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Researchers at the California Institute of Technology (Caltech) may have unveiled a camera capable of 10 trillion frames per second in 2018. However, in 2020, the team has unveiled a camera that only captures 1 trillion frames per second but can image transparent objects.
The newer Caltech camera can also capture more than just physical objects. It can also capture ultra-fast phenomena like shockwaves moving through water and the motion of light itself.
According to a report from researchers who developed the technology, the new camera system is partly based on a century-old technique called phase-contrast microscopy, which makes use of how light waves decelerate and accelerate as they move in and out of transparent objects.
Phase-contrast microscopy uses changing speeds of light and optical techniques to differentiate light that has passed through a transparent object from light that has not. This allows for the transparent object to become more visible.
To create their novel camera technology, the Caltech team modified a phase-contrast microscopy system to enable ultrafast imaging of transparent objects, such as cells, and extremely fast events, such as the firing of a neuron.
The ultrafast imaging elements of the new system are directly derived from the compressed ultrafast technology (CUP) system the Caltech team unveiled in 2018. The new system contained an updated version called lossless encoding compressed ultrafast technology (LLE-CUP). While a lot of extremely quick video-imaging systems capture a sequence of pictures in quick succession, the LLE-CUP system uses a single shot, recording all the movement that takes place during the exposure time.
Because it is faster to capture a single shot than a massive number of shots, LLE-CUP can capture never-before-seen motion, like the motions of light itself.
In the report describing the newer photography system, called phase-sensitive compressed ultrafast photography (pCUP), the researchers described how they could use the system to capture images of a laser pulse passing through a crystal and a laser-induced shockwave propagating through the water.
In a press release, lead researcher Lihong Wang said the pCUP technology has potential applications across many different scientific fields, including biology and physics. For instance, it might be used to watch the dilation of nerve fibers as signals travel along neurons or see how flame front propagates in a combustion chamber.
Developing an Ultrafast Camera System
In the past several years, innovations in both non-linear optics and imaging technology have opened up possibilities for more efficient microscopic analysis of key phenomena in areas like physics and biology. To take full advantage of these technological developments would mean developing a technique to capture imagery in real-time, at an ultra-short temporal resolution, and with a singular exposure.
According to a study published in 2018, Wang was able to expand on existing CUP technology to develop T-CUP, a system capable of capturing 10 trillion frames per second. The T-CUP system was created by using a femtosecond streak camera system with superior data acquisition capabilities, like those used in tomography and other scientific applications.
Wang said his team expanded on the abilities of a femtosecond streak camera by adding a second camera that captured a static image. The team then used a mathematical method known as Radon transformation to acquire high-quality pictures while documenting at the rate of 10 trillion frames per second.
To test the T-CUP system, the research team used it to visualize the real-time focusing of a femtosecond laser pulse. This sequence was documented in 25 frames captured at 400-femtosecond intervals. The imagery depicted the light pulse's form, strength, and angle of inclination.
While that might seem impressive, the study team said at the time that they saw the potential for even faster speeds – up to one quadrillion frames per second.
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