Abstract: A helmet mounted display uses a see-through visor holographic combiner to provide, in the normal field of view of a helicopter pilot, a pair of images derived from an image source such as a miniature cathode ray tube. A source of the video display may be an infrared sensor mounted on an external turret underneath the helicopter. The turret rotates in response to helmet movements so that the pilot is continually provided with a dual image from the CRT display which corresponds with the external scene as visible through the visor.

Abstract: A holographic recording medium is treated to reduce or eliminate unwanted extraneous diffraction and flare. Regions adjacent surfaces of the medium are desensitized to reduce contrast in the holographic fringe pattern along the surfaces, thereby eliminating planar phase grating effects. Treatments include applying a burst of gas or vapor to the surfaces of the medium, irradiating the surfaces with highly absorbed incoherent light, thermally treating the medium as it is built up from sequentially applied layers, building up layers of different concentrations of light-sensitive matrial, and developing diffusion regions at interfaces of layers within the holographic recording medium.