JP2590223B2 - Playback device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus, and more particularly, to an apparatus for simultaneously reproducing a plurality of systems of signals.

[Prior Art] Conventionally, a helical scan type magnetic recording / reproducing device is known as one of such devices. The tracking method of this helical scan type magnetic recording / reproducing device is CTL which records / reproduces a control signal with a fixed head.
An area division pilot scheme is well known. Also, a method called index tracking, which detects a tracking error by comparing the phase detection signal of a rotary head with the phase of a horizontal synchronization signal in a reproduction signal, has been announced (Technical Report of the Institute of Television Engineers of Japan, Vo.
l.11, No.14, pp13-18, VR8.26 (Aug.1987)).

[Problem to be Solved by the Invention] However, in each of the above-described conventional examples,
There were the following disadvantages.

In the CTL method, i) a dedicated CTL (control) track and CTL head are required.

ii) Since the sampling rate is low (two tracks / one sample), the response is poor.

iii) Adjustment of the fixed head position (X-ray) is required.

In the pilot signal superimposition method, i) frequency multiplexing is disadvantageous for digital recording that is easily affected by low frequencies.

ii) Low-level recording to reduce interference with the main signal,
S / N deteriorates.

In the area division pilot method, i) since a dedicated area is required, the effective area of the main signal is reduced.

ii) The sampling rate is low (1-2 samples per track). More areas are needed to increase the number of samples.

In the index tracking method, i) since the phase detection signal of the rotary head is used as a reference signal, the actual sampling rate is limited by this. Further, in order to obtain a rate of several samples per track, a highly accurate phase detecting means is required.

ii) It is affected by jitter during one rotation of the drum.

iii) Since the main signal is used, an error signal cannot be obtained unless the output is higher than a certain level.

As described above, there is a problem in responsiveness, accuracy, etc. in each system,
The disadvantage was that it was difficult to obtain sufficient performance.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reproducing apparatus capable of performing high-accuracy and high-speed response tracking control in view of the above points.

[Means for Solving the Problems] A reproducing apparatus according to the present invention comprises a plurality of heads for reproducing a plurality of systems of signals recorded in parallel on a recording medium, and an output of a certain level or more from each of the heads. Detection means for detecting whether or not each of the heads has been detected; phase comparison means for detecting a phase difference between signals having a predetermined frequency component among signals reproduced from each of the heads; And control means for performing tracking control of the head in response to the output of the phase comparison means only when it is detected that an output of a predetermined level or more is obtained from the control signal.

Another reproducing apparatus according to the present invention includes a plurality of heads for reproducing a plurality of signals recorded in parallel on a recording medium,
A plurality of frequency dividing means for dividing a signal having a predetermined frequency component among signals reproduced from each of the heads; and a phase comparing means for detecting a phase difference between outputs of the plurality of frequency dividing means. And control means for performing tracking control of the head in response to the output of the phase comparison means.

[Operation] In the reproducing apparatus according to the present invention, a constant frequency component (for example, a horizontal synchronizing signal, a data clock, an index signal) in at least two parallel signals is obtained as it is or by dividing the frequency and then comparing the phases. The tracking control is performed by the error signal.

EXAMPLES Hereinafter, the present invention will be described in detail based on examples.

Embodiment 1 FIGS. 1 to 5 show a color image recording / reproducing apparatus according to a first embodiment to which the present invention is applied. Here, FIG. 1 is a block diagram showing the entire embodiment, FIG. 2 is a top view showing the arrangement of the rotary heads included in the embodiment, FIG. 3 is a track pattern diagram formed on a magnetic tape, FIG. 4 and FIG. 5 are a pattern diagram and a waveform diagram, respectively, for explaining the generation of a tracking error signal. 1 in these figures is a rotating drum, four heads Y1, Y2, C1, C2 is mounted, is rotated at a predetermined rotational speed V _H. The magnetic tape 2 is attached rotary drum 1 wound over about 180 °, delivered at a predetermined speed V _T by capstan 3 and pinch roller 4. Thus, an inclined track is formed on the tape 2 as shown in FIG. Here, heads Y1, Y2 and C1, C2 have different azimuth angles ±
By giving θ, a high-density recording method without a guard band is obtained.

Next, the operation of signal processing in this embodiment will be described with reference to FIG.

At the time of recording, in this embodiment, a luminance signal Y, a wideband color signal _CW , a narrowband color signal _CN, and a synchronization signal (horizontal and vertical) are separately input as input signals. And Y
For the signal, add a sync signal and perform FM modulation as it is,
Recording on the magnetic tape 2 is performed by the heads Y1 and Y2. For the C _W signal and C _N signal, the time axis is compressed to 1/2 by using a memory or CCD, etc., and then converted to one C signal by time axis multiplexing to add a synchronization signal and a delay circuit At 30, the signal is delayed by the delay time A, and then FM modulation is performed.

