Abstract: A system and method for monitoring one or more objects that have been restrainedly secured to a vehicle by one or more restraint members. The system includes a plurality of sensors each configured for monitoring one or more of a compressive or tensile stress or strain in one of the one or more restraint members, and a controller for periodically interrogating each of the plurality of sensors to ascertain a value of stress or strain detected by the respective sensor. When a change in the value of stress or strain is indicative of loosened or overtightened restraint members, a mitigation event is triggered.

Abstract: The present invention discloses a method for detecting the mechanical response of a mechanical component by an organic mechanoresponsive fluorescent material, comprising the following steps of: selecting an organic mechanoresponsive fluorescent material; preparing an organic mechanoresponsive fluorescent material solution; forming a film on a metal surface; calibrating fluorescence intensity and obtaining the fluorescence intensity and distribution in a crack tip area; observing the fluorescence signal generated at cracks to monitor the occurrence of fatigue cracks, and predict a propagation pathway of fatigue cracks by using the fluorescence intensity distribution in the crack tip area.

Abstract: The prism-coupling systems and methods include using a prism-coupling system to collect initial TM and TE mode spectra of a chemically strengthened article having a refractive index profile with a near-surface spike region and a deep region. The initial TM and TE mode spectra are examined to see if they fall within a preferred measurement window that can produce an accurate estimate of the knee stress to within a select tolerance. If not, then measurement configuration of the prism-coupling system is changed and new TM and TE mode spectra are collected. This process is repeated until the new TM and TE mode spectra fall within the preferred measurement window. The new TM and TE mode spectra are then used to determine the knee stress. Changing the measurement configuration can include changing at least one of the measurement wavelength, interfacing fluid thickness and interfacing fluid refractive index.

Abstract: The invention relates to a method of determining the thickness of a sample. According to this method, a diffraction pattern image of a sample of a first material is obtained. Said diffraction pattern image comprises at least image values representative for the diffraction pattern obtained for said sample. A slope of said image values is then determined. The slope is compared to a relation between the thickness of said first material and the slope of image value of a corresponding diffraction pattern image of said first material. The determined slope and said relation are used to determine the thickness of said sample.

Abstract: Apparatus for detecting cracks in optically transparent articles e.g vials, comprising a mount for the article, a light source to direct light at a mounted article, an optical detector positioned to receive light from the light source passed through the article and to generate an electronic signal responsive to received light, first and second (analyzer) polarizers such that light from the light source passes through the first polarizer then through the article, then through the second polarizer on its path to the optical detector, with an optical wave plate positioned between the mount and the second polarizer, and an image processing system to process the electronic signal generated by the optical detector and to indicate the presence or absence of a crack in the article supported on the mount. A method of crack detection using the apparatus is also provided.

Abstract: Prism coupling systems and methods for characterizing curved parts are disclosed. A coupling surface of a coupling prism is interfaced to the curved outer surface of the curved part to define a coupling interface. Measurement light is directed through the coupling prism and to the interface, wherein the measurement light has a width of 3 mm or less. TE and TM mode spectra reflected from the interface are digitally captured. These mode spectra are processed to determine at least one characteristic of the curved part, such as the stress profile, compressive stress, depth of layer, refractive index profile and birefringence.

Abstract: A stress measurement method is provided of the present disclosure. The stress measurement method includes an image capturing procedure, a phase shift calculation procedure, an isochromatic intensifying procedure and a transformation procedure. The image capturing procedure is used to capture four light intensity images with four different phase angles of a sample. The phase shift calculation procedure is used to obtain an isochromatic retardation of the sample when the four light intensity images have sufficient light intensity values. The isochromatic intensifying procedure is used to calculate two enhanced light intensity values, the background of intensified isochromatic light intensity value and the amplitude of intensified isochromatic light intensity value to obtain an isochromatic retardation when the sample is in a low stress condition. The transformation procedure is used to transform the isochromatic retardation to a stress value of the sample.

Abstract: The present disclosure provides a sweep velocity-locked laser pulse generator (SV-LLPG) controlled using a digital phase locked loop (DPLL) circuit. The SV-LLPG is utilized for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with mm-level spatial resolution. A laser generates chirped laser pulses via injection current modulation and a DPLL circuit locks the optical frequency sweep velocity. A high-quality linearly chirped laser pulse with a frequency excursion of 117.69 GHz at optical communication bands using a distributed feedback laser is provided.

