31 May 1994 Compensated imaging over arcminutes with fringes in the sodium layer
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Abstract
In order to increase the corrected field of view in multi-conjugate adaptive optics we suggest a method for measuring and separating the contribution of atmospheric turbulent layers. The sodium layer serves as a huge screen, on which we project a wide fringe pattern from a single laser on the ground. A modified Hartmann-Shack sensor is employed to detect deformations in the pattern: sections of the fringe pattern are imaged by a lenslet array onto a large-format camera. Low layer turbulence causes overall shift of the fringe pattern in each lenslet, while high altitude turbulence results in internal deformations in the pattern, which are detected by that section of the camera which is behind each lenslet. Parallel Fourier analyses for the different lenslets allows separation of the atmospheric layers: the periodicity of the fringes lends itself to digital demodulation, which yields the deformations in the fringe. We present a statistical error analysis and simulations, showing good performance over a field of view of 80', compared to the performance expected of a conventional single sodium beacon, single adaptive mirror system.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Erez N. Ribak, Yael Baharav, Joseph Shamir, "Compensated imaging over arcminutes with fringes in the sodium layer", Proc. SPIE 2201, Adaptive Optics in Astronomy, (31 May 1994); doi: 10.1117/12.176043; https://doi.org/10.1117/12.176043
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