In an on-line scanning sensor system, certain components of an FT-IR interferometer are isolated from vibrations that cause inaccuracies in measurements provided by the system, thereby allowing the sensor system to be used on-line in manufacturing environments. More particularly, vibration-absorbing suspension devices suspend selected interferometer components such that the center of suspension of the suspended interferometer component is substantially coincident with the center of gravity of th...

An interferometer includes: a first glass plate optically coupled to a second glass plate, forming an optical interferometric cavity therebetween; a first reflective coating coupled to the first glass plate within the optical interferometric cavity, where the first reflective coating is partially reflective; a second reflective coating coupled to the second glass plate within the optical interferometric cavity, where the second reflective coating is at least partially reflective; and a tuning pl...

Methods and apparatus for reducing the effects of non-isotropic gas distributions on interferometry measurements are disclosed.

An optical interferometer (100) includes a first optical interferometer (200) disposed on a front surface side of a workpiece (W) and a second optical interferometer (300) disposed on a rear surface side of the workpiece (W). The first optical interferometer (200) and the second optical interferometer (300) each include a light emitting section (210, 310), a wire grid (220, 320) and an interference fringe sensor (230, 330). Wire alignment directions of the wire grid (220) of the first optical in...

A passive optical system substantially simultaneously separates light received at an optical input into three or more output light beams on optical outputs. The output light beams may have intensities that are proportional to intensities of optical projections of the received light onto three or more basis vectors of a tetrahedral basis set of a Stokes space. The system includes either multiple partial polarization splitters or multiple optical interferometers.

A polarization independent (PI) interferometer design that can be built from standard optical components is described. Based upon a Michelson interferometer, the PI interferometer uses a 50/50 splitter and Faraday Rotator Mirrors (FM's). The interferometer achieves good optical characteristics, such as high extinction ratio (ER) and low insertion loss (IL). Lack of polarization sensitivity reduces interferometer construction tolerances and cost, enhances performance and utility, and expands the ...

An interferometer for measuring the flatness, variation of thickness and parallelism of large, thin transparent wafers held vertically and undistorted by gravitational forces. A sodium lamp provides monochromatic light that is diffusely reflected off a background screen towards the wafer. A reference flat surface is positioned sufficiently closely to the wafer that an interference fringe pattern is formed that is a measure of the air gap between the reference flat surface and the surface of the ...

At least two discrete quarter wave plates are provided for use as plane mirrors or reflectors in a displacement measuring interferometer, where the plates share common or substantially common reflecting surface geometries. A plurality of geometrically matched discrete matched quarter wave plates reduces the amount of tilt between an input beam provided to, and an output measurement beam provided by, an interferometer, resulting in increased interferometer dynamic range.

An interferometer includes a means for splitting, at a splitting location, an input light beam into a first beam and a second beam; and means for recombining, at a recombination location, the first beam and the second beam. The interferometer is designed such that the first beam will travel a first optical path length (OPL) from the splitting location to the recombination location, and the second beam will travel a second OPL from the splitting location to the recombination location and such tha...

A Mach-Zehnder interferometer having two optical couplers interconnected by two optical fibers at least one of which is temperature insensitive. In use, temperature induced changes in the geometrical length and refractive index of the temperature insensitive fibers offset each other so that the optical path length of the fiber is unaffected by the temperature change. Where two temperature insensitive fibers are included these may be of the same or of different lengths. The interferometer may be ...