Uncalibrated Camera Feature Measurement Using Projected Scale Template
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Solution Overview
Problem
Current methods for inspecting the location and size of features in assembled structures, such as holes, are costly, require skilled labor, and can disrupt manufacturing operations, as they often rely on hard tooling or coordinate measurement machines (CMMs) that are expensive and limited in accessibility.
Innovation Solution
A vision system using a laser projector and uncalibrated camera to project a scale template and measurement pattern onto the article, allowing for non-invasive, automated measurement of feature size and location by determining the image scale factor and rectifying geometric distortion in the image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hard tooling is used for inspection, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces mechanical hard tooling with an optical vision system consisting of a camera and laser projector. The system projects a scale template and measurement pattern onto the article, captures images with a camera, and uses image processing to determine feature locations and sizes. This substitution eliminates the need for complex mechanical tooling while achieving comparable measurement precision through optical and computational methods.
2Measurement precision
If coordinate measurement machine (CMM) is used, then measurement precision is improved, but productivity decreases due to production halt
Solution Approach 1:
The vision system enables continuous measurement during manufacturing operations without requiring production to halt. The system can capture images and perform measurements while the article is being assembled or positioned, allowing overlapping of measurement activities with manufacturing processes. This eliminates the productivity loss associated with stopping production for CMM inspections.
3Measurement precision
If CMM with moveable arm is used, then measurement precision is improved, but ease of operation worsens due to limited access
Solution Approach 1:
The patent transitions from a mechanical arm-based measurement approach to an optical projection and imaging approach. By projecting the measurement pattern and scale template onto the article surface and capturing images from various angles, the system achieves measurement capability in areas that would be difficult or impossible to access with a physical moveable arm, thereby improving ease of operation for complex geometries.
4Device complexity
If uncalibrated camera is used, then device complexity is reduced, but measurement precision deteriorates due to geometric distortion
Solution Approach 1:
The patent introduces a scale template as an intermediary reference object projected onto the article. This template provides known geometric relationships and dimensions that serve as a reference for correcting geometric distortion in the captured images. By comparing the projected scale template's known dimensions with its appearance in the image, the system can calculate and compensate for lens distortion and perspective effects, maintaining measurement precision without requiring complex camera calibration.
Data Source
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AI summary
A method of measuring a feature of an article may include projecting a scale template onto the article at a predetermined size. The method may additionally include projecting a measurement pattern onto the article. An image containing the feature, the scale template, and the measurement pattern may be recorded by the camera. The method may further include determining a scale factor of the image based on the scale template, and determining a size and/or a location of the feature based upon the measurement pattern and the image scale factor.