Single Point Calibration for Eye Tracking in Head Mounted Displays
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Solution Overview
Problem
Conventional eye tracking systems for head-mounted displays, particularly in virtual reality applications, require extensive calibration processes that burden users with frequent target alignments, reducing user experience and increasing operational complexity.
Innovation Solution
An eye tracking system that determines the pupillary axis and angular offset between the pupillary axis and the true line of sight for each eye using a single point calibration process, where the user only needs to look at one specific target, generating an eye model with information about the corneal sphere radius and origin, and storing calibration data for future use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration processes are used with multiple targets, then measurement precision of eye tracking is improved, but device complexity and ease of operation deteriorate due to frequent calibration requirements
Solution Approach 1:
The system performs a comprehensive calibration process that captures multiple images of the pupil at different known positions in advance, storing these images for future use. This preliminary action eliminates the need for repeated calibration sessions, reducing user burden while maintaining tracking accuracy through the use of pre-captured calibration data
Solution Approach 2:
The system creates a digital model (eye model) that copies and stores the physical characteristics of the user's eye including pupil shape, corneal reflections, and anatomical features. This digital copy is then used for ongoing tracking without requiring physical recalibration, maintaining precision while improving ease of operation
2Measurement precision
If comprehensive eye modeling is performed, then measurement precision and reliability are improved, but device complexity increases
Solution Approach 1:
The calibration process is divided into distinct segments: capturing images at multiple known positions, identifying pupil shape and corneal reflections in each image, fitting geometric models to the data, and storing the resulting eye model. This segmentation allows the complex task to be managed systematically while maintaining high precision through each focused sub-process
3Productivity
If single point calibration is used, then ease of operation and productivity are improved, but measurement precision may deteriorate
Solution Approach 1:
The system performs a thorough calibration capturing multiple images at different known positions during an initial setup phase. This preliminary comprehensive calibration stores rich data about the user's eye geometry and optical properties, enabling accurate tracking throughout subsequent use without requiring repeated calibration sessions
Solution Approach 2:
The system uses the initially captured eye model to automatically perform its own calibration for all subsequent tracking operations. Once the comprehensive eye model is created, the system serves itself by using this model to interpret pupil images and determine gaze direction accurately without requiring user intervention for recalibration
Data Source
AI summary
A head mounted display (HMD) comprises an eye tracking system configured to perform a calibration process using an eye tracking system of the HMD that includes determining a pupillary axis and/or determining an angular offset between the pupillary axis and the eye's true line of sight. The eye tracking system obtains an eye model captures images of the user's pupil while the user is looking at a target or other content displayed on the HMD. In some embodiments, the calibration process is based on a single image of the user's eye and is performed only once. For example, the process can be performed the first time the user uses the HMD, which stores the calibration data for the user in a memory for future use.