Abstract: Improvements to the acquisition and replay systems for direct-to-digital holography and holovision are described. A method of recording an off-axis hologram includes: splitting a laser beam into an object beam and a reference beam; reflecting the reference beam from a reference beam mirror; reflecting the object beam from an illumination beamsplitter; passing the object beam through an objective lens; reflecting the object beam from an object; focusing the reference beam and the object beam at a focal plane of a digital recorder to form an off-axis hologram; digitally recording the off-axis hologram; and transforming the off-axis hologram in accordance with a Fourier transform to obtain a set of results. A method of writing an off-axis hologram includes: passing a laser beam through a spatial light modulator; and focusing the laser beam at a focal plane of a photorefractive crystal to impose a holographic diffraction grating pattern on the photorefractive crystal.

Abstract: Disclosed are first and second embodiments of a 3-channel probe-plate structure of the fiber-optic interferometer, wherein low-coherent-length light from a superluminescent light-emitting diode is split by a tree splitter into three light branches which are coupled as separate light inputs to the probe-pate structure by single-mode, polarization-preserving optical fibers. For each of the 3 channels, the first embodiment of the probe-plate structure comprises an integrated polarizing lithium-niobate Y splitter-modulator for deriving separate reference-arm light and probe-arm light.

Abstract: An interferometer spectrometer that has reduced alignment sensitivity is described herein. Parallelism of an output ray pair formed by a single input ray is not affected by variations in relative alignment of the components. In comparison to other compensated interferometer designs, lateral separation errors in the output ray pair due to optical component misalignment are reduced. The reduced alignment sensitivity may be accomplished by utilizing simple planar components that are common to both light paths. The reduced alignment sensitivity and simplicity in design provides a more compact and more robust interferometer, with reduced manufacturing costs associated therewith. An elliptical field of view light source that utilizes an array of collimator lenses is also described. The light source provides a more compact design than a single circular collimator lens of the same area, and is suitable for single channel or multi-channel use.

Abstract: The present invention provides a method and apparatus for monitoring optical signals with an expand 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 frog 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: An improved interferometric modulator permits the reduction in size of optical transmitters. In one embodiment, the optical modulator includes amplifiers or attentuators as phase modulators. In another embodiment, two outputs from a combiner are fed to the modulator, thus avoiding the requirement for an input splitter in the modulator. Light passing through the modulator may be both phase-shifted and amplified or attenuated by optical regulator sections located in the modulator. In another embodiment, the transmitter is included as a multiple-wavelength optical communications source, where individual current sources are provided to actuate a number of light sources feeding into the combiner, a processor controls the operation of each light source, and a modulator driver receives a data input signal to be encoded on the output of the source. By combining a number of modulators, a gray scale modulator may be fabricated for producing a gray scale output, rather than a conventional binary level output.

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: Emitted light from a light source 1 is separated into two parts through an optical fiber coupler 2, one is entered in a measured optical module 3 as measurement light, and the other is given a group delay by means of an optical fiber delay line 5, a reflector 25, etc., as local light signal, then the local light signal is combined with reflected light signal from the measured optical module 3 through an optical fiber coupler 21 and the reflected light signal and the local light signal are caused to interfere with each other. A polarization controller 100 comprising a polarizer and a polarization rotation device for arbitrarily rotating the polarization state 0 degrees and 90 degrees at the time is used to generate beat signals at the polarization rotation angles, and the sum of the intensities of the beat signals is found, making it possible to measure the light power of the reflected light signal regardless of the polarization state of the local light signal or reflected light signal.

Abstract: A laser wavelength meter determines the unknown wavelength of a laser by measuring the phase difference between two orthogonally polarized beams derived from the laser. The orthlogonally polarized beams propagaic along two optical paths of different length as defined, for example, by a polarizing beam splitter or a stepped reflector with a defined step height. An in situ reference laser of known wavelength allows calculation and monitoring of the path difference between the two optical paths.

Abstract: A scanning exposure apparatus has a wafer stage, a reticle stage, a projection optical system for projecting an image of a reticle onto a substrate on the wafer stage, X-Y laser interferometers for measuring the position of the wafer stage in the X direction, Z interferometers for measuring the wafer stage position in the Z direction, and X-Y laser interferometers for measuring the position of the reticle stage in the X and Y directions, and transfers the image of the reticle onto the wafer by exposure while synchronously driving the wafer stage and reticle stage. The exposure apparatus includes a plurality of laser heads for generating laser beams to be provided to the interferometers. A reference signal is supplied from one laser head to the remaining laser heads to synchronize all laser heads.

Abstract: Optical components, particularly microoptic glass components used in synthesizing birefringence in filter systems based on polarization interferometer techniques, are fabricated using systems and methods which provide accurate frequency periodicity measurements. These measurements are derived from differential delays induced by in-process glass elements between beam components in a polarization interferometer unit and from progressive wavelength scanning across a wavelength band of interest. The consequent sinusoidal output variation has peak to peak spacings which are measured to provide frequency periodicity values from which precise length corrections for the optical elements can be calculated.

