Pupil Position Tracking with Beam Steering Against Smart Glasses Slippage
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Solution Overview
Problem
Existing optical systems for determining eye position, pupil position, and gaze vector in smart glasses are prone to disruptions due to unintentional slippage of the glasses, necessitating improved methods to compensate for such movements.
Innovation Solution
An optical device using a laser, first and second photodetectors, an adjustable beam deflection device, and a control unit to scan the eye and its environment, measuring laser power changes and scattered light to determine pupil position, employing laser feedback interferometry and oblique placement of the second photodetector to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical systems are used to determine eye position and pupil position in smart glasses, then eye tracking functionality is achieved, but the system is disrupted by unintentional slippage of the glasses
Solution Approach 1:
The patent introduces a beam deflection device as an intermediary component that mediates between the fixed optical system and the moving eye. This device compensates for relative movements by actively adjusting the beam path, allowing the system to maintain accurate pupil position determination despite slippage of the smart glasses. The beam deflection device acts as a mediator that decouples the measurement system from the mechanical instability.
Solution Approach 2:
The system employs feedback mechanisms where the detected pupil position and eye movements are continuously fed back to adjust the beam deflection device. This closed-loop control compensates for slippage in real-time, maintaining reliable eye tracking. The feedback loop processes the optical signals and dynamically adjusts the system to counteract disturbances caused by unintentional movement.
2Measurement precision
If a beam deflection device is introduced to compensate for head movement, then measurement stability is improved, but device complexity increases
Solution Approach 1:
The beam deflection device serves multiple functions simultaneously: it directs the illumination beam to the eye, compensates for head movements, and enables scanning of the pupil. By making this single component multi-functional, the patent avoids adding separate complex subsystems for each function, thereby improving measurement precision without proportionally increasing overall device complexity.
Solution Approach 2:
The patent combines the illumination path and the detection path through the same beam deflection device. This merging of functions allows the system to use a single adjustable component for both delivering light to the pupil and collecting reflected light for detection, simplifying the overall optical architecture while maintaining high measurement precision.
3Measurement precision
If laser feedback interferometry is used to detect pupil position, then measurement sensitivity is improved, but susceptibility to interfering light increases
Solution Approach 1:
The system applies local quality by using wavelength-specific detection. The laser operates at a specific wavelength, and the detection system is optimized to detect only light at this wavelength. This selective detection enhances measurement sensitivity while filtering out interfering light at different wavelengths, as the detection is localized to the specific spectral region of the laser light.
Solution Approach 2:
The patent converts the potential harm of interfering light into a benefit by using the interference effect constructively. Laser feedback interferometry deliberately uses the interference between the laser light and light reflected from the pupil to create sensitive measurement signals. By controlling and measuring the interference pattern, the system transforms what could be noise into a precise measurement mechanism.
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
Provides a robust and stable determination of pupil position and gaze vector, resistant to interfering light and relative movements, enabling accurate eye tracking in smart glasses without continuous high computational effort.
Implementation Method 1
The device comprises a laser, a first photodetector, a second photodetector, an adjustable beam deflection device and a control unit
Implementation Method 2
If illumination light is reflected at a boundary surface of the eye, for example the retina of the eye, with substantially perpendicular incidence of light and then travels in the opposite direction to the direction of illumination... this reflected light interferes with the light generated in the laser
Implementation Method 3
during the illumination of at least a second portion of the illumination points... scattered illumination light can be detected on the eye (illumination point on the eye) or on the eye environment (illumination point on the eye environment) by means of the second photodetector
Data Source
AI summary
An optical device for determining a pupil position of an eye. The optical device includes a laser, first and second photodetectors, a beam deflection device, and a control unit. The optical device guides light generated by the laser at least partially as illumination light via an illumination beam path to the beam deflection device and illuminates illumination points on the eye/eye environment using the illumination light, during the illumination of a first portion of the illumination points, measures using the first photodetector a laser power of the laser when illuminating the illumination points and/or detects using the first photodetector illumination light reflected at a boundary surface of the eye/eye environment and entering the illumination beam path via the beam deflection device, and, during the illumination of a second portion of the illumination points, detects illumination light scattered on the eye/eye environment using the second photodetector.