set the center of the tracking error voltage to H.
- By intermittently transporting the magnetic tape from the rising or falling edge of the 3W signal until it reaches a predetermined position,
It is possible to provide a still method that allows noise in a reproduced image to be pushed to both sides of the screen.

Further, according to the present invention, compared to a method using an RF multiplied signal obtained by reproducing a video signal, it is possible to obtain a stable methyl image even when using a head having a wider head width than the recording track width. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the relationship between the recording magnetization trajectory and the head scanning trajectory, and FIG. 2 is a schematic diagram showing the relationship between the head width and recording trunk width and the head scanning trajectory for each methyl state.
Figure 3 shows the reproduction R of the unimaged original signal in normal and methyl mode.
A waveform diagram showing the F output, Figure 4 is a schematic diagram showing the recorded magnetization locus using the 4-frequency pilot signal method, Figure 5 is a circuit block diagram for obtaining a tracking error signal, and Figure 6 is a diagram showing each recording track. A schematic diagram showing a still locus, Fig. 7 is a tracking error signal waveform diagram when scanning the methyl locus in Fig. 6, Fig. 8 is a circuit diagram showing an embodiment of the present invention, and Fig. 9 is an absolute value detection FIG. 3 is an output waveform diagram of the circuit. 1...Magnetic tape, 5...Still trajectory, A,,B. ...Recording track, 'rw,,,,, Track width -% HW"""Head width, f1 to f4...
...Pilot signal, 8...Low pass filter,
9...Balanced modulation circuit, 11゜12...
Tuned amplifier circuit, 13.14...Detection rectifier circuit,
15... Level comparison circuit, 16... Inverting circuit, 29, 30, 35... Monostable monomulti,
32...Sample hold circuit, 33...
. . . Absolute value detection circuit, 34 . . . Level comparison circuit, 36 . . . 9 pulse sending circuits. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 e [de f Figure 4 Figure 6 Figure 7

Claims (1)

[Claims] A pilot signal for tracking control is superimposed on a video signal to be recorded and sequentially recorded on a magnetic recording medium as an adjacent recording trunk, and when in use, the tracking control pilot signal is superimposed on a video signal to be recorded and recorded sequentially on a magnetic recording medium. When performing relative position control between the recorded M + - rank and the angular raw magnetism using the tracking error signal corresponding to the level difference of the pilot signal reproduced as a cross-storage, the cylinder A sumplinder pulse is generated at a predetermined position from a head switch notching signal synchronized with the rotational phase of , and the I racking error signal is sampled by this summing pulse to obtain hold electrons, and this hold voltage is a preset voltage. A method for suppressing noise during still playback, characterized by generating a tape feed pulse that moves the magnetic tape until it falls within the range.