JPS63166061A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To stabilize tracking to an optimum state and to read a data with minimum level of missing, by transmitting an obtained tracking error signal to a tracking control system with a transfer gain being almost inversely proportional to a time interval, in a case that times when the tracking error signals are obtained are not arranged with equal intervals on a time base. CONSTITUTION:A reproducing signal sent to a control path 128 is inputted to an (Automatic Track Finding) ATF sync detection circuit 160, and sync signals f2 and f3 in an ATF signal are detected. A pilot level detection circuit 166 detects a tracking error at a tracking error detection circuit 168 by a timing signal generated from a timing generation circuit 170 based on the signals f2 and f3. An ATF1/ATF2 discrimination circuit 176 discriminates whether a detected ATF signal is an ATF1 or an ATF2, and performs the switching of a gain. In other words, the gain is increased in the ATF1 and is decreased in the ATF2, and its ratio is inversely proportioned to the time interval where an error signal is operated. In such a way, it is possible to apply the tracking, and to read the data with the minimum missing.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to magnetic fields such as fl-DAT (rotating head type digital audio tape recorder) where the points at which tracking error signals are obtained are not equidistant on the time axis. The present invention relates to a recording and reproducing apparatus that improves the reliability of tracking control during reproduction.

[Conventional technology]

R-DAT converts analog signals such as audio into PCM signals, records the PCM signals on magnetic tape using a rotating head, and reproduces them.

As shown in Fig. 2, the mechanism has a rotary head 2 equipped with 211M magnetic heads A and B at 180° intervals on the circumferential surface of a cylinder 1, and the tape 3 is transferred from a cassette 4 to a vertical post 5 or an inclined post. It is loaded with a post 6 and wrapped around the circumferential surface of the zero-rolling head 2 at 90 degrees, further supported by a fixed guide 7, and moved by a kill stand 8 and a pinch roller 9.

The diameter of the rotating head 2 is 30M, and the tape winding angle is 9
0°, the speed of the rotating head 2 is 200 Orpm (peripheral speed 3.14
TrL/S), -r-73's speed is defined as 8.15 m/s in the same direction as the rotating head 2, and the relative speed between the rotating head 2 and tape 3 is 3.13 m.

The recording method of R-DAT is helical scanning azimuth recording, and the tape format is defined as a track angle of 6° 22'59.5", an azimuth angle of ±20", and two tapes, as shown in Figure 3. Heads A and B trace the track alternately.

As shown in Figure 4, the track format is to record audio data in the central PCM area, and to record the audio data in the front and back sides of the Nisub code and ATF (AutomaticTr).
Ack Finding) and other control signals are recorded.

As shown in Fig. 5, the PCM area is composed of 128 blocks, each block containing a block sync (indicating the block start position), an ID (identification) code, a block address, a parity check code, and audio data. It has a recording area.

Audio data has a sampling frequency of 48 in mode I.
A 2/S combination code with a frequency of kHz and 16 bits is used, and this PCM data is divided into upper and lower 8 bits, 8-10 modulated, and recorded with 10 bits each.

Tracking control during playback of R-DAT is as follows:
An automatic tracking method using ATF is adopted.

The ATF uses the ATF signal recorded on the track (see Figure 4) to detect and compare the distance [1 stroke 1 km] from the adjacent tracks on the left and right, and adjusts the tape running so that the loss talk level on both sides is equal. It controls the speed of the capstan motor.

The principle of ATF will be explained.

As shown in FIG. 4, the ATF signal is recorded in two locations, ATF1 and ATF2, on one track. The format is as shown in FIG. 6, in which a pilot signal f1 and a sync signal f2 (or f3) are recorded on each track. These frequencies are defined as f2-522.67kHz f3=784.0OkHz in fl-130,67. Since these are low frequencies, azimuth loss is also small.

Head A traces the track with the sync signal f2,
Head B traces the track with the sync signal f3. The length of the sync signal is different between even frames and odd frames, and is defined as 0.5 block and 1 block, respectively.

Now, as shown in FIG. 6, if head A is tracing track T4, head A will trace track T4.
In addition to the reproduction signal of T3.4, the left and right adjacent tracks T3. A pilot signal f1 is obtained from T5 (because the head has a width approximately 1.5 times that of the track). At this time, if head A is correctly tracing track T4, the crosstalk between tracks T and T5 will be the same, but if they are biased in either direction, the crosstalk amount will be different. Therefore, by detecting the amplitude levels of the pilot signal f1 in the track T5 and the pilot signal f1 in the track T3 based on the detection timing of the sync signal f2 in the track T4, the amount of crosstalk from both tracks T and T3 can be determined. Therefore, the tracking error can be determined by taking the difference between these crosstalk ranks.

