Patent ID: 7402785

Claim:
An adaptive optical system to compensate for the effects of turbulence in a beam, comprising: a steering mirror movable about one or more tilt axes; a phase correction device positioned to receive an incoming beam after relay by the steering mirror, wherein the beam has a cross-section that includes multiple subapertures, the phase correction device includes a plurality of phase correction elements, each of the phase correction elements corresponds to a different one of the subapertures, and each of the phase correction elements is positioned to induce phase corrections in its corresponding subaperture; a wavefront sensor (WFS) positioned to receive the incoming beam after correction by the phase correction device, the WFS including a plurality of WFS output channels, each of the WFS output channels corresponding to a different one of the subapertures; and at least one controller configured to perform steps that include (a) receiving data on the WFS output channels, and (b) calculating, for each of the subapertures and based on the data received in step (a), a phase correction to be induced by the phase correction element corresponding to that subaperture, and wherein each of the WFS output channels corresponds to a single one of the phase correction elements, steps (a) and (b) are performed during a current frame period, and the at least one controller is configured to perform step (b) by performing steps that include subtracting a piston, wherein the piston is calculated based on data received on the WFS output channels during a frame period prior to the current frame period and without use of data received on the WFS output channels during the current frame period.