Spectacle Lens Fitting Height Estimation Without Pantoscopic Correction
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Solution Overview
Problem
Existing methods for determining the fitting height of spectacles lenses, particularly for rimless or partly rimless frames, are inaccurate due to difficulties in detecting the boxing system and neglect non-paraxial effects, leading to errors in pantoscopic angle correction.
Innovation Solution
The method decomposes the fitting height into a structural term, measured at the factory, and a postural term, measured on the wearer, using an upper referential point above the mounting point, which are combined to estimate the fitting height, allowing for precise measurements even with rimless frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods are used to determine fitting height with pantoscopic angle correction, then measurement can be performed, but measurement precision deteriorates due to non-paraxial effects and boxing system detection difficulties
Solution Approach 1:
The patent extracts and eliminates the problematic pantoscopic angle correction step from the measurement process. By using a front view camera approach that directly measures fitting height without requiring pantoscopic angle measurement or correction calculations, the method removes the source of non-paraxial errors and boxing system detection difficulties that plague traditional side-view methods.
Solution Approach 2:
The patent introduces an intermediary reference system based on the frame's upper and lower edges rather than relying on the boxing system or pupil center. This intermediary approach uses easily detectable frame features as reference points, avoiding the complex and error-prone detection of the boxing system while still enabling accurate fitting height measurement.
2Measurement precision
If pantoscopic angle correction is applied to account for lens plane inclination, then measurement accuracy should improve, but errors increase due to non-paraxial effects in the correction calculation
Solution Approach 1:
The patent completely removes the pantoscopic angle correction step from the measurement process. By capturing the frame in a front view and measuring fitting height directly between the upper and lower edges, the method eliminates the need for any angular correction calculations, thereby avoiding non-paraxial errors entirely.
Solution Approach 2:
Instead of measuring from the side and mathematically correcting for lens plane inclination, the patent inverts the approach by measuring directly from the front view. This inversion allows direct observation and measurement of the fitting height without requiring any correction for lens orientation, making the measurement more reliable.
3Productivity
If automated measurement systems are implemented, then productivity increases, but device complexity increases due to multiple cameras and sensors required
Solution Approach 1:
The patent makes a single front view camera perform multiple functions: detecting the frame, identifying upper and lower edges, locating the mounting point, and measuring fitting height. This universal approach eliminates the need for multiple specialized cameras and sensors, reducing device complexity while maintaining automated measurement capability.
Solution Approach 2:
The patent segments the measurement process into distinct image processing steps (frame detection, edge identification, mounting point location, fitting height calculation) that can be performed sequentially by software, reducing the need for complex hardware while maintaining automation.
Data Source
AI summary
A process and apparatus for determination of an estimation of a fitting height of a lens in a frame of spectacles. An upper referential point of the frame situated at a level above the mounting point is specified, the referential point allowing to define an upper referential horizontal plane passing on the upper referential point and a structural term defined as an algebraic distance between a bottom referential line and the upper referential horizontal plane is measured, and a postural term defined as an algebraic distance between the upper referential horizontal plane and a gazing axis, is measured, the fitting height being estimated by summing the value of the postural term and the value of the structural term.