Generalized nonimaging concentrators can be incorporated into conventional optical systems in situations where flux concentration rather than imaging is required. The parameters of the concentrator for maximum flux concentration depend on the design of the particular optical system under consideration. Rationale for determining the concentrator parameters is given for one particular optical system and the procedure used for calculation of these parameters is outlined. The calculations are done for three concentrators applicable to the optical system.
William L. Eichhorn, "Designing generalized conic concentrators for conventional optical systems," Appl. Opt. 24, 1204-1205 (1985)