A conventional ATF device using the above principle is shown in FIG. The playback signal from head A is passed through the playback amplifier 14.
The pilot signal f1 is input to the low-pass filter 16.
is extracted. This pilot signal f1 is input to the tracking error detection circuit 21, its envelope is detected by the envelope detection circuit 18, and input to the sample and hold circuit 26. The sync detector 19 detects the sync signal f2 using the equalizer 20 and the comparator 22,
The comparator 22 outputs "1" during the detected period.

The logic circuit 24 generates sample and hold signals SP1. based on the timing of the detected sync signal f2. SP2
Output. The sample and hold signal SP1 is output immediately after the detection of the sync signal f2 starts, and by sampling the output of the envelope detection circuit 18, the sample and hold signal SP1 is sent to the sample and hold circuit 26 to detect the next track T that is currently being traced. The crosstalk amplitude level of the pilot signal f1 in track T5 is held. The subtracter 28 is a sample hold circuit 26
The output of the envelope detector 18 is subtracted from the output of the envelope detector 18. The sample hold signal SP2 is output two blocks after the start of detection of the sync signal f2 (approximately at the middle timing of the pilot signal f1 of the track T3), and is used to sample the output of the subtracter 28. By holding, the sample and hold circuit 30 stores tracks T4 adjacent to the left and right of the track T4 currently being traced.
3. The difference in crosstalk amplitude level of the pilot signal f1 from T5 is held as a number.

The output of the number hold circuit 30 is input to the capstan servo circuit 34 as a tracking error signal. The capstan servo circuit 34 controls the speed of the capstan motor 36 so that the tracking error is zero. As a result, the running speed of the tape 10 is controlled,
1~Racking error is corrected.

According to the ATF device shown in FIG. 7, when the head A causes a leftward track deviation, the pilot signal crosstalk (2) from the track T3 increases, so a negative signal is held in the sample hold circuit 30. At this time, the capstan motor 36 increases its speed to correct the track deviation.

Furthermore, when the head A shifts to the right, the amount of pilot signal crosstalk from the track T5 increases, so ten signals are held in the sample and hold circuit 30. At this time, the capstan motor 36 slows down to correct the track deviation.

In this way, tracking control by ATF is performed.

[Problem that the invention seeks to solve]

In the R-DAT track format, tracking error detection requires A per track as described above.
This is only done at two locations: TFL and ATF2. Therefore, when a tracking error is detected, tracking control is performed by holding the error signal until the next tracking error is detected.

However, the time interval at which tracking errors are detected is not constant as shown in FIG.
The distance to F2 is 64.746°, and the distance from ATF2 to ATF1 of the next track is 115.254°, which is a difference of about 1:2. Therefore, the error signal detected by ATF2 is used for tracking control for about twice as long as the error signal detected by ATFI, and the influence of the error signal detected by ATF2 becomes stronger, resulting in tracking control. This causes an imbalance.

By the way, the head trace with respect to the track is the ninth
Ideally, they should be parallel as shown by solid line A in the figure, but in reality, manufacturing errors in the rotating head (waviness of the cylinder circumferential surface, bending or deviation of the rotating shaft, etc.) and unevenness in tape tension may occur. Due to deflection caused by, for example, an S-shaped undulation as shown by the dotted line B in FIG. 9, or a trace angle error as shown by the dashed line C in FIG. 9. To deal with such waviness and trace angle errors, there is a technique known as dynamic tracking that allows the head to properly follow the track by swinging the magnetic head in the width direction of the tape using a piezoelectric element built into the head on a rotating head. Although this type has been put into practical use in VTRs (video tape recorders), it has the disadvantage that the head configuration is complicated.

Therefore, if the vehicle does not have such a mechanism, it is inevitable that the vehicle will travel undulating or tilted, but it is necessary to be able to trace in the optimal condition. The optimal state is, as shown in FIG. 10, a state in which the head is positioned at the center of the track width at the longitudinal center of the track where the audio data PCM area exists. If traced in this manner, the head width is about 1.5 times the track width, so the PCM area can be read sufficiently and data loss can be kept to a minimum.

However, as described above, if the detection interval of the ATF signal is not constant, such an optimal state cannot be maintained. That is, in the state shown in FIG. 10, the dragging error signal is divided between ATFl and AT as shown in FIG.
The signs are opposite to F2 and the absolute values are almost the same, but the tracking servo is effective based on the temporal average value of the tracking error signal, so if the detection interval of the ATF signal is not constant, the average value will be zero. Therefore, the influence of the tracking error signal on the ATF2 becomes stronger. Therefore, tracking is performed in a direction that corrects more tracking errors in the ATF 2, and as a result, the head trace deviates from the center of the track as shown in FIG. In such a state, the range in which the head trace deviates from the PCM area increases, resulting in more missing PGM data, which impedes reproduction.

