Light has a speed of 300 thousand kilometers per second (186 thousand miles per second). It takes 8 minutes and 20 seconds for light to reach Earth from the Sun. A pulse of light can make approximately 4 revolutions around Earth in one second. Speed of light is just staggering and so is the newly developed technology called Compressed Ultrafast Photography(CUP).

Compressed Ultrafast Photography

Faster than light photography!

Memories are sweeter. Our brain can be scribed with the memories and we do want to have memories more substantial, so people keep souvenir and make paintings. Nowadays its easier with photos and videos we can take with our mobile phones.

A photo/picture of an object is just an image made by light reflected from that object. Since light is continuously being reflected, it is important how fast the image is captured.

Swiftness of photography

A human visual system can perceive about 10 distinct images per second. So to catch everyday visual experience we need to have a device that can capture more than 10 distinct images per second.

But many physical phenomena happens faster and hence cannot be perceived by us. So with the quest of capturing the phenomenon which cannot be perceived by the human visual system, photography became swifter as the days passed by.

The early day silent movies used to have image frames rate of 16 – 25 fps. Today almost everyone has camera embedded mobile phones, the imaging speed of these cameras ranges from 30 – 300 frames per second (fps) i.e. they can take a picture in 30th to 300th fraction of a second or even higher. So, one might wonder how fast is the fastest camera on the Earth?

Started from the periodic opening and closing of shutter to capture the image frames, the photography has now developed to Compressed Ultrafast Photography (CUP). CUP is a two-dimensional dynamic imaging technique which can capture image up to 100 billion frames per second!!

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Since light would have travelled only three millimetres in 100 billionth fraction of second, this swift photography technique enables us to capture light within a millimetre range.

So this technique is even faster than light and can capture even the movement of light making us wonder about the motion that we have never dream of.

What is CUP and how does it work?

CUP is streak photography technique with compressed sensing.  In streak photography, an evolving scene is captured by deflecting incoming light an amount proportional to time. In early days, the light deflection was mechanical, done by rotating mirror but for high speed like Compressed Ultrafast Photography in modern days the light goes to a plate (photo-cathode) which ejects electrons.

The electrons are deflected by applying voltage which ends up producing light striking on a phosphorescence screen. This produces a time-dependent deflection of electrons which maps with the time variation of the light pulse into the camera’s profile detector. From these patterns, after some laborious mapping and encoding of spatial pattern, reconstruction of an image can be done.

Compressed sensing allows us to collect minimum data for excluding the unnecessary ones by the use of a filter so that the real-time image can be extracted.

Is CUP faster than light photography

The Compressed Ultrafast Photography (CUP) technique is stupendously fast. It was experimented in media laboratory of MIT in 2011 and had a speed of 1 trillion fps but this approach could only work for scenes that can be replayed at will with nearly perfect reproducible nature. It took them an hour to have enough shots to make real-time video representing just a fraction of seconds.

The 100 billion fps imaging was carried out at Washington University at St. Louis during early 2015 by Lihong Wang and coworkers and pictures were taken in a single shot.

Although sounds simple there are hefty algorithms as well as the setup is much more complicated. All that matters is that this technique is likely to contribute to the study of high-speed biological activities, many interstellar activities like supernovae, nuclear reactions, etc.

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Ashwin Khadka is a Physics graduate from Tribhuvan University, Kathmandu, Nepal. He is a science enthusiast, researcher and writer. Apart from writing he is also a researcher, with specialization on thin films for electrodes in solar cells.

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