Pupil Center Positioning via Ellipse Fitting in VR
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Solution Overview
Problem
Current pupil center positioning methods in VR/AR devices, such as the projection coordinate method, suffer from low calculation accuracy and poor anti-interference ability due to factors like eyelashes and eyelids, affecting user experience.
Innovation Solution
A pupil center positioning apparatus and method utilizing a hardware implementation based on an ellipse fitting algorithm, employing the Cramer's Rule to obtain parameters of an elliptic equation from N boundary point coordinates, which increases calculation accuracy and anti-interference ability, and is integrated into virtual reality devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the projection coordinate method is used for pupil center positioning, then the device complexity is reduced, but the measurement precision deteriorates due to low calculation accuracy and poor anti-interference ability
Solution Approach 1:
The patent changes the mathematical parameters and calculation model from simple projection coordinates to ellipse fitting parameters (five-parameter ellipse equation). By fitting an ellipse to the pupil boundary points and calculating the center from ellipse parameters, the system achieves higher measurement precision while maintaining acceptable device complexity through standardized mathematical operations
Solution Approach 2:
The patent applies the ellipse fitting algorithm which models the pupil boundary as an elliptical curve rather than using straight-line projection coordinates. This curvature-based approach better matches the actual circular/elliptical shape of the pupil, significantly improving measurement precision and anti-interference ability against eyelash and eyelid disturbances
2Measurement precision
If the ellipse fitting algorithm with Cramer's Rule is implemented in hardware, then the measurement precision improves, but the device complexity increases due to matrix operation circuits and parameter operation circuits
Solution Approach 1:
The patent divides the pupil center positioning system into three distinct functional modules: matrix operation circuit (for forming and solving linear equations), parameter operation circuit (for calculating ellipse parameters using Cramer's Rule), and coordinate operation circuit (for deriving pupil center coordinates). This segmentation allows each module to perform specialized operations efficiently, improving overall calculation accuracy while making the complex hardware architecture more manageable and modular
Solution Approach 2:
The patent replaces traditional software-based image processing algorithms with dedicated hardware circuits that perform matrix operations and ellipse parameter calculations. This hardware implementation substitutes general-purpose computational mechanisms with specialized electronic circuits, achieving higher calculation accuracy and processing speed while the modular circuit design keeps the increase in device complexity controlled
3Measurement precision
If N boundary point coordinates are processed with ellipse fitting, then the measurement precision improves, but the loss of time increases due to additional matrix operations and parameter calculations
Solution Approach 1:
The patent performs preliminary actions by first fitting an ellipse to the N boundary points of the pupil area and obtaining the ellipse parameters (a, b, c, d, e) before calculating the pupil center coordinates. This preliminary ellipse fitting step, while requiring additional matrix operations, organizes the boundary point data into a standardized mathematical model that simplifies subsequent center coordinate calculations and improves overall processing efficiency
Solution Approach 2:
The patent transforms the raw boundary point coordinate data into ellipse parameters through fitting, and then transforms these parameters into pupil center coordinates. This parameter transformation approach converts complex geometric boundary data into simplified algebraic parameters, improving measurement precision while the efficient algebraic operations reduce the time penalty compared to direct geometric methods
Data Source
AI summary
The embodiments of the disclosure provide a pupil center positioning apparatus and method, and a virtual reality device. The pupil center positioning apparatus may comprise: a matrix operation circuit configured to obtain a set of linear normal equations according to received N boundary point coordinates of a pupil area, N being a positive integer greater than 5; a parameter operation circuit configured to obtain parameters of an elliptic equation employing the Cramer's Rule according to the set of linear normal equations; and a coordinate operation circuit configured to obtain the center coordinate of the pupil area according to the parameters of the elliptic equation.