Design of an optical see-through head-mounted display with a low f-number and large field of view using a freeform prism

Abstract

It has been a challenge to design an optical see-through head-mounted display (OST-HMD) that has a wide field of view (FOV) and low f-number (f/#) while maintaining a compact, lightweight, and nonintrusive form factor. In this paper, we present an OST-HMD design using a wedge-shaped freeform prism cemented with a freeform lens. The prism, consisting of three freeform surfaces (FFSs), serves as the near-eye viewing optics that magnifies the image displayed through a microdisplay, and the freeform lens is an auxiliary element attached to the prism in order to maintain a nondistorted see-through view of a real-world scene. Both the freeform prism and the lens utilize plastic materials to achieve light weight. The overall dimension of the optical system per eye is no larger than 25 mm by 22 mm by 12 mm, and the weight is 8 g. Based on a 0.61 in. microdisplay, our system demonstrates a diagonal FOV of 53.5 degrees and an f/# of 1.875, with an 8 mm exit pupil diameter and an 18.25 mm eye relief.

Design of light field head-mounted display

“…In the final design stage, in order to balance the optical performance of the system across the sampled fields, an automatic image performance balancing algorithm is used to further improve and balance the system performance. We have discussed all the details of the design strategies and optimization constraints in [15] [16]. We have demonstrated a diagonal FOV of 53.5° and an F/# of 1.875, with an 8mm exit pupil diameter and an 18.25mm eye relief.…”

“…It is determined by the angle resolution, the number of light beams entering eye pupil, the spatial resolution and the position of the object displayed. In order to obtain higher angular resolution, the best image plane of eyepiece can be away from the plane of MSA and this structure is similar to that of "Plenoptic 2.0" camera proposed in [15]. In order to reduce the crosstalk of light field, taking microlenses as an example, microdisplay should be imaged by the microlenses on the best image plane of eyepiece.…”

Augmented reality using holographic display

“…In order to combine digital world and the physical world, AR devices use couplers to integrate the light from environment and the display. Di erent kinds of couplers are commercially used, they can mainly classify into three groups: half-mirror or prism used by Google Glass; Free-form prism used by military helmet; waveguide coupler used by Hololens [3,4].…”

Portable waveguide display system with a large field of view by integrating freeform elements and volume holograms

“…There are many approaches such as using prisms [3][4][5], projection systems [6][7][8], deformable membrane mirrors [9][10][11], retinal scanning [12][13][14][15], hybrid diffractive-refractive lenses [16,17], and optical waveguides [18][19][20][21][22][23][24] to realize a seethrough display and the most promising approach is an optical waveguide.…”