JPS6212564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for reproducing signals recorded on a tape-shaped recording medium according to recording tracks arranged substantially parallel to each other and obliquely to the long axis of the recording medium. Two reproducing elements per readout alternately read the recording track in succession, mutual positions of the reproducing elements in a direction transverse to the recording track can be controlled, and furthermore, the recording track is connected to the two reproducing elements. The present invention relates to a method for positioning a reproducing element in a signal reproducing device, in which the regenerated signal, if read continuously and correctly, contains pilot signals always located at the same nominal time interval.

Such a positioning method is described in Dutch patent application no.
It is also known from No. 7409513. In devices for recording information on adjacent tracks on a record carrier and subsequently reading the information, in particular video signal recording and reproducing devices in which the record carrier is passed in a helix around a drum and is scanned by a rotating head. , it is necessary that the reading head accurately follows the desired track during the reading period. In order to increase the information density, the distance between tracks is increasingly narrowed, and writing is performed so that the tracks are directly adjacent to each other so that there is no intermediate space.Furthermore, at the same time, the track width is increasingly narrowed, and has already reached a width of about 30 μm. Since many tracks are being used and there is a tendency to further narrow the already significantly narrowed track widths, it is even more desirable for the recording head to accurately follow the desired track. Slight deviations of the read head from the correct track directly result in unacceptable crosstalk from adjacent tracks.

According to this known method, a pilot signal recorded on a track is read, and this pilot signal is used to control the position of the reproducing element relative to the center of the track that the reproducing element is reading. .

The disadvantage of this known method is that the position error may correspond to one track width, or if the pilot signals within a group of tracks can be distinguished from each other, it may not be detected and the position error may correspond to several track widths. The point is that there are things you can do. Using this known method, it is also possible to control the read element to center it on the wrong track.

It is an object of the present invention to provide a method for relative positioning of read elements so that they scan a track in succession.

For this purpose, the present invention provides for detecting a pilot signal in the reproduced signal, measuring the time between the occurrences of said pilot signal in each pair of successively read recorded tracks, and If the recorded time deviates from a predetermined nominal time by a predetermined amount, the relative positions of the two reproducing elements in the lateral direction with respect to the recording track are corrected.

The invention provides that the tracks are arranged diagonally on the tape so that the time difference between two sequentially read pilot signals depends on the number of tracks located between the two sequentially read tracks;
The nominal times are two directly adjacent to each other on the tape.
This is done taking into account that this corresponds to the time difference between the successive readings of two tracks and that in the case of two-head video recording devices said time difference is equal to the time of half a revolution of the head drive and equal to the duration of one video field. It is something that In this case, the pilot signal in the track can be an independent signal that can be distinguished from the information signal, but these signals can also be, for example, vertical synchronization pulses.

In measuring the time difference, according to the present invention, the first
measuring the duration of a first time interval between a reference instant and the detection of a subsequent pilot signal;
measuring the duration of a second time interval between a second reference instant which differs from said first reference instant by a predetermined nominal time and the detection of a subsequent pilot signal; Preferably, the difference in duration between two time intervals is determined.

Thus, according to the invention, it is not necessary to measure the entire time between the occurrences of two successive pilot signals.

In generating the control signal, in a preferred embodiment of the present invention, the first signal is generated when the difference between the durations of the first and second time intervals exceeds a predetermined magnitude; A second signal can be generated representing the polarity of the difference between the durations.

Furthermore, the present invention provides a first and a second recording medium for reproducing signals recorded on a tape-shaped recording medium according to recording tracks arranged substantially parallel to each other and obliquely to the long axis of the recording medium. The first and second reproducing elements move continuously in a direction oblique to the long axis of the recording medium, and transversely to the direction of movement of the first and second reproducing elements. The present invention relates to an apparatus for carrying out a method for positioning a reproducing element, comprising positioning means for controlling the positions of the first and second reproducing elements in a direction.

According to the invention, such a positioning device
and a detection circuit for detecting the occurrence of a pilot signal in the signal reproduced by the second reproduction element and a measurement for determining the time interval between the detected occurrences of two successive pilot signals. a comparison circuit for comparing said time interval with a predetermined nominal time; and a control for providing a control signal to said positioning means when said measured time interval deviates from said nominal time by a predetermined amount. It is characterized by comprising a circuit.

In practicing the invention, the control circuit generates a first level signal when the time error measured by the integrating element and the comparator circuit is of a first polarity, and the control circuit generates a first level signal to the comparator circuit. signal means for generating a second level signal when the measured time error has a polarity opposite to said first polarity; and when said measured time interval deviates by a predetermined amount. A switching element may be provided for supplying the signal to the integrating element.

In this way, the control signal is generated by an integral method, and this control signal continues to increase or decrease as long as a time error is detected, and maintains its value as soon as the relative positions of the two reproduction elements are correct.

In a preferred embodiment of the present invention, a second switching means is provided between the control circuit and the positioning means, and the second switching means is arranged so that the reproducing element controlled by the positioning means receives a signal from the recording medium. It can be configured to remain open during playback time.

In yet another embodiment of the invention, the detection circuit comprises a pulse shaper for shaping pulses in synchronization with the detected pilot signal;
Furthermore, said measuring circuit comprises a first pulse generator for generating pulses in which the time interval between the occurrences of two successive pulses is equal to said nominal time; the duration of a first time interval between the appearance of one pulse and the appearance of another first pulse generated by the pulse shaper and following the first pulse by the first pulse generator; measuring the difference in duration of a second time interval between the occurrence of a second pulse generated and the occurrence of another second pulse generated subsequent to said another first pulse by said pulse shaper; and a duration difference measuring circuit.

In the practice of the present invention, the measuring circuit includes a counting pulse generator for generating counting pulses having a repetition frequency relatively higher than a repetition frequency of pulses from the first pulse generator;
and a gate circuit for forwarding the counting pulses during a second time interval, for counting the counting pulses in a first counting direction during the first time interval, and for transferring the counting pulses in a first counting direction during the second time interval. and a switchable counter for counting in the opposite direction.

In carrying out the invention, the measuring circuit further comprises a bistable circuit, and set and reset input terminals of the bistable circuit receive pulses from the pulse shaper and pulses from the first pulse generator. Preferably, the gate circuit is controlled by the output signal of the bistable circuit.

Further in an embodiment of the invention, the comparator circuit is configured to determine that the count value of the switchable counter at the end of each second time interval is such that the time interval between the occurrences of two successive pilot signals is equal to the nominal time. A decoding circuit may be provided for generating a first signal when the reference position is deviated by a predetermined amount from a reference position reached when the position is equal, and a second signal representing the polarity of the deviation.

In a preferred embodiment of the present invention, in supplying the first and second signals to the control circuit having the integrating element, the first switching means is actuated by the first signal and the signal means can be controlled by the second signal.

Since the count value of the switchable counter changes continuously during a counting cycle, the comparator circuit determines the values of the first and second signals based on the command of a clock pulse that always occurs at the end of the second time interval. and a memory circuit for receiving and storing these values until the appearance of the next clock pulse and providing the stored values of the first and second signals to the first switching means and the signal means. suitable.

Therefore, a simple circuit can be selected for the decoding circuit. This is because the output signal is not provided to the memory circuit until after the end of each counting cycle. If the detection circuit does not detect the pilot signal, an incorrect error signal may be generated at the end of the counting cycle. To prevent this from occurring, in the present invention the switchable counter includes a device for detecting whether the counting limit of the switchable counter has been exceeded and inhibiting the supply of the next clock pulse to the memory circuit. It can be equipped.

If no pilot signal is detected, the supply of counting pulses to the counter is not prevented, so that one of the two counting limits will be exceeded.

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

FIG. 1 shows a record carrier 1 in the form of a tape, which is assumed to be moving in the direction of the arrow 2 at a constant speed. This tape 1 is passed around the drum in a helical manner in a known manner, although not shown. The drum is equipped with two diametrically opposed magnetic heads 4 and 5 which can be brought into mechanical contact with the magnetic tape 1 through a gap in the drum. The tape passes part way around the drum so that each head contacts the tape every half revolution. In this way, information can be written in tracks on the tape. These information tracks are arranged parallel to each other and obliquely to the tape axis. FIG. 1 schematically shows a number of tracks T ₁ to T ₇ . In the situation shown in FIG. 1, head 5 reads track _T3 . After the head 5 reaches the end of the track _T3 , the head 4 reaches the starting point of the track _T4 and starts the track _T3.
This track continues with the information continued from.

These tracks are not always perfectly linear, and in order to obtain a still image, both heads 4 and 5 are placed on an information track to enable continuous reading when the tape 1 is stationary. It is known to control the information so that these heads always follow the center of the information track. Many systems for this purpose are known, one method being disclosed in a previous Dutch patent application.

Generally, these fine tuning systems are unable to identify which track or set of tracks is being followed. In this case, head 4 may be offset from head 5 by a height H, so that head 5 is on track T ₃
There is a possibility that the head 4 starts reading some track other than track _T4 following track _T3 after reading T3, which is undesirable.

According to the present invention, such deviations can be detected by providing the information track with a pilot signal that is distinguishable in amplitude, frequency and/or time from the information written on the track. In that case, these pilot signals should be located at the same time interval from the start point of the track, and it is preferable that these pilot signals be of burst type. These signal bursts are designated B ₁ through B ₇ in FIG.

FIG. 2 is a diagram showing the time relationship of the signals read by heads 4 and 5. Figures 2A-2G show the burst signals read by heads 4 and 5, respectively, as they read tracks T1- _T7 , _respectively . These burst signals are therefore read at the instants t ₁ to t ₇ respectively.

Assume that when head 5 reads track _T3 , head 4 should read track _T4 . In that case, the burst signal B ₄ is read at instant t ₄ . This time _t4 occurs exactly one half revolution after the time when the head 5 reads the burst signal _B3 . If the head 4 reads the wrong track, the instant the burst signal _B3 is generated and the head 4 reads the wrong track.
The time difference dT between the instant of occurrence of the burst signal read by dT is not equal to 1/2T. From the difference between this time difference dT and the half-rotation period, a signal representing how many tracks the error of head 4 with respect to head 5 corresponds to can be derived. FIG. 3 shows this difference dT-1/2T as a function of the track read by head 4.

FIG. 4 is a block diagram showing one embodiment of a circuit for measuring the time difference dT-1/2T and deriving a servo signal from it. Further, FIG. 5 is a waveform diagram showing a large number of signal waveforms for explaining the operation of the circuit of FIG. 4. This circuit comprises a reading device 6 for reading the signals recorded on the tape, and therefore this circuit comprises two heads 4 and 5. The output signal S ₁ of this device 6 is shown in FIG. 5A. In this signal S ₁ , the burst signal is instantaneous
It appears at t ₃ , t ₆ , t ₁₀ and t ₁₃ . In this case, these burst signals differ in amplitude from the rest of the signal _S1 . The output of this device 6 is connected to the input of a pulse shaper 7, for example an am demodulator in series with a threshold circuit for forming the pulses. In this example, this pulse is a pulse with a duration equal to the duration of the burst signal. However, these pulses can also be synchronized with the beginning or end of a burst signal to form short pulses of constant duration. The output signal _S2 of this pulse shaper 7 is shown in FIG. 5B.

In order to be able to determine the time error dT-1/2T, the circuit comprises a pulse generator 9 which generates pulses at time intervals 1/2T, ie every half revolution. FIG. 5C shows this pulse train _S3 . To obtain correct measurements, this pulse generator must be synchronized so that under all conditions the pulses from this pulse generator always precede or always follow the reading of the burst signal. It is necessary to follow the instructions.

This signal S ₃ is supplied to the set input terminal of flip-flop 8, and the signal S ₂ is supplied to the set input terminal of flip-flop 8.
Supplied to the reset input terminal of the The output signal of flip-flop 8 is shown in FIG. 5D.

In this case, the duration difference between two successive output pulses of flip-flop 8 is equal to the time error dT-1/2T to be determined. To give an example, the difference in duration of the pulses appearing at instants _t2 and _t5 , respectively, is ( _t6 - _t5 )-( _t3 - _t2 ). i.e. pulse train
For S ₂ , t ₆ - t ₃ = dT, and for pulse train S ₃ , t ₅ - _{t 2} = 1/2T, so (t ₆ - t ₅ ) - (t ₃
−t ₂ )=dT−1/2T.

To measure the time error, the circuit comprises a pulse generator 10 for generating relatively high frequency counting pulses S ₅ (FIG. 5E). These counting pulses
_S5 is supplied together with signal _S4 to the gate circuit 11, in this example an AND gate. The output signal S ₆ of this gating circuit 11 therefore consists of a set of counting pulses, each having the same duration as the corresponding pulse of the signal S ₄ . In this example,
The difference in the duration of two sequential pulses of the signal S ₄ is
It is determined by counting the difference in the number of count pulses present in the corresponding set of count pulses of signal _S6 . This counting is performed using a count up/count down counter 12. In this case, a signal S ₆ is applied to the counting input 53 of the counter. The signal _S7 shown in FIG. 5G originates from a generator 19 and supplies this signal to the reset input 14' of the counter 12. This signal S ₇ contains one pulse per unit revolution, which pulse occurs before the first set of counting pulses of the two sequential sets of pulses of the signal S ₆ and causes the counter 12 to This ensures that the reference counting position is set at the beginning of each counting cycle. Generator 20 supplies to counting mode input 15 of counter 12 a square wave signal S ₈ (see FIG. 5H) having a fundamental frequency equal to the repetition frequency of the reset pulse in signal S ₇ . It is necessary that this edge of signal S ₈ always appears before the set of counting pulses in signal S ₆ occurs. In response to the command of this signal _S8 , the counter 12 is always set in count-up mode during the appearance of a set of counting pulses in signal _S6 and in countdown mode during the next set of counting pulses. Ru. Therefore, at the end of each counting cycle, the count value corresponds to a time error dT-1/2T.

A count value S ₉ appears at the count output terminal 21 of the counter 12. This count value _S9 is shown as a signal in FIG. 5I. At time _t1 , the counter is reset to the reference count value Cr by the command of signal _S7 . In this example,
This counter is simultaneously set to count-up mode with the command of signal _S8 . At time t ₂ , i.e. when the pulses of signal S ₃ and the set of counting pulses of signal S ₆ appear, the count value S ₉ increases, and this increase is caused by the appearance of a burst signal in signal S ₁ when the counter is no longer active. It lasts until the instant t ₃ when no counting pulses are received. time
At t ₄ , this counter is set to countdown mode under the command of signal S ₈ , and at time t ₅ the counter receives counting pulses again, so that the count value decreases, and this decrease occurs during said counting cycle. continues until the instant t ₆ when a second burst signal occurs. This counting cycle begins at the instant _t8 when the counter is reset to its reference count value Cr in response to the command of the signal _S7 and when the counter is also reset to the count-up mode.
ends at Between times _t9 and _t10 , the counter again receives counting pulses and increases its count value. At time _t11 , the counter is set to countdown mode and the counter again decrements in response to the application of counting pulses during time _t12 - _t13 . At time _t15 , this counting cycle is terminated by a reset pulse.

This time error can be measured proportionally. That is, in a manner similar to that in the illustrated embodiment, a signal proportional to the time error can be generated. In this case, a signal is generated indicating whether the relative position of the head is correct or incorrect and indicating, for example, whether it deviates by one track or by a group of tracks from the desired relative head position. For this purpose, the count value S ₉ is supplied to a decoding circuit 13 which supplies an output signal, i.e. in this example a logic value "1" when the count value S ₉ exceeds a certain limit value C ₊ or C _- . . In order to represent the polarity of the deviation, the counter 12 has an output terminal 16 from which it outputs a signal with the logic value "1" if the time error is positive and a logic value "1" if the time error is negative. 0'' signal. When using an n-bit count-up/count-down counter, it has a count value between 0 and 2 ⁿ -1, and if C _r =2 ^{n -1} is selected as the reference count value C _r , then The most significant bit represents the polarity of the time error.

From FIG. 5, between times t ₆ and t ₈ and between t ₁₃ and
It can be seen that the count value during t ₁₅ represents the time error. In order to read these counts, this circuit comprises a memory element 14, for example consisting of two flip-flops, which receives at its input the output signal of the decoding circuit 13 and from the output terminal 16 of the counter 12. supply the signal. This memory circuit transfers these logic signals to its output terminals, producing thereon signals S ₁₁ and S ₁₂ as shown in FIGS. 5K and 5L. The state of the output of this memory circuit 14 can only change if a pulse appears at the input terminal 22. For this purpose, the inverted signal of the signal S ₈ and the signal S ₂ are applied to a gate circuit 24, ie an AND gate in this example. Therefore, when the counter 12 is in countdown mode and a pulse of the signal S ₂ appears, the output signal S ₁₀ (FIG. 5J) of the gate 24 will be a logic "1". This therefore takes place at the end of each counting cycle after the signal S ₂ has suppressed the counting pulse S ₅ at the instants t ₆ and t ₁₃ .

In this example, signals S ₁₁ and S ₁₂ are time
At the beginning of the first counting cycle at t ₁ the logic value is "0". At time _t6 , a pulse appears in signal _S10 . In this case, the time error is negative, so the signal S ₁₁ has a logic value of "0", and the count value S ₉ corresponding to this time error exceeds the limit value C _- , so the logic of the signal S ₁₂ The value will be "1". Second
Time t ₁₃ at which pulse S ₁₀ at the end of the counting cycle occurs
, the time error is positive and the corresponding count value exceeds the limit value C ₊ , so the signal S ₁₂ remains at the logic value "1" and the signal S ₁₁ becomes the logic value "1".

These signals S ₁₁ and S ₁₂ are digital signals representing time errors. In the embodiment shown in FIG. 4, these signals are converted to analog servo signals. For this purpose, the circuit consists of an integrating capacitor C ₁
The voltage _S13 across the capacitor _C1 is a servo signal to the head 4. This signal S ₁₁ is supplied to the capacitor C ₁ via the charging resistor R ₁ and the switch 29.

When the switch 29 is closed and the signal S ₁₁ has a logical value "1", the capacitor C ₁ is charged and the signal S ₁₁
is the logic value "0", the capacitor C ₁ is discharged.

activating switch 29 by signal S ₁₂ ;
This switch is closed if the signal S ₁₂ has a logical value ``1'', which corresponds to the case when the relative position of the head is incorrect and in an incorrect position, and if the signal S <sub>12</sub> has a logical value ``0'' , since this switch is opened, the voltage S ₁₃ does not change. Signal S ₁₃ is shown in FIG. 5M. Capacitor C ₁ discharges between times t ₆ and t ₁₃ , and at time t ₁₃ when signal S ₁₁ changes, capacitor C ₁
will be charged again.

Certain disturbances may prevent the pulse shaper 7 from detecting the burst signal. As a result, one of the counting limits of the counter 12 is exceeded as the counter retains the counting pulses it is receiving for the remainder of the counting cycle. Although the relative positions of heads 4 and 5 are correct, an error signal is generated in this case and the heads are set in the wrong relative positions. In order to prevent such a situation from occurring, the counter 12 is provided with output terminals 17 and 18 from which a signal having a high logic level is produced when the upper or lower counting limit is reached, respectively. These output terminals are connected to an OR gate 32. The output of this OR gate is the two output terminals 1
When the logic level of one of the numbers 7 and 18 becomes "1", that is, when one of the two counting limits of the counter 12 is exceeded, the logic value becomes "1". In this embodiment, the output terminal of OR gate 32 is connected to the reset input terminal of flip-flop 31, and the signal _S7 is supplied to the set input terminal. The output terminal of flip-flop 31 is connected to the input terminal of AND gate 25, and the other input terminal is connected to the output terminal of decoding circuit 13. The output terminal of this AND gate is connected to the memory circuit 14.

When one count limit of the count range of the counter 12 is exceeded, the output of the gate 32 becomes a logic value "1" and the flip-flop 31 is reset, so that the logic level of its output becomes "0". As a result, the output of the gate 25 becomes a logic value "0", and when a pulse appears at the input terminal 22 of the memory circuit 14, the signal _S12 becomes a logic value "0", so that the switch 29
opens and the voltage _S13 no longer changes.

After the counting cycle exceeding the counting limit is completed, the flip-flop 31 is set with the signal _S7 so that the output of the flip-flop 31 becomes a logic value "1". As a result, the output signal of the decoding circuit 13 reaches the memory circuit 14 again, and when the next pulse appears at the input terminal 22 of this memory circuit 14, the signal S ₁₂ again reaches the logic level corresponding to the output signal of the decoding circuit 13. take.

Generators 9, 10, 19 and 20 can be synchronized in different ways. In recording devices in which speedometer generators are coupled to the motors that rotate heads 4 and 5, an oscillator included in a phase-locked loop together with the speedometer generator may be used for these generators. Synchronization can be performed by Furthermore, it is also possible, for example, to synchronize the counting pulse generator 10 with the aforementioned speedometer generator or with other available synchronization signals and to derive the signals S ₃ , S ₇ and S ₈ therefrom using, for example, a counter. can.

Regarding the measurement of time errors, it is possible not only to directly measure the time interval between two successive burst signals, but also to subtract the known value 1/2T from the measurement.

Regarding the generation of servo signals, the present invention is not limited to the integral on/off control method described herein, but can also use a proportional control method.

The burst signal need not be a signal added to the recorded signal, but can also be a signal forming a part of this recorded signal, for example a vertical synchronization pulse of a video signal.

The system described with reference to Figures 1 to 5 is one in which the relative heights of the two heads are controlled so that the two heads follow the correct track or group of tracks. Alternatively, the video recording device may be provided with a tracking system to position each video head relative to the correct track. In the case of such fine adjustments, the control loop that cooperates with the head that scans the track at that moment does not necessarily operate, and the control loop that cooperates with the head that does not scan the track at that moment does not necessarily operate. I haven't. When track scanning by one of the heads begins, a control signal having a specific initial value is supplied to the associated positioning means.

The method of cooperating the control system according to the invention with the fine adjustment described above makes it possible to control the aforementioned initial value according to the control signal _S13 . head 4
during each half-rotation period when the head 4 is not scanning the tape, supplying said initial value to the associated positioning element, and during each half-rotation period when said head 4 is scanning the tape, supplying a fine adjustment signal to the associated positioning means. I can do it.

FIG. 6 shows a circuit for generating servo signals _S19 and _S21 to control the positioning of heads 4 and 5. This circuit uses servo signal S ₁₈
It comprises a device 33 for generating an instantaneous tape scanning head, which controls the positioning of the head with respect to the center of the track to be read by this head, or the positioning of a particular track of a group of tracks. The position of this head relative to the center of the head is measured and a signal _S18 is derived therefrom. An example of such a fine-tuning circuit is described in Dutch patent application no.
No. 7409513 and No. 7702815.
The output signal _S18 of the fine adjustment device 33 is sent to the positioning element 48 of the head 5 via a resistor 37 and an amplifier 43.
It is also supplied to the positioning element 49 of the head 4 via the resistor 38 and amplifier 44.

During scanning of a track by head 4 or 5, the corresponding positioning element receives a servo signal to cause the head to follow the center of the track. The deviation of the head from the reference position at the end of the track is generally different from the deviation at the beginning of the track, while the track is such that the head position corresponding to the center of the beginning of the next track with respect to the reference value is different from the previous one. It extends so that it does not deviate too much from the initial position of the track. Therefore, in order to quickly center the head on the next track, it is advantageous to make the position of the head at the start of a track the same as at the start of the previous track. For this purpose, a signal is placed at the start of each track.
Sample S ₁₈ and keep that sample value,
During the next scan of the track by the head, the sample values are applied to the associated positioning element.
For this purpose, a signal S ₁₈ is applied via a charging resistor 34 or 55 and a switch 35 and 36, respectively, to a capacitor C ₂ or C ₁ , respectively. These switches 35 or 36 are controlled by the signals _S14 or _S15, respectively, to close them for a time period of, for example, 1 ms after the scanning of the track by the heads 5 or 4 has been started. After this time period,
The signal S ₂₀ or S ₁₃ across the capacitor C ₂ or C ₁ has a value corresponding to the value of the signal S ₁₈ during said period. This signal S ₂₀ or S ₁₃ is supplied as a follower to an amplifier 43 or 44 via an amplifier 39 or 40 and a switch 41 or 42 connected respectively. Signal switch 41 or 42
actuated by S ₁₆ and S ₁₇ to open the switch when heads 5 or 4 read a track;
During the reading of the two tracks, the switch is closed, so that during the period when the switch is closed, a signal corresponding to the signal S ₂₀ or S ₁₃ is supplied to each amplifier 43 and 44. follower amplifier 3
As a result of the low ohmic outputs of 9 and 40, the signal
This signal, corresponding to S ₂₀ or S ₁₃ respectively, is connected to resistor 37.
and ₃₈ , respectively. As a result, the signal S ₂₀ or S ₁₃ corresponding to the value of the signal S ₁₈ at the start of the previous track read by said head is transmitted to head 5 or 4.
during the scanning of the two tracks by the associated positioning element 48 or 49, respectively.

In order to control the head position when the position of head 4 relative to head 5 is off by one track or by a group of tracks, a switch 29 is included between resistor 55 and switch 36, and this latter switch is connected to signal _S12. operated by. Fourth
If the circuit shown in the figure generates an error signal S ₁₂ (for example, S ₁₂ has a logical value of "1"), switch 2
9 connects the switch 36 to the circuit 14 from which it supplies the signal S ₁₁ via the resistor R ₁ . Components 14, R ₁ , 29 and C ₁ shown in FIG _. 6 correspond to components with the same signs in the circuit shown in FIG. At the start of the scan (in which case the switch is closed) the capacitor C1 is charged or discharged and this signal _S13 of the capacitor _C1 is supplied to the positioning element 49 of the head 4 when the track is read and the switch 42 is closed. Ru. In the absence of an error signal (for example, the logic state of signal S ₁₂ is "0"), switch 36 is connected to circuit 33 via charging resistor 55 to determine the starting point of each track read by head 4. In capacitor C ₁
receives a signal corresponding to the signal _S18 at the start of the track, resulting in a fine adjustment of the initial value.

FIG. 7 is a waveform diagram showing a number of signal waveforms for explaining the operation of the circuit of FIG. Therefore, in this example, the signal shown in FIG. 5 is selected. 7B, 7C,
Figures 7D and 7E show signals S ₁₄ , S ₁₅ , S ₁₆ and S ₁₇
are shown respectively, and these signals are transmitted to switches 35, 36,
41 and 42 are activated, respectively. Note that in this case, a logic value of ``1'' for these signals means that the corresponding switch is closed, and a logic value of ``0'' means that the associated switch is opened. Signals S ₁₄ to S ₁₇ can be derived from signal S ₃ using a gate circuit 47, for example. FIGS. 7F and 7G show the signals S ₁₁ and S ₁₂ obtained from the circuit of FIG. 4. 7th H
The figure shows an example of the voltage S ₁₃ across the capacitor C ₁ and FIG. 7G shows the associated servo signal S ₁₉ for the positioning element 49.

Next, the operation regarding the head 5 will be explained. At every second pulse of the signal S _{3 ,} i.e. initially after the instant t ₃ in FIG. 7, the switch 35 is briefly closed under the command of the signal S ₁₄ and the value of the signal S ₁₈ is applied to the capacitor C ₂ . During the scanning of the track by the head 5, ie between the instants _t3 and _t4 shown in FIG. 7, the switch 41 opens and the positioning element 48 receives the (amplified) signal _S18 . For example, if a track is being scanned by head 4 between instants t ₄ and t ₆ , switch 41 is closed by command of signal S ₁₆ and positioning element 48 is scanned by signal S at instant t ₃ . Receive ₁₈ (amplified) values.

The control of the head 4 takes place according to a function of the signals S ₁₁ and S ₁₂ , which are selected by way of example and in the manner described below.

At the instant t ₁ the error signal S ₁₂ has the logical value "0"
Therefore, the switch 29 is in the switching position shown in FIG. At this instant, the head 4 starts scanning the track, and the switch 36 is closed in response to the signal _S15 . Signal during the period from time t ₁ to t ₂
S ₁₃ takes on a value corresponding to the value of signal S ₁₈ and this signal holds that value until the next pulse of signal S ₁₅ appears at time t ₄ . During times t ₁ and t ₃ , the positioning means 49 outputs the signal S ₁₉ shown in dashed lines in FIG. 7I.
receives an amplified signal S ₁₈ which is . When head 4 reaches the end of the associated track at time _t3 , switch 42 closes as commanded by signal _S17 and remains closed until time _t6 , when head 4 begins scanning the next track. . During the period from t ₃ to t ₄ , signal S ₁₉ has a value corresponding to the value of signal S ₁₃ . This process is repeated based on the command of signal S ₁₅ as long as the logic value of signal S ₁₂ is "0".

In this embodiment, it is assumed that head 4 is located on the wrong track or wrong set of tracks relative to head 5, for example due to interference. In that case, the signal S ₁₂ will be "1", and in this case the signal S ₁₁
represents the polarity of the error. At that instant, switch 29 is toggled and remains in its switched state as long as signal _S12 is at a logic value of "1". At the instant t ₈ when the next pulse appears in the signal S ₁₅ after the time t ₇ , the switch 36 is briefly closed and the signal S ₁₁ is applied to the capacitor C ₁ so that said capacitor is closed when the switch 36 is closed. Discharge is performed during the period from time _t8 to _t9 . From the instant t ₁₀ when the switch 42 is closed to the instant t ₁₁ when it is reopened, the signal S ₁₉ takes on a value corresponding to the signal S ₁₃ , so that the initial position of the head 4 has an error (signal S ₁₁ ). is corrected to the limit determined by charging resistor R ₁ and capacitor C ₁ depending on the polarity of . A servo signal S ₁₈ is supplied to the positioning element 49 between times t ₁₁ and t ₁₂ . This process is a signal
This is repeated each time a pulse occurs in signal S ₁₅ as long as the logical value of S ₁₂ is "1".

The illustrated apparatus controls the positioning of one head relative to the other head when an error signal is generated. In principle, for example, by making the circuit between the circuit 33 and the positioning means 48 the same as the circuit between the circuit 33 and the positioning means 49, it is possible to control both heads by the same amount. However, since an inverted signal _S11 is supplied, the head 5 can be controlled in the opposite direction to the head 4.

For example, in the system disclosed in Dutch patent application no. A system with coarse adjustment cannot be obtained without taking special steps. In fact, in such a system, the fine adjustment detects tracking errors within each group, eg, errors in two tracks, but does not detect errors in the size of the track group. Such a large error, for example, an error of 4 tracks and 2
When two heads are controlled by the same amount in opposite directions, the heads are controlled to a position with an error equivalent to two tracks. However, since the fine adjustment mechanism attempts to adjust the two heads in opposite directions over two tracks, the fine adjustment mechanism and the coarse adjustment mechanism will maintain opposite effects. In the case of a group error, it can be solved by adjusting the fine adjustment mechanism by two tracks. However, in this case the system described above presents no problems. For errors corresponding to one group (4 tracks), 2
The heads occupy proper positions relative to the fine adjustment mechanism. Correction of one head over one group (4 tracks) can lead to the correct position for the fine adjustment mechanism.

[Brief explanation of the drawing]

1 is a diagram showing a record carrier in the form of a tape with an information track and a pilot signal; FIG. 2 is a diagram showing a time profile of the pilot signal to be read; and FIG. 3 is a diagram showing the time error as a function of the tracking error. FIG. 4 is a diagram showing an embodiment of the device according to the present invention, and FIG. 6 is an explanatory diagram for explaining the apparatus shown in FIG. 4 in which the apparatus according to the invention cooperates with an apparatus for positioning the reproducing element in the center of the track; FIG. 7 is an illustration of the apparatus according to FIG. 6. FIG. 3 is a waveform diagram showing a large number of signal waveforms for explaining the operation of FIG. DESCRIPTION OF SYMBOLS 1... Tape, 4, 5... Magnetic head, 6... Reading device, 7... Pulse shaper, 8, 31... Flip-flop, 9, 10... Pulse generator, 11, 24... Gate circuit, 12... Counter, 13... Decoding circuit, 1
9, 20... Generator, 21... Memory element, 32... OR gate, 33... Fine adjustment device, 34, 37, 3
8, 55...Resistance, 29, 35, 36, 41, 42
...Switch, 39, 40, 43, 44...Amplifier,
47...Gate circuit, 48, 49...Positioning element.

Claims (1)

[Scope of Claims] 1. Two signals for reproducing signals recorded on a tape-shaped recording medium along recording tracks arranged substantially parallel to each other and obliquely to the long axis of the recording medium. The reproducing elements alternately read the recording track continuously, the mutual positions of the reproducing elements in a direction transverse to the recording track are controllable, and the recording track is continuously read by the two reproducing elements. In a method of positioning a reproducing element in a signal reproducing device, if the regenerated signal is read correctly, the regenerated signal always contains pilot signals located at the same nominal time interval. measuring the time between the occurrences of said pilot signal in each pair of recorded tracks that are read out, and further measuring the time between the occurrences of said pilot signal in each pair of recorded tracks that are read out; A method for positioning a reproducing element, characterized in that the relative position of the two reproducing elements in the lateral direction is corrected. 2. Measure the duration of a first time interval between a first reference instant and the detection of a subsequent pilot signal, and determine a second reference instant differing from said first reference instant by a predetermined nominal time. Measuring the duration of a second time interval between the detection of a subsequent pilot signal and determining the difference in duration of the first and second time intervals. A method for positioning a reproducing element according to scope 1. 3. a second signal for generating a first signal when the difference between the durations of the first and second time intervals exceeds a predetermined magnitude and representing the polarity of the difference between the durations;
A method for positioning a reproducing element according to claim 2, characterized in that a signal is generated. 4. First and second reproducing elements for reproducing signals recorded on a tape-shaped recording medium along recording tracks arranged substantially parallel to each other and obliquely to the long axis of the recording medium. It is equipped with
These first and second reproducing elements move continuously in a direction oblique to the long axis of the recording medium, and the first and second reproducing elements move in a direction transverse to the direction of movement of the first and second reproducing elements. A reproducing element positioning device comprising positioning means for controlling the position of the reproducing element, further comprising: a detection circuit for detecting the appearance of a pilot signal in the signals reproduced by the first and second reproducing elements; , a measuring circuit for determining the time interval between the occurrences of two detected sequential pilot signals; a comparison circuit for comparing said time interval with a predetermined nominal time; and said measured time interval. a control circuit for supplying a control signal to the positioning means when the time deviates from the nominal time by a predetermined amount. 5. The control circuit includes an integrating element and a first level signal when the time error measured by the comparator circuit is of a first polarity and a signal of a first level when the time error measured by the comparator circuit is of a first polarity. signal means for generating a second level signal when the signal has a polarity opposite to the first polarity; and supplying the signal to the integrating element when the measured time interval deviates by a predetermined amount. 5. The reproducing element positioning device according to claim 4, further comprising a switching element for positioning the reproducing element. 6. A second switching means is provided between the control circuit and the positioning means, and the second switching means is open during the time when the reproducing element controlled by the positioning means reproduces the signal from the recording medium. A reproducing element positioning device according to claim 5, characterized in that: 7. said detection circuit comprises a pulse shaper for shaping pulses in synchronism with said detected pilot signal, and said measuring circuit further comprises a pulse shaper for shaping pulses in synchronism with said detected pilot signal; a first pulse generator for generating equal pulses, the occurrence of a first pulse generated by the first pulse generator and the occurrence of another first pulse generated by the pulse shaper; the duration of a first time interval between and the first pulse generator
the duration of a second time interval between the appearance of a second pulse generated subsequent to the pulse and the appearance of another second pulse generated subsequent to the another first pulse by the pulse shaper; 7. The reproducing element positioning device according to claim 4, further comprising a duration difference measuring circuit for measuring the difference between the two. 8. The measuring circuit includes a counting pulse generator for generating counting pulses having a repetition frequency relatively higher than a repetition frequency of pulses from the first pulse generator, and a counting pulse generator for generating counting pulses having a repetition frequency relatively higher than a repetition frequency of the pulses from the first pulse generator; a gate circuit for transferring pulses; for counting the counting pulses in a first counting direction during the first time interval; and for transferring the counting pulses in a first counting direction during the second time interval;
8. The reproducing element positioning device according to claim 7, further comprising a switchable counter for counting in a direction opposite to the counting direction. 9. The measuring circuit comprises a bistable circuit, the set and reset input terminals of the bistable circuit being supplied with pulses from the pulse shaper and pulses from the first pulse generator, respectively; 9. The reproducing element positioning apparatus according to claim 8, wherein the gate circuit is controlled by an output signal. 10 said comparator circuit determines that the count value of said switchable counter at the end of each second time interval is from a reference position reached when the time interval between the occurrences of two successive pilot signals is equal to said nominal time; The reproduction according to claim 8 or 9, further comprising a decoding circuit that generates a first signal and a second signal representing the polarity of the deviation when there is a deviation by a predetermined amount. Element positioning device. 11 activating the first switching means by the first signal and activating the signal means by the second signal;
11. The reproducing element positioning device according to claim 10, wherein the reproducing element positioning device is controlled by a signal. 12 said comparator circuit receives the values of said first and second signals based on the command of a clock pulse that always occurs at the end of said second time interval, accumulates these values until the appearance of the next clock pulse, and 12. The reproducing element positioning apparatus according to claim 11, further comprising a memory circuit for supplying the accumulated value of the second signal to the first switching means and the signal means. 13. The switchable counter comprises a device for detecting whether the counting limit of the switchable counter has been exceeded and for inhibiting the supply of the next clock pulse to the memory circuit. A positioning device for a reproducing element according to scope 12.