Abstract

The conventional feedback of multidither outgoing-wave adaptive optical systems is inoperative in the presence of a featureless target resolved by the transmitter optics. We propose in this paper to define an artificial glint by imaging the target laser pattern on a pinhole aperture. The concept is somewhat obvious, but in turbulence the existing theory on resolution and coherence states that it is restricted to small scintillation strength. Through correlation measurements between the physical-glint return and the artificial-glint irradiance, it is shown that the range of validity is much broader than predicted. Furthermore, tests with a two-degree-of-freedom system operated in turbulence demonstrate that the artificial-glint technique allows effective convergence at propagation distances reaching far into the scintillation–saturation region, i.e., well beyond the theoretical limit.

© 1982 Optical Society of America

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References

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  1. Topical issue on adaptive optics. J. Opt. Soc. Am. 67, 269 (1977).
  2. J. W. Hardy, Proc. IEEE 66, 651 (1978).
    [CrossRef]
  3. J. E. Pearson, R. H. Freeman, H. C. Reynolds, “Adaptive Optical Techniques for Wave-Front Correction”, in Applied Optics and Optical Engineering, Vol. 7, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1979).
    [CrossRef]
  4. J. E. Pearson, W. B. Bridges, S. Hansen, T. A. Nussmeier, M. E. Pedinoff, Appl. Opt. 15, 611 (1976).
    [CrossRef] [PubMed]
  5. T. R. O’Meara, J. Opt. Soc. Am. 67, 306 (1977).
    [CrossRef]
  6. J. H. Shapiro, J. Opt. Soc. Am. 66, 469 (1976).
    [CrossRef]
  7. D. L. Fried, J. Opt. Soc. Am. 55, 1427 (1965).
    [CrossRef]
  8. L. R. Bissonnette, Appl. Opt. 16, 2242 (1977).
    [CrossRef] [PubMed]
  9. L. R. Bissonnette, “Outgoing-Wave Adaptive Optics Systems: Error-Sensing Method in the Case of Extended Targets in Turbulence,” in Proc. Soc. Photo-Opt. Instrum. Eng.365, (1982). Adaptive Optics Systems and Technology, to be published.
  10. J. R. Dunphy, J. R. Kerr, J. Opt. Soc. Am. 63, 981 (1973).
    [CrossRef]
  11. H. T. Yura, “Physical Model for Strong Optical Wave Fluctuations in the Atmosphere,” in AGARD Conference Proceedings No. 183, Optical Propagation in the Atmosphere (National Technical Information Service, Springfield, Va., 1976).
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    [CrossRef]

1978 (1)

J. W. Hardy, Proc. IEEE 66, 651 (1978).
[CrossRef]

1977 (3)

1976 (3)

1973 (1)

1965 (1)

Asakura, T.

Bissonnette, L. R.

L. R. Bissonnette, Appl. Opt. 16, 2242 (1977).
[CrossRef] [PubMed]

L. R. Bissonnette, “Outgoing-Wave Adaptive Optics Systems: Error-Sensing Method in the Case of Extended Targets in Turbulence,” in Proc. Soc. Photo-Opt. Instrum. Eng.365, (1982). Adaptive Optics Systems and Technology, to be published.

Bridges, W. B.

Dunphy, J. R.

Freeman, R. H.

J. E. Pearson, R. H. Freeman, H. C. Reynolds, “Adaptive Optical Techniques for Wave-Front Correction”, in Applied Optics and Optical Engineering, Vol. 7, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1979).
[CrossRef]

Fried, D. L.

Fujii, H.

Hansen, S.

Hardy, J. W.

J. W. Hardy, Proc. IEEE 66, 651 (1978).
[CrossRef]

Kerr, J. R.

Nussmeier, T. A.

O’Meara, T. R.

Pearson, J. E.

J. E. Pearson, W. B. Bridges, S. Hansen, T. A. Nussmeier, M. E. Pedinoff, Appl. Opt. 15, 611 (1976).
[CrossRef] [PubMed]

J. E. Pearson, R. H. Freeman, H. C. Reynolds, “Adaptive Optical Techniques for Wave-Front Correction”, in Applied Optics and Optical Engineering, Vol. 7, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1979).
[CrossRef]

Pedinoff, M. E.

Reynolds, H. C.

J. E. Pearson, R. H. Freeman, H. C. Reynolds, “Adaptive Optical Techniques for Wave-Front Correction”, in Applied Optics and Optical Engineering, Vol. 7, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1979).
[CrossRef]

Shapiro, J. H.