Abstract: Prism-coupling systems and methods for characterizing large depth-of-layer waveguides are disclosed. The systems and methods utilize a coupling prism having a coupling angle ? having a maximum coupling angle ?max at which total internal reflection occurs. The prism angle ? is in the range 0.81?max???0.99?max. This configuration causes the more spaced-apart lower-order mode lines to move closer together and the more tightly spaced higher-order mode lines to separate. The adjusted mode-line spacing allows for proper sampling at the detector of the otherwise tightly spaced mode lines. The mode-line spacings of the detected mode spectra are then corrected via post-processing. The corrected mode spectra are then processed to obtain at least one characteristic of the waveguide.

Abstract: A method for measuring blowing structures of a prestressed disc is described. The method has the steps of: (a) irradiating at least one analysis area of the disc with linearly polarized light from a radiation source at an angle of incidence and recording an image at least of the analysis area at an angle of observation using at least one detector, (b) supplying the image to an evaluation unit, and (c) using the evaluation unit to read a brightness profile along an analysis line on the image, to determine the local maxima and the local minima of the brightness profile, and to determine an intensity index by means of the difference between a brightness mean of the local maxima and a brightness mean of the local minima.

Abstract: A method for measuring blowing structures of a prestressed disc is described. The method has the steps of: (a) irradiating at least one analysis area of the disc with linearly polarized light from a radiation source at an angle of incidence and recording an image at least of the analysis area at an angle of observation using at least one detector, (b) supplying the image to an evaluation unit, and (c) using the evaluation unit to read a brightness profile along an analysis line on the image, to determine the local maxima and the local minima of the brightness profile, and to determine an intensity index by means of the difference between a brightness mean of the local maxima and a brightness mean of the local minima.

Abstract: An examination kit allows for discovery of the axis of direction and stress areas of polarized lenses. The kit comprises a lower light box with a transparent work surface, two polarized film sheets, a dial gauge with notches defining allowable variation of axis direction and an upper polarized lens for viewing the tested polarized lens in various states and positions.

Abstract: The present invention provides a monitoring device for detecting stresses and strains in structural components and a method of using the monitoring device. The monitoring device comprises a base material, one or more attachment points for attaching the monitoring device to a structure to be monitored, a detection zone on the monitoring device, and a means for detecting the presence of stress and strain in the detection zone. The dimensions and material of the monitoring device are chosen such that a predetermined level of strain transmitted to the monitoring device from the structure will result in a known level of stress and strain in the detection zone. Detection of stress and strain in the detection zone can be correlated to a level of stress and strain experienced by the structure at the point of attachment of the monitoring device.

Abstract: A structural color body is film-like and comprises a front surface layer disposed on a front surface side and a back surface layer disposed on a back surface side, the front surface layer and the back surface layer contain block copolymers and have micro-phase separated structures including lamellar micro domains, each of the micro domains has a wave-like shape having amplitudes in the thickness direction of the structural color body, a maximum value of distances predetermined in the micro domains of the front surface layer is larger than the wavelength in the visible light range, and distances predetermined in the micro domains of the back surface layer are equal to or less than the wavelength in the visible light range.

Abstract: A structural color body is film-like and formed of a resin layer containing a block copolymer, the resin layer has a micro-phase separated structure including lamellar micro domains, each of the micro domains has a wave-like shape having amplitudes in the thickness direction of the structural color body, and in each of the micro domains, a maximum value of distances in the direction between the tops of convexities and the bottoms of concavities is larger than the wavelength in the visible light range.

Abstract: A photoelastic coating for structural monitoring of bridges, buildings, and other structures comprises an optically translucent or transparent photoelastic layer. The photoelastic coating is applied to the structure as a solvent-based liquid or gel. The photoelastic properties of the photoelastic layer are used to detect stress and strain or plastic deformation in the structure using photoelastic techniques. Also described is a method of structural monitoring comprising applying a photoelastic coating to a structure as a solvent-based liquid or gel. Presence of fringe patterns in the reflected light from the photoelastic layer indicates the presence of stress and strain in the photoelastic layer. Stress and strain in the photoelastic layer indicates stress and strain or plastic deformation in the underlying structure. The invention can be used for detecting when structures have been overloaded or when stress limits have been exceeded.

