CMOS camera sensor inventor returns with an extreme-low-light follow-up

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The same engineer that created the CMOS sensor (above) is developing a low light quanta image sensor. Muhammad Amal Farial Khalid / 123RF

The engineer that developed the CMOS sensor now found in a majority of cameras and smartphones may have just discovered the next generation of camera sensors. Eric R. Fossum and the Dartmouth College Thayer School of Engineering published research in the December 20 issue of Optica detailing the Quanta Image Sensor (QIS), a digital camera sensor capable of capturing images even in the smallest amount of light possible.

What makes the QIS unique is that the sensor only needs a single photon of light to capture an image, which opens up possibilities for extreme low-light photography in a number of fields, including both artistic and scientific applications. Earlier attempts to design a sensor capable of performing in such low light conditions required large pixel sites, which creates a low-resolution image, or cooling mechanisms because the hardware couldn’t perform at room temperature.

The first QIS sensor is a 1-megapixel sensor with a frame rate numbering in the thousands — and the researchers say the technology could easily be upscaled to create higher resolution devices. Because the sensor is so sensitive to light, in the scientific community, the technology could allow scientists to capture images of stars previously too distant to capture, according to phys.org. The project, which was partially funded by the Defense Advanced Research Projects Agency (DARPA), would also have implications for security applications because of the low-light capability.

While the scientific — and even medical — possibilities are intriguing, the low-light sensor could also eventually make its way into the field of cinematography and photography. The greater sensitivity to light would allow the digital sensor to record with a look closer to film, while maintaining the characteristics of a digital file, like easy editing with software.

While the initial QIS sensor has only a million pixels, the sensor is made up of billions of what the researchers call “jots.” These jots function like tiny pixels, and in the most extreme low-light conditions, each jot can collect just one photon, enabling that low-light capability. The QIS sensor uses a layered or stacked design, which has already been introduced in CMOS sensors, using a layer of jots and then a layer of circuits and drivers, allowing the data from those jots to be read at those frame rates in the thousands. That’s how the QIS sensor works in the simplest form, but as the academic research details, there’s much more involved, including techniques to reduce noise.

Of course, the technology won’t ever reach consumer level if the QIS sensor can’t reach the same resolution of today’s CMOS cameras or if it isn’t affordable enough to manufacture. Thankfully, the researchers kept both in mind while developing the first QIS. The jots are arranged in clusters, which allows that first 1-megapixel sensor to be scaled for higher resolution applications. The research team also designed the QIS so that the hardware could be developed using some of the same machines used to develop CMOS, lowering the production costs by using existing equipment.

The QIS sensor has some more work to be done before entering the consumer world — it is currently only monochrome, for example — but if the tech makes its way past medical, scientific and security applications, QIS could mean some serious low-light capabilities for videographers and photographers. Fossum, the inventor of the CMOS and a Dartmouth professor, worked with Jiaju Ma, Saleh Masoodian and Dakota A. Starkey on the project.