JPS60201560A - Tracking controller for still reproduction - Google Patents

Abstract

PURPOSE:To attain still reproduction at a normal tracking position at all times by utilizing that a tracking signal obtained with still reproduction at a normal tracking position is a rectangular wave signal whose polarity is inverted with a duty of nearly 50% in one field to detect the polarity inversion. CONSTITUTION:A reproducing signal S1 of rotary heads HA, HC selected by the 3rd switching circuit 11 at still reproduction is applied to a pilot signal detectin circuit 15, from which a pilot signal S2 is detected and the signal is fed to a multiplier 13 of a tracking signal forming circuit 20, where the signal is multiplied with a reference pilot signal S3. A multiplied output S4 is fed to DELTAfA, DELTAfB detection circuits 21, 22, where the frequency difference component is detected, each detected output is fed to DC generating circuits 23, 24 of diode constitution and envelope outputs S5, S6 are generated. The subtraction of S6-S5 is conducted by a subtraction circuit 26, and the polarity of a tracking signal S7 for still reproduction is inverted when the track changes from T2 to T1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention records a plurality of M types of pilot signals with different frequencies on a video signal recording track together with the video signal, and performs auto-tracking based on the pilot signals obtained during playback. The present invention relates to a tracking control device for still playback that is suitable for application to a camera-integrated VTR or the like.

Background Art and Problems A camera-integrated VTR has been proposed in which a plurality of types of pilot signals with different frequencies are recorded together with the video signal on a video signal recording track, and the pilot signals are detected and tracked during playback. There is.

For example, as shown in FIG. 1, four pilot signals P1 to P4 with different frequencies (their frequencies are 11 to f4) are sequentially transferred to the corresponding recording track T1 along with the video signal.
-T4, and during reproduction, the frequency difference between pilot signals reproduced from adjacent tracks is detected and trasoking servo is performed so that the reproduction head (rotary head) is positioned on a predetermined track.

The frequency difference can be determined from the multiplication output of the reproduced pilot signal and the reference pilot signal. The reference pilot signal is the normal trunking poem people's recording track T1~T4
The frequencies f1 to f4 are respectively selected so as to correspond to the more regenerated pilot signal, and the signals are configured as signals that circulate in the same order as the pilot signal. Therefore, if the current track is played back shifted to the right side of the regular track, the relationship between the playback pilot signals P1 to P4 (hereinafter collectively referred to as S2) and the reference pilot signal S3 will be the same as the second one. It will look like Figures B and C, l)
Of the calculated power S4, ΔfA=l ft -b l-l f3-f41=14
(KHz) ΔfB = l'h - h l = l f
4-h l -44(kllz), the frequency difference Δ
By detecting fA+Δfs (D in Figure 2), it is possible to determine which track the playback head is tracing out of the adjacent trunks, so this frequency difference Δ
f8.

Tracking servo can be performed based on ΔfB.

Note that the pulse RF-SW in FIG. 2A does not include a head switching pulse for sequentially and alternately switching the signals reproduced by the pair of rotary heads. ”-the pilot frequency f l”
f 4 is a low frequency, fx = 102 (KHz)
, f2-116(Kllz), f3=160(
Kllz).

f4=146 (KHz) is selected.

When playing still images on a VTR that uses such an automatic track following method (ATF method), noise bands caused by the rotating head scanning guard bands between tracks or trunks that differ from the recording azimuth are eliminated, and the S/N is improved. Various proposals have been made to obtain still images with good quality.

For example, the above objective is achieved by attaching a rotating head to a position control element such as a bimorph plate, detecting the angular difference between the head scanning trajectory and the playback track during still playback, and controlling the position control element using this detection output. .

However, in such a tracking control device for still playback, it is necessary to attach a rotary head to the position control element, which has the disadvantage of complicating the configuration. It is necessary to provide a detection system for detecting the angular difference between the two and a control system for controlling the position control element based on the detection output, which results in an increase in the size of the ileocecale.

