JPH0262906B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording and reproducing device, and relates to a magnetic recording and reproducing device that is compatible with a two-head helical scan type magnetic recording and reproducing device and has a rotating drum with a small diameter. It is something.

[Prior Art] Conventionally, there has been a helical scan type in which a control track is provided on a magnetic tape, a control signal is recorded on the track, the control signal is reproduced from the track, and the running of the magnetic tape is controlled using this control signal. In magnetic recording and reproducing equipment (hereinafter referred to as VTR), the diameter of the rotating drum has been reduced while maintaining compatibility with 2-head VTRs.
There is a VTR. This VTR will be explained using FIGS. 3A to 3D.

FIG. 3A is a diagram showing the head configuration of a conventional two-head VTR, and FIG. 3B is a diagram showing the head configuration of a conventional two-head VTR.
FIG. In FIG. 3A, a rotating drum 2A is provided with a pair of magnetic heads 1a and 1b that are exposed on its circumferential surface and are opposed to each other in its diametrical direction, and each of the magnetic heads 1a and 1b has a different azimuth. are doing. A magnetic tape 3 is wound around the rotating drum 2a by more than 180 degrees, and a control head 4 is in contact with the magnetic tape 3. The magnetic heads 1a and 1b are rotated by the rotation of the rotary drum 2a, and helically scan the magnetic tape 3. 3rd B
In the figure, 5 is a video signal track, and a and b shown in the video signal track 5 are recorded by helical scanning of magnetic heads 1a and 1b, respectively. Further, 6 is a control track, and the control head 4 connects two video signal tracks to the control track 6.
Control signals N, S, . . . having a period are recorded.

Figure 3C shows a method proposed to miniaturize the above-mentioned two-head VTR (Japanese Unexamined Patent Application Publication No. 1989-1999).
89612), by using four magnetic heads, the drum diameter is reduced to 2/3 of that with two magnetic heads.
1 is a diagram showing the head configuration of a VTR. In FIG. 3C, the rotating drum 2b is provided with a pair of magnetic heads 1a, 1c that are exposed on its circumferential surface and are opposed to each other in the diametrical direction.
1c have the same first azimuth. Further, the rotating drum 2b has a pair of magnetic heads 1b and 1d exposed on its circumferential surface and facing each other in the diametrical direction, and a pair of magnetic heads 1a and 1c.
The magnetic head 1
b and 1d each have the same second azimuth. The magnetic tape 3 is placed around the rotating drum 2b.
The magnetic tape 3 is wound over 270 degrees, and the control head 4 is in contact with the magnetic tape 3. Rotating drum 2
b rotates 270 degrees during one field period, and the magnetic head 1a records in each field in turn.
→Magnetic head 1b →Magnetic head 1c →Magnetic head 1d →Magnetic head 1a... The track pattern recorded on the magnetic tape 3 by the helical scanning of these magnetic heads is as shown in FIG. 3D. In FIG. 3D, a, b, c, and d shown in the video signal track 5 are the magnetic heads 1, respectively.
a, 1b, 1c, and 1d. In the control track 6, a control signal having one cycle of two video signal tracks is recorded as in FIG. 3B. As mentioned above,
Since the azimuths of magnetic heads 1a and 1c are equal, and the azimuths of magnetic heads 1b and 1d are also equal, the same track pattern as shown in FIG. 3B can be obtained. That is, by setting the wrapping angle of the magnetic tape 3 around the rotating drum 2b to 270 degrees or more and adding two new magnetic heads to the rotating drum 2b, the drum diameter can be reduced to 2 while keeping the track pattern the same as that of a 2-head VTR. It can be downsized to /3.

[Problems to be solved by the invention] However, by reducing the diameter of such a drum,
In a VTR, two video signal tracks correspond to one cycle of the control signal, so the magnetic heads used for recording and reproduction are different (for example, the video signal tracks recorded by magnetic heads 1a, 1b, 1c, and 1d) , magnetic head 1c,
1d, 1a, 1b) will occur with a 50% probability. At this time, there may be problems between the magnetic heads 1a and 1c, or between the magnetic heads 1c and 1d, which may occur during the manufacture or installation of the magnetic heads.
If there is an azimuth error θ between them, 20log ₁₀ ｜sin
The drawback was that an azimuth loss expressed as (πWθ/λ)/(πWθ/λ)|(dB) occurred, making it impossible to achieve the original recording and reproducing characteristics. Note that W is the video signal track width and λ is the recording wavelength.

