By Brian Santo, contributing writer
Swedish researchers have developed a camera that can record at a rate equivalent to 5 trillion images per second. That’s so fast, the researchers say, that they can film chemical and physical reactions never before captured on film. It’s the latest innovation – and speed record – in super-extra-ultra-insanely fast photography.
The researchers, from Lund University in Sweden, further the advancements of their predecessors from MIT (with the participation of scientists at the University of Zaragoza in Spain), who, in 2011, created a camera that can film at roughly 1 trillion frames per second (fps).
The MIT-based group found that their femtocamera could emit a pulse of light and was fast enough to not only detect light that got reflected back, but detect light that bounced off of multiple surfaces before returning to the camera. It meant that the camera could literally see around corners. MIT professor Ramesh Raskar talks about this in a 2012 TED Talk.
The MIT camera is what is called a streak camera. As a practical matter, what that means is that in order to build a two-dimensional image, the camera has to take many, many exposures from a slightly different position each time. The technology is exotic and the process is complex, but the essential filmmaking process is a variation of standard operating procedure in videography: Take multiple images and then display them in time sequence.
The new, faster femtocamera developed by a team at the University of Lund works differently. In essence, it creates a motion picture from a single image. The researchers call the process frequency recognition algorithm for multiple exposures, or Frame. To put the femtocamera’s speed into context, consider that the number of femtoseconds in a single second is significantly larger than the number of seconds in a person’s life-time — that’s the sort of scale we’re dealing with.
The method, they write, is based on “superimposing a structural code onto the illumination to encrypt a single event, which is then deciphered in a post-processing step.” The coding strategy allows — in fact, requires — the use of “laser probing with arbitrary wavelengths/bandwidths to collect signals with indiscriminate spectral information, thus allowing for ultrafast videography with full spectroscopic capability,” say the Lund researchers in their paper .
In short, they have developed a technique for encoding light and an algorithm that allows them to decrypt the encoded information from a single exposure to render a time-sequenced set of images.
The Lund femtocamera can, thus, capture a single, non-repetitive event — an apparently unique capability. The MIT femtocamera can’t do it because it must perform an experiment over and over to reconstruct a sequence. There are other imaging technologies that the Lund researchers explain fall short for various other reasons.
The Lund group demonstrated femtosecond imaging, but said that the minimum temporal resolution is dictated only by laser pulse duration; they pointed out that attosecond lasers exist (the scale goes nano, pico, femto, then atto, followed by zepto and yocto).
The new femtocamera can capture phenomena in biology, chemistry, and physics. Because Frame is not restricted to any particular wavelength, it can be used with a wide variety of lab equipment, whether it’s based on absorption, scattering, fluorescence, polarization, wave mixing, and coherence, the researchers said in their paper.
Image via Nature
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