Design of binary-phase diffusers for a compressed sensing snapshot spectral imaging system with two cameras.

We propose designs of pupil-domain optical diffusers for a snapshot spectral imaging system using binary-phase encoding. The suggested designs enable the creation of point-spread functions with defined optical response, having profiles that are dependent on incident wavefront wavelength. This efficient combination of dispersive and diffusive optical responses enables us to perform snapshot spectral imaging using compressed sensing algorithms while keeping a high optical throughput alongside a simple fabrication process.

Dual-camera snapshot spectral imaging with a pupil-domain optical diffuser and compressed sensing algorithms.

We propose a snapshot spectral imaging method for the visible spectral range using two digital cameras placed side-by-side: a regular red-green-blue (RGB) camera and a monochromatic camera equipped with a dispersive diffractive diffuser placed at the pupil of the imaging lens. While spectral imaging was shown to be feasible using a single monochromatic camera with a pupil diffuser [Appl. Opt.

Combining and collimation of RGB laser beams with transmissive resonance domain diffractive optics.

Resonance domain diffractive optical elements for combining RGB laser beams into a single collimated beam were designed, fabricated, and experimentally investigated. The input RGB beams were angular separated up to tens of degrees and set in a nearly Bragg arrangement for high diffraction efficiency. A single resonance domain diffractive lens delivered beam combining and collimation functions with reasonable residue divergence.

Multifunctional binary diffractive optical elements for structured light projectors.

A set of diffractive optical elements for multiple-stripe structured illumination was designed, fabricated and characterized. Each of these elements with a single layer of binary surface relief combines functions of a diffractive lens, Gaussian-to-tophat beam shaper, and Dammann beam splitter. The optical investigations of laser light patterns at 20° fanout angle reveal up to 88% diffraction efficiency, high contrast, and nearly diffraction limited resolution.

Resonance-domain diffractive microlens arrays.

High-efficiency resonance-domain diffractive microlens arrays with high numerical apertures and 100% fill factor were designed, fabricated, and characterized. Fabricated arrays of eight off-axis microlenses with pitch 127 μm and numerical aperture 0.2 demonstrated diffraction-limited collimation of fiber light at 632.

Mapping of spectral signatures with snapshot spectral imaging.

We propose a snapshot spectral imaging method that enables direct reconstruction of spatial maps for spectral signatures of given materials using a monochromatic image sensor. An image-plane array of dispersive shapers converts an aerial image of an object into a tailored mixture of spectral and spatial data that is sensed and digitally processed to reconstruct weight coefficients of the spectral signatures. The feasibility of the method is proven by computer simulations.

Tunable resonance-domain diffraction gratings based on electrostrictive polymers.

Critical combination of high diffraction efficiency and large diffraction angles can be delivered by resonance-domain diffractive optics with high aspect ratio and wavelength-scale grating periods. To advance from static to electrically tunable resonance-domain diffraction grating, we resorted to its replication onto 2-5 μm thick P(VDF-TrFE-CFE) electrostrictive ter-polymer membranes. Electromechanical and optical computer simulations provided higher than 90% diffraction efficiency, a large continuous deflection range exceeding 20°, and capabilities for adiabatic spatial modulation of the grating period and slant.

Shift-bonded resonance-domain diffraction gratings.

Resonance-domain-transmission diffractive optics with grating periods comparable to those of the illumination wavelength offers large angles of light deflection and nearly 100% Bragg diffraction efficiency. Optical design preferences for nearly normal incidence can be met by proper choice for the slant of the diffraction grooves relative to the substrate. However, straightforward fabrication of the slanted submicron high-aspect-ratio grooves is challenging.

Coherent imaging with a resonance domain diffractive lens in laser light.

We investigated coherent imaging with a binary off-axis resonance domain diffractive lens using three lasers in visible wavelengths. The relations between the dispersion of this lens, shape of its point spread function, and spectral properties of these lasers were analyzed theoretically and experimentally. In particular, we measured the point spread function, imaging contrast, and diffraction efficiency.

Compressed sensing snapshot spectral imaging by a regular digital camera with an added optical diffuser.

We propose a spectral imaging method that allows a regular digital camera to be converted into a snapshot spectral imager by equipping the camera with a dispersive diffuser and with a compressed sensing-based algorithm for digital processing. Results of optical experiments are reported.

Design of dense transmission diffraction gratings for high efficiency.

We propose a design method for dense surface-relief diffraction gratings with high efficiency in transmission mode. Closed-form analytical relations between diffraction efficiency, polarization, and grating parameters are derived and verified in the resonance domain of diffraction under general three-dimensional angles of incidence traditionally termed conical mounting. A powerful tool for rigorous design of computer-generated holograms and diffractive optical elements with spectroscopic scale periods is now enabled.

Chromatic dispersion of a high-efficiency resonance domain diffractive lens.

Inherent strong lateral and longitudinal chromatic dispersion of a transmission resonance domain off-axis diffractive lens were studied theoretically and experimentally. It is shown that a 4 mm diameter and 0.14 NA diffractive lens provides both focusing and dispersion with a spectral resolution of up to 0.

Diffractive optical elements for mode-division multiplexing of temporal signals with the aid of Laguerre-Gaussian modes.

Optical aspects of space-division multiplexing with orthogonal modes of coherent light were considered in theory and experiments with the coherent optical correlator. We resorted to the mathematical tool of generating functions and technologies of diffractive optical elements to implement complex spatial filters matched to rotationally symmetrical transverse modes. Successful multiplexing and demultiplexing in free-space transmission of low-frequency temporally modulated signals through different spatial modes was demonstrated.

