Abstract

A simple technique, synthetic-array heterodyne detection, permits an ordinary single-element optical detector to behave as though it were a coherent array. A successful experimental implementation of a synthetic two-pixel array, using a CO2 laser and a single-element HgCdTe photodiode is reported. A different heterodyne local oscillator frequency is incident upon each resolvable region of the detector surface. Thus different regions are mapped to different heterodyne beat frequencies. One can determine where the photons struck the detector surface even though a single electrical connection to the detector is used. This also prevents the destructive interference that occurs when multiple speckles are imaged (akin to spatial diversity). In coherent lidar this permits a larger field of view. An acousto-optic modulator produces the local oscillator frequencies and can achieve good spatial separation of optical frequencies of the order of a megahertz apart.

© 1994 Optical Society of America

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References

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  1. R. T. Menzies, in Laser Monitoring of the Atmosphere E. D. Hinkley, ed. (Springer-Verlag, New York, 1976), p. 298.
  2. P. Gatt, P. P. Wilson, C. Hiemmerman, M. Stickley, in Proceedings of Seventh Conference on Coherent Laser Radar Applications and Technology (Optical Society of America, Washington, D.C., 1993), p. 237.
  3. J. C. Dainty, ed., Laser Speckle and Related Phenomena (Springer-Verlag, New York, 1975), p. 15.
  4. R. G. Frehlich, M. J. Kavaya, Appl. Opt. 30, 5325 (1991).
    [CrossRef] [PubMed]
  5. D. Fink, S. N. Vodopia, Appl. Opt. 15, 453 (1976).
    [CrossRef] [PubMed]
  6. N. Sugimoto, K. P. Chan, D. K. Killinger, Appl. Opt. 30, 2609 (1991).
    [CrossRef] [PubMed]
  7. K. Chan, D. Killinger, Opt. Lett. 17,1237 (1992).
    [CrossRef] [PubMed]

1992 (1)

1991 (2)

1976 (1)

Chan, K.

Chan, K. P.

Fink, D.

Frehlich, R. G.

Gatt, P.

P. Gatt, P. P. Wilson, C. Hiemmerman, M. Stickley, in Proceedings of Seventh Conference on Coherent Laser Radar Applications and Technology (Optical Society of America, Washington, D.C., 1993), p. 237.

Hiemmerman, C.

P. Gatt, P. P. Wilson, C. Hiemmerman, M. Stickley, in Proceedings of Seventh Conference on Coherent Laser Radar Applications and Technology (Optical Society of America, Washington, D.C., 1993), p. 237.

Kavaya, M. J.

Killinger, D.

Killinger, D. K.

Menzies, R. T.

R. T. Menzies, in Laser Monitoring of the Atmosphere E. D. Hinkley, ed. (Springer-Verlag, New York, 1976), p. 298.

Stickley, M.

P. Gatt, P. P. Wilson, C. Hiemmerman, M. Stickley, in Proceedings of Seventh Conference on Coherent Laser Radar Applications and Technology (Optical Society of America, Washington, D.C., 1993), p. 237.

Sugimoto, N.

Vodopia, S. N.

Wilson, P. P.

P. Gatt, P. P. Wilson, C. Hiemmerman, M. Stickley, in Proceedings of Seventh Conference on Coherent Laser Radar Applications and Technology (Optical Society of America, Washington, D.C., 1993), p. 237.

Appl. Opt. (3)

Opt. Lett. (1)

Other (3)

R. T. Menzies, in Laser Monitoring of the Atmosphere E. D. Hinkley, ed. (Springer-Verlag, New York, 1976), p. 298.

P. Gatt, P. P. Wilson, C. Hiemmerman, M. Stickley, in Proceedings of Seventh Conference on Coherent Laser Radar Applications and Technology (Optical Society of America, Washington, D.C., 1993), p. 237.

J. C. Dainty, ed., Laser Speckle and Related Phenomena (Springer-Verlag, New York, 1975), p. 15.

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Figures (3)

Fig. 1
Fig. 1

Synthetic-array concept: the LO is composed of multiple frequencies (ωl,. . . ) that are spatially distinct on the detector. The signal is single frequency with a distorted phase front. Mixing by the detector gives a difference-frequency spectrum. Each frequency maps to a different spatial location on the detector.

Fig. 2
Fig. 2

Experimental arrangement.

Fig. 3
Fig. 3

Focusing onto the detector: the displacement in focal plane is determined by the angle of deflection. The focal plane spot size is determined by the beam diameter (and divergence).

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