Abstract: A high contrast remotely switchable target discriminator, particularly suitable for use with automatic guided vehicles (AGVs), is disclosed. A laser light source directs light through a first polarizer to reflect off a beam splitter toward a target, which may be an AGV guidepath. The target comprises a reflecting material overlaid with a polarization rotator so that the light then reflected from the target has a polarization different from that from the original light source. The reflected light transmits back through the beam splitter to a second polarizer that transmits only light of the rotated polarization. Light that passes through the second polarizer then strikes a detector. A second polarizer-detector combination may be set to transmit and detect only light of the non-rotated polarization so that a sufficiently large ratio of the two different polarizations may be tested.

Abstract: An object recognition system for detecting visible light of a predetermined wavelength emitted by a fluorescent material illuminated with modulated ultraviolet light produced by a self-modulated high pressure mercury vapor lamp. The lamp forms part of a resonant LC circuit which produces oscillations in the lamp intensity at a frequency higher than line frequency. The resulting visible light is detected, demodulated, and compared with a predetermined threshold to sense when the fluorescent material is present. Self-modulation of the UV lamp source eliminates external triggering, excitation or switching of the lamp power supply.