Introduction to Optical System Design Optimization
A fixed-focus lens is a lens with only one fixed focal length. Compared to zoom lenses, fixed-focus lenses are simpler in design. Therefore more easily achieve demanding technical parameters, such as large entry pupil diameters.
The double Gaussian structure is a common fixed-focus lens structure, generally composed of 6 pieces, the front and the back one for the meniscus lens. Additionally, the stop is in the middle of the lens, and the entire structure is close to symmetry. This means that it is easy to correct aberrations related to the field of view such as coma, distortion, magnification, and chromatic difference of magnification. While the double Gaussian structure has been known for nearly 200 years, it and its variants are still widely used today.