Search for: All records

A randomly scattering analyzer with a multi-element fixed detector aperture located in the far field is introduced as a means to access enhanced spatial sensing information associated with far-subwavelength spatial features. This sensing method allows far-subwavelength spatial resolution with coherent fields scattered from a moving object, or some other relative change that causes a modified field incident on the detector aperture. Experimental optical speckle correlation data with a translated diffusing structure show the salient features, and understanding in relation to the experimental variables is supported by numerical simulations. The conclusion is that more-heavily-scattering analyzers provide better spatial resolution because the measurements are more sensitive to changes in the incident field. Such randomly scattering analyzers offer a new dimension for sensitive coherent optical metrology related to various sensing and motion application domains requiring large offset distances. 

A statistical treatment of speckle correlations as a function of the position of a moving object is shown to provide access to object information through thick and heavily scattering random media. Experiments for a patch-like object of varying size and for varying degree of background scatter are explained using a model, and an experimental study allows evaluation of key attributes. Given a sufficient signal-to-noise ratio, adequate coherence, and developed field statistics, measured speckle intensity patterns from a set of object positions can allow high-resolution imaging deep into an obscuring medium and the medium's scattering strength can be gauged quantitatively with calibration. This enables new opportunities in application domains such as optical sensing, material inspection, and deep tissue in vivo imaging. 

We present a general theory for optical imaging of moving objects obscured by heavily scattering random media. Measurements involve collecting a series of speckle intensity images as a function of the position of a moving object. A statistical average intensity correlation can be formed with the potential to provide access to microscopic and macroscopic information about the object. For macroscopic objects and translation distances that are both large relative to the wavelength, there is a clear method to invert measurements to form an image of the hidden object. Opportunities exist for super-resolution sensing and imaging, with far-subwavelength resolution. Importantly, there is no fundamental limit to the thickness of the background randomly scattering medium, other than the practical requirement of detecting an adequate number of photons and sufficient background scatter for developed Gaussian field statistics. The approach can be generalized to any wave type and frequency, under the assumption that there is adequate temporal coherence. Applications include deep tissue in vivo imaging and sensing in and through various forms of environmental clutter. The theory also provides another dimension for intensity interferometry and entangled state detection to the case with motion of the scatterer or emitter.