JPH05128654A - Tracking controller - Google Patents

Abstract

PURPOSE:To eliminate the disturbance of tracking in the case of performing a superscription or a rewrite recording to a previously recorded area in a long time mode. CONSTITUTION:A pilot signal f1 is picked up from a head output by a BPF 118A and the pilot signal f2 is picked up by the BPF 118B. They are detected by detecting circuits 120A, 120B and low-pass filtered by LPFs 124A, 124B and switched every track by switches 124A, 124B and applied to a comparator circuit 126. In a system control circuit 50A, which of heads HA+, HA- or heads HB+, HB- are on-track is discriminated by the output of the comparator circuit 126, and by the heads being on-track, reproduction hereafter is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device of a recording / reproducing apparatus for recording / reproducing information on / from a tape-shaped recording medium.

[0002]

2. Description of the Related Art Conventionally, a recording / reproducing apparatus for recording / reproducing a digital signal on a magnetic tape by a helical scan system
It is known, and further, a standard mode with a standard recording time,
There is also known a configuration that realizes a long-time recording mode that enables recording for a longer time although the image quality is slightly degraded by reducing the number of data tracks recorded in a unit time (for example, a patent application in 1988). Public No. 306504
issue).

FIG. 2 shows a digital signal recording / reproducing system having a standard mode (hereinafter, referred to as SP mode) and a double mode (hereinafter, referred to as LP mode) which enables double recording for a long time. The block diagram of the conventional example of an apparatus is shown.

In FIG. 2, a digital image signal is input to the input terminal 10. The DPCM encoding circuit 12 compresses the digital image signal from the input terminal 10 in half in the amplitude direction (for example, 8 bits to 4 bits) by differential encoding. The switch 14 selects the digital image signal of the input terminal 10 in the SP mode, and the DPC in the LP mode.
The output of the M encoding circuit 12 is selected. The data selected by the switch 14 is temporarily stored in the memory 16, read out, and applied to the separation circuit 18.

The separation circuit 18 divides the data read from the memory 16 into two systems. Error correction code (EC
C) The addition circuits 20A and 20B add error correction codes to the outputs of the respective systems of the separation circuit 18, and the digital modulation circuit 2
2A and 22B are error correction code adding circuits 20A and 20B
Is subjected to low-frequency suppression modulation (for example, 8-9 modulation). The outputs of the modulation circuits 22A and 22B are the amplifiers 24A and 24B.
B, recording / reproducing changeover switches 26A, 26B, and
Applied to the magnetic heads HA +, HB +; HA-, HB- via the head selection switches 34, 36; 38, 40,
It is recorded on the magnetic tape 42.

3 and 4 show switches 34, 36, 3
8 shows a timing chart of opening / closing control signals S1, S2, S3, S4 of 8 and 40. FIG. 3 shows the case of the SP mode, and FIG. 4 shows the case of the LP mode. Symbols d1 and d2 represent signals at common contact portions of the switches 26A and 26B. When the control signals S1, S2, S3, S4 are high, the corresponding switches 34, 36, 38, 40 are turned on. The shaded area in FIG. 4 indicates that there is no signal to be recorded, and the time base compression for forming this shaded area is executed in the memory 16.

FIG. 5 shows magnetic heads HA +, HB +, HA.
-, HB- is equipped with a plan view of a rotary cylinder, and FIG. 6 is a circumferential development view of the rotary drum. As shown in FIG. 5, the magnetic tape 42 is wound around the outer peripheral surface of the rotary cylinder 44 over an angle range of 180 ° or more.
Heads HA + and HB attached to the rotary cylinder 44
+ Is plus azimuth, and heads HA- and HB- are minus azimuth. Heads HA + and HB + rotate with a phase difference of 180 ° with each other, and heads HA- and HB- also have a position of 180 ° with respect to each other. Rotate with a phase difference. Further, the heads HA + and HA− rotate with a phase difference of an angle θ.

The operation of each head in the SP mode and the LP mode will be described. The cylinder 44 rotates twice while one frame of interlaced digital image signal is input to the input terminal 10. That is, in the case of the NTSC signal, the rotation speed of the cylinder 44 is about 3,600 rpm.

In the SP mode, each magnetic head HA +, HB +, HA-, HB- traces the magnetic tape 42 twice each while the cylinder 44 makes two revolutions, and records a signal on the magnetic tape 42. During this time, the magnetic tape 42 is conveyed at a constant speed by the capstan 48 controlled by the capstan control circuit 46 so that eight tracks are formed in one frame at a constant track pitch Tp.

