Abstract

The design of high density digital optical storage systems requires a thorough understanding of the various interactions affecting the integrity of both data and servo signals under various readout conditions. Here, a 2-D Fourier optic model of the readout system is presented along with an efficient calculational procedure based on 2-D fast Fourier transforms (FFT). The model is utilized to examine the effects of data density, focus errors, tracking errors, lens fill conditions, phase pit depth, etc. on the quality of the readout signal. The derivation of servo signals is also studied through the modeling of a simple diffraction based scheme. It is shown that a reasonably constant servo signal (small variations with focus errors, track depth, or added amplitude data) can be generated by this technique provided that a λ/8 phase groove is present. The same technique can be shown to be unacceptable if an amplitude or λ/4 phase groove is utilized.

© 1983 Optical Society of America

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References

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  1. D. Maydan, Bell Syst. Tech. J. 50, 1761 (1971).
  2. K. Bulthuis et al., IEEE Spectrum 26 (Aug.1979).
  3. G. Kenney et al., IEEE Spectrum 33 (Feb.1979).
  4. H. H. Hopkins, J. Opt. Soc. Am. 69, 4 (1979).
    [CrossRef]
  5. C. J. R. Sheppard, A. Choudhury, Opt. Acta 24, 1051 (1977).
    [CrossRef]
  6. T. Wilson, Appl. Phys. 22, 119 (1980).
    [CrossRef]
  7. A. E. Bell, F. W. Spong, IEEE J. Quantum Electron. 14, 487 (1978).
    [CrossRef]
  8. D. Goodman, IBM Research; private communicatins.
  9. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), p. 48.
  10. A. Atalar, J. Appl. Phys. 49, 5130 (1978).
    [CrossRef]
  11. D. G. Howe, J. J. Wrobel, J. Vac. Sci. Technol. 18(1), 92 (1981).
    [CrossRef]
  12. J. Drexler, J. Vac. Sci. Technol. 18(1), 87 (1981).
    [CrossRef]
  13. V. Jipson, C. Jones, J. Vac. Sci. Technol. 18(1), 105 (1981).
    [CrossRef]
  14. M. G. Carasso, A. Huijser, in Technical Digest, Conference on Lasers and Electrooptic Systems (Optical Society of America, Washington, D.C., 1982), paper WH1.

1981 (3)

D. G. Howe, J. J. Wrobel, J. Vac. Sci. Technol. 18(1), 92 (1981).
[CrossRef]

J. Drexler, J. Vac. Sci. Technol. 18(1), 87 (1981).
[CrossRef]

V. Jipson, C. Jones, J. Vac. Sci. Technol. 18(1), 105 (1981).
[CrossRef]

1980 (1)

T. Wilson, Appl. Phys. 22, 119 (1980).
[CrossRef]

1979 (3)

K. Bulthuis et al., IEEE Spectrum 26 (Aug.1979).

G. Kenney et al., IEEE Spectrum 33 (Feb.1979).

H. H. Hopkins, J. Opt. Soc. Am. 69, 4 (1979).
[CrossRef]

1978 (2)

A. E. Bell, F. W. Spong, IEEE J. Quantum Electron. 14, 487 (1978).
[CrossRef]

A. Atalar, J. Appl. Phys. 49, 5130 (1978).
[CrossRef]

1977 (1)

C. J. R. Sheppard, A. Choudhury, Opt. Acta 24, 1051 (1977).
[CrossRef]

1971 (1)

D. Maydan, Bell Syst. Tech. J. 50, 1761 (1971).

Atalar, A.

A. Atalar, J. Appl. Phys. 49, 5130 (1978).
[CrossRef]

Bell, A. E.

A. E. Bell, F. W. Spong, IEEE J. Quantum Electron. 14, 487 (1978).
[CrossRef]

Bulthuis, K.

K. Bulthuis et al., IEEE Spectrum 26 (Aug.1979).

Carasso, M. G.

M. G. Carasso, A. Huijser, in Technical Digest, Conference on Lasers and Electrooptic Systems (Optical Society of America, Washington, D.C., 1982), paper WH1.

