JPH02282964A - Rotary head type reproducing device - Google Patents

Abstract

PURPOSE:To securely perform a tracking control even when time base fluctuation is large by detecting a time difference between a regenerative horizontal synchronizing signal gated with a window pulse and a prescribed rotary phase of a rotary head, as a 2nd time difference and a 1st time difference in accordance with the size of time base fluctuation of a regenerative video signal, and using this for the tracking control. CONSTITUTION:The horizontal synchronizing signal abstracted by the AND gate 12 is supplied to a time difference detecting circuit 14, and an output of a rotation detecting amt. 3 relative to a drum motor 2 is supplied to an amplifier 15. A detecting signal PG having a phase corresponding to the rotary phase of rotary heads 1a and 1b of a drum is generated from the amplifier 15, and this is given to the circuit 14 to detect a time difference between the signal PG and the horizontal signal from the gate 12, and then this time difference is supplied via a gain correction circuit 16 to one input terminal 18 of a switch 17. The other input terminal 19 is supplied with an output of a gain correction circuit 22, and a separated vertical synchronizing signal VSY and the detecting signal PG are given to a time difference detecting circuit 20, and this output is given to the circuit 17 to control a motor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary head type reproducing device, and particularly to a tracking control device.

(Summary of the Invention) In the present invention, in a rotary head type reproducing device in which a rotary head scans diagonal tracks formed on a tape to reproduce a video signal, a window pulse is formed from a reproduction vertical synchronization signal. a first detection circuit for detecting a first time difference from a predetermined position on the rotary head to a reproduced horizontal synchronization signal gated with a window pulse; a second detection circuit that detects a second time difference and averages the detected second time difference; a second detection circuit that detects a temporal fluctuation of the reproduced video signal and selects a first time difference when the fluctuation is small; When the fluctuation is large, a circuit for selecting the averaged second time difference and a circuit for correcting the tracking deviation according to the selected time difference are provided, and when the recorded video signal has many temporal fluctuations. It is also possible to suppress the occurrence of tracking errors.

[Conventional technology]

A rotary head type VTR requires tracking control (also referred to as tracking servo) to ensure that the head correctly scans diagonal tracks formed during recording during reproduction. One method of tracking control is to record a control signal with a frequency of 30 Hz formed from a vertical synchronization signal separated from the recorded video signal in the longitudinal direction of the tape during recording, and during playback, the reproduced control signal and the head It is known to control the tape running speed so that the rotational phase has a predetermined relationship.

This method of using control signals for trunking requires a recording/reproducing head for the control signals, and also requires the provision of longitudinally extending tracks for the control signals, which increases cost and reduces recording density. There were problems that hindered improvement.

In addition, the 8mm VTR has four types of frequencies fl, f2, etc. as shown below. f3. The pilot signal of f4 is sequentially recorded together with the video signal, so that the pilot signals of both adjacent tracks and the pilot signal of the track of interest have a frequency difference of rh (horizontal frequency) and 3fh.

fl=6.5fh '1102.5k)lzf 2=
7. 5 fh 'if 19. 0kHzf 3=
10.5 fh #165.2kHzfl=9.5fh
! :1148.7kHz During reproduction, a tracking error is detected by comparing the levels of the frequency difference components (fh, 3fh) between the crosstalk components from both adjacent tracks and the local pilot signal in the reverse order from the recording time.

As described above, the process of switching the frequency of the pilot signal for each track and comparing the levels of frequency difference components has the problem of complicating the circuit configuration.

In order to solve the above-mentioned problems, a tracking control method that does not require special signals for control such as a control signal or a pilot signal has been used. The synchronization signal timing detection method is one of these tracking control methods. That is, the output signal formed from the reproduced vertical synchronization signal
A specific horizontal synchronizing signal is extracted using a window pulse with a width of H (H: horizontal circumference FJJ), and the time difference between the reference time when the rotating head passes a predetermined position and the time when the specific horizontal synchronizing signal is reproduced is detected. The direction and amount of track deviation are determined from this time difference.

