Abstract: A sensor comprises an optical modulator that generates a modulation signal, an interferometer that mixes an acoustic signal evoked by a pulsed laser with the modulation signal to down-convert the acoustic signal to lower frequencies, and a photodetector that detects the down-converted signal.

Abstract: The present invention generally relates to a method and system for determining the position and alignment of a plane in relation to an intersecting axis and using that known position and alignment to allow for corrections to be made when using the plane as a reference plane. More particularly, the invention relates to a method and system for determining the angle of tilt of a planar surface in relation to a laser beam, and using the determined angle of tilt to calculate a correction factor to be applied to the laser beam. Briefly stated, the method and system ultimately calculates a correction factor, z-offset, that is applied when using the laser beam in a procedure.

Abstract: A method including: imaging test light emerging from a test object over a range of angles to interfere with reference light on a detector, wherein the test and reference light are derived from a common source; for each of the angles, simultaneously varying an optical path length difference from the source to the detector between interfering portions of the test and reference light at a rate that depends on the angle at which the test light emerges from the test object; and determining an angle-dependence of an optical property of the test object based on the interference between the test and reference light as the optical path length difference is varied for each of the angles.

Abstract: Novel spectroscopy techniques using entangled photons are disclosed. In one technique, entangled photons are directed to a sample of interest, while the photons with which they are entangled are resolved according to frequency. The photons transmitted by or reflected from the sample and the frequency-resolved photons are detected. Such detection may be by way of an electronic coincidence counter or a biphoton sensitive material, which absorbs entangled photons while allowing other photon pairs to pass. Detection information is used to derive spectroscopic properties of the sample. In another technique, a Fourier transform spectroscopy technique using entangled photons is disclosed. Entangled photons are directed to a sample, while the photons with which they are entangled are directed to a Michelson interferometer. The photons transmitted by or reflected from the sample and the photons leaving the Michelson interferometer are detected.

Abstract: A method and apparatus using two sets of polarized light detection systems are disclosed for optically measuring absolute displacement. In the first detection system a step motor is controlled to drive an analyzer to trace synchronously the displacement being measured by comparison of the magnitude of the intensity of two orthogonal light beams and then the number of control pulses from the step motor becomes a value of the displacement measured; and by comparison with the magnitude the intensity of a plurality of light beams with phase difference from a plurality of light paths in the second polarized light detection system the section of system operation is ascertain and consequently the absolute displacement is detected and measured.

Abstract: A wavefront measurement system includes a source of electromagnetic radiation. An imaging system directs the electromagnetic radiation at an object plane that it uniformly illuminates. A first grating is positioned in the object plane to condition the radiation entering the input of a projection optic. A projection optical system projects an image of the first grating onto the focal plane. A second grating is positioned at the focal plane that receives a diffracted image of the object plane to form a shearing interferometer. A CCD detector receives the image of the pupil of the projection optical system through the projection optical system and the second grating that forms a fringe pattern if there are aberrations in the projection optical system. Phaseshift readout of fringe pattern can be accomplished by stepping the first grating in a lateral direction and reading each frame with the CCD detector.

Abstract: A laser ultrasonic inspection apparatus and method which enables remote sensing of thickness, hardness, temperature and/or internal defect detection is disclosed. A laser generator impinges a workpiece with light for generating a thermo-elastic acoustic reaction in a workpiece. A probe laser impinges the workpiece with an annularly-shaped probe light for interaction with the acoustic signal in the workpiece resulting in a modulated return beam. A photodetector having a sensitive region for detecting an annularly-shaped fringe pattern generated by an interaction of a reference signal and with the modulated return beam at said sensitive region.

Abstract: A method for measuring scene inhomogeneity includes directing radiance of a scene into an interferometer; and oscillating a field-of-view (FOV) of the interferometer, while directing the radiance of the scene into the interferometer. A Fourier transform of signals emerging from the interferometer is obtained with magnitude values of the Fourier transform as a function of wavelength. The magnitude values are separated into (1) component values occurring within a predetermined wavelength band of the interferometer and (2) a component value occurring outside the predetermined wavelength band. The component value occurring outside the predetermined wavelength band is used to measure scene inhomogeneity.

Abstract: An apparatus for sensing data from a remote optical sensor 16 has its frequency stabilised by balancing the outputs of narrow band filter 28 30, spaced about a desired frequency 36 positioned at about the 3 db down points 40 of a broad band light source 10 using voltage control, current control or temperature control to vary the frequency of the wide band light source 10. Difference between the outputs through the two narrow band filters 28 30 can be used to drive an amplifier 48 to correct the frequency of the broad band light source. The outputs through the two narrow band filters 28 30 can be converted 52 to binary numbers and fed to a microprocessor 56 which is used, via analog conversion 60, to drive the amplifier 48. The broad band light source 10 can be pulse modulated 68 to provide temporally separate light pulses 92 94 through each of the narrow band filters 28 30, measured at separate times.

Abstract: An optical system is presented for use in a measurement system (100) for use in measurements of thin films of a workpiece (W), the system comprising an optical assembly (14), comprising illuminator assembly, a detector assembly, and a light directing assembly (FA-OF) for directing illuminating light to a plurality of measurement sites in the workpiece (W) arranged in an array of substantially concentric ring-like regions, such that an area defined by the measurement sites within one of the substantially concentric ring-like regions is substantially equal to that of the other substantially concentric ring-like region.

