Eye Imaging With Diffractive Optics for Unobstructed HMD Views
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Solution Overview
Problem
Challenges exist in capturing high-quality images of the eye for gaze tracking and biometric identification in virtual and augmented reality systems without obstructing the user's view or causing image distortions due to the proximity and occlusion issues with conventional camera placements.
Innovation Solution
The use of off-axis camera assemblies combined with coupling optical elements, such as diffractive optical elements, to direct light from the eye into a substrate for imaging, allowing the camera to capture images without being directly in the user's field of view, using total internal reflection (TIR) and offset optical elements to facilitate imaging from a distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera assembly is placed close to the user's eye for imaging, then imaging quality and field of view are improved, but the camera obstructs the user's view of the surroundings
Solution Approach 1:
A transparent substrate is introduced as an intermediary element between the camera assembly and the user's eye. The substrate allows light from the eye to pass through to the camera while remaining transparent to the user, enabling the camera to be positioned close to the eye without obstructing the user's view of the surroundings.
Solution Approach 2:
The optical path is redirected into a different spatial dimension by using the substrate to capture light from the eye at an offset angle. This allows the camera to image the eye without being directly in the user's line of sight, effectively moving the imaging function to another dimensional plane while maintaining close proximity for high-quality imaging.
2Device complexity
If a camera assembly is placed directly in front of the eye for imaging, then optical path is simplified, but image distortions occur due to occlusion and proximity
Solution Approach 1:
The transparent substrate serves as a mediator that enables indirect imaging of the eye. By capturing light reflected from the eye's surface as it passes through the substrate, the system achieves accurate eye imaging without the distortions that would result from direct close-proximity placement of the camera.
Solution Approach 2:
The system creates a virtual image of the eye by capturing light that has reflected off the eye's surface. This optical copying approach allows the camera to record accurate eye images without requiring direct contact or close proximity that would cause distortion, effectively capturing a faithful representation of the eye through light reflection principles.
3Object-affected harmful factors
If the camera is positioned off-axis to avoid obstruction, then user's view is maintained, but the optical path becomes more complex requiring additional coupling elements
Solution Approach 1:
The transparent substrate performs multiple functions simultaneously: it allows light from the eye to pass through to the camera assembly, maintains transparency to prevent obstruction of the user's view, and provides a surface for optical coupling. This multi-functionality reduces the need for additional separate coupling elements, thereby limiting the increase in optical path complexity despite the off-axis camera positioning.
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
Enables high-quality eye imaging with increased field of view and reduced obstruction, allowing for effective gaze tracking and biometric identification while maintaining the user's unimpeded view of the surroundings.
Implementation Method 1
The first coupling optical element may be configured to deflect light at an angle to totally internally reflect (TIR) the light between the proximal and distal surfaces and toward the second coupling optical element
Implementation Method 2
The second coupling optical element may be configured to deflect light incident thereon at an angle out of the substrate
Data Source
AI summary
Examples of eye-imaging apparatus using diffractive optical elements are provided. For example, an optical device comprises a substrate having a proximal surface and a distal surface, a first coupling optical element disposed on one of the proximal and distal surfaces of the substrate, and a second coupling optical element disposed on one of the proximal and distal surfaces of the substrate and offset from the first coupling optical element. The first coupling optical element can be configured to deflect light at an angle to totally internally reflect (TIR) the light between the proximal and distal surfaces and toward the second coupling optical element, and the second coupling optical element can be configured to deflect at an angle out of the substrate. The eye-imaging apparatus can be used in a head-mounted display such as an augmented or virtual reality display.