Using high-diffraction-efficiency holographic optical elements in a full-color augmented reality display system

Abstract

Holographic optical elements (HOEs) play an important role in augmented reality (AR) systems. However, the fabrication of full-color HOEs is difficult and the diffraction efficiency is low. In this paper, we use the time-scheduled iterative exposure method to fabricate full-color HOEs with high diffraction efficiency. Through this method, a full-color HOE with an average diffraction efficiency of 73.4% was implemented in a single photopolymer, the highest rate yet reported. In addition, the AR system is simulated by the geometric optics method combining k-vector circle and ray tracing and structured by combining laser micro-drop and high diffraction efficiency HOEs. A good color blending effect was achieved in a full-color AR system by using the reconstruction wavelength consistent with the recording light. It can present clear holographic images in a full-color AR display system.

Color gamut characteristics of diffractive-light guides of near-eye augmented reality glasses

“…The RSoft was employed for simulating the diffraction efficiency of the SRG, 31 while Kogelnik’s formula was applied to simulate the Bragg diffraction within an FOV of 20°, as depicted in Figure 5 . 23 This visualization underscores the fundamental disparity between SRG and VHOE. The former allows all colors to manifest at each viewing angle, albeit with non-uniform diffraction efficiency.…”

“…The second group comprises volume gratings and holograms, where thickness becomes a critical factor in influencing diffraction. 19 , 20 , 21 , 22 , 23 The diffraction from volume grating relies on constructive interference across the entire volume, leading to the imposition of the Bragg condition, which restricts diffraction along a specific direction with a designated wavelength. 24 , 25 , 26 Consequently, a volume grating can diffract incoming light into a split light with a rainbow-like structure, where each wavelength of the diffracted light corresponds to a specific incident angle determined by the Bragg condition.…”

Recent Applications of Optical Elements in Augmented and Virtual Reality Displays: A Review

“…Also note that if the free space reflective or transmissive combiner PPHOE has positive or negative optical power, we denote them as “lens PPHOE” for ease of explanation. Free space combiner PPHOEs are usually fabricated by illuminating a reference wave and a signal wave simultaneously onto a PP attached to a glass substrate. , This element is often used in OST AR NEDs, since it can function as a transparent mirror or lens that only diffracts the Bragg-matched light while transmitting others. Additionally, by using the off-axis scheme, the overall system size can be reduced, and the DC noises can also be avoided.…”