Apparatus for making light attenuating filters

Claim 1

In a light attenuating filter coating apparatus of the type wherein a patterned coating of light attenuating material is deposited on a transparent substrate from a vapor beam emitted by a source of appropriately vaporized, light attenuating material, the improvement comprising means defining a non-circular aperture of time-varying size between said vapor source and said transparent substrate for controlling the impingement of the beam on the substrate, means for varying the size of said aperture as a predetermined function of time, so that the resulting light attenuating filter is characterized by iso-attenuation contours of which at least portions thereof are non-circular, said means for defining said aperture of time-varying size comprising a pair of templates which are movable rectilinearly toward and away from each other along a path substantially parallel to said transparent substrate and the confronting edges of the templates are essentially concave.