Abstract

Photons emitted by a narrow laser beam are followed through multiple scattering events in the ocean until registered by a detector at the source position. A realistic ocean model is used which takes account not only of molecular scattering (Rayleigh) and absorption, but also scattering and absorption by the hydrosols (Mie). The single scattering function for the hydrosols is calculated from Mie theory assuming a relative index of refraction of 1.15 and a size distribution with a modal radius of 3 μ. Targets with various surface albedos (A) are introduced at various distances from the source. The three-dimensional path of the photons is followed by a Monte Carlo technique. When A ≥ 0.02 the returned flux per unit photon path length from the targets is greater than the background from the laser beam for any target distance. The returned flux is plotted as a function of the photon path length. In practice the detection distance is limited by the lowest flux that can be detected and the background of natural light. Inhomogeneities in the optical properties of the ocean can also be measured in this way.

© 1972 Optical Society of America

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References

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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]

1971 (1)

1969 (2)

1968 (5)

1967 (1)

G. W. Kattawar, G. N. Plass, Appl. Opt. 6,1377, 1549 (1967).
[CrossRef] [PubMed]

1963 (1)

R. S. Fraser, W. H. Walker, J. Opt. Soc. Am. 58, 1636 (1963).

1954 (1)

W. V. Burt, Tellus 6, 229 (1954).
[CrossRef]

1952 (1)

W. R. G. Atkins, H. H. Poole, Proc. Roy. Soc. (London) B140, 321 (1952).

1945 (1)

1939 (1)

Y. LeGrand, Ann. Inst. Ocean. 19, 393 (1939).

Atkins, W. R. G.

W. R. G. Atkins, H. H. Poole, Proc. Roy. Soc. (London) B140, 321 (1952).

Beardsley, G. F.

Burt, W. V.

W. V. Burt, Tellus 6, 229 (1954).
[CrossRef]

Fraser, R. S.

R. S. Fraser, W. H. Walker, J. Opt. Soc. Am. 58, 1636 (1963).

Hulbert, E. O.

Kattawar, G. W.

LeGrand, Y.

Y. LeGrand, Ann. Inst. Ocean. 19, 393 (1939).

Plass, G. N.

Poole, H. H.

W. R. G. Atkins, H. H. Poole, Proc. Roy. Soc. (London) B140, 321 (1952).

van de Hulst, H. C.

H. C. van de Hulst, Light Scattering by Small Particles (Wiley, New York, 1957).

Walker, W. H.

R. S. Fraser, W. H. Walker, J. Opt. Soc. Am. 58, 1636 (1963).

Ann. Inst. Ocean. (1)

Y. LeGrand, Ann. Inst. Ocean. 19, 393 (1939).

Appl. Opt. (8)

J. Opt. Soc. Am. (3)

Proc. Roy. Soc. (London) (1)

W. R. G. Atkins, H. H. Poole, Proc. Roy. Soc. (London) B140, 321 (1952).

Tellus (1)

W. V. Burt, Tellus 6, 229 (1954).
[CrossRef]

Other (1)

H. C. van de Hulst, Light Scattering by Small Particles (Wiley, New York, 1957).

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Figures (4)

Fig. 1
Fig. 1

The returned flux from a laser source as a function of the photon path length in meters. The half angles of the source and detector are 10−3 rad and 5 × 10−3 rad, respectively. Calculated points are shown for the returned flux including all orders of multiple scattering for targets at 10 m, 30 m, 50 m, and 80 m. The returned flux from the target is shown for various assumed values of the surface albedo (A). The returned flux is normalized per unit flux from the source and per meter of photon path length. Only Rayleigh scattering is taken into account.

Fig. 2
Fig. 2

Returned flux as a function of photon path length in meters. Both Rayleigh and hydrosol scattering centers are assumed. The ratio of the total Rayleigh attenuation length (βT,R) to the total attenuation length from both Rayleigh centers and hydrosols (βT), β T / β T = 1 2. See caption to Fig. 1.

Fig. 3
Fig. 3

Returned flux as a function of photon path length in meters. β T / β T = 1 14. Targets are assumed at 2 m, 5 m, and 10 m. See caption to Fig. 1.

Fig. 4
Fig. 4

Returned flux as a function of photon path length in meters. The target is assumed at 50 m. Calculated points for a homogeneous ocean with β T / β T = 1 2 are indicated by squares. Open circles are the same except for a turbid layer ( β T / β T = 1 5 ) from 25 < z < 30 m, where z is the distance from the source. Crosses are the same model, except that the turbid layer is from 40 < z < 50 m. Solid circles indicate a model with five different layers, each with different optical properties: β T / β T = 1 2, 0 < z < 10 m; β T / β T = 1 3, 10 < z < 20 m; β T / β T = 1 4, 20 < z < 30 m; β T / β T = 1 5, 30 < z < 40 m; β T / β T = 1 6, 40 < z < 50 m. See caption to Fig. 1.

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