[Problem to be solved by the invention]

With the synchronization signal timing detection method, there is no problem if the horizontal synchronization signal recorded on the tape is not significantly different from the signal standard of the NTSC system. When shooting with a body type VTR, the temporal fluctuations of the recorded video signal, so-called jitter, become quite large, the field period of the recorded video signal fluctuates considerably, and the fluctuation of the horizontal synchronization signal also becomes large. If tracking control is performed using the synchronization signal timing method when playing back a tape, it is not guaranteed that the horizontal synchronization signal extracted by the window pulse is a specific one, leading to errors in the tracking control operation.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a rotary head type reproducing apparatus that can prevent malfunctions in tracking control operations even when the temporal fluctuation of a synchronization signal is considerably large.

(Means for Solving the Problems) In the present invention, in a rotary head type reproducing device in which the rotary heads la and lb scan diagonal tracks formed on a tape 4 to reproduce video signals, the reproduction vertical a pulse generation circuit 13 that forms a window pulse from a synchronization signal; a first detection circuit 14 that detects a first time difference from a predetermined position of the rotary heads la, Ib to a reproduction horizontal synchronization signal gated by the window pulse; Rotating head la, lb
a second detection circuit 20-21 that detects a second time difference from a predetermined position of the playback video signal to the playback vertical synchronization signal and averages the detected second time difference; , a circuit 17.23 that selects a first time difference when the fluctuation is small and selects an averaged second time difference when the fluctuation is large; and means for correcting tracking deviation according to the selected time difference. is provided.

[Effect]

A first time difference between the window pulse gated reproduction horizontal synchronization signal and a predetermined rotational phase of the rotary head 1a, Ib is detected. A tracking error is detected by this first time difference. When the temporal fluctuation of the reproduced video No. 73 is small, control is performed using the reproduced horizontal synchronizing signal. When the temporal fluctuation is large, the reproduced vertical synchronizing signal and the predetermined rotational phase of the rotating healds la and lb are controlled. A second time difference is detected. This second time difference does not correspond accurately to the tracking error due to large temporal fluctuations.
Therefore, tracking control is performed using the average value of the second time difference.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. In FIG. 1, la and 1b indicate rotary heads that are attached to a drum rotating at a frame frequency (30 Hz) at an opposing interval of 180°.0-rotary heads 1a and 1b are such that the direction in which their differential gaps extend is There is a deviation of a predetermined angle, and so-called inclined azimuth recording is performed. 2 indicates a drum motor, 3 indicates a rotation detector that generates a detection signal PG corresponding to the rotational phase of the drum motor 2, and a magnetic tape is wrapped around the circumference of the drum at a winding angle slightly larger than 180°. The magnetic tape 4 is fed at a predetermined speed with the magnetic tape 4 wound around the magnetic tape 4. The winding angle of the magnetic tape 4 may be increased as necessary so that the PCM audio signal is recorded during the overlap period.

Reference numeral 5 indicates a capstan motor for feeding the magnetic tape 4, and a rotation detector 6 is provided for generating a detection signal FC corresponding to the rotational frequency and rotational phase of the capstan motor 5.

The reproduction signals from the rotary heads 1a and 1b are converted into a one-channel reproduction RF signal by a reproduction switching circuit (not shown), and are supplied to an FM demodulation circuit 8 via a reproduction amplifier 7. The reproduced video signal from the FM demodulation circuit 8 is taken out to the terminal 9, and the composite synchronization signal C3Y from the zero separation circuit 10 is supplied to the composite synchronization signal separation circuit 10. The composite synchronization signal C3Y is supplied to the vertical synchronization signal separation circuit 11 and the AND gate 12. be done.

