JPS611181A - Still picture reproducing method of magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To stop stably a tape by using two heads used at field still picture reproduction to detect an optimum stop position of the tape and to prevent tape stop while a head output produced due to the difference in head touch is small. CONSTITUTION:A head switching signal (a) is inputted from a terminal 46 of the still picture reproducing system, monostable multivibrators 47, 48 are triggered, outputs (b), (c) from the rising/falling of the signal outputted from the multivibrators 47, 48 are synthesized by a synthesis circuit 49 and synthesized outputs (d), (e) are obtained. The outputs (d), (e) are differentiated by a differentiation circuit 50 to output a pulse output (e) of a short time width. Further, a tracking error signal from a level comparator circuit given to a terminal 11 is fed to an on-track pulse generating circuit 51, and when an error signal passes through a zero reference, a pulse output (f) is outputted, a gate pulse (g) is fed from a monostable multivibrator 52 and inputted to a pulse generating circuit 53. Then the generation of the feed pulse is controlled by a pulse output (e) to stop the tape on an optimum position.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to still image reproduction in which a tape is stopped and reproduced in a magnetic recording/reproducing device (hereinafter referred to as a VTR), and in particular, tracking control using a pilot signal. The present invention relates to a method for reproducing still images after transmitting noise in a VTR.

The configuration of the conventional example and its problems Before explaining the conventional example, a method for creating a tracking error signal using a pilot signal will be described. Here, a four-frequency pilot signal method using four types of pilot signals will be explained as an example.

FIG. 1 shows the recorded magnetization trajectory by the four-frequency pilot signal method. In Figure 1, A□HB, A 21 B 2
H... is each recording track recorded on the magnetic tape by the A head and the B head. Arrow (1a) indicates the scanning direction of the rotary head, and arrow (1b) indicates the tape running direction. In each recording track, pilot signals indicated by f1 to f4 are sequentially recorded for each field together with the video signal. The order in which the pilot signals are recorded is as shown in FIG. 1, and one type of pilot signal is continuously recorded within one field period. The frequency of the pilot signal is set, for example, to the value shown below.

f1=102.5 (KHz: 6.5fHf2=11
8.9(K7)≠7.5fHf, =165.2(KH
z) #10.5f+4f4= 148.7 (K kite) Cape 9.5f,.

Note that fH indicates the frequency of the horizontal synchronization signal, and is 6.5fH.
indicates that the frequency is 6.5 times the frequency of the horizontal synchronization signal, and as shown in Figure 1, the frequency difference in the pilot signal between adjacent recording trunks is fH or 3f. . Then, the head is A, (however, j
, = 1 r 2 r 3 +...) When scanning a track, the frequency difference between the pilot signal of the scanning trunk and the pilot signal recorded in the adjacent track on the right on the paper is always f++, and that on the left is always 3
It is f+4. The head is B+ (however, i=1.2, 3.
...) When scanning a track, the relationship is reversed to that described above, and the frequency difference between the pilot signals between the scanned track and the adjacent track on the right is always 3fH, and that on the left is always fH.
. It is.

Here, 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 even if the head does not scan the adjacent track. I can do it. For example, the pilot signal obtained when the head on-tracks the A2 track and performs reproduction scanning is f3. f2.
It is a composite signal of f4, and its level is the highest at f3, and the same level as f2+f4 is reproduced first.

The level of the reproduction pilot signal obtained when the head slightly shifts from track A2 to the track B□ side and performs reproduction scanning is f, , f2 . It becomes smaller in the order of f4. Therefore, the difference signals f□ and 3f between the pilot signal on the main scanning track and each pilot signal recorded on both adjacent tracks
9. By separating and extracting the two signals and comparing the reproduction levels of both signals, it is possible to know the amount of deviation of the head from the main scanning track and the direction of the deviation.

FIG. 2 is a block diagram of a regeneration circuit for obtaining an l-racking error signal. In Fig. 2, from terminal (2) there is a reproduced RF signal in which the video signal and pilot signal are combined.
A signal is input. (3) is a low-pass filter that separates and extracts only the pilot signal from the reproduced RF signal.

The pilot signal obtained at this time is a composite signal of the main scanning track and the pilot signals recorded on both adjacent tracks. (4) is a balanced modulation circuit which multiplies the aforementioned composite signal by the reference signal supplied from terminal (5).

