Short Focus Lenses for Projection with Translucent Screens

Projection from behind a translucent screen appears to have advantages in small theaters designed to be operated in low-rental space and with a minimum of operating staff. In large theaters this type of projection permits stage effects not so easily produced, perhaps, by any other means. — All advantage, however, is lost, unless the projection distance can be made very small for a given size of picture compared with the usual projection distance. For this purpose lenses have been developed with a focal length as short as one inch that will project 35-mm. film. Patents have been granted disclosing that all these make use of the diverging power of a negative lens in order to cover a large field of view. Such use of negative lenses was applied in submarine periscope construction at least as early as 1915. — In projection lens practice, simple meniscus, compound meniscus, and negative lenses with compound curves have been disclosed in the patents issued. Another construction will be shown in which the distortion introduced by the usual negative element is compensated by an additional positive element, the two elements being used in conjunction with any standard projection lens to give the effect of a lens of shorter equivalent focal length, high aperture, and freedom from distortion.

Print ISSN

0097-5834

Published

1932-12

Content type

Original Research

DOI

10.5594/J08986