Survey camera automatic iris control - has periscopic objective which minimises parallax effects and has semi-reflecting surface on prism

摘要

Automatic iris adjustment for cine-cameras employing a light sensitive photo-cell sampling part of the image being directed onto the film emulsion, the photo-cell output controlling the iris via motor driven gearing. The system is particularly suitable for use with cameras employed in survey work and geodesy generally, overcoming the human element in appreciation of parallax effects. Input light follows a path through an input prism capable of movement about a very small angle, 85% of the total light is directed by a second prism onto the film surface, the remainder being transmitted to the photo-cell. The iris system lies between the two prisms set up in a periscope format.