By the way, in a VTR, in order to automate tracking adjustment, four video signal tracks are combined into one track.
For each video signal track, four pilot signals having different frequencies are sequentially recorded by a rotating magnetic head, superimposed on the video signal to be recorded, and these pilot signals are reproduced from each video signal track by the rotating magnetic head. There is something like this. This invention eliminates the above azimuth loss by making the recording magnetic head and the reproducing magnetic head the same when downsizing a VTR that performs tracking using the above four pilot signals to 2/3 of a 2-head VTR. By doing so, the objective is to obtain a VTR that can realize the original recording and playback characteristics.

[Means for Solving the Problems] The VTR according to the present invention includes a first
a first pair of magnetic heads having an azimuth of
A second pair of magnetic heads having a second azimuth is provided perpendicularly to the pair of magnetic heads, and during recording, a pilot with a different frequency corresponding to each magnetic head is superimposed on the information signal on each track of the magnetic tape. Signals are recorded sequentially by each magnetic head, and during reproduction, each pilot signal is reproduced by each magnetic head, and information is recorded and reproduced by making a one-to-one correspondence between each magnetic head and each pilot signal based on the reproduced pilot signal. It was designed to do this.

[Operation] In the present invention, since each magnetic head and each pilot signal correspond one-to-one, the information signal is always reproduced by the magnetic head used during recording.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. In addition, in the description of the following examples, 3A
The explanation of parts that overlap with the explanation of figures 1 to D will be omitted as appropriate. FIG. 1A is a diagram showing the configuration of a portion related to reproduction of a magnetic recording and reproducing apparatus according to an embodiment of the present invention. First, the configuration of this part will be explained. A rotating drum 2b is provided on the shaft of the motor 9, and the motor 9 drives the rotating drum 2b. The rotating drum 2b is provided with a pair of magnetic heads 1a, 1c.
1c have the same first azimuth. Further, the rotating drum 2b includes a pair of magnetic heads 1b and 1d, and a pair of magnetic heads 1a and 1c.
The magnetic head 1
b and 1d each have the same second azimuth. The magnetic heads 1a, 1b, 1c, and 1d are provided with regenerative amplifiers 31a, 31b, 31c, and 31, respectively.
d, changeover switch 32a, 32b, 32c, 32
It is connected to the FM demodulator 33 via d. The FM demodulator 33 has changeover switches 32a, 32b, 32
It demodulates the reproduced signal from either of 32d and 32d and outputs a video signal. In addition, the changeover switch 32
a, 32b, 32c, and 32d are connected to a mixer 35 via a bandpass filter 34. The bandpass filter 34 is connected to the magnetic heads 1a, 1b, 1
A reproduced pilot signal is extracted from the signals reproduced at c and 1d. Further, a magnet 8 is provided on the shaft of the motor 9, and the PG head 7 faces the magnet 8.
is provided. PG head 7 is rotating drum 2
Detect the rotational phase of b. Magnet 8 is PG head 7
generates a reproducing magnetic field. The PG head 7 is connected to a timing control circuit 11 via a PG amplifier 10. A PG amplifier 10 amplifies the output of the PG head 7 and shapes its waveform. Further, the clock signal generation circuit 30 is connected to the timing control circuit 11. The timing control circuit 11 includes changeover switches 32a, 3
2b, 32c, and 32d, and is also connected to the mixer 35 via the pilot signal generating circuit 12. A clock signal generation circuit 30 generates a clock signal. The timing control circuit 11
In response to the output of the PG amplifier 10 and the clock signal, it generates pilot signal generation control signals C ₁ and C ₂ and head switching signals Ha, Hb, Hc, and Hd for switching the magnetic heads 1a, 1b, 1c, and 1d. The pilot signal generation circuit 12 receives pilot signal generation control signals C ₁ and C ₂ and generates one of four pilot signals f ₁ , f ₂ , f ₃ and f ₄ corresponding to each magnetic head. The mixer 35 is connected to a tracking control circuit 38 via a bandpass filter 36 and to a tracking control circuit 38 via a bandpass filter 37. The mixer 35 mixes the regenerated pilot signal and the pilot signal generation circuit 1.
Mix the pilot signals from 2. The bandpass filter 36 detects the amount of positional deviation of each magnetic head from the center of the video signal track 5 in one direction from the output of the mixer 35, and outputs a beat signal fa. Similarly, the bandpass filter 37 detects the amount of positional deviation of each magnetic head from the center of the video signal track 5 to the other, and outputs a beat signal fb. The tracking control circuit 38 compares the beat signal fa and the beat signal fb and outputs a tape running speed control signal.

