Numerical evaluation of a plastic lens by coupling injection molding analysis with optical simulation

The present study covers an integrated simulation scheme for injection-molded plastic lenses by coupling a ray tracing simulation with a finite element (FE) analysis of injection molding. Traditional ray tracing was based on the assumption that the optical properties of a lens were homogeneous throughout the entire volume. This assumption is to a certain extent unrealistic for injection-molded plastic lenses because material properties vary at every point due to the injection molding effects. To take into account the effects of the inhomogeneous optical properties of the molded lens, a modified ray tracing scheme is proposed in conjunction with an FE analysis of the injection molding. Through the injection molding analysis, the distribution of the refractive indices of the lens can be obtained on every mesh point. This information is then used to calculate the ray paths based on the FE mesh of which nodal points have unique index values. The proposed tracing scheme is implemented on the tracing of an aspheric lens for a photo pick-up device, and its validity is ascertained through experimental verifications.