There are many thermal camera lenses types used in thermal imaging systems. The types of thermal camera lenses chosen for a particular system can depend on (among others): the spectral range of interest, e.g., NIR, SWIR, MWIR, or LWIR, the number of FOVs required (e.g., single, dual, continuous zoom), whether or not they need to be athermal (no need for refocusing following a temperature change), and their focus mechanism, e.g., fixed, manual, or motorized. Once the system requirements are established and the thermal camera lenses specifications are drafted, the optical designer must supply an optical design that meets specification requirements. Additionally, the designer must be cognizant of manufacturability and cost.
The stages of optical design include the following:
- Establishing the basic geometry.
- Optimizing performance, fit, and cost.
- Building a tolerance set.
- Documenting the design and performance.
The principle method of arriving at a good optical design is optimization, which is varying the numerical design parameters to achieve a desired imaging outcome such as a tight focus or a flat field. Design parameters can be extensive owing to, for example, the number of thermal camera lenses involved, their shapes or curvatures, the optical materials that make up the thermal camera lenses, whether there is an intermediate focus, etc.