JP2626050B2 - Rotating head type playback device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head type reproducing apparatus, and particularly to a tracking control apparatus.

[Summary of the Invention]

According to the present invention, in a rotary head type reproducing apparatus in which a rotary head scans an oblique track formed on a tape to reproduce a video signal, a pulse generating circuit for forming a window pulse from a reproduced vertical synchronization signal; A first detection circuit for detecting a first time difference from a predetermined position of the rotary head to a reproduction horizontal synchronization signal gated by a window pulse; and a second detection of a second time difference from a predetermined position of the rotation head to a reproduction vertical synchronization signal. And
A second detection circuit for averaging the detected second time difference; detecting a temporal fluctuation of the reproduced video signal; selecting a first time difference when the fluctuation is small, and averaging when the fluctuation is large; And a circuit for correcting a tracking error in accordance with the selected time difference, so that a tracking error can be generated even when the recorded video signal has a large temporal variation. Can be suppressed.

[Conventional technology]

In a rotary head type VTR, tracking control (also referred to as tracking servo) is required so that the head can correctly scan an oblique track formed during recording during reproduction. As one method of tracking control, a control signal of a frequency of 30 Hz formed from a vertical synchronizing signal separated from a recording video signal in a longitudinal direction of the tape at the time of recording is recorded, and at the time of reproduction, the reproduced control signal and a head signal are recorded. There is known one that controls the tape running speed so that the rotation phase has a predetermined relationship.

In the method using the control signal for tracking, a recording / reproducing head for the control signal is required, and a track extending in the longitudinal direction for the control signal needs to be provided, which increases cost and improves recording density. There was a problem that was hindered.

In an 8 mm VTR, the following four types of frequency f
The pilot signals 1, f2, f3, and f4 are sequentially recorded together with the video signal, and the pilot signals of both adjacent tracks and the target track have a frequency difference of fh (horizontal frequency) and 3fh.

f1 = 6.5fh ≒ 102.5kHz f2 = 7.5fh ≒ 119.0kHz f3 = 10.5fh ≒ 165.2kHz f1 = 9.5fh ≒ 148.7kHz During playback, the crosstalk components from both adjacent tracks and the local pilot signal in the reverse order of the recording The tracking error is detected by comparing the levels of the frequency difference components (fh, 3fh).

As described above, the process of switching the frequency of the pilot signal for each track and comparing the level of the frequency difference component has a problem that the circuit configuration is complicated.

In order to solve the above-mentioned problem, a tracking control method which does not require a special control signal such as a control signal or a pilot signal has been proposed. The synchronization signal timing detection method is one of the tracking control methods. That is, ±± formed from the reproduced vertical synchronization signal
^A specific horizontal synchronization signal is extracted by a window pulse with a width of _1/2 H (H: horizontal cycle), and the time difference between the reference time when the rotary head passes a predetermined position and the time when the specific horizontal synchronization signal is reproduced Is detected, and the direction and amount of the track shift are determined from the time difference.

[Problems to be solved by the invention]

In the synchronization signal timing detection method, there is no problem if the horizontal synchronization signal recorded on the tape does not greatly differ from the NTSC signal standard. However, when shooting with a camera-integrated VTR while riding on a vehicle with large vibration, such as a roller coaster, the temporal fluctuation of the recorded video signal, so-called jitter, becomes considerably large,
The field period of the recorded video signal fluctuates considerably, and the fluctuation of the horizontal synchronizing signal is large. When tracking control is performed by the synchronization signal timing method when reproducing such a tape, there is a problem that the horizontal synchronization signal extracted by the window pulse is not guaranteed to be a specific one, and the tracking control operation is erroneously performed. .

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rotary head type reproducing apparatus in which a malfunction of a tracking control operation is prevented when a temporal variation of a synchronization signal is considerably large.

