Patent ID: 6094210
Filing Date: 2000-07-25
Classification: G02B

Abstract:
A focusing apparatus for maintaining a first beam in focus at an imaging plane comprising:a first reflective surface which redirects said first beam from a first direction to a second direction wherein said second direction is oriented approximately 90.degree. from said first direction;a second reflective surface which redirects said first beam from said second direction to a third direction wherein said third direction is oriented approximately 90.degree. from said second direction;a third reflective surface which redirects said first beam from said third direction to a fourth direction wherein said fourth direction is oriented approximately 90.degree. from said third direction;a fourth reflective surface which redirects said first beam from said fourth direction to a fifth direction wherein said fifth direction is oriented approximately 90.degree. from said fourth direction;wherein said second reflective surface and said third reflective surface are movable linearly as a unit, with respect to said first reflective surface and said fourth reflective surface;wherein said first direction, said second direction, said third direction, and said fourth direction are located in approximately the same plane;wherein said first reflective surface is located at a plane formed by a face of a first prism and a face of a fourth prism; andwherein said first reflective surface is partially transmissive to a second beam, and said second beam is colinear with said first beam.