STRESS MEASURING DEVICE FOR TEMPERED GLASS, STRESS MEASURING METHOD FOR TEMPERED GLASS, METHOD FOR MANUFACTURING TEMPERED GLASS, AND TEMPERED GLASS

摘要

This stress measuring device has: a polarization phase difference changing member which changes the polarization phase difference of a laser beam by one wavelength or more with respect to the wavelength of the laser beam; an imaging element imaging scattered light, which is emitted as the laser beam having the changed polarization phase difference is incident on a tempered glass, multiple times at predetermined time intervals, and acquiring a plurality of images; and a calculation unit which uses the plurality of images, measures periodic brightness changes of the scattered light, calculates phase changes of the brightness changes, and on the basis of the phase changes, calculates stress distribution in the depth direction from the surface of the tempered glass.