JPH0648568B2 - Tracking controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention records a plurality of types of pilot signals having different frequencies together with a video signal on a video signal recording track, and performs auto-tracking based on the pilot signal obtained during reproduction. The present invention relates to a tracking control device suitable for application to a camera body type VTR or the like.

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

For example, as shown in FIG. 1, four pilot signals P _{1 to} P ₄ (the frequencies of which are ₁ to ₄ ) having different frequencies are sequentially recorded with a video signal, and corresponding recording tracks T ₁
Recorded on through T _4, in which reproduced by detecting a frequency difference of the pilot signals reproduced from tracks adjacent to each other at the time of reproducing heads (rotary head) performs tracking servo so as to be positioned on a predetermined track. The pilot frequencies ₁ to ₄ are low frequencies and are selected as ₁ = 102 (KHz), ₂ = 116 (KHz), ₃ = 160 (KHz), and ₄ = 146 (KHz).

A tracking control device adopting such an automatic track following system (ATF system) can be realized by configuring as shown in FIG.

The reproduction signal S ₁ supplied to the terminal (1) is supplied to the pilot signal detection circuit (2) having a low-pass filter configuration, and from the reproduction signal S ₁ , the pilot signals P _{1 to} P ₄ (hereinafter these are collectively referred to as S ₂ Is detected and is supplied to a multiplier (4) provided in the tracking error signal forming circuit (3) to be multiplied by the reference pilot signal S ₃ .

The reference pilot signal S ₃ sent from the reference pilot generating circuit (5) corresponds to the pilot signals S ₂ reproduced from the respective recording tracks T _{1 to} T _{4 during} normal tracking, that is, P _{1 to} P ₄ , respectively. Same frequency ₁ ~
₄ and is configured as a signal that circulates in the same order as the reproduced pilot signal S ₂ .

Therefore, the reference pilot generation circuit (5) is provided with a generation circuit (6) for pilot frequencies ₁ to ₄ and a switch circuit (7) for switching its output for each track, and the switch circuit (7) has a head switching function. A pulse RF-SW (Fig. 3A) is supplied. The reference pilot signal S ₃ indicating this change over pulse RF-SW in Figure 3 B is obtained.

For this reason, when the reproducing head does not normally track and is now displaced to the right and is tracing, the reproduced pilot signal S ₂ contains pilot signals P ₂ , P ₃ , P ₄ , P recorded on adjacent tracks. ₁ is output in the state of including each (FIG. 3C).

Among the multiplication output _{S 4, Δ A = | 1} - 2 | = | 3 - 4 | = 14 (KHz) Δ B = | 2 - 3 | = | 4 - 1 | = 44 if (KHz), the frequency By detecting Δ _A and Δ _B , it is possible to know which of the adjacent tracks the reproducing head is misaligned with.
₄ is supplied to the Δ _A and Δ _B detection circuits (11) and (12) to detect the frequency difference component, and the respective detection outputs are the DC conversion circuit.
It is supplied to (13) and (14).

As described above, if the tracing in a state where the reproducing head is shifted to the right, of the multiplication output S ₄ between the reproduced pilot signal S ₂ and the reference pilot signal S _3, included in the reproduced pilot signal S ₂ Since the multiplication calculation power (frequency difference component) between the reproduced pilot signal of the crosstalk component and the reference pilot signal S ₃ is Δ _A , Δ _B , Δ _A , Δ
Focusing only on the _B component, each of the tracks T _{1 to} T ₄
From the frequency difference components Δ _A , Δ as shown in FIG. 3D.
_B is detected. Therefore, from the DC circuit (13), the third
The detection output S _{5 of} FIG. E is obtained, and the detection output S _{6 of} FIG. F is obtained from the other DC conversion circuit (14).

The detection outputs S ₅ and S ₆ are supplied to the subtractor (15) and are connected to the G in FIG.
The signal S ₇ shown in is formed, and this signal S ₇ and the signal obtained by inverting the phase of this signal by the inverter (16) And are alternately and sequentially switched in the switching circuit (17), and the tracking error signal S shown in FIG.
_E is formed.

