Near-null interferometric test of aspheric cylinders utilizing a partial null lens

Aspheric cylinders are more advantageous than cylinder with spherical cross section in optical design and aberration correction of high-energy laser systems because additional shape parameters can be introduced. To overcome the limited test accuracy and the insufficient research on the testability of the flexible null test method for aspheric cylinders, a near-null interferometric test method for aspheric cylinders was developed utilizing a partial null lens. A coaxial configuration design was employed. Accordingly, only one translation motion was required for testing various aspheric cylinders in one shot. Using the proposed test configuration and the developed near-null data processing method, test accuracy about λ/20 (λ = 632.8 nm) root-mean-square are easier to guarantee compared with those of the existing stitching-required method with off-axis configuration. Further, the testability of the proposed method was analyzed following the development of the partial null theory. The analysis shows the testable surfaces are equidistant surfaces with nearly constant k·R products (k·R = 211.625 mm). The testability results can serve as a good reference for engineers who intend to use aspheric cylinders in high-energy laser systems and can further promote the development of high-energy laser systems. A near-null test system was established. Its simple configuration, moderate test accuracy, and flexible test capacity were successfully demonstrated based on aspheric cylinders measurements.