A vertical synchronizing signal (SY) is separated by a vertical synchronizing signal separation circuit 11. This vertical synchronizing signal VSY is supplied to a pulse generating circuit 13, which forms a window pulse WN for extracting a predetermined horizontal synchronizing signal after the timing of the vertical synchronizing signal SY.

This window pulse WN is supplied to an AND gate 12, and a predetermined horizontal synchronizing signal is output from the AND gate 12.

The horizontal synchronization signal extracted by the AND gate 12 is supplied to a 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 PC having a phase corresponding to the rotation phase of the drum (rotary heads 1a, lb). This detection signal PG is supplied to a time difference detection circuit 14, and the time difference between the detection signal PC and the horizontal synchronization signal from the AND gate 12 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 synchronizing signal SY and detection signal PG are supplied to a time difference detection circuit 20, and the detected time difference is supplied to an averaging circuit 21. In the averaging circuit 21, an average value of, for example, 10 fields of the time differences detected by the detection circuit 20 is formed, and the output signal of this averaging circuit 21 is supplied to the input terminal 19 of the switch circuit 17 via the gain correction circuit 22. be done.

The vertical synchronizing signal VSY is supplied to a fluctuation detection circuit 23, and it is detected whether the fluctuation of the vertical synchronizing signal VSY exceeds, for example, 10%. The switch circuit 17 is controlled by the output signal of the fluctuation detection circuit 23, and when the fluctuation of the vertical synchronization signal SY is smaller than ±l, the input terminal 1 of the switch circuit 17 is
8 is selected, and on the other hand, the vertical synchronization signal ■SY fluctuation is ±η
When the voltage exceeds H, the input terminal 19 of the switch circuit 17
is selected. The magnitude of fluctuation in the reproduced video signal may be detected from a horizontal synchronization signal other than the reproduction vertical synchronization signal.

The output signal of the switch circuit 17 is a tracking control signal and is supplied to the adder circuit 24. In the addition circuit 24, a detection signal FG generated from the nine rotation detector 6 to which the speed servo signal of the capstan motor 5 is added and obtained from the amplifier 25 is supplied to the period measurement circuit 26. Since this detection signal FG has a frequency proportional to the rotational speed of the capstan motor 5, the period measurement circuit 26 generates a speed servo signal corresponding to the speed error component of the capstan motor 5 from the period of the detection signal FG. is formed. The output signal of the adder circuit 24 is supplied to the capstan motor 5 via a drive amplifier 27. The capstan motor 5 runs the magnetic tape 4 at a constant speed using a tracking control signal and a speed servo signal so as not to cause a tracking error.

Formation of the tracking control signal will be explained with reference to FIG. 2A shows the composite synchronization signal C3YNC separated from the reproduced video signal by the composite synchronization signal separation circuit 10, and FIG. 2B shows the vertical synchronization signal C3YNC separated from the reproduction video signal by the vertical synchronization signal separation circuit 11. The window pulse WN shown in FIG. 2C is generated by the pulse generating circuit I3 from the vertical synchronizing signal 5YNC indicating VSYNC. This window pulse WN has a pulse width of 10'AH with respect to the horizontal synchronizing signal used for detecting the time difference. A predetermined horizontal synchronizing signal shown in the second diagram gated by the window pulse WN and a detection signal PG (FIG. 2 E) having a phase corresponding to a predetermined rotational phase of the drum are supplied to the time difference detection circuit 14, and the second A time difference indicated by Td in the figure is detected.

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

In step 31, the fluctuation of the vertical synchronization signal SY is detected by software processing, and it is determined whether this fluctuation is greater than or equal to 0%H (step 32).When the fluctuation is smaller than %H, a predetermined horizontal synchronization signal Tracking control using Yuregashi+A is executed (step 33).
When it is H or more, the time difference between the vertical synchronizing signal VSY and the detection signal PC is detected (step 34), and 10 fields of data of this time difference are averaged (step 35).
), the averaged data is passed through a gain correction step 36 and a speed system error addition step 37 to generate drive data for the capstan motor 5. This drive data is converted into an analog drive signal in step 38 of the D/A conversion process, and the capstan motor 5 is driven with the analog drive signal in step 39.

