Abstract: An encoded hologram that produces a first image and a second image pursuant to playback illumination, wherein the first image is resolvable by human vision while the second image is not resolvable by human vision when the playback illumination comprises non-coherent broad band illumination, and wherein the second image is machine readable when the hologram is illuminated with playback illumination that is based on the original reference beam.

Abstract: Multiple layers or holographic exposures and methods for preparing multiple layers of holographic exposures are described. The multiple layers of holographic exposure combine to form holographic stacks and are fabricated from layers of exposed and processed photosensitive recording films, each of which has at least one independently recorded hologram. The holographic stacks are useful for providing wide bandwidth holograms and holograms having superimposed images.

Abstract: A method for precisely controlling the overall average diffraction efficiency of a hologram including the steps of (a) providing a hologram layer that includes a hologram formed pursuant to hologram forming exposure and development, (b) coating the hologram layer with a photoresist layer, (c) masking the photoresist layer with a mask having opaque and transparent areas wherein the proportion of the opaque areas relative to the transparent areas is selected pursuant to the desired diffraction efficiency, the opaque and transparent areas being sufficiently small so as to have little noticeable effect when the resulting hologram is played back, (d) exposing the photoresist layer to actinic illumination through the mask transparent areas, (e) developing the photoresist layer to remove the photoresist in the areas illuminated by the actinic illumination to uncover the areas of the recording material corresponding to the transparent areas of the mask, (f) etching the recording material to remove the areas thereof t

Abstract: A hologram efficiency adjusting process that includes scanning the brightness effect of a hologram, which is either the hologram to be adjusted or a hologram representative of the hologram to be adjusted, to provide brightness vs. position information. The brightness information is utilized to produce a variable duty cycle half-tone mask that contains a pattern defining the areas of the hologram which are to be removed, with the pattern being unresolvable by the viewer of the hologram from which holograms have been removed pursuant to the mask pattern. The hologram to be adjusted is then photoresist coated and etched in accordance with the mask. Alternatively, the brightness information can be utilized to directly expose, for example by a laser scanner, photoresist disposed on the hologram to be adjusted.

Abstract: A head-up display for a vehicle, including a primary image reflection hologram supported by a transparent substrate located in the vehicle operator's field of view for the ambient scene in front of the vehicle, a light source for providing playback illumination to the primary image hologram, and a guard hologram in front of the primary image hologram for substantially reflecting ambient illumination that otherwise could spuriously turn on the first reflection hologram, the guard hologram having an angular bandwidth and a spectral bandwidth that are greater than the angular bandwidth and the spectral bandwidth of the primary image hologram, and having an optical density of 2.0 or greater. The guard hologram can be parallel fringe reflection hologram or a slant fringe reflection hologram.

Abstract: A holographic stoplight for a vehicle including a stoplight hologram, a source of playback illumination, and a transparent prism for supporting the stoplight hologram and for guiding the playback illumination to the stoplight hologram. The prism with the stoplight hologram is mounted in front of the rear window of a vehicle with the light source beneath the surface of the rear panel that is adjacent the rear window.

Abstract: The optical image properties of gelatin holograms are improved by reducing uneven shrinkage during chemical development. This is accomplished by introducing from 2 to 10 weight percent of a water soluble sizing agent into the gelatin. Suitable sizing agents include polyvinylpyrrolidone homopolymer and polyvinylpyrrolidone-vinyl acetate copolymers.

Abstract: A rear window mounted stoplight assembly for a vehicle including stoplight illuminating apparatus for producing stoplight illumination, and a scatter blocking hologram adjacent the stoplight illuminating apparatus for preventing scattered stoplight illumination from being viewable by the vehicle operator. In a particular embodiment, the stoplight illumination apparatus includes an image volume hologram and a source of playback illumination.

Abstract: A holographic stoplight assembly including a volume hologram having a recorded stoplight image secured adjacent to the inside surface of an automobile window. The volume hologram is selectively illuminated by an illumination source located out of the driver's rearward field of vision and forward of the hologram. Also disclosed is a method for recording a hologram for use in a holographic automobile stoplight system which includes the steps of recording the image of a stoplight in a first hologram, and then recording in a second hologram the playback image of the first hologram.