Measuring forces in transparent materials, particularly applicable to production of sheet glass for windows

摘要

A laser source (42) transmits monochromatic light through a polarizer (44) and a photoelastic modulator (46) providing two reference frequencies to the glass being measured (40) and a diffusing band (60). The diffused light is received by an analyzer (48) and photodiode (50) and synchronous detection at the two reference frequencies (54,56) enables the phase difference of the light to be determined for stressed and unstressed conditions