Sheared-beam imaging: an evaluation of its optical compensation of thick atmospheric turbulence.

Sheared-beam imaging (SBI) should compensate the effects of an idealized layer of turbulence located either in a transmitter/detector plane or in an object plane. This motivated the study of optical compensation of SBI in the presence of uniformly distributed turbulence over long horizontal paths in the cases of ideally smooth and ideally rough extended objects. The phase error along a one-dimensional wave front resulting from SBI observation is computed numerically in the long-path regime and is compared with that of an equivalent conventional system for the case of a large smooth object. It is found that for the conditions considered the phase errors of the SBI system are greater than those of a conventional system. In the case of an ideally rough object the extra information furnished by the SBI observations does not lead to data that can be inverted to compute an image by the conventional shearing-interferometric algorithm. The phase errors in imaging a point reflector, however, are perfectly compensated.