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.

Ultrafast, cross-correlated harmonic imaging through scattering media.

A simple upconversion scheme utilizing 40-fs pulses is shown to permit high-contrast imaging of objects obscured by a highly scattering medium when no ballistic component is evident in the scattered light and imaging is performed with any portion of the scattered light pulse. We present a time-gated, inherently low-pass spatially filtered imaging method that minimizes signal-averaging requirements and greatly facilitates imaging under severe scattering (turbid) conditions.

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.

Spatially partially incoherent and broad spectrum holographic stereo vision.

We suggest a technique that allows reconstruction of three-dimensional objects with spatially incoherent broad-spectrum illuminating light sources. The reconstruction is obtained by the realization of a holographically recorded parallax-based stereo vision. Experimental results demonstrate the suggested technique.

Volume reflection holographic confocal imaging.

The Denisyuk volume reflection hologram is produced with spatially incoherent light to form an image-plane hologram. The image formed in readout combines the properties of volume holography and confocal image formation.

Spectral holography for coherence-gated imaging.

A spectral-holography application called spectral-decomposition holography forms a recorded image according to optical path length. In this method all wavelength components of a broad-spectrum source simultaneously backlight a nonscattering binary-phase object. A spectral hologram is thus recorded. Subsequent computer processing recovers temporally discriminated images.

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.

High-resolution optical chirped pulse gating.

We describe a system for achieving high-resolution range gating using optically chirped pulses. The technique converts signals from the time domain into signals in the frequency domain through a nonlinear, sum-frequency generation process. The technique is based on similar methods used in microwave radar. We draw analogies between our method and conventional and time-lens imaging processes, and present experimental results demonstrating the method.

Broad-source image plane holography as a confocal imaging process.

The process of image plane holography with incoherent illumination has many significant properties. The process can produce extremely high-quality, low-noise images, section slicing, image formation through inhomogeneities, and high-resolution image formation through small apertures. The process of confocal imaging has similar properties. We describe the similarities and differences between the two processes.

Superresolution by spatial-temporal encoding methods.

The Lukosz technique of superresolution by spatial and temporal frequency interaction is extended. The effects of various misalignments and other errors are considered. An implementation of the technique is presented. Experimental results are given.

Imaging through scattering media using spatial incoherence techniques.

Imaging of objects embedded in scattering media can be accomplished by sources with reduced spatial coherence instead of pulsed light or short temporal coherence light.

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.

Small-aperture, high-resolution, two-channel imaging system.

A method that utilizes incoherent light interferometry is used to form images through vanishingly small apertures. The method utilizes the increased channel capacity produced by reduction of spatial coherence, but in a way thatimproves the resolution instead of the signal-to-noise ratio.

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.

Grating interferometers for producing large holographic gratings.

Methods for producing large holographic diffraction gratings are described. In particular, the advantages of using a grating interferometer illuminated with a noncollimated beam from either an extended monochromatic source or an extended polychromatic source are described along with some of the problems that arise and methods to solve them. Experimental results illustrating the grating interferometer's ability to produce straight uniform fringes when illuminated with such noncollimated wavefronts are given.

Tandem coherent-incoherent filtering in scanning optical microscopy.

A method of imaging through inhomogeneities using the principles of scanning optical microscopy is described.

One-way phase conjugation with partially coherent light and superresolution.

Limitations on the one-way phase-conjugation technique are described. These limitations are reduced or eliminated by reducing the spatial coherence of the light and by reducing the aperture of the imaging system. By introducing a suitable level of superresolution of the kind previously described as superresolution by incoherent-tocoherent conversion, the aperture and coherence reductions reduce the effect of the optical path inhomogeneities. However, the aperture reduction does not degrade the diffraction-limited resolution limit.

Sawtooth profile fringes with a two-grating interferometer.

The theory of fringe formation of arbitrary profile in a two-grating interferometer is developed emphasizing sawtooth profile fringes. Two methods of fringe synthesis are given: the spatially incoherent illumination method, leading to a coherent synthesis and the temporally incoherent (polychromatic) illumination method, leading to an incoherent synthesis.