15 February 2008 All-optical image sharpness sensor for propagation and imaging
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Abstract
Undesirable turbulence effects present during propagation and imaging through the atmosphere are often reduced using adaptive optics. Many current adaptive optics systems use the Shack-Hartmann wavefront sensor requiring measurement and reconstruction of the incoming wavefront at the pupil plane. Indirect wavefront sensing methods, such as image sharpening, are based on data obtained from the image plane. We are developing an image sharpness sensor based on the Fourier spectrum of an image. High spatial frequencies contain information about the edges and fine detail of the image. Our premise is the maximizing of the high spatial frequencies will sharpen the image. In our setup the Fourier transform of the image is generated optically (and essentially instantaneously) and then various spatial-frequency bands are filtered with an opaque mask. The remaining Fourier spectrum is integrated optically and a sharpness signal is measured with a single photodetector. The collected sharpness value is used in a closed-loop to control the deformable mirror until the sharpness is maximized. We have constructed both a simulation and a laboratory experiment to study the sensor and its performance in an adaptive optics system.
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Kristin N. Walker, Kristin N. Walker, Robert K. Tyson, Robert K. Tyson, } "All-optical image sharpness sensor for propagation and imaging", Proc. SPIE 6878, Atmospheric Propagation of Electromagnetic Waves II, 68780E (15 February 2008); doi: 10.1117/12.768172; https://doi.org/10.1117/12.768172
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