JPH0644367B2 - Tracking signal detection and control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical scan type magnetic recording / reproducing apparatus having a rotary head, and more particularly to a video tape recorder and a P recorder.
The present invention relates to a tracking signal detection and control circuit suitable for tracking control of a CM recorder.

[Background of the Invention]

The rotary head type magnetic recording / reproducing apparatus is widely used as a consumer device such as a video tape recorder and an audio PCM recorder. The rotary head type magnetic recording / reproducing apparatus forms and records an oblique track on a magnetic tape as a recording medium. Further, in order to increase the recording density, no guard band is provided between the adjacent tracks, and crosstalk from the adjacent tracks during reproduction is reduced by causing the azimuth angle of the recording / reproducing head to be different between the adjacent tracks and by azimuth loss. .

In such a rotary head type magnetic recording / reproducing apparatus, the reproducing head needs to accurately trace the track recorded on the magnetic tape, and the tracking control for controlling it plays an important role.

Conventionally, tracking control of a video tape recorder is performed by using a dedicated track for recording a control signal for control. This method does not interfere with the image signal, which is the main signal, but requires a tracking control head and a dedicated area on the magnetic tape, and is different from the track on which the main signal is actually recorded. However, there is a hardware and performance defect that the performance is not suitable for high density recording and reproduction.

In order to improve this, as a conventional method that does not require a control signal recording track, a track formed by the rotary head is provided with an area for recording a pilot signal,
There is a method of detecting a tracking shift amount by a crosstalk component of a pilot signal from an adjacent track and controlling the tracking. FIG. 1 shows an example of a recording pattern of pilot signals formed on a track, and FIG. 2 shows a block diagram of a conventional tracking signal detection and control circuit.

In FIG. 1, A ₀ , A ₁ , and A ₂ are tracks recorded by a head having an azimuth angle of + 20 °, and B ₀ , B ₁ , and B ₂ are tracks recorded by a head having an azimuth angle of −20 °. . Further, 1 is a head having an azimuth angle of + 20 °, and the head width is 1.5 times wider than the track pitch.
°, 90 °, and 180 ° indicate the position of the head when the tracking error is the value. The hatched area in Fig. 1 is
In the area where the pilot signal is recorded, _P and _B are
The frequency is shown, _P is a frequency with a small azimuth loss effect, and _B is a frequency with a large effect.
2 in FIG. 2 is an input terminal for applying a signal reproduced from the head, 3 is an amplifier circuit for amplifying the reproduced signal, and 4 is a frequency.
A low-pass filter that passes _P and cuts _B (hereinafter L
PF), 5 is an envelope detection circuit for detecting the envelope of the output of the LPF 4, 6, 7 is a sample hold circuit (hereinafter referred to as SH) for holding the output of the envelope detection circuit 5, and 8 is in the figure. An adder circuit for adding according to the suffix No., 9 is an output terminal for outputting a tracking error signal, 10 is a bandpass filter (hereinafter referred to as BPF) for passing the frequency _B and blocking _P , 11 is an envelope detection circuit, and 12 is A comparator that compares the output signal of the envelope detection circuit with the voltage Vth to obtain digital signals of "1" and "0", 13 is a rising detection circuit that detects a rising edge of the output of the comparator 12, and 14 is a rising detection circuit.
A delay circuit that delays 13 output pulses. The circuit operation in FIG. 2 will be described with reference to the waveforms in each state of the frequencies _{P 1} and _P 2 in FIG.