Abstract: A moiré interferometer has an illumination system and an imaging system that share a common focusing optic, which preferably takes the form of a concave mirror. Within the illumination system, the common focusing optic collimates light en route to a test surface. Within the imaging system, the common focusing optic telecentrically images a grating pattern appearing on the test surface onto a fringe pattern detector.

Abstract: A signal/vibration detecting technique employs a simple structure to identify a target optical fiber among many and carry out a bidirectional conversation through the target optical fiber. First ends of optical fibers (202A, 202B), one of which is a target optical fiber, are connected to an optical transceiver (201). Second ends of the optical fibers are connected to each other to form a loop. A local unit (203) is installed at the loop. The local unit vibrates the loop, and the optical transceiver emits lights so that the lights are oppositely propagated through the loop. The propagated lights are coupled together so that they interfere with each other. In the intensity of the interfering lights, a change corresponding to the vibration is detected to identify the target optical fiber. Once the target optical fiber is identified, it is used to carry out a conversation between the optical transceiver and the local unit.

Abstract: A polarization-insensitive fiber-optic interferometric sensor system has an erbium-doped fiber amplifier (EDFA) at a location between a light source and a sensing array to serve as a post amplifier. An output end of the sensing array is coupled to another EDFA, and further coupled to a receiver, in which this another EDFA is used as an in-line amplifier. As the sensor system is applied for a light source with multiple wavelengths, a dense wavelength division multiplexers (DWDMs) is used to combine the multiple wavelengths into one for amplification, and another DWDM is used to decouple the multiple wavelengths.

Abstract: A code reading device includes an illuminator which illuminates a code formed on a substrate with light, a reflector which reflects the light to allow the light to pass through the code at least two times, and a detector which detects the reflected light to read the code on the substrate. The substrate is one of a photomask, a reticle, a wafer and a glass plate.

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: A measuring system for measuring the accuracy of the position and track of a machine element moved along a predetermined track. The system includes a predetermined track along which a machine element moves relative thereto and a measuring device for measuring the position of the machine element along the track. The track has a guide of the measuring device, on which a carriage is guided along the track, wherein the machine element can be fastened to the carriage. A component of the measuring device is fastened on the carriage and a drive integrated with the measuring device moves the carriage in a controlled manner along the guide into predetermined positions and at predetermined speeds.

Abstract: A fiber optic switch based on a Mach-Zender type interferometer comprises first and second input optical fibers, first and second intermediate optical fiber segments, and first and second output optical fibers. The switch selectively couples the first and second input fibers either to the first and second output fibers, respectively, or to the second and first output fibers, respectively. To operate the switch, an optical path length of the first intermediate fiber segment is changed, and an optical path length of the second intermediate fiber segment is altered by an equal and opposite amount. Heat is therefore deposited equally in each of the intermediate fiber segments. The intermediate fiber segments lie substantially in a plane, thereby ensuring that the polarization of light traveling through the first intermediate fiber segment does not rotate significantly relative to the polarization of light traveling through the second intermediate fiber segment.

Abstract: A method of spectroscopically analyzing amplitude and phase information of a particular sample (510) is disclosed, comprising providing a femtosecond laser source (502) positioned in an angularly distal relationship to the sample, generating from the laser source a primary light pulse (504) of substantial peak intensity and spectral bandwidth directed at the sample, and providing a reference medium (512) interposed between the light source and the sample, fixed in position with respect to the sample. A portion of the primary light pulse is directed through the reference medium generating a reference second harmonic signal (514) directed at the sample, which propagates collinearly with the primary light pulse towards the sample. A spectrometer (520) is provided, positioned in an angularly distal relationship to the sample and opposing the laser source, to receive second harmonic reflections of the primary pulse and reference signal (516 and 514, respectively) from said sample.

Abstract: A method for monitoring a device fabrication process. The method includes etching into a wafer disposed inside a chamber and detecting the intensity of a portion of a light reflected from a surface of the wafer and further scattered at a scattering inside surface of the chamber.

Abstract: An improved interferometric modulator permits the reduction in size of optical transmitters. In one embodiment, the optical modulator includes amplifiers or attentuators as phase modulators. In another embodiment, two outputs from a combiner are fed to the modulator, thus avoiding the requirement for an input splitter in the modulator. Light passing through the modulator may be both phase-shifted and amplified or attenuated by optical regulator sections located in the modulator. In another embodiment, the transmitter is included as a multiple-wavelength optical communications source, where individual current sources are provided to actuate a number of light sources feeding into the combiner, a processor controls the operation of each light source, and a modulator driver receives a data input signal to be encoded on the output of the source. By combining a number of modulators, a gray scale modulator may be fabricated for producing a gray scale output, rather than a conventional binary level output.