Since the present invention utilizes a well-known tracking method using four pilot signals f ₁ to _{f 4} having mutually different frequencies, the principle thereof will be briefly explained. The frequencies of the pilot signals f ₁ to _{f 4} are |f ₁ −f ₂ |=
｜f ₃ −f ₄ ｜=fa, ｜f ₁ −f ₄ ｜=｜f ₂ −f ₃ ｜=fb, fa≠
Set to satisfy the fb relationship. During recording, as shown in FIG. 1B, one period consists of four video signal tracks 5, and pilot signals f ₁ , f ₂ , f ₃ , f ₄ are sent to each of the four video signal tracks 5 together with the video signal. are recorded sequentially. During playback, a beat signal (with frequencies fa and fb) is created from the pilot signal included in the playback signal and the pilot signal generated in the same order and period as during recording.
When tracking is complete, the speed of the magnetic tape 3 is controlled by utilizing the fact that the amplitudes of both beat signals are equal, thereby controlling its running.

Next, the operation of this embodiment will be explained using the timing diagram shown in FIG. During recording and playback,
As shown in Fig. 2b, when the counter value in the timing control circuit 11 is greater than or equal to Nr at time _t0 , when the output of the PG amplifier 10 rises, the counter value is set to Ns, and the count is started again by inputting the clock signal. Perform the action. Here, PG amplifier 1
0, as shown in FIG. 2a, a pulse of positive polarity is generated every rotation of the rotating drum 2b. As shown in FIG. 2 b, c, d, the timing control circuit 1
1 is used as the pilot signal generation control signals C ₁ and C ₂ , and when the counter value N is N ₁₁ ≦N<N ₂₁ , (H,
H), when N ₂₁ ≦N < N ₃₁ , (L, H), N ₃₁ ≦N
When <N ₄₁ , (H, L), N≧N ₄₁ and N<
When N ₁₁ , outputs (L, L). Here, the pilot signal generation circuit 12 operates so that the pilot signal generation control signals C ₁ and C ₂ are (H, H,) (L, H,) (H,
L, ) (L, L), the pilot signals f ₁ , f ₂ , f ₃ , respectively, as shown in FIG. 2 c, d, e,
Generate f ₄ . The pilot signal generating circuit 12 which operates in this manner is used in a two-head VTR and is well known. Counter values _N11 ~ _N21 , _N21 ~ _N31 , _N31 ~ _N41 , _N41 ~ _N11
The period corresponds to the period during which the rotating drum 2b rotates 270 degrees. As shown in Fig. 2a and b, the above Nr is determined by assuming that three rotations of the rotating drum 2b are one cycle.
The above counter is set to operate.
That is, in the range of N<Nr, the configuration is such that the output of the PG amplifier 10 is not accepted. The head switching signal Ha~ which is the output of the timing control circuit 11
Hd is a signal that controls the magnetic head used. Head switching signals Ha to Hd correspond to magnetic heads 1a to 1d, respectively, and when each signal is at "H" level and "L" level, the corresponding magnetic head is in a used state or a non-used state. . During recording, as shown in FIGS. 2b and f to i, for example, the magnetic head 1a is in use for a period when the counter value is _N10 to _N22 , and the magnetic head 1b is in use for a period when the counter value is _N20 to _N32 . In used condition. That is, in the switching portion of the magnetic head, there is a slight overlap period, and the same signal is recorded with two signals. This is to prevent signal dropout at the time of magnetic head switching during reproduction. Ignoring the above overlapped portion, the pilot signals f ₁ , f ₂ , f ₃ , and f ₄ are recorded together with the video signals on the video signal tracks formed by the magnetic heads 1a, 1b, 1c, and 1d, respectively. . That is, the track pattern shown in FIG. 1B is formed. In FIG. 1B, f ₁ to _{f 4} written on the video signal track 5 indicate the pilot signals recorded on the video signal track 5, and a
-d indicate that the video signal tracks were recorded by magnetic heads 1a-1d, respectively.