OBJECT OF THE INVENTION Therefore, the present invention proposes a tracking control device for still playback of this type, which has a significantly simplified mechanical and electrical configuration.

Summary of the Invention Therefore, in this invention, noiseless still playback is realized by using a rotary head exclusively for variable speed playback and skillfully utilizing the output of an ATF error detection system. reproducing the pilot signal recorded on each video trunk by a pair of rotary heads, and forming a tracking signal corresponding to the still scanning locus by multiplying the pilot signal and a reference pilot signal corresponding to the reproduced video track; This tracker 2 tracking signal is fed to the level comparator (j) so that the tracking signal whose polarity changes in the center of the same field is detected by the level comparator. Tracking servo is performed during still playback.

According to this configuration, a position control element for the rotary head is not required, and a drive control system for this position control element is also not required, so that the mechanical and electrical configuration can be significantly simplified compared to the conventional one.

Embodiment Next, an example of a tracking control device for still reproduction according to the present invention will be explained in detail with reference to FIG. 3 and subsequent figures.

FIG. 3 shows an example of a rotating magnetic head device (2) suitable for use in the present invention, in which a rotating magnetic head device (3) has a pair of rotating magnetic head devices for both recording and reproducing purposes, with an angular spacing of approximately 180°. A rotating head H is provided with an HB. This rotating head HA
+ HB is selected at different azimuth angles. On the HB side of the rotary head, there is a position that is rotationally ahead of this one, at a predetermined interval, and a position that is 1 to several H (H is the horizontal period) away from this in one hour, and is dedicated for variable speed playback of slow, still, etc. A rotary head Hc is provided, the azimuth angle of which is selected to be the same as that of the other rotary head H^. Therefore, rotating head HB
.

A double azimuth type rotating head is used for Hc. In variable speed playback mode, rotary heads HA and HC are used as playback heads.

In still playback mode, track and rotate nodes HA, H.
The relationship between c and the scanning locus is shown in Fig. 4. Let us now assume that track T1 is the track on which field image information has been recorded by the rotating head HA of positive azimuth, and that the field image information of this trunk Ti is When playing stills, the scanning locus of the rotating heads H^ and Hc is
The noise is the least when , and the noise occurs within the vertical blanking period.

That is, as shown in FIGS. 5A to 5C, the rotary head HA traces the track T1 during the period W1, and the rotary head Ha traces the same track T1 during the period W2, so that the reproduced output (FM luminance signal Envelope E of Y)
^ will be as shown in Figure B.

Envelope EA is maximum at the center of track T1.

The second level is obtained at the start and end of the trunk T1, and a small amount of noise sN is generated at the start and end (FIG. 3C). However, since this noise generation position corresponds to the vertical blanking period, it does not appear on the screen, making noiseless still playback possible.

On the other hand, when the scanning locus is LB in Fig. 4,
Since the envelope output is E as shown in the fifth diagram, a considerably large noise appears at the upper side of the screen (E in the same figure). Similarly, when the scanning trajectory is Lc, the envelope output Ec
The image becomes F in Fig. 5, and noise appears at the bottom of the screen (G in the same figure). For this reason, in order to perform noiseless still reproduction, it is necessary to control the scanning locus so that it becomes LA.

FIG. 6 shows a tracking control device 0 for still playback according to the present invention for performing noiseless still playback as described above.
An example of 0) is shown below.

During normal playback, each playback signal from the rotary heads HA, H is made into a continuous playback signal by the first switching circuit (11^), and during still playback, the playback signals from the rotary heads HA, Hc
The reproduced signals are made into continuous reproduced signals by the second switching circuit (IIB), and these continuous reproduced signals are converted by the third switching circuit (IIC) according to the respective reproduction modes. selected. 1st~
The third switching circuits (11^) to (IIC) are control circuits 5. (30) is controlled by a switching control pulse (not shown) obtained from (30).

