Abstract:
Fast on-line electro-optical detection of wafer defects by illuminating with a short light pulse from a repetitively pulsed laser, a section of the wafer while it is moved across the field of view of an imaging system, and imaging the moving wafer onto a focal plane assembly, optically forming a continuous surface of photo-detectors at the focal plane of the optical imaging system. The continuously moving wafer is illuminated by a laser pulse of duration significantly shorter than the pixel dwell time, such that there is effectively no image smear during the wafer motion. The laser pulse has sufficient energy and brightness to impart the necessary illumination to each sequentially inspected field of view required for creating an image of the inspected wafer die. A novel fiber optical illumination delivery system, which is effective in reducing the effects of source coherence is described. Other novel aspects of the system include a system for compensating for variations in the pulse energy of a Q-switched laser output, methods for autofocussing of the wafer imaging system, and novel methods for removal of repetitive features of the image by means of Fourier plane filtering, to enable easier detection of wafer defects.
Abstract:
Computation-saving techniques and stability-adding techniques provide for fast, accurate reconstructions of a time series of images involving large-scale 3D problems, such as real-time image recovery in an optical tomography imaging system. A system equation for a target medium (116) such as tissue is solved using a Normalized Difference Method (NDM) (250). Because of the inherent stability of the NDM solutions, a weight matrix (W) of the system equation can be provided for a given point in a time series (220), then reused without recalculation at subsequent points. Further savings are achieved by decomposing W using singular value decomposition or direct matrix decomposition, transforming it to reduce its dimensions, and/or scaling it to achieve a more stable numerical solution. Values of measured energy (112) emerging from the target medium are back-substituted into the system equation for the different points to obtain the target medium properties.
Abstract:
Apparatus for detecting defects in a web of textile material as it is being drawn through an inspection zone. A header is arranged to project a line of light on the running web and a reflected light image from the web is sensed and analyzed for defects. The header includes a fiber bundle for producing a line of light and an optical element for collimating the light upon the web as it passes through the inspection zone.
Abstract:
A variable filter spectrophotometer, for use with sample and reference; has a main member, a filter unit, a drive, a detector, a light distribution system, and a clamping circuit. The main member defines first and second beam paths, which are intersected by the filter unit. The filter unit has filtering and opaque portions. The filter unit is continuously movable relative to the beam paths in a repeating cycle from a first filtering relation in which the filtering portion is interposed in the first beam path and the opaque portion completely blocks the second beam path, to a first dark relation in which both beam paths are blocked, to a second filtering relation in which the filtering portion is interposed in the second beam path and the first beam path is completely blocked, and to a second dark relation in which both beam paths are completely blocked. The filtering portion is variably transmissive along a direction of movement of the filter unit. The drive continuously moves the filter unit relative to the beam paths. The detector produces a signal responsive to light received. The light distribution system directs light separately to and from the sample and reference, to and from the beam paths, and to the detector. The clamping circuit clamps the signal produced by the detector during the filtering relations to the signal produced by the detector during the dark relations.
Abstract:
Optical analytical instruments to determine a physical parameter of a fluid, and methods of operation of such instruments, are shown. These employ a source of suitable optical radiation, a detector means, means defining a zone for the fluid, means defining an optical path from the radiation source through the fluid zone to the detector means, and reading and control circuitry. At least two readings of optical energy that has been influenced by the fluid are taken without there having occurred substantial change to the fluid. During one of the readings a filter of known absorbance is included in the optical path so that the respective reading represents a calibration reading. A calibration-value-determining means is constructed first to compare, effectively, the two readings to remove the effect of the fluid from the value of the calibration reading, second, to compare, effectively the residual value of the calibration reading to a known value based on the known absorbance of the filter, and, third, on the basis of the second comparison, to make a calibration adjustment based on values derived while the fluid sample remained unchanged in the fluid zone. Novel software implementations of the determinations are shown. Specific examples of instruments and methods implementing these features shown are a dual lamp, no-moving part in-line spectrophotometer, a no-moving part reflection colorimeter capable of on-line or off-line operation, a scatter or fluorescence detecting implementation and a turbidimeter.
Abstract:
Measurements of physical attributes such as dielectric film thickness that are susceptible to spectral analysis are accomplished rapidly and accurately by a spectrophotometric system in which a programmed digital computer operating concurrently with the optical scanning means automatically performs the calibrating, normalizing and data reducing functions that otherwise must be carried out as time-consuming human, mechanical or analog electronic operations. The control over the optical data handling operations exercised by the computer eliminates the need for mechanically or electronically adjusting the optical apparatus to meet changing system conditions, whether periodic or aperiodic. Source light is transmitted through a rotating variable-wavelength interference filter which acts during one-half of its cycle to transmit light of varying wavelength through a fiber-optic reference path directly to the optical data acquisition apparatus, while acting in the next half-cycle to transmit light of such varying wavelength indirectly to said data acquisition apparatus through a measurement path. In the present example, where film thickness is the attribute being measured, the measurement path comprises a bifurcated fiber-optic bundle, one branch of which is used to carry the light of variable wavelength to the sample, and the other branch of which carries light reflected from the sample to the aforesaid data acquisition apparatus. A computer program enables light passed through the reference path in one half-cyle to calibrate the system for measuring optical transmission or reflectance in the next half-cycle. Reduction of relative reflectance data to absolute reflectance data (needed for the accurate determination of film thickness) is accomplished by additional computer programs whose algorithms are based upon the discovery that all graphs of absolute reflectance versus wavelength for film samples of a given material having different thicknesses are bounded by a common pair of wave envelopes.
Abstract:
A distributed gas detection system includes solid core fibers, hollow core fibers, and an interrogator device. The solid core fibers are configured to receive light of one or more wavelengths from a light source. The hollow core fibers are disposed in different locations. Each of the hollow core fibers is optically coupled with a different corresponding one of the solid core fibers and configured to receive at least some of the light transmitted through the corresponding solid core fiber. The interrogator device is configured to receive at least some of the light propagating through the solid core fibers and the hollow core fibers. The interrogator device is configured to identify a location of a presence of a gas-of-interest by examining absorption of at least one of the wavelengths of the light in at least one of the hollow core fibers.
Abstract:
The present invention relates to an apparatus for measuring the absorbance of a substance in a solution, comprising at least one sample cell arranged to contain said solution that is at least partially transparent to light of a predefined wavelength spectrum, at least two light passages through said at least one sample cell, each of said light passages having a known path length,an LED light source arrangement comprising at least two LEDs, each arranged to emit a light output with a wavelength within said predefined wavelength spectrum,wherein a plurality of optical fibers, one for each light passage, is arranged at each LED for receiving said light output and guiding it to the light passages. The invention also relates to a method for measuring the absorbance of a substance in a solution.
Abstract:
The present invention provides a method and system for identification and isolation of cells from tissues using optical spectroscopy. The method includes accessing the cells using an access corridor, measuring the cells using optical spectroscopy, comparing the spectra of the cells to signature spectra, using the comparison to identify the cells and removing the cells into a container. The system includes an access corridor, a probe for measuring the cells, a resection tool, a collection tube and a collection container.
Abstract:
The invention relates to a method for quantification of the amount of impurities in lactide. Said method is characterized in that the quantification of the impurities is based on measurements performed on absorptions in the near Infra-Red region of the electromagnetic spectrum. With this method, small amounts of impurities like water, free-acid species or both can be determined online in a reaction mixture of lactide in a relatively simple manner. This allows a simple online monitoring of the production process of lactide.