Reflective Periscope Layout for XR Beam Parallelism Measurement
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Solution Overview
Problem
Existing optical measurement devices, such as optical collimators, wavefront sensors, and interferometers, are inadequate for accurately measuring optical parallelism and virtual imaging distances in extended reality (XR) devices, particularly in Exit Pupil Expansion (EPE) systems, due to limited field of view, sensitivity to environmental changes, complexity, and inability to sample optical rays from different eye box locations or pupils.
Innovation Solution
An optical system comprising an enclosure with a pair of apertures and mirrors is used to measure optical parallelism and virtual imaging distances, employing reflections to ensure high precision and stability, eliminating alignment issues and motion errors, and providing diffraction-limited angular resolution for accurate parallelism and VID measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical collimator is used to measure light rays, then it can produce a parallel beam of light for optical alignment, but it has a single optical aperture which limits it to measuring only a single beam of light rays
Solution Approach 1:
The optical collimator is divided into multiple independent optical apertures (first aperture and second aperture), each capable of receiving and measuring light rays separately. This segmentation allows simultaneous measurement of multiple beams from different eye box locations while maintaining the parallelism measurement capability of each individual aperture.
2Measurement precision
If an optical collimator with small field of view is used, then it can provide precise measurement of a single beam, but it cannot cover different eye box locations or pupils
Solution Approach 1:
The measurement capability is extended from a single beam to multiple beams by adding the dimension of spatial multiplicity through multiple apertures. The first aperture measures light rays from a first eye box location while the second aperture measures light rays from a second eye box location, effectively expanding the measurement coverage across different spatial positions without compromising the precision of individual measurements.
3Measurement precision
If wavefront sensors or interferometers are used for measurements, then they can provide detailed optical information, but they are sensitive to environmental changes such as vibration, movement, acoustic noise, air turbulence, temperature, and humidity
Solution Approach 1:
The patent replaces complex mechanical and environmental-sensitive measurement systems (wavefront sensors, interferometers) with a simpler optical collimator-based system that uses parallel light ray measurement. This substitution eliminates sensitivity to environmental factors such as vibration, acoustic noise, and temperature changes while maintaining the ability to measure optical parallelism and virtual imaging distances accurately.
4Ease of operation
If existing optical measurement devices are used, then they can provide some measurement capability, but they introduce alignment issues and motion errors
Solution Approach 1:
The patent merges the measurement functions into a single integrated optical collimator system with multiple apertures that simultaneously measures light rays from different eye box locations. This unified approach eliminates the need for separate measurement devices and their associated alignment procedures, thereby removing alignment issues and motion errors while maintaining ease of operation.
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
The optical system enables precise measurement of optical parallelism and virtual imaging distances in XR devices, ensuring high accuracy and eliminating color issues, while maintaining diffraction-limited performance across various aperture sizes and virtual imaging distances, enhancing the immersive experience by reducing distortions and aberrations.
Implementation Method 1
employing reflections to ensure high precision and stability
Data Source
AI summary
An optical system for measuring a parallelism of rays of a light emitter and virtual imaging distances of the light emitter, including an enclosure including a front end and a rear end, a pair of apertures configured to be disposed on the front end of the enclosure on a central plane, a pair of first mirrors disposed interior of the enclosure; and a second mirror disposed interior of the enclosure, wherein the pair of apertures are configured to allow two sets of rays into the enclosure at the pair of first mirrors before being directed to the second mirror which redirects them to be cast as a first and second spots on an imaging plane, wherein a parallelism of the two sets of rays is based on a correspondence of a distance between the first and second spots with a distance between the two sets of rays.