Field-oriented wavefront sensor for laser guide stars

We propose a modified approach [1, 2] to form a laser guide star (LGS) with a collimated laser beam launched through the full aperture of a telescope. Using a special form of field stop (diaphragm) uniquely positioned for each subapertures, the wavefront sensor sees only a small part of the source corresponding to the area on the sky, which is cut out by the field stop. Each of these spherical waves subtends the area of a separate subaperture at the telescope pupil. Thus, the LGS is formed of a set of spherical waves. Since the linear size of the subaperture is approximately equal to the coherence radius, the measured wavefront can be restored as a smooth phase function. The use of this scheme is investigated.