Monocular AR Projection Eyebox Expansion Using Exit Pupil Arrays
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Solution Overview
Problem
Existing augmented reality systems in monocular smart glasses face challenges in providing high-quality image projection with a wide field of view while maintaining a small form factor, accommodating various eye shapes and vision capabilities, and ensuring high power efficiency.
Innovation Solution
The image projection system configures a small exit pupil to create a large effective eyebox with a matrix of exit pupils, allowing for user-specific selection of an optimal optical window through an array of optical windows, using a scanner and image projector with a pupil multiplicator system to replicate exit pupils along orthogonal axes without angular displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a small form factor is used for monocular glasses, then weight and compactness are improved, but the field of view of the projected image is limited to about 20 diagonal degrees
Solution Approach 1:
The patent transforms the single exit pupil into a two-dimensional array of multiple exit pupils (e.g., 2x2 matrix), effectively expanding the optical output in the angular dimension without increasing the physical size of the glasses. This dimensional transformation allows the system to maintain a compact form factor while providing a wider effective field of view through multiple overlapping exit pupil positions.
Solution Approach 2:
The single exit pupil is segmented into multiple discrete exit pupils arranged in an array. Each exit pupil in the array can be independently positioned and optimized, allowing the system to cover a broader angular range while keeping each individual pupil small enough to maintain high image quality and resolution.
2Illumination intensity
If a small exit pupil is used to provide high brightness and resolution, then image quality is improved, but the eyebox size is reduced
Solution Approach 1:
The single small exit pupil is segmented into an array of multiple small exit pupils. While each individual pupil remains small to maintain high brightness and resolution, the collective array covers a larger area, effectively creating a large eyebox that can accommodate various eye positions and pupil sizes.
Solution Approach 2:
The exit pupil is transformed from a single point into a two-dimensional array, expanding the effective eyebox area without increasing the size of individual pupils. This dimensional expansion allows users with different eye characteristics to find an optimal viewing position within the array.
3Measurement precision
If optics (mirrors, lenses, and prisms) are added to create an optimized image, then image quality is improved, but the total system volume and weight increase
Solution Approach 1:
The patent extracts the exit pupil transformation function from the main optical path, implementing it through a separate array generation mechanism. This allows the primary optical system to remain compact while the exit pupil array provides additional image optimization without requiring bulky mirrors, lenses, or prisms in the main path.
Solution Approach 2:
Instead of using complex optical elements to create multiple images, the system creates copies of the exit pupil in an array configuration. Each pupil in the array provides the same high-quality image function, allowing the system to achieve wide field of view and accommodation for various users without adding voluminous optical components.
4Measurement precision
If the exit pupil is kept small to maintain resolution, then image sharpness is improved, but the system cannot accommodate various eye shapes and vision capabilities
Solution Approach 1:
The single exit pupil is segmented into an array of multiple pupils, where each pupil can serve users with different eye characteristics. Users with varying eye shapes, pupil sizes, and vision capabilities can select the optimal pupil from the array, maintaining high resolution while accommodating individual differences.
Solution Approach 2:
The exit pupil array provides universal compatibility by offering multiple viewing options within a single device. The system functions effectively for diverse users by allowing selection among multiple exit pupils, making the device adaptable to various eye shapes and vision capabilities without requiring multiple specialized optical systems.
Data Source
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AI summary
The present invention relates to a projection system for use in direct projection of images onto user's eye, the projection system comprising: a scanner operable for scanning a predetermined field of view with an image encoded light beam, an exit pupil of the scanner defining an exit pupil of the projection system; and an image projector configured to define an effective eyebox of predetermined dimensions, the image projector being configured and operable to transform the exit pupil of the scanner into an array of N said exit pupils being simultaneously projected on a user-selected partial eyebox being a region of the effective eyebox.