Methods and apparatus for creating an aspheric optical element and the

Abstract

A method and apparatus for coating optical substrates, such as a combiner substrate, is provided so as to create aspheric optical elements, such as aspheric combiners for heads up displays. Due to its asphericity, the aspheric optical element, such as an aspheric combiner, can compensate or correct for optical aberrations within an optical system, such as a heads up display. However, the coating method and apparatus of the present invention allows aspheric optical elements, including aspheric combiners, to be repeatedly fabricated in a less expensive manner. The coating apparatus includes a fixture for holding an optical substrate, such as a combiner substrate, in a predetermined aligned relation with a mask. The mask defines an opening having a predetermined shape which varies in at least one radial direction and through which a portion of the optical substrate is exposed. By creating a relative rotation between the mask and the optical substrate, an aspheric dielectric layer can be deposited on the substrate, such as via ion assisted deposition, which has a thickness which varies in a predetermined manner along at least one radial direction in correspondence to the predetermined shape of the opening defined by the mask. In order to create an aspheric combiner, a reflection coating can then be deposited upon the aspheric dielectric coating to reflect visual images provided by a cathode ray tube of the heads up display to the pilot without undesirable aberrations.