A three-dimensional video showing a pulse of laser light passing through a laser scattering medium and being reflected off reflective surfaces. Image credit: Caltech
In an effort to bring ever faster cameras to the world, Caltech’s Lihong Wang developed technology that can reach 70 trillion frames per second, which is fast enough to see the movement of light. However, just like the camera in your phone, it can only produce flat images.
Now, Wang’s lab has gone a step further to develop a camera that not only records video at incredibly high speed, but also in three dimensions. Wang, Bren Professor of Medical and Electrical Engineering in the Medical Engineering Department of Andrew and Peggy Cherng, describes the device in a new article in the journal Communication with nature.
The new camera, which uses the same underlying technology as Wang’s other Compressed Ultrafast Photography (CUP) cameras, can capture up to 100 billion frames per second. That’s fast enough to take 10 billion pictures, more pictures than the entire human population in the world, in the time it takes to blink your eye.
Wang calls the new iteration “stereo-polarimetrically compressed ultra-fast single-shot photography” or SP-CUP.
In CUP technology, all images of a video are captured in one action without repeating the event. This makes a CUP camera extremely fast (a good cell phone camera can take 60 pictures per second). Wang added a third dimension to this ultra-fast imagery by making the camera “see” more like humans.
When a person looks at the world around them, they perceive that some objects are closer to them and some objects are further away. Such depth perception is possible because of our two eyes, each of which looks at objects and their surroundings from a slightly different angle. The brain combines the information from these two images into a single 3D image.
The SP-CUP camera works essentially the same way, says Wang.
“The camera is now stereo,” he says. “We have a lens, but it functions as two halves that provide two views with an offset. Two channels imitate our eyes. ”
Just like our brains with the signals it receives from our eyes, the computer running the SP-CUP camera processes data from these two channels into a three-dimensional film.
SP-CUP also offers another innovation that nobody possesses: the ability to see the polarization of light waves.
The polarization of light refers to the direction in which light waves vibrate as they travel. Consider a guitar string. When the string is pulled up (e.g. with a finger) and then released, the string vibrates vertically. When the finger plucks it sideways, the string vibrates horizontally. Ordinary light has waves that vibrate in all directions. However, the polarized light has been modified so that its waves all vibrate in the same direction. This can happen naturally, for example when light is reflected from a surface, or through artificial manipulation, as is the case with polarizing filters.
Although our eyes cannot directly sense the polarization of light, the phenomenon has been exploited in a number of applications: from LCD screens to polarized sunglasses and camera lenses in optics to devices that detect hidden stresses in materials and three-dimensional configurations of molecules .
According to Wang, the combination of high-speed three-dimensional images and the use of polarization information makes the SP-CUP a powerful tool that can be applicable to a wide variety of scientific problems. In particular, he hopes this will help researchers better understand the physics of sonoluminescence, a phenomenon in which sound waves create tiny bubbles in water or other liquids. Since the bubbles collapse quickly after they form, they emit a flash of light.
“Some people think this is one of the greatest mysteries in physics,” he says. “When a bubble collapses, its interior reaches such a high temperature that it generates light. The process that makes this possible is very mysterious because it all goes so quickly and we wonder if our camera can help us figure it out. ”
Reference: “Stereo-polarimetrically compressed ultra-fast single image for the speed of light observation of high-dimensional optical transients with picosecond resolution”, October 16, 2020, Communication with nature.
The paper with the title “Single-Shot-Stereopolarimetry-Compressed Ultra-Fast Photography for the Speed of Light observation of high-dimensional optical transients with picosecond resolution” appears in the October 16 issue of Communication with nature. Co-authors are Jinyang Liang, formerly Caltech, now at the National Research Institute in Quebec; Peng Wang, postdoctoral researcher in medical technology; and Liren Zhu, a former PhD student at the Wang Laboratory.
Research funding was provided by the National Institutes of Health.
