Focal-Plane Shutters and the Design of High-Frame-Rate Cameras

Operating principles for a new family of rotating-mirror framing cameras which make use of focal-plane shutters are described and examples are given. The basic concept is an extension of the idea of isotransport of image and film, presently found only in moving-film cameras. The rotating mirror and a number of prisms, plane mirrors or concave mirrors are used to produce a sequence of connected frames which move past a fixed slit in the camera at constant velocity. The moving image segments seen through the slit are then relayed to a stationary film by means of a smear camera employing the same rotating mirror. The optics of the smear camera is arranged to stop the motion of each image on the film. As a consequence, a series of stationary images which have been scanned by a focal-plane shutter in a known way are formed on the film. Use of the focal-plane shutter offers the possibility of very precise time definition. Focal-plane shutter characteristics have both advantages and disadvantages in comparison with between-the-lens shutters. One advantage is that multiple slits may be employed. If the images from several equally spaced slits are relayed to independent film areas, it is possible to increase the number of frames and the effective framing speed of a camera without increasing rotor speed or sacrificing f number. Other possible uses of multiple-slit recording are described.

Print ISSN

0361-4573

Published

1960-11

Content type

Original Research

DOI

10.5594/J15550