Here, in the time axis compression processing section 28, a time delay of more than 1/2 horizontal period occurs, so that a time difference occurs between the Y signal and the C signal at the output time of the processing section 28. On the other hand, as shown in FIG. 2, the heads Y1 and C1 and the head Y2
Although C2 and C2 are arranged close to each other, a physical space is required to a certain degree or more in order to secure the mechanical strength and accuracy and not to increase the crosstalk, thereby causing a mounting error. Therefore, it is necessary to adjust the recording timing of the Y signal and the C signal in order to always keep the write position of the synchronization signal in each track in a predetermined relationship. Therefore, in the present embodiment, the recording position of the synchronization signal of each track is set in a predetermined positional relationship by providing the delay circuit 30 in the processing system of the C signal.

Next, the operation at the time of reproduction will be described. First, two heads Y
The reproduced FM signal obtained from Y1 and Y2 is subjected to FM demodulation, then passes through a delay circuit 40 having a delay time A, is synchronously separated, and is output as a Y signal. On the other hand, the reproduced FM signals obtained from the two heads C1 and C2 are subjected to FM demodulation, separated into synchronization, and the delay amount B
It is sent to the time-base decompression and separation unit 52 via a delay circuit 50 having, are separated and output to the C _W signal and the C _N signal.

The synchronization signals separated from the Y-system and C-system circuits are input to a phase comparator 56, and a tracking error signal S56 representing the phase difference is sent to a delay circuit 50 of a capstan servo circuit 58.

The captan servo circuit 58 performs a tracking control operation based on the error signal S56, and the delay circuit 50 operates to change the amount of delay so that the timings of the Y signal and the C signal match.

Next, the principle by which a tracking error signal is obtained by the two synchronization signals described above will be described with reference to FIG.
Now, the tape feed direction (V _T direction indicated by the arrow) consider the case where deviation tracking by Δ perpendicular to the track in the opposite direction. In this case, the head Y1 having the azimuth in the clockwise direction with respect to the traveling direction of the head (the _VH direction indicated by the arrow) leads the head by t = Δtanθ, and the head C1 having the opposite azimuth delays the track by t. To reproduce the signal. That is, there is a time difference with respect to the tracking error Δ by T = 2t / V _H = 2Δtan θ / V _H (1). For example, Δ = 1 μm, θ
T = 10 ゜, V _H = 6 m / s, T is about 0.06 μsec. Therefore, when the frequency of the horizontal sync signal is 15.75 kHz,
This corresponds to a phase difference of 0.1%, indicating that the detection sensitivity is sufficiently high.

FIG. 5 shows signal waveforms when the phase comparison operation described with reference to FIG. 4 is performed using a sample and hold circuit. Here, one of the synchronization signals obtained from the two synchronization separation circuits 42 and 48 is used as a reference signal (A), and a sawtooth wave (C) is generated therefrom. The sawtooth wave is sampled by the other synchronizing signal (b), and this is held until the next sampling to obtain a tracking error signal as shown in (d). Note that the broken line in the figure indicates the case where the phase difference has changed.

As described above, the tracking error signal S56 can be obtained by inputting the two synchronization signals to the phase comparison circuit 56. However, when the track deviation is large, a sufficient output signal cannot be obtained. Each head Y1, Y2, C
The output detection circuit 54 confirms that an output of a certain level or more has been obtained from 1, C2, and only in that case, the tracking control is performed by the output of the phase comparator 56 (tracking error signal S56).

In the above-described embodiment, if the positions of the synchronization signals of the two tracks have a predetermined relationship on the tape, the tape is compatible. In addition, in order to absorb errors such as the mounting phase of the head, in this embodiment, compatibility adjustment is performed by adjusting the delay amount of the delay circuit 40 using a reference tape in which a standard tape pattern is recorded in advance. That is, when the interval between the heads Y1 and C1 is longer than a predetermined value, the reproduction of the reference tape is delayed more than the C signal and the Y signal. Therefore, the delay amount of the delay circuit 40 is increased to delay the Y signal. And the C signal can have a predetermined phase difference. By performing this adjustment, during recording, the C signal passes through the delay circuit 30 (having the same delay amount A as the delay circuit 40: the delay circuit 40 is also used in this embodiment). The error is compensated, and the same pattern as the reference tape can be recorded.

