Selective Couplers Based on Multiplexed Volume Holographic Gratings for Waveguide Displays

Maria Shishova,Dmitrii Lushnikov,Alexander Zherdev,Sergey Odinokov,Vladimir Venediktov,Yohan Kim

doi:10.3390/photonics8070232

Abstract

Diffraction waveguides are widely used in augmented reality devices as information display systems for the introduction of data into the human visual field in order to supplement information about the world around us. This paper formulates the principles of radiation conversion in diffraction waveguides made of photo-thermo-refractive glass on the basis of multiplexed volume holographic gratings, and the advantages and disadvantages of high spectral-angular selectivity are analyzed. In the optical scheme, each of the superimposed volume holographic gratings in the diffraction waveguide forms a corresponding part of the composite angular field of view of the augmented reality device. A proposed mathematical model based on angular multiplexing made it possible to synthesize the diffraction optical element for a new type of diffraction waveguide made from photo-thermo-refractive glass and to create a prototype with an angular resolution of at least 3.0 ± 0.5′, with a brightness change in the image of less than 20% and with a composite angular field of view of 32°.

Highlights

Augmented reality devices are widely used as information display systems with an aim of introducing into the human visual field any data that complements the information about the world around us
When using volume diffraction gratings in PTR glass, only angular multiplexing allows expansion of the effective angular field of view provided by a single diffraction grating, as shown in Figure 7a,b for monochrome green and multicolor implementation, respectively
The action of each sequential multiplexed volume holographic gratings (MVHGs) can be interpreted as a static implementation of the “rolling K-vector” conditions used in switchable diffraction optical elements (DOE) [7]

Summary

Introduction

Augmented reality devices are widely used as information display systems with an aim of introducing into the human visual field any data that complements the information about the world around us. Such devices are necessary for supplying visual instructions during manual operations in medicine, construction and education, as well as in everyday life for expanding smartphone functionality. Diffraction waveguides are commonly used for implementation of augmented reality head-mounted displays [1,2]. Most of these are glass plane-parallel plates where radiation propagates by total internal reflection (TIR), and diffraction gratings are used as couplers to input, redirect and output the light. Slanted surface gratings [4] are implemented into augmented reality displays by Microsoft HoloLens, Magic Leap, WaveOptics, and Dispelix and they can have a diffraction efficiency up to 80%, but the manufacturing requires a complex and expensive technological process

Methods

Results

Conclusion