JP2537274B2 - Information signal reproduction device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information signal reproducing apparatus, and more particularly to an apparatus for reproducing an information signal from a plurality of parallel tracks in which a tracking control pilot signal is recorded together with the information signal. Regarding

[Conventional technology]

In the present specification, a helical-skiyan type magnetic recording / reproducing apparatus which records or reproduces a signal by a rotating head, which is inclined with respect to the longitudinal direction of the magnetic tape, will be described below as an example. In this type of magnetic recording / reproducing apparatus, a tracking apparatus for accurately scanning the rotary head on the track during reproduction is indispensable, and various types of apparatuses have been conventionally known. For example, a CTL method is known in which a track dedicated to tracking is provided in the longitudinal direction along the side edge of the magnetic tape and a control pulse (CTL) is recorded.

This method generates a pulse signal in synchronization with the rotation of the drum at the time of recording, and records it on the side edge of the tape as a CTL signal using a dedicated fixed head.
The signal is detected to control the running phase of the magnetic tape. This allows the rotating head to scan over the track to be scanned.

However, this CTL method requires a fixed head due to the existence of the longitudinal track, and it is necessary to arrange the tape path etc. in consideration of the fixed head in constructing the device, which is very disadvantageous. is there. Further, since the mounting accuracy of the fixed head directly affects the tracking accuracy, it is not suitable for a high-accuracy tracking device for high-density recording by narrowing the track. Further, for the same reason, it is difficult to maintain the compatibility of the devices, and there is a problem that the cost increases with the addition of the dedicated head.

In a device which performs high-density recording / reproduction under such a background, it is effective to record the pilot signal together with the information signal on the helical track.

As a method of using this kind of pilot signal, it is adopted in a four-frequency pilot method used in a so-called 8 mm format video tape recorder (VTR) and a rotary head type digital audio tape recorder (R-DAT). The area division pilot system is known. The former 4-frequency pilot system records four types of pilot signals, which have different frequencies at the time of recording, in a cyclical manner by switching every track cycle and frequency-multiplexes the video signal with each video track. By comparing the levels of two types of beat signals obtained by crosstalk from adjacent tracks on both sides of the track being reproduced, the deviation direction and amount of tracking can be detected, and the video track to be scanned can be accurately detected. The rotating video head is made to follow and scan.

On the other hand, in the latter area division pilot system, a dedicated area for recording a pilot signal is provided in the recording track to record a plurality of types of pilot signals. At the time of reproduction, the crosstalk amount of the pilot signals from both adjacent tracks in the dedicated area is detected and the tracking control is performed so that they are equal to each other.

Here, the area division pilot method will be described in more detail taking the method applied to the R-DAT as an example. The format recorded on the R-DAT is shown in FIG. Area of ATF1 and ATF2 in the figure (ATF: Automatic Trac
k Finding) is a dedicated area of the pilot signal for performing tracking control so that the rotary head correctly scans the recording track during reproduction. In the areas ATF1 and ATF2, a low frequency signal f _{1 with} a small azimuth loss is recorded as a pilot signal in at least a part (f _{1 in} FIG. 6).
This is used to detect the level of crosstalk level from both adjacent tracks during reproduction and obtain a tracking error signal according to the level difference.
Also in the area ATF1 and ATF2, sink signal for determining a position where the pilot signal of the frequency f ₁ is recorded is further recorded. As the sync signal, the plus azimuth track (A) has a sync signal f of frequency f _2.
2 is the frequency f ₃ in the track (B) of minor azimuth.
Are recorded at predetermined positions (positions indicated by f ₂ and f ₃ in FIG. 6). The erase signal of frequency f ₄ is recorded for the purpose of erasing the signal before recording.

The position of the pilot signal of frequency f ₁ is different between a certain track and its both adjacent tracks, and the pilot signals of both adjacent tracks of the certain track are arranged so that they can be reproduced and detected at different timings with respect to each other. . The recording pattern of such a pilot signal is a 4-track sequence by the combination of the signals as shown in FIG. 6, and is controlled so as to be tracked to a desired track.