Since the heads Y1 and C1 and the heads Y2 and C2 have different mechanical mounting positions, the delay amounts of the respective delay circuits need to be set separately.

Alternatively, a tracking error signal may be obtained only for the heads Y1 and C1, and the tracking error signal may be held for the remaining period. Further, a malfunction may occur before and after the timing of head switching and near the vertical flyback period. Therefore, it is desirable to hold the tracking error signal.

In the present embodiment, the delay circuits 30 and 40 are used for both recording and reproduction, but may be separate circuits. That is, the delay amount of the time axis compression unit 28 may be linked to the delay amount of the delay circuit 40 during reproduction.

As described above, according to the present embodiment, the tracking system can be configured with only a few additional circuits, and since the tracking error signal is obtained using the horizontal synchronization signal, the responsiveness and accuracy are excellent. In addition, 2
Since signals from the two heads are used, the tracking error signal is not affected even if the rotating drum has jitter. Further, no special area, head and signal band on the tape for tracking are required.

Although the embodiment shown in FIG. 1 uses the Y, C _W , and C _N signals as input / output signals, the present invention is not limited to this. In the above embodiment, the parallel recording method of the Y signal and the C signal compressed on the time axis is used, but the present invention is not limited to this method. That is, the present invention can be applied to any device that records and reproduces signals including synchronization signal components of two or more channels in parallel.

Also, in the case where tracking control is performed by moving a head in the track width direction using a bimorph element or the like, the present invention can be applied by using signals of two heads that are close to each other. Particularly, since the sampling rate is high, tracking with good responsiveness can be realized.

Embodiment 2 FIGS. 6 to 9 show a digital signal recording / reproducing apparatus according to a second embodiment to which the present invention is applied. Here, FIG. 6 is a block diagram showing the entire second embodiment, and FIG.
The figure shows the arrangement of the rotary head, FIG. 8 shows the format of the data to be recorded, and FIG. 9 shows the signal waveform diagram. As shown, in the present embodiment, eight heads A1, A
Recording and reproduction are performed using 2, B1, B2, C1, C2, D1, and D2.

Dozens to hundreds of megabps like a digitized video signal
In order to record and reproduce a high-speed signal of s, it is necessary to distribute the signal to several channels and record it. Therefore, in this embodiment, recording and reproduction are performed simultaneously using four circuits.

The rotary head unit 1 has eight heads A1 to D2 mounted thereon, and runs the tape 2 with 180 ° + α wound thereon to sequentially form diagonal tracks similar to those in the first embodiment. Head A1, A2, C
1, C2 and heads B1, B2, D1, D2 are given azimuths in directions opposite to each other, so that the time difference between adjacent reproduction signals, which is time T with respect to the off-track of the head, is similar to the first embodiment. (See equation (1)).

A format signal as shown in FIG. 8 is recorded on each track. "SYNC" shown in FIG. 8 is a signal of a fixed pattern that cannot be represented in normal data such as a series of several "1s", and is a signal indicating the beginning of data.
“ID” is a signal indicating an address attached to data, “DATA” is a true data part, and “ECC” is a correction code for detecting and correcting an error in the “DATA”.

 Next, the operation of this embodiment will be described.

At the time of recording, an input signal is input to the encoder unit 60, where it undergoes processing necessary for magnetic recording, such as data rearrangement, ID addition, and ECC addition. Next, 4
Distributed to system signals. Further, the timing of the signals of each system is adjusted by the delay units 64 to 70, respectively, and recorded.

At the time of reproduction, the waveform of the reproduced signal from each head is different from that at the time of recording due to the differential characteristics and the like, so that the waveform equalization processing is performed. Then, by sampling the reproduced signal with a reproduced clock generated by a PLL circuit that follows a clock component in the signal, the signal is restored to an original digital signal. These signal processings are performed by the circuits 72 to 78 in FIG.
It is performed in. After that, the four digital signals are combined
The signal is synthesized by the decoder 82 and sent to the decoder 84. The encoder 84 performs error correction and data rearrangement in the decoder 84.
The processing opposite to that of 60 is performed, and an output signal is obtained.

