Simulation and measurement of optical aberrations of injection molded progressive addition lenses

Injection molding is an important mass-production tool in the optical industry. In this research our aim is to develop a process of combining ultraprecision diamond turning and injection molding to create a unique low-cost manufacturing process for progressive addition lenses (PALs). In industry, it is a well-known fact that refractive index variation and geometric deformation of injection molded lenses due to the rheological properties of polymers will distort their optical performance. To address this problem, we developed a method for determining the optical aberrations of the injection molded PALs. This method involves reconstructing the wavefront pattern in the presence of uneven refractive index distribution and surface warpage using a finite element method. In addition to numerical modeling, a measurement system based on a Shack-Hartmann wavefront sensor was used to verify the modeling results. The measured spherocylindrical powers and aberrations of the PALs were in good agreement with the model. Consequently, the optical aberrations of injection molded PALs were successfully predicted by finite element modeling. In summary, it was demonstrated in this study that numerically based optimization for PAL manufacturing is feasible.