The researchers managed to expand the field of view for speckle-related imaging with limited memory effects

In our daily lives, if you've ever experienced watching the sunrise on a cloudy morning or driving with sweaty palms in thick fog, you'll find that trying to see through scattered media such as smog is often accompanied by disappointment and even difficulty
.
For researchers in optics and photonics, penetrating scattering media is also a long-term challenge in a wide range of applications, such as microscopy imaging of biological tissues and telescope observation
through atmospheric turbulence.

To address this challenge, speckle-related imaging has evolved into an emerging technique with non-invasive nature and minimal optical setup, which has advantages over existing methods such as wavefront shaping and transmission matrices, although they are capable of imaging
with strong scattering media.

However, speckle-related imaging is not always practical
.
It works on the premise of a physical property called the memory effect – assuming the displacement invariance of the speckle pattern during scattering, which is known to be severely limited
when the medium is thicker.

Recently, researchers at the University of Tokyo and Osaka University have developed a promising solution to make speckle-related imaging work properly
with limited memory effects.
On September 30, they published their research
in the journal Intelligent Computing.

"When the scattering medium is thick, one problem with speckle-related imaging is the small field of view due to the limited range of memory effects," the
researchers noted.

To overcome this bottleneck, they proposed a method
to extend the field of view of single-shot speckle-related imaging.
"The proposed method takes into account speckle-related attenuation under limited memory effects and infers correlation
during reconstruction," the researchers explain.
"Our method estimates both the attenuation
associated with object and speckle-based gradient descent methods.
"

On this basis, the proposed method is verified numerically and experimentally, and the application of the proposed algorithm (considering the attenuation function) and the traditional algorithm (without considering the attenuation function) in the reconstruction process is compared
.

In the experiment, the researchers reconstructed the point source behind the scattering medium using minimal optical settings, without any imaging optics: from left to right, there was incoherent light, a bandpass filter, a diffuser, an object illuminated by diffuse light (an aluminum foil with 15 holes), another diffuser, and an image sensor
that captured the light passing through the object.

By comparing and analyzing the reconstructed images obtained by the proposed algorithm and the traditional algorithm, it is found that the proposed algorithm recovers a larger field of view than the traditional algorithm, and its estimated attenuation parameters are consistent
with the measured attenuation parameters.

The researchers concluded: "By extrapolating finite autocorrelation, this result validates our concept of speckle-related imaging under the extended field of
view.
"

According to the researchers, this proposed method is easily adapted to traditional speckle-related imaging methods without any optical modification
.
In addition, this single speckle-related imaging method can also be extended to multidimensional speckle-related imaging, thus facilitating imaging applications
in various fields such as biomedicine, astronomy, and safety.

This study was supported by grants from the Japan Association for the Promotion of Science KAKENHI: JP20H02657, JP20K05361 and JP20H05890
.