Long-life focal plane shutter for reconnaissance cameras

Abstract

A shutter for reconnaissance cameras includes a digital signal processor (DSP) system which provides for control of motors moving two curtains. The curtains each define an edge, the gap between the edges of the curtains defines an exposure slit. The shutter replaces the prior art DC curtain motors and potentiometer curtain position sensing devices with AC motors having integral resolvers that provide motor shaft position feedback information. Furthermore, a mechanical clutch coupling the curtains together, which has been standard practice in the prior art, has been eliminated, with the precise movement of the curtains governed by the motors under control by the DSP. The marriage of DSP control with the AC motors and resolvers provides a direct coupling to the curtains, with built-in motor shaft position feedback via the resolvers. This design allows not only precise movement of the curtains and control of the exposure slit, but also provides for a dramatically increased durability, reliability, long mean time between failure, and high frame rates. The shutter is thus able to meet the requirements of the latest generation of reconnaissance cameras, whereas known prior at shutters lacked these capabilities due to their inherent design limitations.