Abstract: A film-like structural color body comprises a front surface layer disposed on a front surface side, a back surface layer disposed on a back surface side, and an intermediate layer disposed between the front surface layer and the back surface layer, the front surface layer, the back surface layer and the intermediate layer contain block copolymers and have micro-phase separated structures including lamellar micro domains, each of the micro domains has a wave-like shape having amplitudes in the thickness direction of the structural color body, a maximum value of predetermined distances in the micro domains of the front surface layer and a maximum value of predetermined distances in the micro domains of the back surface layer are larger than the wavelength in the visible light range, and predetermined distances in the micro domains of the intermediate layer are equal to or less than the wavelength in the visible light range.

Abstract: The disclosure is directed to a photoelastic method for measuring the absolute zero crossover temperature Tzc of a sample of materials (transparent glass, glass-ceramic or ceramic) directly, without requiring calibration against a primary technique. The method involves subjecting the sample to a temperature gradient that generates a stress distribution pattern within the sample. When some portion of the sample is at a temperature equal to the Tzc of the material, the pattern adopts an easily identifiable shape whose measurement allows the calculation of Tzc. Silica-titania glass, which has a low thermal expansion, is used as an exemplary material.

Abstract: An examination kit allows for discovery of the axis of direction and stress areas of polarized lenses. The kit comprises a lower light box with a transparent work surface, two polarized film sheets, a dial gauge with notches defining allowable variation of axis direction and an upper polarized lens for viewing the tested polarized lens in various states and positions.

Abstract: A fiber-optic based thrust load measurement system is coupled to a bearing housing. The measurement system includes at least one fiber optic sensor configured to detect one or more parameters related to the bearing housing. An optical coupler is configured to regulate light signals emitted from a light source and light signals reflected from the fiber optic sensor. A detector system is configured to receive light signals from the optical coupler. A processor is configured to receive an output from the detector system and to determine a thrust load on a thrust bearing based on the detected one or more parameters related to the bearing housing.

Abstract: An apparatus for determining fiber orientation parameters of a sheet of material during a production process includes a polarized radiation generating system operable for providing polarized radiation having a frequency of at least 1×108 Hz. The radiation is aligned to be incident on a sheet material to be characterized. A polarimeter is aligned to receive the radiation transmitted by the sheet material. A photodetector is provided for measuring radiation received after polarization processing by the polarimeter. A processor is coupled to the photodetector for calculating Stokes parameters of the sheet material based upon intensities of the radiation received and determines at least one parameter relating to fiber orientation of the sheet material based upon the Stokes parameters.

Abstract: An apparatus and method for measurement of the stress in and thickness of flat glass or curved glass segments is disclosed that uses fluorescence to quickly and accurately ascertain both the thickness of the stress layers and the wall thickness in addition to the stress curve in flat glass or curved glass segments. The apparatus and method may be used to quickly and accurately measure both the stress in and the thickness of flat glass or curved glass segments at a plurality of various locations therein. The apparatus and method are adapted for large scale flat glass or curved glass segment manufacturing, and are capable of high speed measurement of the stress in and the thickness of the flat glass or curved glass segments.

Abstract: An apparatus (200) for determining fiber orientation parameters of a sheet of material during a production process includes a polarized radiation generating system (201, 202) operable for providing polarized radiation having a frequency of at least 1×108 Hz. The radiation is aligned to be incident on a sheet of material to be characterized (203). A polarimeter (204, 205) is aligned to receive the radiation transmitted by the sheet of material (203). A photodetector (206) is provided for measuring radiation received after polarization processing by the polarimeter. A processor (207) is coupled to the photodetector (206) for calculating Stokes parameters of the moving sheet (203) based upon intensities of the radiation received and determines at least one parameter relating to fiber orientation of the moving sheet based upon the Stokes parameters.

Abstract: The present invention provides a monitoring device for detecting stresses and strains in structural components and a method of using the monitoring device. The monitoring device comprises a base material, one or more attachment points for attaching the monitoring device to a structure to be monitored, a detection zone on the monitoring device, and a means for detecting the presence of stress and strain in the detection zone. The dimensions and material of the monitoring device are chosen such that a predetermined level of strain transmitted to the monitoring device from the structure will result in a known level of stress and strain in the detection zone. Detection of stress and strain in the detection zone can be correlated to a level of stress and strain experienced by the structure at the point of attachment of the monitoring device.

Abstract: In accordance with an aspect of the present invention, there is provided a photoelastic coating for structural monitoring comprising an optically translucent or transparent photoelastic layer. The photoelastic coating is applied to the structure as a solvent-based liquid or gel that can be cured without heating. The photoelastic properties of the photoelastic layer can be used to detect stress and strain or plastic deformation in the structure using photoelastic techniques. In accordance with another aspect of the invention, there is provided a method of structural monitoring using a photoelastic structural monitoring coating. The method comprises the steps of providing a structure for which structural monitoring is desired, applying a photoelastic layer to said structure as a solvent-based liquid or gel, and curing said photoelastic layer in place on said structure.

