Infrared Eye-Tracking in High Ambient Light
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Solution Overview
Problem
Eye-tracking systems face significant challenges in outdoor environments due to high levels of ambient infrared interference from sunlight, which reduces signal-to-noise ratios and increases power consumption, as traditional silicon photodetectors are less sensitive to longer wavelengths like 940 nm.
Innovation Solution
The use of infrared light at 940 nm, paired with narrow linewidth bandpass filters and deep well PIN sensors or quantum film detectors, along with pulsing the optical sources to reduce thermalization time and increase peak power, helps mitigate ambient light interference and improve quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional silicon photodetectors are used for eye-tracking, then the system can operate in indoor environments, but the signal-to-noise ratio deteriorates in outdoor environments due to high ambient infrared interference from sunlight
Solution Approach 1:
The patent changes the operating wavelength parameter from traditional 850 nm to 940 nm infrared, which falls in a spectral region with lower solar irradiance. This parameter change allows the system to operate in outdoor environments by exploiting the atmospheric absorption band where sunlight has reduced intensity, thereby improving signal-to-noise ratio despite using standard silicon photodetectors
Solution Approach 2:
The patent introduces narrow linewidth bandpass filters as intermediary components between the optical source and photodetector. These filters selectively transmit only the 940 nm wavelength while blocking other wavelengths, effectively mediating the interaction between the infrared source and ambient sunlight to reject interfering wavelengths and enhance the desired signal
2Measurement precision
If the optical source power is increased to overcome ambient light interference, then the signal-to-noise ratio improves, but power consumption increases
Solution Approach 1:
The patent changes the wavelength parameter to 940 nm where ambient solar irradiance is naturally lower due to atmospheric absorption. This parameter change improves signal-to-noise ratio without requiring increased optical source power, thereby avoiding increased power consumption while maintaining measurement precision
Solution Approach 2:
The patent converts the naturally occurring atmospheric absorption of sunlight at 940 nm from a potential limitation into a beneficial feature. By operating in this spectral region, the system exploits the Earth's atmosphere as a natural filter that reduces ambient infrared interference, improving signal-to-noise ratio without additional power expenditure
3Object-affected harmful factors
If narrow linewidth bandpass filters are used at 940 nm, then ambient light interference is reduced, but the device complexity increases
Solution Approach 1:
The patent uses standard silicon photodetectors and commercially available 940 nm infrared LEDs or laser diodes, which are existing multi-used components. By combining these universal components with narrow linewidth bandpass filters, the system achieves wavelength-specific operation without requiring specialized or complex custom-designed components, thereby limiting the increase in device complexity
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 the signal-to-noise ratio and reduces power consumption by minimizing ambient light interference and increasing the sensitivity of the eye-tracking system, allowing for more efficient operation in outdoor conditions.
Implementation Method 1
one or more optical sources configured to emit infrared light with a narrow spectral linewidth toward an eye of a user
Implementation Method 2
one or more shuttered optical sensors configured to receive infrared light reflected off the eye of the user
Data Source
AI summary
A method for active eye-tracking comprises pulsing on and off a plurality of infrared optical sources configured to emit infrared light with a narrow spectral linewidth toward an eye of a user, such that a pulse-on duration is less than a duration needed to fully thermalize each optical source. One or more shuttered optical sensors are configured to receive infrared light reflected off the eye of the user. The shuttered optical sensors are opened for a detection duration based on the pulse-on duration, the shuttered optical sensors. A conformation of the user's eye is indicated based on infrared light received at the shuttered optical sensor during the detection duration.