Faceted Light Guide for Compact Eye Tracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional eye tracking mechanisms in near-eye display devices, such as HMDs, require complex optical arrangements that hinder the implementation of a small form factor due to the need for a substantial viewing distance between the eye and the display panel, leading to bulkiness and discomfort.
Innovation Solution
A faceted light guide assembly is used, which includes a transparent body with angled facets that internally reflect light towards an image sensor, reducing the eye tracking distance and allowing for a more compact design by positioning the image sensor outside the field of view, thereby minimizing the distance between the lens and the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional eye tracking mechanisms with complex optical arrangements are used, then eye tracking function is achieved, but device form factor increases and comfort decreases
Solution Approach 1:
The patent combines the eye tracking optical path with the display optical path by using the same light guide structure for both functions. The combiner surface integrates display light transmission and eye reflection collection, eliminating the need for separate optical components and reducing overall device volume.
Solution Approach 2:
The light guide structure serves multiple functions simultaneously: it guides display light to the user's eye, collects reflected light from the eye for tracking, and provides structural support. This multi-functionality reduces the number of components needed and compactes the device design.
2Measurement precision
If substantial viewing distance is maintained between eye and display panel, then eye tracking accuracy is improved, but device weight and awkwardness increase
Solution Approach 1:
The patent changes the optical path arrangement from a linear distance-based system to a multi-dimensional system using angled combiner surfaces. Light reflects at specific angles (e.g., 45 degrees) to achieve the necessary optical path length without requiring substantial physical distance, thereby reducing device weight while maintaining tracking precision.
3Reliability
If complex optical mechanisms are used to capture eye images, then eye tracking capability is achieved, but device complexity increases
Solution Approach 1:
The patent extracts the eye tracking function from the main display optical path by using a dedicated reflection collection path through the combiner surface. This separation allows the display system to remain simple while adding eye tracking capability through a minimal additional optical path that collects reflected light without interfering with display light transmission.
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 reduces the perceived weight and awkwardness of head-mounted displays, enhancing the user experience for virtual and augmented reality applications by providing a more compact and comfortable design without compromising the field of view or image quality.
Implementation Method 1
The second surface includes a combiner region having a plurality of facets generally arranged along a plane having a non-zero angle relative to the first surface. The facets are configured to reflect light internally through the body of the light guide toward the third surface of the light guide.
Implementation Method 2
A faceted light guide assembly is used, which includes a transparent body with angled facets that internally reflect light towards an image sensor, reducing the eye tracking distance and allowing for a more compact design by positioning the image sensor outside the field of view
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An eye tracking system includes a light guide including an eye-facing first surface, a second surface, a third surface, and a plurality of facets formed in the second surface. The facets reflect a portion of light incident on an eye into the light guide, which is positioned proximate to the eye and between the eye and a display. A surface of a compensator may be shaped complementary to the second surface of the light guide and placed proximate to the light guide. A camera or other image sensor is oriented toward the third surface of the light guide and captures an image based on internally reflected light. An IR light source may be included. The image sensor may be an IR image sensor. Based on the image, a pose of the eye is determined. A faceted light guide assembly may include a reflective coating adjacent the facets.