Short period holographic structures for backlight display applications

Roberto Caputo,Hugo J Cornelissen,Dick K G De Boer,Luciano De Sio,Eefje J Hornix,Martin J J Jak

doi:10.1364/oe.15.010540

Abstract

The use of holographic structures is promising for the realization of efficient systems in backlight applications for displays. By applying surface relief gratings on top of a side-lit lightguide we realize a backlight that avoids the use of color filters. The grating is used as a light outcoupling and color-separating element. The demands for this grating are stringent and calculations have been performed to meet them. A prototype backlight, including the grating structure, has been assembled and characterized. Results of experiments are discussed.

Highlights

In the last few years, a lot of attention has been devoted to the realization of new devices based on holographic diffractive structures
An innovative way for achieving this result has been proposed by Taira et al, [8] who demonstrated how the color-dispersion power of a diffraction grating can be efficiently employed to avoid the use of color filters
The lightguide with the grating on top was placed in a side-lit configuration with a cold-cathode fluorescence lamp (CCFL) and a mirror at the other end of the lightguide

Summary

Introduction

In the last few years, a lot of attention has been devoted to the realization of new devices based on holographic diffractive structures. These diffractive elements can be implemented in many configurations. In this paper we consider the design and realization of a high quality short-pitched diffraction grating used for improving the efficiency of backlit displays. An innovative way for achieving this result has been proposed by Taira et al, [8] who demonstrated how the color-dispersion power of a diffraction grating can be efficiently employed to avoid the use of color filters. Since the percentage of light absorbed in these filters can be estimated to be 65-70%, there could be a considerable advantage in designing and adopting diffractive structures for display applications. In another work by Xu et al [10], a birefringent grating was considered and the advantages of polarized outcoupling were studied

Design of a grating for a backlight system

Configuration of the backlight system

Experimental evaluation of a working prototype

Evaluation of the backlight system

Conclusions