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Scientists at Swiss research institute, EPFL, in partnership with imaging experts, Canon, have developed a camera that can take 3D images with record-breaking speed and resolution. According to Edoardo Charbon, an EPFL professor and head of the Advanced Quantum Architecture Laboratory in EPFL’s School of Engineering, the camera, also called the MegaX, is the culmination of over 15 years of research on single photon avalanche diodes (SPADs), which are photodetectors used in next-generation image-sensor technology. It is currently being touted as the world’s first million-pixel camera.

A Shooting Star

What makes the camera different is that it can capture and count the very smallest form of light particle: the photon. Photons are invisible to the human eye; one can see only continuous beams of photons, like those used in laser pointers. But MegaX can film the trajectories of individual photons in rays of light. When shown in video form, they look like shooting stars. According to Charbon, the team had to slow the film speed by a factor of 300 million to see individual photons move.

But there’s more to it. MegaX is extremely fast and can take up to 24,000 images per second; in comparison, movies are filmed at 24 images per second. MegaX also has three other important advantages: it has a very large dynamic range, can produce 3D representations and can perform in-depth segmentations of those representations – all at the same time. Thanks to its high resolution and advanced detection capabilities,MegaX could be used in applications that incorporate virtual and augmented reality.

Reconstructing 3D Images

So how exactly does the camera work? It captures individual photons and converts them into electric signals that are stored in a digital memory system. The process of capturing photons takes just one nanosecond, or 1x10-9 seconds. The camera can also detect exactly when a photon hits a sensor and measure how much time it took for the photon to travel between the object that emitted it and the camera, and therefore calculate that distance. That time is called the time-of-flight. The ability to calculate it, and to capture a million pixels simultaneously, is what lets the camera generate 3D images very quickly.

Both Light and Dark

As seen in the example image (Fig b), one can see how striking the effect is. With standard cameras, very light and very dark areas in a picture are saturated – human eyes see only black and white. But with MegaX, one can see both light and dark objects equally well. MegaX helps in increasing the dynamic range substantially, far beyond what can be done with a high-definition camera.

So when can one buy a MegaX? Not at this point, according to Charbon. The main obstacle is pixel size. A regular camera has a pixel size of 0.9 µm, but the pixel size in MegaX is ten times larger, at 9 µm. The team is already working on a next-generation MegaX with a pixel size of 2.2 µm. The goal isn’t necessarily to make MegaX work like a conventional camera, but rather to create a 4D camera – the three standard dimensions plus time – with as many pixels as possible, in order to achieve a higher resolution.

The result was published in the science journal Optica.