Design and tolerance of polychromatic multi-material freeform gradient-index phase corrector plates

Previous studies have demonstrated the potential of multi-material gradient-index (MMGRIN) optical elements in polychromatic imaging applications, yet few have explored the manufacturability of such elements. The ability to control polychromatic aberrations with MMGRIN elements is demonstrated through a design study of polychromatic MMGRIN phase-corrector plates utilizing freeform refractive-index-profile definitions. A single MMGRIN element design corrected for three wavelengths is presented. A Monte Carlo trial-based tolerance method is used to determine the manufacturing precision required for optimum yield. The MMGRIN designs and their tolerance results are then compared with equivalent phase corrector plate designs based on refractive freeform surfaces. The results show that the MMGRIN design has less strict precision requirements than the equivalent refractive freeform surface design.