External dihedral-angle error measurement based on Differential Wavefront Sensing

High-precision making of cube blocks such as cube test mass, corner cube retroreflectors, and right-angle prisms faces the problem of measuring the dihedral-angle error. A new method based on optical differential wavefront sensing for external measurement of dihedral-angle error is proposed in this paper. Compared to conventional methods such as the Fizeau interferometer and autocollimation, this method has the advantages of compactness and high precision. Moreover, it can measure both arbitrary internal and external dihedral angles. A quasi-monolithic compact interferometer bench for dihedral-angle error measurement is built and tested. The experimental results show that a resolution of ± 0.15 μrad and a nonlinear residual below ± 3 μrad within a dynamic range of ± 100 μrad has been achieved.