Manufacture for ruling concave metal grating with a long focal length

The ruling technique for concave metal grating with long curvature radius (namely long focal length) is studied. In order to rule the concave grating with a long focal length, the diamond carriage with elastic thimble mode is designed and manufactured. It is available not only to rule plane grating, but to concave grating with a long focal length. The mathematic expression between the curvature radius of circular arc cutting edge of ruling tools for grating and the curvature radius of concave grating, the caliber of grating and the size of transverse direction of bit tool are given. The span of curvature radius of circular arc cutting edge is analyzed theoretically. The concave metal grating with 30 m curvature radius for 10.6 μm laser system is manufactured. The testing result shows that the quality of groove is perfect and the diffraction efficiency is more than 95.6 percent.