Phase conjugate adaptive optics using perimeter phase measurement

We describe a concept for a phase conjugate adaptive optics system which avoids the use of a shared aperture and the attendant difficulties when such a system is used with a high-power laser. The concept consists of measuring the phase of a reference wave around the edge of the aperture and interpolating with a suitable formula to find the phase inside the aperture. We assess the potential of this technique to compensate for atmospheric turbulence when the transmitting aperture is circular or annular. Good correction is indicated, particularly for the case of an annular aperture where perimeter phase measurements can give an estimate of the amount of turbulence-induced misfocus.