Discover the first quantum image sensor

Article by: Brian Santo

It seems possible to build a quantum image sensor (QIS) that could detect every incoming photon to create the most precise imaging ever.

A company that may be relatively unknown to most outside the imaging field recently announced its first products. The Gigajot team invented and developed quantum image sensors (QIS) long before the company was founded in 2017. The acronym QIS will sound a bit like the much more familiar IEC or CMOS image sensor. It’s the evolution (or maybe a revolution) of CMOS image sensors, a truly ubiquitous technology.

Gigajot was co-founded by researchers Saleh Masoodian and Jiaju Ma as a spin-off from the Thayer School of Engineering at Dartmouth College in New Hampshire.

QIS Camera Development Kit (source: Gigajot)

Massoodian and Ma were PhD students mentored by another company director who is known to even the most casual imaging tech enthusiasts and non-techies. Eric R. Fossum recently received an Emmy for his work developing image sensors and appears on the firm’s list of advisors with Ron Adner.

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First silicon

The prehistory of the first Gigajot products probably dates back to Fossum’s slide deck describing the history of active pixel image sensor history from 2008. His slides cover imaging technology in the 1960s that preceded the charge-coupled device (CCD) – what was once the workhorse of solid-state imaging. Fossum’s timeline has covered all the major milestones that bring us to the point of dense, high-megapixel count sensors. Fast forward to 2008, and today’s image sensors have changed little except for size and pixel count.

In that talk, Fossum noted the power of marketing when it comes to technology with the point “If you can’t fix it, introduce it.” For the future of imaging technology, he postulated that the next generation of imaging requires a market-driven paradigm shift.

He signed his closing slide with “Jot-based sensors can be interesting.” And here we are.

In this 2008 presentation, Fossum indicated its profound awareness of the importance not only of the market, but also of marketing in the success of a new technology. Using iota describe a new type of imaging product protected the territory of a very small detector element, leaving little room for competitors.

Slide from Eric Fossum’s lecture “Inventing the CMOS Camera and the Quanta Image Sensor” given at the University College of Cork (Source: ER Fossum) (Click on the image to enlarge it.)

This is akin to Google’s origin of googol, a huge number another brand not easy to beat. With fewer letters and correct spelling, the note-based imager deserves the praise. Only time will tell if the term enters the vernacular in a way that parallels our current overuse of the term. Google.

The link with NASA

The path to the CMOS image sensor that everyone has with a cell phone today began at NASA’s Jet Propulsion Laboratory (JPL) at the California Institute of Technology. They weren’t the only growing group, and the imagery community that grew alongside friendly competition surely played a big role.

But a significant part of the development of CIS came from JPL. The motivation was lighter, more power-efficient solid-state cameras for spacecraft.

The original dream of a lightweight space camera ends up fitting into a cellphone as well (photo credit: Amy Etra/BusinessWeek)

From JPL, Photobit was spawned for commercial development. Some of the first CIS products were webcams. And where would we be in 2021 without our telecommuting webcams?

Photobit was acquired by Micron which became Aptina which was later absorbed into the imaging division of ON Semiconductor.

Back to the future

Several well-researched technologists later, and we have a return to the roots of scientific imaging as Gigajot products are aimed at “high performance imaging applications such as scientific, medical, defense, industrial and space”. The story goes back to its origins. And so is the company, because Gigajot is now located in Pasadena, a short drive from JPL.

Traditionalists and photography perfectionists alike will appreciate the concept of the jot imaging concept. The goal was to create a truly digital film.

As Fossum noted in a 2018 DP Review interview, “Because it is binary in nature, its response is comparable to that of old photographic film.”

Although credited as the inventor of the active pixel sensor technology that forms the basis of most current detectors, Eric Fossum is always careful to acknowledge others for achieving the current state of the art. digital imagery: “The current situation is the result of the contribution of thousands of engineers from different companies who have contributed to our current situation.”

Living in a world where it pays to be aware of near-constant surveillance by image sensors, it might be hard to imagine that even more caution might be needed in the future. But as DP Review summarized the work of the Gigajot team, reading noise reduction to the point of reliably counting individual photons opened “the possibility of cameras that could perfectly describe the light in the scene, even in the almost total darkness.

As we move into an era of even more sophisticated imaging, it’s comforting to know that the brains behind the technology are causing concern. Fossum highlighted the unintended consequences of advanced imaging. At the latest ISSCC, another solid state imaging icon, Albert Theuwissen, took advantage of his plenary address to promote these concerns through the concept of “responsible innovation”, a strong point of this conference.

The Gigajot team will present at next month’s VLSI Symposium. For a detailed overview of the technology base, see the article published in 2017 depicting a back-illuminated sensor array stacked with a readout chip and using a pump gate pad. There is also a next Electron Device Letters article for June.

The VLSI Symposium paper will expand on previous developments: “A Stacked BSI Quanta Photon-Counting Image Sensor with 0.3e Readout Noise and 100dB Single Exposure Dynamic Range”.

Technical documents add credibility and weight to product announcements. Deep, cutting-edge technology coupled with savvy marketing is a rare combination. And probably a winner.

This article was originally published on EE time.

Michael C. Garrison