This invention solves the drawbacks in the conventional techniques, and
When tracking error signals cannot be obtained at regular intervals,
The present invention aims to provide a magnetic recording/reproducing device that can average the influence of tracking error signals and perform tracking in an optimal state.

[Means for solving problems]

This invention comprises means for transmitting the obtained tracking error signal to the tracking control system with a transmission gain that is approximately inversely proportional to the time interval when the points at which the tracking error signal is obtained are not equidistant on the time axis. It is something.

[For production]

According to the above configuration of the present invention, the transfer gain is low in the portion where the time interval in which the tracking error signal is obtained is long, and the transfer gain is high in the portion where the time interval is short. Therefore, even if the time intervals at which the tracking error signals are obtained are different, the influence on the tracking servo is approximately the same, and the head trace with respect to the track may, for example, undulate in an S-shape as shown in FIG. 9, or be inclined. Even in the case where the data is in the optimum state shown in FIG. 10, it is possible to stabilize the data in the optimum state shown in FIG. 10, and the data can be read with minimal loss.

〔Example〕

An embodiment in which this invention is applied to R-DAT is shown in FIG.

The system control 54 is composed of a microcomputer, and controls the operation of each part according to the contents of instructions from the operation keys 56 and state detection 58 within the device, and displays necessary information such as track number and time on the display 60. Let's do it.

The reference clock/timing generation circuit 64 generates various reference clocks and timing signals used in the signal processing system and the servo processing system based on the crystal oscillation output.

The rotating head 2 is attached to the circumferential surface of the cylindrical cylinder 1 by 180°.
Two magnetic heads A and B are installed at an interval of . This rotary head 2 is driven by a drum motor 28.

The rotating head 2 is equipped with an FG (frequency generator) for speed detection.
30, and a PG (phase generator) 32 for detecting a rotational reference position.

The capstan motor 34 has a motor shaft connected to the capstan 8.
The pinch roller 9 contacts the capstan 8 and runs the tape while regulating the tape speed. The capstan motor 34 has F for speed detection.
e12 is provided.

Reel motor 42 drives reel stand 48.50 via pulley 44.46 to wind up the tape. The loading motor 52 loads cassettes and tapes, and is driven via the drive 62 in response to instructions from the system control 54.

First, we will explain the parts that operate during recording.

Analog audio signals of left and right channels are input from input terminals 66 and 68. The recording level of these signals is adjusted by attenuators 70 and 72, pre-emphasis is applied by pre-emphasis circuits 74 and 76, and the signals are input to switches 78 and 80, respectively.

Switches 78 and 80 are connected to the RII side during recording.
The input analog signal is input to low pass filters 82 and 84. The low-pass filters 82 and 84 are for attenuating unnecessary high frequency components in the input signal to prevent aliasing due to sampling, and have a cutoff frequency of 1, which is about 172 of the sampling frequency. The low-pass filters 82 and 84 function as demodulation filters in the reproduction mode, as will be described later.

The level meter 86 displays the recording level and playback level.

The output analog signal of the low-pass filter 82.84 is input to a number hold circuit 88.90 and is set at a predetermined sampling frequency (48 k in the case of R-DAT mode ■).
Hz).

The sampling data is time-divisionally output by switching the switch 92 alternately so that the left and right channel data are outputted in a time-division manner, and the data is converted into digital data (16 bits per channel) by the A/D converter 94 and converted into PCM.

This PCM data is divided into upper and lower eight pits for each data, and is input to an interleave/FCC parity generation circuit 96. Here, interleaving (reordering data), parity generation (giving an error correction code), giving an ID code (identification code), etc.
8. Also, system control 5
A subcode is generated by a subcode generation circuit 100 based on information such as the track number and time outputted from the subcode generator 4.

PCM data is input to the 8-10 modulation circuit 102,
Each 8-bit data is converted to 10-bit data so as to satisfy specific conditions (namely, specifying the magnetization reversal interval within a certain range to narrow the band and make the DC component zero).

The block sync generation circuit 106 generates a block sync signal (see FIG. 5) arranged at the head position of each block, which is the basic unit of the track format.

Further, the ATF signal generation circuit 104 includes ATF1, ATF
The pilot signal f, so as to form each pattern of 2,
Sink signal f2. Generate f3 etc. Each of these signals is
In order to match the track format shown in FIG. 4,
The combination circuit 108 combines the signals. In this way, a series of data to be recorded on the track is generated.

