Abstract: Apparatus for splitting, imaging, and measuring wavefronts with a reference wavefront and an object wavefront. A wavefront-combining element receives and combines into a combined wavefront an object wavefront from an object and a reference wavefront. A wavefront-splitting element splits the combined wavefront into a plurality of sub-wavefronts in such a way that each of the sub-wavefronts is substantially contiguous with at least one other sub-wavefront. The wavefront-splitting element may shift the relative phase between the reference wavefront and the object wavefront of the sub-wavefronts to yield a respective plurality of phase-shifted sub-wavefronts. The wavefront-splitting element may then interfering the reference and object wavefronts of the phase-shifted sub-wavefronts to yield a respective plurality of phase-shifted interferograms. An imaging element receives and images the phase-shifted interferograms.

Abstract: A method (1) creates charge carriers in a concentration that changes in a periodic manner (also called “modulation”) only with respect to time, and (2) determines the number of charge carriers created in the carrier creation region by measuring an interference signal obtained by interference between a reference beam and a portion of a probe beam that is reflected by charge carriers at various depths of the semiconductor material, and comparing the measurement with corresponding values obtained by simulation (e.g. in graphs of such measurements for different junction depths). Various properties of the reflected portion of the probe beam (such as power and phase) are functions of the depth at which the reflection occurs, and can be measured to determine the depth of the junction, and the profile of active dopants.

Abstract: The disclosure relates to measuring devices that are particularly suited for the purpose of in-situ characterization of particles present in fluid substances or in air using a low-coherence interferometer. Specifically, the characterization includes average size, size distribution, volumetric density, and composition. The low-coherence interferometer utilizes a split band of radiation to illuminate a sample probe and a reference probe then combines the reflected radiation from both probes to determine the photon pathlength distribution of the tested particulate or colloidal containing stream and from this information determine the size characteristics of said stream. The methodology is relevant to possible spatially distributed control of chemical processes such as emulsion polymerization to produce paints, coatings, synthetic rubbers, or crystallization processes in pharmaceuticals, food, and bulk chemicals industries.

Abstract: The present invention features an anamorphic apparatus that alters a wavefront of a beam having a wavefront error to form a beam comprising a region having a greatly reduced wavefront error. A beam stop may be used with the anamorphic apparatus to define a portion of the region having a greatly reduced wavefront error that is subsequently detected or launched into a fiber optic. Furthermore, the anamorphic apparatus can be incorporated into an interferometry system to reduce errors associated with wavefront error and beam shear, i.e., non-cyclic non-linearities.

Abstract: The present invention provides a method and apparatus for monitoring optical signals with an expanded frequency resolution. The invention permits high-resolution measurements of optical signal spectrums while retaining wide bandwidth operation through appropriate control circuitry. An interferometer having a periodic frequency response formed of equally spaced narrow-band peaks is used to sweep the entire signal spectrum. The interferometer frequency response is incrementally tuned in cycles so that each of its frequency response peaks cyclically scans a particular spectral band of the signal spectrum. During each cycle, the interferometer isolates multiple spectrally resolved portions of the optical signal spectrum where each portion originates from a different spectral band. In this way, a high-resolution measurement of the entire signal spectrum can be obtained. The invention may be network protocol independent and can be incorporated into an optical spectrum analyzer or directly into any optical terminal.

Abstract: A test plate (1) is equipped with simulations (3) of components in an automatic equipping unit. The simulations comprise defined markings (4). The test plate is provided with local reference marks (5) having high positional precision in the proximity of the markings (4). A printed circuit board camera of the automatic equipping unit serving as topically resolving sensor is successively moved over the markings (4) and reference marks (5). A marking (4) and a reference mark (5) thereby respectively lie in the scan field (6) of the camera. As a result thereof, it is possible to acquire the relative position of the marking (4) relative to the reference mark (5) without thereby having to move the camera, the measuring outlay being reduced as a result thereof.

Abstract: The present invention detects ultrasonic displacements includes a detection laser to generate a first pulsed laser beam to detect the ultrasonic surface displacements on a surface of the target. Collection optics to collect phase modulated light from the first pulsed laser beam either reflected or scattered by the target. An optical amplifier which amplifies the phase modulated light collected by the collection optics. An interferometer which processes the phase modulated light and generate at least one output signal. A processor that processes the at least one output signal to obtain data representative of the ultrasonic surface displacement at the target.

Abstract: This device comprises a device (DD) for demultiplexing these lines in terms of wavelength, a device (DM) for measuring, by filtering, the wavelengths of the demultiplexed lines, comprising, for each of these lines, a measuring channel (VM) provided with a filter and a reference channel (VR), and means (MP) for the photodetection, for each line, of the light intensity transmitted by the corresponding measuring and reference channels. The wavelength of each of these lines is determined by calculating the ratio of the intensities thus detected. Application to the monitoring of structures.

Abstract: The present invention for detecting ultrasonic displacements includes a detection laser to generate a first pulsed laser beam to generate the ultrasonic surface displacements on a surface of the target. A second pulsed laser beam to detect the ultrasonic surface displacements on a surface of the target. Collection optics to collect phase modulated light from the first pulsed laser beam either reflected or scattered by the target. An interferometer which processes the phase modulated light and generate at least one output signal. A processor that processes the at least one output signal to obtain data representative of the ultrasonic surface displacements at the target.

Abstract: An uncorrelated Michelson interferometer is formed with single mode optical fiber. In a first embodiment, light is transmitted into an optical 3 dB coupler, and split into a transmission down a first optical fiber and transmission down a second, significantly longer second optical fiber. In the disclosed embodiment, the second optical fiber path may be several meters, and even hundreds of meters longer than that of the first fiber optic path. The light at the ends of the respective first and second fiber optic paths is reflected back into the single mode optical fiber, and coupled in the optical coupler. In the first embodiment, since the second fiber optic is relatively long, an unknown amount of rotation of the polarization would otherwise occur. Thus, a polarization controller is used to control the polarization in the longer, second optical fiber such that a maximum signal is output from the optical coupler.

