Structured Illumination Optical Inspection for Transparent Materials
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current substrate defect inspection systems face limitations in resolution due to the diffraction limit of camera lenses, which causes higher frequency features to appear blurry, and existing solutions to increase resolution, such as increasing lens aperture or reducing field-of-view, are either costly or impractical for certain optical setups.
Innovation Solution
The method involves projecting a structured illumination pattern onto a transparent target, capturing images at multiple phase shifts, and extracting high-frequency components to reconstruct a corrected image that exceeds the resolution of the imaging device without altering the lens aperture or field-of-view, using a wavefront modulator and image processing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lens aperture size is increased to improve resolution, then the resolution is improved, but the depth of field decreases and costs increase
Solution Approach 1:
The patent moves the problem from the spatial domain to the frequency domain by capturing multiple images at different defocus distances. By analyzing the frequency content across these defocused images, the system can reconstruct high-frequency information that would be lost in any single in-focus image, effectively resolving the resolution-depth of field tradeoff without changing optical parameters.
Solution Approach 2:
The system changes the focus distance parameter across multiple captures rather than optimizing a single focus setting. By varying the defocus distance and analyzing the resulting frequency domain characteristics, the system can extract high-frequency information while maintaining the original lens aperture and depth of field constraints.
2Measurement precision
If the lens aperture size is increased to improve resolution, then the resolution is improved, but the cost increases
Solution Approach 1:
Instead of using expensive high-aperture optics, the system creates multiple copies of the same optical path by capturing images at different defocus distances. The computational reconstruction process synthesizes the information that would require expensive hardware, achieving super-resolution through software processing of standard optical components.
Solution Approach 2:
The patent changes the focus distance parameter across multiple captures rather than optimizing a single focus setting. By varying the defocus distance and analyzing the resulting frequency domain characteristics, the system can extract high-frequency information while maintaining the original lens aperture and depth of field constraints.
3Measurement precision
If the field-of-view is reduced to improve resolution, then the resolution is improved, but the coverage area decreases
Solution Approach 1:
The patent moves the problem from the spatial domain to the frequency domain by capturing multiple images at different defocus distances. By analyzing the frequency content across these defocused images, the system can reconstruct high-frequency information that would be lost in any single in-focus image, effectively resolving the resolution-field of view tradeoff without changing optical parameters.
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 effectively doubles the resolution of the imaging system, allowing for clear imaging of high-frequency features beyond the diffraction limit, improving defect inspection capabilities without increasing costs or complexity.
Implementation Method 1
the resolution of digital images is still limited by the diffraction limit of the camera lens
Data Source
AI summary
A method of imaging surface features with a large (non-microscopic) field-of-view includes projecting a structured illumination pattern onto the transparent target. The surface features modify the structured illumination pattern, and an image of the modified structured illumination pattern is imaged at each of multiple different introduced phase shifts via an imaging device. The method further provides for extracting, from each of the captured phase-shifted images, image components that correspond to frequencies exceeding a cutoff frequency of the imaging device; and using the extracted image components to construct a corrected image of the surface features of the transparent target. The corrected image has a resolution that is greater than a spatially incoherent point-to-point optical resolution of the imaging device.