Thermodynamically optimal infrared collector with directional reduction of concentration

A collector for receiving infrared communications signals, comprising:

• a concentrator for receiving and concentrating signals including infrared communications signals, the concentrator being made of a dielectric material which transmits infrared radiation and having a convex surface of a non-zero curvature which is substantially transparent to infrared radiation;
• and
• infrared radiation detection means for receiving the concentrated infrared communications signals from the concentrator, the convex surface being such that any line which connects any part of the infrared radiation detection means to the surface intersects the surface at an angle less than the critical angle for the dielectric material and the convex surface including a more-curved portion and a less-curved portion, the less-curved portion having a non-zero curvature which is less than a non-zero curvature of the more-curved portion of the convex surface, whereby the concentrator concentrates infrared radiation which strikes the more-curved portion at a direction normal to the more-curved portion at a level of approximately N.sup.2, where N is the index of refraction of the dielectric material, and concentrates radiation which strikes the less-curved portion from a direction normal to the less-curved portion at a level less than N.sup.2.