A pressure actuated light pen attached to the end of an optical fiber bundle has a retractable shutter mechanism at its forward end. The shutter mechanism comprises a plurality of wedge-shaped sections, resiliently urged in a forward direction to at least substantially close off light admittance, and...http://www.google.fr/patents/US4107540?utm_source=gb-gplus-shareBrevet US4107540 - Pressure actuated light pen
