Thermal editorial

The term "minimize" is used but theoretically one can drive it to zero with some caveats. The thermal coefficients, such as index (material and air) and expansion, are non linear. These coefficients have error bars around their measurements and this sometimes leads to a linear approximation to their values. Simulating thermal is just that - a simulation. Like any simulation if you put garbage assumptions in, you will get garbage predictions. Thermal defocus is not an exact science and one must be prepared that your hardware may not be "perfectly" passively athermal.