[Means for solving the problem]

According to the present invention, in a rotary head type reproducing apparatus in which the diagonal tracks formed on the tape 4 are scanned by the rotary heads 1a and 1b to reproduce a video signal, a pulse for forming a window pulse from a reproduced vertical synchronization signal is provided. A generation circuit 13, a first detection circuit 14 for detecting a first time difference from a predetermined position of the rotary heads 1a, 1b to a reproduced horizontal synchronization signal gated by a window pulse, and a first detection circuit 14 for detecting a first time difference between the predetermined positions of the rotary heads 1a, 1b. Second detection circuits 20 and 21 for detecting a second time difference up to the reproduced vertical synchronization signal and averaging the detected second time difference; detecting a temporal fluctuation of the reproduced video signal; Sometimes, the first time difference is selected, and when the fluctuation is large,
Circuits 17 and 23 for selecting the averaged second time difference and means for correcting the tracking error according to the selected time difference are provided.

[Action]

A first time difference between the reproduced horizontal synchronization signal gated by the window pulse and a predetermined rotation phase of the rotary heads 1a and 1b is detected. A tracking error is detected based on the first time difference. When the temporal fluctuation of the reproduced video signal is small, control using the reproduced horizontal synchronization signal is performed.
When the temporal fluctuation is large, a second time difference between the reproduced vertical synchronizing signal and a predetermined rotation phase of the rotary heads 1a and 1b is detected. This second time difference does not exactly correspond to the tracking error due to large temporal fluctuation. Therefore,
Tracking control is performed using the average value of the second time difference.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numerals 1a and 1b denote rotating heads mounted on a drum rotating at a frame frequency (30 Hz) at 180 ° facing intervals. In the rotary heads 1a and 1b, the extending directions of the differential gaps of the rotary heads 1a and 1b are shifted by a predetermined angle, and so-called tilt azimuth recording is performed. Reference numeral 2 denotes a drum motor, and reference numeral 3 denotes a rotation detector that generates a detection signal PG corresponding to the rotation phase of the drum motor 2. Further, the magnetic tape 4 is fed at a predetermined speed in a state where the magnetic tape 4 is wound on the peripheral surface of the drum at a winding angle slightly larger than 180 °. The winding angle of the magnetic tape 4 may be increased as necessary, and the PCM audio signal may be recorded during the overlap period. Reference numeral 5 denotes a capstan motor for feeding the magnetic tape 4, and a rotation detector 6 for generating a detection signal FG corresponding to the rotation frequency and rotation phase of the capstan motor 5 is provided.

The reproduction signals from the rotary heads 1a and 1b are not shown,
The signal is converted into a one-channel reproduction RF signal by the reproduction switching circuit and supplied to the FM demodulation circuit 8 via the reproduction amplifier 7.
The reproduced video signal from the FM demodulation circuit 8 is taken out to a terminal 9 and supplied to a composite synchronization signal separation circuit 10. The composite synchronization signal CSY from the separation circuit 10 is
1 and an AND gate 12. Vertical sync signal separation circuit
11 separates the vertical synchronizing signal VSY. This vertical synchronizing signal VSY is supplied to the pulse generation circuit 13, and the vertical synchronizing signal VSY
A window pulse WN for extracting a predetermined horizontal synchronization signal after the timing of SY is formed. The window pulse WN is supplied to the AND gate 12, and a predetermined horizontal synchronization signal is output from the AND gate 12.

The horizontal synchronization signal extracted by the AND gate 12 is supplied to the time difference detection circuit 14. The output signal of the rotation detector 3 associated with the drum motor 2 is supplied to the amplifier 15, and the amplifier 15 generates a detection signal PG having a phase corresponding to the rotation phase of the drum (rotating heads 1a and 1b). This detection signal PG is supplied to the time difference detection circuit 14, and the detection signal PG and the AND gate 12
The time difference from the horizontal synchronizing signal is detected. This time difference is supplied to one input terminal 18 of the switch circuit 17 via the gain correction circuit 16.