Resonance domain surface relief diffractive lens for the visible spectral region.

Early expectations for a role of diffractive lenses were dramatically lessened by their high order overlapping foci, low optical powers, and competing advances in refractive micro-optics. By bringing the Bragg properties of volume holograms to diffractive lenses we got rid of ghost diffractive orders and the critical trade-off between diffraction efficiency, number of phase levels, and spatial feature-size. Binary off-axis resonance domain diffractive lens with high numerical aperture of 0.

Design and experimental investigation of highly efficient resonance-domain diffraction gratings in the visible spectral region.

Surface-relief resonance-domain diffraction gratings with deep and dense grooves provide considerable changes in light propagation direction, wavefront curvature, and nearly 100% Bragg diffraction efficiency usually attributed only to volume optical holograms. In this paper, we present design, computer simulation, fabrication, and experimental results of binary resonance-domain diffraction gratings in the visible spectral region. Performance of imperfectly fabricated diffraction groove profiles was optimized by controlling the DC and the depth of the grooves.

Novel approach for extending the depth of field of Barcode decoders by using RGB channels of information.

A specially designed phase mask embedded in the lens assembly of an imaging system is shown to provide different response in the three major color bands, R, G and B of a detector array. Each channel provides optimal performance for different depth of field regions, such that the three channels jointly provide an imaging system with wide depth of field. The approach is useful in particular for Barcode imagers.

Pupil coding masks for imaging polychromatic scenes with high resolution and extended depth of field.

An algorithm for the design of imaging systems with circular symmetry that exhibit high resolution as well as extended depth of field for polychromatic incoherent illumination is presented. The approach provides a significant improvement over a publication [1] where the design was carried for a single wavelength. The approach is based on searching for a binary phase pupil mask that provides imaging with the highest cut-off spatial frequency, while assuring a desired contrast value over a given depth of field.

Diffractive optical elements with porous silicon layers.

We investigate the basic chromatic properties of dispersive surface relief diffractive optical elements with porous silicon (PSi) layers. Rigorous and scalar wavelength-dependent diffraction efficiencies are juxtaposed and compared to reflection coefficients of uniform silicon and PSi layers. The application of the device as an enhanced sensor is discussed.

Analogy between generalized Coddington equations and thin optical element approximation.

Local wavefront curvature transformations at an arbitrarily shaped optical surface are commonly determined by generalized Coddington equations that are developed here via a local thin optical element approximation. Eikonal distributions of the incident and refracted beams are calculated and related by an eikonal transfer function of a local thin optical element located in close proximity to a given point at a tangent plane of an optical surface. Main coefficients and terms involved in the generalized Coddington equations are derived and explained as a local nonparaxial generalization for the customary paraxial wavefront transformations.

Spectral multiplexing method for digital snapshot spectral imaging.

We propose a spectral imaging method for piecewise "macropixel" objects, which allows a regular digital camera to be converted into a digital snapshot spectral imager by equipping the camera with only a disperser and a demultiplexing algorithm. The method exploits a "multiplexed spectrum" intensity pattern, i.e.

Mode-matched phase diffractive optical element for detecting laser modes with spiral phases.

A new type of diffractive optical element for detecting and measuring the power distribution of transverse modes emanating from radially symmetric laser resonators is presented. It is based on a relatively simple straightforward design of a phase-only diffractive optical element that serves as a matched filter, which correlates between specific prerecorded transverse modes with a certain azimuthal mode order and those in the incident laser light. Computer simulations supported by experimental results demonstrate how such elements can accurately detect modes with spiral phases and provide quantitative results on the modal power distribution.

Pilot studies to demonstrate that intestinal mucosal afferent nerves are functionally linked to visceral adipose tissue.

Dietary capsaicin reduces rodent visceral fat weight. We tested the hypothesis that intact intestinal mucosal afferent nerve function is necessary for fat deposition in visceral adipose tissue sites. Rats were treated daily for 2 weeks with intragastric (chronic treatment) vehicle or capsaicin.

Analytic design and solutions for resonance domain diffractive optical elements.

A model for designing and analyzing complicated surface relief diffractive elements in the resonance domain is developed. It is based on subdividing the complicated diffractive element into many highly efficient local diffraction gratings whose surface relief modulations can be effectively characterized as slanted volume gratings for which closed form analytic solutions exist. The model is illustrated by finding in the resonance domain the local period, effective slant angle, and groove depth at each location on an off-axis cylindrical diffractive lens.

Planar configuration for image projection.

A flat panel, compact virtual image projection display is presented. It is based on a light- guided optical configuration that includes three linear holographic gratings recorded on one planar transparent substrate so as to obtain a magnified virtual image for a small input display. The principles of the projection display, unique design, and procedures for experimentally recording an actual planar configuration are presented, along with evaluation results.

Extended focus diffractive optical element for Gaussian laser beams.

The depth of focus of the Gaussian beam is extended by introducing a wavefront phase correction with properly designed diffractive optical elements. Results of the computer simulations show that, compared with other methods, the presented method demonstrates a reduced focal spot size and low sidelobes in a focal domain, within a considerable range of defocusing distances. Experimental results for the visible range diffractive optical element with a focus of 40 mm and a depth of focus that extends to 1 mm agree with the theory.