Imaging the behaviour of photons is difficult. Light is the fastest thing we've ever recorded in the universe, and catching its trajectory on film requires extraordinary high speeds.
A new camera developed by researchers at Washington University in St Louis may be just the thing to enable new discoveries about light. They're claiming it's the world's fastest 2D receive-only camera, able to capture images at a rate of up to 100 billion frames per second using a technique its creators call Compressed Ultrafast Photography.
Current receive-only cameras image at a speed of around 10 million frames per second, limited by on-chip storage and electronic readout speed.
"For the first time, humans can see light pulses on the fly," said study leader Lihong Wang, PhD, Gene K. Beare Distinguished Professor of Biomedical Engineering.
"Because this technique advances the imaging frame rate by orders of magnitude, we now enter a new regime to open up new visions. Each new technique, especially one of a quantum leap forward, is always followed a number of new discoveries. It's our hope that CUP will enable new discoveries in science -- ones that we can't even anticipate yet."
The technology consists of an array of devices, such as microscopes and telescopes paired with lenses to capture events. The whole thing is centred around an existing piece of technology, called a "streak camera", an ultrafast device that measures the intensity variation of a pulse of light over time. Streak cameras, however, only record in one dimension; the algorithms and components added by Wang and his team expanded this into two dimensions.
The lens captures the photons, sending them through a long tube to a digital micromirror device the size of a small coin, with around a million micromirrors on board, each about seven microns squared. These encode the image, then reflect the beams to a beam splitter; this, in turn, shoots the the photons into the streak camera's slit. This converts the photons to electrons, which are then sheared with electrodes in order to convert time into space -- 2D. The voltage of the electrodes increases, so that the electrons arrive at different times and land in different positions.
This raw data is then stored in a charge-coupled device, to be sent to a computer, where it is processed into an image using computational imaging.
Its applications include biomedicine, where it can be used to image fluorescent proteins -- a highly worthy use -- but its potential expands much, much farther.
"Fluorescence is an important aspect of biological technologies. We can use CUP to image the lifetimes of various fluorophores, including fluorescent proteins, at light speed," Wang said.
Then he added, "Combine CUP imaging with the Hubble Telescope, and we will have both the sharpest spatial resolution of the Hubble and the highest temporal solution with CUP. That combination is bound to discover new science."
The full study, "Single-shot compressed ultrafast photography at one hundred billion frames per second," can be found online in the journal Nature.