Max Epstein

Optical surface waves along a toroidal metallic guide

An approximate analysis shows that rays guided inside a torus oscillate sinusoidally around the equator. Expressing the Helmholtz equation in toroidal coordinates yields the equivalent index of refraction. The equation can be solved, yielding Airy functions in the direction perpendicular to the surface. Along the surface the equation is similar to that for media with a quadratic index profile, the Hermite‐Gaussian solutions of which follow sinusoidal trajectories while oscillating in width. Experimental verification of these features is presented.

Invariant properties of helical‐circular metallic waveguides

Experimental evidence shows that toroidal or helical‐circular metallic waveguides, operating on the whispering‐gallery principle, can be bent significantly without affecting either their ray‐guiding or modal properties. These remarkable properties, reported here for the first time for any type of surface guide, result from the fact that the allowed deformations are geodesic and conserve the curvature of the rays. Scanning in one or two dimensions with a diffraction‐limited beam has been achieved.

Whispering-gallery CO 2 laser

The design and operation of a CW CO2laser based on the whispering-gallery principle is reported. The optical cavity consists of a portion of the equatorial region of a torus terminated by two flat mirrors. In agreement with theoretical expectations, the output beam is found to be TE polarized, and to consist of low-order Airy-Hermite-Gaussian modes.

Optical absorption in polymer glasses by laser calorimetry

Optical absorption in polystyrene and poly(methyl methacrylate) was measured in the visible region of radiation. Two methods of data evaluation yield consistent results to indicate that near λ=500 nm, the absorption coefficient is approximately 2×10−4 cm−1, or less than 100 dB/km, for both materials.

Backscattering patterns of step index optical fibers: angular width

Angular widths of laser backscattering patterns from optical fibers with thin claddings due to rays reflected by core-cladding interface are investigated. Calculated and measured values are presented and found to be in good agreement. A summary of different backscattering patterns from clad fibers is given.

Misalignment in imaging multifibers

A statistical approach is used to characterize image transmission through misaligned multifibers, i.e., differently arranged at the input and output faces, leading to a spatially invariant line spread function. The resulting MTF is the product of the MTF for the aligned system and a function characterizing stochastic departures from alignment. The case of circular fibers with Gaussian misalignment is treated theoretically and is found to account satisfactorily for experimentally observed results.

Efficient white laser illuminators for plastic optical fibers

Multiwavelength lasers are used to compensate for color distortion in transmission of light through plastic optical fibers. Efficient methods to eliminate the speckle effect and to generate multicolor laser light are described.

Robot Eye-In-Hand Using Fiber Optics

For many applications, eye-in-hand robot vision has several advantages over the use of a fixed external camera. Even smaller solid state cameras are too bulky for gripper mounting and, therefore, limit the grippers movement for many operations. A novel approach for eye-in-hand robot vision is proposed utilizing, a) coherent fiber-optic bundles for carrying light from an object to be imaged, and b) photodiodes to convert this light into electrical signals for processing. The feasibility of this concept has been experimentally demonstrated by developing a fiber-optic eye-in-hand system, mounting the scanner head on a gripper and obtaining good images under back and front light conditions.

Coupling of rigid to flexible imaging multifibers

By magnifying the high-quality image produced by a rigid miniature endoscope onto a large flexible multifiber, an instrument has been developed which provides both high resolution and flexibility. It is shown theoretically, and verified experimentally, that the MTF of a system of coupled multifibers is the product of the individual MTFs. Measurements show that the coupled instruments outperform state-of-the-art all-flexible systems. The technique should greatly facilitate observation, display, and photography in percutaneous endoscopy and in a variety of industrial applications.

Fiber optic beam delivery for endoscropic holography

Abstract Fiber optic methods to deliver the object and reference beams in endoholography are described. Two novel approaches are introduced, and quantitatively compared along with two other methods, on the basis of stability, power efficiency, and maximum power density. A method utilizing a three-layer coaxial fiber structure is shown to be most promising. Preliminary holograms have been obtained with a commercial single-mode fiber, the object beam being coupled out of the cladding by a bend in index-matching liquid.