Since the DC level of the tracking error signal S _E corresponds to the deviation amount from the regular track, if this tracking error signal S _E is supplied to the capstan servo system, the tracking error of the reproducing head can be corrected. You can

When the reproducing head is tracing while deviating to the left with respect to the regular track, the pilot signal S ₂ becomes I in FIG. 3, the multiplication calculation force S ₄ becomes J in FIG. 3, and the tracking error signal S _E becomes Since it has a negative DC level (K in the same figure), it is possible to correct the tracking error even when it is shifted to the left side.

By the way, when the tracking servo is not yet fully operating, such as when the tracking servo is rising, the subtraction output S ₇ for forming the tracking error signal is as shown in FIG.

That is, when the read head causes a track shift in the positive direction (rightward direction) with reference to the track T ₁ , a positive tilt is generated until the tracking shift amount becomes one track pitch, that is, the adjacent track T _2. Will increase with. This is because Δ _B = 0 and Δ _A increases corresponding to the tracking shift amount while the reproducing head is between the tracks T _{1 and} T ₂ . The amount of increase takes a maximum value on the track T ₂ , and thereafter, the subtraction output S ₇ decreases with a negative slope during the range (T _{2 to} T ₄ ) in which the amount of tracking deviation increases by two track pitches, and the track output is reduced. It becomes 0 at the position of ₃ , and then becomes a negative value. This phenomenon has a maximum negative value at the position of the track T ₄ , and when the tracking deviation amount exceeds this position T ₄ , the subtraction output S ₇ again increases with a positive inclination for two track pitches.

As described above, when the servo is started up, the subtraction output S ₇ is repeatedly increased and decreased in a triangular waveform at a cycle of every 4 track pitches. To changes of the subtraction output S _7, between S _{7> 0} decelerates the capstan motor, between S _{7> 0} is tracking servo such that the speed increasing is performed.

Therefore, if the subtraction output S ₇ increases in the positive direction at the lock point T ₁ , the capstan motor is decelerated so that the tracking deviation amount decreases. Also, the subtraction output S ₇
However, even if is increasing in the negative direction, the capstan motor is similarly decelerated and the tracking deviation amount is corrected while S ₇ > 0. In this way, the reproducing head has S ₇ =
It will be locked at the phase point T ₁ which becomes zero.

If S ₇ <0, the capstan motor will be accelerated and locked at the next phase point T ₅ in the future.

Although S ₇ = 0 also at the phase point T ₃ , this phase point T 3
_{If the} subtraction output S ₇ deviates slightly from _{3 in the} positive direction or the negative direction, the above-mentioned servo loop operates and the phase point T ₃ cannot be a stable point. Therefore, the phase point T ₃ becomes an oscillation point. Become.

Due to such a servo loop working, when the tracking is shifted near the oscillation point, the reproducing head cannot reach the stable lock point unless it is corrected by two tracks. That is, the conventional tracking control device
In (10), there is a drawback that it takes time to return to normal tracking.

SUMMARY OF THE INVENTION Therefore, the present invention is intended to shorten the servo lock time by speeding up the stable pull-in operation to the lock point even when the reproduction track is deviated to near the oscillation point.

SUMMARY OF THE INVENTION Therefore, in the present invention, when the reproduction track is displaced close to the oscillation point, this oscillation point is devised so as to become the pseudo-lock point. That is,
The phase of the subtraction output is forcibly changed by 180 ° by the detection output of the error signal forming circuit obtained when the frequency difference component as the subtraction output is not within the predetermined lock-in range. The phase change may be performed by inverting the phase of the subtraction output, or may be performed by skipping the circulation order of the reference pilot signal by a predetermined number of stages.

Embodiment Next, a case where an example of the tracking control device according to the present invention is applied to the above-mentioned camera body type VTR will be described in detail with reference to FIG.

FIG. 5 is a system diagram of a main part showing an example of the tracking control device (10) according to the present invention, and FIG.
FIG. 6 is a diagram showing a relationship between a composite reference pilot signal S ₃₀ used for 0) and a reproduction pilot signal S ₂ .

