Structural Thermal Optical Performance Analysis : a team work !

What is STOP analysis ? Many imaging or laser optical systems have to work in extreme conditions. It is the case of telescopes or camera lenses in optical system for aeronautics, space, balistic, underwater, nuclear or high-powered lasers. A Structural Thermal Optical Performance (STOP) analysis consists in modeling accurately temperature changes and structural loads (including thermal stress) on the optical system. The generated optical model enables to analyse the induced effect on the optical system performance. The goals of a STOP analysis could be to specify system tolerance budget for given thermal loading, to analyse the load capability of the structure, the structure distortion and stress or the surface distortion of an optical component and to evaluate the impact on the optical performance in terms of Zernike wavefront error. A STOP analysis could be conducted in three steps : -the conceptual design is a sensitivity analysis which considers no stress on components mounting, uniform gradients and bulk temperatures and simplified structural modeling, - the preliminary design is a mid-fidelity structural model which considers a simplified secondary structure including optics, more accurate load paths a more detailled thermal mapping and a material optimisation, - the design verificaion is a high fidelity structural model including the optics and optics mounts fully modeled, all test configurations and all temperatures cycles. It enables to predict the final optical performance. Software Tools to perform STOP analysis Various software can be used to perform STOP analysis : - Finite Element Modeling (FEM) software such as NASTRAN, ANSYS, - Thermal analysis software such as TMG, ESATAN,Thermica which simulates non-linear and transient heat transfer by conduction, radiation or convection. - opto-mechanical software such a SigFit can convert a surface from a Finite Element Modeling software into an interferogram which could be read by an optical software. - optical software such as Zemax or CodeV could predict the optical performance in terms of Wavefront error. Author : Scoptique is a consulting company with an in-house engineering division and a recruitment division, ProfileOptics. The engineering division proposes research and development studies in optical design and engineering. The recruitment division proposes internationnally to the optical systems industry a broad range of experts from optical engineering to mechanical, thermal, electronics, sofware or system engineering.