Synthetic-aperture chirp confocal imaging.

An imaging system that combines synthetic-aperture imaging, holography, and an optical chirp with confocal imaging is described and analyzed. Comparisons are made with synthetic-aperture radar systems. Adaptation of several synthetic-aperture radar techniques to the optical counterparts is suggested.

Investigation of ultrafast time gating by spatial filtering.

With a spatial-filtering method of gating, we explore image formation through scattering media using first-arriving light. Gating times of a few femtoseconds and less are produced, and the resolution at these extremely short gating times is investigated.

Realization of time gating by use of spatial filtering.

A method for simulating conventional time gating in low-coherence optical imaging processes in highly scattering media is given. The method uses monochromatic instead of broadband light, and spatial filtering is substituted for time gating. The process enables the study of imaging techniques in scattering media to be carried out in an easy and highly controllable way. Experimental results are given.

Electronic channel fringe holography for depth and delay measurements.

Electronic spectral holography in the form developed by Shih [Ph.D. dissertation, University Microfilms, Ann Arbor, Mich. (1995)] is adapted to various applications, including optical coherence tomography in scattering media, contouring of surfaces, and optical fiber mode examination.

Ensemble-averaged Shack-Hartmann wave-front sensing for imaging through turbid media.

A technique is described for ensemble-averaging the light wave emerging from a turbid medium, enabling the recovery of optical information that is otherwise lost in a speckle pattern. The technique recovers both an amplitude and a phase function for a wave that has been corrupted by severe scattering, without the use of holography. With the phase estimated, an ensemble-averaged field is constructed that can be backprojected to form an image of the object obscured by the scattering medium. Experimental results suggest that the technique can resolve two object points whose signals are unresolved on the exit surface of a diffuser.

Three-dimensional confocal imaging of objects embedded within thick diffusing media.

Confocal scanning methods are modified to allow 3-D imaging of objects embedded within thick diffusing media. A method called exfoliative deconvolution is used to sharpen a volume image in which the blur is depth variant. Experimental results are presented.

Imaging absorbing structures within thick diffusing media.

A linear and space invariant model for imaging absorbing structures within thick diffusing structures illuminated by coherent light is developed. Experimental, theoretical, and computer simulation results compare ordinary broad beam images with confocal and deconvolved-confocal images; the resolution is improved by factors of ~2 and 3, respectively.