Afocal optical concentrator

Abstract

A Mersenne reflector system provides solar daylighting uses parabolic troughs as primary and secondary reflectors, in Cassegrainian and Gregorian configurations. A Mersenne-like reflector system uses truncated parabolic troughs as primary and secondary reflectors in the Cassegrainian configuration. A variety of combinations of reflector shapes are used including: elliptical primary and circular secondary, rectangular primary and square secondary, elliptical primary and square secondary, and rectangular primary and circular secondary.

What is claimed is: 
     
         1 . An optical concentrator, comprising
 a primary reflector formed as a concave first surface with a first longitudinal axis and a first focal line, the primary reflector defining a first modified conic section along the first longitudinal axis and defining a hole therein configured to allow light to pass through the hole, the first focal line being perpendicular to the first longitudinal axis; and   a secondary reflector formed as a second surface with a second longitudinal axis and a second focal line, the secondary reflector defining a second modified conic section along the second longitudinal axis; wherein   the first focal line of the primary reflector is substantially coincident with the second focal line of the secondary reflector;   the first modified conic section has a form of a corresponding first true conic section modified by truncation of an intermediate portion of the primary reflector along the first longitudinal axis by a truncation amount; and   the second modified conic section has a form of a corresponding second true conic section modified by truncation of an intermediate portion of the secondary reflector along the first longitudinal axis by the truncation amount.   
     
     
         2 . The optical concentrator as set forth in  claim 1 , wherein the truncation amount is substantially equal to a size of an occluded area of light flux on the primary reflector due to shadowing by the secondary reflector. 
     
     
         3 . The optical concentrator as set forth in  claim 1 , wherein the total flux incident on the first surface area of a primary reflector is reflected toward the secondary reflector. 
     
     
         4 . The optical concentrator as set forth in  claim 1 , wherein the truncation amount is determined by a shape of the secondary reflector. 
     
     
         5 . The optical concentrator as set forth in  claim 4 , wherein the truncation amount is determined by a width of a shadow cast on the primary reflector by the secondary reflector. 
     
     
         6 . The optical concentrator as set forth in  claim 5 , wherein the width of the shadow is dependent on a width of the secondary projector, which is a dimension orthogonal to the second longitudinal axis. 
     
     
         7 . The optical concentrator as set forth in  claim 5 , wherein
 each of the primary and secondary reflectors has a plane of symmetry transverse to the longitudinal axes; and   the truncation amount corresponds to one half of the width of the shadow, which is removed from the intermediate portions of each of the primary and secondary reflectors on each side of the plane of symmetry.   
     
     
         8 . The optical concentrator as set forth in  claim 1 , wherein the first modified conic section defining the first surface of the primary reflector and the second modified conic section defining the second surface of the secondary reflector are a same type of conic section. 
     
     
         9 . The optical concentrator as set forth in  claim 1 , wherein the first modified conic section defining the first surface of the primary reflector and second modified conic section defining the second surface of the secondary reflector are different conic section types. 
     
     
         10 . The optical concentrator as set forth in  claim 1 , wherein the first longitudinal axis is parallel to the second longitudinal axis. 
     
     
         11 . The optical concentrator as set forth in  claim 1 , wherein the hole is located midway or is centered along the first longitudinal axis. 
     
     
         12 . The optical concentrator as set forth in  claim 1 , wherein the primary reflector has a substantially elliptical perimeter and is formed by truncating the primary reflector at a midpoint along the first longitudinal axis. 
     
     
         13 . The optical concentrator as set forth in  claim 15 , wherein the secondary reflector has a rectangular perimeter and is formed by truncating the secondary reflector at a midpoint along the second longitudinal axis. 
     
     
         14 . The optical concentrator of  claim 1 , wherein the truncation amount is a first truncation amount associated with the primary reflector and a second truncation amount associated with the secondary reflector. 
     
     
         15 . The optical concentrator of  claim 1 , wherein
 the primary reflector has a first reflector half and second reflector half and a first plane of symmetry therebetween;   the secondary reflector has a third reflector half and fourth reflector half and a second plane of symmetry therebetween;   the first and second planes of symmetry are substantially aligned along an optical axis of the optical concentrator; and   the first, second, third, and fourth reflector halves are each disposed closer to the first and second planes of symmetry, respectively, by a distance equal to half the truncation amount.   
     
     
         16 . The optical concentrator or  claim 1 , wherein a concentration of light exiting the hole is at least three times a concentration of light incident on the primary reflector. 
     
     
         17 . The optical concentrator or  claim 1 , wherein a concentration of light exiting the hole is at least seven times a concentration of light incident on the primary reflector. 
     
     
         18 . The optical concentrator or  claim 1 , wherein a concentration of light exiting the hole is at greater than or equal to 10 times a concentration of light incident on the primary reflector. 
     
     
         19 . The optical concentrator as set forth in  claim 1 , wherein the optical concentrator is an afocal optical concentrator. 
     
     
         20 . The optical concentrator as set forth in  claim 1 , wherein the first longitudinal axis of the primary reflector is at least twice as long as a width of the primary reflector.