Method for measuring gradient index distribution of rod lens

摘要

A method of measuring a radial index distribution of a rod lens has the steps: (1) the rod lens is processed so that the length is approximately P/2 (where P is pitch length) or an integer multiple thereof and so end surfaces parallel, (2) a patterned surface is set as an object surface in the proximity of one end surface, and an image surface is formed in the proximity of the other end surface by irradiating the patterned surface with condensed monochromatic light, (3) the positions of paraxial focal points and the curves of curvature of field are obtained by observing the image surface, and (4) higher-order index distribution coefficients are calculated back by a fitting process on the basis of the positions of paraxial focal points and the curves of curvature of field.