Further, in Japanese Patent Application No. 62-265560 filed earlier by the present applicant as one of the area division pilot systems of this type, two types of pilot signals are used, and tracking control is similarly realized.

[Problems to be solved by the invention]

However, even with the pilot system, which is considered to be suitable for high-density recording, the conventional system does not partially record the pilot signal due to head clogging (clock) that occurs during recording and playback, or tape damage. Or it will be unplayed. Accordingly, the tracking error signal is
It becomes an abnormal value. This forms a tracking error signal that follows the difference in crosstalk of the pilot signals between adjacent tracks, so if one or both signals of these two tracks are not reproduced for some reason, the tracking error signal will be large. An error will occur. This phenomenon disturbs the control of the capstan and adversely affects the reproduced signal.

Against this background, the present invention has an object of enabling an excellent tracking control in an information signal reproducing apparatus having a plurality of heads for tracing adjacent tracks even if there is a recording defect or a reproducing defect. .

[Means for solving problems]

Under such an object, according to the present invention, in an apparatus for reproducing the information signal from a plurality of parallel tracks in which a tracking control pilot signal is recorded together with the information signal, a plurality of adjacent tracks are traced. Reproducing means having a head, means for generating a tracking control signal based on a level difference between reproduction pilot signals from both adjacent tracks of a main reproducing track of each head of the reproducing means, and detection of dropout of the reproduction signal of each head. A dropout detecting means, and a period during which a dropout occurs in at least one of the plurality of heads based on a detection output of the dropout detecting means,
A head signal having dropouts in the reproduction signal and a head signal tracing a track adjacent to the head tracing track are reproduced. .

[Work]

With the above-described configuration, defective tracking control is performed even when the reproduction head itself cannot reproduce a signal and when the recording of both adjacent tracks of the main reproduction track used to form the tracking control signal is defective. The signal is no longer generated.

〔Example〕

Hereinafter, Japanese Patent Application No. 62-26 filed by the present applicant for the present invention
Digital using the tracking method disclosed in 5560
An example applied to a VTR will be described.

FIG. 1 is a diagram showing the construction of a reproduction system of a digital VTR as an embodiment of the present invention, and FIG. 2 is a digital VT of FIG.
Diagram showing the head configuration of R, Fig. 3 is the digital V of Fig. 1.
FIG. 4 is a diagram showing a recording format on the magnetic tape which the TR is about to reproduce, and FIG. 4 is an enlarged view of a main part of FIG.

In FIG. 3, 1 is the magnetic tape, A is the scanning direction of the rotary head, B is the feeding direction of the magnetic tape, and t1 to t6 are tracks, respectively, and a pilot signal is recorded in the hatched area by vertical lines. It is the part that is. FIG. 4 is an enlarged view of the vicinity of the recording area of the pilot signal, f ₁ , f ₂
The pilot signals of frequencies f ₁ and f ₂ are recorded in the portions marked with, respectively. The area before and after the recording area of this pilot signal is surrounded by an area indicated by IBG (IBG: Inter Block Gap) in the figure. In this area IBG, a signal that does not include the frequency components of f ₁ and f ₂ is recorded or erased. V is a recording area of a video signal.

In FIG. 2, reference numerals 2a, 2b, 2c, 2d, 2e and 2f are rotational recording / reproducing heads, respectively, which trace the tape 1 wound on the drum D in an angular range of 180 ° or more. The heads 2a, 2b, 2c have a rotational phase difference of 180 ° with respect to the heads 2d, 2e, 2f, and the heads 2a, 2b, 2c are arranged close to each other.
2f are also placed close to each other. Heads 2a, 2c, 2e also have the same azimuth angle, and heads 2b, 2d, 2f also have the same azimuth angle, and heads 2a, 2c, 2e have the same azimuth angle and heads 2b, 2e.
The azimuth angles of d and 2f are different.

When the drum D rotates 1/2 turn, the recording / playback head is 2a, 2b, 2c.
And 2d, 2e, 2f are switched, and three rotating heads are constantly in contact with the tape 1 to record and reproduce signals of three systems. For example, the tracks t1, t2, t3, t in FIG.
4, t5 and t6 are recorded at heads 2a, 2b, 2c, 2d, 2e and 2f, respectively.

