Abstract

A method is described which allows an increase of information density on optically read disks by a reduction of the track spacing by a factor of 2. The cross talk between neighboring tracks is maintained at an acceptable level by modulating from track to track the depth of the relief pattern on the disk. By an appropriate readout method (a compromise between differential and integral detection), the signals from neighboring tracks are suppressed. The layout of such a disk and the possible geometries of the relief pattern are indicated.

© 1983 Optical Society of America

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References

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  1. G. Bouwhuis, J. Braat, “Recording and Reading of Information on Optical Disks,” in Applied Optics and Optical Engineering, Vol. 9, R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1983).
    [CrossRef]
  2. C. Bricot et al.IEEE Trans. Cons. Electron. CE-22, 304 (1976); R. Adler, IEEE Trans. Broadcast Telev. Receivers 20, 230 (1974); G. Hrbek, J. Soc. Motion Pict. Telev. Eng. 83, 580 (1974).
    [CrossRef]
  3. H. H. Hopkins, J. Opt. Soc. Am. 69, 4 (1979).
    [CrossRef]

1979

1976

C. Bricot et al.IEEE Trans. Cons. Electron. CE-22, 304 (1976); R. Adler, IEEE Trans. Broadcast Telev. Receivers 20, 230 (1974); G. Hrbek, J. Soc. Motion Pict. Telev. Eng. 83, 580 (1974).
[CrossRef]

Bouwhuis, G.

G. Bouwhuis, J. Braat, “Recording and Reading of Information on Optical Disks,” in Applied Optics and Optical Engineering, Vol. 9, R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1983).
[CrossRef]

Braat, J.

G. Bouwhuis, J. Braat, “Recording and Reading of Information on Optical Disks,” in Applied Optics and Optical Engineering, Vol. 9, R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1983).
[CrossRef]

Bricot, C.

C. Bricot et al.IEEE Trans. Cons. Electron. CE-22, 304 (1976); R. Adler, IEEE Trans. Broadcast Telev. Receivers 20, 230 (1974); G. Hrbek, J. Soc. Motion Pict. Telev. Eng. 83, 580 (1974).
[CrossRef]

Hopkins, H. H.

IEEE Trans. Cons. Electron.

C. Bricot et al.IEEE Trans. Cons. Electron. CE-22, 304 (1976); R. Adler, IEEE Trans. Broadcast Telev. Receivers 20, 230 (1974); G. Hrbek, J. Soc. Motion Pict. Telev. Eng. 83, 580 (1974).
[CrossRef]

J. Opt. Soc. Am.

Other

G. Bouwhuis, J. Braat, “Recording and Reading of Information on Optical Disks,” in Applied Optics and Optical Engineering, Vol. 9, R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1983).
[CrossRef]

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Figures (12)

Fig. 1
Fig. 1

One-dimensional groove pattern with grooves of width w and period q.

Fig. 2
Fig. 2

Far-field amplitude distribution when illuminating the groove pattern with a conical light beam.

Fig. 3
Fig. 3

Phase difference ψ0 between the zeroth and first orders of the groove pattern as a function of the optical depth of the grooves.

Fig. 4
Fig. 4

Diffracted orders and their overlapping regions projected onto the detectors D1 and D2. In the case of a reflective disk system the returning light beam is limited by the circle A0.

Fig. 5
Fig. 5

Detection circuit that introduces electronic phase shifts between the signals originating from the split detectors D1 and D2.

Fig. 6
Fig. 6

Geometry of the disk pattern used in the numerical program CROSST.

Fig. 7
Fig. 7

Phase difference between the zeroth and first tangential orders of a videodisk pattern as a function of wall inclination of the pits. The disk is scanned in reflection through the substrate. Curve 1 applies to a disk with a maximum pit depth of 115 nm; curve 2 applies to a disk with a depth of 145 nm. The wavelength of the light is 633 nm, and the refractive index of the substrate is 1.50.

Fig. 8
Fig. 8

Relative power of the signals at frequencies ν1, ν2, ν3, ν4, and ν5 as a function of the radial position of the scanning light spot. Taking into account small residual tracking errors, cross talk is defined as the power ratio between the spurious signal and the desired signal. The spatial frequency f sp of the pits is 1000/mm. The cutoff frequency of the optics is 1400/mm.

