Virtual Frame Technique captures incredibly high-speed video with any camera
High-speed cameras offer more than simply breath-taking slow motion captures of fast-moving events. Scientists and engineers often turn to these advanced imaging technologies to better understand things like rocket launches, lightning and viper strikes, and now researchers in Switzerland are proffering such folks a brand new tool they say will work with any kind of camera.
Called Virtual Frame Technique, the new imaging method was cooked up at the École polytechnique fédérale de Lausanne's (EPFL) Engineering Mechanics of Soft Interfaces Laboratory, where scientists worked together with Harvard University researchers to develop a new way to capture rapid, everyday events in incredible detail.
Key to the technique is that light is carefully shone on the subject just as the event takes place, be it a drop of water hitting a surface, fabric being torn, or perhaps a balloon being popped. When these kinds of rapid occurrences are snapped with a regular camera, the resulting image will likely be blurry. But by illuminating the subject in the right way as the photo is taken, the scientists say they can show these high-speed events in a new light, so to speak.
"This initial illumination step must be done correctly so that the blurry parts of the picture contain the right information and can be used," explains John Kolinski, a professor at EPFL's School of Engineering. "At this point the object must have a quantifiable instantaneous state of either completely blocking the light or completely letting it through."
From here, the team is able to process the photo into a binary image, where objects are shown in either black or white pixels with nothing in between. Because a piece of fabric is either torn or intact, and a surface is either wet or dry, the team is able to forego the thousands of greyscale values assigned to each pixel in a normal image, and use sensor's capabilities to simply paint them in black and white instead.
The researchers say this allows them to achieve far greater frame rates while maintaining full spatial resolution, or the number of pixels in the image. So much so, they say they have achieved 65 MHz frame rate at 4-megapixel resolution, which is equivalent to 65 million fps, and that in principle, a modern smartphone is capable of more than a million fps using the technology.
"It's like taking time-lapse photos of a nearly instantaneous phenomenon," says Kolinksi.
The researchers say they tested the imaging technique using all kinds of cameras, from regular smartphones to professional-grade shooters, and that when the objects were illuminated in the right way it consistently returned the desired results. You can see it demonstrated with a water droplet in the video below, while a paper describing the research was published in the journal Optics Express.