During still playback, the playback signal S1 of the rotary heads HA and Hc selected by the third switching circuit (IIC) is transmitted to the biloft signal detection circuit (12
), the pilot signal S2 is detected, and this signal is supplied to the multiplier (13) provided in the tracking error signal forming circuit (20), which also functions as a tracking error signal forming means during normal reproduction. Multiplication with pilot signal S3 is performed.

The reference pilot S3 sent out from the reference pilot generating circuit (14) corresponds to the pilot signal s2 reproduced from the normal tracking extra-large recording trunks T1 to T4, that is, P1=, P4 during normal reproduction. The same frequencies f1 to f4 are respectively selected so that the pilot signals S2 and S2 are configured as signals circulating in the same order as the regenerated pilot signal S2 (FIG. 2B). On the other hand, during still playback, any one of P1 to P4 is fixed to number 16. In this example, since the track T1 is used as a still reproduction track, it is fixed to the reference pilot signal S3 of frequency f1.

The reference pilot generation circuit (14) is thus used both during normal playback and during still replay, and is connected to the generation port II (15) of the pilot frequencies r1 to f4 and its output by switching it for each track. A switch circuit (16) is provided, and the switch circuit (16) is controlled based on a control signal sent from a control circuit (30).

The multiplication output S4 is a detection circuit (21) for ΔfA and ΔfB.

(22), the frequency difference component is detected, and the detection output of the husband is sent to a diode-configured DC conversion circuit (23).

(24) to form envelope outputs Ss, Ss.

By the way, when the trunk T1 is reproduced to form video information for a still image, the reference pilot signal S3 is fixed to the pilot frequency f1 corresponding to the rack T1 (FIG. 7B). Assuming that the scanning trajectory of the axis heads HA and HC this time is I-A, the heads are shifted to the right in the first half of the track T1, so the pilot signal P1 of frequency f1 and the frequency from the adjacent track T2 are T2
A crosstalk pilot signal P2 having a frequency of T4 is simultaneously reproduced in the latter half of the track T1, and a crosstalk pilot signal P4 having a frequency of T4 is simultaneously reproduced in addition to the pilot signal P1 due to the left shift in the latter half of the track T1 (FIG. 7C).

Therefore, components of the frequency difference Δf8 and ΔrB are obtained alternately (D in the same figure), and the envelope output S5 of the frequency difference ΔfA gradually decreases toward the center of the track T1 (E in the same figure), and the frequency difference ΔfB The envelope output S6 gradually increases from the center (FIG. F).

These envelope outputs Ss and Ss are the subtraction circuit (26)
S6Ss is subtracted, and as a result, a tracking signal S7 for still reproduction shown in FIG. 7G is obtained. Tracking signal S7 is from track T2 to T1
, that is, the polarity is reversed from negative to positive at exactly point 2 of 1 field.

On the other hand, the scanning of the rotating heads HA and Hc! 1i When the IL trace is LB, it is shifted further to the right than LA, so the tracking signal S7 at this time
is obtained in the state of S7<0, as shown in the eighth diagram. When Lc is further shifted to the left than the scanning locus LA, the above is reversed, so that a tracking signal Sv (>0) that looks like a blur is obtained at the 8th νIF.

As is clear from the above, the rotating belly button I/'H8.

In order to detect that the HC is on the correct scanning locus LA-HI and to make it zero on the I-8, it is sufficient to detect the polarity and level of the tracking signal S7.

For this purpose, the I/ranking signal S7 is sent to the amplifier (28).
The signal is supplied to the level comparator (29) via the reference level VR and compared with the reference level VR. This example shows the case where the DC level of the tracking signal S7 is zero, so vR=
o. Each time the tracking signal S7 shown in FIG. 8B is passed through the level comparator (29), a level comparison signal S8 which is inverted at the center of the track T1 as shown in FIG. 8C is obtained when the tracking signal S7 shown in FIG. 1, a level comparison signal Ss (E in the same figure) having a constant negative level is obtained for the right-shifted tracking signal S7 shown in the figure, and a constant positive level for the left-shifted tracking signal S7 shown in the same figure F. A level comparison signal S8 (G in the same figure) is obtained.

