a method and apparatus involve collection of radiation with a radiation collector that allows entry of external radiation . the exterior of the collector has mutually exclusive first , second , third and fourth surface portions oriented so that they each effect total reflection of the majority of radiation within a waveband that impinges thereon while propagating within the collector . the first and second surface portions are spaced and approximately parallel . the third and fourth surface portions extend at a first angle with respect to each other , and respectively extend at second and third angles with respect to end portions of the first and second surface portions .