Light collectors in cylindrical geometry

A device for concentrating energy from a source of radiant energy of finite dimension defined by first and second opposing edge points, comprising:

• an energy transducer, a portion of whose cross section is bounded by a first reference axis with said portion and said first reference axis coplanar with a line coupling the edge points, the perimeter of said portion being convex and being limited to the same side of said first reference axis as the source, said portion having a second reference axis extending therethrough perpendicular to said first reference axis, the perimeter of said portion extending from a first tangent point along said first reference axis to a second tangent point along said first reference axis such that a first line from the first edge point to said first tangent point intersects said second reference axis and is tangent to the perimeter of said portion at said first tangent point and such that a second line from the second edge point to said second tangent point intersects said second reference axis and is tangent to the perimeter of said portion at said second tangent point, and a first side wall for directing radiant energy being positioned on the same side of said second reference axis as said first tangent point and being of such contour that any ray of radiant energy from the first edge point intersecting said second reference axis and incident on said first wall is directed along a line tangent to said portion, said first side wall extending from said first line to no further than a intersection with said second line.