Methods for measuring of stress in glass

Home Compensator Senarmont Lambda Plate Fringes

Set-up for measuring stress in glass
First polariser to get polarised light at 45 degrees with the main stress axis Sample which gives difference in phase between light polarised in X or in Y direction (Optional)
Second polariser (called Analyser) to get a light intensity dependent of the phase shift at the sample

A set-up for measuring stress mainly consists of two (crossed) polarisers. With no stress, the intensity after the second polariser (called Analyser) is zero. With stress, the intensity is not zero anymore, but is difficult to measure by eye. Therefore a measuring device is inserted. For most measuring devices the intensity after the Analyser is changed back to zero, this zero intensity is easy to see by eye.
The following methods can be used to measure stress:


The previous mentioned methods can be automated. For this, the light through the sample is sampled with a camera connected to a computer. Also, dependent on the measuring method, some special hardware has to be used:

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