Precision Holographic Optical Elements in Bayfol~? HX Photopolymer

摘要

The versatility of Volume Holographic Optical Elements (vHOE) is high, especially because of their tunable angular and spectral Bragg selectivity. Those unique lightweight, thin and flat optical elements are enabled by the new instant developing photopolymer film Bayfol~? HX technology, which allows to mass produce cost effective diffractive optics due to its simplified and robust holographic recording process. From a pure scientific point of view volume holography is well established. In practice though, commercially available optical design software is not adapted to handle the specific characteristics of photopolymer diffractive optical elements and their recording. To achieve high quality vHOE precision optics, the recording setup needs to accommodate several aspects that will be covered in this paper. We report on means how to deal with photopolymer shrinkage and average refractive index changes of the recording media. An important part in diffractive optics design is the compensation of different conditions between the holographic recording setup and in a final product containing the vHOE. Usually substrates might need to be changed (in material, in refractive index) as well the illumination sources are using incoherent light having angular and spectral emission profiles with finite bandwidth. Recently special in- and out-coupling vHOEs are becoming attractive e.g. in near eye displays and in compact lighting devices. We will report on design considerations and adjustments to the recording condition for a specific in-coupling vHOE and demonstrate the effects of pre-compensation on this example.