During playback, the magnetic head used is 1 at any time.
When the counter values are N ₁₁ , N ₂₁ , N ₃₁ , and N ₄₁ , the magnetic heads 1a, 1b, 1c, and
1d becomes in use. In addition, the magnetic heads 1a~
When 1d is in use, the pilot signals output by the pilot signal generating circuit 12 are _f1 to _f4 , respectively, as shown in FIG. 2e and j to m.
That is, during recording and reproduction, the magnetic heads 1a,
When 1b, 1c, and 1d are in use, the outputs of the pilot signal generating circuit 12 are pilot signals f ₁ , f ₂ , f ₃ , and f ₄ , respectively.

In the above embodiment, various control signals are generated from the PG signal using a counter and a clock signal generation circuit, but a one-shot circuit or the like may also be used.

[Effects of the Invention] As described above, according to the present invention, a first pair of magnetic heads having a first azimuth and a second pair of magnetic heads having a second azimuth orthogonal to the first pair of magnetic heads are provided. A pair of magnetic heads is provided, and during recording, each magnetic head sequentially records a pilot signal of a different frequency corresponding to each magnetic head by superimposing it with an information signal on each track of the magnetic tape, and during playback, each pilot signal is Since information is recorded and reproduced using a magnetic head and each magnetic head corresponds one-to-one with each pilot signal based on the reproduction pilot signal, the information is always read from the track using the magnetic head that recorded it. The signal can be reproduced, and the inherent recording and reproduction characteristics can be realized.

[Brief explanation of drawings]

FIG. 1A is a diagram showing the configuration of a portion related to reproduction of a magnetic recording and reproducing apparatus according to an embodiment of the present invention. FIG. 1B is a diagram showing a track pattern recorded by a magnetic recording/reproducing apparatus according to an embodiment of the present invention. FIG. 2 is a timing diagram illustrating the operation of a magnetic recording/reproducing apparatus according to an embodiment of the present invention. FIG. 3A is a diagram showing the head configuration of a conventional two-head VTR. FIG. 3B is a diagram showing a track pattern recorded by the conventional two-head VTR of FIG. 3A. FIG. 3C is a diagram showing a conventional VTR head configuration that uses four magnetic heads to reduce the drum diameter to two-thirds of that of two magnetic heads. FIG. 3D is a diagram showing a track pattern recorded by the 4-head VTR of FIG. 3C. In the figure, 1a, 1b, 1c, and 1d are magnetic heads, 2a and 2b are rotating drums, 3 is a magnetic tape, 4 is a control head, 5 is a video signal track, 6 is a control track, 7 is a PG head, and 8 is a magnet. , 9 is the motor, 10 is the PG amplifier,
11 is a timing control circuit, 12 is a pilot signal generation circuit, 31a, 31b, 31c, 31d are regenerative amplifiers, 32a, 32b, 32c, 32d are changeover switches, 33 is an FM demodulator, 34, 36,
37 is a band pass filter, 35 is a mixer, 38
is a tracking control circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A magnetic tape wound around a rotating drum is helically scanned by a magnetic head provided on the rotating drum, and an information signal is superimposed on the track of the magnetic tape and a frequency signal is superimposed on the information signal. In a magnetic recording and reproducing apparatus that records a plurality of pilot signals with different values, and controls the running of the magnetic tape based on the reproduced pilot signals during reproduction, the magnetic head is attached to the rotating drum and on the circumferential surface of the rotating drum. a first magnetic head pair consisting of two magnetic heads having a first azimuth, which are exposed and provided facing each other in the diametrical direction of the rotating drum; a second magnetic head pair consisting of two magnetic heads having a second azimuth, the second magnetic head pair extending from the rotary drum, facing each other in the diametrical direction of the rotating drum, and disposed perpendicularly to the first pair of magnetic heads; Furthermore, a rotational phase detection means for detecting the rotational phase of the rotary drum, a control signal for generating each pilot signal corresponding to each of the magnetic heads based on the output of the rotational phase detection means, and switching between the respective magnetic heads. a timing control means for generating a head switching signal; a pilot signal generating means for generating the pilot signal corresponding to each of the magnetic heads based on the control signal; a switching means for switching the output, and one for each of the magnetic heads and each of the pilot signals.
A magnetic recording/reproducing apparatus characterized in that the information is recorded and reproduced in a pair-to-one correspondence. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the information signal is a video signal.