For monitoring applications prone to temperature fluctuations, it is important to design optics that are insensitive to thermal change in the surrounding environment. Developing an athermalized optical design, is especially critical because temperature changes can cause the materials in a lens to expand and contract at different rates. If this is not carefully considered in your optical design, then a lens will lose focus as the temperature changes.
Read now: https://resolveoptics.com/athermalisation-explained/