JP2609227B2 - Tracking control circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device applied to a digital video tape recorder or the like for recording and reproducing digital signals, and more particularly, to a tilt recording formed on a magnetic tape. The present invention relates to a tracking control device that performs tracking control by controlling the position of a rotary head in the width direction of a track.

[Summary of the Invention]

The present invention provides a tracking control device that performs tracking control by controlling the position of a rotary head in the width direction of an inclined recording track formed on a magnetic tape. By performing data rearrangement processing so as to eliminate the correlation, the correlation between signals reproduced from adjacent tracks by the rotary head is eliminated, and tracking control can be performed based on the square detection output of the reproduction output by the rotary head. It was made.

[Conventional technology]

In general, a helical scan type magnetic recording / reproducing apparatus such as a video tape recorder which records a video signal using a rotating head records a signal on an inclined recording track on a magnetic tape traced by the rotating head during recording and reproduces the signal. In some cases, reproduction is performed by tracing an inclined recording track on which a signal has been recorded by the rotary head. In the helical scan type magnetic recording / reproducing apparatus, in order to prevent S / N deterioration of a reproduction signal due to a crosstalk component from an adjacent inclined recording track, as shown in FIG. A guard band recording method in which a non-signal area (so-called guard band) 53 is provided between recording tracks 52, or a magnetic tape as shown in FIG.
An azimuth recording method or the like in which the recording azimuth of each of the adjacent inclined recording tracks 56 and 57 on 55 is changed is adopted.

In a helical scan type magnetic recording / reproducing device,
For example, as disclosed in JP-A-57-135583, a rotary head is attached to an electro-mechanical conversion element such as a bimorph plate, and position control is performed in a direction orthogonal to the scanning direction, that is, in a width direction of the inclined recording track. A so-called bimorph head is used to correct a tracking error, that is, a deviation between an inclined recording track on a magnetic tape and a reproduction scanning trajectory during a reproducing operation, and to accurately trace the inclined recording track by the rotating head. There is known a device provided with a tracking control device. Conventionally,
The tracking error is obtained by, for example, sampling the pedestal portion of the reproduction signal every horizontal scanning period (1H) and comparing it with a reference signal level.

Furthermore, in a digital video tape recorder that records and reproduces digital signals, the digitized signal requires about 10 times or more the bandwidth of the original analog signal, so the same amount of information as an analog video tape recorder is recorded on magnetic tape. For recording, it is necessary to reduce both the recording wavelength and the track pitch. In the case of digital recording,
The S / N can be reduced by 20 to 30 dB as compared with analog recording, and the recording wavelength and the track pitch can be reduced in this range. When the guard band recording method or the azimuth recording method is adopted, during a variable speed reproduction operation in which the scanning trajectory of the rotary head straddles a plurality of inclined recording tracks, a portion where a reproduction signal cannot be obtained increases, and the amount of reproduction information is reduced. It is known to be short.

[Problems to be solved by the invention]

By the way, as described above, a conventional tracking control device which samples a pedestal portion of a reproduced signal every one horizontal scanning period (1H) and compares it with a reference signal level to obtain a tracking error signal to control a bimol head. In this case, a tracking error signal is obtained only once every 1H, so that highly accurate tracking control cannot be performed. Therefore, it is extremely difficult to obtain the required tracking accuracy when a conventional tracking control device is applied to a digital video tape recorder that requires both a recording wavelength and a track pitch to be reduced.

Accordingly, the present invention has been made in view of the above-described problems, and has a novel configuration in which a tracking error signal can be obtained for all positions of an inclined recording track on a magnetic tape to enable high-accuracy tracking control. It is an object to provide a tracking control device.

[Means for solving the problem]

In order to achieve the above object, the tracking control device according to the present invention uses the tilted recording track on the magnetic tape on which the digital video signal subjected to the data rearrangement processing so that there is no correlation between adjacent tracks. A rotary head that reproduces a digital video signal, a square detection unit that square-detects a reproduction output signal from the rotary head and outputs a detection output signal corresponding to a tracking error,
Tracking error signal forming means for forming a tracking error signal from the detection output signal; andposition control means for displacing the rotary head in the width direction of the inclined recording track based on the tracking error signal. I have.

