Abstract
Ring polishing is a primary method to polish large aperture planar optics that is widely used in the fabrication of high-power solid-state laser equipment. The relative motion track with the ring polishing is always rotationally symmetrical and the amount of material removal is related to the radius. The height errors are identical when the points are in the same radius, which can largely reduce the coverage area when the subaperture stitching method is used to measure the figure error of the surface. A new sparse lattice for planar optics polished by ring polishing is introduced. The cumulative error is proven small enough for sparse subaperture stitching by the reference of the simulated data. A planar optical element with 200 mm×200 mm aperture was chosen to test the feasibility of our proposed method. The results indicate that sparse stitching is suitable for measuring a large planar surface polished by ring polishing. The results of two chain lattice are closer to the fully covered lattice than a one chain lattice. However, more measuring time could be saved by the one chain lattice method. So, the usage of different lattices could be adapted for different periods of large aperture planar optical manufacturing.
Highlights
High-power solid-state laser equipment, such as National Ignition Facility (NIF),[1,2,3] laser mégajoule (LMJ),[4,5] requires a great number of large aperture planar optical elements
The influence of the cumulative error can be calculated from the results obtained during simulated sparse subaperture stitching measurement
Planar large aperture optical surfaces manufactured by ring polishing usually have rotational symmetry; they can be tested by incompletely covered subapertures
Summary
High-power solid-state laser equipment, such as National Ignition Facility (NIF),[1,2,3] laser mégajoule (LMJ),[4,5] requires a great number of large aperture planar optical elements. In NIF, more than 7000 planar optical elements with an aperture larger than 400 mm × 400 mm are required.[6] In the optical manufacturing, the surface shape measurement is a significant process to determine the precision of the optical elements.[7,8,9,10] a measuring method with high precision and efficiency is required. The surface shape measuring method of large aperture optical elements includes the Ritchey–Common test, interferometry, and subaperture stitching interferometry. Some subapertures can be omitted from the fully-covered lattice, and some others are arranged as the sparse lattice to fit the rotationally symmetrical surface shape. It would be a time-saving method with a certain level of accuracy. A planar optical element with 200 mm × 200 mm aperture polished by ring polishing is used for confirming the theory
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