Optical Lens Trimming Guideline via Reference Image Comparison
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Solution Overview
Problem
Current methods for trimming optical lenses to fit spectacle frames lack precision, especially for rimmed frames, due to limitations in acquiring necessary data from face-on images, such as constraints related to frame thickness and nose pad positions, and the expense of using telecentric objectives.
Innovation Solution
A method involving the removal and imaging of a reference optical lens, both with and within the spectacle frame, using a non-telecentric objective to acquire face-on and side-on images, allowing for the deduction of trimming parameters through image processing, which can include scaling and curvature measurements to achieve precise lens shaping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a face-on image of a blank is used to determine the shape of the optical lens, then the acquisition process is simplified, but the precision is insufficient due to scale variations caused by the curved surface and non-telecentric imaging
Solution Approach 1:
The patent introduces a reference blank as an intermediary object. By imaging the reference blank both inside and outside the spectacle frame, the system creates a reference measurement that mediates between the simple face-on imaging process and the need for precise shape determination. This reference allows correction of scale variations without requiring expensive telecentric objectives.
Solution Approach 2:
The patent creates an optical copy of the reference blank in two states: mounted inside the spectacle frame and removed from it. By comparing these two copies, the system can determine the true shape of the blank and correct for distortions. This copying approach enables precise measurement through image processing rather than direct telecentric imaging.
2Measurement precision
If a telecentric objective is used to acquire images of the blank, then measurement precision is improved, but the cost of the equipment increases significantly
Solution Approach 1:
The patent replaces the expensive telecentric objective with a standard, inexpensive camera system. The reference blank serves as a disposable or reusable reference object that enables precise measurements through software processing rather than expensive hardware. This substitution achieves similar precision at much lower equipment cost.
Solution Approach 2:
The patent substitutes the mechanical/optical solution (telecentric objective) with an image processing solution. By capturing images with a standard camera and using computational methods to correct scale variations, the system replaces the need for specialized expensive optical hardware with more affordable digital processing techniques.
3Ease of manufacture
If only a face-on image is acquired, then the imaging process is simpler, but constraints related to frame thickness and nose pad positions cannot be determined
Solution Approach 1:
The patent transitions from two-dimensional face-on imaging to three-dimensional shape determination by comparing images of the reference blank in different states (inside and outside the frame). This dimensional approach allows extraction of depth-related information such as frame thickness and nose pad positioning that cannot be obtained from a single face-on view.
Data Source
AI summary
Disclosed is a method of determining a guideline for trimming an optical lens to be trimmed in view of its mounting in a spectacle frame in which is mounted at least one reference optical lens, including: removing the reference optical lens; fixing the removed reference optical lens on a support of a machine for acquiring images; acquiring, with an image sensor, at least one first image of the removed reference optical lens; processing each acquired first image in order to deduce therefrom trimming parameters for the optical lens to be trimmed; and defining the trimming guideline as a function of the trimming parameters. Before or after the first acquiring step, a second step of acquiring a second image of the reference optical lens mounted in the spectacle frame, and in the processing step, the trimming parameters are defined as a function also of the second image is included.