Abstract: An apparatus and method are disclosed for detecting and signaling when a vehicle enters or poses a serious risk of entering a roadway work zone. The apparatus comprises an intrusion detector array for detecting a vehicle breaching the work zone perimeter, and a high intensity strobe light array for providing an optical warning signal when the perimeter breaching vehicle is detected. The detector array includes one or more transmitters for emitting pulsed infrared signals along the work zone perimeter, and one or more receivers for detecting the presence or absence of the pulsed infrared signals, where the receivers include filters for removing stray signals emanating from sources other than the transmitters. The strobe light array includes a primary strobe activated by the detector array when a perimeter breaching vehicle is detected, and several relay strobes which are activated by the optical warning signal emitted by the primary strobe or another relay strobe.

Abstract: The light receiving or back-side surface (22) of an indium antimonide (InSb) photodetector device (10) substrate (12) is cleaned to remove all native oxides of indium and antimony therefrom. A passivation layer (26) is then formed on the surface (22) of a material such as silicon dioxide, silicon suboxide and/or silicon nitride which does not react with InSb to form a structure which would have carrier traps therein and cause flashing. The device (10) is capable of detecting radiation over a continuous spectral range including the infrared, visible and ultraviolet regions.

Abstract: An assembly for detecting and signalling when an object enters a work zone including a plurality of transmitter-sensor pairs serially connected along a section of the work zone perimeter for detecting when an object passes therethrough. Once an object is detected, an optical warning signal is activated. The optical warning signal includes a primary strobe and a plurality of relay strobes positioned throughout the work zone. The primary strobe flashes at a predetermined flash rate which is detected by a photoelectric sensor in a nearby relay strobe. The nearby relay strobe begins flashing at the predetermined flash rate thereby activating another relay strobe in close proximity. This cascading strobe effect saturates the work zone.