In the LP mode, a signal is recorded on the magnetic tape 42 by two traces of the magnetic heads HA + and HA- while the cylinder 44 makes two revolutions. Magnetic head HB
Do not use + and HB-. If the trace direction of the head is sufficiently small with respect to the longitudinal direction of the magnetic tape 42, the transport speed of the magnetic tape 42 by the capstan 48 is 1/2 of that in the SP mode, which is a track formed in one frame. The number is four.

The system control circuit 50 of FIG. 2 controls the above recording operation and controls the reproducing operation described below.

During reproduction, the switches 26A and 26B are set to P.
Switches 34, 36, 38, 40 connected to the contact side
Is opened and closed at the same timing as when recording. Reproduction signals of two systems can be obtained from the P contacts of the switches 26A and 26B, and these reproduction signals are reproduced amplifiers 52A and 5A.
It is amplified by 2B and demodulated by digital demodulation circuits 54A and 54B. The ECC decoding circuits 56A and 56B error-correct the demodulation outputs of the digital demodulation circuits 54A and 54B,
The synthesizing circuit 58 synthesizes the error correction outputs of the ECC decoding circuits 56A and 56B into the original 1-system signal. Synthesis circuit 5
The output of 8 is temporarily stored in the memory 60.

In the case of the signal recorded in the SP mode, the reproduction information passes directly through the memory 60, but in the case of the signal recorded in the LP mode, the memory 16 is time-axis-compressed at the time of recording. To extend the time axis and restore it to its original state.

Reproduction of recording signal in SP mode (hereinafter referred to as SP
It is called reproduction. In the case of), the digital reproduced image signal read from the memory 60 is output to the output terminal 66 via the switch 64. In the case of reproducing the recording signal in the LP mode (hereinafter, referred to as LP reproduction), the DPCM decoding circuit 62.
Performs DPCM decoding on the output of the memory 60 and expands it in the amplitude direction. The output of the DPCM decoding circuit 62 is applied to the output terminal 66 via the switch 64.

In such a recording / reproducing apparatus, a CTRL in a so-called VHS system is used as a tracking control system in which a rotary head accurately scans a recording track during reproduction.
Although a system using a head and a pilot signal superimposing system in an 8 mm video system have been proposed, the following system has been proposed by the present applicant as a system suitable for digital recording. That is, in this tracking control method, two types of pilot signals f1 and f2 are recorded on a part of each track with the no-signal recording area IBG interposed therebetween. The track pattern is shown in FIG. In FIG. 7, t
1, t2, t3, and t4 are heads HA + and HA, respectively.
Tracks recorded and scanned by −, HB +, and HB−, and hatched portions with diagonal lines are pilot signal recording areas.

FIG. 8 is an enlarged view of a portion of the pilot signal recording area of FIG. As can be seen from FIG. 8, the pilot signals of different frequencies f1 and f2 are alternately recorded for each track, and the pilot signal recording area of each track partially overlaps with the pilot signal recording area of the adjacent track. Furthermore, each pilot signal recording area is arranged such that the beginning and the end of a certain pilot signal recording area are located at the center of the pilot signal recording areas of the adjacent one and the other tracks, respectively.

FIG. 9 is a block diagram showing the configuration of a tracking control circuit for controlling tracking with the above pilot signal. Figure 12 shows the waveform of each part during SP playback.
FIG. 13 shows the waveform of each part during LP reproduction.

In FIG. 9, heads HA +, HA-, H
The outputs of B + and HB- are reproduction amplifiers 102 and 1, respectively.
04, 106, 108 and switches 110, 112, 1
BPF 118A and BPF 118B through 14, 116
Applied to. The system control circuit 50 is similar to that shown in FIG.
At the timing of extracting the head output from the pilot signal recording area shown in FIG.
Turn on 4,116.

The BPF 118A extracts the pilot signal component of the frequency f1, and the BPF 118B extracts the pilot signal component of the frequency f2. Detection circuit 120A, 120
B detects the outputs of the BPFs 118A and 118B, and the LPFs 122A and 122B detect the detection circuits 120A and 1B.
20B output is low pass filtered. The LPF 122A outputs a voltage proportional to the magnitude of the pilot signal component of the frequency f1, while the LPF 122B outputs a voltage proportional to the magnitude of the pilot signal component of the frequency f2.

The outputs of the LPFs 122A and 122B can be switched by the switches 124A and 124B. The system control circuit 50 includes a switch 124A,
124B is switched for each track. Switch 124A
Thus, the outputs of the LPFs 122A and 122B are alternately applied to the comparison circuit 126 for each track. Comparison circuit 12
6 is a sampled value by the switch 124A, which is a predetermined threshold value Vt.
Compared with h, and when larger than Vth, outputs logic H,
A logic L is output when Vth or less. Also, switch 12
4B selects one of the output signals of the LPFs 122A and 122B that is different from the switch 124A. Switch 12
The output of 4B is applied to the switches 128 and 130 as a track deviation detection signal.

