MEMS Eye-Tracking Optics for Low-Glare Waveguide Displays
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Solution Overview
Problem
Conventional eye-tracking systems for head-mounted display devices add bulk, weight, and optical complications, and can cause glare due to stray light, making them costly and inefficient for ergonomic design and user experience.
Innovation Solution
An eye-tracking system that uses a partially transparent visible light waveguide with infrared light path configurations, including MEMS scanning mirrors and strategically positioned mirrors to direct infrared light on-axis or off-axis relative to visible light, reducing the need for additional components and minimizing light interference with the user's view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an eye-tracking system is added to the HMD device, then eye-tracking functionality is achieved, but the device adds weight and bulk
Solution Approach 1:
The patent combines the eye-tracking system with the existing HMD optical components by integrating the infrared light source and sensor into the waveguide structure. The MEMS scanning mirror is positioned within the existing optical path, allowing eye-tracking functionality to be achieved without adding separate, bulky components. This merging approach enables the eye-tracking system to share the HMD's structural framework, thereby reducing overall weight.
Solution Approach 2:
The waveguide structure serves multiple functions: it guides visible light for the display and simultaneously guides infrared light for eye-tracking. The MEMS scanning mirror performs dual roles by directing both display light and infrared tracking light. This multi-functionality eliminates the need for dedicated separate components, reducing the overall weight and bulk of the device.
2Adaptability or versatility
If an eye-tracking system is added to the HMD device, then eye-tracking functionality is achieved, but the device complexity increases
Solution Approach 1:
The patent merges the eye-tracking optical path with the existing HMD waveguide structure. The infrared light source, MEMS scanning mirror, and sensor are integrated into the same physical framework that supports the visible light display. This consolidation reduces the number of separate components and simplifies the overall system architecture while maintaining eye-tracking functionality.
Solution Approach 2:
The waveguide acts as an intermediary structure that carries both visible light for display and infrared light for eye-tracking. By using the existing waveguide as a shared medium, the patent avoids creating separate complex optical paths, thereby reducing system complexity while achieving the desired functionality.
3Adaptability or versatility
If conventional eye-tracking systems are used, then eye-tracking is achieved, but they cause glare and obstructions to the user's field of view
Solution Approach 1:
The patent uses different wavelengths of light for different purposes: visible light for the display and infrared light for eye-tracking. The infrared light is invisible to the human eye, so it does not cause glare or obstruct the user's field of view. This local quality differentiation (using different spectral regions for different functions) eliminates the harmful effects while maintaining functionality.
Solution Approach 2:
The patent transitions from using visible light for both display and tracking to using infrared light for tracking. This wavelength change (from visible spectrum to infrared spectrum) allows the tracking light to be imperceptible to the user, eliminating glare and field of view obstruction while enabling eye-tracking functionality.
4Adaptability or versatility
If conventional eye-tracking systems are used, then eye-tracking is achieved, but they require extra processing power
Solution Approach 1:
The patent extracts the eye-tracking measurement function from complex computational processing and implements it through optical means. The MEMS scanning mirror physically directs infrared light to track eye position, and the sensor directly measures reflected light patterns. This extraction of the tracking function into the optical domain reduces the computational burden on the device's processor, thereby reducing power consumption.
Solution Approach 2:
The patent replaces computational image processing with direct optical measurement. Instead of using cameras and complex algorithms to determine eye position, the system uses infrared light reflection and direct sensor measurement. This substitution of mechanical/optical methods for computational methods reduces processing power requirements.
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 configuration reduces the bulk and weight of the device, optimizes the user's viewing experience by minimizing glare, and enhances the overall design efficiency while maintaining effective eye-tracking functionality.
Implementation Method 1
A microelectromechanical system (MEMS) scanning mirror positioned in the IR light path may be configured to direct the IR light along the IR light path
Implementation Method 2
A relay positioned in the IR light path downstream of the MEMS scanning mirror may include at least one mirror configured to reflect the IR light directed by the MEMS scanning mirror along the IR light path
Implementation Method 3
At least one sensor configured to receive the IR light after being reflected by the eye
Data Source
AI summary
An eye-tracking system is provided. The system includes an at least partially transparent visible light waveguide having a visible light display region configured to emit visible light to impinge upon an eye of a user. A light source is configured to emit at least infrared (IR) light that travels along an IR light path to impinge on the eye. A microelectromechanical system (MEMS) scanning mirror positioned in the IR light path is configured to direct the IR light along the IR light path. A relay positioned in the IR light path downstream of the MEMS scanning mirror includes at least one mirror configured to reflect the IR light along the IR light path. At least one sensor is configured to receive the IR light after being reflected by the eye.