Proceedings PaperResolution limits for high-resolution imaging lidar
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We investigate the way laser-speckle noise and limited signal power affect the quality of images reconstructed from diffraction field data obtained with a pupil-plane array of optical heterodyne detectors. Modeling the detected signal from each detector sub-element as a circular-complex Gaussian random variable and taking into account the random amplitudes of the detected signals arising from laser-speckle effects, we compute the SNR of the Fourier spectrum of the coherent intensity image formed from the array of heterodyne field measurements. The resulting SNR expression is compared to that obtained earlier, P.S. Idell (1988), for the same quantity estimated from photocount-limited, focal plane detector measurements. This comparison shows that the spatial frequency SNR performance of both systems is identical when the systems are operated at high signal-level operating conditions (number of signal photocounts per speckle much greater than one). When signal levels drop significantly below one signal photocount/speckle, we find that focal plane imaging performs somewhat better at estimating all but the very highest spatial frequencies.