Optical Thread Profile Inspection for Full-Length 3D Measurement
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Solution Overview
Problem
Existing methods for inspecting threaded and cylindrical components face challenges such as wear in contact gages, limited coverage, and alignment issues in non-contact techniques, which affect accuracy and reliability in measuring thread characteristics.
Innovation Solution
A system comprising a fixture, a light source, and an optical detector that moves in unison along the component, allowing for wide-field imaging and incremental profiling, enabling the creation of a composite profile and three-dimensional model, with the ability to handle components that are not perfectly centered or aligned, using a combination of linear and rotational scanning and telecentric optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact-type gages with feelers are used to measure thread characteristics, then mechanical measurement of tolerances is achieved, but the feelers become worn with usage and 100% coverage of the threaded surface is not possible
Solution Approach 1:
The patent replaces the mechanical contact measurement system with an optical measurement system. A light source projects light onto the threaded component, and a video camera captures the reflected light patterns. The thread profile is extracted from the optical image, eliminating physical contact and thus preventing wear of measurement elements while achieving complete surface coverage through optical field illumination.
2Measurement precision
If a light-sensitive detector with small light-sensitive area is used to resolve individual threads, then thread quality can be determined, but the inspection coverage is limited
Solution Approach 1:
The patent transitions from a one-dimensional linear detector to a two-dimensional video camera sensor. The video camera captures the entire threaded surface in a single optical field, providing both high resolution for individual thread detection and complete surface coverage simultaneously. The image processing system then extracts thread profile information from the 2D image data.
3Measurement precision
If laser triangulation is used to build a precise profile of thread form, then quantitative thread characteristics can be derived, but the sensor must be mounted on a precision mechanical system that moves the sensor to scan the thread form
Solution Approach 1:
The patent replaces the mechanical scanning system with a stationary video camera-based optical system. The video camera captures the thread profile in a single shot or through minimal movement, and image processing algorithms extract the thread form characteristics. This eliminates the need for precision mechanical positioning systems while maintaining measurement accuracy through computational methods.
4Area of stationary object
If an optical detector with field of view wider than the component width is used, then the detector can image the outer edges of the component, but the system complexity increases with translation stage and processing requirements
Solution Approach 1:
The patent uses a video camera with a two-dimensional sensor array that provides wide field of view coverage of the entire component in a single capture. The image processing system analyzes the 2D image data to extract thread profiles across the entire component width and length, achieving complete coverage without requiring complex translation stages or sequential scanning mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides accurate and comprehensive inspection of components, including those with complex geometries, allowing for 100% coverage and precise measurement of features like threads and diameters, regardless of alignment, and enables virtual 3-wire analysis and three-dimensional modeling.
Implementation Method 1
A light source projects light onto the component and an optical detector, disposed on another side of the component, detects the light
Data Source
AI summary
A system for inspecting a component includes a fixture for holding the component, a light source disposed on one side of the component, and an optical detector disposed on the other side of the component. The detector images a portion of the outer edges of the component. A translation stage is operative to move the light source and detector in unison along the length of the component. The component is rotated through a predetermined angle about its axis.