An existing solution for remote, non-contact object identification is Radio Frequency Identification (RFID), which uses radio frequency radiation and a tag on the object to be identified with a reader. Active RFID tags require a source of electrical power to generate the signal to be transmitted to the reader, so the system is not passive. Passive RFID uses a passive identification tag, but the range of this technique can be limiting. Another set of techniques for remote object identification use reflectors that are illuminated by a light source and that actively modulate the amount of light reflected back to the light source. One drawback is that electrical power to the reflectors is required. Another drawback is that the technique relies on active modulation of the light and therefore any light variation due to disturbances of the index of refraction of the intervening medium can mask the desired signal.
USPTO Backgrounds
USPTO Backgrounds