Choudhury, A.

C. J. R. Sheppard, A. Choudhury, Opt. Acta 24, 1051 (1977).
[CrossRef]

Drexler, J.

J. Drexler, J. Vac. Sci. Technol. 18(1), 87 (1981).
[CrossRef]

Goodman, D.

D. Goodman, IBM Research; private communicatins.

Goodman, J. W.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), p. 48.

Hopkins, H. H.

Howe, D. G.

D. G. Howe, J. J. Wrobel, J. Vac. Sci. Technol. 18(1), 92 (1981).
[CrossRef]

Huijser, A.

M. G. Carasso, A. Huijser, in Technical Digest, Conference on Lasers and Electrooptic Systems (Optical Society of America, Washington, D.C., 1982), paper WH1.

Jipson, V.

V. Jipson, C. Jones, J. Vac. Sci. Technol. 18(1), 105 (1981).
[CrossRef]

Jones, C.

V. Jipson, C. Jones, J. Vac. Sci. Technol. 18(1), 105 (1981).
[CrossRef]

Kenney, G.

G. Kenney et al., IEEE Spectrum 33 (Feb.1979).

Maydan, D.

D. Maydan, Bell Syst. Tech. J. 50, 1761 (1971).

Sheppard, C. J. R.

C. J. R. Sheppard, A. Choudhury, Opt. Acta 24, 1051 (1977).
[CrossRef]

Spong, F. W.

A. E. Bell, F. W. Spong, IEEE J. Quantum Electron. 14, 487 (1978).
[CrossRef]

Wilson, T.

T. Wilson, Appl. Phys. 22, 119 (1980).
[CrossRef]

Wrobel, J. J.

D. G. Howe, J. J. Wrobel, J. Vac. Sci. Technol. 18(1), 92 (1981).
[CrossRef]

Appl. Phys. (1)

T. Wilson, Appl. Phys. 22, 119 (1980).
[CrossRef]

Bell Syst. Tech. J. (1)

D. Maydan, Bell Syst. Tech. J. 50, 1761 (1971).

IEEE J. Quantum Electron. (1)

A. E. Bell, F. W. Spong, IEEE J. Quantum Electron. 14, 487 (1978).
[CrossRef]

IEEE Spectrum (2)

K. Bulthuis et al., IEEE Spectrum 26 (Aug.1979).

G. Kenney et al., IEEE Spectrum 33 (Feb.1979).

J. Appl. Phys. (1)

A. Atalar, J. Appl. Phys. 49, 5130 (1978).
[CrossRef]

J. Opt. Soc. Am. (1)

J. Vac. Sci. Technol. (3)

D. G. Howe, J. J. Wrobel, J. Vac. Sci. Technol. 18(1), 92 (1981).
[CrossRef]

J. Drexler, J. Vac. Sci. Technol. 18(1), 87 (1981).
[CrossRef]

V. Jipson, C. Jones, J. Vac. Sci. Technol. 18(1), 105 (1981).
[CrossRef]

Opt. Acta (1)

C. J. R. Sheppard, A. Choudhury, Opt. Acta 24, 1051 (1977).
[CrossRef]

Other (3)

M. G. Carasso, A. Huijser, in Technical Digest, Conference on Lasers and Electrooptic Systems (Optical Society of America, Washington, D.C., 1982), paper WH1.

D. Goodman, IBM Research; private communicatins.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968), p. 48.

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Figures (17)

Fig. 1
Fig. 1

Simplified schematic of the readout optics for an optical disk system.

Fig. 2
Fig. 2

Normalized focal plane light intensity distribution for three lens fill conditions.

Fig. 3
Fig. 3

Peak light intensity at the focal plane as a function of lens fill conditions. Note that the optimum peak intensity occurs when the input field distribution is e−1.25 at the edge of the lens aperture.

Fig. 4
Fig. 4

Section of a typical disk reflectivity function. d x and d y represent the axes of spots while s x and s y correspond to the mark spacing along the track and perpendicular to the track, respectively. Note that in general the spots can be elliptical, but the ones shown here are circular.

