Compensating for Astigmatism in a Holographic Optical Element
Original Publication Date: 1988-Jun-01
Included in the Prior Art Database: 2005-Feb-15
When a holographic optical element is used to deflect and focus a Gaussian laser beam, astigmatism is introduced in the focussed beam if the angle of incidence and angle of diffraction differ. The reduction of the effective beam aperture as measured parallel to the plane of incidence can be compensated by slightly altering the angle of incidence of the reconstructing laser beam. The resulting focal length of the optical element measured parallel to the plane of incidence can be made equal to its focal length measured perpendicular to the plane of incidence.