Transient thermal design for athermal bond-line estimates

Transient operating temperatures often allow a lens cell to expand before the lens itself, potentially leading to stresses well in excess of the lens tensile strength. The transients thus affect the calculation of the athermal bond-line thickness, estimates of which have historically been based on thermal equilibrium conditions. In this paper, we present both analytical expressions and finite-element modeling results for thermal-transient bond-line design. Our results show that a cell with a large CTE and a bond thickness based on thermal transients is the best strategy for reducing the tensile stress on the bonded lens over a range of operating temperatures.