Such a level comparison signal S8 is sent to the switch circuit (16)
and a control circuit (30) for the capstan motor (not shown).
), and control is performed so that the scanning locus during still playback becomes LA.

FIG. 9 is a flowchart of an example of this 1-racking servo, and FIG. 10 is a waveform diagram for explaining its operation.

First, when switching to the still playback mode at any point a during normal playback (step (41) in Figure 9), the frequency of the reference pilot signal S3 becomes the cycle fl. If fl is detected, the frequency is fixed to fl in step (42), and 1
After m5ec has elapsed, in step (43), a reverse pulse CCW (Fig. 10E) is sent to the capstan, and the reverse brake is applied for 5m5ec in this example to stop the tape drive and turn off the capstan. A pulse CAPON (D in the figure) is supplied so that the capstan also stops after the reverse braking is completed.

In addition, in this step (43), the second switching circuit (IIB) is supplied with the switching pulse 5 shown in FIG. 10C.
W2 (Fig. fO C) is supplied and the rotating head H^, Hc
A reproduced signal is supplied to the forming circuit (20).

Next, in step (44), the field number counter is reset, and in step (45), a rising edge or a falling edge of the head switching signal RF-SW is detected, and when either edge is detected, step ( 46) and waits 6m5ec in this example, it is determined in step (47) whether the level of the level comparison signal S8 is "T4", and if it is rLJ, it is again determined in step (48) that it is rising or falling in this example. After waiting 7m5ec with the edge as a reference, in the next step (49), the same level comparison signal S
It is determined whether the level of 8 is [H-1 or not.

That is, through steps (44) to (49), it is determined whether the level comparison signal S8 is C, E, or G in FIG. When the scanning locus is LA, the level comparison signal S8 is inverted in level at the center of the track T1, and is 6 m5ec from the edge of the head switching signal RF-SW.
The later level is rLJ, and the level for 1m5ec is rHJ, so the level comparison signal S shown in Figure 8C is
8 is supplied to the control circuit (30), the 'III definite result of I'yesJ is obtained from step (49),
When this is obtained, a stop command signal is sent to the capstan motor in step (50).

Next, in step (52) it is determined whether or not the frame forwarding mode is in effect, and if it is not in the frame forwarding mode, step (45) is performed.
The determination of the level comparison signal S8 is repeated through the steps described above, but the determination of whether or not the level comparison signal S8 is the level comparison signal S8 shown in FIG. 8C is performed over a period of at least two fields. As a result of a total of four determinations made during these two field periods, if it is determined that none of the level comparison signals Se is shown in FIG. Correction is performed so that the trajectory becomes LA.

Therefore, first, in step (47), the level comparison signal S
It is determined whether 8 is a positive DC signal as shown in FIG. 8G or a rectangular wave signal as shown in FIG. 8C. As a result of the determination, if it is 1°noJ, step (60) the odor "ζ field counter is incremented, and step (60)
In I), the content of the counter is determined, and if N=4 is not established, the process returns to step (45) and a similar determination loop is formed. Then, when N=4 is detected in step (61), it is determined for the first time that the level comparison signal S8 is a DC signal with a difference between G in FIG. 8, and step (62) is performed.
The capstan motor is driven in forward rotation. This drive may be either step feed or continuous feed, but in the case of step feed, a feed pinch is selected such that the scanning locus changes from Lc to approximately IA with l step feed.

When the 1E rotation is driven, the field counter is reset in step (63), and then the process moves to step (45). By step-feeding the tape, the scanning locus of the rotary heads HA, Ha changes from Lc to LA.

On the contrary, in step (47), the level comparison signal S8 is a negative DC signal as shown in FIG. 8E.

