Optical system

A light guide comprising:

• (a) a clear block of transparent material having an internal volume, said internal volume being an optical continuum without reflecting surfaces internal thereto;
• (b) a first facet block of transparent material containing a first set of mutually-parallel partially-reflecting internal surfaces, said first facet block bonded to said clear block at a first planar interface;
• and
• (c) a second facet block of transparent material containing a second set of mutually-parallel partially-reflecting internal surfaces, said second facet block bonded to said clear block at a second planar interface, said second planar interface being non-parallel to said first planar interface,
• wherein said clear block, said first facet block and said second facet block together form at least part of a rigid optical assembly bounded by a pair of parallel surfaces for supporting internal reflection within said rigid optical assembly, and wherein said first set of partially-reflecting internal surfaces is parallel to said second set of partially-reflecting internal surfaces, and wherein a straight line between at least one of said first set of partially-reflecting internal surfaces and at least one of said second set of partially-reflecting internal surfaces passes through said clear block.