[Action]

In the tracking control device according to the present invention, the digital signal is reproduced from the inclined recording track on the magnetic tape on which the digital signal subjected to the data rearrangement processing is recorded so that the correlation between adjacent tracks is eliminated by a rotating head. Thus, a reproduced signal having no correlation with a signal reproduced from an adjacent track is obtained. A detection output corresponding to a tracking error is obtained by performing square detection of a reproduction output from the rotating head, and a tracking error signal is obtained from the detected output. To perform tracking control of the rotary head.

〔Example〕

Hereinafter, an embodiment of a tracking control device according to the present invention will be described in detail with reference to the drawings.

In the block diagram of FIG. 1 showing the configuration of an embodiment of a digital video tape recorder to which the present invention is applied, a magnetic tape 1 is spirally wound around an outer periphery of a rotary head drum 2 at an angle range of about 360 °. The capstan 4 is driven at a predetermined speed by a capstan 4 driven by a capstan motor 3 and a pinch roller 5. The rotary head drum 2 is rotated at a constant speed by a drum motor (not shown).

The rotary head drum 2 is provided with a video head 7 cantilevered by a bimorph plate 6 in which two piezo ceramic plates are joined. The bimorph plate 6
In the recording operation mode, the video head 7 is fixed at a predetermined height position, and in the reproduction operation mode, the video head 7 is accurately traced on a target track on the magnetic tape 1 by a tracking servo system 30 described later. Is displaced in the track width direction. On the surface of the bimorph plate 6, a strain gauge 8 such as a resistance strain gauge for detecting the amount of deflection of the bimorph plate 6, that is, the amount of displacement of the video head 7 in the track width direction, is attached.

The video head 7 is selectively connected to a recording processing system 10 and a reproduction processing system 20 via a switch circuit 9.

The recording processing system 10 includes an analog / digital (A / D) conversion circuit 12 for digitizing an analog video signal supplied to a signal input terminal 11 and a digital video signal obtained by the A / D conversion circuit 12. A scramble processing circuit 13 for rearranging data, a recording amplifier 14 for supplying the scrambled digital video data as a recording signal to the video head 7 through the switch circuit 9 and the like are provided. .

In this embodiment, in the recording operation mode, the video head 7 sequentially scans each inclined recording track TR on the magnetic tape 1 without providing a guard band between the tracks as shown in FIG. The recording signal supplied from the recording processing system 10 via the switch circuit 9 performs non-azimuth recording on each of the inclined recording tracks TR.

Here, since continuous video signals are very similar, there are strong line correlations and field correlations. In this embodiment, the scramble processing circuit 13 of the recording processing system arranges data so that recording signals recorded non-azimuthally on each inclined recording track TR on the magnetic tape 1, ie, digital video data, have no correlation between adjacent tracks. The replacement process is performed.

Further, the reproduction processing system 20 performs a data rearrangement process corresponding to the data rearrangement process corresponding to the data rearrangement process performed by the reproduction amplifier 21 that amplifies the reproduction output from the video head 7 and the scramble processing circuit 13 of the recording processing system 10. A scramble processing circuit 22 and a digital / analog (D / A) conversion circuit 23 for converting a reproduced digital video signal obtained by the descramble processing circuit 22 into an analog signal and outputting the analog signal to a signal output terminal 24; I have.

In this embodiment, the reproduction processing system 20 traces each inclined recording track TR of the magnetic tape 1 on which the digital video data subjected to the data rearrangement processing as described above is recorded by the video head 7. Digital video data obtained as a reproduction output is supplied via the switch circuit 9 in the reproduction operation mode, and the reproduction output, that is, the digital data, corresponds to the data rearrangement processing by the scramble processing circuit 13 of the recording processing system 10 described above. By performing the data rearrangement processing in the descrambling processing circuit 22, the order of the digital video data is restored, and the analog video signal is reproduced in the D / A conversion circuit 23, thereby reproducing the reproduced analog video signal. Output from the signal output terminal 24.

Further, in this embodiment, in the reproduction operation mode, the reproduction output obtained by the video head 7 is output from the reproduction processing system.
The amplified signal is amplified by the regenerative amplifier 21 and the square detection circuit 31 and the address data generation circuit 34 of the tracking servo system 30 are amplified.
It is supplied to.

The square detection circuit 31 of the tracking servo system 30 supplies the detection output to a multiplier 33 via a low-pass filter (LPF) 32. Further, the multiplier 33 is supplied with a signal indicating the amount of displacement of the video head 7 from a strain gauge 8 provided on the bimorph plate 6.
The multiplier 33 multiplies the square detection output signal supplied through the LPF 32 by the displacement detection signal supplied from the strain gauge 8, and outputs the multiplied output to the first signal.
Is supplied to the adder 34.

