Static subaperture stitching interferometry based on dynamic wavefront modulation with a spatial light modulator

Subaperture stitching interferometry (SSI) is an essential technique for testing surface shape errors of complex surfaces. However, the accuracy of full-aperture surface reconstruction is affected by positioning errors caused by mechanical movement. To address this issue, this paper presents a static SSI method based on dynamic wavefront modulation using a spatial light modulator (SLM). The SLM is utilized to compensate for the amount of tilt required for subaperture testing and combined with a standard spherical lens to generate tilted spherical waves. This process is performed via a feedback correction algorithm based on Newton iterations, with the aim of to increasing the quality of the tilted standard spherical wavefront. Full-aperture stitching tests can be realized without moving any system components, fundamentally suppressing the generation of positioning errors. For a high-order aspheric surface, the root mean square (RMS) value of the point-to-point residual wavefront between the test and the result of the computer-generated hologram (CGH) method is 0.01λ. Thus, the proposed method can be applied for the high-precision testing of complex surfaces.