Researchers at a US university have developed a chip modelled on the human eye which combines image sensing with filtering and the ability to track images. The technology could in the future lead to a new type of monitoring device which can interpret and react to movement and may eventually even be used by heart surgeons.

The work being carried out at John Hopkins University under the direction of Ralph Etienne-Cummings, assistant professor of electrical and computer engineering, has produced an integrated low-power chip which mimics the work of the high-definition central region of the retina and the lower-resolution peripheral vision area that follows movement.

The circuit is based on combination analogue-digital CMOS technology and is said to be much faster than distributed component setups which use multiple chips. Those systems typically use an image sensor, a micro-controller and non-volatile RAM.

Etienne-Cummings used the parasitic bipolar transistors that are innate to CMOS chips and created surface arrays of photo-sensitive pixels. The analogue interconnecting matrix for the transistors employs motion detection in the central area and derives speed calculations from it. The analogue inter-connection matrix in the periphery calculates the location of an object by bumping against the edge of the central area and figures a heading calculation from it.

The speed and heading calculations are combined to lock on to, and track, objects in motion. The chip itself executes all operations without the necessity of a separate computer to guide it. 'The idea of putting electronic sensing and processing in the same place is called computational sensing,' said Etienne-Cummings. 'It was coined less than ten years ago by the people who started this new line of research. Our goal is to revolutionise robotic vision, or robotics in general. It hasn't happened yet, but we're making progress.'

Etienne-Cummings points out that the significant thing is how the chip operates, not what it does. 'It's the way it functions. It's a regular CMOS (integrated circuit) chip that can execute all its operations directly without the help of a computer, which results in a very low energy requirement, small size and high speed.'

One of the first applications mentioned for this technology is in security surveillance cameras. The chip could be embedded in cameras, which would allow them to control their own mechanised pan and tilt functions. Cameras could then track intruders.

Factory environments are another area for the technology. 'It could also be used in manufacturing to enable a robot to grab moving parts,' said Etienne-Cummings. 'The chip could be used for anything which we take for granted that uses some motor action - reaching, grabbing, following, tracking - which would require first measuring some kind of visual calculation and picking something out of the background.' Using the chip for electronic toys is another use touted for the technology within a few years.

In the longer term, Etienne-Cummings hopes the technology will be enhanced for use in computer-aided surgery. 'I hope to someday have helped create a technology that will enable doctors to track movement of a beating heart so that blocked cardiac arteries can be cleared without having to stop the heart first, as doctors must do today,' he said.

The technology still has a way to go before it meets those lofty goals. At present, its capabilities are being demonstrated by mounting two eye chips on a toy car, enabling it to follow a line around a test track. The chips force the car to follow a line detected by the sensors, unless an obstacle appears in its path.

To the chips, avoiding a crash takes priority over following the line, so they steer the car away from the obstacle. The system also 'remembers' how it avoided the obstacle so it can steer the car back to the line, to resume its original course.

It 's no surprise, therefore, that Etienne-Cummings says the chips are well suited for all kinds of new mobile applications in micro-robots, autonomous flying machines and extra-terrestrial rovers.