In the present invention, as shown in FIG. _6A , the circulation order of the reference pilot signal S _3a is shifted by one pitch to each front half of the reference pilot signal S _3a for tracking error detection which circulates at each head switching timing. In this example, the composite reference pilot signal S ₃₀ in which the reference pilot signal S _3b for detecting the oscillation point, which is 90 ° in phase with respect to the reference pilot signal of frequency ₁ , is inserted, is used.

When the composite reference pilot signal S ₃₀ is supplied to the multiplier (4) and the tracking servo is not activated,
The subtraction output S ₇ (Δ _A −Δ) for the tracking error signal formed from the multiplication calculation force of the reference pilot signal S _3a for detecting the tracking error and the reproduction pilot signal S _2.
B ) has characteristics as shown by the curve l ₁ in FIG. 7A.
If the phase of the subtraction output S ₇ is changed by 180 °, the curve l ₃ shown in FIG. 7C is obtained. Therefore, the subtraction output shown by the curve l ₃ is obtained. The lock point of 1 corresponds to the oscillation point of the subtraction output S ₇ .

Therefore, when the tracking displacement amount is near the oscillation point of the subtraction output S ₇ is to force the phase of the subtraction output S ₇
Tracking deviation amount is subtracted by changing 180 ° Since it exists near the lock point of, the pulling in to the lock point becomes very fast.

In order to perform such processing, the reference pilot signal S
_3b is used. That is, the subtraction formed from multiplying the output of the reference pilot signal S _3b for oscillation point detection reproduced pilot signal S ₂ output _{S 9 (= Δ A -Δ B} ) , the reference pilot signal S _3b the reference pilot signal S _3a 90 °
Since the phase advance, Noting that a characteristic as shown in curve l ₂ in FIG. 7 A, set the detection level V _R as shown in FIG. 7 B, the subtraction output S ₉ is the detection subtraction output when it becomes less than the level V _R Is configured to be output.

Therefore, the detection level V _R is set to a predetermined error range including the oscillation point T ₃ (predetermined lock-in range).

Therefore, when the tracking shift amount is near the oscillation point T ₃ and S ₇ > 0, the arrow a in FIG.
The tracking servo works in the direction indicated by. Subtract output at this time Since will work the tracking servo in the direction indicated by the arrow a with respect to, the tracking deviation amount comes reduced, eventually the level of the subtraction output S ₉ is equal to or smaller than the detection level V _R, subtraction in the detection output of the time output Is selected. By this selection, S ₇ <0 (7th
(Figure C). In this polarity, since the tracking servo works so that S ₇ = 0, the tracking shift amount is corrected in the direction shown by the arrow c in FIG. 7C, and the pulling to the lock point is performed in a short time. Become.

When the tracking displacement amount contrary to the above-described near the oscillation point T _3, and a S _{7 <0} is an arrow b, the tracking servo acts on b 'direction, the subtraction output S ₉ is equal to or less than the detection level V _R Output when subtracted Is selected, and the tracking deviation amount is corrected in the direction indicated by the arrow d. Therefore, also in this case, the pulling to the lock point is performed in a short time.

In order to achieve such a detection operation, a detection system as shown in FIG. 5 is newly provided.

Head switching pulse RF-SW is supplied to the monostable multivibrator (21), the sixth pulse P _S shown in FIG. D is formed which is a composite reference pilot signal shown in FIG. 6 A is supplied to the switch circuit (7) S ₃₀ is formed.

Direct current circuit (13), and each signal S _5, S ₆ between the (14) and a subtraction circuit (15), selection switch which can select the phase inverted signal (23), provided with (24) To be (25) and (26) are inverters for phase inversion, and the selection switches (23), (2
4) is switched in conjunction. In the switching state shown, the subtraction output S ₇ is obtained, and in the switching state opposite to this, the subtraction output phase-shifted by 180 ° Is obtained.

The output signal S ₈ of the switching circuit (17) is supplied to the first and second sampling and holding circuits (27) and (28),
In the sampling hold circuit (27) of FIG. 6, the output signal S ₈ of the period W ₁ shown in FIG. 6 is sampled and held,
The hold output is used as the tracking error signal S _E. In the second sampling and holding circuit (28), the output signal S ₈ of the period W ₂ is sampled and held,
This is used as the subtraction output S ₉ for detecting the oscillation point.

