Steven R. Mackara

Holographic optical element (HOE) imaging in DuPont holographic photopolymers

DuPont holographic photopolymers have been used to fabricate high quality holographic optical elements. The wide spectral sensitivity possible in these materials allows imaging near the desired HOE playback conditions. Multicolor imaging with ion and dye lasers using these materials is discussed. Mastering materials and methods are described for reflection and transmission HOE replication. HOE performance is compared to performance predicted by coupled- wave theory and HOE applications using these materials are described.

Holographic transmission elements using improved photopolymer films

Volume phase holographic gratings provide the high diffraction efficiency often required from holographic optical elements. In order to provide wide angular bandwidth, high index modulation is also required. A new addition to the family of Du Pont holographic photopolymer films has significantly higher index modulation for the grating spacings typical of holographic transmission elements. In this paper, the recording of volume phase transmission gratings in this holographic photopolymer is described. The dependence of holographic properties on exposure conditions, grating characteristics, and processing are discussed. The performance characteristics of holographic optical elements produced in this material are also presented.

Diffractive printing methods using volume holograms

A unique, proprietary, holographic printing technology has been demonstrated using DuPont OmniDexTM Holographic Recording Films which can incorporate multicolor, image individualization and anticounterfeiting functions into volume holograms. Starting with a monocolor volume hologram, we describe a process using simple existing photopatterning technologies to introduce imagewise selective colors into the monochrome hologram. In this process a latent image is recorded in our OmniDexTM Color Tuning Film. This latent image is transferred to a prerecorded hologram by lamination and developed by heating. Bright, multicolor holographic images were achieved with high resolution. The process flexibility and applications of this technology to graphic arts holography and security printing will be discussed.

Enhanced reflective liquid crystal displays using DuPont holographic recording films

Holographic reflectors with high brightness and excellent environmental stability have been produced using DuPont holographic films. The center wavelength, color bandwidth and viewing cone are defined for the optimal viewing performance. Measurement methods used to quantify holographically enhanced reflective LCD performance are presented. The test results show that holographic reflectors based on the DuPont OmniDex film experienced less than 1 percent brightness degradation under 70 degrees and 95 percent relative humidity for 200 hours, with no measurable color shift. Two examples of how this technology can be extended to enhance color LCDs are also presented.

Display applications for holographic optical elements

In the last several years, holographic elements have been introduced into a wide array of display applications. Holographic Reflectors are incorporated with liquid crystal displays to shift optimum viewing angle away form specular glare and raise brightness by concentrating light at a convenient viewing angle. Reflectors can be produced in blue, green, gold, red, or white colors. Denso GlassVision projection screens incorporate transmission holograms to efficiently direct projected light to the viewer in a screen that reverts to clear glass When the projection image is turned off. JVC has introduce da large-screen HDTV that uses a holographic color filter to separate blue, green, and red light from the illumination beam, and direct the sorted colors to the appropriate color pixel, raising brightness with a passive component. Most recently, HOE prototypes have been produced to improve the efficiency of portable liquid crystal color display. Front diffuser are affixed to the face of reflective color LCDs and direct output light from the LCD to the viewer at a convenient viewing angle in a concentrated view cone. Reflective Colors Filters are pixelated diffuse reflectors internal to the LCD structure and aligned to the LCD matrix. These reflective filters provide higher brightness, larger color gamut, and better color saturation including a holographic grating are under development to provide wider view angle in direct-view LCDs.