Abstract: The invention is directed to a system and method for implementing process control for tubing thickness using sonic NDE techniques. The system may, for example, generate ultrasound waves in a test object during the manufacturing process. A detector such as an interferometer may be used to detect the ultrasound waves. An interpreter or analyzer may determine the tubing or sheet thickness from the waves. Then, a control system may determine and implement an appropriate control action on the process.

Abstract: A laser cavity optical architecture of a solid-state laser gyro measures rotational velocity or angular position and is based on a global conservation of the scale factor so that each parameter varies with temperature and avoids optical mode hops.

Abstract: Low coherence light is divided into measuring light and reference light. The measuring light is collected to be projected onto an object of measurement. Intensities of the reflected light in a plurality of positions in the direction of depth are detected by carrying out a Fourier analysis on each channeled spectrum obtained by decomposing the detected interference light into frequency components. The optical path length of the reference light is stepwise changed to adjust the optical path length within the focusing range of the measuring light. A plurality of pieces of data representing the intensity of the reflected light are obtained in a plurality of positions in the direction of depth each time the position of the focusing range changes, and data on the position in the direction of depth where the measuring light is in the focusing range is extracted out of the pieces of data.

Abstract: A double pass apparatus for detecting defects on a disk surface includes a light source that generates a light beam and a beamsplitter that splits the light beam into a first light beam portion and a second light beam portion. A modulator is provided that modulates the second light beam portion into a frequency shifted modulated light beam for illuminating the surface of the disk. The frequency shifted modulated light beam is twice reflected from the surface of the disk, thus doubling the frequency shift of the reflected light beam. A polarizing beamsplitter combines the first light beam portion with the reflected light beam portion providing an interference signal.

Abstract: A system for determining at least one condition of a bearing including an optical fiber for transmitting light from a light source. The optical fiber is embedded in the bearing and operatively coupled to an interferometric system. The interferometric system is operatively coupled to a processor. The interferometric system provides the processor with information relating to wear of the optical fiber, and the processor determines wear of the bearing, rate of wear and remaining useful life of the bearing based on the information relating to wear of the optical fiber.

Abstract: In common path time domain OCT/OCR devices optical radiation from a source is first split into two replicas, which are then delivered to an associated sample by an optical fiber probe. The tip of the optical fiber probe serves as a reference reflector and also serves as a combining element that produces a combination optical radiation by combining an optical radiation returning from the associated sample with a reference optical radiation reflected from the reference reflector. The topology of the devices eliminates the necessity of using Faraday mirrors, and also allows for registering a cross-polarized component of the optical radiation reflected or backscattered from the associated sample, as well as a parallel-polarized component.

Abstract: The technology described here enables the use of an inexpensive laser to measure an interferometric response of an optical device under test (DUT) at reflection lengths significantly greater than the coherence length of the laser. This is particularly beneficial in practical interferometric applications where cost is a concern. In other words, inexpensive lasers having shorter coherence lengths may be used to achieve very high interferometric measurements at longer DUT reflection lengths. The technology also enables the use of such inexpensive lasers to measure Rayleigh scatter in commercial-grade, single-mode optical fiber.

Abstract: An ultra-miniature interferometric fiber-optic encoder readhead for sensing displacement of a very fine pitch scale grating is disclosed. The readhead includes a source grating that diffracts diverging source light into +/? 1st order beams, a pair of mirrors that reflect the +/? 1st order beams to converge toward the scale grating. The +/? 1st order scale light beams are reflectively diffracted back from scale grating to return to the mirrors, and are then reflected to converge back toward the light source and a set of adjacent fiber-optic receiver channels. An interference field generating grating positioned in front of the receiver channels produces interference fringes having a desired pitch. Movement of the interference fringes is sensed by the fiber-optic receiver channels to provide displacement information. The readhead may be configured so that primarily or only +/? 1st order light reaches the receiver channels.

Abstract: An alignment stage includes a first plane mirror which extends in two directions substantially perpendicular to each other in order to measure the position of a stage in the translation direction and the tilt of the stage in the direction of height, a first measurement unit which irradiates the plane mirror with a laser beam and measures the position of the stage in the translation direction by using reflection of the laser beam, and a second measurement unit which irradiates the first plane mirror with a laser beam and measures the position by using reflection of the laser beam at a position vertically spaced apart from the firs measurement unit in order to measure the tilt of the stage.

Abstract: Device for white light interferometry comprising a light source of main emission wavelength ?0 and spectral width ?? and an evaluating unit with a line sensor of pixel width P for detecting an interference fringe pattern with a fringe spacing F, a mask being placed in front of the line sensor having a periodically modulated light transmittance along said line sensor, characterized in that the period length M of the mask is such as to fulfill the condition ? ? ? ? ? 0 < ? 1 - F M ? < 1 2 ? F P - ? ? ? ? ? 0 .

Abstract: The present invention provides an optical filter assembly that reduces the phase and amplitude noise of a detection laser used to detect ultrasonic displacements. The filtered detection laser is directed to the surface of a remote target. Ultrasonic displacements at the surface scatter the filtered detection laser. Collection optics then gather phase modulated light scattered by the surface and direct the phase modulated light to an optical processor to produce a signal representative of the ultrasonic displacements with an improved SNR. Additional processors may determine the structure of the remote target.

