Application: to measure the thermal strain of optical lens. Due to temperature variation the lens surface is expanding / contracting in radial direction with two extreme operating temperature. (-40C to +70C ) Optical lens is SF56A (CTE - 7.9*e-6 per Kelvin) What to do: I need to measure this expansion/contraction of lens. I think I can do that by strain gauge. But I was looking for some earlier references on internet as bonding on gauge is very tricky. Even a small scratch on lens can deteriorate its performance. So I need to very careful while bonding gauge on it. Questions: 1. Anyone have previous exp/suggestion on how to bond the gauge & its placement. 2. Any references on internet.