Curved-Surface Deviation Measurement With Chromatic Confocal Scanning

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Solution Overview

Problem

Existing methods for measuring geometric deviations in the curvature of curved surfaces, particularly in thin glass sheets for vehicle glazing, are inefficient, require specialized templates, prone to mechanical stress, and unsuitable for high-speed production lines, leading to delays, costs, and potential surface degradation.

Innovation Solution

An automated, non-contact method using a chromatic confocal sensor and an articulated automated arm with six degrees of freedom to measure curvature deviations by tracing a defined trajectory, eliminating the need for templates and enabling high-speed, flexible quality control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If contact-based measurement methods (feelers, potentiometers) are used to measure curvature deviations, then measurement capability is provided, but mechanical stress and surface degradation occur

Engineering Contradiction:
Improvecurvature deviation measurementVSAvoidmechanical stress on thin glass
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces mechanical contact-based measurement systems (feelers, potentiometers) with an optical measurement system using a camera and image processing. This substitution eliminates mechanical contact with the glass surface, thereby removing the source of mechanical stress and surface degradation while maintaining measurement capability through optical means

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If specialized templates are used for each glass sheet shape, then measurement accuracy is improved, but device complexity and production time increase

Engineering Contradiction:
Improvecurvature measurement accuracyVSAvoidtemplate development and maintenance
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses a digital image of the reference curved surface captured by a camera instead of physical templates. This digital copy can be stored and reused for multiple measurements without physical wear or degradation, eliminating the need to develop and maintain specialized physical templates for each glass sheet shape while maintaining measurement accuracy through image processing

Inventive Principle:
Principle #26Copying

Solution Approach 2:

The optical measurement system with camera and image processing algorithms serves as a universal measurement device that can measure various glass sheet shapes and curvatures without requiring specialized physical templates for each configuration, thereby reducing device complexity and production time

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Measurement precision

If contact-based measurement devices are used, then curvature measurement is enabled, but production line speed is reduced

Engineering Contradiction:
Improvegeometric deviation measurementVSAvoidmeasurement speed
Core Design Contradiction:
Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces slow mechanical contact-based measurement devices with an optical measurement system using a camera and image processing. This optical system can capture and process images rapidly, enabling measurements to be performed at high speeds compatible with continuous production lines while maintaining geometric deviation measurement precision

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP3894784B1Method for measuring geometric discrepancies between the curved surfaces of a plurality of materials that are to be evaluated and a curved surface of a reference material
Publication Date: 2025.09.17 SAINT GOBAIN SEKURIT FRANCE
  • EP3894784B1 patent drawingFigure 1~2
  • EP3894784B1 patent drawingFigure 3~4
  • EP3894784B1 patent drawingFigure 5

AI summary

The present invention relates to the field of the checking of the reliefs of the curved surfaces of materials, particularly curved surfaces of window glazing designed for means of transport, notably in the automotive industry. The subjects of the invention are a method and system for measuring the geometric discrepancies between the curved surfaces of a plurality of materials that are to be evaluated and a curved surface of a reference material.