Abstract:
A method and apparatus for improving contrast in prism coupling measurements of waveguide mode spectra, wherein the measured waveguide sample has a surface region of rapidly decreasing index, characterized with normalized slope >0.0004. An opaque light-blocking element is placed in the portion of the light beam closest to the plane of the contact between prism and measured sample, on the input side, output side or both sides of the prism. The light blocking element prevents light from the light source to reach a portion of the length of the prism-sample coupling interface along the optical path, prevents light reflected from a portion of the aforementioned length to reach the detector, or both when input and output light-blocking elements are used.
Abstract:
Gezeigt werden eine Vorrichtung (26) und ein Verfahren zur Detektion der Auslenkung einer Mehrzahl elastischer Elemente (22), wobei die elastischen Elemente (22) gegen eine Rückstellkraft aus einer Ruhelage auslenkbar sind und als Resonatoren und/oder zur Messung einer auf ein jeweiliges elastisches Element (22) wirkenden Kraft geeignet sind. Die elastischen Elemente (22) sind periodisch angeordnet. Die Anordnung der elastischen Elemente (22) wird mit Licht beleuchtet, dessen Kohärenzlänge größer ist als der mittlere Abstand benachbarter elastischer Elemente (22). Hierdurch wird ein Beugungsbild des an der Anordnung von elastischen Elementen (22) gestreuten Beleuchtungslichtes erzeugt, und zumindest ein Teil des Beugungsbildes wird direkt oder nach Wechselwirkung mit weiteren optischen Komponenten von einem optischen Sensor (32) detektiert. Das detektierte Bild oder Bildsignal wird anschließend weiter analysiert, um daraus Informationen bezüglich des Auslenkungszustandes der elastischen Elemente (22) zu ermitteln.
Abstract:
According to one aspect, the invention provides an optical sensor for measuring a force distribution, comprising a substrate; one or more light emitting sources and one or more detectors provided on the substrate, the detectors responsive to the light emitted by the sources; wherein a deformable opto-mechanical layer is provided on said substrate with light responsive properties depending on a deformation of the opto-mechanical layer. The design of the sensor and particularly the use of optical components in a deformable layer make it possible to measure the contact force accurately. The sensor is scalable and adaptable to complex shapes. In one embodiment also a direction of the contact force can be determined.
Abstract:
An essentially thickness independent luminescent photoelastic coating consists of a single layer of a photoelastic material in which a polarizing preserving luminescent dye, (1), and an excitation absorption dye, (2), are contained therein. The absorption dye limits a penetration depth, (3), of incident radiation, (4). The thickness of the coating is greater than a penetration depth of the excitation radiation. The coating is used to determine strain on an underlying substrate, (5), on which the coating is adhered by measurement and analysis of the emission intensities and patterns from the luminescent dye in the coating upon irradiation at a distinct excitation radiation.
Abstract:
A reflective strain gauge includes an holographically-formed polymer dispersed liquid crystal (H-PDLC) film comprising layers of liquid crystal (LC) droplets in a matrix polymer, the H-PDLC film having a reflection or transmission grating capable of reflecting or transmitting light of a selected wavelength, and means for adhering the film to a surface of a workpiece for monitoring the strain at said surface. A change in the nature of the reflected light is an indication of strain. Also included is a polarizing material having an holographically-formed polymer dispersed liquid crystal (H-PDLC) film comprising layers of liquid crystal (LC) droplets in a matrix polymer, the H-PDLC film having a reflection grating capable of reflecting light of a selected wavelength, wherein the reflection grating of the H-PDLC film is oriented, such that the refractive index parallel to said axis of orientation (ne) is greater than the refractive index perpendicular to said axis no).
Abstract:
A structural specimen coated with or constructed of photoelastic material, when illuminated with circularly polarized light will, when stressed, reflect or transmit elliptically polarized light, the direction of the axes of the ellipse and variation of the elliptically polarized light from the illuminating lights corresponds to the direction and magnitude of shear stresses for each illuminated point. Stress analyzing apparatus may or may not use multiple rotating optical elements. A simple polariscope has two polarizing filters with a single one-quarter waveplate placed between the polarizing filters. Light is projected through the first polarizing filter and the one-quarter waveplate and is reflected from a sub-fringe birefringent coating on a loaded structure. Reflected light is analyzed with a polarizing filter. The polarizing filters and the one-quarter waveplate may be rotated together or the analyzer alone may be rotated. Computer analysis of the variation in light intensity yields shear stress magnitude and direction.
Abstract:
A photoelastic force sensor comprising a sensor plate or disk bonded by means of diffusion or reactive bonding of identical or like materials onto a first face of a spacer ring which defines an aperture. The spacer ring also has an appropriate thickness and width so that other sealing requirements that induce stress into the spacer ring are not appreciably passed onto the sensor plate. A seal plate is attached to a second face of the spacer ring to form a sealed cavity which can then be evacuated or pressurized as required for the application.