Multi-Direction Slit Light Surface Profiling for Shadow Compensation
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Solution Overview
Problem
Non-contact surface profiling methods using lasers or slit pattern lights face challenges in accuracy due to shadow regions and defects in height measurements when the target object protrudes at angles greater than the irradiation angle, leading to inconsistencies in height data.
Innovation Solution
The method involves projecting slit pattern light in multiple directions to obtain pattern images, calculating vector fields for maximum height variation, and using confidence indexes to integrate these fields, solving the Poisson equation to determine accurate heights by minimizing noise and defects such as shadows and specular reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If laser or slit pattern light is irradiated onto the target object in a single inclined direction, then the measurement process is simple, but shadow regions are generated when the target object protrudes at angles greater than the irradiation angle
Solution Approach 1:
The patent divides the measurement process into multiple segments by irradiating light in multiple different inclined directions (first inclined direction and second inclined direction). This segmentation allows different regions of the target object to be illuminated from different angles, eliminating shadow regions that would occur with single-direction illumination while maintaining the simplicity of the overall measurement process.
2Reliability
If laser or slit pattern light is irradiated onto the substrate in various directions to obtain profile, then shadow regions are reduced, but the heights obtained do not coincide and involve defects
Solution Approach 1:
The patent applies local quality by evaluating the reliability of height measurements obtained from different directions at each specific position (x,y) on the substrate. Confidence indexes are calculated for each direction based on local characteristics such as visibility, specular reflection, and shadow conditions. This allows the system to selectively use reliable measurements from specific directions for each local region while discarding defective measurements, thereby improving overall height measurement precision.
3Adaptability or versatility
If multiple directions of light irradiation are used to obtain height data, then measurement coverage is improved, but data inconsistencies and defects increase
Solution Approach 1:
The patent implements feedback by calculating confidence indexes for each direction's height measurement based on evaluated characteristics (visibility, specular reflection, shadow). These confidence indexes provide feedback on the quality of each measurement, allowing the system to identify and filter out defective data while retaining reliable measurements. This feedback mechanism enables the system to maintain broad measurement coverage while eliminating inconsistent and defective height data through selective integration based on confidence levels.
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 enhances the accuracy of surface profiling by compensating for shadow regions and integrating data from multiple directions, resulting in precise height measurements that minimize defects and improve overall measurement reliability.
Implementation Method 1
projecting slit pattern light toward a target object in at least two directions in sequence to obtain pattern images reflected on the target object
Data Source
AI summary
A method and an apparatus of profiling a surface are disclosed. The method comprises projecting slit pattern light toward a target object in at least two directions in sequence to obtain pattern images reflected on the target object, obtaining heights by using the pattern images according to the directions, obtaining vector fields showing a direction of maximum variation of height, obtaining confidence indexes of the heights corresponding to the at least two directions, obtaining integrated vector fields by using the confidence indexes and the vector fields, and calculating height of each position of the target object by using the integrated vector fields. Therefore, accuracy is enhanced.