In AND game 1-12, tracking control using a horizontal synchronizing signal gated by window pulse WN 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 a rotating radial drive 1a, and Tb indicates a track formed by a rotating rad lb. In this example, there is no guard band, the distance between the starting ends of two adjacent tracks Ta and Tb corresponds to a time difference of %H, and the recording position of the horizontal synchronization signal is in the direction perpendicular to the tracks. are lined up. In FIG. 4, L is the predetermined rotational phase of the rotating heads la and lb;
That is, it is a line for indicating the phase of the detection signal PC.

The head 1a rotates on the center track Ta in FIG.
A case will be explained in which control is performed so that the image scans correctly. When there is no track deviation, that is, when a scanning trajectory SO is drawn in which the center of the track Ta and the center of the rotary head 1a coincide, the time difference between the detection signal PC and the horizontal synchronization signal Ph recorded on the track Ta is the reference value. (ITr (see Figure 5)).In contrast to a state where there is no track deviation, a track deviation in which the scanning locus at the center of the rotating head deviates to the upstream side of the tape is considered positive; A trunk shift in a state where the scanning locus shifts to the downstream side of the tape is considered negative.

As shown by the scanning trajectories S1 and S2, ± each Wp (Wp
: ) rack pitch), the time difference is (T r f Vs H). Also, as shown in the scanning trajectories S3 and S4, when there is a track deviation of ±Wp, the time difference is (Tr: ). 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 rotational speed of the capstan motor 5 according to the detected time difference.

Note that the time difference between the horizontal synchronization signal and the detection signal PC is
The tracking accuracy may be increased by detecting not only one time but multiple times on one track.

Similarly to the horizontal synchronization signal, the time difference between the vertical synchronization signal VSY and the detection signal PC also corresponds to the tracking error. However, when the vertical synchronization signal VSY has large fluctuations due to jitter during recording, the time difference does not correspond accurately to the track deviation, so tracking control is performed using an average value over a period of several fields or more than ten fields. .

The present invention can also be applied to patterns other than the recording pattern shown in FIG. 4, such as patterns in which the starting ends of adjacent tracks are offset by IH.

In a pattern where there is no guard band and adjacent tracks have an IH deviation, the width of the window pulse WN is ±IH.
It is said that

Furthermore, tracking control is not limited to controlling the running speed of the tape, but can also be achieved by attaching a rotary head to a piezoelectric element so that it can be displaced in the height direction.

〔Effect of the invention〕

According to this invention, it is possible to prevent errors in tracking control even when the recorded video signal has large fluctuations in the time axis, such as when shooting with a camera-integrated VTR in a situation where there is a lot of vibration. .

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a timing chart for explaining the operation of an embodiment of the invention, and Fig. 3 is a flowchart showing the operation when controlled by a microcomputer. , FIG. 4, and FIG. 5 are route maps used to explain tracking control. Explanation of main symbols in the drawings la, Ib: 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. Agent: Tadashi Sugiura, Patent Attorney: Flowchart for microcomputer control Figure 3 Figure 5 Track, limb, B, difference

Claims (1)

[Scope of Claim] A rotary head type reproducing device in which a rotary head scans diagonal tracks formed on a tape to reproduce a video signal, comprising means for forming a window pulse from a reproduced vertical synchronizing signal; a first detection means for detecting a first time difference from a predetermined position of the rotary head to a reproduced horizontal synchronization signal gated with the window pulse; and a second time difference from a predetermined position of the rotary head to the reproduced vertical synchronization signal gated with the window pulse a second detection means that detects a time difference between the two and averages the detected second time difference;
and means for selecting the averaged second time difference when the fluctuation is large; and means for correcting the tracking deviation according to the selected time difference. Rotating head type playback device.