Abstract: A substrate holder and mask system for depositing curved films and mirrors on flat mirror substrates. A spherical mask is held in close proximity to a substrate by a support structure to intercept a fraction of vapor from a distant source. The film deposited on the substrate behind the mask has a spherically symmetric curvature when the source has a large area. The cross section of the mask support structure is made as small as possible to minimize irregularities in the spherical figure. A mirror is subsequently deposited on said curved substrate after removing said mask.

Abstract: A mirror for a ring laser gyro includes alternating optical quarterwave regions of SiO.sub.2 and ZrO.sub.2, and of admixtures of these. The alternating regions have thicknesses suitable for reflecting a laser beam in a ring laser gyro. A final coating of ZrO.sub.2 and SiO.sub.2, and of admixtures of these, is constructed so as to be made substantially of ZrO.sub.2 at a bottom portion and so as to have gradually increasing SiO.sub.2 content so that the top surface comprises substantially pure SiO.sub.2 material.

Abstract: An apparatus for monitoring ion beams with an electrically isolated aperture includes an ion beam source for generating an ion beam and an electrically conductive aperture plate arranged to collimate the ion beam. The aperture plate is electrically isolated from the rest of the deposition apparatus and is divided into a plurality of electrically isolated segments. A current monitoring device has an input connected to the aperture plate so as to monitor current from the aperture plate which is indicative of the ion beam performance.