For high temperature process monitoring, optical systems must be designed to ensure performance is maintained at the application operating temperature. When a material heats up there is expansion. The rate of expansion differs depending on material types. To avoid your optical system going out of focus, as it reaches operating temperatures, you must take careful consideration of the rate of expansion of components and air spaces. Temperature also affects the refractive index of materials so this needs to be considered in optical designs.
Learn more: https://www.resolveoptics.com/monitoring-high-temperature-processes-design-challenges/