Regarding the operation at the time of recording, when the heads 2a to 2f are tracing the areas f ₁ and f ₂ of the tracks t1 to t6, respectively, the pilot signal is recorded and the area V is traced. Record the signal.

Next, the reproducing system will be described. In FIG. 1, 1 is a magnetic tape, 2 is a reproduction head, 3 is a reproduction amplifier, and the reproduction signal obtained from the magnetic tape 1 is a signal processing circuit 4, a dropout detector 5, a bandpass filter (BPF) 6 and BPF
Respectively. The outputs of BPF6 and BPF8 are input to detectors 7 and 9, respectively, and their outputs are selected by switching switches 10a and 10b, and sampling hold (S / S
H) Input to the circuits 12 and 13 or the comparator (COMP) 14. S / H
The circuits 12 and 13 operate by the output of the comparator 14, and the output signals are input to the subtractor 15, respectively. The output of the subtractor 15 is
Input to the S / H circuit 16. The S / H 16 operates by the output of the timing generator 21, and the output is input to the average value calculation 19. The average value calculator 19 is controlled by the signal from the dropout detector 5, and its output is input to the capstan drive circuit 20.

200 and 300 are circuits having the same configuration as the circuit 100 surrounded by a solid line, and each output has the same S / H circuits 17 and 18, as the circuit 100.
It is input to the average value calculator 19. Two heads are selectively used as the heads 2 in the circuits 100, 200, and 300, respectively. For example, circuit 100 is head 2a, 2d, circuit 200
The heads 2b and 2e are selectively used, and the circuit 300 selectively uses the heads 2c and 2f. However, in the figure, the head switching switches 2a and 2d, 2b and 2e, 2c and 2f are omitted.

The operation will be described in detail below. Of the signals reproduced from the magnetic tape 1 by the recording / reproducing head 2 and the reproducing amplifier 3, the signal relating to the recording data is processed by the signal processing circuit 4 and output as a reproduced signal from the terminal 25a. The reproduction signal of the head 2 is detected by the dropout detector 5 for the presence or absence of dropout. On the other hand, BPF6, BPF
8 detects the frequency components of f ₁ and f ₂ , respectively, and
The signal levels of f ₁ and f ₂ are detected by 9. Switch 10a
Is the signal level of the pilot signal reproduced from both adjacent tracks of the track which the head 2 should mainly trace,
The switch 10b is switched each time the drum D makes one revolution so that the head mainly selects the signal level of the pilot signal reproduced from the track to be traced.
The output of the switch 10a is input to the S / H circuits 16 and 17, and the output of the switch 10b is input to the comparator 14. The comparator 14 generates a pulse for sampling the level of the pilot signals of the two adjacent tracks mentioned above, and the switch 10b.
The rising and falling edges of the signal level output from are detected. The two pulses output from this comparator 14 cause S / H
The circuits 12 and 13 operate. By this operation, the crosstalk amount of the pilot signal from the adjacent track is S / H.
This corresponds to the output level of the circuits 12 and 13. Subtractor 1
Reference numeral 5 detects a tracking error of the head 2 by obtaining the difference between the output levels of the S / H circuits 12 and 13, and outputs a tracking error signal. The above operation is for each circuit 100, 200, 30
It is carried out at 0 respectively and becomes the input of the S / H circuits 16, 17, and 18.
The timing generator 21 generates a sampling pulse at the timing when each circuit 100, 200, 300 forms a tracking error signal from the pilot signal, that is, at the timing after all the S / H circuits 13 of each circuit 100, 200, 300 operate, and S / H. Captured and held in the circuits 16, 17, and 18, respectively. In a normal state where there is no dropout, the tracking error signals from the three heads obtained by the S / H circuits 16, 17, and 18 are added and averaged by the average value calculator 19 and input to the capstan drive circuit 20. And tracking control is performed. Here, the tracking error signals obtained from the three heads are added and averaged because the three heads are arranged close to each other as shown in FIG. Therefore, the purpose is to improve the stability of tracking by taking the average value in consideration of the stability of capstan control.

