Optical freeform surface generation by modal Zernike method with optimum sampling data type to realize accurate wavefront matching

摘要

Wavefront matching, i.e. phase control of an arbitrary input wavefront (IW) to produce target output wavefront (OW), can be realized using an optical freeform surface (OFS). The accuracy of wavefront matching is dependent on the discrete sampling data of OFS, categorized as feature point coordinates and surface slopes, especially for surface generation with modal Zernike method. To find out the optimum sampling data type, first we propose an exact ray mapping process ruled by Snell' law and the constancy of optical path length from IW to OW to derive the feature point coordinates and surface slopes of OFS simultaneously. Then, wavefront error is numerically calculated by ray tracing for OFS generated from different sampling data types to demonstrate the effectiveness and accuracy of wavefront matching. We find that OFS generation method based on feature point coordinates has superior performance in wavefront matching than that based on surface slops under the condition of high density sampling of IW regardless of complexity of IW. Additionally, in the case of complex IW, the accuracy of wavefront matching benefits from heavy weight of low-order aberrations especially defocus and astigmatism in IW.