Marc P. Christensen

The presence of a scattering medium in the imaging path between an object and an observer is known to severely limit the visual acuity of the imaging system. We present an approach to circumvent the deleterious effects of scattering, by exploiting spectral correlations in scattered wavefronts. Our Synthetic Wavelength Holography (SWH) method is able to recover a holographic representation of hidden targets with sub-mm resolution over a nearly hemispheric angular field of view. The complete object field is recorded within 46 ms, by monitoring the scattered light return in a probe area smaller than 6 cm × 6 cm. This unique combination of attributes opens up a plethora of new Non-Line-of-Sight imaging applications ranging from medical imaging and forensics, to early-warning navigation systems and reconnaissance. Adapting the findings of this work to other wave phenomena will help unlock a wider gamut of applications beyond those envisioned in this paper.

The submission examines the role of illumination diversity in recovering shape, texture and motion of objects hidden from view. Focused spots incident on a scattering wall are used to spatially pattern the illumination within the hidden volume.

Motion of objects hidden from view is recovered by tracking displacements in speckle patterns produced by the coherently illuminated object. A latent image may additionally be recovered by examining spatial correlations in the speckle pattern.

A computational imager combining ideas from correlography and phase retrieval is used to recover images of non-line-of-sight (NLoS) objects. It exploits the intrinsic roughness of real-world surfaces to indirectly illuminate NLoS objects and intercept the return.

Macroscopic imagers are subject to constraints imposed by the wave nature of light and the geometry of image formation. The former limits the resolving power while the latter results in a loss of absolute size and shape information. The suite of methods outlined in this work enables macroscopic imagers the unique ability to capture unresolved spatial detail while recovering topographic information. The common thread connecting these methods is the notion of imaging under patterned illumination. The notion is advanced further to develop computational imagers with resolving power that is decoupled from the constraints imposed by the collection optics and the image sensor. These imagers additionally feature support for multiscale reconstruction.

Optical imaging systems in which the lens and sensor are free to rotate about independent pivots offer greater degrees of freedom for controlling and optimizing the process of image gathering. However, to benefit from the expanded possibilities, we need an imaging model that directly incorporates the essential parameters. In this work, we propose a model of imaging which can accurately predict the geometric properties of the image in such systems. Furthermore, we introduce a new method for synthesizing an omnifocus (all-in-focus) image from a sequence of images captured while rotating a lens. The crux of our approach lies in insights gained from the new model.

A spatiotemporal approach for recovering holograms is proposed in this paper. Flutter-shutter camera is used for temporal demodulation. The proposed method needs lesser measurements than phase shifting interferometry to extract the hologram.

Angular dependence of surface/sub-surface scattering from rough reflecting sample is examined, as evidenced in objective speckle patterns acquired at standoff, to decouple the single and multiply-scattered light using Principal-Component -Analysis.