Researchers have improved upon a new camera technology that can image at
speeds about 100 times faster than today’s commercial cameras while also
capturing more image frames. The new technology opens a host of new
possibilities for studying extremely fast processes such as neurons
firing, chemical reactions, fuel burning or chemicals exploding.
A research team led by Lihong V. Wang, Gene K. Beare Distinguished
Professor of Biomedical Engineering, Washington
University, St. Louis, USA, previously developed a single-shot
compressed ultrafast photography (CUP) camera that can image at speeds
of 100 billion frames per second in a single camera exposure — fast
enough to capture traveling light pulses. The camera is the world’s
fastest camera that is receive-only, meaning that it can use available
light for imaging and doesn’t need any additional illumination from a
laser or other light source.
In The Optical Society's journal for high impact research, Optica,
the researchers report on a new method that improves the resolution and
quality of images captured with CUP. They demonstrate the CUP upgrades
by capturing a movie of a picosecond laser pulse traveling through the
air and also by pointing laser light onto a printout of a toy car to
create a movie of the light reaching different portions of the car at
Watching neurons fire
Wang and his colleagues are particularly interested in understanding how
the brain’s neural networks operate. Using the new camera with a
microscope could allow them to watch neurons fire by capturing extremely
fast chemical processes called action potentials that travel through an
axon at speeds that can reach more than 100 meters per second.
“We want to use our new camera to study a living animal’s neural network
in action,” Wang said. “This would reveal how the neural network
functions, not just how the neurons are connected. If you were to think
of the neural network as streets in a city, right now we can see the
layout of the streets, but we want to see the traffic to understand how
the whole system functions.”
The improved image resolution and quality reported in the Optica
paper mean that the camera could better capture entire action potential
events, including the initiation of the action potentials, propagation
with varying speeds, and the termination of signaling.
“Biological reactions can occur very fast, faster than standard cameras
can image,” said Wang. “When people study events like that now, they use
a pump-probe method, which requires them to repeat the event many times.
Our camera can be used for real-time imaging of a single event,
capturing it all in one shot at extremely high speeds.”
Since the camera can image with just the light available it could be
used with telescopes to record activities of a supernova occurring light
years away. Wang said that the CUP camera could, for example, add
high-speed imaging to space telescopes such as the Hubble that have high
spatial resolution unperturbed by the atmosphere.
The camera would also be very useful for other applications such as
imaging explosions. “For explosions, the chemical reactions may not be
repeatable, so it is important to capture everything with a single event
in real time,” said Wang. “The camera could also help scientists
studying combustion so that they could improve the fuel efficiency of
cars, for example.”
How it works
The original CUP camera adds a second dimension to the one-dimensional
view of a streak camera — an extremely fast type of camera that measures
the intensity variation of a pulse of light over time. Because this
imaging approach doesn’t directly create an image from the raw data
acquired by the camera, computer algorithms are necessary to convert the
data into an image.
In the new work, the researchers added an external charge-coupled
device, or CCD, that provides more information for the image
reconstruction, leading to a higher quality image. The researchers also
developed a new algorithm to merge the data from the external CCD with
the data from the streak camera. With the improvements, the researchers
generated images with finer spatial resolution, higher feature contrast
and cleaner background.
Paper: L. Zhu, Y. Chen, J. Liang, Q. Xu, L. Gao, C. Ma, L. Wang, "Space-
and intensity-constrained reconstruction for compressed ultrafast
photography," Optica, 3, 7, 694 (2016).
Optica is an open-access, online-only journal dedicated to the
rapid dissemination of high-impact peer-reviewed research across the
entire spectrum of optics and photonics. Published monthly by The
Optical Society (OSA), Optica provides a forum for pioneering
research to be swiftly accessed by the international community, whether
that research is theoretical or experimental, fundamental or applied. Optica
maintains a distinguished editorial board of more than 30 associate
editors from around the world and is overseen by Editor-in-Chief Alex
Gaeta, Columbia University, USA. For more information, visit Optica.
About The Optical Society
Founded in 1916, The Optical Society (OSA) is the leading professional
organization for scientists, engineers, students and entrepreneurs who
fuel discoveries, shape real-life applications and accelerate
achievements in the science of light. Through world-renowned
publications, meetings and membership initiatives, OSA provides quality
research, inspired interactions and dedicated resources for its
extensive global network of optics and photonics experts. For more
information, visit osa.org/100.
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