Real-time imaging through strongly scattering media: seeing through turbid media, instantly

Abstract

Numerous everyday situations like navigation, medical imaging and rescue operations require viewing through optically inhomogeneous media. This is a challenging task as photons propagate predominantly diffusively (rather than ballistically) due to random multiple scattering off the inhomogenieties. Real-time imaging with ballistic light under continuous-wave illumination is even more challenging due to the extremely weak signal, necessitating voluminous data-processing. Here we report imaging through strongly scattering media in real-time and at rates several times the critical flicker frequency of the eye, so that motion is perceived as continuous. Two factors contributed to the speedup of more than three orders of magnitude over conventional techniques - the use of a simplified algorithm enabling processing of data on the fly, and the utilisation of task and data parallelization capabilities of typical desktop computers. The extreme simplicity of the technique, and its implementation with present day low-cost technology promises its utility in a variety of devices in maritime, aerospace, rail and road transport, in medical imaging and defence. It is of equal interest to the common man and adventure sportsperson like hikers, divers, mountaineers, who frequently encounter situations requiring realtime imaging through obscuring media. As a specific example, navigation under poor visibility is examined.

Image Transmission through Scattering Media Using Ptychographic Iterative Engine

“…The proposed method can be applied in particular to situations where the target can be illuminated with desired patterns-for example, in the application of aircraft landing in cloudy days [30]. In cases where signal lights on the runway can be switched on and off in sequence, it analogously performs a scan of the runway with a 'probe' beam whose aperture equals to the size of the signal light.…”

An all-optical technique enables instantaneous single-shot demodulation of images at high frequency

“…Clearly, rapid techniques providing wide-field demodulation imaging are greatly desirable as they would not only permit real-time applications like navigation, but would also open up possibilities for for 3D ranging and imaging, vibrometry, optical communications, and specialised scientific instrumentation. Such imaging at high frequencies would be a leap forward for imaging through turbid media, a field of interest that has bearing on vision through opaque scattering walls [10][11][12][13][14][15], medical diagnosis [16][17][18][19], food quality analysis [20], transport safety [5,21,22], underwater vision [23] and imaging through fog [3]. Progressing from single-pixel lock-in detection to simultaneous demodulation over millions of pixels to achieve snapshot image demodulation would bring to the realm observation of spatially distributed and fast physical effects that remain otherwise undetectable.…”

A compact single channel interferometer to study vortex beam propagation through scattering layers

“…Light propagation through scattering and turbid medium produce speckle signatures from which it is often difficult to extract useful information. Different techniques have been developed in order to look through both static as well as dynamic scatterers [1][2][3][4][5]. These techniques can be broadly classified into two types.…”