Attenuation spot filters manufacturing process

Abstract

An attenuation spot filter adapted to extend the light intensity range of usefulness of cameras, particularly television cameras, by attenuating the input light intensity in accordance with reduced iris aperture, comprising an optical element having at its center a thin film coating the density of which decreases in a radially outward direction whereby light attenuation is a minimum at maximum iris aperture and is maximum at minimum iris aperture. The attenuation spot filter is manufactured by a thin film carbon deposit of controlled thickness and diameter onto an optical flat which is, after deposition, coated. The flat is held horizontally for vertical axial rotation about a controlled flame, with the distance between the flame and the flat being cam-controlled and with the flame jet being secured for vertical axial movement with a cam follower. The coating is float-applied for uniformity and the coating material is an alkyd resin and lacquer thinner mixture.

Dependencies are inferred from the claim text.