Figure 1 (left) shows a photoelastic fringe pattern in a light-field circular polariscope near the edge of a tempered glass panel of 6 mm thickness.
s] in all the specimens was measured with the scattered light polariscope SCALP (Glasstress Ltd.
In  Seebeck gave an interpretation of the obtained interference fringes and investigated the changes of the fringe patterns when the specimens were rotated in a polariscope.
1 shows the polariscope where polarization is created by reflection from the glass plate G-G.
In  data is described about testing of 360 glass panels by first measuring the residual surface stress with the GASP polariscope (GASP is registered trademark of Strainoptics Technologies, Inc.
For industrial applications, a portable scattered light polariscope, referred to as the SCALP, has been developed at GlasStress Ltd .
This paper gives a brief description of the portable polariscope
SCALP and some measurement results, which are compared with the four-point bending test and fragmentation test.