The global economy is the most complex machine ever created

‘Value of digital information networks: a holonic framework’, PhD-thesis by António Madureira (Faculty Electrical Engineering, Mathematics and Computer)

Insects have a very blurred view of their surroundings, but their compound eyes detect movement and the polarization of light very accurately, allowing them to fly and navigate with very limited intelligence. According to Mukul Sarkar, these advantages make an insect’s visual system very useful for robotics.

Sarkar, who conducted his research in Delft ( EEMCS faculty) and at the Holst Centre, a sensors and electronics research institute in Eindhoven, will defend his Phd thesis, entitled ‘A biologically inspired CMOS image sensor’, on Friday,  February 4.

“Light emanating from reflections is partially polarized,” Sarkar says. “Because insects have their light-sensitive rhodopsin molecules nicely aligned in their faceted eyes, they’re able to detect the polarization. This information for example tells them what type of substrate they’re looking at, since all materials polarize the reflected light differently.”

Insects also use the angle of polarization as a navigation tool –  as a kind of light compass. And they need very little brain processing power to do this. We humans on the other hand, with our polarisation blind eyes, must compare different high resolution images with one another and calculate the changes in x, y and z directions in order to estimate movements, which is much more complicated.

“The same goes for robots that use photodiodes for their vision and navigation,” Sarkar explains. “They need to perform iterative processes with multiple images, which costs lots of energy. If we provide them with CMOS image sensors capable of in-pixel polarization detection and data processing power, we solve that problem.”

By neatly aligning the metal wires in a CMOS sensor – the wires that are used for routing in the chip – Sarkar developed a sensor with grids that only allow light with certain polarisation to penetrate. Each sensor is composed of four pixels. The wires on top of each one of the pixels are laid down in a different direction, making each pixel sensitive to different polarization.
There is still a lot of work to be done to obtain high enough resolution, but Sarkar believes these types of sensors could one day be used in endoscopes: “Cancer tissue reflects light with different polarisation than healthy tissue. A small chirurgical robot could use this information to navigate towards the tumor.”

Editor Redactie

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