Spectacle Lens Evaluation via Difference Index for Irregular Power
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Solution Overview
Problem
Existing methods for evaluating spectacle lenses fail to distinguish between regular and irregular differences in optical characteristics, which can lead to distortion and discomfort for wearers, and do not adequately consider the cylinder axis in evaluations.
Innovation Solution
A method and device that measure and evaluate the spectacle lens's power distribution, including spherical and cylindrical powers, and cylinder axis, to differentiate between regular and irregular differences by calculating a difference index through differentiation of the difference distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lens is evaluated only at measurement point(s) according to ISO/JIS standards, then the evaluation process is simple and follows standard procedures, but the evaluation does not cover the wide region through which the wearer actually sees, leading to insufficient detection of irregular differences
Solution Approach 1:
The lens surface is divided into multiple measurement points arranged in a grid pattern, allowing the evaluation to cover the entire lens surface rather than just a few standard points. This segmentation enables detection of local irregularities while maintaining a systematic evaluation approach
Solution Approach 2:
The evaluation transitions from point-based measurement to surface-based measurement by introducing a two-dimensional grid of measurement points across the lens surface. This dimensional expansion allows comprehensive coverage of the lens while organizing data in a structured manner
2Measurement precision
If the measured power distribution is directly compared with design data without differentiation, then the evaluation process is simpler, but it cannot distinguish between regular differences and irregular differences that cause distortion
Solution Approach 1:
A difference distribution map is introduced as an intermediary representation between the measured power distribution and design data. This intermediary visualizes the spatial pattern of differences, enabling distinction between regular (systematic) and irregular (local) differences through pattern recognition
Solution Approach 2:
The evaluation methodology is replaced from direct numerical comparison to visual pattern analysis using difference distribution maps. This substitution enables qualitative assessment of difference types (regular vs irregular) that cannot be achieved through simple numerical thresholds
3Measurement precision
If conventional evaluation methods are used, then the evaluation follows established standards, but cylinder axis information is not adequately considered in the assessment
Solution Approach 1:
The evaluation treats different regions of the lens with different importance weights, particularly emphasizing regions where cylinder axis misalignment would have the greatest impact on visual quality. This local quality approach ensures that critical areas are assessed more rigorously
Data Source
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AI summary
The present invention is to provide a lens evaluation method capable of easily evaluating whether there is a difference which greatly changes locally in a lens, and evaluating the degree of the difference. According to the lens evaluation method of the present invention, first, power a distribution of a plurality of measurement point in an arbitrary direction. Next, a calculation power distribution (a design power distribution) is created. Further, a difference distribution between an actually measured power distribution, which indicates an actual power distribution, and a calculation power distribution is obtained. Further, the difference distribution is differentiated to obtain a difference index, and an evaluation is performed based on the difference index to evaluate whether there is a difference which greatly changes locally in a lens, and evaluate the degree of the difference.