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: A method for analyzing stress in an object according to spectrum data is provided. The spectrum data is obtained from an interference fringe pattern of the object that results from performing photoelasticity. The method includes: analyzing the spectrum data to obtain three sets of intensity data related respectively to different wavelengths of light used in photoelasticity; calculating wrapped phases according to the three sets of intensity data, respectively; calculating preliminary stress values according to the wrapped phases, respectively; determining a system of stress equations according to a relation among the preliminary stress values; and calculating an estimated stress value using the system of stress equations.

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: An optical interferometric system for measurement of a full-field thickness of a plate-like object in real time includes two light sources, two screens, two image capturing devices, and an image processing module. The light sources radiate incident lights toward a reference point on the plate-like object in respective directions to produce respective interference fringe patterns (IFPs). The image capturing devices capture light intensity distribution images respectively of the IFPS imaged respectively on the screens. The image processing module calculates a fringe order at the reference point according to the light intensity distribution images, and obtains a full-field thickness distribution of the plate-like object according to the fringe order.

Abstract: A method for analyzing stress in an object according to spectrum data is provided. The spectrum data is obtained from an interference fringe pattern of the object that results from performing photoelasticity. The method includes: analyzing the spectrum data to obtain three sets of intensity data related respectively to different wavelengths of light used in photoelasticity; calculating wrapped phases according to the three sets of intensity data, respectively; calculating preliminary stress values according to the wrapped phases, respectively; determining a system of stress equations according to a relation among the preliminary stress values; and calculating an estimated stress value using the system of stress equations.

Abstract: An optical interferometric system for measurement of a full-field thickness of a plate-like object in real time includes two light sources, two screens, two image capturing devices, and an image processing module. The light sources radiate incident lights toward a reference point on the plate-like object in respective directions to produce respective interference fringe patterns (IFPs). The image capturing devices capture light intensity distribution images respectively of the IFPS imaged respectively on the screens. The image processing module calculates a fringe order at the reference point according to the light intensity distribution images, and obtains a full-field thickness distribution of the plate-like object according to the fringe order.

Abstract: A device for real-time thickness inspection is provided. An optical interferometric technique is used. Measurement requirements in rapid online thickness inspection can be satisfied. An object is measured in a non-contact and non-destructive way. For measuring, an optical spherical wavefront is radiated on the object in an oblique angle. The interference fringe pattern (IFP) thus imaged on a screen is directly related to the thickness distribution of the object. The phase difference on the same horizontal cross section in the IFP monotonically decreases from the light source side to the other side. Accordingly, phase unwrapping can be effectively performed without using phase shift. The present invention achieves rapid on-line thickness inspection through the optical path of interference without using optical lens groups and special optical elements.

Abstract: A device for real-time thickness inspection is provided. An optical interferometric technique is used. Measurement requirements in rapid online thickness inspection can be satisfied. An object is measured in a non-contact and non-destructive way. For measuring, an optical spherical wavefront is radiated on the object in an oblique angle. The interference fringe pattern (IFP) thus imaged on a screen is directly related to the thickness distribution of the object. The phase difference on the same horizontal cross section in the IFP monotonically decreases from the light source side to the other side. Accordingly, phase unwrapping can be effectively performed without using phase shift. The present invention achieves rapid on-line thickness inspection through the optical path of interference without using optical lens groups and special optical elements.

Abstract: An apparatus for quantifying unknown stress and residual stress of a material to be tested, the material being a birefringent or temporary birefringent material, which includes a light source, a polarizer in front of the light source for converting a light beam from the light source into a beam with linear polarization, a first quarter-wave plate in front of the polarizer for generating circular polarization, a standard material, a second quarter-wave plate, an analyzer, a loading unit, a spectrometer for obtaining transmissivity spectrum of the standard material under the wavelength of the light source and a detecting module connected to the spectrometer to have the transmissivity spectrum of the material to be tested and consequently a stress quantifying formula for the standard material.

Abstract: An apparatus for quantifying residual stress of a birefringent material comprises a light source generating light; a vertical polarizer converting a beam of light into a beam with vertical polarization; a standard material being mounted in front of the vertical polarizer; a horizontal polarizer converting a beam of light into a beam with horizontal polarization; an applied force unit applying different forces to the standard material; a spectrometer being mounted in front of the horizontal polarizer and recording intensity of light passing through the horizontal polarizer and transmittance of the standard material and a processing module being connected to the spectrometer, deriving a stress formula from the applied forces and transmittances of the standard material and obtaining a stress distribution of the birefringent material. A method for quantifying residual stress of a birefringent material is also disclosed.

Abstract: An apparatus for quantifying unknown stress and residual stress of a material to be tested, the material being a birefringent or temporary birefringent material, which includes a light source, a polarizer in front of the light source for converting a light beam from the light source into a beam with linear polarization, a first quarter-wave plate in front of the polarizer for generating circular polarization, a standard material, a second quarter-wave plate, an analyzer, a loading unit, a spectrometer for obtaining transmissivity spectrum of the standard material under the wavelength of the light source and a detecting module connected to the spectrometer to have the transmissivity spectrum of the material to be tested and consequently a stress quantifying formula for the standard material.

Abstract: An apparatus for quantifying residual stress of a birefringent material comprises a light source generating light; a vertical polarizer converting a beam of light into a beam with vertical polarization; a standard material being mounted in front of the vertical polarizer; a horizontal polarizer converting a beam of light into a beam with horizontal polarization; an applied force unit applying different forces to the standard material; a spectrometer being mounted in front of the horizontal polarizer and recording intensity of light passing through the horizontal polarizer and transmittance of the standard material and a processing module being connected to the spectrometer, deriving a stress formula from the applied forces and transmittances of the standard material and obtaining a stress distribution of the birefringent material. A method for quantifying residual stress of a birefringent material is also disclosed.