JPH04271002A - Reproducing device - Google Patents

Abstract

PURPOSE:To correct the non-linearity of a track and the scan by making a pair of magnetic heads scan on loci overlapping with each other in the track width direction in a normal reproduction mode and then editing the signals received from those heads. CONSTITUTION:A tape 4 is fed toward an arrow with revolutions of a rotary drum 1. A pair of magnetic heads A and A' and a pair of magnetic heads B and B' have the same azimuth to the axis of the drum 1. The diagram shows the relational positions of these heads when viewed from the axis of the drum 1. The scan locus of the head A is shown by (c) and the cirve of this locus is due to the scanning non-linearity obtained between a track and the scan. Meanwhile the scan locus of the head A' is shown by (d) and the track width is shown by the dotted lines. Then the non-linearity can be corrected in comparison with the scan of a single head with use of the former and latter hatched halves of both loci. In addition, the accurate reproduction of information is attained even in a special scan state owing to the mutual compensation of both head pairs.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus for reproducing information signals recorded as diagonal tracks on a tape medium by a rotary head.

0002

2. Description of the Related Art In a reproducing apparatus that reproduces information signals recorded as diagonal tracks on a tape medium,
Helical scanning is performed using a rotating head. In such reproducing apparatuses, various factors such as cylinder shaft vibration, tape running fluctuations, and tape deformation deteriorate the linearity of the tracks on the tape medium and the head scanning locus during reproduction. This does not pose any problem if the track pitch is sufficiently larger than the degree of deterioration of linearity. However, when the degree of deterioration reaches a level that cannot be ignored with respect to the track pitch, the magnetic head is no longer able to correctly scan the track, leading to a drop in the level of the reproduced signal.

On the other hand, in order to achieve high-density recording on tape media, it is necessary to narrow the track pitch. Therefore, the required mechanical precision of the reproducing device is improved accordingly, which causes an increase in cost, and conversely, the mechanical precision hinders the improvement in recording density. As a means to solve these problems, there is a method (DTF) in which a movable head using a piezoelectric element or the like is used, the misalignment between the magnetic head and the track is detected by some method, and the head position is driven so that the misalignment becomes zero. be. In addition, a non-tracking method has also been proposed as a reproduction method based on the assumption that the magnetic head does not scan the track correctly (for example, Japanese Patent Laid-Open No. 57
-150109).

[0004] Furthermore, in playback devices that record and play back audio and moving images, it is necessary to play back signals at a tape speed different from normal playback as so-called special playback such as slow speed or double speed. It is valid. In other words, when playing back at a tape speed different from normal playback, the magnetic head scans diagonally across the tracks on the tape, but the DTF detects the velocity component perpendicular to the tracks out of the relative speed of the magnetic head to the tracks. By canceling, the magnetic head is able to trace the track correctly. During slow playback, the magnetic head sequentially traces all tracks, including overlaps. In double-speed playback, it is not possible to trace all tracks unless the cylinder rotation speed is changed, so interlace scanning is normally performed for several tracks as a unit.

[0005]Furthermore, since the non-tracking method does not originally require tracking, reproduction can be performed during special reproduction in the same manner as during normal reproduction. Furthermore, since non-tracking inherently has redundancy in playback, it is possible to pick up more information signals than DTF in special playback, especially in high-speed playback where DTF cannot track tracking, and the final playback output is Another benefit is that the quality of audio and images can be improved.

[0006]

[Problems to be Solved by the Invention] DTFs not only have a complicated structure and lead to increased costs, but also have limited track following performance due to the actuator that drives the magnetic head and the detection characteristics of head position deviation, and cannot completely follow the track. There is also the issue of not being able to keep up.

Furthermore, the non-tracking method has the following problems with respect to narrowing the track. In other words, in non-tracking, the loss due to off-tracking is compensated for by increasing the redundancy of scanning during playback compared to during recording, but in order to ensure redundancy, it is necessary to use the playback signal up to a certain degree of off-tracking. There is. However, when the track is narrowed, azimuth loss decreases, so crosstalk from adjacent tracks increases, and restrictions on the amount of off-track to ensure the C/N required for signal reproduction become stricter. Therefore, the redundancy of scanning required to establish the non-tracking method increases, making it difficult to realize a reproducing apparatus.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the reproducing device of the present invention includes a plurality of pairs of magnetic heads each having a first and a second magnetic head having the same azimuth. Track pitch Tp on the mounted tape medium
a rotary drum for reading and scanning a track formed diagonally by the magnetic head; a signal processing means for reconstructing the output of the pair of magnetic heads to reproduce an information signal recorded on the track; tracking control means for controlling running of the tape so that a deviation between each of the first and second magnetic heads and the track becomes zero on average; Set the width to (1+
β)・Tp, the angular interval on the rotating drum between the pairs of magnetic heads having the same azimuth is θ0, α
is a real number such that 0<α≦β, and δ is a real number such that −β<δ<β, then the relative height Δh and angular interval Δθ of the second magnetic head with respect to the first magnetic head are expressed as Δh=(1 −α+δ)・Tp/2 Δθ=(1+α+δ)・θ0/4.

