Heterodyne wavefront sensor

Abstract

An optical heterodyne wavefront sensor uses a radio frequency (RF) signal for measuring an optical wavefront having a state of phase that differs throughout its aperture. It comprises a lens, optical fiber and optical frequency shifter arrangement to develop a reference optical wavefront having substantially the same phase throughout and that is shifted in frequency by an amount corresponding to the RF. A beam combiner interferometrically combines the optical wavefront and the shifted reference optical wavefront into a heterodyne optical signal at the RF frequency, each subaperture of which has a phase that corresponds to the state of phase of a like subaperture of the optical wavefront. An array of lenses focuses the optical heterodyne signal into an array of photodetectors, each responsive to a subaperture and that produces an electrical signal at the optical beat frequency corresponding to the RF and having a phase corresponding to the state of phase of the corresponding subaperture of the optical wavefront. A plurality of circuit chains, each including a digital divider, responds to the RF signal and a corresponding one of the array of electrical signals and with an exclusive OR circuit and an integrating circuit develops a like plurality of output signals that comprise voltages that linearly correspond to the state of optical phase of a subaperture of the optical wavefront. The composite output signals represent the optical state of phase of the incoming optical wavefront.