Refocusing a scanned laser projector for small and bright images: simultaneously controlling the profile of the laser beam and the boundary of the image

This paper describes a projection system for augmenting a scanned laser projector to create very small, very bright images for use in a microsurgical augmented reality system. Normal optical design approaches are insufficient because the laser beam profile differs optically from the aggregate image. We propose a novel arrangement of two lens groups working together to simultaneously adjust both the laser beam of the projector (individual pixels) and the spatial envelope containing them (the entire image) to the desired sizes. The present work models such a system using paraxial beam equations and ideal lenses to demonstrate that there is an “in-focus” range, or depth of field, defined by the intersection of the resulting beam-waist radius curve and the ideal pixel radius for a given image size. Images within this depth of field are in focus and can be adjusted to the desired size by manipulating the lenses.