Conventional refractive lenses often employ adjustable irises to stop down the lens aperture to increase the depth of field or reduce the amount of light collected by the imaging system. Although a highly obscured concentric multi-reflection (CMR) lens cannot be stopped down in the same way, a similar effect can be achieved with an off-axis aperture mask.
With our CMR designs, a convenient off-axis aperture mask is achieved by sectioning an asymmetrical section of the aperture. This reduction of aperture can significantly increase the depth of field of a CMR lens with a trade-off in sensitivity due to the reduced aperture area. The arc-sectioned aperture also provides a convenient method of further reducing the volume of the lens since a significant portion of the lens volume can be removed.
By arc-sectioning a CMR lens design in this way, we can make an ultra-compact, large magnification, large depth of field camera for a variety of applications including compact portable device cameras. Our first demonstration prototype- an arc-sectioned eight-reflection camera, is shown below.
(Below) Arc-Sectioned eight-reflection lens
(Below) Prototype packaging and assembly
(Below) Performance comparisons
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