RFID 'Lamps' Map The Physical World

By Roland Piquepaille

By combining RFID tags containing photosensors with portable projectors, researchers from Mitsubishi Electric Research Labs (MERL) are bringing a revolution to inventory control. In "Projector lights radio tags," Technology Research News says that the "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." The RFIG lamps are demonstrated right now at the SIGGRAPH 2004 Conference held in Los Angeles. This system, which also could be used to guide robots or track movement of items in health care settings, should be available at reasonable costs within two or three years.

Here are some of the things we could do with the RFIG lamps.

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.

As an example, this sketch shows how warehouse workers could track inventory (Credit: MERL).

All the illustrations above and below come from this page at MERL, "RFIG Lamps: Interacting with Self-describing World via Photosensing Wireless Tags and Projectors."

Here are some details about how the system works.

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.

The projector then marks the appropriate tags for the user. The projector image is dark where there are no tags, and illuminates areas where there are tags, said Raskar. The tags are accurate to within a millimeter, and can be used to find objects and detect when objects have been moved, said Raskar.

These RFIG lamps offer plenty of new possibilities. For example, a warehouse worker can put annotations on selected objects. The following is pretty interesting.

The projector can also capture an image of an object or sets of objects including tag information, then project the image on another surface. This cut-and-paste capability is useful for interacting with tags that are in places that are not suitable for projections, said Raskar.

	These three photographs show how to use a cut-and-paste using these images captured by the projectors. This one represents a scene that you want to reinspect later (Credit: MERL).
	Here is how the scene is projected on another surface, and 'copied' along with data stored on tags (Credit: MERL).
	Finally, the scene is examined elsewhere by 'pasting' images after removing geometric and photometric distortions (Credit: MERL).

The above link at MERL provides many other photographs and comments. And now, what's next?

The system's radio frequency tags will cost a little more than ordinary radio frequency tags because they contain a photosensor, and it will be two or three years before the passive sensing tags are available at reasonable costs and in quantity, said Raskar.

The researchers' next step is to put together a system that would allow more than one reader to work with a set of tags at a time, said Raskar.

If you are lucky enough to be in Los Angeles, run to SIGGRAPH 2004: it is opened up to tomorrow, August 12. If you can't go, you still can read this page on the conference site, "Interacting With Projections Using iLamp Projectors."

Sources: Kimberly Patch, Technology Research News, August 11/18, 2004; Mitsubishi Electric Research Labs