[0009] Furthermore, a plurality of pairs of magnetic heads each having a first and second magnetic head having the same azimuth are mounted, and a track formed diagonally at a track pitch Tp on a tape medium is used. a rotating drum for reading and scanning, and a signal processing means for reconstructing the output of the pair of magnetic heads and reproducing the information signal recorded on the track;
tracking control means for controlling running of the tape so that a deviation between each of the first and second magnetic heads of the pair of magnetic heads and the track becomes zero on average; The head width of the magnetic head is (1+β)・
Tp, the angular interval on the rotating drum between the pairs of magnetic heads having the same azimuth is θ0, and α is 0<
Relative height Δh and angular interval Δ of the second magnetic head with respect to the first magnetic head, when α≦β is a real number.
θ is set to Δh=(1−α)·Tp/2 Δθ=(1+α)·θ0/4.

0010

[Operation] According to the above-described structure, during normal playback, the first and second heads scan the same track in the track width direction in an overlapping manner, and from the results of these scans, the signals recorded on the track are determined. , which reduces the effects of track and scan nonlinearities. Further, during special reproduction, the quality of the reproduced signal is improved by minimizing the overlap of scans and maximizing the effective scanning area.

[0011]

[Example] The following is a reproduction device according to an embodiment of the present invention.
This will be explained with reference to the drawings. (FIG. 1) is a block diagram of a playback device in one embodiment of the present invention. (Fig. 1), 1 is a rotating drum, 2 is a tracking control means, and 3 is a rotating drum.
4 is a signal processing means, and 4 is a tape medium. The operation of the playback device configured as described above during normal playback is generally as follows.

The tape medium 4 is wound around the rotating drum 1, and is fed at a substantially constant speed by the tracking control means 2. As the rotary drum 1 rotates, a magnetic head mounted on the rotary drum 1 obliquely scans the tape medium 4 to read recorded signals and output a head reproduction signal. The head reproduction signal is processed by signal processing means 3.
The signal is then sent to the station, undergoes processing such as signal demodulation and reconstruction, and is output as the final reproduced signal. Further, the head reproduction signal is also supplied to the tracking control means 2. The tracking control means 2 detects a deviation between the magnetic head and the track on the tape medium 4, and controls tape running so that the head correctly traces the track.

Next, the structure and operation of the surroundings of the rotating drum 1 will be explained in more detail with reference to FIGS. 2 and 3. (FIG. 2) is a schematic diagram showing the arrangement of magnetic heads on the rotating drum 1. (Fig. 2), 1 is a rotating drum;
4 is a tape medium, A and B are magnetic heads having opposite azimuths, A' is a magnetic head having the same azimuth as magnetic head A, and B' is a magnetic head having the same azimuth as magnetic head B. In addition, (Fig. 3 (a)) is a vector diagram showing the relationship between the tape feed, the scanning of the magnetic head, and the scanning locus on the tape medium, and (b), (c), and (d) of the same figure are vector diagrams showing the relationship between the tape feed, the scanning of the magnetic head, and the scanning locus on the tape medium, and (b), (c), and (d) of the same figure are the tracks on the tape and the magnetic head. FIG.

In FIG. 3(a), VT is the tape feed vector, and VH is the scanning vector of the magnetic head by the rotating drum 1. At this time, since the scanning locus of the magnetic head viewed from above the tape is given by VH - VT, this becomes a vector shown by a broken line in the figure. In addition,
Normally, in such a helical scan, the head scanning locus is oblique to the tape, but here it is schematically shown perpendicular to the tape for ease of understanding. When such a vector relationship exists, the scanning trajectory of each head with respect to the tape is as shown in FIG. 3(b). Tape medium 4
The numbers written above are track numbers added for convenience to identify the tracks.

During recording, the magnetic head tracks (1),
(2) and (3) are recorded in order, but the tracks actually formed on the tape medium 4 generally lose linearity due to mechanical accuracy errors in tape running and drum rotation, and tape deformation. , for example, curved as shown. The illustrated track also includes non-linearity errors in reading scans. These tracks are read and scanned to reproduce recorded signals. First, let us consider the case where the magnetic head A scans the tape.