Fig. 5
Fig. 5

Optical contrast vs linear spot density with normalized mark size as a parameter.

Fig. 6
Fig. 6

Measured and theoretical contrast vs linear density for a thin film metal disk: N.A. = 0.6; λ = 647.1 nm; b = 600 nm (measured), d x = d y = 600 nm (measured).

Fig. 7
Fig. 7

Optical contrast vs tracking error with normalized mark size as a parameter.

Fig. 8
Fig. 8

Optical contrast vs tracking error for d/b = 1.0. Of note is the fact that the track-to-track cross talk is reduced by >50 dB when s y = 1.3 b. This is excessive for digital storage applications.

Fig. 9
Fig. 9

Readout signal vs position for three focal positions: d/b = 1.0; s/b = 1.5, N.A. = 0.5.

Fig. 10
Fig. 10

Readout signal vs position for pure phase pits (λ/4 deep) of various sizes.

Fig. 11
Fig. 11

Peak readout contrast vs phase pit diameter and peak readout contrast vs amplitude pit diameter. Note that the phase pit has an optimum size from a contrast point of view.

Fig. 12
Fig. 12

Peak readout contrast vs phase pit depth: d/b = 0.6, s/b = 1.5.

Fig. 13
Fig. 13

Intensity distribution at the output plane as the read beam is swept across a λ/8 track. Note the clear asymmetric distribution for off-track conditions. All distributions have been normalized, but the relative signal strengths are a = 1.0, b = 2.3, c = 3.8, d = 4.0.

Fig. 14
Fig. 14

Calculated tracking error signal as a function of track position for a λ/8 groove at three focal positions. Note that the error signal is not dramatically affected by small focus errors.

Fig. 15
Fig. 15

Calculated tracking error signal as a function of track position for grooves with depths of 0.10, 0.125, and 0.15 wavelengths. Note that while the derived servo signal does change with groove depth, it is not overly sensitive.

Fig. 16
Fig. 16

Complex disk reflectivity function for an object consisting of amplitude pits written onto λ/8 grooves.

Fig. 17
Fig. 17

Calculated tracking error signal as a function of track position for the object of Fig. 16. Results are shown for three focal positions.

Equations (12)

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u i + ( x i , y i ) = c exp - ( x i 2 a x 2 + y i 2 a y 2 ) ,
u f + ( x f , y f ) = F 2 { P ( x i , y i ) u i + ( x i , y i ) } S x = x f / λ F , S y = y f / λ F ,
F 2 { u ( x , y ) } = - - u ( x , y ) exp { i 2 π ( S x x + S y y ) } d x d y .
A + ( x i λ F , y i λ F , O ) = F 2 { u f + ( x f , y f ) } S x = x i / λ F , S y = y i / λ F ,
A + ( x i λ F , y i λ F , O ) = P ( - x i , - y i ) u i + ( - x i , - y i ) ,
A + ( x i λ F , y i λ F , ɛ ) = A + ( x i λ F , y i λ F , O ) × exp { i 2 π ɛ λ 1 - ( x i F ) 2 - ( y i F ) 2 } .
u f + { x f , y f , ɛ } = F - 2 { A + ( x i λ F , y i λ F , ɛ ) } .
u f - ( x f , y f , ɛ ) = u f + ( x f , y f , ɛ ) × R ( x f - x s , y f - y s ) ,
A - ( x i λ F , y i λ F , ɛ ) = F 2 { u - ( x f , y f , ɛ ) }
A - ( x i λ F , y i λ F , O ) = A - ( x i λ F , y i λ F , ɛ ) × exp { - i 2 π ɛ λ 1 - ( x i F ) 2 - ( y i F ) 2 } .
u i - ( x i , y i ) = A - ( x i λ F , y i λ F , O ) P ( - x i , - y i ) ,
v ( x s , y s ) = - - u i - ( x i , y i ) u i - * ( x i , y i ) D ( x i , y i ) d x i d y i ,

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