Abstract: A scanning system includes a cable take-up mechanism that uses a series of pulleys that determine the bend diameters of a scanning system. The mechanism is particularly suited for a spectrometric, e.g., infrared, scanning system where moving scanner or sensor head essentially houses only the optical elements while essentially of all the other electronic and optical components associated with the measurement are housed in an easily accessible compartment that is remote from the moving scanner head. Light is transmitted through optical fiber cables. The cable take-up mechanism maintains the fiber optic cable at essentially constant total bend length and bend diameter thereby minimizing any dynamic changes to spectral bend losses as the optical head is scanned. The light weight construction of the sensor head further reduces vibrations associated with the moving scanner head.

Abstract: A color switchable stress/fracture sensor in combination with a structure. The combination apparatus includes a structure requiring stress and/or fracture detection, and at least one elasto-mechanoluminescent material at least partially dispersed in and/or on the structure and/or in a coating on the structure. The combination apparatus further includes at least one fracto-mechanoluminescent material at least partially dispersed in and/or on the structure and/or in a coating on the structure, and at least one fiber optic cable positioned to receive and transmit sufficient light emitted from the elasto-mechanoluminescent material due to stress applied to the elasto-mechanoluminescent material and to receive and transmit sufficient light emitted from the fracto-mechanoluminescent material due to fracture of the fracto-mechanoluminescent material.

Abstract: This invention relates to a process for using computerized molecular interaction modeling to predict the adhesive interactions between a substrate and a polymer. The molecular modeling method may be used to predict and select optimal adhesion promoting monomers for use in latex polymer coatings, providing the best wet adhesion to alkyd-coated substrates. The molecular modeling method could also predict substrate polymer pairs having the least affinity, and thus the most useful as a release liner.

Abstract: Photoelastic elements are formed deliberately with stress concentrations so that, when evaluated with a polariscope, more pronounced isochromatic bands or fringes result when loads are applied to these elements or to assemblies of these elements. A kit of photoelastic elements, at least some of which have stress concentrations formed therein, is also disclosed. In addition, a toy for producing color patterns is disclosed.

Abstract: Apparatus and a method for inspecting a topology of a surface (2) of a structural member (1) are provided. The degree to which a known type of stress has been applied to the member may be ascertained using a Moiré grid (8). The method involves providing a range of calibration samples of structurally equivalent members, the samples each having been subject to the known type of stress to a differing respective degree. Measurements taken using the apparatus and method of the invention are then compared with measurements taken from a calibration sample to determine the amount of stress which has been applied.

Abstract: A film is placed between contacting surfaces in an assembly. The film has an optical property responsive to pressure. A compressive force is applied to the contacting surfaces to generate an initial pressure pattern. The film is removed from between the contacting surfaces. The optical property is sensed to derive a sensed initial pressure pattern. A stored setting controls the compressive force. The sensed initial pressure pattern is compared to a reference pressure pattern. The stored setting is updated to adjust the compressive force as a function of the comparing.

Abstract: The elaborately calculated method of the present invention using photoelastic analysis for finding contact relation between ball and track is characterized in that a photoelastic plate having a semi-circular section is used in measurement by observing contrast of stripes appeared thereon in stead of observing track profile from the plucked image of the object in conventional technique therefore being released from shortcoming of inaccurate measurement result due to vagueness of profile of plucked image.

Abstract: The invention provides for a detector assembly. fiber assembly and screening system for optical measurements.

Abstract: Apparatus for the measurement of out of plane displacements of a panel of material under test comprises; a laser (2) capable of focusing a laser spot (8) onto the surface of the panel (6) of material; a line generating lens (12) for converting the image of the projected laser spot (8) into a focused line (22); and, a photo diode (16) responsive to illumination by laser light and so orientated and disposed in relation to the generated laser line (22) that the out of plane distortions of the panel (16) and resulting movement of the spot (8 to 8') produce a corresponding translation of the generated line (18) across the face of the photo diode (16) and the photo diode (16) produces a recordable output proportional to the out of plane deflection of the panel (6).

