Structured-Light Topographic Measurement Without Reflection Artefacts
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Solution Overview
Problem
Existing methods for measuring the dimensions and shape of salient parts on a surface, such as electrically conducting pads, suffer from poor image quality due to artefacts like spurious reflections and shadows, leading to inaccurate calculations.
Innovation Solution
A method involving the acquisition of multiple images of a sample surface illuminated by structured lights with varying angles, frequencies, and colors to identify and reduce artefacts, forming working images devoid of these artefacts for precise calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single structured light illumination is used to acquire images for topographic measurement, then the measurement process is simple and quick, but image quality deteriorates due to artefacts such as spurious reflections and shadows
Solution Approach 1:
The measurement process is segmented into multiple image acquisition series, each capturing images under different illumination conditions (different angles, exposure times, or colors). By dividing the measurement into these segments, the system can identify and eliminate artefacts that appear only under specific conditions, thereby improving image quality without requiring a complete redesign of the measurement system.
Solution Approach 2:
The system employs periodic action by acquiring multiple series of images with structured light applied at different parameters (angles, exposure times, colors) in a systematic sequence. This periodic variation in illumination conditions allows the detection and elimination of artefacts while maintaining an organized and manageable measurement process.
2Measurement precision
If multiple images are acquired with varying illumination parameters to reduce artefacts, then image quality improves, but the measurement time increases
Solution Approach 1:
The system performs preliminary action by acquiring multiple series of images with different illumination parameters before final processing. By pre-acquiring images under various conditions and identifying artefacts in advance, the system can efficiently select or combine the best images for final measurement, reducing the need for repeated measurements and overall measurement time.
Solution Approach 2:
The system changes illumination parameters (angle, exposure time, color) systematically across different image series. By varying these parameters and analyzing which conditions produce artefact-free images, the system can optimize the measurement process to achieve high image quality while minimizing the total number of images that need to be processed.
3Manufacturing precision
If artefacts are present in the acquired images, then the measurement process remains simple, but the calculation accuracy of salient part dimensions deteriorates
Solution Approach 1:
The system applies the extraction principle by identifying and removing artefacts from the image series. By detecting artefacts that appear in specific image series (such as spurious reflections in certain angles or shadows in specific lighting conditions) and excluding these problematic images from final processing, the system ensures that only high-quality, artefact-free images are used for dimensional calculations.
Solution Approach 2:
The system implements feedback by analyzing the acquired image series to identify artefacts and using this information to guide the selection or combination of images for final measurement. The feedback loop allows the system to automatically adjust which images are used for calculation, ensuring dimensional accuracy while managing processing complexity through intelligent image selection.
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
Enhances the precision of topographic measurements by minimizing artefacts, allowing for accurate determination of salient part dimensions and shapes.
Implementation Method 1
A textured light is applied on the surface of a sample that has multiple salient parts. The textured light defines a plurality of repetitive patterns that are applied on the surface of the sample.
Implementation Method 2
Several images of the surface of the sample illuminated by the textured light are acquired. By analysing the different images, the dimensions and shape of the salient parts can be calculated.
Data Source
AI summary
A topographic measurement method includes provision of a sample including first surface provided with plurality of salient patterns. The first surface of the sample is illuminated by means of structured light that defines several repetitive patterns. The structured light is emitted at first angle with respect to first surface. A first image of first surface of sample illuminated by structured light is acquired. The first image is acquired at second angle with respect to first surface. A second image of illuminated sample is acquired. The second image differs from first image by value of exposure time. The first image is compared with second image to determine presence of at least one artefact on the first image. A reference image is formed from the first image and the second image. The reference image is devoid of any artefact. A quantity representative of the first surface is calculated from the reference image.