Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Recovering color images from scattered light

30.07.2019

New technique non-invasively separates spectral bands from scattered light

Engineers at Duke University have developed a method for extracting a color image from a single exposure of light scattered through a mostly opaque material. The technique has applications in a wide range of fields from healthcare to astronomy.


Researchers have created a method that takes light from colored numerals (top left) that has been scattered by a mostly opaque surface (top center) and uses its 'speckle' patterns and a coded aperture to reconstruct the image in five different frequencies (bottom row) before combining them into a final image (top right).

Credit: Michael Gehm, Duke University

The study appeared online on July 9 in the journal Optica.

"Others have been able to reconstruct color images from scattered light, but those methods had to sacrifice spatial resolution or required prior characterization of the scatterer in advance, which frequently isn't possible," said Michael Gehm, associate professor of electrical and computer engineering at Duke. "But our approach avoids all those issues."

When light is scattered as it passes through a translucent material, the emerging pattern of "speckle" looks as random as static on a television screen with no signal. But it isn't random.

Because the light coming from one point of an object travels a path very similar to that of the light coming from an adjacent point, the speckle pattern from each looks very much the same, just shifted slightly.

With enough images, astronomers used to use this "memory effect" phenomenon to create clearer images of the heavens through a turbulent atmosphere, as long as the objects being imaged were sufficiently compact.

While the technique fell out of favor with the development of adaptive optics, which do the same job by using adjustable mirrors to compensate for the scattering, it has recently became popular once again. Because modern cameras can record hundreds of millions of pixels at a time, only a single exposure is needed to make the statistics work.

While this approach can reconstruct a scattered image, it has limitations in the realm of color. The speckle patterns created by different wavelengths are typically impossible to disentangle from one another.

The new memory effect imaging approach developed by the authors Xiaohan Li, a PhD student in Gehm's lab, Joel Greenberg, associate research professor of electrical and computer engineering, and Gehm breaks through this limitation.

The trick is to use a coded aperture followed by a prism. A coded aperture is basically a filter that allows light to pass through some areas but not others in a specific pattern. After the speckle is "stamped" by the coded aperture, it passes through a prism that causes different frequencies of light to spread out from each other.

This causes the pattern from the coded aperture to shift slightly in relation to the image being captured by the detector. And the amount it shifts is directly related to the color of light passing through.

"This shift is small compared to the overall size of what's being imaged, and because our detector is not sensitive to color, it creates a messy combination," said Li. "But the shift is enough to give our algorithm a toehold to tease the individual speckle patterns apart from each color, and from that we can figure out what the object looks like for each color."

The researchers show that, by focusing on five spectral channels corresponding to violet, green and three shades of red, the technique can reconstruct a letter "H" full of nuanced pinks, yellows and blues. Outside of this difficult proof-of-principle, the researchers believe their approach could find applications in fields such as astronomy and healthcare.

In astronomy, the color content of the light coming from astronomical phenomena contains valuable information about its chemical composition, and speckle is often created as light is distorted by the atmosphere. Similarly in healthcare, color can tell researchers something about the molecular composition of what's being imaged, or it can be used to identify biomolecules that have been tagged with fluorescent markers.

"There are a lot of applications where people really want to know how much energy there is in specific spectral bands emitted from objects located behind opaque occlusions," said Greenberg. "We've shown that this approach can accomplish this goal across the visible spectrum. Knowing the aperture pattern and how much it shifts as a function of wavelength provides the key we need to disentangle the messy sum into separate channels."

###

This research was supported by the Defense Advanced Research Projects Agency (HR0011-16-C-0027).

CITATION: "Single shot multi-spectral imaging through a thin scatterer," Xiaohan Li, Joel A. Greenberg, and Michael E. Gehm. Optica, July, 2019. DOI: 10.1364/OPTICA.6.000864

Media Contact

Ken Kingery
ken.kingery@duke.edu
919-660-8414

 @DukeU

http://www.duke.edu 

Ken Kingery | EurekAlert!
Further information:
https://pratt.duke.edu/about/news/speckle-color
http://dx.doi.org/10.1364/OPTICA.6.000864

More articles from Power and Electrical Engineering:

nachricht Hot electrons harvested without tricks
18.11.2019 | University of Groningen

nachricht New laser opens up large, underused region of the electromagnetic spectrum
15.11.2019 | Harvard John A. Paulson School of Engineering and Applied Sciences

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Atoms don't like jumping rope

Nanooptical traps are a promising building block for quantum technologies. Austrian and German scientists have now removed an important obstacle to their practical use. They were able to show that a special form of mechanical vibration heats trapped particles in a very short time and knocks them out of the trap.

By controlling individual atoms, quantum properties can be investigated and made usable for technological applications. For about ten years, physicists have...

Im Focus: Images from NJIT's big bear solar observatory peel away layers of a stellar mystery

An international team of scientists, including three researchers from New Jersey Institute of Technology (NJIT), has shed new light on one of the central mysteries of solar physics: how energy from the Sun is transferred to the star's upper atmosphere, heating it to 1 million degrees Fahrenheit and higher in some regions, temperatures that are vastly hotter than the Sun's surface.

With new images from NJIT's Big Bear Solar Observatory (BBSO), the researchers have revealed in groundbreaking, granular detail what appears to be a likely...

Im Focus: New opportunities in additive manufacturing presented

Fraunhofer IFAM Dresden demonstrates manufacturing of copper components

The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Dresden has succeeded in using Selective Electron Beam Melting (SEBM) to...

Im Focus: New Pitt research finds carbon nanotubes show a love/hate relationship with water

Carbon nanotubes (CNTs) are valuable for a wide variety of applications. Made of graphene sheets rolled into tubes 10,000 times smaller than a human hair, CNTs have an exceptional strength-to-mass ratio and excellent thermal and electrical properties. These features make them ideal for a range of applications, including supercapacitors, interconnects, adhesives, particle trapping and structural color.

New research reveals even more potential for CNTs: as a coating, they can both repel and hold water in place, a useful property for applications like printing,...

Im Focus: Magnets for the second dimension

If you've ever tried to put several really strong, small cube magnets right next to each other on a magnetic board, you'll know that you just can't do it. What happens is that the magnets always arrange themselves in a column sticking out vertically from the magnetic board. Moreover, it's almost impossible to join several rows of these magnets together to form a flat surface. That's because magnets are dipolar. Equal poles repel each other, with the north pole of one magnet always attaching itself to the south pole of another and vice versa. This explains why they form a column with all the magnets aligned the same way.

Now, scientists at ETH Zurich have managed to create magnetic building blocks in the shape of cubes that - for the first time ever - can be joined together to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

High entropy alloys for hot turbines and tireless metal-forming presses

05.11.2019 | Event News

 
Latest News

Structure of a mitochondrial ATP synthase

19.11.2019 | Life Sciences

The measurements of the expansion of the universe don't add up

19.11.2019 | Physics and Astronomy

Ayahuasca compound changes brainwaves to vivid 'waking-dream' state

19.11.2019 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>