Therefore, the pulse P _S formed by the mono-multi (21) is phase-inverted by the inverter (31) and is the first sampling pulse. As shown in FIG. 6E, the first sampling and holding circuit (2
7) and the pulse P _S itself is used as a second sampling pulse in the second sampling and holding circuit (2
Supplied to 8).

The subtraction output S ₉ is sent to the level detection circuit (33) via the amplifier (32).
Is supplied to. This level detection circuit (33) has a detection level V
_It has a level comparator with _R as a reference level (threshold level), and a flip-flop (34) with its comparison output.
Operates and the output pulse S ₉ is inverted every time the level of the subtraction output S ₉ becomes equal to or lower than the detection level V _R. This output pulse S ₉ is used as a selection pulse for the selection switch (2
It is commonly supplied to 3) and (24).

According to this structure, the subtraction output S ₇ by the selection pulse S ₉ the level of the subtraction output S ₇ is reversed each time it is below the detection level V _R And are alternately output, and the above lock-in operation is performed.

Since it is not necessary to perform such an operation during recording, the recording pulse P _R controls the monomulti (21) and the flip-flop (34) in the reset mode. Thus, from the generator circuit (5) outputs the reference pilot signal S _3b without normal reference pilot signal S _3, a pair of selection switches (23), (24) is locked to the switching state shown.

Subtraction output S ₇ and Can also be formed by inverting the phase of the switching pulse RF-SW supplied to the switching circuit (17) as shown in FIG. That is, the inverter (35) and the selection switch
(36) are provided, and this selection switch (36) is used to select pulse S ₉
If controlled by, the same operation as described above can be achieved.

In the above description, the signals S ₅ , S ₆ or the switching pulse RF-SW are phase-inverted, so that the subtraction output 180 ° out of phase is output. However, when the selection pulse S ₉ is supplied to the switch circuit (7) and the tracking shift amount is near the oscillation point, the circulation order of the reference pilot signal S _3a is skipped by a predetermined number of steps. Subtraction output Can be formed.

As described above, according to the configuration of the present invention, the lock-in time of the tracking error can be greatly shortened as compared with the configuration of FIG. 2, so that the tracking correction can be performed quickly. Have.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a reference pilot signal and a recording track, FIG. 2 is a system diagram of a tracking control device used for explaining the present invention, and FIGS. 3 and 4 are waveform diagrams used for explaining the operation thereof. 5 and 8 are system diagrams showing an example of the tracking control device according to the present invention, FIGS. 6 and 7.
Each of the drawings is a waveform diagram for explaining the operation thereof. (3) is a circuit for forming the tracking error signal S _E , (5) is a circuit for generating the reference pilot signal S ₃₀ , and (33) is a circuit for detecting an oscillation point.

Claims (1)

[Claims] 1. A reproduction pilot signal obtained by recording a recording pilot signal whose frequency changes cyclically in a field unit in a predetermined order sequentially on a recording track and reproducing the recording pilot signal when reproducing the recording track. On the other hand, the tracking position of the reproducing head is controlled by multiplying the reference pilot signal whose frequency is cyclically changed in the above-mentioned predetermined order in field units and detecting the difference frequency component generated in the multiplying force. In the tracking control device, each of the field units is divided into first and second signal sections, and a first reference pilot signal is generated in the predetermined order in the first signal section, and Second
In the signal section, pilot signal generating means adapted to generate a second pilot signal having a phase different from that of the first pilot signal in the predetermined order, and the first pilot signal as the reproduction pilot. Tracking control means for controlling the tracking position of the reproducing head by detecting the frequency component generated in the output multiplied by the signal, and the frequency difference component detected using the second pilot signal have a predetermined lock-in range. And a lock-in error detection means for generating a detection output when the lock-in error detection means is not present, and the phase of the tracking error signal is forcibly changed by 180 ° by the detection output of the lock-in error detection means. Control device.