Scanning Self-Mixing Interferometry Sensor for Eye-Tracking
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Solution Overview
Problem
Increasing the number of self-mixing interferometry (SMI) sensors for improved accuracy in proximity and distance measurements leads to increased complexity, power consumption, and weight, which can occlude the field-of-view in head-mounted devices and complicate electrical routing.
Innovation Solution
A scanning module paired with an SMI sensor operates at high frequencies to generate SMI signals for multiple points, reducing the need for external cameras and simplifying hardware and software architectures by using a micro-electro-mechanical systems scanner to direct coherent light and receive feedback light for accurate velocity and depth measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an array of sensors is used to increase sensor accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the sensing function into temporal segments by using a single SMI sensor that sequentially measures different points through scanning. Instead of having multiple sensors simultaneously, one sensor performs multiple measurements at different spatial locations over time, thereby segmenting the measurement task temporally while maintaining spatial resolution.
Solution Approach 2:
The patent introduces dynamic scanning capability to a static sensing system. By making the single SMI sensor movable through scanning mechanisms, the system dynamically covers multiple measurement points that would otherwise require multiple fixed sensors, thus reducing hardware complexity while maintaining measurement precision.
2Measurement precision
If an array of sensors is used to increase sensor accuracy, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent segments the power consumption across time rather than having continuous power draw from multiple sensors. A single SMI sensor is activated sequentially to measure different points, reducing total power consumption while achieving the same measurement precision that would require multiple simultaneously active sensors.
Solution Approach 2:
The patent employs periodic scanning where a single sensor is activated in periodic intervals to measure different spatial points. This periodic activation pattern reduces average power consumption compared to having multiple sensors continuously active, while still achieving comprehensive measurement coverage.
3Measurement precision
If an array of sensors is used to increase sensor accuracy, then measurement precision is improved, but weight increases
Solution Approach 1:
The patent segments the sensing function across time rather than duplicating sensor hardware. Instead of weighing down the product with multiple physical sensors, a single lightweight SMI sensor performs multiple measurement tasks sequentially through scanning, significantly reducing overall system weight while maintaining measurement precision.
4Measurement precision
If an array of sensors is used to increase sensor accuracy, then measurement precision is improved, but the required size increases
Solution Approach 1:
The patent segments the measurement function temporally rather than requiring simultaneous spatial distribution of multiple sensors. This allows the system to be compact in size since a single small SMI sensor performs all measurements sequentially, avoiding the need for a large array configuration that would increase product volume.
5Measurement precision
If a scanning module is used to direct light to multiple points, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces a scanning module as an intermediary component between the single SMI sensor and the multiple measurement points. This intermediary directs the coherent light from the single sensor to different spatial locations sequentially, enabling the sensor to measure multiple points without requiring multiple sensors, thus improving precision while adding only one intermediary subsystem rather than multiple sensor units.
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 approach enhances sensing accuracy for eye-tracking in head-mounted devices while minimizing hardware and software complexity, reducing power consumption, and maintaining a clear field-of-view.
Implementation Method 1
Self-Mixing Interferometry (SMI) techniques include emitting coherent light from a light source and generating an SMI signal in response to feedback light that is received by the optical cavity of the light source
Implementation Method 2
scanning module that includes a reflective element to redirect coherent light received from an SMI sensor to an eyebox location
Data Source
AI summary
Self-mixed interferometer (SMI) devices and techniques are described for measuring depth and/or velocity of objects. The SMI devices and techniques may be used for eye-tracking. A light source of an SMI sensor emits coherent light that is directed to a target location with a scanning module. One or more SMI signals are measured. The one or more SMI signals are generated by the SMI sensor in response to feedback light received from the target location. The feedback light is a portion of the coherent light that illuminated the target location.