DISCRETE PHASE CONJUGATE TECHNIQUE FOR PRECOMPENSATION OF LASER BEAMS TRANSMITTED THROUGH TURBULENCE

A process and apparatus are disclosed for aligning a laser beam from a laser transmitter with an incoming laser beam, and driving any sensed tilt differences on an aperture and subaperture basis to zero. The apparatus uses a shared aperture component to sample the outgoing laser beam and the incoming target beam, a retroreflector array to reverse the direction of the subaperture samples of the outgoing beam, a common-mode wavefront sensor to measure subaperture tilt differences between the reversed samples of the laser and the incoming target beam, and a deformable mirror to drive any sensed tilt differences to zero. A transparent beamsplitter is used as the shared aperture component and an AC shearing interferometer is used as the basis for the common-mode sensing. By forcing the outgoing beam to be then conjugate of the incoming beam it is automatically precompensated for any aberrations in the transmission path.