Retroreflective annular beam prism and flow cytometer apparatus

摘要

A beam of optical radiation from a source 5 is directed onto the apex 2 of the conical portion 3 at the forward end of the prism 1 and in the direction of the central axis of the prism. The beam is reflected by the reflector 4 provided behind the apex so that the beam is refracted by the prism to project from the forward end of the prism as an annular beam 7. Alternatively, the prism may have a pyramid shaped front portion with an even number of inclined faces meeting at the apex so that the beam emerging from the front of the prism is in the form of a multisided tube of parallel beams.