It is determined whether the signal is a rectangular wave signal shown in FIG. 8C. If the result of the determination is r noJ, step (65
), the field counter is incremented,
In step (66), the contents of the counter are determined and N
If not =4, the process returns to step (45) and a similar determination loop is formed. Then, in step (66) N=
4 is detected, the level comparison signal S8 is detected for the first time.
It is determined that the signal shown in FIG. 8E is a DC signal, and the capstan motor is driven in reverse at step (67).

When reversely driven, the field counter is reset in step (68), and then the process moves to step (45). By step-feeding the tape, the scanning loci of the rotary heads HA, Hc change from LB to LA.

Note that when the frame advance mode is selected, the track at the time of still repopulation can be changed from T1 to T3, so if it is determined that the frame advance mode is selected in step (52), the tape (53) The reference pilot frequency is fl
to f3.

When it is in trunk T3, f3 is changed to fl.

In addition, in FIG. 6, the neo formation circuit (20) generates the tracking error signal SI! during normal playback. It is also used to detect.

In this case, the switching circuit (27A) provided between the subtraction circuit (26) and the amplifier (28) operates, and a tracking signal (in this case, a tracking error signal) is generated by supplying the head switching signal RF-S. 37 and a signal 7 whose phase is inverted by an inverter (27B) are output while being alternately switched.

When there is a deviation to the right or left with respect to normal tracking, a DC signal with a polarity and level corresponding to the direction and amount of deviation is obtained, so this tracking error signal SI! By supplying this as a control signal to the capstan servo system, the servo is prevented from performing normal trunking.

Fit command signal from control circuit (3o) during still playback.

The switching circuit (27A) is then held in the switching state shown.

Effects of the Invention As explained in 2, according to the present invention, the tracking signal obtained when still playback is performed at a compact tracking position has a duty of approximately 50% within one field and has a rectangular polarity inversion. Focusing on the fact that the signal is a wave signal, we devised a way to detect this polarity reversal and always perform still playback at the normal tracking position.

This has the feature that noiseless still playback can always be realized.

Therefore, according to the configuration of the present invention, there is no need for a position control element for the rotary head, and there is also no need for a drive control system for this position control element.

The electrical configuration can be significantly simplified compared to the conventional one.

Further, according to the present invention, the circuit for forming the tracking error signal SBI used during normal playback can be used to form the tracking signal s8 during still playback, so the circuit configuration can be simplified. It has a soothing effect.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between pilot signals and trunks;
Fig. 2 is an explanatory diagram of a tracking error signal, Fig. 3 is a diagram illustrating an example of a rotating magnetic head device, Fig. 4 is a diagram used to explain still reproduction, and Fig. 5 is an illustration of how the reproduction is output when a still is generated. FIG. 6 is a system diagram showing an example of a tracking control device for still playback according to the present invention.
Figures 7 and 8-1 are waveform diagrams for explaining the operation, and Figure 9.
The figure is a flowchart showing an example of a still playback control system.
FIG. 10 is a waveform diagram accompanying this flowchart and used to explain the operation. HA and HB are rotating heads for normal playback, Hc is a rotating head dedicated to still playback, (2o) is a tracking signal forming circuit, (29) is a level comparator, S8 is a level comparison signal, (3o) is a control circuit It is. Figure 1 Figure 2 Figure 7 Figure 8

Claims (1)

[Claims] In this system, a plurality of pilot signals with different frequencies are recorded on a video track together with a video signal, and a traffking servo is applied based on the reproduced pilot signal. The recorded pilot signal is played back,
This pilot signal is multiplied by the reference pilot signal corresponding to the reproduced video track, and from this H) calculation output, a trunking signal corresponding to the still scan uL trace is formed, and this tracking signal is sent to the level comparator (j Still playback is such that tracking servo is performed during still playback using the level comparison signal from the level comparator so that the level comparator detects a tracking signal whose polarity changes in the center of the same field. tracking control device.