Abstract: To provide an optical image measuring apparatus capable of calculating an intensity of a direct current component composed of background light based on a result obtained by detection of interference light and obtaining a signal intensity of the interference light using the calculated intensity. The apparatus includes: an optical interference system to divide a light beam into signal light and reference light, and the signal light propagating through an object to be measured and the reference light are superimposed to produce interference light; beam splitters for dividing it into three interference light beams; shutters to perform sampling; photo detectors for detecting the sampled interference light beams and converting them into electrical signals; and a signal processing portion for calculating the signal intensity of the interference light and the spatial phase distribution thereof based on the electrical signals.

Abstract: A method of detecting contaminants on a window surface of a viewing system comprises the steps of: reflecting light off of contaminants on the window surface; capturing the reflected light in an image; converting the image into image data; and processing the image data to detect the contaminants on the window surface. Also, apparatus for detecting contaminants on an external surface of a window of a viewing system comprises: at least one light source for reflecting light from contaminants on the external surface; an imager for capturing an image of the reflected light and converting the image into image data; and a processor for processing the image data to detect the contaminants on the external surface.

Abstract: Embodiments of the present invention generally provide methods, apparatus, and systems for compensating for frequency fluctuations in source light used to interrogate an optical sensor. The optical sensor may be interrogated to generate a sensor signal. A reference device co-located with the optical sensor may also be interrogated to generate a reference signal. Optical parameters extracted from the reference signal may be used to correct parameters extracted from a sensor signal.

Abstract: The embodiments disclosed herein generally relate to identifying and removing background noise in spectroscopic imaging of a sample. Because white-light has essentially constant intensity at every wavelength, background noise caused by white light can be identified and removed from spectroscopic measurements including Raman spectroscopy. Thus, once the Raman spectrum for a sample is obtained, it may be corrected to remove the white-light dispersive spectrum in accordance with the embodiments disclosed herein.

Abstract: A method of determining the rate of change of optical thickness of a thin-film during deposition comprising the steps of illuminating the thin-film (5) with electromagnetic radiation (3) having a range of wavelengths, measuring the transmission spectrum (6,7) of the thin-film (5) at least twice during the deposition process to determine the wavelength ?t or turning points in the transmission spectrum, and using the measurements to determine the rate to change of optical thickness of the thin-film as a function of time. The method further comprises the steps of predicting a time T in the growth process at which the wavelength ?t of the turning point in the transmission spectrum of the thin-film will be substantially equal to the wavelength ?d of the turning point in the transmission spectrum of thin-film at its optical design thickness, and interrupting the growth process such that growth ceases at time T.

Abstract: A high-speed optical delay generating method by a rotation reflector in optical coherence tomography, capable of providing a sectional picture with a sufficiently long depth-direction (Z direction) scanning distance, and an optical coherence tomography device therefor are provided. The device comprises a low-coherence light source (1), a half mirror (2) for splitting light from the low-coherence light source (1) into two, that is, into object light towards an object (A) to be examined and reference light, a light delay mechanism (3) for delaying the reference light by means of a rotation reflector (12), a fixed mirror (4) for reflecting/returning the reference light from the light delay mechanism (3), the half-mirror (2) for combining the object light returning from the object (A) to be examined with the reference light returning from the light delay mechanism, and a light detector (11) for detecting interference light including a heterodyne interference beat signal combined at the half mirror (2).

Abstract: A system and method for coherent optical inspection are described. In one embodiment, an illuminating beam illuminates a sample, such as a semiconductor wafer, to generate a reflected beam. A reference beam then interferes with the reflected beam to generate an interference pattern at a detector, which records the interference pattern. The interference pattern may then be compared with a comparison image to determine differences between the interference pattern and the comparison image. According to another aspect, the phase difference between the reference beam and the reflected beam may be adjusted to enhance signal contrast. Another embodiment provides for using differential interference techniques to suppress a regular pattern in the sample.

Abstract: There is described an improved Surface Reflectance Instrument which achieves more complete detection of surface defects in the nature of small particles. One of the improvements is the use of an elliptical integrated cavity with internal surface mirrors, and another the use of a position sensing diode as the detector for the scattered light. Other improvements and the use of a stable laser at a particular wavelength resulting in greater detection are also described.

Abstract: An apparatus and method for measuring by the Schlieren technique light beam deviations generated by a sample (EV) includes a source (S) of light beam for illuminating the sample (EV) therewith so as to have a transmitted beam. An imaging means is provided (L2, L3) for forming an image of the sample from the transmitted beam. A filtering means acts as a Schlieren filter (SF) for obtaining “Schlieren fringes” from the image. The Schlieren filter (SF) comprises a periodic structure (SFP) of a defined period. A detecting means (CCD) is provided for detecting the Schlieren fringes under operating conditions.

Abstract: A target detection apparatus is provided which can detect and quantitatively measure various detection targets such as pathogens. For this purpose, the apparatus comprises an optical irradiation unit which irradiates light; an optical interference unit which can interact with the detection target, interferes with the light irradiated from the optical irradiation unit and radiates it as interference light and change the wavelength of the interference light after interaction with the detection target; and an wavelength change detecting unit which detects the wavelength change of the interference light radiated by the optical interference unit. The wavelength change detecting unit preferably measures spectrums before and after wavelength change of the interference light, and their differential spectrum. Also provided is a target detection substrate comprising a film-like material on a substrate which, when interacting with a detection target, changes the wavelength of the interference light.