THE VIBRATING eyes of jumping spiders have inspired a new breed of vision
sensors that could give the next generation of Mars rovers sharper eyesight, say
researchers in California. As a result, the roving robots will need less
computing power, so they鈥檒l be much lighter and will use less electricity.
Today鈥檚 robot-vision systems sense images focused onto an array of picture
elements on a microchip. Each picture element, or pixel, is generated by a
photoreceptor that converts light intensity into an electrical signal. The
sensors generate huge quantities of data many times per second鈥攕o they
need complex computer circuitry to process the information. But this adds
weight.
To cut down on the processing power required, Oliver Landolt, Ania Mitros and
their colleagues at the California Institute of Technology in Pasadena are
turning to nature for help. Biologists have long known that the tropical jumping
spider, which vibrates its thin, long retina back and forth to see more clearly
than would otherwise be possible.
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Landolt and his colleagues wondered whether vibrating an electronic image
sensor could also create sharper images. So they built an array comprising 32
rows of 32 pixels each on a silicon image-sensor chip and clamped a metal frame
onto it. Next, they mounted a lens inside the frame, attached by four springs.
The lens focuses an image onto the chip. When the unit is shaken, the lens
starts vibrating at the springs鈥� resonant frequency鈥攁bout 300
hertz鈥攎oving the image over the pixels.
The distance from the lens to the surface of the chip never changes, so the
image is always in focus. The net effect is as if each pixel is moving
elliptically, sampling a larger area of the image than if it were stationary.
Each pixel generates a train of digital pulses from which a signal processor
extracts features of the image鈥攗sing knowledge of the position of the
springs.
To see why moving pixels are better than stationary ones, consider the line
that signals a transition from light to darkness
(see Diagram, bottom right).
Immobile pixels can only tell that the transition is somewhere in between them.
But if the pixels are moving, they cover the region between them, and will
detect precisely where the change in light intensity occurs.
Although smaller than a matchbox, the vibrating sensor鈥檚 images are almost as
sharp as those of an immobile sensor with 256 by 256 pixels, says Landolt. 鈥淭his
is a good start to doing interesting things with a robot, such as finding where
a door is, or identifying the orientation of edges between light and
诲补谤办苍别蝉蝉.鈥�
Christopher Assad, who works on biologically inspired planetary robots at
NASA鈥檚 Jet Propulsion Laboratory in Pasadena, agrees. 鈥淭his would be great,鈥� he
says. 鈥淭he really elegant part that I like is that if you mount this on a small
rover, the rover鈥檚 going to have vibrations just from its movements and you can
use that wasted energy to power the sensor鈥檚 movements. It鈥檚 a very elegant way
to win big on power and allow you to do smart imaging.鈥�
Landolt鈥檚 team, whose research was funded by DARPA, the Pentagon鈥檚 research
outfit, revealed its vibrating camera at last week鈥檚 Advanced Research in Very
Large Scale Integration conference in Salt Lake City, Utah.