Automatic iris for a television camera

Claim 1

In combination with a television camera which includes a front plate, a camera tube and a lens system for projecting a beam of light reflected from a viewed object upon the lightsensitive surface of said tube, an apparatus comprising a generally planar iris defining a aperture being selectively controlled and sized with respect to said light beam so as to control the quantity of light impinging the light-sensitive surface of said tube, actuating means coupled to said iris for controlling same with respect to said light beam, and a lightsensitive cell on said front plate and having an unobstructed view therefrom towards the objects being vieweD, said lightsensitive surface of said camera tube having a predetermined area of view, said photosensitive cell having an area of view centered on and substantially larger than said camera tube predetermined area so that said photocell may anticipate said light-sensitive surface viewing a beam of light exceeding a predetermined level and cause said iris to be obstructed before said light-sensitive surface is damaged, said photosensitive cell being connected to said actuating means and controlling the size of said iris aperture and thereby regulating the quantity of illumination passing through said iris aperture and impinging upon the lightsensitive surface of said camera tube, said iris aperture providing an enlarged size opening for low levels of illumination and providing a nonlinear change in size of opening for intermediate levels of illumination, said iris being positionable in a covering and obstructing position to protect said lightsensitive surface at illumination levels above predetermined level, said nonlinear reduction in size of said iris providing a depth of field greater than that for a linear reduction in size of opening, said actuating means selectively controlling said iris to and from said covering and obstructing position and said open positions.