Abstract: Unwanted signal components in time-division multiplexed (TDM) systems may lead to crosstalk and noise if these pulses overlap with signal pulses from an interrogated sensor. The crosstalk and noise are dominated by interference between the signal pulses from the interrogated sensor and the unwanted signal components and can be greatly reduced by suppressing this interference signal. The unwanted signal components may include overlapping pulses originating from different sets of interrogation pulses (repetition periods). Modulating the phase or frequency between the repetition periods so that the unwanted interference signal does not appear at frequencies from which the phase of the interrogated sensor is demodulated suppresses this interference. Other unwanted signal components include leakage light during dark periods of the duty cycle of an interrogation signal.

Abstract: A method for determining a resonant frequency of an optically coupled resonator includes modulating an incident light and striking a laterally offset photodiode with the modulated incident light. An electric field is generated between the laterally offset photodiode and the resonator in response to the modulated incident light, and the resonator is driven with a driving component of the generated electric field. A reflected light from the resonator is sensed, and the resonant frequency of the resonator is determined based on the reflected light. A system for determining a resonant frequency of an optically coupled resonator and a method of sensing an applied stimulus are also disclosed.

Abstract: A chemical sensing probe comprises an optical fiber or may be mounted on an optical fiber. The probe has a chemically sensitive measuring material which exhibits a change in volume and/or a change in refractive index in the presence of a given chemical. The change in volume and/or refractive index gives a change in an optical path length through the probe which can be measured interferometrically.

Abstract: A Fourier Transform Spectrometer (“FTS”) system includes a Fizeau FTS having a plurality of sub-collecting elements, adjacent ones of which are separated by a gap distance, and at least one of which has an adjustable optical path. The FTS system further includes a Michelson FTS having an adjustable optical path. The FTS system further includes one or more processors configured to select spectral data collected by the Fizeau FTS corresponding to spatial frequencies for which the Fizeau FTS has a modulation transfer function (“MTF”) value above a first threshold level, to select spectral data collected by the Michelson FTS corresponding to spatial frequencies for which the Michelson FTS has a MTF value above a second threshold level, and to combine the selected spectral data from the Fizeau FTS with the selected spectral data from the Michelson FTS.

Abstract: Optical filters tunable for both center wavelength and bandwidth, having applications such as in astronomy, remote sensing, laser spectroscopy, and other laser-based sensing applications, using Michelson interferometers or Mach-Zehnder interferometers modified with Gires-Tournois interferometers (“GTIs”) are disclosed. A GTI nominally has unity magnitude reflectance as a function of wavelength and has a phase response based on its resonator characteristics. Replacing the end mirrors of a Michelson interferometer or the fold mirrors of a Mach-Zehnder interferometer with GTIs results in both high visibility throughput as well as the ability to tune the phase response characteristics to change the width of the bandpass/notch filters. A range of bandpass/bandreject optical filter modes, including a Fabry-Perot (“FP”) mode, a wideband, low-ripple FP mode, a narrowband notch/bandpass mode, and a wideband notch/bandpass mode, are all tunable and wavelength addressable.

Abstract: Device and method for wavefront measurement of an optical imaging system by means of phase-shifting interferometry, having a mask structure (6a) to be arranged on the object side, and/or a grating structure (7a) to be arranged on the image side. The object-side mask structure includes one or more one-dimensional mask structure patterns, and the image-side grating structure includes one or more two-dimensional grating structure patterns. Alternatively, conversely, the mask structure includes one or more two-dimensional patterns, and the grating structure includes one or more one-dimensional patterns.

Abstract: In general, in a first aspect, the invention features apparatus that include an interferometer having a main cavity and an auxiliary reference surface, the main cavity including a primary reference surface and a test surface. The interferometer is configured to direct a primary portion of input electromagnetic radiation to the main cavity and an auxiliary portion of the input electromagnetic radiation to reflect from the auxiliary reference surface, wherein a first portion of the primary portion in the main cavity reflects from the primary reference surface and a second portion of the primary portion in the main cavity reflects from the test surface. The interferometer is further configured to direct the electromagnetic radiation reflected from the test surface, the primary reference surface, and the auxiliary reference to a multi-element detector to interfere with one another to form an interference pattern.

Abstract: A wavefront interferometry system including: a wavefront interferometer that during operation combines a reference beam from a reference object and a measurement beam from a measurement object to generate a combined beam; and a processor system programmed to processes the combined beam to concurrently generate therefrom a control signal and information about the difference in wavefront profiles of the reference and measurement objects, wherein the control signal controls a system parameter so as to maintain an optical path length difference between a spot on the reference object and a corresponding spot on the measurement object at a constant value mod 2?.

Abstract: A phase shift interferometer (100) has an illuminating optical system (200) that emits a P-wave and an S-wave, a collimator lens (110), a reference half mirror (120), a pinhole plate (130) having a pinhole (131), and a phase shift interference fringe acquiring section (300) that allows an object light and a reference light contained in the light beam passed through the pinhole (131) interfere with each other in four different phases to acquire interference fringes with different phases. In the S-wave, only the reference light (SR) reflected by the reference half mirror (120) is passed through the pinhole (131), and the object light (SM) reflected by a surface-to-be-measured is blocked by the pinhole plate (130). In the P-wave, only the object light (PM) reflected by the surface-to-be-measured is passed through the pinhole (131), and the reference light (PR) reflected by the reference half mirror (120) is blocked by the pinhole plate (130).