What do drops of water, a bouncing rubber ball, and a tear running through fabric have in common? They are all fast-occurring phenomena’s worthy of catching by camera. However, conventional cameras are not quick enough to capture such images and high-speed cameras break the bank.
Now, researchers have created a new imaging technique known as Virtual Frame Technique (VFT) that can produce thousands of images of such phenomena as they occur step by step. VFT can be used from any device including a smartphone and has been shown to perform better than high-speed cameras.
Watch this video of a water drop impacting surface:
"If you use a regular camera to take a picture of a drop of water hitting a dry surface, the water's movement will cause the picture to be blurry. But these blurred areas are precisely where the phenomenon is taking place, both spatially and temporally. That's what our technique uses to piece together the underlying phenomenon," says John Kolinski, a professor at EPFL's School of Engineering.
The VFT methodology begins by analysis of a conventional photo before deconstructing the blurry portions of pictures. "This initial illumination step must be done correctly so that the blurry parts of the picture contain the right information and can be used. At this point the object must have a quantifiable instantaneous state of either completely blocking the light or completely letting it through," says Kolinski. The next step is to employ advanced image-processing methods to improve the conventional picture's temporal resolution and specific illumination scheme, and then turn it into a binary image -- that is, containing either black or white pixels.
Credit: © 2019 Jamani Caillet
VFT is advantageous because it doesn’t require intensity values—it depends on amount of information the sensor of a camera can obtain. "It's like taking time-lapse photos of a nearly instantaneous phenomenon," says Kolinski.