Eyeglass Frame Cant Angle Measurement Without Measuring Brackets
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Solution Overview
Problem
Existing methods for determining the pretilt angle in spectacle frames require measuring brackets, which can cause discomfort and unnatural head positioning, leading to inaccurate measurements, especially when precise lateral images are not available.
Innovation Solution
A computer-implemented method that captures lateral images of a person wearing a spectacle frame, annotates a vertical lens edge, and corrects for perspective distortions using assumed annotation lines and geometric considerations to determine the pretilt angle accurately without the need for measuring brackets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measuring brackets are used to determine pretilt angle, then measurement precision can be improved, but ease of operation deteriorates due to discomfort and unnatural head positioning
Solution Approach 1:
The invention extracts and removes the measuring brackets from the measurement system. Instead of using physical measuring brackets attached to the spectacle frame, the method uses image processing of the frame's lens edges directly visible in lateral images, thereby eliminating the source of discomfort and unnatural head positioning while maintaining measurement capability
Solution Approach 2:
The invention creates a digital representation (annotation) of the vertical lens edge from the lateral image. By copying the geometric information of the lens edge into an annotated line in the image space, the system obtains measurement data without physical contact, avoiding the need for measuring brackets that cause discomfort
2Measurement precision
If precise lateral images are required for accurate pretilt angle determination, then measurement precision improves, but device complexity increases due to precise positioning requirements
Solution Approach 1:
The invention changes the approach from requiring precise physical positioning parameters to using image processing parameters. By annotating the lens edge in the lateral image and using geometric relationships within the image space, the system determines pretilt angle without needing precise control of head positioning parameters
Solution Approach 2:
The invention replaces the mechanical positioning system with an optical-digital system. Instead of using mechanical means to achieve precise lateral views and positioning, the method uses camera imaging combined with image processing algorithms to extract measurement information, thereby reducing mechanical complexity
3Manufacturing precision
If measuring brackets are used to correct perspective distortion, then manufacturing precision improves, but object-generated harmful factors increase due to user discomfort
Solution Approach 1:
The invention introduces an intermediary - the annotated lens edge line in the lateral image - that mediates between the perspective-distorted image and the accurate pretilt angle measurement. By using geometric relationships of the annotated line rather than physical measuring brackets, the system achieves accurate lens centering without generating user discomfort
Solution Approach 2:
The invention creates a digital copy (annotation) of the lens edge geometry from the lateral image. This copied geometric information is then used to determine the pretilt angle, replacing the need for physical measuring brackets that cause harmful effects, while maintaining the ability to correct for perspective distortion through image-based geometric analysis
Data Source
Figure 1A~1B
Figure 2~3
Figure 4A~5
AI summary
Methods and devices for determining the cant angle of an eyeglass frame are provided. This involves taking at least one lateral photograph of a person wearing the frame. In some variations, the rim of the lens is annotated in the lateral image. The cant angle can then be determined based on the annotated rim and a predefined annotation line, or based on an annotated temporal and nasal rim.