Ring laser gyro detector lens system

A ring laser gyroscope detector lens system for mounting on a ring laser gyroscope body having a resonant cavity, said ring laser gyroscope body having CW and CCW counterpropagating light beams propagating in a plane normal to the rate input axis of said ring laser gyroscope, said ring laser gyroscope detector lens system comprising:

• a means for extracting a component of each of said CW and CCW light beams from said cavity and for providing extracted CW and CCW beams;
• a means for combining said extracted CW and CCW beams to form a substantially circular interference light source having a diameter;
• a planar array of detector elements;
• a cylindrical lens for forming a substantially elliptical interference light source pattern on said planar array of detector elements, said cylindrical lens having:
• a single curved surface,
• a cylindrical axis parallel to said curved surface, all points on said curved surface of said cylindrical Tens being located at a radius (R) from said cylindrical axis, and
• a flat surface parallel to said cylindrical axis and normal to said optical axis;
• said curved surface subtending a half angle of curvature equal to or less than 40 degrees;
• said substantially circular interference light source being incident on said curved surface at the primary vertex and coaxial with said optical axis;
• light from said light source passing through said lens and exiting said flat surface to form said elliptical interference light source pattern on said planar array of detector elements;
• said cylindrical lens having a radius of curvature (R), said radius of curvature being set equal to the diameter of said substantially circular interference light source divided by substantially 0.64;
• said flat surface having a width "W", said width being substantially equal to two times the diameter of said substantially circular interference light source;
• said planar array detector elements having a geometric center, said planar array detector elements being positioned to locate said geometric center on said optical axis, said planar array being normal to said optical axis;
• said cylindrical lens being made of fused silica and having a primary principal point located on said optical axis at a point substantially equidistant between the lens primary vertex and said flat surface;
• said planar array detector elements geometric center being positioned on said optical axis subsequent to said cylindrical lens flat surface at a distance from said primary principal point substantially equal to 3.5 times the diameter of said substantially circular interference light source;
• bias and amplification means for conditioning each said detector in said array to be independently responsive to incident light intensity, said amplification means being further characterized to provide:
• a detector output signal for each detector in response to said incident light intensity penetrating a predetermined threshold;
• whereby, the phase relationship between said detector output signals and the repetition rate of said detector output signals characterize the rotational polarity and rotational rate of said ring laser gyroscope body on said input axis.