Abstract: A spectral image input device has an image forming optical system for forming an image of image light on an image forming surface and a phase difference generating unit disposed anterior to the image forming surface in the direction of image light travel. The phase difference generating unit constitutes, sequentially in the direction of image light travel, a polarizer for transmitting only polarized light in a specific direction, an optical element formed of a solid material having a birefringence, and arranged such that the principal refraction index axis is inclined 45° relative to the polarization angle of the analyzer, the optical element generating a phase difference in accordance with the wavelength of the image light based on the difference in the physical thickness of the optical element in the direction of image light travel and an analyzer for transmitting only the image light of a polarization angle of 90° relative to the direction of the polarized light of the polarizer.

Abstract: An apparatus for exposing a pattern, formed on a mask, on each of a plurality of partitioned areas on a photosensitive substrate by a step-and-repeat scheme includes a projection optical system for projecting the pattern of the mask on the photosensitive substrate, a substrate stage for holding the photosensitive substrate and two-dimensionally moving the photosensitive substrate within a plane perpendicular to the optical axis of the projection optical system, a detection unit for projecting a pattern image having a predetermined shape on the photosensitive substrate and photoelectrically detecting light reflected by the photosensitive substrate to detect a position at each of a plurality of points on the photosensitive substrate along the optical axis of the projection optical system, and a measurement unit for, when each of a plurality of measurement points in a partitioned area on which a pattern of the mask is to be exposed next coincides with or approaches the pattern image, detecting an offset amount b

Abstract: Methods and systems for evaluating stresses in line features formed on substrates. Stresses may be computed from measured curvature information based on simple analytical functions. The curvature information can be obtained optically by, e.g., a coherent gradient sensing method, to obtain a full-field measurement of an illuminated area.

Abstract: A wavelength reference device for tuning a tunable Fabry-Perot filter and/or a tunable VCSEL to a desired frequency, where the device uses a Fizeau interferometer and a position sensitive detector, with the position sensitive detector being used to measure the location of the maximum reflected power from the interferometer, whereby to determine the wavelength of laser radiation for tuning the device.

Abstract: An interferometric optical torque sensor senses the torque transmitted by a rotating shaft without requiring physical contact with the shaft. A diffraction grating is provided on the shaft with its grating lines parallel to the longitudinal dimension of the shaft. A laser beam is split in two and reflected from two axially-separated points of the grating. As the shaft twists, the phase of the light in the diffracted orders of the light reflected from the grating changes. By superimposing the diffracted beams an interference pattern is created. The motion of the interference fringes in this pattern is proportional to the twist, therefore the torque, in the shaft. The power transmitted by the shaft may be computed from the torque and shaft speed.

Abstract: Fringe counting in a Michelson type interferometer is carried out by detecting when the amplitude of the reference fringe attains a given value eg a zero crossing. Reversals in scan direction are recognized by monitoring parameters of the waveform such as amplitude and time occurence of successive half fringes and identifying a reversal by the occurrence of a particular sequence or state of the monitored parameters.

Abstract: An optical wavelength division multiplexed system uses wavelength splitters to split channels included in input light into different paths within the system. Odd-numbered channels are split into one path, and even-numbered channels are split into another path, providing increased isolation between channels. Using filters, the system then drops one or more of the isolated, split channels into paths referred to as dropped paths and allows the remaining channels to continue through the filters into output paths. The dropped paths are then combined into one, common dropped path, and the output paths are also combined into one, common output path.

Abstract: Apparatus for splitting, imaging, and measuring wavefronts with a reference wavefront and an object wavefront. A wavefront-combining element receives and combines into a combined wavefront an object wavefront from an object and a reference wavefront. A wavefront-splitting element splits the combined wavefront into a plurality of sub-wavefronts in such a way that each of the sub-wavefronts is substantially contiguous with at least one other sub-wavefront. The wavefront-splitting element may shift the relative phase between the reference wavefront and the object wavefront of the sub-wavefronts to yield a respective plurality of phase-shifted sub-wavefronts. The wavefront-splitting element may then interfering the reference and object wavefronts of the phase-shifted sub-wavefronts to yield a respective plurality of phase-shifted interferograms. An imaging element receives and images the phase-shifted interferograms.

Abstract: The gauge length of an acoustic signal detector is dynamically variable by adjusting the location of an induced light reflection interface within a section of optical waveguide to which an acoustic stimulus is coupled. In an interferometer based architecture, a light beam is applied to each of an ‘acoustic signal detection’ optical waveguide and a ‘reference’ optical waveguide. The ‘acoustic signal detection’ waveguide is coupled to an acoustic energy transmission element. The acoustic input modifies the index of refraction of the optical waveguide and modulates the light passing through the waveguide. Since the index of refraction of the optical waveguide section is modified by the acoustic stimulus, the signal beam has a phase delay dependent upon the acoustic signal and the distance between one end of the signal waveguide section and an induced reflection interface.

Abstract: A blood vessel imaging system includes a measuring light source which emits a measuring light beam. An optical heterodyne detection system consists of an optical system which splits the measuring light beam into a first light beam traveling to impinge upon an organism and a second light beam traveling not to impinge upon the organism and combines the second light beam with the first beam emanating from the organism into a combined light beam, a frequency shifter which causes the first and second light beams to have frequencies different from each other, and a beat component detector which detects beat components of the combined light beam. An image signal is generated on the basis of the ratio of the intensity of a pulsation wave band signal to the intensity of a beat signal included in an output signal of the optical heterodyne detection system.