Fourier image sharpness sensor for high-speed wavefront correction

Kristin N. Walker; Robert K. Tyson

doi:10.1117/12.731638

26 September 2007 Fourier image sharpness sensor for high-speed wavefront correction

Kristin N. Walker, Robert K. Tyson

Proceedings Volume 6712, Unconventional Imaging III; 67120F (2007) https://doi.org/10.1117/12.731638
Event: Optical Engineering + Applications, 2007, San Diego, California, United States

Abstract

Conventional adaptive optics systems use direct wavefront sensing such as the Shack-Hartmann sensor requiring a point source such as a natural star or a laser guide star. In situations where a natural guide star isn't available or a laser guide star isn't practical it is beneficial to use an indirect wavefront sensing approach based upon information in the image itself. We are developing an image sharpness sensor using information found in the Fourier spectrum of the image. Since high spatial frequencies contain information about the edges and fine detail of the image our premise is that maximizing the high spatial frequencies will sharpen the image. The Fourier transform of the image is generated optically (and essentially instantaneously) and then various spatial-frequency bands are filtered out with an opaque mask. The remaining Fourier spectrum is integrated optically resulting in a single sharpness signal from a photodetector. The collected sharpness value is used in a closed-loop to control the deformable mirror until the sharpness is maximized. We have created a simulation to study the sensor and its performance in an adaptive optics system; results and limitations will be discussed.

Citation Download Citation

Kristin N. Walker and Robert K. Tyson "Fourier image sharpness sensor for high-speed wavefront correction", Proc. SPIE 6712, Unconventional Imaging III, 67120F (26 September 2007); https://doi.org/10.1117/12.731638

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