Abstract: A first apertured shutter rotates almost a full revolution in a first direction, and a second apertured rotary shutter rotates almost a full revolution in an opposite direction before the apertures of both blades are present at the optical axis to effect exposure, thereby to reduce dynamic disturbances owing to the reduced blade accelerations required.

Abstract: A solar energy collector of low cost and high thermal efficiency is disclosed having a heat trap produced by zigzagging a thin strip of polyethylene terephthalate between opposite sides of the trap while wrapping the strip about rows of dowels positioned at opposite sides of the frame of the solar collector. A window of soda lime glass filters UV radiation to inhibit discoloration of the plastic heat trap walls. An absorber plate having fluid pipes therein is positioned underneath the heat trap and a first layer of fiberglass, and a second layer of polyurethane foam are positioned below the absorber plate. The fiberglass layer prevents overheating of the polyurethane foam layer to in turn inhibit the formation of toxic fluids, which may condense upon the underside of the window to reduce the efficiency of the collector.