Large exit pupil wearable near-to-eye vision systems exploiting freeform eyepieces

Abstract

Within applications for Near-to-Eye (NR2I) displays, irrespective of whether they are for short-term, long-term, low vision, augmented reality, etc., there is a conflicting tradeoff between user comfort, ease of attachment, minimizing intrusiveness and aesthetics which must be concurrently balanced with and are often in conflict with providing an optical vision system within the NR2I display that provides the user with a wide field of view and high image resolution whilst also offering a large exit pupil for eye placement with sufficient eye clearance. Embodiments of the invention address these issues and provide a high performance optical system through the design of the optical eyepiece design to overcome these limitations within a bioptic configuration with laterally disposed displays.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application claims the benefit of priority from U.S. Provisional Patent Application 62 / 374,208 filed on Aug. 12, 2016 entitled “Large Exit Pupil Wearable Near-to-Eye Vision Systems Exploiting Freeform Eyepieces”, currently pending, the entire contents of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]This invention relates to wearable NR2I vision systems and more particularly to providing wearable NR2I vision systems with wide field of view, high image resolution, large exit pupil for eye placement, sufficient eye clearance, and elegant ergonomic design.BACKGROUND OF THE INVENTION[0003]Wearable near-to-eye (NR2I) vision systems or NR2I displays are a class of wearable device that creates a display in front of the user's field of vision from an electronic display. The display may be transparent such that the viewer can view the external world and the projected electronic display simultaneously or opaque ...

AI Technical Summary

Benefits of technology

[0008]It is an object of the present invention to mitigate limitations within the prior art relating to wearable NR2I vision systems and more particularly to provide wearable NR2I vision systems with wide field of view, high image resolution, large exit pupil for eye placement, sufficient eye clearance, and elegant ergonomic design.

[0009]In accordance with an embodiment of the invention there is provided a near-to-eye (NR2I) display system comprising an assembly comprising a free-form prism lens, a microdisplay for projecting image-light onto a region of a first surface of said freeform prism-lens, said image light performing two internal reflections within the free-form prism-lens before exiting the free-form prism-lens for viewing by the user with an eye, wherein the microdisplay is fixedly held in position by said assembly relative to said first surface of the free-form prism lens and proximate a temple of the user nearest the user's eye viewing the projected image-light, such assembly having attachment features such that lateral motion of the assembly across the user's horizontal field of view when attached to a body of the NR2I system is made possible.

[0010]In accordance with an embodiment of the invention there is a provided near-to-eye (NR2I) display system further comprises a second assembly comprising a second free-form prism lens, a second microdisplay for projecting image-light onto a predetermined region of a first surface of said second freeform prism-lens, said image light performing two internal reflections within the second freeform prism-lens before exiting the second freeform prism-lens for viewing by the user with their other eye, wherein the second microdisplay is fixedly held in position relative to said first surface of the second free-form prism lens and proximate the user's other temple by said second assembly, such assembly having attachment features such that lateral motion of the second assembly across the user's horizontal field of view when attached to the body of the NR2I system is made possible allowing the positions and separation of the assembly and second assembly to be established in dependence upon the positions and the inter-pupil distance of the user's eyes.

[0011]In accordance with an embodiment of the invention there is provided a near-to-eye (NR2I) display system comprising an assembly comprising a free-form prism lens and a microdisplay for projecting image-light onto a predetermined region of a first surface of said freeform prism-lens, said image light performing two internal reflections within the free-form prism-lens before exiting the free-form prism-lens for viewing by the user with an eye, wherein the microdisplay is fixedly held in position by said assembly relative to said first surface of the free-form prism lens and proximate a temple of the user nearest the user's eye viewing the projected image-light, such assembly having attachment features such that vertical angular motion of the assembly across the user's vertical field of view when attached to a body of the NR2I system is made possible, in order to allow positioning of the display above the user's line of sight.

[0012]In accordance with an embodiment of the invention there is provided a near-to-eye (NR2I) display system comprising an assembly comprising a free-form prism lens and a microdisplay for projecting image-light onto a first surface of said freeform prism-lens, said image light projecting onto a second surface of said freeform prism-lens performing a first internal reflection to a third surface of the freeform prism-lens, a second internal reflection from the third surface towards a predetermined region of the second surface whereupon the light exits the freeform prism-lens towards the user's eye through said predetermined region; wherein external light is prevented from entering substantially all the second surface excluding said predetermined region through at least one of an applied coating to the second surface of the freeform prism-lens and opaque structures external to the freeform prism-lens.

Problems solved by technology

First of all, the exit pupil diameter (EPD) of most existing designs is typically from 4 to 8 mm, which essentially results in a limited eyebox size.

This makes it very challenging to design a system with a large exit pupil and long eye clearance distance.

As a result, prior art designs compromise the size of non-vignetted exit pupil diameter (about 6 mm) by allowing a significant amount of vignetting for large field positions, which compromises the effective eyebox size to about 8 mm at the designed eye clearance position.

Thirdly, the pixel size of the microdisplays used in most of the existing designs is typically 15 μm or larger.

In general, it is very challenging to design a freeform prism-lens eyepiece achieving low F-number and high optical resolution for a broad spectrum without adding additional elements for chromatic aberration correction.

With this type of plane-symmetry structure, it is very challenging to achieve a wider field of view for the folding direction than the direction with symmetry.

As a result, most of the freeform prism-lens-based NR2I optical systems mount the microdisplays above the user's eyebrow(s), which leads to a front-heavy system and compromises overall ergonomic design.

Rather, embodiments of the invention have a FOV in the folding direction is much wider than the non-folding direction, which makes a high-performance design very challenging.

A large pupil, however, often not only compromises the compactness and weight of the optical system, but also imposes limitations on the FOV due to the dramatically increased challenge of designing low F / # systems.

In designing NR2I systems, a large eye clearance is also desirable to accommodate users wearing eyeglasses, but it affects the compactness of the viewing optics.

In a freeform prism-lens eyepiece, however, the distortion can be very large and irregular if it is left without any constraints.

However, this design constraint means that the full correction of chromatic aberrations due to optical dispersion is not feasible.

This is often a limiting factor for designing a freeform prism-lens with high optical resolution for a broad optical spectrum such as the full human visual spectrum.

Typical NR2I systems provide the image at a fixed focal depth of infinity, and the IPD of the images are fixed, which may result in diplopia (double-vision) or eye-strain when viewing close objects, as the eyes are not operating in a “natural” manner for close objects.

The function that relates distance to the object to the number of pixels by which to digitally offset the image may be simple or complex.

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