Patent attributes
An optical device comprises two flat plates each having a reflective flat surface, and two flat spacer plates of thickness H each having a reflective sidewall. The flat plates and flat spacer plates are arranged as a stack with the reflective flat surfaces facing each other and the flat spacer plates arranged in a single plane and disposed between the two flat plates with the reflective sidewalls facing each other and with a gap between the two reflective sidewalls. The facing reflective flat surfaces and facing reflective sidewalls define a light tunnel passage with dimension H in the direction transverse to the single plane. The facing reflective sidewalls may be mutually parallel and spaced by a constant gap W to provide a light tunnel passage with constant cross-section H×W, or may be oriented at an angle to provide a tapered light tunnel passage.