Next, the case where the dropout of the reproduction signal is detected in each circuit 100, 200, 300 will be described. If a dropout occurs in the reproduction signal of the head 2b, the signal has not been recorded in the track t2 shown in FIG.
Either 2b could not be played. In the former case, the tracking error signal obtained from the reproduction signal of any head that reproduces the tracks t1, t2, and t3 is an abnormal value, and in the latter case, it is obtained from the reproduction signal of the head that reproduces track t2. It is considered that only the tracking error signal has an abnormal value. Therefore, if a dropout occurs in the reproduction signal of the head for reproducing the track in the period during which the pilot signal is reproduced, the head and the reproduction signal of the head to be reproduced by both the adjacent tracks of the track traced by the head It is possible that all of the obtained tracking error signals have abnormal values. Therefore, it is desirable not to use all the tracking error signals obtained from the reproduction signals of these heads for tracking control.

By the way, according to the above-mentioned logic, dropout occurs in the reproduction signal of the head 2d, and if the pilot signal cannot be reproduced, the tracking error signal obtained from the reproduction signal of the head 2c may have an abnormal value. However, since the head 2d traces on the tape 1 with a delay from the head 2c in a period close to the half-rotation of the drum D, the tracking error signal obtained from the reproduction signal of the head 2c should not be used for tracking control. In order to configure it, it is necessary to output the tracking control signal at a timing delayed by a period longer than the half rotation of the drum D. This greatly deteriorates the responsiveness of tracking control. Also, the circuit configuration becomes complicated. Similarly, when the pilot signal cannot be reproduced from the reproduction signal of the head 2c, the tracking error signal obtained from the reproduction signal of the head 2d may have an abnormal value. In this case, the responsiveness of tracking control is not deteriorated, but the circuit configuration becomes complicated.

Therefore, in the digital VTR of this embodiment, when the dropout detector 5 in the circuit 100 detects the dropout during the period in which the pilot signal should be reproduced, the circuit 10
If a tracking control signal is formed without using the tracking error signal output by 0,200, and the dropout detector 5 in the circuit 300 detects a dropout during the period in which the pilot signal should be reproduced, the tracking output by the circuit 200,300 is output. The tracking control signal is formed without using the king error signal. Furthermore, two or more of the circuits 100, 200, 300,
Alternatively, if the dropout detector 5 in the circuit 200 detects a dropout during the period in which the pilot signal should be reproduced, these three signals are used to form the tracking control signal.
The configuration is such that the tracking error signals output by the two circuits are not used.

FIG. 5 is a diagram showing an example of the configuration of the average value calculation circuit of FIG. 1 for realizing the above-mentioned concept. In the figure, 51, 52 and 53 are the detection signals of the dropout detector 5 in the circuits 100, 200 and 300, respectively. It is an input terminal. The dropout detector 5 outputs a high level (Hi) when the dropout occurs in the reproduction signal of each system in all periods. On the other hand, at the terminal 54, while the head 2 of each system from the timing generator 21 traces the recording area of the pilot signal,
A pulse signal that becomes Hi is input, and if a dropout occurs within this period, the AND gates 55, 56, 57 become Hi. Mono-multi (MM) 58,59,60 is AND gate 55,56,
Trigger on the rising edge of the output of 57 and maintain Hi for a period corresponding to the pulse width of the pulse signal input to the terminal 54.

From the timing generator 21 to the S / H circuit 16,
A pulse for operating 17, 18 is input, and its timing is set immediately after the pulse signal input to the terminal 54 changes to low level (Lo). As a result, when the inverted outputs of the latch circuits 62, 63, 64 are Lo, the S / H circuits 16, 1
It indicates that dropout has occurred in the reproduction signal for forming the tracking error signal output by 7,18.

The tracking error signals output from the S / H circuits 16, 17, 18 are supplied to terminals 65, 66, 67, and the level of each tracking error signal is reduced to 1/3 by the attenuators 68, 69, 70 and post-added. The unit 71 adds the values and the average value of each tracking error signal is obtained.

