Quality control of Fresnel lens molds using deflectometry
Fresnel lenses are widely used in CPV applications and can be manufactured in mass replication processes like injection molding, embossing or crosslinking. The quality control of the designed function of refractive replica includes the assessment of surface errors and replication errors. Since deviations of the mold surface from design are transferred to the replica, the direct characterization of mold surfaces enables error detection early in the fabrication chain. We show the application of a developed deflectometry method to Fresnel shaped metallic molds. The method detects slope deviations from ideal surface slopes in sub-mrad resolution. The results can be easily included in ray tracing simulations to predict the potential optical function of a replica which was manufactured by the respective mold.