"polarized sheet" to view glass stress

My company produces a birefringence imaging module which can be added to standard polarising microscopes and quantifies birefringence in glass caused by stress. See www.metripol.com for more details.

If you go to Walmart in the fishing department you can find a cheap (ten bux) pair of polirized sunglasses. Used for seeing the fish. When driving down the highway I can see the patterns in the back window of cars. Also the low e coating on home skylights shows up a bright purple. Low e coatings on home verticle windows too. And strain patterns in home windows as well. It is possible a more expensive set might do better.

Henry Grover Jr.
windowinspector@hotmail.com