Further, the clock signal CLA of the PLL circuit A that follows the reproduced output from the heads A1 and A2 and the clock signal CLB of the PLL circuit B that follows the reproduced output from the heads B1 and B2 are input to the n frequency dividing circuit 80, respectively. , N and then input to the phase comparator 86. Then, a tracking error signal can be obtained by comparing the phases of the outputs of the n frequency dividing circuit 86. here,
The reason for dividing the clock signal from each PLL circuit is
It is as follows. In other words, the frequency of the PLL clock is very high, which corresponds to twice the highest frequency of the recording signal, so that even a slight off-track causes a time lag of one cycle or more, and the tracking dynamic range becomes too narrow. It is. Therefore, the off-track amount (eg, ± 1/2
Even if a time difference corresponding to (track pitch) occurs, it is necessary to divide the frequency so that the phase difference between the two comparison signals does not exceed ± 180 °. In this frequency dividing circuit 80, as shown in FIG.
The waveform of (b) is obtained by dividing the fall of the clock signal (a) from the PLL circuit by eight, but the position on the track is determined like the signal indicating the timing of the ID signal, ie, the ID pulse (c). By resetting with a signal, it is possible to detect a phase difference between signals between the respective heads even after frequency division by n.

The tracking error signal is obtained during a period in which the two heads A1 and B1 and the two heads A2 and B2 are in contact with the tape at the same time. In order to leave the tape, it is necessary to hold the tracking error signal during this time.
Alternatively, it is also possible to similarly obtain a tracking error signal using the remaining PLL circuits PLL C and PLL D.

As in the first embodiment described above, the heads A1 and B1, A2
The phase comparison circuit 86 needs to be able to separately set the phase relationship between the signals from the PLL circuit A and the PLL circuit B in accordance with the head mounting phase difference between the signals A and B2. This is because either one of the signals from PLL A or PLL B is delayed for a certain time and then given to the phase comparison circuit 86, and the amount of delay can be adjusted separately for the heads A1 and B1, A2 and B2 It is achieved by doing so. In order to perform compatibility adjustment, the reference tape is reproduced to adjust the delay amount, and the delay amounts A and B during recording are changed in accordance with the delay amount. It can be done easily.

In the second embodiment described above, a circuit newly required for tracking is a PLL clock frequency dividing circuit 80.
, A phase comparison circuit 86, and a recording signal delay amount variable section 64-70.
Only with a small number of additional circuits. Further, the necessary off-track detection range and sampling rate can be set by the frequency division ratio of the n frequency dividing circuit. Further, since a tracking error signal can be generated if a synchronization pulse is detected once, a tracking servo with very high response can be realized in combination with a high sampling rate.

[Effects of the Invention] As described above, according to the reproducing apparatus of the present invention, a signal of a constant frequency component included in two parallel signals is compared in phase to obtain an error signal for tracking control. This makes it possible to realize high-accuracy and high-speed response tracking control without using a large-scale additional circuit or an extra head.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a top view of a rotary head according to the first embodiment of the present invention, and FIG. 3 is a track according to the first embodiment of the present invention. FIG. 4 is a track pattern diagram showing the principle of generation of a time difference between adjacent track signals. FIG. 5 is a signal waveform diagram of a phase comparator. FIG. 6 is a block diagram showing a second embodiment of the present invention. FIG. 7 is a top view of the rotary head according to the second embodiment of the present invention, FIG. 8 is a data format diagram according to the second embodiment of the present invention, and FIG. 9 is used in the second embodiment of the present invention. FIG. 9 is a signal waveform diagram for explaining the operation of the n frequency divider to be used. 1 ...... rotary head, 2 ...... tape, 3 ...... capstan, V _H ...... head running speed, V _T ...... tape running speed, Y1, Y2, C1, C2 ...... head, 20 ...... synchronization Addition circuit, 24: Modulation circuit, 28: Time axis compression multiplexing / synchronization addition circuit, 30: Delay circuit, 32: Modulation circuit, 38: Demodulation circuit, 40: Delay circuit, 42: Synchronization separation Circuit, 46 demodulation circuit, 48 synchronization demultiplexing circuit, 50 delay circuit, 52 time expansion / separation circuit, 54 output detection circuit, 56 phase comparator, 58 capstan Servo circuit.

Claims (2)

(57) [Claims] A plurality of heads for reproducing a plurality of systems of signals recorded in parallel on a recording medium; a detecting means for detecting whether or not an output of a certain level or more is obtained from each of the heads; Phase comparison means for detecting a phase difference between signals having a predetermined frequency component among signals reproduced from each of the heads; and an output of a certain level or more is obtained from each of the heads by the detection means. And a control means for performing tracking control of the head in response to the output of the phase comparison means only when the is detected. 2. A plurality of heads for reproducing a plurality of systems of signals recorded in parallel on a recording medium, and a frequency-divided signal having a predetermined frequency component among signals reproduced from each of the heads. A plurality of frequency dividing means, a phase comparing means for detecting a phase difference between outputs of the plurality of frequency dividing means, and a control means for performing tracking control of the head in response to an output of the phase comparing means. A playback device, characterized in that: