JPH0822152B2 - Phase adjuster - Google Patents

Description

The present invention relates to a phase adjustment device in a phase control system of a magnetic recording / reproducing device.

[Conventional technology]

In a rotary head type magnetic recording / reproducing apparatus such as a VTR for recording / reproducing an information signal such as a video signal, it is possible to control the phase of the rotating head so as to record the information signal at a predetermined position on a recording medium such as a magnetic tape. FIG. 4 shows an example of the configuration. In FIG. 4, 1 is a rotary drum, 7 is a drive motor, and the drive motor 7 rotates the rotary drum 1 in the direction of arrow 2 at a constant speed. 3a
Numerals 3b and 3b are two magnetic heads which rotate integrally with the rotary drum 1, and are provided facing each other with a space of 180 ° between them.
For example, it is in contact with a magnetic tape (not shown) for 180 °. Reference numeral 4 is a rotating body that rotates integrally with the rotating drum, and 5a and 5b are N-pole and S-pole magnets, respectively, which are provided to face the rotating body 4 and are separated by 180 °. The pairs 3a and 3b are arranged with a predetermined angle difference. Reference numeral 6 denotes a fixed position detector composed of a detection coil, a magnetic sensitive element, etc., and outputs a detection signal S1 corresponding to the polarity of the magnet each time it faces the rotating magnet pair 5a, 5b. That is, the detection signal output of the position detector 6 is the magnetic head pair.
This means that the positions of 3a and 3b have been detected.

The detection signal S1 output from the position detector 6 is applied to the amplifier 11
The amplified signal is input to the pulse generator 12 including a Schmitt circuit to obtain the detection pulse P1, and this is input to the monostable multicircuit 13 In the monostable multicircuit 13, the resistance value of the volume VR1 is made variable. Detection pulse P input by
The signal HS obtained by adjusting the phase of 1 is output, and the phase comparator 14
Input to one input end. To the other input end of the phase comparator 14, for example, a reference signal REF synchronized with a video signal created from a vertical synchronization signal in a video signal recorded in a VTR is input, and a phase error signal Pe regarding both input signals REF and HS is input. Output. A signal obtained by amplifying the phase error signal Pe by the deviation amplifier 15 is used as a command signal to the drive circuit 16 of the drive motor 7 for rotating the rotary drum 1, so that the rotational phase of the rotary magnetic heads 3a and 3b is increased. Is controlled.

In this case, the video signal recorded on the magnetic tape must always be recorded at a predetermined position on the tape in consideration of compatible reproduction of the magnetic tape, so the rotary magnetic head has a predetermined phase with respect to the video signal to be recorded. Need to have. Here, as described above, the rotating magnetic head pair 3a, 3b
The position of is detected using the fixed position detector 6 and the rotating magnet pair 5a, 5b.
And 3b, the absolute positions of the magnets 5a and 5b, the absolute position of the position detector 6, and the like vary. In order to correct such variations, the rotary magnetic head is set to a predetermined position on the magnetic tape by making the time constant variable by using the volume VR1 of the monostable multi-circuit 13 and adjusting the phase of the detection pulse P1. The phase is controlled so that they touch each other.

[Problems to be solved by the invention]

In the phase control system of the conventional magnetic recording / reproducing apparatus, the phase is adjusted by adjusting the time constant by using the monostable multi-circuit 13 as described above. Will affect the phase error signal of the phase control loop, and for example, in the case of rotary magnetic heads, it will not be possible to make accurate contact with a predetermined position on the magnetic tape, and for applications where highly precise control performance is desired. However, there is a problem in that the drift of a delay circuit such as a monostable multi-circuit cannot be ignored.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain a phase adjusting device that is not affected by drift or the like in a phase control system.

[Means for solving problems]

A phase adjusting device according to the present invention includes pulse generating means for outputting a detection pulse formed by repeating a high level signal period and a low level signal period based on a detection signal relating to the position of a rotary head, and a rising edge of the detection pulse and Data generating means for generating the first data and the second data in synchronization with the falling edge respectively, and respective predetermined values based on the first data and the second data in synchronization with the rising edge and the falling edge of the detection pulse, respectively. A counter for counting the count value of, and the rising and falling phases of the detection pulse are respectively delayed according to the count output based on the first data and the count output based on the second data of the counter, A delay means for outputting as a head switching signal of the rotary head is provided, and the phase of the detection pulse is adjusted by these means. Order is obtained so as to determine the delay amount when the delay.

[Action]

The phase adjustment according to the present invention is performed based on the predetermined data based on the first and second data generated by the counter in synchronization with the rising and falling of the detection pulse and in synchronization with the rising and falling of the detection pulse. By counting the count value of, and delaying the rising and falling phases of the detection pulse according to the count output based on the first data and the count output based on the second data of the counter, The phase is digitally adjusted independently at the rising and falling edges of the detection pulse.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In FIG. 1, the parts designated by the same reference numerals as those in the conventional example shown in FIG. 4 have the same configuration as in FIG. That is, 1 is a rotary drum, which is rotated at a constant speed by the drive motor 7 in the direction of arrow 2. Three magnetic heads 3a and 3b are opposed to each other on the rotary drum 1 with 180 ° apart from each other, and are in contact with a magnetic tape (not shown) serving as a recording medium for 180 °. Reference numerals 5a and 5b denote magnets provided to face the rotary body 4 which rotates integrally with the rotary drum 1 at a distance of 180 ° from each other. The magnet pair 5a, 5b and the magnetic head pair 3a, 3b have a predetermined angular difference. Is arranged. Reference numeral 6 denotes a fixed-side position detector including a detection coil and a magnetic sensitive element such as a Hall element. The rotation-side magnet pair 5a, 5b and the position detector 6 constitute a rotation detector 10. . The position detector 6 outputs a detection signal regarding the positions of the magnets 5a and 5b that rotate in opposition to each other, which means that the positions of the magnetic heads 3a and 3b are equivalently detected. The configuration of the rotation detector 10 is not limited to that shown in FIG. 1, and various configurations can be adopted.

The detection signal S1 output from the position detector 6 is applied to the amplifier 11
The signal amplified by is input to the pulse generator 12 including a Schmitt trigger circuit to obtain the detection pulse P1, which is used as data input to the first latch circuit 21 constituting the phase shift circuit 100. The clock signal CLK is also input to the first latch circuit 21 to latch the detection pulse P1. The clock signal CLK may or may not be a clock phase-locked with a synchronizing signal such as a vertical synchronizing signal of the video signal recorded in the VTR. Such first latch circuit
The first latch signal L1 output from 21 is input to the second latch circuit 22 and is latched by the clock signal CLK input at the same time to output the second latch signal L2.

FIG. 2 is a time chart for explaining the operation of the embodiment of FIG. 1, where FIG. 2 (a) is a detection pulse P1 output from the pulse generator 12, FIG. 2 (b) is a clock signal CLK, and FIG. c) is the second latch signal L1, and FIG. 7 (d) is the second latch signal
It is L2. First and second shown in FIGS. 2 (c) and 2 (d)
By inverting the output signals obtained by inputting the latch signals L1 and L2 to the exclusive OR gate 23, the inverter circuit 24 inverts them to preset the low level to one clock width. Output pulse R1. That is, as shown in FIGS. 2 (a) and 2 (b), the timing of the rising or falling of the detection pulse P1 and the clock signal CLK can have various timing relationships, but what kind of timing relationship they have? Even if the detection pulse P1 is latched at the rising pulse of the clock signal CLK by the first latch circuit 21 and the second latch circuit 22 described above,
Each time P1 rises and falls, a preset pulse R1 having a low level of one clock width is obtained. The counter 25 receives the clock signal CLK and the preset pulse R1 output from the inverter circuit 24. The counter 25 supplies the preset pulse R1 with data every time the preset pulse R1 is at a low level. The count value is preset to the predetermined value.

On the other hand, the first latch signal L1 output from the first latch circuit 21
Is also input to the data generator 26, and the first data NU and the second data ND are used as the count data value of the counter 25 in each of the period in which the first latch signal L1 is high level and the period in which the first latch signal L1 is low level. Data signal D1
Is input to the counter 25. That is, in the counter 25, the count value is preset to NU in response to the data signal D1 by the preset pulse R1 having a low level of one clock width created in synchronization with the rising edge of the detection pulse P1, and the falling edge of the detection pulse P1. The count value is preset to ND by the preset pulse R1 created in synchronization with. After being preset with NU or ND in this way, the counter
The counter 25 repeats the count operation in which the count value is NU or ND until the next input of the preset pulse R1. Therefore, the counter 25 outputs the count output signal RC as shown in FIG. 2 (f). Then, the count output signal RC from the counter 25 is supplied as a clock input to the delay circuit 27 composed of a latch circuit, and the detection pulse P1 output from the pulse generator 12 is supplied as a data input.
Outputs a head switching signal HS as shown in FIG. 2 (g).

In this way, the head switching signal HS obtained by delaying the rising edge and the falling edge of the detection pulse P1 input to the phase shift circuit 100 to the position of the count signal regarding the count values NU and ND, respectively, is sent to the phase comparator 14. Is entered.
The reference signal REF synchronized with the video signal created from the vertical synchronizing signal in the video signal to be recorded in the VTR, for example, is also input to the phase comparator 14, and the phase error signal related to the phase difference between the both input signals HS and REF. Pe is output. A signal obtained by amplifying the phase error signal Pe by the deviation amplifier 15 is used as a command signal to the drive circuit 16 of the drive motor 7 for driving the rotary drum 1, thereby rotating the magnetic head.
The rotation phase of 3a and 3b is controlled.

As described above, since the magnets 5a and 5b on the rotating side or the position detector 6 on the fixed side forming the rotation detector 10 have variations in absolute position, a pulse is generated from the detection signal S1 of the rotation detector 10. The detection pulse P1 created by the device 12 varies in the relative positional relationship with the rotating magnetic heads 3a and 3b. In addition, although there are variations in the absolute positions of the magnetic heads 3a and 3b themselves, in order to correct these variations, the detection pulse in the phase control loop is used in this embodiment.
The delay amount is digitally adjusted individually for each rising and falling edge of P1. Therefore, since it is hardly affected by the drift in the delay circuit such as the monostable multi-circuit, the rotary magnetic head 3a and
The phase can be controlled with high precision so that the 3b is placed at a predetermined position on the magnetic tape.

If the head switching signal HS shown in FIG. 2 (g) represents the timing of head switching at which the magnetic heads 3a and 3b contact a predetermined position on a magnetic tape (not shown), for example, the head switching signal HS is The magnetic head 3a is in contact with the magnetic tape during the high level period, and the magnetic head 3b is in contact with the magnetic tape during the period when the head switching signal HS is at the low level.

In the above embodiment, the recording / reproducing of the VTR is performed by one channel consisting of the pair of magnetic heads 3a and 3b facing each other 180 ° apart while rotating 180 ° apart while facing the magnetic tape. The present invention is not limited to one channel, and the same effects as those of the above embodiment can be obtained in the case of recording / reproducing with multiple channels.

For example, FIG. 3 shows a case of a two-channel magnetic head pair. In FIG. 3, the pair of magnetic heads 8a and 8b facing each other with a space of 180 ° record and reproduce a luminance signal of a video signal, for example. This is the first channel. The pair of magnetic heads 9a and 9b facing the first channel with a delay of an angle θ with respect to the rotation direction 2 of the rotary drum 1 are the second channel for recording / reproducing a color signal of a video signal, for example. Also in FIG. 3, similarly to the embodiment of FIG. 1, the detection signal S1 output from the rotation detector 10 is input to the pulse generator 12 via the amplifier 11, and the detection pulse P1 output from the pulse generator 12 is input. Is input together with the clock signal CLK to the first shift circuit 100a having the same configuration as the phase shift circuit 100 of FIG. Then, the head switching signal HS thus obtained is input to the phase comparator 14 together with the reference signal REF to control the rotational phase of the rotary drum 1 without being affected by drift. And
First head switching signal output from the first phase shift circuit 100a
HS may be used as a signal indicating the timing of head switching when the magnetic heads 8a and 8b forming the first channel are in contact with a predetermined position on the magnetic tape.

Further, the first head switching signal HS from the first phase shift circuit 100a corresponds to the detection pulse P1 input to the first phase shift circuit 100a, and has the same configuration as the first phase shift circuit 100a together with the clock signal CLK. It is input to the second phase shift circuit 100b. However, magnetic head pair 9a, 9b
There is a variation in the absolute position in mounting the second channel composed of 1 and the relative position between the second channel and the first channel composed of the magnetic head pairs 8a and 8b. Therefore, the second phase shift circuit 100b digitally operates the rising and falling edges of the first head switching signal HS, which is the head switching timing signal for the first channel, by the same operation as the phase shifting circuit 100 of FIG. By individually delaying, the second head switching signal HS2 in which the above variations are corrected is output with almost no influence of drift in a delay circuit such as a monostable multi-circuit. Therefore, the second head switching signal HS2 can be used as a signal indicating the timing of head switching at which the magnetic heads 9a and 9b accurately contact each other at a predetermined position on the magnetic tape. Even in the case of three or more channels, the same effect as that of the embodiment shown in FIG. 3 can be obtained by providing the phase shift circuit by the number of channels as in the case of the embodiment shown in FIG.

Further, in the above embodiment, one channel is composed of two magnetic heads, and each magnetic head is a magnetic tape.
Although the case of contacting for 0 ° period has been described, one channel is composed of one magnetic head and the magnetic tape is contacted for more than 180 °, and one channel is composed of three or more magnetic heads. The magnetic head may be in contact with the magnetic tape for a period of less than 180 °, and the same effect as that of the above embodiment is obtained.

Furthermore, in the above embodiment, the rotation phase adjustment of the rotary magnetic head has been described, but the present invention can also be applied to the phase adjustment in a phase control system other than the rotary magnetic head, such as a capstan servo.

〔The invention's effect〕

As described above, according to the present invention, the rising and falling phases of the detection pulse generated from the detection signal relating to the position of the rotary head in the recording / reproducing apparatus are individually digitally delayed and adjusted. In a delay circuit such as a monostable multi-circuit, stable and highly accurate control performance can be realized without being affected by the existing drift, and it can be applied to a controlled object requiring high accuracy. is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing a phase adjusting device according to an embodiment of the present invention, FIG. 2 is a time chart diagram for explaining the operation of the device, and FIG. 3 is a block showing another embodiment of the present invention. 4 and 5 are block diagrams showing a conventional phase adjusting device. 12 …… Pulse generator, 14 …… Phase comparator, 21,22 …… Second
1, 2nd latch circuit, 25 ... Counter, 26 ... Data generator, 27 ... Delay circuit. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A pulse generating means for outputting a detection pulse formed by repeating a high level signal period and a low level signal period based on a detection signal relating to the position of a rotary head in a rotary head type recording / reproducing apparatus, and the detection. Data generating means for generating the first data and the second data in synchronization with the rising and falling edges of the pulse, and the first data and the second data in synchronization with the rising and falling edges of the detection pulse, respectively. A counter that counts each predetermined count value based on the count output based on the first data and the count output based on the second data of the counter. And the delay means for delaying and outputting as a head switching signal of the rotary head. A phase adjusting device comprising: a head switching signal and a reference signal as a phase comparison input and outputting a phase error signal related to a phase difference between the two signals to control the phase of the rotary head. .