Adaptive Shack-Hartmann wavefront system with extended dynamic range for lens characterization

Abstract

The adaptive Shack-Hartmann wavefront sensor (SHWFS), which integrates deformable mirror (DM) with SHWFS, is effectively used for measuring and characterizing optical elements such as thick lenses, contact lenses, and intraocular lenses (IOLs). The major advantage of combining the DM with SHWFS is the ability of the DM to implement dynamic corrections of any existing wavefront aberrations. However, the measurement dynamic range of the system is limited by the active area of the DM which has a relatively small bandwidth product. This issue can be physically overcome using compound-lens methodology that uses an additional lens or lens system along with the lens under test. The selection criterion of the compound-lens system is based on the focal length of the tested lens, the effective focal length of the tested lens with the compound lens, and the distance between them. Thus, the optimal selection of the compound-lens system and the setup parameters significantly contribute to readjusting the laser beam diameter to properly fit the DM's active area. Hence, the measurement dynamic range could be successfully extended. To prove the concept, the dynamic range of the used adaptive SHWFS system is first determined. Then, a group of lenses beyond the dynamic range of the system was measured using the compound-lens methodology. The experimental results reveal that the proposed compound-lens methodology can effectively extend the dynamic range of the measurements while keeping the root-mean-square error minimal.