The output of the comparison circuit 126 is applied to mono-multi vibrators (hereinafter abbreviated as mono-multi) 132 and 134, and the mono-multis 132 and 134 are compared.
A pulse of about several μs is output depending on the rising and falling edges of the output of. The output pulse of the monomulti 132 turns on the switch 128,
Output turns on switch 130. As a result, track deviation detection signals (switch 1
24B output) is stored in capacitors 136 and 138.

The output voltage difference between the capacitors 136 and 138 corresponds to the track shift amount of the rotary head. The differential amplifier 140 amplifies the output voltage difference of the capacitors 136 and 138, and the output is applied to the capstan control circuit 46. By performing servo control of the capstan 48 so that the two inputs of the differential amplifier 140 become equal, automatic tracking of the rotary head is realized.

In the LP mode, only the heads HA + and HA- are used for both recording and reproduction as shown in FIG.
Even for tracking control, only the switches 110 and 112 are turned on.

[0024]

In the above conventional example,
During LP reproduction, the system control circuit 50 causes the head HA +,
It is set to use HA- and the head HB
Do not use + and HB-. In self-recording / reproducing, the error rate tends to be smaller when reproducing with the magnetic head used for recording, and thus it is set as described above.

However, such a setting causes a disadvantage that the rise at the time of reproduction (especially LP reproduction) is delayed. On the other hand, from the actual error rate, the head HB
Even if + and HB- are used, there is practically no problem.

It is an object of the present invention to provide a tracking control device with improved start-up during reproduction.

[0027]

A tracking control apparatus according to the present invention records and reproduces information by a plurality of pairs of magnetic heads in a standard mode, and some of the plurality of pairs of magnetic heads in a predetermined long time mode. A tracking control device in a recording / reproducing device for recording / reproducing information by using, a means for determining which of a plurality of pairs of magnetic heads is on-track at the start of reproduction, and a magnetic head on-track It has a control means for performing tracking control by a pair.

[0028]

When the signal recorded in the LP mode is reproduced by the above means, the magnetic head pair used is not fixed. Since the pair of magnetic heads that are on-track at the start of reproduction is used for the subsequent reproduction, the start-up of the reproduction becomes faster.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the present embodiment, the output of the comparison circuit 126 is also supplied to the system control circuit 50A, and the system control circuit 50A is supplied.
A indicates the heads HA +, HA according to the output of the comparison circuit 126.
It is made possible to select whether to use − or the heads HB + and HB−. A flowchart of this selection is shown in FIG. The other components are the same as those in FIG. 9, and the same reference numerals as those in FIG. 9 are attached.

FIG. 12 shows L by the heads HB + and HB-.
P playback timing diagram, FIG. 13 shows heads HA + and HA
7 shows a flowchart of an operation for determining which of − or the heads HB + and HB− is used. FIG. 14 shows a timing chart at the rising edge of the LP reproduction.

The operation of this embodiment will be described in detail with reference to FIG. After starting the drum motor and waiting for a predetermined time, start the capstan motor. After confirming the lock of the phase servo of the drum motor and the lock of the speed servo of the capstan motor, the switch 11 is switched at the timing shown in FIG. 14 according to the rotation of the drum motor.
Turns 0 to 116 on / off.

FIG. 15A shows an example of the tracking position at the time of rising. In this example, the head HA + is on-track on the track t1 having the same azimuth, the pilot signal f1 is a sampling signal for the head HA +, and a track deviation detection signal is generated according to the rising and falling of this signal. A component of a certain frequency f2 is sampled.

The tracking position when the drum is rotated 180 ° is shown in FIG. 15 (b). By the time the head HB + facing 180 ° arrives, the magnetic tape 42 advances by 1 Tp (track pitch) by the capstan 48,
It is track t2. The pilot signal f1 which is a sampling signal for the head HB + does not exist in the adjacent track and is almost unreadable. Therefore,
The output of the comparison circuit 126 is L, and the monomulti 132,
134 does not output a pulse and cannot measure the off-track amount.