The scanning start position and scanning locus of the magnetic head with respect to the track are as shown in (FIG. 3(b)), but the one drawn by extracting only the magnetic head A and track (1) is (FIG. 3(c)). ). In this example, the head width is 1
．． 5Tp (Tp is track pitch). In the first half of scanning, a portion of the track protrudes to the left of the scanning locus due to track curvature, and the reproduced signal level decreases accordingly. In the latter half of scanning, the track is included in the scanning locus, so there is no drop in the reproduced signal level. In the end, the track range that can be played without a drop in level is the hatched area.

Next, scanning is performed by the magnetic head A'. In this example, the head position and head height are determined so that magnetic head A' performs scanning with a 0.5 Tp shift relative to magnetic head A. The relationship between the track (1) and the scanning locus in this case is shown in FIG. 3(d). In this case, contrary to the magnetic head A, signal reproduction is possible without a drop in level during the first half of the scan, but in the second half of the scan, part of the track protrudes to the right side of the scanning locus and the reproduction level decreases. In this case, the range in which the signal can be reproduced without a drop in level is shown by hatching. Here, it can be seen that if reproduction signals from both magnetic heads A and A' are used, greater track nonlinearity can be tolerated compared to single head scanning.

The signal processing means 3 shown in FIG. 1 reconstructs the information recorded on the track from the reproduction signal obtained from these two scans. In actual processing, first, information representing signal quality, such as signal amplitude and error flags in digital recording, is extracted from the head reproduction signal, and from the results, in the example of (Fig. 3), magnetic head A
The information recorded on the original track is reconstructed by using each reproduction signal in a complementary manner, such as using the second half of the output and the first half of the output of the magnetic head A'. Track (2) is similarly scanned by magnetic heads B and B', thereby reproducing the information. Thereafter, information on each track is sequentially reproduced in the same manner.

Next, special playback will be explained with reference to FIG. 4. In this case, similarly to (Fig. 3), (Fig. 4
(a) is a vector diagram showing the relationship between the tape feed, the scanning of the magnetic head, and the scanning locus on the tape medium; (b)
shows a schematic diagram of the tracks on the tape and the scanning locus of the magnetic head. However, the difference is that the direction of the vector VT is reversed because it is assumed to be played back at -1x speed. As a result, the head scanning locus on the tape 4 is largely inclined with respect to the track as shown by the broken line. At this time, the signals obtained from each magnetic head correspond to the portion where the scanning locus and the track overlap. Here, they are shown by vertical hatching for magnetic head A, and horizontal hatching for magnetic head A'. Note that in this example, azimuth recording is performed, and even-numbered tracks that are in the opposite azimuth to magnetic head A are excluded from consideration, as they have almost no effect on the signals reproduced from the tracks with the opposite azimuth. There is. The scanning positional relationship of magnetic heads A and A' is (Fig. 3
) is different from normal reproduction due to the effect that these heads are arranged discretely from each other on the rotating drum 1. Further, the scanning start position of the magnetic head A after one rotation of the rotary drum 1 is the position of track (3). It can be seen that by sequential scanning, each scan progresses to cover all the tracks while maintaining some overlap with each other. The magnetic heads B and B' also perform similar scanning for even-numbered tracks with reverse azimuth. Therefore, if reproduction signals from these magnetic heads are supplied to the signal processing means 3 in the same way as during normal reproduction while allowing a certain degree of reduction in the reproduction signal amplitude, all information can be reproduced in this case as well.

Here, how much information can be reproduced from each track is determined by how much of the track can be covered by the scanning locus of each magnetic head, regardless of the scanning inclination. Therefore, for example (Fig. 4(b)
)) Once the scanning start position of each magnetic head as shown on the lower side of the tape medium 4 is determined, the reproducible ratio is determined.

Focusing on this point, the general case of special playback will now be described with reference to FIG. 5. (Figure 5)
is a diagram showing the scan start position during various playbacks with magnetic head A as a reference, the horizontal axis is the scan start position of each magnetic head on the tape, and the vertical axis is the tape running speed normalized by the speed during normal playback. It is expressed as Since the magnetic head A serves as a reference, the scanning start position is the same at any speed. On the other hand, the scanning start position of the magnetic head A' changes depending on the tape running speed.

