Handheld Camera Spectacle Lens Fitting with Inclination Correction
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Solution Overview
Problem
Existing methods for determining fitting parameters for spectacle lenses, such as those using securely installed cameras, often result in errors due to the inclination angle of the camera image plane, which cannot be readily compensated by tilt or swiveling, leading to inaccuracies in calculating centration data and visual point height.
Innovation Solution
A method using a hand-held camera, like a tablet computer with an integrated inclination sensor, acquires images of a subject wearing a spectacle frame with a measurement bracket, correcting the pantoscopic angle and head rotation angle based on the inclination angle to determine the far visual point accurately, accounting for habitual head position and parallax errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a securely installed camera is used to determine fitting parameters, then measurement stability is improved, but the system complexity and installation requirements increase
Solution Approach 1:
The patent replaces the mechanical installation system (securely mounted camera on column) with a handheld mobile camera system. The camera is no longer fixed mechanically but is held by an operator, dramatically simplifying installation while maintaining measurement capability through software-based correction methods.
Solution Approach 2:
The patent changes the operational parameters of the camera system from fixed-position to mobile handheld operation. By measuring and correcting for inclination angle γ and head rotation angle β, the system adapts to varying camera positions and orientations, enabling reliable measurements without secure installation.
2Device complexity
If a hand-held camera is used to determine fitting parameters, then device complexity is reduced, but measurement precision deteriorates due to camera inclination
Solution Approach 1:
The patent implements feedback by measuring the actual camera inclination angle γ using an inclination sensor and the head rotation angle β through image analysis. These measured values are fed back into the calculation process to correct the determined visual point position, compensating for the effects of handheld camera orientation errors.
Solution Approach 2:
The patent introduces correction calculations as an intermediary process between the raw image capture and the final visual point determination. The inclination angle γ and head rotation angle β serve as intermediate parameters that mediate the relationship between the handheld camera's arbitrary orientation and the accurate determination of fitting parameters.
3Device complexity
If camera inclination correction is not applied, then calculation process is simplified, but centration data accuracy deteriorates
Solution Approach 1:
The patent performs preliminary measurement of the camera inclination angle γ and head rotation angle β before the final visual point determination. These preliminary measurements are used to pre-correct the coordinate system and calculation parameters, ensuring that subsequent centration data calculations are based on corrected reference frames.
Solution Approach 2:
The correction calculations for inclination angle γ and head rotation angle β serve as intermediary processing steps that transform the raw handheld camera images into a corrected coordinate system. This intermediary correction layer separates the simplicity of handheld operation from the requirement for precise measurement results.
Data Source
AI summary
The invention is directed to a method allowing the exact determination of the far visual point on spectacle lenses in a spectacle frame for a subject while taking into account the habitual head position or body posture. The method renders it possible to specify the coordinates of the far visual point on spectacle lenses in a coordinate system that is fixed in relation to the spectacle frame coordinate system. The invention also relates to a system carrying out the method.