Holographic Optical Element for Pupil Tracking
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Solution Overview
Problem
Existing pupil detection and tracking methods struggle to accurately detect and track pupils, especially in individuals with visual defects such as myopia or hyperopia, due to the inability to effectively focus infrared laser light onto the retina.
Innovation Solution
A method utilizing a holographic optical element (HOE) with multiple refractive structures, each designed to correct different visual defects by generating distinct focal points, allowing for reliable pupil detection and tracking by evaluating back-reflected speckle patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single focal point is used for pupil detection, then the detection system is simple, but it cannot accurately detect pupils in individuals with visual defects such as myopia or hyperopia
Solution Approach 1:
The optical system is segmented into multiple refractive structures within the HOE, each generating a distinct focal point. This segmentation allows the system to handle different visual defect types (myopia, hyperopia, emmetropia) by directing light through appropriate refractive structures to create focal points at different distances, thereby achieving accurate pupil detection across diverse visual conditions without requiring entirely separate optical systems.
Solution Approach 2:
The system dynamically adapts to different visual defects by scanning the infrared laser beam across multiple refractive structures of the HOE. The laser beam can be directed to different focal points depending on the detected visual defect type, allowing the system to adjust its optical path in real-time to maintain accurate pupil detection for users with varying visual conditions.
2Reliability
If the infrared laser is focused at a fixed distance, then the optical system is simple, but insufficient backscattering occurs for individuals with visual defects
Solution Approach 1:
The HOE is divided into multiple refractive structures, each designed to focus the infrared laser beam at different distances corresponding to different visual defect conditions. This segmentation ensures that regardless of the user's visual defect type, the laser beam can be focused at the appropriate distance to achieve sufficient backscattering from the retina for reliable speckle pattern evaluation.
Solution Approach 2:
The single HOE component performs multiple functions by incorporating refractive structures for different visual defect types (myopia, hyperopia, emmetropia). This multi-functional design allows the system to achieve sufficient backscattering for all user types without requiring separate optical systems for each visual condition, thereby improving reliability while controlling complexity.
3Measurement precision
If multiple focal points are generated for different visual defects, then pupil detection accuracy improves, but the scanning time increases
Solution Approach 1:
The system performs preliminary action by first determining the user's visual defect type before conducting the full pupil detection scan. By pre-identifying the appropriate focal point based on the visual defect classification, the system can direct the laser beam to the correct focal point from the outset, avoiding unnecessary scanning of other focal points and thereby reducing overall scanning time while maintaining detection accuracy.
Solution Approach 2:
The system dynamically adjusts the laser beam direction to focus on the most probable focal point based on the detected visual defect type. This dynamic adaptation allows the system to concentrate scanning resources on the relevant focal point rather than uniformly scanning all possible focal points, thereby reducing scanning time while maintaining high detection accuracy for users with specific visual defects.
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 enables accurate pupil detection and tracking, even in individuals with visual defects, by ensuring sufficient backscattering of the infrared laser light for speckle pattern evaluation, thereby facilitating reliable visual defect assessment and adaptation.
Implementation Method 1
at least the light of an infrared laser (12) radiated into the eye is scanned via a holographic optical element (HOE 18)... the different refractive structures being designed in such a way that they each generate a different visual defect correction
Implementation Method 2
evaluation of a speckle pattern back-reflected by the eye... sufficient backscattering of the infrared laser light for speckle pattern evaluation
Implementation Method 3
The light/speckle patterns back-reflected in the laser direction, in particular, are measured and used for the evaluation. For example, the back-reflected light/speckle pattern is detected by a photodiode
Data Source
AI summary
A method for a pupil detection and/or pupil tracking with the aid of an evaluation of a speckle pattern back-reflected by an eye of a light of an infrared laser irradiated into the eye. At least the light of the infrared laser irradiated into the eye is scanned via a holographic optical element that includes different refractive structures, the different refractive structures being configured in such a way that they each generate a different visual defect correction.