The other input terminal 19 of the switch circuit 17 is supplied with the output signal of the gain correction circuit 22. The separated vertical synchronization signal VSY and the detection signal PG are supplied to the time difference detection circuit 20,
The detected time difference is supplied to the averaging circuit 21. In the averaging circuit 21, the time difference detected by the detection circuit 20 is, for example, 10
An average value of the field is formed, and the output signal of the averaging circuit 21 is supplied to the input terminal 19 of the switch circuit 17 via the gain correction circuit 22.

It is supplied to the detection circuit 23 shaking vertical sync signal VSY, whether swinging of the vertical synchronization signal VSY, for example greater than ± _^1/2 H is detected. Switch circuit with output signal of shake detection circuit 23
17 is controlled, at the time of swinging of the vertical synchronizing signal VSY is ± _^1/2 H less than the input terminal 18 of the switch circuit 17 is selected,
On the other hand, fluctuation of the vertical synchronizing signal VSY is when more than ± _^1/2 H, the input terminal 19 of the switch circuit 17 is selected. The magnitude of the fluctuation of the reproduced video signal may be detected from a horizontal synchronizing signal other than the reproduced vertical synchronizing signal.

The output signal of the switch circuit 17 is a tracking control signal and is supplied to the adding circuit 24. In the adding circuit 24, the speed servo signal of the capstan motor 5 is added. Detection signal generated from the rotation detector 6 and obtained from the amplifier 25
FG is supplied to the period measurement circuit 26. This detection signal FG is
Since the cycle has a frequency proportional to the rotation speed of the capstan motor 5, the cycle measuring circuit 26 forms a speed servo signal corresponding to the speed error component of the capstan motor 5 from the cycle of the detection signal FG. The output signal of the adding circuit 24 is supplied to the capstan motor 5 via the drive amplifier 27. The capstan motor 5 runs the magnetic tape 4 so that a tracking error does not occur at a constant speed between the tracking control signal and the speed servo signal.

The formation of the tracking control signal will be described with reference to FIG. FIG. 2A shows a composite synchronization signal CSYNC separated from the reproduced video signal by the composite synchronization signal separation circuit 10,
FIG. 2B shows the vertical synchronization signal VSYNC separated from the reproduced video signal by the vertical synchronization signal separation circuit 11. Vertical sync signal V
The window pulse WN shown in FIG. 2C is formed by the pulse generation circuit 13 from SYNC. The window pulse WN is ±± with respect to the horizontal synchronizing signal used for detecting the time difference.
^It has a pulse width of _1/2 H. The predetermined horizontal synchronizing signal shown in FIG. 2D gated by the window pulse WN and the detection signal PG (FIG. 2E) having a phase corresponding to the predetermined rotation phase of the drum are supplied to the time difference detection circuit 14, Td in Figure 2
Is detected.

The configurations of the time difference detection circuits 14, 20 and the like surrounded by broken lines in FIG. 1 may be realized by software processing of a microcomputer. FIG. 3 is a flowchart showing processing in the case of microcomputer control.

Shaking of the vertical synchronizing signal VSY at step 31 is detected by software processing, whether this shaking ± _^1/2 H or more is determined (step 32). Shaking at the time of ± _^1/2 H less than a tracking control using a predetermined horizontal synchronizing signal is performed (step 33). On the other hand, it is shaking when more than ± _^1/2 H, the time difference between the vertical sync signal VSY and the detection signal PG is detected (step 34), 10 fields of data for this time difference is averaged (step 35). Drive data for the capstan motor 5 is generated from the averaged data through a gain correction step 36 and a speed system error addition step 37. This drive data is converted into an analog drive signal in step 38 of the D / A conversion process,
At 39, the capstan motor 5 is driven by the analog drive signal.

In the AND gate 12, regarding the tracking control by the horizontal synchronization signal gated by the window pulse WN,
This will be described with reference to FIGS. 4 and 5.

