Phase volume holographic optical components for high-brightness single-LCD projectors

Abstract

Projection systems based on liquid-crystal displays (LCD's) offer new opportunities to display high-definition and large-size TV images. There are two types of LCD projector architectures: the 3-LCD architecture uses one LCD for each primary color, red, green, and blue, whereas a single-LCD configuration employs only one LCD paved with color filters. The single-LCD projector is simple and compact but suffers from a poor luminous efficiency because of losses in the color filters: each filter transmits only ~1/3 of the flux emitted by the lamp. To increase this optical efficiency, we propose to introduce volume holographic elements in the architecture of a single-LCD projector. Innovative systems are presented in which volume holographic elements realize the spatiochromatic illumination of the LCD. This illumination consists of selectively directing all the light that corresponds to a primary color, red, green, or blue, in the pixel addressed with the corresponding video composite signal and exploits the spectral selectivity and dispersion properties of volume holographic gratings and lenses. The two main advantages of such illumination are the suppression of the color filters and the recovery of the light lost in a classical architecture by absorption of the color filters. A complete luminous efficiency analysis of spatiochromatic illumination with volume holographic elements is presented. The achieved performances are compared with classical single-LCD projectors.

Ionic Liquids in Photopolymerizable Holographic Materials

“…The distribution of diffusing beads in the diffuser is nonuniform, which affects the performance of diffusion light. The surface-relief diffusers scatter the light by the microstructures thereon, e. g. microlens diffuser [67,68], random phase diffuser [69], deterministic diffractive diffuser [70] and holographic diffuser [71][72][73][74][75][76][77]. Much research has been focused on holographic diffusers, which were produced via exposure of the film of photopolymerizable holographic material to collimated light through a diffuser [72], dichromated gelatine [73], photopolymer [74][75][76] and azobenzene polymer [77] have been used to fabricate the diffusers.…”

Sol–Gel Derived Nanocomposites for Optical Applications

“…[116] Much research has been performed on holographic diffusers owing to their unique properties, such as controllable diffusion angle, directional property, variability of volume refractive index, and high transmittance. Hologram materials such as silver-halide sensitized gelatine, [117][118][119] dichromated gelatine, [120] photopolymers, [121] and azobenzene polymers [122] have been used to fabricate the diffusers. The modulation of the refractive index was visible using a phase-optical microscope as shown in Figure 17.…”

Optical Photopolymers: Design and Applications

“…For a three-color LCD projector system it is estimated that only 2 % of the light from the lamp reaches the display screen and for a single-color LCD panel projector the value drops to 0.8 %. [21] Approaches using a combination of dichroic mirrors, micro-optics, and a single LCD panel have been successfully applied to this problem but issues of the high cost of dichroics and sensitive alignment of the components remain. [22] Approaches using pixellated holograms have been demonstrated using diffractive or holographic components to replace the color filters and significantly improve (factor of 2±4) the light throughput of the overall system.…”

“…[22] Approaches using pixellated holograms have been demonstrated using diffractive or holographic components to replace the color filters and significantly improve (factor of 2±4) the light throughput of the overall system. [21,23,24] Recently, holographic approaches to more effective light management have been discussed for backlit LCDs [25] and reflective LCDs. [26,27] In these approaches the wavelength selectivity and controlled spectral bandwidth of the holographic optical element (HOE) have been used to effectively use and control the incident light.…”