Fig. 9
Fig. 9

Disk with tracks of different average depth. (a) readout is optimum for the shallow tracks (δ = 45°); (b) deep tracks are detected in an optimum way (δ = −45°). The spatial frequency of the pits again is 1000/mm.

Fig. 10
Fig. 10

Same as for Fig. 9, an exception being made for the angles δ, which now equal ±75°. The spatial frequency is now 250/mm.

Fig. 11
Fig. 11

Classical MTF of a video disk player and the modified one under the influence of the frequency-dependent phase shift between the detectors D1 and D2.

Fig. 12
Fig. 12

Phase shift to be applied between the two detectors D1 and D2 for an optimum cross-talk reduction as a function of the spatial frequency of the pits.

Equations (16)

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A 0 = 1 + w q [ exp ( i ϕ ) - 1 ] , A n = w q [ exp ( i ϕ ) - 1 ] sinc ( π n w q ) exp ( 2 π i n ν t ) ,
tan ψ 0 = - 1 / [ tan ( ϕ 2 ) ( 1 - 2 w q ) ] .
A ( x , y , t ) = n A n ( x , y , t ) ,
I ( x , y , t ) = | n A n ( x , y , t ) | 2 .
S 1 ( t ) = D 1 I ( x , y , t ) d x d y , S 2 ( t ) = D 2 I ( x , y , t ) d x d y .
A 0 = A 0 , A + 1 = A 1 exp [ i ( ψ 0 + 2 π ν t ) ] , A - 1 = A 1 exp [ i ( ψ 0 - 2 π ν t ) ] ,
S 1 ( t ) = b 1 A 0 2 + ( b 1 + b 2 ) A 1 2 + 2 b 1 A 0 A 1 cos ( 2 π ν t - ψ 0 ) + 2 b 2 A 0 A 1 cos ( 2 π ν t + ψ 0 ) + 2 b 2 A 1 2 cos ( 4 π ν t ) , S 2 ( t ) = b 1 A 0 2 + ( b 1 + b 2 ) A 1 2 + 2 b 1 A 0 A 1 cos ( 2 π ν t + ψ 0 ) + 2 b 2 A 0 A 1 cos ( 2 π ν t - ψ 0 ) + 2 b 2 A 1 2 cos ( 4 π ν t ) ,
S 1 ( t ) 2 A 0 A 1 [ ( b 1 - b 2 ) cos ( 2 π ν t - ψ 0 ) + 2 b 2 cos ψ 0 cos 2 π ν t + b 2 A 0 A 1 cos ( 4 π ν t ) ] , S 2 ( t ) 2 A 0 A 1 [ ( b 1 - b 2 ) cos ( 2 π ν t + ψ 0 ) + 2 b 2 cos ψ 0 cos 2 π ν t + b 2 A 0 A 1 cos ( 4 π ν t ) ] .
S 1 * ( t ) cos ( 2 π ν t + δ - ψ 0 ) , S 2 * ( t ) cos ( 2 π ν t - δ + ψ 0 ) ,
S ( t ) cos ( ψ 0 - δ ) cos ( π ν t ) .
S ν 1 ( t ) cos ( ψ 1 - δ ) cos ( 2 π ν 1 t ) , S ν 2 ( t ) cos ( ψ 2 - δ ) cos ( 2 π ν 2 t ) ,
S ν 1 ( t ) cos ( ψ 1 - δ ) cos ( 2 π ν 1 t ) + 2 cos ( ψ 2 - δ ) cos ( 2 π ν 2 t ) + 3 cos ( ψ 2 - δ ) cos ( 2 π ν 3 t ) ,
S ν 1 ( t ) cos ( ψ 1 - ψ 2 + π 2 ) cos ( 2 π ν 1 t ) .
S ν 2 ( t ) cos ( ψ 2 - δ ) cos ( 2 π ν 2 t ) + 1 cos ( ψ 1 - δ ) cos ( 2 π ν 1 t ) + .
S ν 2 ( t ) cos ( ψ 1 - ψ 2 + π 2 ) cos ( 2 π ν 2 t ) .
A ( r , ϕ ) = exp ( - σ 2 r 2 ) exp [ 2 π i W ( r , ϕ ) ] ,

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