Further, the address data generating circuit 34 of the tracking servo system 30 operates during the reproducing operation mode.
Forms address data of digital video data obtained as a reproduction output by the CPU, supplies a clock pulse of the data to a tape speed detection circuit 35, and outputs a synchronization pulse of the digital video data to a reproduction phase detection circuit
Supply to 37. The above tape speed detection circuit 35,
From the period of the supplied clock pulse, the magnetic tape 1
And outputs the detected output to the ramp voltage generator 36 and the jump discriminating circuit 39. The ramp voltage generator 36 outputs a ramp voltage for displacing the video head 7 in accordance with the tape speed of the magnetic tape 1 indicated by the detection output of the tape speed detection circuit 35 to the first adder. Supply to 41. Further, the reproduction phase detection circuit 37 compares the phase of the phase reference signal Vref supplied to the reference signal input terminal 38 with the synchronization pulse supplied from the address data generation circuit 34, thereby obtaining the reproduction phase of the digital video data. And the detection output is supplied to the jump determination circuit 39. Further, in the variable speed reproduction operation mode, the jump discriminating circuit 39 controls the tape speed of the magnetic tape 1 indicated by the detection output of the tape speed detecting circuit 35 and the reproducing phase detecting circuit 37.
The jump data is supplied to the jump voltage generator 40 at a predetermined timing according to the reproduction phase of the digital video data indicated by the detection output of. The jump voltage generator 40 supplies a jump voltage corresponding to the jump data to the first adder 41.

Further, the first adder 41 adds the multiplied output of the multiplier 33 to the ramp voltage and the jump voltage, and supplies the added output to the second adder 43 via the integrator 42. I have. The second adder 43 is supplied with a sine wave excitation signal (so-called wobbling signal) having a frequency of, for example, 720 Hz from the oscillator 44, and is provided with the wobbling signal as an integrated output of the integrator 42. The control signal is added, and the output is supplied to the bimorph plate 6 as a drive signal.

In the embodiment having the above-described configuration, in the reproducing operation mode, for example, as shown by a broken line in FIG. 2, the video head 7 is moved to two adjacent inclined recording tracks TRx and TRy on the magnetic tape 1. Assuming you are straddling and scanning,
From the video head 7, one inclined recording track TR
A reproduction obtained by adding the reproduction output (X) of the reproduction level corresponding to the width x sliding on x and the reproduction output (Y) of the reproduction level corresponding to the width y sliding on the other inclined recording track TRy. An output (X + Y) is obtained.

In the tracking servo system 30 to which the reproduction output (X + Y) is supplied, the square detection circuit 31 obtains the square detection output (X + Y) ² of the reproduction output (X + Y),
By averaging the squared detection output (X + Y) ² in the LPF 32, Sig = [((X + Y) ² ] = [X ² + 2ρxy + Y ² ] 1] The signal Sig is obtained.

Here, ρ is a correlation coefficient between the reproduced outputs (X) and (Y). [...] indicates averaging.

In this embodiment, as described above, a data rearrangement process is performed by the scramble processing circuit 13 of the recording processing system 10, and a recording signal recorded on each inclined recording track TR on the magnetic tape 1, ie, digital video data. Since the correlation between adjacent tracks is eliminated, the correlation coefficient ρ of each of the reproduced outputs (X) and (Y) is substantially zero.

Therefore, the output signal Sig of the LPF 32 is expressed by the following equation: Sig = [X ² ] + [Y ² ], and two adjacent inclined recording tracks TRx on the magnetic tape 1 being scanned by the video head 7. , TRy, and is a signal indicating the sum of the respective envelopes of the reproduction outputs (X) and (Y).

Therefore, when the tracking error amount as a <1 rewrite the first equation, Sig = [{(1-a) X + aY} 2 ] = ^{[(1-a) 2 X 2} + 2a (1-a) ρXY + a 2 Y ² ] = (1-a) ² [X ² ] + a ² [Y ² ]

The output signal Sig of the LPF 32 represented by the third equation
Is Sig = [X ² ], when the tracking error amount is a = 0.
When a = 1, Sig = [Y ² ]. Normalized by [X ² ] and [Y ² ] and differentiated by the tracking error amount a, dSig / da = {(1-a) ² + a ² } / da = (1−2a + 2a ² ) / da = −2 + 4a, and dSig / da = 0 when a = 0.5, so that a curve with a = 0.5 as the minimum value with respect to the tracking error amount is drawn. Become.