The reference signal supplied from the terminal (5) is a pilot signal having the same frequency as the pilot signal recorded on the main scanning track. For example, in FIG. 1, when the head performs reproduction scanning over racks 1 to A2, the input signal to the balanced modulation circuit (4) is f21f31f4, and the terminal (
The reference signal supplied from 5) is f3. Therefore, the output signal to the balanced modulation circuit (4) is f2. f3. Sum and difference signals between each signal of f4 and the signal of f4 are output. (
6) is f. A tuned amplifier circuit tuned to the signal of (7) is 3
A tuning amplifier circuit tuned to the fH signal, (8) and (9) a detection rectifier circuit, and (10) a level comparison circuit. Therefore, each pilot signal taken out as a gross talk signal from both adjacent tracks is separated and taken out as a difference signal from the pilot signal recorded on the main scanning track, and then sent to the level comparison circuit (10). A signal corresponding to the level difference is taken out to a terminal (11). The signal obtained at the terminal (11) has a playback level of fi+ of 3.
When it is higher than the reproduction level of fH, a positive potential corresponding to the level difference is extracted, and in the opposite case, a negative potential is extracted. The signal output to the terminal (1j) can be used as a tracking error signal because it includes information on the amount and direction of the head's track deviation. However, a tracking error signal that is actually suitable for practical use requires further processing. This is because, as is clear from FIG. 1, the direction of the head deviation and the beat signal (fH or 3f1.
) are opposite to each other. Therefore, in FIG. 2, the configuration is as follows. (12) is an analog inversion circuit, and (13) is an electronic switch that is switched according to the level of the head switching signal supplied from the terminal (14). Therefore, the terminal (15) has, for example, A
When the head scans a track, the signal obtained at the terminal (11) is sent as is, and when the head scans the B track for reproduction, the signal obtained at the terminal (11) is inverted in analog form and sent as a signal. Therefore, the signal obtained at the terminal (15) should be scanned by the head regardless of tracks A or B. When the head deviates to the right from the track, a positive potential is always output, and when it deviates to the left, a negative potential is always output. be done.

Therefore, if the tracking error signal obtained at the terminal (15) is supplied as a phase error signal to the capstan motor, for example, and the tape feeding speed is controlled, the head always scans on the main scanning track in an on-1 rack. It turns out.

The above is an overview of the method for obtaining a tracking error signal using four types of pilot signals.

Next, a conventional method for processing the signal obtained at the terminal (11) in FIG. 2 described above to send out noise and reproduce a still image will be described. Note that field playback without image blur has recently become common as still image playback, so the explanation will be based on field still image playback.

In the above-mentioned tracking method, reference pilot signals fl, f2. f3. When f4 is fixed to a single value, the output signal of the comparator circuit (lO) will be as shown in Figure 3, if the zero reference is when the levels of the crosstalk signals f and 3f□ match. Make a change. Here, if the head used during still image playback is, for example, A azimuth, the scanning locus of the rotary navel 1 in the on-track state during field still image playback will be the solid line arrow (21) or the broken line arrow (21) in Fig. 4. 22). f input to terminal (5) in Figure 2 during still image playback
If one of the reference pilot signals 1 to 1 with different frequencies of □l f21 f31 f4 is successively extracted, for example, if the reference pilot signal of f□ is selected, then the signal shown in FIG. The output of the comparator circuit (10) shown in FIG. 2 when continuous scanning is performed is shown in FIG. 5 when expressed in correspondence with the head switching signal. Figure 5 (a) shows the head switching signal.
(B) is the output of the comparator circuit (10) when the head trajectory (21) is shown in Figure 4, and (c) is the head trajectory (22) in Figure 4.
This is the output of the comparison circuit (]0) when .

Conventionally, the output of the level comparison circuit (10) shown in FIG. 2 is used to generate gate pulses to send noise and reproduce still images. Further, this will be specifically explained using the block diagram of the conventional example shown in FIG. 6 and the operational waveform diagram shown in FIG.

In Fig. 6, the head switching signal (d) is input from the terminal (31), and the head switching signal (d) is inputted from the terminal (31).
As the output of the monostable multivibrator (32), which is triggered by the rising or falling edge of The pulse output signal (E) is input to the differentiating circuit (33), and as its output, a pulse output signal (E) with a relatively short time width is obtained.On the other hand, the terminal (11) is connected to the terminal (11) shown in FIG. The tracking error signal output from the level comparison circuit (10) shown in FIG. The above pulse output (
) is a monostable multi/
<Input to the ibrator (35) to obtain a gate pulse (chi) with a constant time width in the positive direction. The gate no. Gate pulse obtained from monostable multivibrator (35)
When the pulse width is at a location other than the pulse width of (h), a feed pulse (su) of a constant time width synchronized with the above positive differential pulse is generated, and the above positive differential pulse causes the monostable multivibrator (
35), the above-mentioned sending pulse (su) is prohibited when the width is within the width of the gate pulse (ch) obtained from (35).

