Analysis and simulation of a synthetic-aperture technique for imaging through a turbulent medium

Holmes, Richard B.; Ma, Shuang; Bhowmik, Anup; Greninger, Charles E.

doi:10.1364/josaa.13.000351

Cited by 42 publications

(13 citation statements)

References 14 publications

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“…This effect was theoretically predicted in Ref. 1 0. The degradation effect of turbulence on laser speckle pattern is a consequence of the Van Cittert-Zernike theorem generalized to randomly inhomogeneous medium.…”

Section: Simulation Resultssupporting

confidence: 73%

Effect of turbulence on downlink and horizontal path on high-order coherence moments in Fourier telescopy system

et al. 2002

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Fourier Telescopy is an active laser-based imaging method for high-resolution imaging of dim objects in Geosynchronous (GEO) orbit. The Geo Light Imaging National Testbed (GLINT) will be build to demonstrate new powerful imaging capability. Several processes including laser speckle, atmospheric turbulence on the downlink and 1-km horizontal path, as well as Poisson shot noise can contribute to the measurement error of the Fourier phase of the object and thus degrade the reconstructed image. We investigated the impact of three processes including laser speckle, turbulence, and Poisson shot noise on the measurement error of the Fourier phase. We introduced the concept of powerin-the-bucket receiver and applied this concept to the receiver in the Fourier telescopy system. We found that the powerin-the-bucket receiver cancels the effects of turbulence on the horizontal path on the Fourier telescopy system. We evaluated variance of the real and imaginary parts of the triple product, as well as variance of the Fourier phase of the object by using a numerical simulation code. The twelfth moment of the optical filed was calculated in the presence of laser speckle, atmospheric turbulence, and Poisson shot noise. Simulation results confirmed that Fourier telescopy system is immune to the effects of turbulence on the horizontal path. It also showed that the effect of turbulence on the downlink path on the triple product is small. Laser speckle contributes strongly to the variations of the real part of the triple product and weakly to the imaginary part. Statistical properties of the triple product depend on the noise source. Poisson shot noise and laser speckle produce the main contribution to the variance of the triple product and measurement error of the object Fourier phase. Phase variance reduces with increasing the number of heliostats, number of pulses, fringe visibility, and fringe signal-to-noise ratio. For 40 heliostat receivers, 100 averaged pulses, and all considered fringe SNRs and fringe visibilities the phase variance caused by Poisson noise, laser speckle, and turbulence on the downlink path is significantly less than 0.36, which corresponds to the phase measurement accuracy of Ill 0 of the wave.

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Section: Simulation Resultssupporting

confidence: 73%

Effect of turbulence on downlink and horizontal path on high-order coherence moments in Fourier telescopy system

et al. 2002

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“…A recent variant of these techniques, Fourier Telescopy, does in fact take best advantage of such active signals, attaining shot-noise limited performance with existing hardware, even for very distant faint objects. [12] This technique has been experimentally verified. [13] Complex images have been formed successfully using solely phase closure, using a complex reconstructor.…”

Section: N1'roduchonmentioning

confidence: 99%

<title>Reconstruction of images of deep-space objects using Fourier telescopy</title>

Holmes

Brinkley

1999

SPIE Proceedings

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Fourier Telescopy is an imaging method that can form images of very dim objects with angular resolution of a few nanoradians, attained by means of a synthetic aperture that overcomes the effects of intervening aberrations using mathematical algorithms akin to that of long-baseline radio astronomy. The algorithm makes use of phase closure and advanced wavefront reconstruction techniques from adaptive optics and Knox-Thompson image reconstruction. The imaging technique is active and so can be used even with faint objects. The imaging technique is active and encodes the information in the temporal instead of spatial domain, allowing imaging of faint objects with extremely large, low-cost receivers. An implementation for deep space imaging is shown; it uses large-area solar collectors for the receiver, yielding a low-cost, highperformance design. Simulated images are shown for a potential realization ofthe system.

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“…The most direct way to provide this information is to perform the proper additional measurements that provide the needed data. Such data can be provided using phase closure, for example, in which three baselines are sampled simultaneously [3]. Phase closure can also be applied if more than 3 apertures are used by applying the bispectrum technique [11,6].…”

Section: Color Restoration and Synthetic Aperturesmentioning

confidence: 99%

“…The former aberrations are manifested as phase errors in the interference measurement. Means for reducing or eliminating these aberrations include phase closure with non-redundant apertures [3], the bispectrum [4][5][6], heterodyne sampling [7], phase diversity [8], spectral techniques [9,2], and various hybrids. Other sparse array techniques have been proposed in conjunction with active laser ifiumination for non-astronomical applications [lO], although such active techniques typically use only one laser color.…”

Section: Introductionmentioning

confidence: 99%

<title>Color restoration for astronomical applications</title>

Holmes¹,

Abatzoglou

1997

SPIE Proceedings

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A technique for polychromatic image restoration is proposed in the context of high-resolution synthetic aperture imaging. Noise and aberrations from the atmosphere are included in the analysis. The technique is simulated and successful image restorations are shown for objects with spectrally-varying radiance profiles. It is concluded that color restoration requires some additional information, e.g., phase closure or multiple-frame averaging, to overcome aberrations for robust image formation.

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Analysis and simulation of a synthetic-aperture technique for imaging through a turbulent medium

Cited by 42 publications

References 14 publications

Effect of turbulence on downlink and horizontal path on high-order coherence moments in Fourier telescopy system

Effect of turbulence on downlink and horizontal path on high-order coherence moments in Fourier telescopy system

<title>Reconstruction of images of deep-space objects using Fourier telescopy</title>

<title>Color restoration for astronomical applications</title>

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