FIG. 16 shows the relationship between the off-track amounts of the heads HA +, HA-; HB +, HB- and the output of the differential amplifier 140. FIG. 16A shows the relationship between the off-track amount by the heads HA + and HA− and the output (error voltage) of the differential amplifier 140, and FIG. 16C shows the heads HB + and HB−.
3 shows the relationship between the off-track amount and the output (error voltage) of the differential amplifier 140. As shown in FIGS. 16A and 16C, an error voltage proportional to the off-track amount can be obtained for a certain amount of off-track.
When it exceeds 0.5 Tp), the output of the switch 124A does not exceed the threshold value Vth, so that the pulse signal for turning on the switches 128 and 130 cannot be obtained and the error voltage cannot be obtained.

FIG. 16B shows the presence / absence of the output of the comparison circuit 126 when it is assumed that the output of the switch 124A becomes equal to Vth when the heads HA + and HA- are off-tracked by 0.5 Tp. d) is the head HB
The presence or absence of the output of the comparison circuit 126 in the same case by + and HB- is shown. As shown here, which of the heads HA +, HA-; HB +, HB- is on-track at the rise of LP reproduction can be determined by the output of the comparison circuit 126.

Returning to FIG. 13, the switch 110 or 11 is used.
If the output of the comparison circuit 126 becomes H when 2 is ON, it means that the heads HA + and HA- are on-track within 0.5 Tp, and the system control circuit 50A
Each part is controlled at the timing of FIG.
Continue playback with A-. On the other hand, if the output of the comparison circuit 126 becomes H when the switches 114 or 116 are ON, it means that the heads HB + and HB- are on-track within 0.5 Tp, and the system control circuit 50A.
Controls each part at the timing of FIG.
Reproduction by + and HB- is continued.

In the conventional example, during LP reproduction, for example, FIG.
The timing is set to 3, and it takes a long time to pull in when an error voltage is not obtained due to off-track at the start of reproduction, but in the present embodiment, the error voltage is always obtained. Response characteristics are significantly improved.

[0039]

As can be easily understood from the above description, according to the present invention, the response during LP regeneration is remarkably improved.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 is a basic configuration block diagram of a recording / reproducing apparatus which is a target of the present embodiment.

FIG. 3 is a timing diagram of head switching in SP mode recording.

FIG. 4 is a head switching timing chart for LP mode recording.

FIG. 5 is a plan view of a 4-head cylinder.

FIG. 6 is a development view of FIG. 4.

FIG. 7 is an explanatory diagram of an arrangement of pilot signal recording areas.

FIG. 8 is an enlarged view of the vicinity of a pilot signal recording area.

FIG. 9 is a configuration block diagram of a conventional example of a tracking control circuit.

FIG. 10 is a timing chart of SP reproduction in FIG.

FIG. 11 shows L by the heads HA + and HA− in FIG.
It is a timing chart of P reproduction.

FIG. 12 is an L diagram of heads HB + and HB− in FIG.
It is a timing chart of P reproduction.

13 is an operation flowchart of tracking control during LP reproduction in FIG.

FIG. 14 is a timing diagram at the start of LP reproduction by the heads HA + and HA−.

FIG. 15 is a diagram showing an example of a head position at the start of LP reproduction.

FIG. 16: Off-track amount, error voltage, comparison circuit 1
It is a figure which shows the relationship of the output of 26.

[Explanation of symbols]

10: Input terminal 12: DPCM encoding circuit 14: Switch 16: Memory 18: Separation circuit 20A, 20
B: Error correction code addition circuit 22A, 22B: Digital modulation circuit 24A, 24B: Amplifier 26A, 26
B: Recording / reproduction changeover switch 34, 36, 38, 4
0: Head selection switch 42: Magnetic tape 44: Rotating cylinder 46: Capstan control circuit 48: Capstan 50: System control circuit 50A: System control circuit 52A, 52B: Reproducing amplifiers 54A, 54B:
Digital demodulation circuit 56A, 56B: ECC decoding circuit 58: Synthesis circuit 60: Memory 62: DPCM decoding circuit 64: Switch 66: Output terminal 102, 10
4, 106, 108: reproduction amplifiers 110, 112, 1
14, 116: Switch 118A, 118B: BPF
120A, 120B: Detection circuit 122A, 122
B: LPF 124A, 124B: Switch 126:
Comparison circuit 128, 130: switch 132, 13
4: Mono multivibrator 136, 138: Capacitor 140: Differential amplifier HA +, HB +, HA-,
HB-: Magnetic head

Claims (1)

[Claims] 1. A tracking in a recording / reproducing apparatus, wherein information is recorded / reproduced by a plurality of pairs of magnetic heads in a standard mode, and information is recorded / reproduced by using some of the plurality of pairs of magnetic heads in a predetermined long time mode. A control device comprising: a means for determining which of the plurality of pairs of magnetic heads is on-track at the start of reproduction, and a control means for performing tracking control by the pair of on-track magnetic heads. And tracking control device.