Hybrid 3D Inspection With Interferometry and Triangulation
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Solution Overview
Problem
Existing optical inspection methods for workpieces, such as printed circuit boards and display panels, face limitations in resolution and ambiguity in measuring 3D topography, with triangulation methods lacking precision and interferometric methods having cyclic ambiguity issues.
Innovation Solution
An optical inspection apparatus combining an interferometer module and a triangulation module, utilizing beam combiner optics to ensure accurate mutual registration of fields-of-view, allowing for high-resolution and unambiguous 3D mapping by integrating interferometric and triangulation measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If triangulation methods are used to measure topography, then measurement range is improved, but measurement precision deteriorates
Solution Approach 1:
The patent combines triangulation module and interferometer module into a hybrid inspection system. The triangulation module provides large measurement range while the interferometer module provides high vertical resolution. The beam combiner optics merge both measurement beams to inspect the same area, and the processor integrates both measurement results to achieve both large range and high precision simultaneously.
2Measurement precision
If interferometric methods are used to measure topography, then measurement precision is improved, but measurement range deteriorates due to ambiguity
Solution Approach 1:
The processor uses the triangulation measurement results as feedback to resolve the ambiguity in interferometric measurements. Since triangulation provides unambiguous height information over large ranges, this information feeds back to determine the correct interference order for each pixel, thereby extending the unambiguous measurement range of the interferometer while maintaining its high precision.
3Device complexity
If separate inspection areas are used for interferometer and triangulation modules, then device complexity is reduced, but measurement accuracy deteriorates due to misalignment
Solution Approach 1:
The beam combiner optics merge the optical paths of the interferometer module and triangulation module so that both modules inspect the same area on the workpiece. This ensures accurate spatial correspondence between the two measurement sets, enabling precise integration of results while maintaining relatively simple device configuration.
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
The combined system provides accurate and unambiguous 3D measurements over a wide range, leveraging the strengths of both methods to achieve precise topographical mapping with enhanced resolution and reduced ambiguity.
Implementation Method 1
produce a first image of interference fringes produced by combining the reflected beam with a reference beam
Implementation Method 2
direct a beam of coherent light toward an area under inspection
Implementation Method 3
capture a second image of the pattern that is reflected from the area under inspection
Data Source
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Figure 2b
AI summary
An optical inspection apparatus includes an interferometer module, which is configured to direct a beam of coherent light toward an area under inspection and to produce a first image of interference fringes of the area. The apparatus also includes a triangulation module configured to project a pattern of structured light onto the area, and at least one image sensor configured to capture the first image of interference fringes and a second image of the pattern that is reflected from the area. Beam combiner optics are configured to direct the beam of coherent light and the projected pattern to impinge on the same location on the area. A processor is configured to process the first and second images in order to generate a 3D map of the area.