Large exit pupil wearable near-to-eye vision systems exploiting freeform eyepieces
Inventors
Jones, Frank • Bacque, James Benson • Hilkes, Robert • ERSDHADI, MEHDI AREZOOMAND • Harris, Mark • PAWSON, JON
Assignees
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Publication Number
US-11644671-B2
Publication Date
2023-05-09
Expiration Date
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.
Core Innovation
The invention relates to wearable near-to-eye (NR2I) vision systems that provide a wide horizontal field-of-view with high resolution using a single-element free-form wedge prism-lens in bioptic, laterally disposed configurations. The system is designed to achieve a large exit pupil, sufficient eye clearance, reduced vignetting, and controlled distortion, while targeting optical performance such as an MTF target.
To realize the wide horizontal field-of-view and the specified optical constraints, the system uses an optical folding, refracting, and reflecting path implemented as a three-surface prism-lens. The design methodology uses a rotated coordinate system that folds along the wider horizontal field-of-view axis, and it divides prism surfaces into regions associated with total internal reflection and transmission to control light propagation.
Stray-light suppression is addressed through baffles, opaque structures, and coatings or reflective coatings. The prism-lens design is supported by wavelength-selective modeling tied to microdisplay color pixels, and chromatic aberration is addressed by an under-corrected prism design combined with digital pre-warping per color channel based on computed full-field chromatic distortion maps.
System integration includes dual optical trains, one per eye, with microdisplay mounting on a temple-side location and a pivotable bioptic immersive configuration. Image shifting is performed based on range-finding data and eye tracking, where the object of gaze is established solely from the displayed image and a gaze direction derived from eye-tracking, and the resulting shift magnitude is used to maintain alignment while reducing diplopia and eye strain.
Claims Coverage
The provided claim set includes four independent claims for NR2I display systems that share common inventive structure: a casing-fixed microdisplay and free-form prism lens with internal reflections for NR2I coupling, a laterally disposed horizontal folding plane providing a wider field-of-view in the horizontal axis, and image shifting whose magnitude depends on range-finding data, with object-of-gaze determination solely from the displayed image and gaze direction established via eye-tracking. The independent claims further include selective coatings or region definitions on prism surfaces, spatial distortion limitation, and wavelength-specific simulation linked to color pixels.
Two internal reflections in a laterally disposed free-form prism-lens with horizontal-greater-than-vertical field of view
A first free-form prism lens fixedly attached in a first assembly has image light performing two internal reflections within the first free-form prism-lens before exiting for viewing, where the first microdisplay and the first free-form prism lens together present a field-of-view in a horizontal axis greater than a field-of-view in a vertical axis.
Gaze-dependent image shifting using range-finding data and eye-tracking derived gaze direction
Images upon the microdisplay are shifted by horizontal translation in combination with vertical translation, rotational translation, or vertical translation, where a magnitude of the shift is established in dependence upon range-finding data to an object of gaze, and the object of gaze is established solely in dependence upon the image displayed upon the microdisplay and a gaze direction established through eye-tracking of the eye aligned to the assembly.
Multi-surface free-form prism folding in a selected folding plane with horizontal-greater-than-perpendicular field of view
A free-form prism lens includes a first free-form surface transmitting light into the body, a second free-form surface reflecting light, and a third free-form surface at least partially reflecting light back toward the second free-form surface and out of the prism-lens, where the reflection at the second free-form surface and the at least partial reflection at the third free-form surface occur within a selected folding plane that is the horizontal axis.
Spatial distortion limitation at a maximum field angle
A spatial distortion at a maximum field angle of the free-form prism lens is less than 10%.
Selective coating/region definition on prism surfaces to block transmitted light
A coating blocks light transmitted through a second free-form surface, where the coated portion is a remainder of the second surface minus a predetermined region corresponding to where image light exits from the microdisplay toward the user's eye.
Selective reflective/transmissive partitioning on prism surfaces with optional non-overlapping coated sub-portions
On a second free-form surface, a first portion internally reflects light toward a third free-form surface while a second portion is transmitted to the user's eyes, and non-overlapping sub-areas of the first portion are optionally coated to reflect light or block external light.
Wavelength-specific prism-lens simulation linked to color pixels
A final design of the first free-form prism lens is based on a plurality of design simulations run at predetermined wavelengths, where each wavelength corresponds to a specific colour pixel in the first microdisplay.
Fixed assembly prism-lens coupling with casing-fixed microdisplay and image shifting
A prism lens and microdisplay are each fixedly attached to a casing, the images upon the microdisplay are coupled to an eye of a user via the prism lens, and images upon the microdisplay are shifted by horizontal translation in combination with vertical translation, rotational translation, or vertical translation, with shift magnitude established in dependence upon range-finding data.
Across the independent claims, the core inventive coverage centers on casing-fixed microdisplay-to-free-form-prism coupling with internal reflections within a selected horizontal folding plane to provide a wider horizontal field-of-view than vertical or perpendicular fields, together with gaze-dependent image shifting. The independent claims further cover establishing the object of gaze solely from the displayed image and a gaze direction determined through eye-tracking, determining shift magnitude from range-finding data, and narrower refinements including selective coatings or region definitions on prism surfaces, limiting spatial distortion, and linking prism design simulations to microdisplay color pixels.
Stated Advantages
Provides a field-of-view in a horizontal axis greater than a field-of-view in a vertical axis.
Provides reduced vignetting.
Controls distortion.
Targets a large exit pupil.
Provides sufficient eye clearance.
Targets chromatic aberration mitigation using prism and digital pre-warping tied to color channels.
Reduces diplopia and eye strain.
Documented Applications
Wearable near-to-eye (NR2I) vision systems, including bioptic immersive configurations, with temple-side mounting and dual optical trains, one per eye.
Gaze-dependent image shifting based on range-finding data and eye tracking to align image light with a user's eye and reduce diplopia and eyestrain.
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