Tokyo (SCCIJ) – Scientists of the Swiss Federal Institute of Technology Lausanne (EPFL), working in association with Japan’s largest optics manufacturer Canon, have developed a camera that can take 3D images with record-breaking speed and resolution. The device named „Mega X“ shoots 24,000 frames per second and captures even a single photon.
EPFL researchers built the first camera which can take picture of a single photon (© EPFL).
A shooting star
“It’s something I’d been dreaming of for a long time,” says professor Edoardo Charbon, head of the Advanced Quantum Architecture Laboratory in EPFL’s School of Engineering. “MegaX is the culmination of over 15 years of research on single-photon avalanche diodes“. These photodetectors are used in next-generation image-sensor technology and have enabled the development of the world’s first million-pixel camera. The Swiss findings have just been published in the journal Optica.
What makes their camera different is that it can capture and count the very smallest form of light particle: the photon. They are invisible to the human eye; we can see only continuous beams of photons, like those used in laser pointers. But MegaX can film the trajectories of individual photons in a ray of light. When shown in video form, they look like shooting stars. “We had to slow the film speed by a factor of 300 million to see individual photons move,” says Charbon.
Incredible speed
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,” says Charbon, “MegaX could be used in applications that incorporate virtual and augmented reality.”
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,” explains Charbon. The process of capturing photons takes just one nanosecond. 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,” explains Charbon. “The ability to calculate it, and to capture a million pixels simultaneously, lets the camera generate 3D images very quickly.”
A 4D camera as goal
One can see how striking the effect is when looking at an example image. With standard cameras, very light and very dark areas in a picture are saturated – our eyes see only black and white. But with MegaX, we can see both light and dark objects equally well. “MegaX lets you increase the dynamic range substantially, far beyond what you can do with a high-definition camera,” says Charbon. But these 15 years of research will not end here.
The remaining main obstacle for commercialization is pixel size. A regular camera has a pixel size of 0.9 micrometers, but in MegaX, it is ten times larger. “Our team is already working on a next-generation MegaX with a pixel size of 2.2 micrometers” adds Charbon. “Our 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, to achieve a higher resolution.”
Text: © Valérie Geneux/EPFL