Abstract: In a system for in-situ delamination detection in composites, the invention employs a system which evaluates the mechanical vibration response of composite material structures. The damping characteristics of the composite structure are extracted from the detected wave properties generated by imbedded piezoelectric ceramic actuators and received by imbedded high strain sensitive fiber optic sensors. Such a sensor system is simple to operate for real-time non-destructive strain and displacement monitoring and delamination detection, without the need to remove the tested surface from operation.During the routine structural integrity monitoring operation, mechanical vibration pulses are launched into the composite from one actuator. The strain signal's propagation patterns are measured in real time by the fiber-optic sensors at different grating locations. Different travel times are computed dependent on the location of the receiving gratings.

Abstract: A part for projecting a measuring light beam onto a sample and a light receiving part are arranged on the same side of a sample surface so that the measuring light beam is concentric with the light receiving part, the measuring light beam which is converted to a linearly polarized light beam through a polarizing element is projected to the sample so that the measuring light beam outgoing from the sample to the projecting side is received and detected through the same polarizing element. A plurality of sets of polarizing elements and light receiving parts are set so that the polarizing elements have different polarization directions, to calculate retardation from transmitted light intensity levels as obtained.

Abstract: A method of stress-optical force measurement where a linearly polarized light ray is guided into a stress-optical measurement array consisting of several measurement members on which the force to be measured acts in a distributed manner. The light ray successively traverses the measurement members while being influenced in a force-dependent manner and is applied to a subsequent evaluation unit for evaluation. The invention also relates to a measurement device for performing the method, comprising a measurement array and an evaluation unit between two plates which are arranged in parallel at a distance from one another. The measurement array consists of at least three spaced stress-optical measurement members which keep the plates at a distance from one another, influence the light ray in a force-dependent manner, and guide the light ray into the evaluation unit arranged between two measurement members.

Abstract: The combination of a polarizer and an analyzer, and a sample interposed therebetween are rotated relative to each other to determine the relationship between the angle of rotation and the intensity of light transmitted through the arrangement. The birefringence of the sample is obtained from the retardation values calculated from the result of the determination. When the determination is made for two kinds of light with different wavelengths close to each other, the retardation can be determined straightforwardly. When at least three kinds of light with different wavelengths are used for the determination, different retardation values are obtained for the respective wavelengths for a highly accurate analysis.

Abstract: A method for photoelasticity examination of a stress or strain field comprises successive steps. A two dimensional image of a test-piece is formed which has isochromatic fringes in the form of an array of pixels and the grey level of each pixel is stored as a digital value. From the isoclinals, the orientation of the main stresses .sigma.I and .sigma.II is determined at each pixel and the angle of orientation is stored for obtaining each pixel; from the stored pixels, the law of variation of brightness is worked out along at least three lines parallel to an arbitrary direction chosen by the operator and passing completely through the test-piece; from a condition at the limits and by finite differences then integration, a value is determined representative of .sigma.I and .sigma.II at each point of the median line among the three lines and .sigma.I and .sigma.II are derived from the stored digital values and from the computed values of .sigma.I and .sigma.II.

Abstract: A system and method for determining the anisotropy of a sample of a light transmitting sheet is disclosed. The surface of the sample is irradiated with a polarized light which is directed through the sample to an analyzer element. The polarizing plane of the analyzer is matched to, or maintained in a predetermined angular relation to, the polarizing plane of the polarized light. The sample is rotated relative to the analyzer element so that the optical anisotropy can be determined from the relationship between the rotation angle and the output of measured light.

Abstract: A precision optical distance measuring device utilizes coherent optical detection for extreme precision, and polarization preserving fiber to enable its use in limited access environments. A laser diode provides a linearly polarized source light beam which is directed to a polarizing beam splitter. The source beam passes through the beam splitter and is focused by a lens into a polarization preserving fiber where it travels along one optical axis toward a probe head disposed at the target location. In the probe head, the source beam is focused by a lens onto the target. After focusing, the source beam is passed through a quarter-wave plate. The interface between ambient air and the target-side of the quarter-wave plate reflects a local oscillator beam back through the quarter-wave plate. Meanwhile, the source beam is reflected from the target as a return beam.

