Walls are mirrors with new imaging technique

Jul 16, 2012 by Nancy Owano weblog

(Phys.org) -- A child's dream wanting to come true: putting on a magic cape to see around corners and through walls, solving mysteries and catching criminals. Scientists, meanwhile, are achieving the same optical powers with knowledge and labs if not capes. A study published yesterday, “Looking around corners and through thin turbid layers in real time with scattered incoherent light,” is attracting much attention in its description of the technique, using a spatial light modulator to undo the scattering that makes objects opaque or non-reflecting. Their technique allows real-time imaging through opaque materials and around highly scattering optical diffusers.

The paper, published yesterday in Nature Photonics, is authored by Ori Katz, Eran Small and Yaron Silberberg. Prof Silberberg and his colleagues are with the Ultra Fast Optics Group at the Weizmann Institute of Science in Israel. They are being said to have “pushed the limits” of what spatial light modulators (SLMs) can do.

SLMs modify the phase of an incoming light beam. Like a series of ocean waves, the waves in light can be slowed down or redirected when they hit materials. The team’s “wavefront shaping” involves using the SLM so that it refocuses at a desired location. Exploiting the angular range in which a single wavefront pattern inverts scattering allows wide-field real-time imaging through a single process.

“We show that wavefront-shaping enables wide-field imaging through turbid layers with incoherent illumination, and imaging of occluded objects using light scattered from diffuse walls,” the authors said.

“Our results bring wavefront-shaping closer to practical applications and realize the vision of looking through walls and around corners.”

This is not the first attempt to explore correcting for scattering, with a number of research efforts in evidence over recent years. In 2010 there was news of a prototype camera that was developed by scientists that can shoot around corners, making use of an ultra-short high-intensity burst of laser light to illuminate a scene.

The Weizmann Institute team provides real-time imaging in a different way. As reported in Nature Photonics, the is quick, simple and uses natural light rather than lasers.

The main power of the technique is said to be that it can work with incoherent . Unlike past wavefront approaches, this technique does not require a coherent source, interferometric detection, raster scanning or off-line computational reconstruction.

Earth-based astronomy and deep tissue imaging are two relevant areas that could make use of the study’s findings, as both astronomy and deep tissue imaging are challenged by scattering and dense materials.

Talking about future applications, principal investigator Silberberg said, “Our technique for imaging through scattering layers may allow that study of previously inaccessible biological samples by optical imaging, e.g., imaging through thin egg shells for studying embryonic development.”

Silberberg further explained what could make a difference. “If you want to look to see an embryo developing inside an egg but the eggshell scatters everything, or you want to look through the skin, scattering is the main enemy there, and time-of-flight is not a good solution.” He was referring to the "time-of-flight" approach with a laser-based camera. He envisions that the primary use for their technique will be in biological and medical studies.

Explore further: New technique detects microscopic diabetes-related eye damage

More information: Looking around corners and through thin turbid layers in real time with scattered incoherent light, Nature Photonics (2012) doi:10.1038/nphoton.2012.150 (Preprint is available on Arxiv)

Abstract
Imaging with optical resolution through turbid media is a long sought-after goal with important applications in deep tissue imaging. Although extensively studied, this goal was considered impractical until recently. Adaptive-optics techniques, which can correct weak aberrations, are inadequate for turbid samples, where light is scattered to complex speckle patterns with a number of modes greatly exceeding the number of degrees of control. This conception changed after the demonstration of coherent focusing through turbid media by wavefront-shaping, using spatial light modulators. Here, we show that wavefront-shaping enables wide-field imaging through turbid layers with incoherent illumination, and imaging of occluded objects using light scattered from diffuse walls. In contrast to the recently introduced schemes for imaging through turbid media, our technique does not require coherent sources, interferometric detection, raster-scanning or off-line reconstruction. Our results bring wavefront-shaping closer to practical applications and realize the vision of looking through ‘walls’ and around corners.

Related Stories

Nanoparticle imaging: A resonant improvement

Oct 28, 2011

Raman spectroscopy is a powerful technique for analyzing atomic structure based on the inelastic scatter of light from molecules, with diverse applications including medical imaging and chemical sensing. Researchers ...

Light Scattering Method Reveals Details under Skin

Apr 12, 2005

A new optical method that can image subsurface structures under skin has been demonstrated by scientists at the National Institute of Standards and Technology (NIST) and the Johns Hopkins University Applied Physics Laboratory. The met ...

Recommended for you

Robotics goes micro-scale

22 hours ago

(Phys.org) —The development of light-driven 'micro-robots' that can autonomously investigate and manipulate the nano-scale environment in a microscope comes a step closer, thanks to new research from the ...

High power laser sources at exotic wavelengths

Apr 14, 2014

High power laser sources at exotic wavelengths may be a step closer as researchers in China report a fibre optic parametric oscillator with record breaking efficiency. The research team believe this could ...

Combs of light accelerate communication

Apr 14, 2014

Miniaturized optical frequency comb sources allow for transmission of data streams of several terabits per second over hundreds of kilometers – this has now been demonstrated by researchers of Karlsruhe ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Graeme
5 / 5 (1) Jul 16, 2012
This used a 40x60 pixel spatial light modulator. and a bandpassfilter about 0.5%. The images were too dim to see with the eye. Offline computation was needed for a genetic optimisation alorithm to control the spatial light modulator.

More news stories

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Robotics goes micro-scale

(Phys.org) —The development of light-driven 'micro-robots' that can autonomously investigate and manipulate the nano-scale environment in a microscope comes a step closer, thanks to new research from the ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.

Leeches help save woman's ear after pit bull mauling

(HealthDay)—A pit bull attack in July 2013 left a 19-year-old woman with her left ear ripped from her head, leaving an open wound. After preserving the ear, the surgical team started with a reconnection ...