Illumination control system for a film scanner

Abstract

In an illumination system for a film telecine scanner of the type adapted to provide a line of illumination on the image frames of a film which is supported for movement in a film gate of the scanner, an improved light control system for adjusting the amount of light that is delivered from a light source to an integrating cylinder to take into account fluctuations in intensity of the light source and desired intensity changes in the line of illumination upon a change of scene in the image frames of the film as the film is being scanned. The light control system comprises an aperture defining mechanism, a position servo regulator that maintains the aperture at a desired aperture opening despite disturbances tending to change the aperture between aperture changes, and an intensity servo regulator that takes into account the lamp intensity in resetting the aperture to a new position in response to a commanded light intensity related to a scene change, whereby aperture changes may be effected within the time of scanning a single image frame. The aperture defining mechanism employs first and second movable blades placed at a location in the optical path and movable between a full open aperture position outside the optical path and to one of a plurality of stopped down aperture defining positions interrupting the optical path and the resulting illumination line intensity in the course of scanning a single image frame.