Near Visual Point Determination Without Reference Brackets
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Solution Overview
Problem
Existing methods for determining near visual points for spectacle lenses often require the use of reference objects, which can influence the position of the spectacle frame on the face and lead to inaccuracies, and may not accurately represent the natural reading position of the wearer.
Innovation Solution
A method and device that capture images of a person's head while looking at a movable near-sight target, determining the orientation and position of the target, and calculating the near visual point based on the pupil or cornea position relative to the axis of symmetry of the imaging device, without the need for side target markers or measuring sticks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference objects (measuring brackets) are used to determine near visual points, then the arrangement of the spectacle frame in space can be recognized, but the position of the spectacle frame on the face is influenced and measurement inaccuracies arise
Solution Approach 1:
The patent removes the measuring bracket from the measurement system entirely. Instead of using a physical reference object attached to the spectacle frame, the invention uses the camera device itself as the reference, with its known position and orientation relative to the image sensor. This extraction eliminates the interference caused by measuring brackets while maintaining measurement capability through mathematical calculation of the near visual point based on pupil position and camera parameters.
2Measurement precision
If a measuring bracket is attached to the spectacle frame or face, then spatial arrangement can be determined, but the spectacle wearer's natural reading position is influenced
Solution Approach 1:
The camera device serves itself as the reference object for measurement. The known position and orientation of the camera relative to the image sensor provide the spatial reference needed, eliminating the need for external measuring brackets. This self-service approach allows the wearer to assume their natural reading position without being constrained or influenced by additional measurement equipment.
3Measurement precision
If side target markers are used to determine near visual point, then the position can be calculated, but the eyes may be obscured by temple pieces
Solution Approach 1:
The patent uses the camera device as an intermediary to determine eye position indirectly. Instead of requiring direct visual markers on the eyes that might be obscured by temple pieces, the system captures images of the eyes (or their reflections) and calculates the near visual point through image processing and geometric calculations based on the known camera parameters. This intermediary approach bypasses the visibility problem caused by temple piece obstruction.
Data Source
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AI summary
Methods and devices for determining a near viewing point are provided. A person being examined looks at a moving near viewing target (60), and an image of the person is captured with a camera device (62). The orientation and/or position of the near viewing target (60) is also determined. From this, the near viewing point is then determined.