Asymmetric Aperture Eyetracker for Focus Accuracy
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Solution Overview
Problem
Existing eyetracking devices face challenges in accurately determining the focus condition and range to an object without restricting user freedom of motion, often requiring additional equipment and complex calibration, and struggle to maintain high-quality image capture in handheld devices due to large and heavy motorized gimbal mechanisms.
Innovation Solution
The use of an asymmetric aperture with an open-center design and multiple illuminators positioned within opaque intrusion tabs, optimizing light gathering and focus condition measurement while minimizing the size and weight of the eyetracker, and employing microelectromechanical systems (MEMS) for camera positioning and focusing to enable miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motorized gimbal mechanisms are used to maintain camera focus on the eye, then focus accuracy is improved, but device size and weight increase
Solution Approach 1:
The patent replaces motorized gimbal mechanisms with a MEMS-based mirror system that uses electrostatic actuation instead of heavy motors and gears. The MEMS mirror tilts in response to eye position changes, maintaining the optical path to the sensor without requiring mechanical gimbals, thereby achieving focus accuracy while dramatically reducing device weight.
Solution Approach 2:
The system changes the operating parameters by using electrostatic fields to control mirror orientation rather than mechanical forces. This allows for rapid, precise adjustment of the optical path with minimal mass, enabling accurate eye tracking in a lightweight handheld device configuration.
2Measurement precision
If additional equipment is added to determine focus condition and range, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the camera lens serve multiple functions: it acts as both the imaging lens for capturing eye images and the objective lens for measuring focus condition and range. By analyzing the focus condition of the captured image, the system simultaneously obtains depth information without requiring separate measurement equipment, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The system merges the imaging function and the range measurement function into a single optical path using the same camera lens. The focus condition analysis of the captured image provides both qualitative focus assessment and quantitative range information, combining multiple measurement capabilities in one integrated system.
3Ease of manufacture
If a symmetric aperture is used, then manufacturing is simplified, but focus condition information becomes indistinguishable
Solution Approach 1:
The patent employs an asymmetric aperture shape (such as rectangular or triangular) instead of a conventional circular symmetric aperture. This asymmetry causes the out-of-focus image of a point light source to have a distinctive orientation that reveals the polarity of the focus error (whether the lens is focused too near or too far), thereby preserving complete focus condition information while remaining manufacturable using standard fabrication techniques.
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 allows for precise focus condition measurement and reduced device size, enabling accurate eyetracking with increased user mobility and integration into small devices like smartphones, while maintaining high image quality and reducing power consumption.
Implementation Method 1
an asymmetric aperture with a noncircular shape of distinguishable orientation and a sensor for capturing the image formed by the lens the aperture
Implementation Method 2
illuminate the eye with infrared light which is reflected from various parts of the eye, particularly the cornea and retina, to an imaging device
Data Source
AI summary
An asymmetric aperture device for a camera is provided that improves light gathering properties by increasing both the light gathering opening of the aperture and the number of light producing light sources placed on the aperture. An asymmetric aperture design is provided that utilizes a significantly larger portion of the camera lens. The tradeoff between the competing objectives of maximizing camera depth of field and maximizing the production of useful focus-condition information within the camera image is optimized. More illumination is provided without significantly increasing the lateral size of the illuminator pattern.