Patent ID: 8780348

Claim:
An apparatus for quantifying unknown stress and residual stress of a material, the material being a birefringent or temporary birefringent material, the apparatus comprising: a light source for generating light beam of a single wavelength or multiple wavelengths; 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 the same as that of the material to be tested and being free of unknown stress and residual stress, which is mounted or located in front of the first quarter-wavelength plate with a face thereof facing a face of the first quarter-wave plate; a second quarter-wave plate in front of the standard material with its one face facing a face of the standard material; an analyzer in front of the second quarter-wave plate with its one face facing a face of the second quarter-wave plate; a loading unit for loading the standard material; a spectrometer in front of the analyzer for recording intensity of the light passing through the analyzer and 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, which combined with the normalized transmissivity of the material to be tested, a stress distribution of the material to be tested is then obtained.