Wavelength-Multiplexed Holographic Optical Element for Eye Tracking in Scanning Laser Projectors
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Solution Overview
Problem
Wearable heads-up displays face challenges in integrating eye tracking functionality without increasing the size and bulk of the device, as existing systems require multiple dedicated components with stringent positioning requirements.
Innovation Solution
A scanning laser projector with an integrated eye tracker that uses a wavelength-multiplexed holographic optical element to redirect both infrared and visible light, allowing for eye tracking with minimal additional components and maintaining a compact form factor, including an infrared laser diode, a scan mirror, and an infrared detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple dedicated components are used for eye tracking, then eye tracking functionality is achieved, but device size and bulk increase
Solution Approach 1:
The patent combines eye tracking functionality with the existing scanning laser projection system by using the same scan mirror and optical path for both functions. The infrared light source and detector are integrated into the existing device architecture, merging two separate functions (projection and eye tracking) into a unified system that shares common components.
Solution Approach 2:
The scan mirror serves dual purposes: it scans visible light for image projection and scans infrared light for eye tracking. The optical splitter enables the system to handle both visible and infrared wavelengths through the same optical path, making the system multi-functional without requiring separate dedicated components for each function.
2Adaptability or versatility
If dedicated eye tracking components are added, then eye tracking is enabled, but device complexity increases
Solution Approach 1:
The patent merges eye tracking components with the existing projection system components. The infrared light source is integrated alongside the visible light laser diodes, and the infrared detector shares the same optical path and processing electronics as the projection system, reducing overall system complexity.
Solution Approach 2:
The optical splitter and scan mirror serve multiple functions: they direct visible light for projection and infrared light for eye tracking simultaneously. This multi-functionality reduces the need for separate dedicated components, thereby reducing system complexity while maintaining both functionalities.
3Adaptability or versatility
If conventional eye tracking systems are integrated, then eye tracking functionality is achieved, but positioning precision requirements become stringent
Solution Approach 1:
By merging eye tracking with the existing scanning projection system, the patent eliminates the need for separate positioning mechanisms. The scan mirror's established positioning system, already optimized for projection, is reused for eye tracking, thereby maintaining functionality while reducing positioning precision requirements.
Solution Approach 2:
The optical splitter and scan mirror are designed to handle both visible and infrared wavelengths through the same optical path with a single positioning system. This universal design approach allows one positioning mechanism to serve dual purposes, reducing the stringency of positioning requirements compared to separate dedicated systems.
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 eye tracking functionality in wearable heads-up displays with minimal impact on size and form factor, allowing for efficient image projection and gaze direction tracking without compromising the device's aesthetics or functionality.
Implementation Method 1
a wavelength-multiplexed holographic optical element aligned to receive both the infrared light and the visible light reflected from the scan mirror and to redirect both the infrared light and the visible light towards an eye of a user
Implementation Method 2
the wavelength-multiplexed holographic optical element includes a first hologram that is responsive to the visible light and unresponsive to the infrared light and a second hologram that is responsive to the infrared light and unresponsive to the visible light
Implementation Method 3
a scan mirror aligned with an output of the laser module to receive both the infrared light and the visible light and to controllably reflect both the infrared light and the visible light
Implementation Method 4
an infrared detector aligned to receive at least a portion of infrared light reflected from the eye of the user
Implementation Method 5
a laser module including an infrared laser diode to output an infrared light and at least one visible light laser diode to output a visible light
Data Source
AI summary
Systems, devices, and methods that integrate eye tracking capability into scanning laser projector (“SLP”)-based wearable heads-up displays are described. An infrared laser diode is added to an RGB SLP and an infrared photodetector is aligned to detect reflections of the infrared light from features of the eye. A holographic optical element (“HOE”) may be used to combine visible light, infrared light, and environmental light into the user's “field of view.” The HOE may be heterogeneous and multiplexed to apply positive optical power to the visible light and zero or negative optical power to the infrared light.