Identification device

Abstract

An identification device 10 comprises a retroreflector 12 for receiving an incident beam of radiation 14 from a detection unit 15 remote from the device and selectively retroreflecting the incident beam back to the detection unit. The retroflector 12 comprises a substantially spherical graded refractive index lens 16 and a reflective part 18 for reflecting the incident beam of radiation passing through the lens. In a first condition, or mode, of the retroreflector, the lens 16 and the reflective part 18 are located relative to each other so that the incident beam of radiation 14 is retroreflected back to the detection unit. In a second condition, or mode, of the retroreflector 12, the lens 16 and the reflective part 18 are located relative to each other so that the reflected beam of radiation 22 is directed away from the detection unit.

Dependencies are inferred from the claim text.