ABSTRACT
An optical system is basically formed by lenses and mirrors, but it has an extremely large number of possible configurations and requirements, as pointed out by Hilbert and Rodgers (1987). The optical system may have many different requirements, depending on its particular application, for example:
1. Speed or f-number FN 2. Field angular diameter 3. Resolution on and off-axis 4. Aperture size (entrance pupil diameter) 5. Physical size of the system 6. Construction difficulties 7. Cost, etc.
