Camera Takes 1 Trillion Frames per Second

A shockwave created by a laser striking water propagates in slow motion, as captured by a new ultrafast photography technology. (Source: Caltech)

A little over a year ago, Caltech’s Lihong Wang developed the world’s fastest camera, a device capable of taking 10 trillion pictures per second. It is so fast that it can even capture light traveling in slow motion. But sometimes just being quick is not enough. Indeed, not even the fastest camera can take pictures of things it cannot see. To that end, Wang, Bren Pro­fessor of Medical Engi­neering and Electrical Engi­neering, has developed a new camera that can take up to 1 trillion pictures per second of transparent objects.

The camera technology, which Wang calls phase-sensitive compressed ultra­fast photo­graphy (pCUP), can take video not just of transparent objects but also of more ephemeral things like shock­waves and possibly even of the signals that travel through neurons. Wang explains that his new imaging system combines the high-speed photo­graphy system he previously developed with an old technology, phase-contrast micro­scopy, that was designed to allow better imaging of objects that are mostly trans­parent such as cells, which are mostly water.

Phase-contrast micro­scopy, invented nearly 100 years ago by Dutch physicist Frits Zernike, works by taking advantage of the way that light waves slow down and speed up as they enter different materials. For example, if a beam of light passes through a piece of glass, it will slow down as it enters the glass and then speed up again as it exits. Those changes in speed alter the timing of the waves. With the use of some optical tricks it is possible to distinguish light that passed through the glass from light that did not, and the glass, though trans­parent, becomes much easier to see.

“What we’ve done is to adapt standard phase-contrast micro­scopy so that it provides very fast imaging, which allows us to image ultra­fast phenomena in trans­parent materials,” Wang says. The fast-imaging portion of the system consists of something Wang calls lossless encoding compressed ultrafast technology (LLE-CUP). Unlike most other ultrafast video-imaging techno­logies that take a series of images in succession while repeating the events, the LLE-CUP system takes a single shot, capturing all the motion that occurs during the time that shot takes to complete. Since it is much quicker to take a single shot than multiple shots, LLE-CUP is capable of capturing motion, such as the movement of light itself, that is far too fast to be imaged by more typical camera tech­nology.

Now, Wang and his fellow researchers demons­trate the capabilities of pCUP by imaging the spread of a shockwave through water and of a laser pulse traveling through a piece of crystal­line material. Wang says the tech­nology, though still early in its development, may ulti­mately have uses in many fields, including physics, biology, or chemistry. “As signals travel through neurons, there is a minute dilation of nerve fibers that we hope to see. If we have a network of neurons, maybe we can see their communi­cation in real time,” Wang says. In addition, he says, because tempera­ture is known to change phase contrast, the system “may be able to image how a flame front spreads in a combus­tion chamber.” (Source: Caltech)

Reference: T. Kim et al.: Picosecond-resolution phase-sensitive imaging of transparent objects in a single shot, Sci. Adv. 6, eaay6200 (2020); DOI: 10.1126/sciadv.aay6200

Link: Caltech Optical Imaging Laboratory, California Institute of Technology, Pasadena, USA

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