'Autoclipse' optional non-dazzling acetylene motor car headlamp, 1911.
© Science Museum / Science & Society Picture Library
This is an example of the motor car headlamp and anti-dazzling device patented by H G M and M A Besnard in 1905-1906. Using an arrangement of a hyperbolic reflector and a plano-convex lens, the acetylene lamp provides a central parallel beam for illuminating distant objects, and also a divergent beam for nearer objects. The central, dazzling beam can be cut out, or eclipsed, when required by a circular disc or shutter which, when operated from the dashboard by a Bowden cable, is brought into a position which stops light falling onto the reflector.