In Fig. 1, head ₁ tracks A ₁ track with tracking error 0
When ° trace, the output of the LPF4 of FIG. 2, as indicated by _P in FIG. 3 (a), after _{the P} component of A ₁ track appears, B ₁ track and since azimuth loss effect is small The _P component from the B ₀ track appears as crosstalk. The output of BPF10, since the azimuth loss effect is large, _B components from B _1, B ₀ track, hardly appear, the A ₁ track as indicated by _B of FIG. 3 (a)
_B component appears. The frequency _P and _B components are line-detected by the envelope detection circuits 4 and 11 shown in FIG. The comparator 12 outputs a "1" level when the frequency _B component becomes equal to or higher than the voltage Vth, and the rise detection circuit
At 13, the rising edge is detected. Therefore, Fig. 3 (a)
As shown in, the component of the frequency _P is the crosstalk component from the track B ₁ during the time when the output pulse of the rising edge detection circuit 13 appears. That is, the voltage held at SH7 in FIG. 2 is the crosstalk amount from the B ₁ track. Further, the delay circuit 14 delays the output pulse of the rising edge detection circuit 13 to hold the amount of crosstalk from the B ₀ track in SH6.

Next, when the head 1 causes a + 90 ° tracking error, the head traces many B ₁ tracks.
As shown in FIG. 3 (b), the crosstalk component from the B ₁ track increases, and the voltage held in SH7 of FIG. 2 increases. On the contrary, when the tracking error is −90 °, the crosstalk component from the B ₀ track increases and the voltage held in SH6 rises. Therefore, an error voltage corresponding to the tracking error appears in the output of the adder circuit 8. Tracking control is performed by feeding back this error voltage signal to a tape feeding motor. However, Figure 3
As shown in (c), when the tracking error is + 180 °, the frequency _B component is the comparison voltage Vth of the comparator 11.
A situation occurs in which only a lower level is output. In such a state, since the SH6 and 7 sample pulses are not output in the circuit of FIG. 2, the output of the error signal becomes indefinite. As described above, the circuit configuration of FIG. 2 has a dead zone area in which an error signal cannot be output in response to a tracking error. Due to this, if the dead zone area is entered at the rise of tracking control, the lock time becomes long. There is a drawback that it ends up.

As a method of eliminating this drawback, a digital circuit determines that the output pulse of the rising edge detection circuit 13 of FIG. 2 has not been output within a certain period of time, and when the pulse is not output, the error is forced. It is easily conceivable that a circuit for externally adding the signal output to the terminal 9 may be added.
However, when scratches occur on the tape and the recording pattern of FIG. 1 disappears, the output of the rising edge detection circuit 13 is not output and the additional circuit operates in the same manner as described above, and the scratches are accelerated in the direction of increasing the tracking error, resulting in scratches. If there is, it causes a track jump,
There is a drawback that main signals such as PCM signals are deteriorated.

[Object of the Invention]

An object of the present invention is to provide a device that detects a stable tracking signal without malfunction and to perform control without a dead zone.

[Outline of Invention]

It is determined that the timing at which the frequency fp having a small azimuth loss effect is detected and the timing at which the frequency fB having a large azimuth loss effect is detected are output within a predetermined time determined by the recording positions of the respective frequencies fp and fB. When it is determined that the timing is correct, the error signal detected by the error signal detecting means is output and output.
It outputs a stable tracking signal with no malfunction.

Then, when it is determined in this determination that the timing is incorrect, the dead zone can be removed by performing an operation of switching the tracking signal to a constant voltage.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. Fourth
In the embodiment shown in the figure, when the head should trace the A ₀ , A ₁ , A ₂ tracks in FIG. ₁ , the B ₀ , B ₁ tracks are traced, and the dead zone is detected within a predetermined time after the _P detection pulse. It is to determine whether the detection pulse of _B is detected in the above, and to identify whether it is a dead zone or dropout. ₁₅ is compared with the voltage Vth ₁₅ of the output of the envelope detection circuit 5 of _P component, and "1", "0"
16 is an AND circuit, and 18 is a head for tracing A ₀ , A ₁ , A ₂ tracks, that is, a "1" level when the head of + 20 ° azimuth is tracing, a -20 ° azimuth of A terminal to which a switch signal that becomes "0" level is added when the head is tracing,
17 is a monostable multivibrator that generates a timing gate pulse to determine whether the _B component is detected after detecting the _P component, and 19 is a rising edge that detects the falling edge of the output pulse of the monostable multivibrator 17. Down detection circuit, 20 is an AND circuit, 21 is when _B component is detected,
A monostable multivibrator for generating a gate pulse for inhibiting the output pulse of the fall detection circuit 19, 25
Is an inverter circuit, 26 is an AND circuit, 22 is an RS latch that can be set and reset, 23 is a power supply for forcibly applying the error signal voltage, 24 is a switch for applying the above voltage to the terminal 9, and the RS latch 22 is When "1", on the 24A side,
When it is "0", it is connected to the 24B side. Regarding other symbols, the same symbols as those in FIG. 2 are the same circuits and perform the same operation.

