In-the-Spectacle-Lens Telescopic Device for Low Vision

implements a magnifying element similar to that used in the in-the-lens electronic displaydeveloped by MicroOptical Engineering Corp 39 . Light entering the carrier lens at the objectivewindow on the left (Fig. 10) is reflected by the first beam splitter towards the concave mirror tothe left (the objective). Following reflection and convergence at the concave mirror the lightpasses to the right through the beam splitter traveling through the carrier lens, forming anintermediate image plane, and proceeding through the second beam splitter. It reflects off thesecond spherical concave mirror (the ocular), and is then reflected by the second beam splitterinto the wearer’s eye. This arrangement provides a Keplerian (astronomical, reversing) telescopewith significant light loss due to the 4 passes through the beam splitters. Four such passes willresult in loss of 15/16 (94%) of the entering light.Quarter-wavePlate (λ/4)PolarizingbeamQuarter-wavePlate (λ/4)tPlano Convex lensBack side mirroredCarrier lensOccluderPlano Convex lensBack side mirroredFigure 10: A schematic of a Keplerian (astronomical- reversing) in-the-lens telescopeusing spherical mirrors, polarizing beam splitters and quarter wave plates.The light loss can be substantially recovered using polarizing beam splitters and quarterwave plates (Fig. 10). The first polarizing beam splitter that reflects only the S-componentresults in a 50% loss of light. Following reflection in the objective curved mirror and passingtwice through the quarter wave plate the reflected light will be polarized appropriately to passalmost unaffected through the polarizing beam splitter. Assuming there is no change in thepolarization state of the light as it travels through the carrier lens, it will pass through the second17