Abstract: A stress measurement device for strengthened glass includes a polarization phase difference variable member configured to vary a polarization phase difference of a laser light by one wavelength of the laser light or more; an imaging element configured to image a plurality of times at a predetermined time interval a scattered light emitted according to the laser light with the varied polarization phase difference entering the strengthened glass, and obtain a plurality of images; and an arithmetic unit configured to measure a periodic change in luminance of the scattered light using the plurality of images, calculate a change in a phase of the change in luminance, and calculate a stress distribution in a depth direction from a surface of the strengthened glass based on the change in the phase.

Abstract: Disclosed is a method of measuring a surface refractive index of a strengthened glass including causing light to enter a surface layer of the strengthened glass through a liquid provided with a refractive index equivalent to that of a surface of the surface layer; a process of causing the light to be emitted from the strengthened glass through the liquid; converting two types of light components into two types of emission line sequences; capturing an image of the two types of emission line sequences; measuring positions of respective emission lines of the two types of emission line sequences from the image; and calculating refractive indexes of a surface of the strengthened glass corresponding to the two types of light components, or refractive index distributions of the strengthened glass in a depth direction from the surface corresponding to the two types of light components.

Abstract: A stress measurement device for strengthened glass includes a polarization phase difference variable member configured to vary a polarization phase difference of a laser light by one wavelength of the laser light or more; an imaging element configured to image a plurality of times at a predetermined time interval a scattered light emitted according to the laser light with the varied polarization phase difference entering the strengthened glass, and obtain a plurality of images; and an arithmetic unit configured to measure a periodic change in luminance of the scattered light using the plurality of images, calculate a change in a phase of the change in luminance, and calculate a stress distribution in a depth direction from a surface of the strengthened glass based on the change in the phase.

Abstract: Disclosed is a method of measuring a surface refractive index of a strengthened glass including causing light to enter a surface layer of the strengthened glass through a liquid provided with a refractive index equivalent to that of a surface of the surface layer; a process of causing the light to be emitted from the strengthened glass through the liquid; converting two types of light components into two types of emission line sequences; capturing an image of the two types of emission line sequences; measuring positions of respective emission lines of the two types of emission line sequences from the image; and calculating refractive indexes of a surface of the strengthened glass corresponding to the two types of light components, or refractive index distributions of the strengthened glass in a depth direction from the surface corresponding to the two types of light components.