The operation near the on-track in the operation of FIG. 4 will be described with reference to the timing chart of FIG. The reference numerals on the left side of FIG. 5 correspond to the reference numerals of the circuits in FIG. 4 and show the output waveforms of the respective portions. Track A ₁ shown in Fig. ₁
When the head 1 traces, the "1" level is applied to the terminal 18, the AND circuit 16 is turned on, and the outputs of the LPF 4 and the BPF 10 are the same as those shown in FIG. As shown in 10, the crosstalk components from the adjacent tracks B ₀ and B ₁ appear in addition to the pilot signals _P and _B of the A ₁ track. _The output of the LPF 4, which outputs the _P component, detects the line wrapped by the envelope detection circuit 5, and becomes the waveform of FIG. 5, which is added to SH6 and 7 and to the comparator 15. In comparator 15, voltage Vth
_As compared with 15, the waveform shown in FIG. 5 is output and applied to the monostable multivibrator 17 via the AND circuit 16. In the monostable multivibrator 17, as shown in FIG. 5, the pulse width is output triggered by the first rising edge of the _P component,
It joins the AND circuit 20, gates the output of the rising edge detection circuit 13, and joins the falling edge detection circuit 19 to output the waveform of FIG. On the other hand, the output of the BPF 10 for detecting the _B component detects the line wrapped by the envelope detection circuit 11,
The waveform shown in FIG. 11 is obtained, and the comparator 12 compares it with the voltage Vth to obtain the output shown in FIG. The rising edge detection circuit 13 detects the rising edge of the output of the comparator 12 and outputs a detection pulse to SH.
In addition to the sample pulse of 7, the pulse of FIG. 5 delayed by the delay circuit 14 is added as the sample pulse of SH6. The output pulse of the rising edge detection circuit 13 sets the RS latch 22. Since the output of the AND circuit 20 gates the pulse of the rising edge detection circuit 13 by the monostable multivibrator 17, the output of FIG. 5 is obtained and added to the monostable multivibrator 21. The monostable multivibrator 21 has the pulse width shown in FIG. 5 and is added to the AND circuit 26 via the inverter 25. The AND circuit 26 receives the negative phase signal of the output of the monostable multivibrator 21 and the output of the fall detection circuit 19. Therefore, the output of the AND circuit 26 continues to be the "0" level output as shown in FIG. 5 and the reset signal of the RS latch 22 is not added. According to the above operation, the RS latch 22 is supplied with a pulse from the rising edge detection circuit 13 as a set pulse, but the reset pulse is not supplied from the AND circuit 26.
Output becomes "1" level, the switch 24 selects the 24A side, and outputs the output of the adder circuit 8 to the terminal 9 as the error signal voltage as in the circuit of FIG. Thus, in the vicinity of on-track, the circuit of FIG. 4 outputs the error signal voltage similar to that of FIG.

Next, the operation near the reverse tracking of the operation of FIG. 4 will be described with reference to the timing chart of FIG. 6 is different from FIG. 5 in that the _B component has a large azimuth loss effect, so the _B component of the track B ₁ of the reverse azimuth is not detected, and no pulse appears in the output of the comparator 12, and as a result, No pulse appears in each output of the rising edge detection circuit 13, the delay circuit 14, the AND circuit 20, and the monostable multivibrator 21. Therefore, the output of the inverter 25 becomes "1" level, and the output of the AND circuit 26 is as shown in FIG.
The pulse of the fall detection circuit 19 appears, and the RS latch 22 is reset. Therefore, since the set pulse is not supplied to the RS latch 22 and the RS latch 22 is reset, the output becomes "0" level, the switch 24 selects the 24B side, and outputs the voltage of the power source 23 to the terminal 9 as an error signal voltage.