The series of generated data is input to a switch 114 via a gain switching circuit 110 and a recording amplifier 112. The gain switching circuit 110 reduces the gain during the period in which the pilot signal f1 of the ATF signal is output based on the pilot flag 116 that rises during that period. The reason why the gain is reduced during the pilot signal section is that the frequency of the pilot signal is low, so if you record it with the same gain (i.e. the same recording current) as the others, only this part will be recorded abnormally strongly, and the next In order to prevent it from becoming more difficult to erase than others when overriding, etc.
The purpose is to weaken the recording current only in the section of the pilot signal. A recording amplifier 112 amplifies the data to a level necessary for recording on tape by the rotary head 2. switch 11
4 is connected to the "R" side during recording, and is connected to the recording amplifier 112.
The output is supplied to heads A and B of the rotary head 2, and a series of input data is recorded on tape.

In the recording mode, the drum servo circuit 118 uses the reference clock output from the reference clock/timing generation circuit 64.
Tsuku and FG30. The frequency and phase are compared with the rotation detection signal output from the PG 32, and the rotation of the drum motor 28 is controlled by the PLL IIJ control. The drum servo circuit 118 controls the data sent to the heads A and B and the PG 32 so that the data for one track output from the recording amplifier 112 is accurately recorded on one track on the tape as shown in FIG. The rotational phase of the rotary head 2 is controlled so that the detection timing of the rotary head reference position detected at is a predetermined timing.

The capstan servo circuit 120 operates at a specified tape speed (
The reference clock and the output of the FG 40 are compared in frequency and phase, and the capstan motor 34 is subjected to PLL rotation control so that the reference clock and the output of the FG 40 become 8.15JIII/S).

The reel servo 122 drives the reel motor 42 so that the tape does not slacken.

Next, the parts that operate during playback will be explained.

During playback, the switches 78, 80° 114 are all connected to the "P" side. The signals recorded on the tape are read by heads A and B and sent to switch 114.
The signal is input to the preamplifier 124 via. Preamplifier 1
The outputs of 24 are respectively supplied to a PCM path 126 for reproducing PCM data and a control path 128 for controlling tracking and the like.

The reproduced data supplied to the PCM path 126 is compensated for the frequency characteristics and phase characteristics of the heads A and B by the PCM equalizer 130 to open an eye pattern. The output of the PCM equalizer 130 is detected by the inversion detection circuit 132 as “i I
The waveform is shaped into a digital signal of I,'MQII. Further, the clock is recovered by the clock recovery circuit 134.

The waveform-shaped digital data is input to the block sync demodulation circuit 136, and the block sync signal is demodulated to identify the leading position of the data. Also, 10-8
The demodulation circuit 140 demodulates the data into the original upper and lower 8-bit data.

The error correction/dinterleap circuit 142 is connected to the memory 98
The reproduced data is deinterleaved and returned to the original arrangement via the 1500, and errors are corrected.

The error-corrected data is converted into 16 bits by combining the upper and lower 8 bits, and is returned to an analog signal by the D/A conversion circuit 144. This analog signal is separated into left and right channels, and unnecessary components are removed by deglitch circuits 146 and 148. Furthermore, switch 78.80
It is demodulated to the original audio signal by low-pass filters 82 and 84 through de-enf? cis circuit 150, 152
are subjected to gain phasing and guided to output terminals 154 and 156, respectively.

The subcode reproduced by the subcode reproduction circuit 158 is:
The data is sent to the system control 54 and used to display the track number and time on the display 60 and to perform searches.

The drum servo circuit 118 rotates at a specified speed in accordance with the reference clock as in the recording mode.

The reproduced signal sent to the control path 128 is input to the ATF sync detection circuit 160, and the sync signals f1 and f3 in the ATF signal are detected. Furthermore, the low-pass filter 164 extracts the crosstalk component of the pilot signal f1 of the left and right adjacent tracks in the ATF signal. The pilot level detection circuit 166 detects the levels of these crosstalk components and outputs the sync signal f.
, f , a tracking error detection circuit 168 detects a tracking error by calculating the difference between these levels using a timing signal generated from a timing generation circuit 170 based on the timing signals. The detected tracking error signal is
It is supplied to the capstan servo 120 via the VCA 174. The capstan servo 120 rotates the capstan motor 34 111t[l so that this tracking error becomes zero.