Therefore, if the delay amounts of the monostable multivibrators (32) and (35) are appropriately set based on the optimal tracking signals (signals (b) and (c) in FIG. 5) that inhibit the sending pulse, When the mode of the tape is changed from the normal playback state to the still image playback state, if the capstan motor is driven by the signal from the above-mentioned feed pulse generation circuit (36), the tape will be stopped at the optimal position after noise feed. be able to.

Next, problems with this conventional example will be described.

If the tape slightly floats at the head of the cylinder during a mode transition from reverse fast-forward playback to still image playback, etc., noise feed is performed as described above, but in this conventional example, noise feed is performed only during the period when the head switching signal is at the "H" level. Since the tape stop position is not detected, differences in head ejection volume,
Due to the difference per head, even when the other head, that is, the head switching signal is at the rtLu level and the head output is small, the head switching signal is t.
If the stop position is detected during the LHI+ level period, the above-mentioned feed pulse is inhibited and the tape stops.

In this case, when viewed as a screen, the output from one side of the head is small, resulting in a noisy screen.

This problem is particularly likely to occur when a cylinder with three heads mounted on one cylinder is used for field still image reproduction, and the mounting positions of the cylinder heads are as shown in FIG. The A head (41) and B head (42) are heads used for normal recording and reproduction, and when field still image reproduction is performed, the A head (41) and A' head (43) having the same azimuth are used. In this case, the B head (42) and the A' head (43) are generally formed on the same hard base, and the B head (
42), since the spacing between the A' heads (43) is narrow, when the cylinder rotates in the direction of the arrow (I) in the figure, the A' head (43) on the rear side
'The bed touch of the head (43) is worse than that of the other heads.

In this case, if the tape stop position for still image playback is detected using the A head (41) with good head touch,
'During the reproduction period with the head (43), the output of the reproduction head becomes small due to the head touch, and there is a high possibility that the reproduction screen will be noisy as described above.

Purpose of the Invention This invention aims to reproduce still images in a VTR that performs tracking control using the Pyrower 1 signal, with both reproduction outputs of two heads being stable. Still image playback that can prevent the tape from stopping when the output of one head is low when playing still images by sending out noise from a state where the tape is slightly floating when transitioning to a mode such as still image playback. The purpose is to provide a method.

Structure of the Invention The still image reproducing method of the present invention includes the following steps: 1. A pilot signal for tracking control is input together with a video signal. A tracking error signal is obtained by processing the pilot signal recorded on a magnetic tape as a group of inclined discontinuous recording tracks and reproduced, and controlling the relative position between the recording track and the reproducing scanning locus of the reproducing magnetic head. During still image playback, in which the tape is stopped at an optimal position and played back after sending out noise, the reference pilot signal for obtaining the tracking error signal is fixed to obtain the tracking error signal, and the tracking error signal is The present invention is characterized in that the optimal tape stop position is detected by both of the two heads used during still image reproduction.

In other words, as shown in FIG. 4, when performing field still image playback, if the head used is A azimuth, the optimal tape stop position is when scanning shown by the scanning trajectory (21) or (22) is performed. At this time, if the reference pilot signal input from the terminal (5) to the balanced modulation circuit (4) in Fig. 2 is fixed at f□, the output of the comparator circuit (10) can be expressed as As shown in (b) and (c) of Fig. 5, each time the head is switched, the output of the comparator circuit (10) of Fig. 2, that is, the on-track pulse generated by the tracking error signal obtained from both heads, and the head switching signal are generated. The tape is intermittently fed until the tape stop position reference pulses generated by the above match, and when both pulses match, tape feeding is prohibited,
It performs field still image playback.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 9 and 10.

In FIG. 9, the head switching signal (nu) is input from the terminal (46), and the head switching signal (nu) is inputted from the terminal (46).
A monostable multivibrator (
47) and a falling-triggered monostable multivibrator (48). The outputs of the monostable multivibrators (47) and (48) are pulse outputs (l) and (w) for determining the stop position of the tape, each having an appropriate time width synchronized with the head switching signal (n).
get. The above pulse output (ru) (wo) is the synthesis circuit (49
) to obtain a composite output (wa). In this embodiment, the synthesis circuit can be replaced by an AND circuit. The above composite output (
W) is input to a differentiating circuit (50), and a pulse output (force) with a relatively short time width is obtained as its output. On the other hand, the tracking error signal output from the level comparator circuit (lO) shown in FIG. 2 is input to the terminal (11). The tracking error signal is input to an on-track pulse generation circuit (51), which generates a pulse output (Y) when the tracking error signal passes through the zero reference. Pulse output (Yo)
is input to a monostable multivibrator (52) which is triggered by the rising edge of the signal to obtain a gate pulse (RI) having a constant time width. The gate pulse (RI) and the above-mentioned differential pulse (force) are input to a sending pulse generation circuit (53). The sending pulse generation circuit (53) generates a differential pulse (
The positive pulse of force) is a monostable multivibrator (52)
A sending pulse (shi) with a constant time width synchronized with the positive differential pulse is generated when the pulse is outside the gate period of the monostable multivibrator (52), and the positive differential pulse is within the gate period of the monostable multivibrator (52). In some cases, a configuration is adopted in which the above-mentioned sending pulse is prohibited.

