Catadioptric null test of ultra-deep concave aspheric lens in wide-field optical system.

To test the ultra-deep conic surface in wide-field optical systems, a catadioptric null test method is researched in this paper. Equations of infinite conjugate null test system are established and solved using optical path length. The numeric results of a self-aligning mirror's shapes are fitted by coefficients and validation is done in optical design software. The rms wavefront error is 0.0019λ (λ=632.8 nm) in the example fitted by five coefficients. Furthermore, by adjusting spherical aberration distributions, an all-spherical finite conjugate null test system is designed, whose rms wavefront error is 0.0309λ. The test methods in this paper have been proven to be adaptive to many other similar ultra-deep surfaces, even with higher orders.