Now, if any of the circuits 100, 200, and 300 is played back without dropout due to dropout, the output of the AND gate 72 becomes Hi and the gate circuit 73 is closed, so the average value output from the adder 71 is controlled by tracking. The signal is supplied to the capstan drive circuit 20 via the terminal 75 on the N side of the switch 74 as a signal.

Next, when the dropout occurs only in the head reproduction signal of the circuit 100, the output of the AND gate 76 becomes Hi and the gate 77 is closed, so that the tracking error signal output from the circuit 300 is the tracking control signal. Is supplied to the capstan drive circuit 20.

If dropout occurs only in the head reproduction signal of the circuit 300, the output of the AND gate 78 becomes Hi and the gate 79 is closed. Therefore, the tracking error signal output from the circuit 100 is used as the tracking control signal. It is supplied to the capstan drive circuit 20.

In other cases, none of the tracking error signals output from the circuits 100, 200, 300 can be used.
The S / H circuit 80 holds the tracking control signal output immediately before as it is. On the other hand, the output of NOR gate 81
When it becomes Hi, the output of the S / H circuit 80 is supplied to the capstan control circuit 20 as a tracking control signal via the S terminal of the switch 74.

In the digital VTR of the embodiment as described above, even though the circuit configuration is simple, it is possible to minimize the opportunity for tracking control due to an invalid tracking error signal, and when a dropout occurs in the reproduction signal. However, stable tracking control can be performed.

Although the dropout detector 5 is provided in the latter stage of the amplifier 5 in the above embodiment, it may be provided in the latter stage of the switch 10b.

In the above embodiment, the digital VTR is described as an example, but the information signal is reproduced by a plurality of heads tracing a plurality of adjacent tracks, and the reproduction pilot signal from both adjacent tracks of the main reproduction track of each head is reproduced. The same effects can be obtained by applying the present invention to any information signal reproduced from any recording medium, as long as it is a device that forms a tracking control signal based on the level difference.

〔The invention's effect〕

As described above, according to the present invention, stable tracking control can be realized in an apparatus for reproducing an information signal with a plurality of rotary heads for tracing adjacent tracks even if a recording failure or a reproduction failure occurs. It was

[Brief description of drawings]

FIG. 1 is a diagram showing the construction of a reproduction system of a digital VTR as an embodiment of the present invention, FIG. 2 is a diagram showing the head construction of the digital VTR of FIG. 1, and FIGS. 3 and 4 are magnetic tapes. FIG. 5 is a diagram showing the above recording pattern, FIG. 5 is a diagram showing a specific example of the average value calculating circuit in FIG. 1, and FIG. 6 is a diagram showing an example of the recording pattern on the tape by the area division pilot system. . 1 is a magnetic tape, 2, 2a, 2b, 2c, 2d, 2e, 2f are rotating heads, 5 are dropout detectors, 6 and 8 are BPFs, 7 and 9 are detection circuits, 12 and 13 are sample and hold circuits, 14 is a comparator, 15 is a subtractor, 16, 17 and 18 are sample and hold circuits, 19
Is an averaging circuit, 20 is a capstan drive circuit, 72,76,78
Is an AND gate, 73, 77, 79 are gate circuits, 74 is a switch, 80 is a sample and hold circuit, and 81 is a NOR gate.

Claims (1)

(57) [Claims] 1. An apparatus for reproducing the information signal from a plurality of parallel tracks in which a tracking control pilot signal is recorded together with the information signal, and a reproducing means having a plurality of heads for tracing adjacent tracks. A means for generating a tracking control signal based on a level difference between reproduction pilot signals from both adjacent tracks of a main reproduction track of each head of the reproduction means, and a dropout detection means for detecting a dropout of the reproduction signal of each head, During a period in which at least one of the plurality of heads has a dropout based on the detection output of the dropout detection means, a head in which a playback signal has a dropout and a head adjacent to the track traced by the head are traced. The pilot signal to be reproduced by Serial information signal reproducing apparatus comprising a means for inhibiting the use in tracking control signal generating means.