The ATF1/ATF2 discrimination circuit 176 detects the detected AT
The gain is switched by determining whether the F signal is ATF1 or ATF2. That is, as shown in FIG.
When ATF2 is detected, a high gain G1 is set, and when ATF2 is detected, a low gain G2 is set. Gain Gl,G
The ratio of 2 is inversely proportional to the time interval as G1:G2=t2:tl, where tl is the time during which the error signal obtained from ATFI is active, and t2 is the time during which the error signal obtained from ATF2 is active.

In this way, the tracking error signals obtained by ATFI and ATF2 have equal influence on the tracking servo. Therefore, even if, for example, the head trace undulates in an S-shape with respect to the track or is inclined, as shown in FIG.
The tracking error signal output from the CA 174 becomes as shown in FIG. 13, and its average level becomes zero, and the head trace can maintain the state shown in FIG. 10 without shifting as shown in FIG. 12. Therefore, PCM data can be read with minimal loss.

Note that the ATFI/ATF2 discrimination circuit 176, for example,
Using the fact that ATFI is in front of the PCM area and ATF2 is after the PCM area in one track, P
ATF1 and ATF2 can be determined depending on whether they occur before or after CMm[. Alternatively, if the output pulse of PG32 is obtained at the timing of the track start, the first ATF signal after the output pulse of PG32 is obtained is the ATF signal.
1. It is also possible to determine that the second ATF signal is ATF2.

The pilot frequency detection circuit 172 is used during a search and detects the pilot signal f1 in the ATF signal. During a search, it is sometimes necessary to read the track number and time information from the recorded content on the tape in order to advance or rewind to the target position.

In order to make this reading possible, the relative speeds of the heads A, 8 and the tape must be at a predetermined value that is approximately the same during recording, so the pilot signal f1 is used to control the speed. That is, the pilot signal f1 is 13
Since it is recorded at 0.67 kHz, the reel servo circuit 122 is controlled so that the pilot signal f1 detected during the search has this specified frequency. This allows the tape to be sent to the target position by reading the track number and time information on the length code.

(Example of modification) In the above embodiment, the present invention was applied to R-DAT, but recording and reproduction are performed using a rotary head incorporating a plurality of heads, and the recording and reproduction are performed based on the sync signal timing on the track. A VTR that detects and compares the pilot signal crosstalk components of adjacent left and right tracks and uses them as tracking error signals for automatic tracking control.
It can be applied to various magnetic recording and reproducing devices such as.

〔effect〕

As explained above, according to the present invention, the transfer gain is lowered in the portion where the time interval where the tracking error signal is obtained is long, and the transfer gain is increased in the portion where the R interval is short, so that the tracking error signal can be obtained. Even if the time intervals are different, the influence on the tracking servo is approximately the same, and even if the head trace with respect to the track has an S-shaped undulation or an angular error, it will remain stable. is tracked,
Data can be read with minimal loss.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to an R-DAT. FIG. 2 is a diagram showing the mechanism of R-DAT. FIG. 3 shows the tape format in R-DAT. FIG. 4 shows the track format in R-DAT. FIG. 5 shows the format of the PCM area in FIG. 4. FIG. 6 shows the format of ATF1 and ATF2 in FIG. 4. FIG. 7 is a block diagram showing an example of a conventional ATF device in R-DAT. Figure 8 shows AT in the track format of Figure 4.
FIG. 3 is a diagram showing the timing at which an F signal is obtained. FIG. 9 is a diagram showing a head trace with respect to a track. FIG. 10 is a diagram showing an optimal tracing state when the head trace has an angle with respect to the track. FIG. 11 is a diagram showing a tracking error signal when the head trace is in the state shown in FIG. 10 in the conventional ATF device shown in FIG. 7. FIG. 12 is a diagram showing a head trace using the tracking error signal of FIG. 11. FIG. 13 is a diagram showing the tracking operation in the embodiment of FIG. 1. 2... Rotating head, A, B... Magnetic head, 34.
・・Main 1st stan motor, 120・Capstan servo circuit, 168・Tracking error detection circuit,
174・VCA. Applicant Nippon Musical Instrument Manufacturing Co., Ltd. Figure 2 Figure 3 Figure 9 Figure 1O Figure 1I Figure 12 Figure 13

Claims (1)

[Claims] Recording and reproduction are performed using a rotating head that incorporates multiple heads, and the pilot signal crosstalk components of the left and right adjacent tracks are detected and compared based on the sync signal timing on the track, and are used as a tracking error signal for automatic tracking control. In the magnetic recording/reproducing device configured as above, when the points at which the tracking error signals are obtained are not equidistant on the time axis, the obtained tracking error signals are transmitted to the tracking control system with a transmission gain that is approximately inversely proportional to the time interval. A magnetic recording and reproducing device comprising means.