First, when stopped, a position shifted by the relative head height from the magnetic head A becomes the scanning start position. At other speeds, the tape speed, the rotation period of the rotating drum, and the magnetic head A' of the magnetic head A' on the rotating drum.
The position is moved from the time of the above-mentioned stop by an amount determined by the angular position relative to the angular position. Now, if we consider that the period of the rotating drum is fixed, the locus of A' in the diagram becomes a straight line. Also,
The intersection of this straight line with the speed 0 line corresponds to the head height, and the inclination corresponds to the head angular position. Therefore, if a straight line is determined on (FIG. 5) so that the head positional relationship at each speed is best under appropriate conditions, each head angular position and relative height can be determined accordingly.

[0023] Here, magnetic heads A and A' during normal reproduction are
(or the same for B and B') When the scanning deviation is α・Tp, each scanning is lined up at equal intervals at -1x speed,
In other words, the straight line is determined on the condition that the overlaps of the scans are arranged evenly. The reason for this is that, firstly, in so-called slow-motion playback at 1/2x speed or lower, magnetic heads A and B (or magnetic head A
Even with only two heads (' and B'), the redundancy of scanning during playback can be more than twice that during recording, so the effect of doubling the number of scans is weak to begin with. In high-speed playback, it is not possible to scan all the tracks in the way seen in the example at -1x speed, and on the contrary, the scanning becomes coarse, so there is almost no possibility that each scan overlaps with each other. , there is virtually no need to consider it.

Now, under the above conditions, the arrangement of each magnetic head, that is, the relative height Δh and angular interval Δθ of the second magnetic head with respect to the first magnetic head, is determined by the rotation drum between the pairs of magnetic heads having the same azimuth. It is calculated graphically by setting the angular interval above as θ0, and the result is as shown in the formula below. Δh=(1-α)・Tp/2 Δθ=(1+α)・θ0/4 In this embodiment, θ0 is θ0 because there is no other magnetic head pair having the same azimuth as the magnetic head pair A, A'. θ0=360°. Also, since α=0.5, it is finally given by Δh=Tp/4 and Δθ=135°. That is, by attaching the magnetic head A', which is 135 degrees away from the magnetic head A and shifted in height by Tp/4, the magnetic head A' is installed at a position 135 degrees away from the magnetic head A, so that the height of the magnetic head A' is shifted by Tp/4 during normal playback (Fig. 3), and when -1x speed playback (Fig. Scanning is performed according to the relationship shown in 4). As a result,
During normal playback, the tolerance for track nonlinearity is expanded, allowing playback without causing a drop in signal level.
Also, during special playback, duplication of scans by the magnetic head is suppressed so that the maximum amount of information can be picked up from all scans.

[0025] In the above example, Δh and Δθ are each set to the optimum values, but in reality, they are not limited to one point, and there is a certain allowable range for the values. The minimum requirement is to pick up all the information on the tape medium 4 without omission. For this purpose, each point on the tape medium 4 must be scanned by at least one magnetic head for each azimuth. As already mentioned, this condition is satisfied in slow motion playback at speeds of ±1/2 times or less. Therefore, in this case as well, the scanning start position may be arranged so as to satisfy this condition at -1x speed. Now, if the head width of each magnetic head is (1+β)·Tp, and the deviation of the scan start position from the above optimal value is δ·Tp, then if δ is −β<δ<β, each scan overlaps. Therefore, the above conditions are satisfied. Δh and Δθ in this case can also be found from the figure in the same way as in the case of (Fig. 5), and Δh=(
1-α+δ)・Tp/2 Δθ=(1+α+δ)・θ0/4. If a diagram representing the relationship between the scanning start positions at this time is drawn, it will be as shown in FIG. 6. At this time, when δ=0, (
This corresponds to the embodiment shown in FIG. 5). When δ≠0, although not optimal, at least the entire area on the tape medium 4 is scanned, so the head reproduction signal includes information regarding all data on the tape medium 4.

(FIG. 7) is a diagram showing another example of arrangement of the magnetic head pair on the rotating drum 1. Compared to the example shown in FIG. 2, the number of magnetic heads and the values of α and β are the same, but magnetic heads A and B and magnetic heads A' and B' are arranged at the same location. As a result, the magnetic head A system and the magnetic head B system are shifted from each other in the height direction by Tp, but the relationship between the magnetic heads A and A' (or magnetic heads B and B') remains unchanged.

FIG. 8 is a diagram showing still another example of the arrangement on the rotating drum 1, in which the tape winding angle is 90° and the number of head pairs is increased from 2 to 4. In this case, the magnetic head pair 2A, 2A' (2B, 2B') has the same azimuth as the magnetic head pair 1A, 1A' (1B, 1B').
B') are in opposing positions, so θ0 is 180° and Δθ=67.5°.

