Analysis of he-ne laser surface reflections from an off-axis parabolic mirror

Surface reflections from an off-axis parabolic mirror are analyzed in three dimensions applying the techniques of vector analysis and ray tracing. A He-Ne laser is directed onto the mirror surface and held fixed while the parabolic mirror is rotated through an angle of 360 degrees on an axis that is parallel to that of the original paraboloid. The reflection from the mirror traces a closed figure in a plane perpendicular to the paraboloidal axis when the mirror undergoes one complete revolution about its center axis. The shape of this figure depends on the value of the off-axis distance and the focal length; consequently, this figure yields information about the parameters specified in the construction of off-axis parabolic mirrors.