DRUM camera taps projector tech for images at nearly 5 million fps
Generally speaking, if you want to grab sharp images of crazy fast movements such as molecular interactions or water droplets, you're going to need a super-expensive rig. Researchers have developed a system built using projector tech that could significantly cut the cost.
A research team made up of members from Canada's Institut national de la recherche scientifique (INRS), Concordia University and Meta Platforms has developed a novel camera that's able to capture an event in a single exposure at 4.8 million frames per second with "a temporal resolution of 0.37 µs, and a sequence depth of seven frames."
That doesn't even come close to Caltech's achievement a few years back, but the DRUM technology was built using off-the-shelf components and comes in at a fraction of the cost of commercially available systems.
"Our camera uses a completely new method to achieve high-speed imaging," said Jinyang Liang of INRS. "It has an imaging speed and spatial resolution similar to commercial high-speed cameras but uses off-the-shelf components that would likely cost less than a tenth of today’s ultra-fast cameras, which can start at close to $100,000."
The development centers around a new time-gating method dubbed time-varying optical diffraction. In a regular camera, gating in the shape of the shutter controls the amount of light hitting the sensor. Time-gating involves rapidly opening and closing the gate a few times to capture a short high-speed video.
Liang and team came up with a way to time-gate using light diffraction, which involved "rapidly changing the tilt angle of periodic facets on a diffraction grating" to produce a number of replicas of incident light moving in different directions. This effectively gated out frames at different time points to generate a very short ultra-fast time-lapse movie.
"Luckily, it is possible to accomplish this type of swept diffraction gate by using a digital micromirror device (DMD) – a common optical component in projectors – in an unconventional way," said Liang. "DMDs are mass-produced and require no mechanical movement to produce the diffraction gate, making the system cost-efficient and stable."
The diffraction-gated real-time ultra-high-speed mapping (DRUM) camera is able to capture seven frames for each of these movies. The project's multidisciplinary team tested the apparatus by recording a laser interacting with distilled water, which "showed the evolution of a plasma channel and the development of a bubble in response to a pulsed laser."
The bubble dynamics of a carbonated drink and the interactions between a cell sample from an onion and an ultra-short laser pulse were also captured by the DRUM camera. Work to further refine the technology is ongoing, but the researchers see potential applications in biomedicine and LiDAR systems for autonomous transport.
A paper on the project has been published in the journal Optica.