Projector lights radio tags
By Kimberly Patch,
Technology Research News
puts you in a computer-generated world. Augmented reality allows for a mix
of virtual reality and the real world by placing computer-generated objects
in a real-world setting.
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
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,
If an object has several radio tags attached to different surfaces,
the system can be used to track the object's orientation and shape, for
example detecting when an object has shifted or been deformed, said Raskar.
The projector, which the researchers developed previously, includes
inertial sensors that track its position, making it possible to project
images from a moving projector and compensate for the movements. The projector
can also hold one portion of a projection steady while allowing another
portion to move, making it possible to project a steady shot of a computer
screen and at the same time project a mouse pointer that the user can control
by moving the entire projector.
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.
The radio frequency identity and geometry system solves three interface
problems, said Raskar: it locates tags precisely and can give visual feedback,
it allows the user to see a subset of tags among many tags, and it allows
the user to differentiate among multiple tags responding to a radio-frequency
A warehouse worker, for instance, could use the system to view the
tag information on a set of objects and digitally mark the tags of selected
objects with instructions for coworkers, said Raskar. Or a librarian could
use the system to identify which books are upside-down or out of order,
The system is the reverse of the more common idea of putting beacons
like light-emitting diodes on the objects themselves so they can be located
visually, said Raskar. "We turned this around and said 'what if the tiny
indiscernible tag does not have a battery attached to it... can it still
be located and visually indicated?'"
The system can also be thought of as the reverse of computer vision,
said Raskar. Traditional computer vision uses a centralized, dense, two-dimensional
array of pixels to record information about a visual field, and the cameras
recording the field are outside the field looking in. The researchers' tags,
in contrast, are essentially single-pixel cameras pasted on objects, and
these cameras are looking out, toward the projector.
Because radio frequency identification tags can be tiny and require
no power source, they could be embedded in packaging to make automated tracking
of even inexpensive objects cost-effective.
Most of the researchers' prototype work was done with active, battery-powered
radio frequency ID tags because these can be programmed, but the system
can be adapted for passive ones as well, said Raskar. In addition, the photosensors
could be used to help power passive tags, he said.
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.
Initially the tags will be useful in inventory management, said
Raskar. The system is really geared towards the first 10 meters and the
last 10 meters of the tag's productive life -- initiation of tags at the
time of production, and locating objects in a warehouse or human-interaction
in cluttered environments, he said.
Within a decade most objects that are bar-coded today will instead
carry radio frequency tags, he said. "Adding a geometric notion will be
appealing for several applications," including factory automation, health
care, entertainment, and even surveillance, 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.
Raskar's research colleagues were Paul Beardsley, Jeroen van Baar,
Yao Wang, Paul Deitz, Johnny Lee, Darren Leigh and Thomas Willwacher. The
researchers are scheduled to present the work at the Association of Computing
Machinery (ACM) Siggraph 2004 conference in Los Angeles on August 8 to 12.
The research was funded by Mitsubishi Electric Research Labs.
Timeline: 2-3 years, 10 years
TRN Categories: Applied Technology; Human-Computer Interaction
Story Type: News
Related Elements: Technical paper, "RFID Lamps: Interacting
with a Self-Describing World via Photosensing Wireless Tags and Projectors,"
Association of Computing Machinery (ACM) Siggraph 2004 conference, Los Angeles,
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