Optical transmission filter for far field beam correction

摘要

The present invention deals with an optical transmission filter for effecting differential phase delay upon light in a beam polarized in a P dimension, as a function of position within the filter aperture for far field correction. The filter employs two lenses of birefrigent material, the crystal optic axes of the respective lens materials being oriented in mutually orthogonal positions and at a 45 DEG angle to the P dimension. The lenses have their adjacent surfaces respectively concave and convex with the same radius of curvature and their non-adjacent surfaces flat. The two lenses may be both spherical or both cylindrical. The correction provides an improvement in beam quality in laser systems operating with larger beam apertures or at higher powers.