Shindo, Y.

Yura, H. T.

H. T. Yura, “Physical Model for Strong Optical Wave Fluctuations in the Atmosphere,” in AGARD Conference Proceedings No. 183, Optical Propagation in the Atmosphere (National Technical Information Service, Springfield, Va., 1976).

Appl. Opt. (2)

J. Opt. Soc. Am. (6)

Proc. IEEE (1)

J. W. Hardy, Proc. IEEE 66, 651 (1978).
[CrossRef]

Other (3)

J. E. Pearson, R. H. Freeman, H. C. Reynolds, “Adaptive Optical Techniques for Wave-Front Correction”, in Applied Optics and Optical Engineering, Vol. 7, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1979).
[CrossRef]

L. R. Bissonnette, “Outgoing-Wave Adaptive Optics Systems: Error-Sensing Method in the Case of Extended Targets in Turbulence,” in Proc. Soc. Photo-Opt. Instrum. Eng.365, (1982). Adaptive Optics Systems and Technology, to be published.

H. T. Yura, “Physical Model for Strong Optical Wave Fluctuations in the Atmosphere,” in AGARD Conference Proceedings No. 183, Optical Propagation in the Atmosphere (National Technical Information Service, Springfield, Va., 1976).

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Figures (8)

Fig. 1
Fig. 1

Diagram of the experimental setup for the measurement of the statistical correlation between the turbulent target irradiance viewed by two imaging systems through turbulence and through nonturbulent air: BE, beam expander; M, plane mirror; D, diffuser; L1, f = 300 mm, f/4; L2, f = 200 mm, f/2.5; P1, pinhole aperture, 100 μm; P2, pinhole aperture, variable; PM1 and PM2, photomultipliers.

Fig. 2
Fig. 2

Measured correlation coefficient defined by Eq. (9) as a function of the diameter D of the target spot probed through the nonturbulent air; Cn = 1.2 × 10−4 m−1/3; z = 1.63 m; z/zA = 2.15.

Fig. 3
Fig. 3

Same as Fig. 2 except for z = 2.95 m and z/zA = 3.9.

Fig. 4
Fig. 4

Diagram of the experimental setup to test the proposed imaging technique on a tilt-compensation MDOW adaptive system; M, D, L1, P1, L2, P2, PM1, and PM2 as in Fig. 1.

Fig. 5
Fig. 5

Sample time recordings of the irradiance signal detected by the reference imaging system. Time zero corresponds to the closing of the servo loop: (a) the artificial glint is defined on the axis of the open-loop beam; (b) the artificial glint is defined on the side of the open-loop beam at a radial position equal to 3 times the 1/e radius of the open-loop target irradiance profile; Cn = 1.2 × 10−4 m−1/3; z = 2.95 m; z/zA = 3.9.

Fig. 6
Fig. 6

Comparison of the average irradiance measured under closed-loop operation (data points) to the open-loop beam profile (continuous curve); z/zA = 0.45.

Fig. 7
Fig. 7

Same as Fig. 6, except that z/zA = 3.9. Open symbols: irradiance measured by the imaging system looking through turbulence. Boldface symbols: irradiance measured by the reference imaging system.

Fig. 8
Fig. 8

Dynamic (open symbols) and static (boldface symbols) tracking limits of the two-degree-of-freedom MDOW adaptive system of Fig. 4 as a function of z/zA. Dd and Ds are defined in the main text. ○ and ●: z = 1.0 m, Dt = 6.0 mm; △ and ▲: z = 2.0 m, Dt = 8.4 mm; ▽ and ▼: z = 2.9 m, Dt = 9.6 mm, where Dt is the e−4 diameter of the beam at the entrance of the turbulence generator.

Equations (9)

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L = ( λ z ) 2 / π ρ 0 2 ,
ρ 0 = ( 1.09 k 2 z C n 2 / n 0 2 ) - 3 / 5 ,
S = π ρ 0 2 .
L < S ,
( λ z / π ρ 0 2 ) 2 = ( 1.94 k 7 / 6 z 11 / 6 C n 2 / n 0 2 ) 12 / 5 < 1.
z A = n 0 12 / 11 / C n 12 / 11 k 7 / 11 ,
( z / z A ) 22 / 5 < 0.2 ,
D = P 2 / ( i / o ) 2 .
C = ( I 1 I 2 ¯ - I ¯ 1 I ¯ 2 ) / ( I ¯ 1 2 - I ¯ 1 2 ) ( I ¯ 2 2 - I ¯ 2 2 ) ,

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