ABSTRACT
This chapter describes some of the most important optical systems using lenses. All the lenses in this optical system must have a minimum diameter to allow these (meridional ray and skew ray) two rays to pass through the whole system. The most common and traditional use of a lens is as a magnifier. The stop of the system is the pupil of the observing eye. A single lens has axial chromatic aberration. The advantage of a doublet made by joining together two lenses with different glasses is that a good correction of both axial chromatic and spherical aberrations can be achieved. An alternate series of imaging or relay lenses and field lenses form the system. The first imaging lens is at the entrance pupil and the last imaging lens is near the exit pupil, at the pupil of the observing eye. Projectors are designed to form the amplified real image of a generally flat object on a flat screen.
