Eye Tracking Optical System for Compact Head-Mounted Displays
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Solution Overview
Problem
Existing image display apparatuses, such as head-mounted displays, face challenges in reducing size while maintaining tracking accuracy and immersion, often requiring additional illumination systems that increase size and obstruct the user's view.
Innovation Solution
An image display apparatus that includes a light source section emitting image display light and conjugate light, an optical system projecting these lights onto a user's pupil and surrounding areas, a detector capturing reflected light, and a controller adjusting the image position based on detected reflections, allowing for precise tracking without additional light sources or pattern generators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If illumination using infrared light is arranged around the frame for eye tracking, then tracking function is enabled, but the eyewear becomes larger in size
Solution Approach 1:
The patent combines the illumination function and eye tracking detection function into a single integrated structure. The illumination unit emits infrared light while the detection unit captures reflected light from the user's eye, eliminating the need for separate illumination systems and reducing overall device size.
Solution Approach 2:
The frame structure serves multiple functions: it provides structural support, houses the illumination unit, and contains the detection unit. This multi-functional design reduces the need for additional components and minimizes the volume of the eyewear.
2Reliability
If frame width is increased to accommodate illumination system, then tracking is enabled, but sense of immersion is reduced due to obstructed view
Solution Approach 1:
The illumination and detection units are positioned in specific localized areas of the frame rather than requiring a complete frame structure. This allows tracking functionality while maintaining large optical windows for the user's view, preserving the sense of immersion.
3Measurement precision
If additional optical system is added to generate desired pattern for irradiation onto eyeball, then tracking precision is improved, but device size increases
Solution Approach 1:
The patent merges the illumination pattern generation and detection functions into the existing optical path. The illumination unit generates the necessary light patterns while the detection unit captures reflected light, eliminating the need for separate additional optical systems.
Solution Approach 2:
The illumination unit serves dual purposes: it provides illumination for the display and generates the light patterns needed for eye tracking. The detection unit utilizes the reflected illumination light for tracking, making the system self-sufficient without requiring additional dedicated tracking components.
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 enables a smaller image display apparatus with improved tracking accuracy, eliminating the need for additional illumination and maintaining user immersion by using a conjugate light system that secures a fixed angular relationship between image display and conjugate lights.
Implementation Method 1
an optical system that projects the image display light emitted by the light source section onto a pupil of an eye of a user
Implementation Method 2
a detector that detects reflected light that corresponds to the conjugate light projected by the optical system to be reflected off the portion around the pupil
Data Source
AI summary
An image display apparatus that makes it possible to improve the tracking accuracy, while making the image display apparatus smaller in size. An image display apparatus includes a light source section that emits image display light OL used to display an image, and light CL conjugate to the image display light OL; an optical system that projects the image display light OL emitted by the light source section onto a pupil of an eye of a user, and projects the conjugate light CL emitted by the light source section onto a portion around the pupil of the eye of the user; a detector that detects reflected light that corresponds to the conjugate light CL projected by the optical system to be reflected off the portion around the pupil; and a controller that controls a position of a display-target image on the basis of the reflected light detected by the detector.