Therefore, if you set the delay amount of the monostable multivibrator (47), (48), and (52) as in the conventional example, the capstan motor will be activated when the mode is changed from the normal tape playback state to the still image playback state. When driven by the above-mentioned feed pulse (shi), the on-track pulse (y) obtained from the above-mentioned tracking error signal moves from left to right as shown in the arrow ■ direction in the figure as noise is sent out, and the on-track pulse (y) obtained from the above-mentioned tracking error signal moves from left to right as shown in the arrow ■ direction in the figure. The tape feeding pulse (shi) is inhibited when the differential pulse (force) indicative of the stop reference position coincides with the stop reference position, and the tape can be stopped at the optimal position.

Effects of the Invention The still image playback method of the present invention detects the optimal tape stop position with two heads used during field still image playback in a VTR that performs tracking control using pilot signals, so it is not necessary to use conventional methods. It is possible to prevent an operation in which the tape is stopped when the output of one head is extremely small due to a difference in head touch or the like.

Further, in the present invention, the head switching signal It HI
Since the tape stop position is detected during both the + level and the rrL'' level, that is, at a period 1/2 compared to the conventional example, there is an advantage that variations in the stop position are reduced.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the recorded magnetization trajectory using the 4-frequency pilot signal method, Figure 2 is a block diagram of the circuit that obtains the tracking error signal, and Figure 3 is the frequency of the reproduction reference pilot signal with respect to the recording pattern. Figure 2 shows the output waveform of the comparator circuit, Figure 4 shows the locus of the rotary head when field still image playback is performed, and Figure 5 shows the head switching signal and single waveform when field still image playback is performed. A diagram of the relationship between the output of the comparator circuit when the reference pilot signal is continuously input, Figure 6 is a circuit block diagram of the conventional example, Figure 7 is an operating waveform diagram in the configuration of the conventional example, and Figure 8 is field stationary. When three heads are mounted on a cylinder for image reproduction, the installation of the heads is shown in figure 9, which shows the positions.
The figure is a block diagram of a specific embodiment of the still image reproducing method of the present invention, and FIG. 10 is an operation waveform diagram of FIG. 9. (3)...Low pass filter, (4)...Balanced modulation circuit, (5)...Reference pilot signal input terminal, (6)
(7) Tuned amplifier circuit, (8) (9) Detection rectifier circuit, (10) Level comparison circuit, (11)
...Tracking error output terminal, (21) (22)
...Head trajectory during field still image playback, (41)
(42) (43)...video head, (46)...
...Head switching signal input terminal, (47) (4
8) (52)...monostable multivibrator, (49
)...Synthesis circuit, (50) Differential circuit, (51)...
On-track pulse generation circuit, (53)... Substitute for the feed pulse generation circuit Yoshihiro Morimoto Figure 3 Figure 4 f, f4f, f, f, f. Figure 5 Figure 6 Figure 7 Figure β Figure 2

Claims (1)

[Claims] 1. A rotating magnetic head is used to record and reproduce a video signal on a magnetic tape as a group of discontinuous inclined recording tracks, and at the time of recording, a pilot signal for tracking control is recorded together with the video signal, and the video signal is reproduced. Sometimes a tracking error signal is used to determine the relative relationship between the recording track and the reproducing scanning trajectory of the reproducing magnetic head using a tracking error signal corresponding to the level difference of the crosstalk signal of the pilot signal reproduced from the recording track adjacent to the recording track before and after the recording track to be reproduced. When performing position control, during still image playback, a reference pilot signal for obtaining a tracking error signal is fixed to obtain a tracking error signal, and from this tracking error signal, both of the two heads used for still image playback determine the position of the tape. A still image playback method for a magnetic recording and playback device that detects an optimal stop position. 2. On-track pulse created by tracking error signals obtained from both heads each time head is switched;
Claims characterized in that the tape is intermittently advanced until tape stop position reference pulses generated from head switching signals match, and when both pulses match, tape feeding is prohibited and field still image reproduction is performed. 2. A method for reproducing still images using a magnetic recording and reproducing device according to item 1.