Researchers from Mitsubishi Electric Research Labs have brought dynamic, computer-generated labels into the physical world with a combination of radio frequency identification (RFID) tags and portable projectors.

Their Radio Frequency Identity and Geometry (RFIG) system consists of a hand-held projector that shines dynamic images onto physical objects of the user’s preference, and radio frequency identification tags augmented with photosensors, which identify objects for the projector. Radio frequency identification tags contain tiny, inexpensive chips that are read using radio waves. Photosensors detect light intensity.



The system can be used to find and track inventory, guide robots or precision handling systems on assembly lines, locate small instruments and track movement of items in health care settings, keep track of objects in homes, offices and libraries, and enable games to integrate real and virtual objects, said Ramesh Raskar, a research scientist at Mitsubishi Electric Research Labs.



The radio identification/photosensor tags can be as small as a grain of rice, said Raskar.



To find an object, a user aims a radio frequency reader in the general direction of a collection of tagged objects. Each tag that is in range is activated by the radio frequency signal, prompting its photosensor to take a reading of the existing light. Once this is done, the projector embedded in the reader turns on, and each tag that detects an increase in illumination sends a response indicating that it is in the projector beam and is ready for interaction.



The projector then beams a sequence of about 20 images of horizontal or vertical bars of varying density, which form unique codes indicating horizontal and vertical coordinates. Each tag records the code, then transmits its identity plus the code back to the radio frequency reader. This allows the reader to determine the location of each tag in its range.



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