FIG. 4 shows a recording pattern formed on the magnetic tape 4, where Ta indicates a track formed by the rotary head 1a,
Tb indicates a track formed by the rotary head 1b.
In this example, there is no guard band, the distance between the beginning of the tracks Ta and Tb of the two adjacent, which corresponds to the time difference _^1/2 H, orthogonal recording position of the horizontal synchronizing signal and track Are aligned in the direction you want. In FIG. 4, Lr is
This line indicates a predetermined rotation phase of the rotary heads 1a and 1b, that is, a phase of the detection signal PG.

A case will be described in which control is performed so that the rotary head 1a scans correctly on the center track Ta in FIG. When there is no track shift, that is, when the scanning locus S0 in which the center of the track Ta matches the center of the rotary head 1a is drawn, the detection signal PG and the horizontal synchronization signal Ph recorded on the track Ta are drawn.
Is the reference value Tr (see FIG. 5). With respect to a state where there is no track shift, a track shift where the scanning locus at the center of the rotating head is shifted to the upstream side of the tape is defined as positive, while a scanning track at the center of the rotating head is shifted to the downstream side of the tape. Is negative.

As shown by the scanning locus S1 and S2, ± _^1/2 Wp: when there is a track deviation of (Wp track pitch), the time difference (Tr
± ¹ / a ₄ H). Further, as shown by the scanning trajectories S3 and S4, when there is a track deviation of ± Wp, the time difference is (Tr ±
¹ is a / ₂ H). Therefore, the relationship between the track deviation and the detected time difference is as shown in FIG. Tracking control can be performed by controlling the rotation speed of the capstan motor 5 according to the detected time difference.

The time difference between the horizontal synchronization signal and the detection signal PG is
The detection accuracy is not limited to one time for one track, but may be detected a plurality of times to increase the tracking accuracy.

The time difference between the vertical synchronizing signal VSY and the detection signal PG also corresponds to the track shift similarly to the horizontal synchronizing signal. However, when the fluctuation of the vertical synchronizing signal VSY is large due to the jitter at the time of recording, the time difference does not correspond exactly to the track deviation, so that the tracking control is performed by the average value of the period of several fields or tens of fields. .

The present invention can be applied to a pattern other than the recording pattern shown in FIG. 4, for example, a pattern in which the start end of an adjacent track has a shift of 1H. There is no guard band,
In a pattern in which adjacent tracks have a shift of 1H, the width of the window pulse WN is ± 1H.

Further, the tracking control is not limited to controlling the running speed of the tape, but may be a configuration in which the rotary head can be displaced in the height direction by attaching the rotary head to the piezoelectric element.

〔The invention's effect〕

According to the present invention, it is possible to prevent tracking control from being erroneous even when a recorded video signal has a large time-axis variation, such as when shooting is performed in a situation where the camera-integrated VTR is very vibrated. .

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of one embodiment of the present invention, FIG. 3 is a flowchart showing the operation when controlling by a microcomputer, FIG. 4 and 5 are schematic diagrams used for explaining the tracking control. Description of main reference numerals in the drawings 1a, 1b: rotating head, 4: magnetic tape, 5: capstan motor, 10: composite synchronization signal separation circuit, 11: vertical synchronization signal separation circuit, 14, 20: time difference detection circuit, 19 : Switch circuit, 21: averaging circuit.

Claims (1)

(57) [Claims] 1. A rotary head type reproducing apparatus in which a rotary head scans an oblique track formed on a tape to reproduce a video signal, a means for forming a window pulse from a reproduced vertical synchronization signal, First detection means for detecting a first time difference from a predetermined position of the rotary head to a reproduction horizontal synchronization signal gated by the window pulse; and a second detection means from a predetermined position of the rotation head to the reproduction vertical synchronization signal. A second detecting means for detecting a time difference and averaging the detected second time difference; detecting a temporal fluctuation of the reproduced video signal; and selecting the first time difference when the fluctuation is small. Means for selecting the averaged second time difference when the fluctuation is large, and means for correcting a tracking error according to the selected time difference. Rotary head type reproducing apparatus according to claim.