Abstract: An apparatus for optically detecting electronic circuit malfunctions includes a light transmitting plate member which is adapted to be positioned adjacent to a plurality of individual electronic circuit elements positioned on a printed circuit board. First and second polarizing filters are positioned adjacent to opposing edges of the light transmitting plate. As the individual electronic circuit elements positioned on the circuit board are operated, the nonuniform heating of the light transmitting plate by the circuit elements produces mechanical stresses within the plate. As monochromatic or white light is passed through the pair of polarizing filters and the light transmitting plate, a light/dark striated pattern of light is produced on the surface of the second polarizing filter. By recording the pattern of a properly operating printed circuit board, a reference pattern may be obtained. Subsequent patterns of light are compared to the reference pattern in order to detect differences between patterns.

Abstract: A photoelastic effect measuring device comprising a single white light source, a prism dispersing light emitted by said white light source and a variable slit device, which selects an arbitrary spectrum of light thus dispersed is disclosed, in which for a photoelastic effect measurement using white light, the slit width is opened totally so that all the light spectrum pass therethrough so as to pass through a sample to be measured and for a photoelastic effect measurement using a specified monochromatic light beam, the slit width is controlled so as to have a predetermined opening so that only a specified light spectrum can pass therethrough so as to pass through a sample to be measured.

Abstract: A method for obtaining quantitative data which relates the sound pressure distribution in a body to an ultrasound pulse waveform which propagates through the body, based on photoelastic measurement and analysis. The method involves producing a first image of the body, into which the ultrasound pulse was launched, by recording the image of linearly polarized straboscopic light which is directed into the body. Thereafter, a second image is taken of the stroboscopic light with the principal axis of the linear polarizer offset by 45.degree. relative to the first image. The first and second images are combined to produce a synthesized image and the above-mentioned quantitative data is derived from the synthesized image.

Abstract: An apparatus has been developed to experimentally determine the state and amount of birefringence in an arbitrary plane within a birefringent body using an entirely new method. Such information can be used to determine the optical anisotropy in solid and liquid bodies, residual and induced stress fields, etc. This apparatus uses a collimated and polarized light beam which scans linearly the plane of measurement within a transparent birefringent or photoelastic object, and a device which collects particular sheets of light scattered along the path of the light beam, the intensity of which is directly related to the state of birefringence at each scattering point at the plane of measurement within the birefringent body. An imaging device produces in the image plane of the apparatus the lines of constant light intensities which are the lines of constant values of accumulated birefringence.

Abstract: A new method and device has been developed to determine experimentally the state and amount of birefringence along any arbitrary direction through a birefringent body. Such information can be used to determine the optical anisotropy of solid and liquid bodies, the residual and induced stress fields, etc. Essentially, this method and device separates, from the light scattered in all directions along an arbitrary path of laser light in a body, three sheets of light which are subsequently collimated; each of these light sheets contains parallel light rays carrying information of interest. The middle light sheet indicates the line of measurements, which is identical with the path or position of laser beam in a body. The two outer light sheets carry two complementary and independent pieces of information on the state and amount of birefringence along the line of measurements. Thus, both outer sheets of light can be used simultaneously to increase the reliability and accuracy of the birefringence measurements.

Abstract: An apparatus used directly on a flat sheet of transparent material, especially tempered glass, for simultaneous measurement of sign and amplitude of stress across the section of said glass sheet using scattered light. The apparatus allows reliable and repetitive measurements independently of the operator's subjective observations, since the data is read through an automatic system. The apparatus has a Helium-Neon (He-Ne) laser source of 1 to 5 mW, whose light beam is linearly polarized, then modulated with a series of wave plates (2,2', 2"), then passed through a collimator (3) and subsequently made to strike a prism (4) optically coupled with the glass sheet (V) being tested. Variation in intensity of the interference fringes is revealed by a TV camera (5) having a macrophotographic lens system (5') which focusses the scattered light on a solid-state array photodetector (5').

Abstract: The invention relates to the measurement of stresses in float glass. In a process, the stresses in the glass are continuously determined by scanning the glass over its entire width and simultaneously measuring the temperature of the glass at each location scanned. A measurement of double refraction representing stresses is combined with the temperature measurement to establish values of the permanent stresses in the glass. The invention includes apparatus for carrying out the process.

Abstract: The internal stress state of a plate of heat tempered plate glass is tested by means of a device which uses a source of polarized monochromatic infrared radiation. This radiation passes through the glass in a point, and the variation of the polarization state is determined by means of an analyzer with the polarization axis at 90.degree. with respect to the polarizing filter.

Abstract: In a polariscope including first and second quarter wave plates arranged one on either side of a sample under test, first and second liquid crystal devices are provided adjacent the quarter wave plates and can be switched between two optical conditions to alter the polariscope between a plane polarized and a circularly polarized mode.