Abstract: A holographic head-up display having first and second superimposed reflection holograms supported by a vehicle windshield, and first and second playback sources respectively associated with the first and second reflection holograms and positioned such that reflection by the windshield of playback illumination from one playback source is toward the other playback source. In particular, the first and second playback sources are configured such that the centerlines of the playback beams provided by the first and second playback sources are coplanar in a common plane that is substantially normal to the holograms, with the centerlines intersecting generally in the hologram layers and having substantially the same angle of incidence on the hologram layers as measured relative to normal in the common plane.

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 reflection hologram structure including a transparent substrate, and a pattern of shielded hologram containing regions and transparent regions disposed on the transparent substrate, the pattern being unresolvable to the viewer. The shielded hologram containing areas comprise hologram subregions and shielding subregions overlying the hologram subregions. The shielding subregions comprise for example, opaque regions or partially illumination transmissive regions.

Abstract: A method is disclosed for forming a multi-layer holographic device 22. A first hologram is formed on a major surface of a substrate 14. The first hologram is desensitized to prevent interaction with a second subsequently formed hologram. The second hologram is formed conterminous with said first hologram.

Abstract: A disk cover is provided with a reflection-type hologram assembly having multiple exposure images therein. The sun or an artificial light source illuminates the hologram assembly as it rotates as a result of the body moving. The exposure images are successively reconstructed to produce a single image that may be remotely positioned from and stationary relative to the rotating disk cover.

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 pulsed laser provided a pulsed incident beam which impinges a recording assembly which includes a glass substrate and a recording film adhered thereto. The pulse can be singular or multiple. In either event, the duration of each pulse of light is controlled in such a fashion so that the pulse is long enough to enable it to reflect off of a reflecting element to thereby produce a primary reflected beam. In the recording film, the primary reflected beam can interfere with the incident beam to produce the interference pattern in the film. However, the pulse is not of such a duration to allow a noise reflected beam, such as one from a glass-air interface, to pass through the recording film and interfere with the incident beam or primary reflected beam while those beams are still present. Thereby, noise holograms which might otherwise be recorded in the film are precluded while allowing the primary hologram to be recorded.

Abstract: A filter device 10 and method of making the same is disclosed. The device comprises holographic means 12 for diffracting optical radiation of a first predetermined range of wavelengths, and optical radiation filter means 14 for filtering optical radiation of a second predetermined range of wavelengths. The optical radiation filter means is coupled with the holographic means.

Abstract: A fiber optic point source is utilized to generate a first wavefront which is intersected with a second wavefront to form a desired interference pattern in a recording medium. The point source is moved relative to the recording medium during exposure in order to reduce multiple order scattering noise, and to provide a relatively large translational motion which is gradual and generally follows an angular scanning motion of the fiber optic point source.

Abstract: A fiber optic point source is utilized to generate a first wavefront which is intersected with a second wavefront to form a desired interference pattern in a recording medium. The point source is moved relative to the recording medium during exposure in order to reduce multiple order scattering noise, and a feedback monitoring system permits determination of portions of the recording medium requiring increased exposure.

Abstract: Noise is reduced in computer generated holograms (CGH's) by a method of overexposure. The CGH is used to make a master hologram. The master hologram is then used to make a copy from which a succession of other copy holograms is made. Each successive copy hologram is exposed less than the prior ones while increasing brightness uniformity. Consequently, a decreasing amount of change in exposure is required to reach 100% efficiency. The number and orientation of the copy holograms is incorporated into the design of the final optical element. The final hologram is not overexposed, since the amount of exposure has been reduced from the earlier holograms, and can be used in complex optical power systems.

Abstract: A method for treating permeable plastics and other porous materials to provide solid barriers within the materials that reduce permeability. One method involves migrating a first gas reactant into the material and migrating a second reactant into the material wherein the first and second reactants react at a reaction interface to form a solid reaction product which provides reduced gas permeability for the material. Embodiments are disclosed in which gaseous reactants are migrated from opposite sides of the material to form an internal gas impermeable barrier. Embodiments are also disclosed where the reactants are sequentially migrated into the material to produce gas impermeable barriers. Swelling of the materials prior to treatment with reactants is also disclosed in order to maximize permeation and reactant migration.

Abstract: An improved rearview mirror and process for producing the same is provided wherein an elongated substrate member is configured for attachment to the interior of a windshield. The substrate member supports an image retaining coating defining a holographic reflective surface that is configured to be substantially normal to the line of sight of the driver despite the slope of the windshield. As a result, a thin distortion free mirror can be provided with an expanded line of sight for the driver.

Abstract: A method and apparatus of exposing a hologram to reduce spurious noise holograms. The exposure light source is moved relative to a recording module within predetermined distances that will ensure a blurring of the fringes of a noise hologram that is formed at a distance from a primary hologram while substantially not affecting the primary hologram. The controlled relative movement of the exposure source and the recording module within predetermined limits provide a considerable improvement in reducing the efficiency of spurious noise holograms.

Abstract: High side lobes shown in a hologram efficiency curve are suppressed by reducing the effective sensitivity of a holographic recording medium by a plurality of film layers of gelatin such that there is a continuous increase in sensitivity toward the center of the layers. This makes the recording medium more spectrally selective and increases the "see-through" characteristic. A holographic fringe pattern with a normally uniform modulation recorded in such holographic medium layers will produce a hologram having a modulation in refractive index which is virtually zero at the surfaces and which increases toward the center of the medium. The layers in the recording medium can have varying degrees of photosensitivity. However, when combined, the layers provide an overall sensitivity which can be depicted as a generally sinusoidal curve. The generally smooth transition in sensitivity from one layer to the next is largely achieved by the mixing of layers at their interfaces.

Abstract: A system for monitoring intensity before, during, and after holographic exposure includes a monitoring assembly within an exposure beam and intermediate a light source and a hologram recording assembly. With the monitoring assembly in the exposure beam, a monitoring beam is produced that is directed towards detection elements located outside of the exposure beam. At the same time, the monitoring assembly allows the exposure beam to pass therethrough and onto the hologram recording assembly. The monitoring assembly may include a reflection hologram with an effective shape which is different from the supporting substrate, or glass substrates with an internal reflecting surface. In either event, the exposure beam remains undistorted. The spatial arrangement among the light source, hologram recording assembly, and detection elements are such that a reflected beam from the hologram recording assembly is directed away from the detection elements to avoid incorrect intensity monitoring.

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 computer generated diffraction grating which exhibits multiple order scattering noise is illuminated by a point source to generate a first wavefront which is intersected with a second wavefront to form a desired interference pattern in a recording medium. The point source is moved relative to the recording medium during exposure in order to reduce multiple order scattering noise.

Abstract: A hologram recording assembly includes a transparent, absorbent member supported on a substrate. The transparent member is positioned to be directly incident to an exposure beam. The transparent member is out of moisture equilibrium during an exposure time. Consequently, the transparent member increases or decreases in thickness depending on a moisture difference between it and the environment. As the thickness changes, a phase shift in the light reflections within the recording assembly blurs spurious holograms while leaving the desired hologram intact.

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.