As described above, when the sample pulse is not output in the vicinity of the reverse tracking, the switch 24 is switched and the error signal voltage is forcibly applied to eliminate the dead zone. On the other hand, when the pattern of the pilot signal of FIG. 1 is missing due to scratches on the tape, the circuit operation of FIG.
Since the output signals of the LPF4 and BPF10 of 10 are missing, the output pulses of the comparators 15 and 12 cannot be obtained, the sample pulse is not output, and the set / reset pulse added to the RS latch 22 is not output. Hold the data obtained from time to time. Therefore, in the conventional dropout, the circuit for removing the dead zone operates and the error signal voltage is accelerated in the direction of increasing the tracking error.However, according to the present invention, the dead zone can be removed, and the malfunction at the time of the dropout can be prevented. There is an effect that there is no.

In the description of the above embodiment, the comparator 15 and the comparator 12
The comparison voltages Vth ₁₅ and Vth of are as shown in FIGS.
Although it is set to 1/2 of the level of A ₁ in FIG. 5, the Vth ₁₅ is set to a lower voltage and the levels of B ₁ and B ₀ are detected. The waveform of the monostable multivibrator 17 triggered by the first rising edge of the comparator 15 does not change only by changing the pulse width of 15
There is no change in operation even when Vth ₁₅ is lowered. Further, the level when the frequency _P component with less azimuth loss effect is reproduced from the reverse azimuth head is the same as the level reproduced from the forward azimuth head, as shown by B ₁ in FIG. However, even if the frequency _P has some azimuth loss effect and the level of B ₁ in FIG. 6 is small, it can be dealt with by lowering the comparison voltage Vth ₁₅ of the comparator 15, and the basic operation does not change. .

Although monostable multivibrators 17 and 21 are used to obtain the gate pulse in the embodiment of FIG. 4, this does not limit the present invention, and even if an equivalent pulse is obtained by the counter, The operation in the figure does not change. Further, in order to forcibly obtain the error signal voltage, the switch 24 and the power supply 23 are used, but instead of the power supply 23, a pulse obtained by delaying the rising edge of the output pulse of the comparator 15 shown in FIG.
The circuit operation of FIG. 4 does not change even if a voltage that samples and holds the crosstalk amount from the B ₁ track of the envelope detection circuit 5 is applied. The switch 24 is inserted between the adder circuit 8 and the output terminal 9 in the embodiment shown in FIG. 4, but for the purpose of forcibly adding the error signal, the switch 24 is inserted between the SH7 and the adder circuit 8. Alternatively, it is obvious that the same operation can be performed by inserting it between SH6 and the adder circuit 8.

In the embodiment of FIG. 4, the circuit operated when the + 20 ° azimuth head traces on the tape, but the present invention operates when the -20 ° azimuth head traces B ₀ , B _{1 of} FIG. An example of is shown in FIG.

In FIG. 7, 27 is an inverter, 28 is a fall detection circuit, and other circuits having the same reference numerals as those in FIG. 4 have the same circuit configuration and perform the same operation. In FIG. 7, the terminal 18 has a fourth
Similar to the figure, a signal that becomes "1" when the + 20 ° azimuth head is tracing and "0" level when the -20 ° azimuth head is tracing is added. Track B shown in Fig. 1 _{When controlling 0} to be traced by the -20 ° azimuth head, a "0" level is applied to the terminal 18, and the output of the comparator 15 is applied to the fall detection circuit 28 via the AND circuit 16. The operation in the vicinity of on-track in the operation of FIG. 7 will be described with reference to the timing chart of FIG.

