A Three-Element Projector Condensing System

Chan Street

The design of an efficient optical condensing system is difficult to achieve, since a high aperture must be provided at the source, while an enlarged image of the source is required at the entrance pupil of the projection lens. The system outlined consists of three basic elements, together with a series of supplementary lenses to accommodate a range of projection lenses from 35 to 300 mm. Besides the requirement for high initial aperture, two additional goals were set: correction for the cosine falloff at the source; and compatibility with all projection lenses in a specified range of f-numbers. These two latter objectives were attained using a field flatness of 10% and an f/2.5 lens which received 90% of the flux at its entrance pupil. These conditions are based on a 50° acceptance angle at the filament of a 1200-W incandescent projection lamp.

Print ISSN
Published
1970-02
Content type
Original Research
DOI
10.5594/J10734