[0028]

As described above, according to the present invention, during normal reproduction, the first and second magnetic heads scan the same track overlappingly in the track width direction, so that the track can be determined based on the scanning results. By reconstructing the signals recorded above, the effects of track and scan nonlinearities can be reduced. Furthermore, during special reproduction, the first and second magnetic heads scan so as to minimize the overlap of their scans and maximize the effective scanning area, so that the quality of the reproduced signal can be improved.

[0029] As long as the tracking control means controls the tape feed so that the deviation between the first and second magnetic heads and the track becomes zero on average during normal playback, the specific construction method thereof may be used. There is no limit to A commonly known method is to record pilot signals on tracks by area division or frequency division, and detect misalignment between the magnetic head and the track from the crosstalk level from adjacent tracks. It is also possible to consider a method that takes advantage of the feature that scanning is performed twice and uses the level difference between the reproduction signals of the two scans.

[0030] Also, there are no limitations on the structure of the signal processing means, as long as it reproduces signals by complementary use of the reproduction signals from the first and second magnetic heads. Specific processing varies depending on the signal to be recorded and the modulation method, and will not be discussed here.

In the example, α and β are each 0.
Although only an example in which the value is 0.5 and 0.5 is shown, the value is not limited to this value. Also, if α≦β, the scan overlap during normal playback will be greater than Tp, and it is possible to eliminate a drop in the playback signal level at the tracking center position. Less tolerance for linearity. Conversely, by increasing α, resistance to linearity deterioration can be increased. However, if α>β, when a track is located at the center of scanning of the first and second magnetic heads during normal reproduction, the reproduction signal level of both magnetic head outputs decreases, which is disadvantageous for signal reproduction. Therefore, the final decision should be made based on these trade-offs.

Further, although Δh and Δθ are strictly defined by mathematical formulas here, they are not limited to the values of the above formulas as long as the relationship between each scan is not significantly impaired.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a playback device in one embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of the arrangement of magnetic heads on a rotating drum according to the present invention.

FIG. 3 is a vector diagram and a schematic diagram showing the relationship between a track and a magnetic head scanning locus during normal reproduction.

FIG. 4 is a vector diagram and a schematic diagram showing the relationship between tracks and magnetic head scanning trajectories during special reproduction.

FIG. 5 is a diagram showing a magnetic head scanning start position in an optimal arrangement during various types of reproduction.

FIG. 6 is a diagram showing magnetic head scanning start positions during various types of reproduction.

FIG. 7 is a schematic diagram showing another example of the arrangement of magnetic heads on a rotating drum according to the present invention.

FIG. 8 is a schematic diagram showing still another example of the arrangement of magnetic heads on a rotating drum according to the present invention.

[Explanation of symbols]

1 Rotating drum 2 Tracking control means 3 Signal processing means 4 Tape media

Claims (2)

[Claims] Claim 1: A plurality of pairs of magnetic heads each having a first and second magnetic head having the same azimuth are mounted, and a track is formed diagonally at a track pitch Tp on a tape medium. a rotating drum for reading and scanning; a signal processing means for reconstructing the output of the pair of magnetic heads to reproduce the information signal recorded on the track; and each of the first and second magnetic heads of the pair of magnetic heads. tracking control means for controlling the running of the tape so that the deviation from the track becomes zero on average, and the head width of the first and second magnetic heads is set to (1+β)·T.
p, the angular interval on the rotating drum between the pairs of magnetic heads having the same azimuth is θ0, and α is 0<α
When δ is a real number such that ≦β, and δ is a real number that −β<δ<β, the relative height Δh and angular interval Δθ of the second magnetic head with respect to the first magnetic head are Δh=(1−α+δ)・A reproducing device characterized in that Tp/2 Δθ=(1+α+δ)·θ0 /4. 2. A plurality of pairs of magnetic heads each having a first and second magnetic head having the same azimuth are mounted on a track formed diagonally at a track pitch Tp on a tape medium. a rotating drum for reading and scanning; a signal processing means for reconstructing the output of the pair of magnetic heads to reproduce the information signal recorded on the track; and each of the first and second magnetic heads of the pair of magnetic heads. tracking control means for controlling the running of the tape so that the deviation from the track becomes zero on average, and the head width of the first and second magnetic heads is set to (1+β)·T.
p, the angular interval on the rotating drum between the pairs of magnetic heads having the same azimuth is θ0, and α is 0<α
Relative height Δh and angular interval Δθ of the second magnetic head with respect to the first magnetic head, when ≦β is a real number.
A reproducing device characterized in that Δh=(1−α)·Tp/2 Δθ=(1+α)·θ0 /4.