The reference numerals attached to the left side of FIG. 8 correspond to the reference numerals of the circuits in FIG. 7 and show the output waveforms of the respective portions.
When the -20 ° azimuth head traces the track B ₀ shown in FIG. 1, the output of LPF4 and BPF10 becomes 8th.
As shown in FIGS. 4 and 10, in addition to the pilot signals _P , _B of the B ₀ track, the crosstalk component from the adjacent tracks A ₀ , A ₁ appears. _The output of the LPF 4, which outputs the _P component, detects the line wrapped by the envelope detection circuit 5 and becomes the waveform of FIG. 8 and is added to SH6 and SH7.
Join the comparator 15. In comparator 15, voltage Vth
The waveform shown in FIG. 8 is output in comparison with _15, and is applied to the fall detection circuit 28 via the AND circuit 16. The output of the fall detection circuit 28 has the waveform shown in FIG. 28 and is applied to the AND circuit 26.
On the other hand, the output of the BPF 10 for detecting the _B component detects the line wrapped by the envelope detection circuit 11 and has the waveform shown in FIG. 8, and the comparator 12 compares it with the voltage Vth to obtain the waveform shown in FIG. In the rise detection circuit 13, the comparator 12
The rising edge of the output of the
7 sample pulses, delay circuit 14, monostable multivibrator 17 and RS latch 22 set inputs. The output of the delay circuit 14 delays the input pulse at the timing of FIG. 14 and adds it as a sample pulse of SH6. The monostable multivibrator 17 outputs the pulse width shown in FIG. 17 and is applied to the AND circuit 26 via the inverter 25.
That is, since the opposite phase signal of FIG. 8 and the pulse of 28 are applied to the input of the AND circuit 26, no pulse is output to the output of the AND circuit 26 as shown in FIG. Therefore, the output of the RS latch 22 is the rising detection circuit 13
The output of the adder circuit 8 is output to the terminal 9 as the error signal because the switch 24 selects the 24A side because it is set by. From the above operation,
As the operation of FIG. 7 near the on-track, an error signal voltage similar to that of FIG. 2 is obtained.

Next, the operation in the vicinity of the reverse tracking of the operation of FIG.
This will be described with reference to the timing chart in the figure. In FIG.
The difference from FIG. 8 is that the _B component has a large azimuth loss effect, so the _B component of the track A ₁ of reverse azimuth is not detected and the output pulse of the comparator 12 does not appear.
No pulse appears in each output of the rising edge detection circuit 13, the delay circuit 14, and the monostable multivibrator 17. Therefore,
The output of the inverter 25 goes to "1" level and the AND circuit
At the output of 26, as shown in FIG.
Pulse appears and resets the RS latch 22. Therefore, the output of the RS latch 22 is reset by the AND circuit 26 and becomes an output of "0" level, the switch 24 selects the 24B side, and the voltage of the power supply 23 is output to the terminal 9 as an error signal.

As described above, in the dead zone where the sample pulses are not output to SH6 and SH7 in the vicinity of the reverse tracking, the switch 24 is switched and the error signal voltage is forcibly added to eliminate the dead zone.
When the pilot signal pattern shown in FIG. 1 is missing due to scratches on the tape or the like, the LPF4,
Since the output signal of the BPF 10 is missing, the data obtained at the previous trace is retained. Therefore, the circuit of FIG. 7 has an effect that the dead zone can be removed and there is no malfunction at the time of dropout as in the case of FIG.

Although the embodiments of the present invention in which two heads of + 20 ° azimuth operate independently are shown in the embodiments of FIGS. 4 and 7, the same applies to the combination of the configurations of FIGS. 4 and 7. The effect is obtained. FIG. 10 shows an embodiment in which the embodiments of FIGS. 4 and 7 are combined.

