Smart sensors go lensless for smart cities

This entry was posted on Wednesday, December 7th, 2016.

Gale Morrison of Semiconductor Engineering recently penned an article about the various challenges associated with building smart cities of the future. As Morrison notes, governments around the globe are beginning to tap into a world of connected devices and sensors for reasons ranging from cheaper lighting to less traffic, lower crime and improved air quality.

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“Smart cities encompass all manner of usage models and equipment — parking meters, traffic lights, power and water meters, mobile telephone networks, apps on every resident user’s handheld phone, including cameras and microphones,” she explained. “The engineer’s challenge is integrating all of these devices using common communication links, ubiquitous GPS technology, algorithms that make sense of the data collected and central repositories for relevant data.”

Another issue identified by Morrison is the challenge of maintaining individual privacy in ultra-connected smart cities, a concern that is driving demand for lensless optical sensors such as Rambus’ lensless smart sensor (LSS) technology. Rather than producing images with the kind of visual acuity of a camera, lensless smart sensors generate data and rough images.

“This is a new kind of optic that is extremely flat and easier to use. So instead of generating an image with a photo-sensitive array and a lens, which is what you find in a camera, this replaces the lens with a diffractive grating,” Patrick Gill, principal scientist for Rambus Labs, told Semiconductor Engineering. “You can still see people moving and tell whether they’re sitting, walking, avoiding certain regions and identify a change in the traffic flow or pick up moving car headlights. But it also allows you to replace something that’s analog with a binary diffraction grating. In addition, it’s easy to manufacture—you can do this as large as 2 microns—and it’s a very good detector of motion.”

According to Gill, there can be a wide space between lensless smart sensors, with at least a 140-degree field of view.

“This provides more detail than a motion detector, but also combines an element of privacy so you’re not going to see something end up on YouTube that you don’t want to be made public,” he stated.

One potential deployment for lensless smart sensors, says Gill, is to place the technology on a multi-function chip that measures temperature and humidity – where it’s too expensive to integrate a lens.

“What’s noteworthy is that all camera modules do not survive a solder re-flow,” he added. “The lens would come out as a puddle. But you can make a diffraction grating with a high-temperature polymer. And there are few things that can do this using low power.”

Interested in learning more about smart cities and sensors? The full text of “Smart Cities, Challenging Issues,” by Gale Morrison is available on Semiconductor Engineering here. You can also check out our LSS product page here and our article archive on the subject here.