In this embodiment, the reproduction output obtained by the video head 7 when the bimorph plate 6 is excited by the wobbling signal output from the oscillator 44 includes an AM component due to the wobbling signal. The multiplier 33 multiplies the displacement detection signal corresponding to the wobbling signal by the strain gauge 8 provided on the bimorph plate 6 and the output signal Sig of the LPF 32 in the multiplier 33 to perform so-called synchronous detection. A signal is formed, and the tracking error signal is supplied to the second signal adder 43 via the integrator 42 to correct the tracking error. The tracking error signal formed based on the squared detection output of the reproduction output can be obtained over the entire range of each of the inclined recording tracks TR on the magnetic tape 1, and all the positions of the respective inclined recording tracks TR can be obtained. , Highly accurate tracking control can be performed.

In the variable speed reproduction operation mode in which the magnetic tape 1 is run at a tape speed different from the tape speed in the recording operation mode to perform the reproduction operation, one tape is set in accordance with the ratio between the recording operation track pitch and the reproduction track pitch. In this case, the track is repeatedly traced or several tracks are skipped. For example, in the case of performing the playback at 2.25 times speed, the scanning locus of the video head 6 is the fourth track.
As shown by the dashed line in the figure, 1.2 for TR ₁ , TR ₄ , TR ₆ ...
It is necessary to correct this tilt error, and to increase the reproduction track pitch every five traces in order to correct a fraction (0.25) of the track pitch ratio. is there. Therefore, in this embodiment, the gradient voltage generator 36 applies a gradient voltage for displacing the video head 6 by 1.25 pitches during one track scanning period, and the jump voltage generator 36
A jump voltage is applied every five traces by 40, and the bimorph plate 6 is driven by a drive voltage as shown in FIG. 4 to perform 2.25 times speed reproduction.

〔The invention's effect〕

As is apparent from the above description of the embodiment, in the tracking control device according to the present invention, from the inclined recording track on the magnetic tape on which the digital signal subjected to the data rearrangement processing so that there is no correlation between adjacent tracks is recorded. By reproducing the digital signal with a rotating head,
A reproduced signal having no correlation with a signal reproduced from an adjacent track is obtained, a detection output corresponding to a tracking error is obtained by square detection of a reproduction output from the rotary head, and a tracking error signal is formed from the detected output. Thus, since the tracking control of the rotary head is performed, a tracking error signal is formed for all the positions of the inclined recording tracks on the magnetic tape, and the tracking control can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a digital video tape recorder to which the present invention is applied, and FIG. 2 is a schematic diagram showing an inclined recording track on a magnetic tape used for explaining the operation of this embodiment. FIG. 3 is a schematic diagram showing a trace state when a 2.25 × speed reproduction operation is performed in the above embodiment, and FIG. 4 is a waveform diagram showing a drive voltage supplied to the bimorph plate. FIG. 5 and FIG. 6 are schematic diagrams showing recording formats according to the conventionally known guard band recording system and azimuth recording system. DESCRIPTION OF SYMBOLS 1 ... Magnetic tape 2 ... Rotating head drum 6 ... Bimorph plate 7 ... Video head 8 ... Strain gauge 9 ... Switch circuit 10 ... Recording processing system 11 ... Signal input terminal 12 ... A / D conversion Circuit 13 Scramble processing circuit 20 Reproduction processing system 22 De-scramble processing circuit 23 D / A conversion circuit 30 Tracking servo system 31 Square detection circuit 32 LPF 33 Multiplication circuit 41, 43 …… Adder 42 …… Integrator 44 …… Oscillator

Claims (1)

(57) [Claims] 1. A rotary head for reproducing a digital video signal from an inclined recording track on a magnetic tape on which a digital video signal on which data rearrangement processing has been performed so that there is no correlation between adjacent tracks is provided. Squared detection of the reproduced output signal according to the above, and a squared detection means for outputting a detection output signal corresponding to the tracking error; a tracking error signal forming means for forming a tracking error signal from the detection output signal; and A displacement control means for displacing the rotary head in the width direction of the inclined recording track.