16A in FIG. 10 corresponds to the AND circuit 16 in FIG.
It corresponds to the AND circuit 16 in FIG.
A, 17B monostable multivibrator, 25A, 25B inverter, 26A, 26B AND circuit, 22A, 22B RS
The same applies to the latch. Also, 29 is an OR circuit, which is an RS latch.
The switch 24 is controlled by taking the OR of 22A and 22B.
Therefore, in the embodiment of FIG. 10, RS latches 22A, 22
Only when both B are at "0" level, the switch 24 is connected to the 24B side to forcibly generate the error signal voltage. That is, according to the embodiment of FIG. 10, when the head of + 20 ° azimuth is tracing the A ₁ track of FIG. _1, it is possible to drop out only the area where _{B of} the A ₁ track is recorded. , Even if the RS latch 22A becomes "0", there is no dropout when the -20 ° azimuth head traces the B ₀ and B ₁ tracks.
The latch 22B is "1", and the error signal voltage is added by the adder circuit 8
Will be output. Therefore, there is an effect that a malfunction does not occur even for the small dropout as described above.

As described above, in the embodiment of the present invention, the pilot signal is recorded in one area of the track as shown in FIG. 1. However, a plurality of the same patterns as those in FIG. 1 are recorded on the track. The operation of this embodiment is the same for all the products. When the pilot signals are recorded at multiple points, the RS latch shown in FIG. 10 is used in all pilot signal areas on the track to ensure the operation.
It is conceivable to determine that 22A and 22B have become "0" level and connect the switch 24 to the 24B side. In the above circuit, for example, RS latches corresponding to 22A and 22B in FIG. 10 are provided by the number of areas recorded on the track, a pulse indicating each area is externally applied, and this pulse sets the plurality of RS latches. , It can be realized by switching the reset pulse and taking the OR of the outputs of all RS latches.

〔The invention's effect〕

According to the present invention, the tracking signal can be detected stably without malfunction as compared with the timing when only the frequency fB is detected.

In addition, there is an effect that the dead zone that has been present can be removed.

[Brief description of drawings]

FIG. 1 is a diagram showing a recording pattern of pilot signals, and FIG.
FIG. 3 is a diagram showing a conventional tracking signal detection and control circuit, FIG. 3 is a timing diagram showing the operation of FIG. 2, FIG. 4 is a diagram showing one embodiment of the present invention, FIG. 5 and FIG. FIG. 4 is a timing chart showing the operation, FIG. 7 is a diagram showing another embodiment of the present invention, FIGS. 8 and 9 are timing charts showing the operation of FIG. 7, and FIG. It is a figure which shows another Example. 1 ... Head, 4 ... Low-pass filter, 10 ... Band-pass filter, 5, 11 ... Envelope detection circuit, 13,15 ... Comparator, 17, 21 ... Monostable multivibrator, 19 ... Fall detection Circuit, 14 ... Delay circuit, 22 ... RS latch, 28 ... Fall detection circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Furihata 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Home Appliances Research Institute, Hitachi, Ltd. (72) Inventor Fujio Okamura 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Ceremony Company, Home Appliance Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-60-124047 (JP, A)

Claims (1)

[Claims] 1. A frequency f having at least two rotating magnetic heads having different azimuth angles and having a small azimuth loss effect.
p and the frequency fB having a large azimuth loss effect are stored at different positions on the track of the recording medium, and the timing at which the frequency fp is detected in the tracking signal detection and control device using the reproduced signals of the frequencies fp and fB at the time of reproduction is First timing detecting means for generating, second timing detecting means for generating timing at which the frequency fB is detected, and outputs of the first and second timing detecting means are recorded at respective frequencies fp and fB. A discriminating means for discriminating that the timing is output within a predetermined time determined by the position and the timing is correct, and an error for taking in and holding the crosstalk amount from the adjacent track of the frequency fp based on the detected timing of the frequency fB. When it is determined that the output of the signal detection means and the output of the determination means are at the correct timing, The error signal detection means outputs the error signal captured and held, and when the determination means detects the frequency fp and the frequency fB is not detected within a predetermined time, it determines that the timing is incorrect and outputs a constant voltage. A tracking signal detection and control device comprising a control means.