Design and fabrication of freeform holographic optical elements

Abstract

Holographic optical elements (HOEs) have a wide range of applications, including their emerging use in virtual and augmented reality displays, but their design and fabrication have remained largely limited to configurations using simple wavefronts. In this paper, we present a pipeline for the design, optimization, and fabrication of complex, customized HOEs that enhances their imaging performance and enables new applications. In particular, we propose an optimization method for grating vector fields that accounts for the unique selectivity properties of HOEs. We further show how our pipeline can be applied to two distinct HOE fabrication methods. The first uses a pair of freeform refractive elements to manufacture HOEs with high optical quality and precision. The second uses a holographic printer with two wavefront-modulating arms, enabling rapid prototyping. We propose a unified wavefront decomposition framework suitable for both fabrication approaches. To demonstrate the versatility of these methods, we fabricate and characterize a series of specialized HOEs, including an aspheric lens, a head-up display lens, a lens array, and, for the first time, a full-color caustic projection element.

Augmented reality and virtual reality displays: emerging technologies and future perspectives

“…Two major types of diffractive optics are HOEs based on wavefront recording and manually written devices like surface relief gratings (SRGs) based on lithography. While SRGs have large design freedoms of local grating geometry, a recent publication 19 indicates the combination of HOE and freeform optics can also offer a great potential for arbitrary wavefront generation. Furthermore, the advances in lithography have also enabled optical metasurfaces beyond diffractive and refractive optics, and miniature display panels like micro-LED (light-emitting diode).…”

“…Therefore, both incoupler and out-coupler are usually reflective types. The gradient efficiency can be achieved by space-variant exposure to control the local index modulation 186 or local Bragg slant angle variation through freeform exposure 19 . Due to the relatively small angular bandwidth of PPG, to achieve a decent FoV usually requires stacking two 187 or three 188 PPGs together for a single color.…”

A Multi-Plane Augmented Reality Head-Up Display System Based on Volume Holographic Optical Elements With Large Area

“…This method can effectively solve the aberration problem of the curved HOE. The Facebook reality laboratory research has proposed a design and fabrication method for freeform holographic optical elements [28]. This method has better design freedom, and can use optimization algorithms to correct the aberration of the curved HOE based on holographic printing.…”

Learned holographic light transport

“…The topic of light transport plays a crucial role in formulating the basis of various domains including traditional computer graphics [12], architecture [13], biomedical imaging [14], nonline-of-sight imaging [15], three-dimensional printing [16], visible light communications [17], holographic recording [18], computational displays [19], eye prescription correction [20], eyegaze tracking [21], ophthalmology [22] and many more. Although we cover only display technologies in this work, an accurate representation method of light transport can potentially pave the way towards enhancements in many other highlighted applications.…”