What if we could design a camera that could take a hundred billion pictures in a second ― enough to record the fastest phenomena in the universe.
Sounds like science fiction, right?
But it’s not: a new ultrafast imaging system developed at Washington University can do just that.
Biomedical engineer Lihong Wang and his research lab have already invented or discovered a whole bunch of high tech imaging techniques, like functional photoacoustic tomography, dark-field confocal photoacoustic microscopy, time-reversed ultrasonically encoded optical focusing ― and a lot of other things I had never heard of.
So it probably won’t come as a surprise that the new camera Wang’s team has developed isn’t exactly your ordinary point-and-shoot. "For the first time, humans can literally see light pulses traveling in space at the speed of light,” Wang said.
The speed of light is just over 186,282 miles per second. Going that fast, it would take you about a second to go all the way around the world ― seven and a half times.
“Based on Einstein’s Theory of Relativity, any mass or energy can propagate only up to the speed of light,” Wang said. “So we’re literally talking about the fastest phenomenon in the world.”
This video captured by Wang’s new imaging system shows a laser pulse propagating in air and being reflected from a mirror. The movie is slowed down 10 billion times to make it visible to the human eye. (Credit Lihong Wang, Washington University)
How do you take a picture of a light pulse moving at the speed of light? Wang says you start with something called a streak camera. “The streak camera is a very specialized device that allows us to convert time into space,” Wang said.
Just how do you do that?
“We convert light particles, or photons, into electrons, then pull the electrons really hard at different rates, depending on the time of arrival,” Wang said. “So, the time of arrival will be converted into different vertical positions on the ultimate CCD camera.”
Thus turning time into space. Simple, right?
Wang’s new technology improves on previous ultrafast cameras in two important ways.
Up until now, streak cameras could only take a one-dimensional snapshot ― think of it like trying to take a picture of something flying by really fast behind a vertical slit.
And the fastest cameras had to have an external light source to work.
Wang’s technique doesn’t need special lighting, and it produces two-dimensional images ― more like a regular photograph ― but at a rate of one every 10 trillionths of a second.
Dartmouth biomedical engineer Brian Pogue called Wang’s invention "impressive."
“Anytime that you create a system that images a thousand times faster than what exists today, that’s a big deal,” Pogue said.
Pogue said this new way of visualizing the movement of light could lead to major scientific breakthroughs in fields like physics ― and military defense. “Things like optical cloaking,” Pogue said.
In science fiction, cloaking is a technology that can make an object ― like a spaceship ― disappear. Pogue says it’s something the military would like to be able to do in real life. “There’s a lot of interest in getting light to bend around objects, so it sort of looks like you’re seeing through them,” Pogue said.
Pogue said Wang’s new system would allow researchers to image the light as it bends ― something they haven’t been able to do before, and that could help make optical cloaking a reality.
Lihong Wang envisions many other uses for the new camera. Combined with a microscope, it could be used to image chemical reactions inside of human cells. Paired with the Hubble Telescope, it could take detailed pictures of ultrafast astronomical phenomena, like supernovas.
“This is the first time humans can ever see phenomena like this,” Wang said. “We would imagine many new discoveries could be made down the road.”
Follow Véronique LaCapra on Twitter: @KWMUScience