Abstract: A length of optical fiber is attached to a flexible base plate at two spaced apart locations. The portion of the fiber between the two points of connection is under a bias tension. An interferometer is formed in the tensioned portion of the optical fiber. The sensor is mounted to a surface and changes in interference patterns output by the interferometer are monitored to measure strain in the surface.

Abstract: The present invention is an apparatus for combining pulsed or continuous laser beams into a single coherent output beam wherein the laser beams to be combined are directed to intersect at the surface of a sinusoidal phase grating so that each are diffracted into sets of diffracted beams, the first laser beam striking the sinusoidal phase grating from a first angle of incidence and the other laser beam striking it from an angle of incidence which is the negative of the first. The sinusoidal phase grating features a modulation wavelength which causes a preselected order from each resultant set of diffracted beams to propagate in a direction normal to the sinusoidal phase grating and a modulation depth which maximizes the energy distributed into the normally directed, preselected diffraction order. All other orders are suppressed.

Abstract: An interferometer which provides for the precise figure measure of optical surfaces through the interference of two pencil beams, reflected off the optical surface, comprises a laser for generating a laser beam which is split into two parallel beams by a beam splitter and a mirror, the two pencil beams are reflected off a second beam splitter, through an alignment invariant optical device and onto the optical surface to be measured. The two pencil beams are reflected and back-trace through the alignment invariant optical device, propagate through the second beam splitter and enter an optical lens which is capable of focusing two beams in its back focal plane where the interference of the two pencil beams takes place. This information is then relayed through optical spatial filter and optional micro objective into the readout section.

Abstract: The extent of diffraction in a laser resonator is controlled to provide the desired oscillation sustaining feedback. Specifically, a laser system has an annular gain medium disposed about an optical axis. The gain medium has first and second opposite annular ends. A first reflector is disposed on the optical axis closely adjacent to the first end of the gain medium. A second reflector is disposed on the optical axis closely adjacent to the second end of the gain medium. The first and second reflectors are shaped to magnify electromagnetic waves impinging thereon beyond the periphery of one of the reflectors. A sufficiently large portion of the energy incident on an interior region of one of the reflectors to sustain electromagnetic oscillations in the gain medium is diffracted back on itself. In the preferred embodiment, a contoured circular zone plate having a focal point on the optical axis is employed as a diffracting device.

Abstract: An interferometer method for measuring aberrations in a lens system by analysis of a Fourier transform pattern generated by the lens system and the embodiment of this principle for the measurement of aberrations in the human eye and in the general imaging system.