Pupil Relay System for AR Waveguide Illumination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Laser scanning projectors face challenges in achieving efficient illumination of waveguides due to off-axis illumination, leading to vignetting and light loss, especially in compact augmented and virtual reality displays where a complex lens system is difficult to implement.
Innovation Solution
A laser scanning projection system that uses a combination of polarizing beam splitters and quarter waveplates to ensure on-axis illumination, allowing the waveguide to be positioned close to the scanner without interrupting the beam and enabling a compact design, with controlled exit pupil relay to prevent vignetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If off-axis illumination is used in laser scanning projectors, then the scanning mirror can be positioned to achieve a desired field of view, but the exit pupil becomes displaced from the input grating causing vignetting and light loss
Solution Approach 1:
A relay optics system comprising a first lens and a second lens is introduced as an intermediary between the laser scanning mirror and the waveguide. The first lens receives light from the scanning mirror and the second lens relays the exit pupil to coincide with the input grating on the waveguide, thereby eliminating vignetting while preserving the off-axis scanning capability and achieving both desired field of view and light efficiency
Solution Approach 2:
The relay optics are divided into separate lens components (first lens and second lens) that can be independently positioned and optimized. This segmentation allows the system to maintain compact form factor while achieving proper pupil relay and eliminating light loss through the intermediate optical stages
2Reliability
If a complex lens system is used to relay the pupil, then the exit pupil can be positioned at the desired location, but the device size and complexity increase making it unsuitable for compact head mounted displays
Solution Approach 1:
The patent extracts and eliminates unnecessary optical elements from the light path by using a simplified relay optics configuration. By carefully selecting the positions and focal lengths of only two lenses, the system achieves accurate pupil relay without requiring complex multi-element lens assemblies, thereby reducing device complexity while maintaining reliable pupil positioning
Solution Approach 2:
The relay optics system utilizes strategic positioning in three-dimensional space to achieve pupil relay with minimal components. By optimizing the spatial arrangement and distances between the scanning mirror, first lens, second lens, and waveguide, the system accomplishes accurate pupil positioning without requiring additional optical elements that would increase complexity
3Volume of moving object
If the waveguide is positioned close to the laser scanner, then the device can be made compact, but off-axis illumination interrupts the beam and causes vignetting
Solution Approach 1:
The relay optics system acts as an intermediary that bridges the gap between the laser scanner and waveguide. It allows the waveguide to be positioned close to the scanner for compactness while the relay lenses ensure the exit pupil coincides with the input grating, maintaining beam integrity and preventing vignetting despite the close proximity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures efficient coupling of light into the waveguide, reduces distortion, and allows for control of image size, enhancing the feasibility of laser scanning projectors in augmented and virtual reality headsets by maintaining light efficiency and compactness.
Implementation Method 1
a first polarising beam splitter, configured to receive the light from the laser source
Implementation Method 2
a first quarter waveplate, configured to receive the light from the first polarising beam splitter
Implementation Method 3
a laser scanner comprising a scanning mirror that is pivotably mounted, configured to receive the light from the first quarter waveplate and direct the light across an angular field of view, thereby to form an exit pupil
Implementation Method 4
a waveguide comprising an input, the input configured to receive the light from the first polarising beam splitter via the second polarising beam splitter
Data Source
AI summary
A laser scanning projection system for use in illuminating a waveguide of an augmented reality or virtual reality headset is disclosed. The laser scanning projection system comprises a laser source configured to emit light towards a pair of polarising beam splitters. The polarising beam splitters direct light onto a plurality of mirrors through a plurality of quarter waveplates. The laser scanning projection system further comprises a waveguide having an input configured to receive the light such that the exit pupil formed at the laser scanner is relayed into the waveguide.