Substrate Inspection via World Coordinate Transformation
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Solution Overview
Problem
Existing substrate inspection systems face challenges in achieving accurate defect inspection due to image distortion caused by varying camera positions and attitudes, leading to inconsistent reference image data and reduced detection sensitivity across different systems.
Innovation Solution
A substrate inspection method that uses a camera with an image forming device to transform coordinates from a pixel image coordinate system to a two-dimensional image coordinate system, and then to a three-dimensional camera coordinate system, allowing for the calculation of world-camera coordinate transformation parameters to correct image data and reduce distortion, enabling accurate inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the camera is positioned and adjusted to reduce image distortion, then image quality improves, but installation time and labor increase due to multiple positioning parameters
Solution Approach 1:
The patent transforms the camera coordinate system to a world coordinate system through coordinate transformation, changing the parameter representation from camera-specific parameters to standardized world coordinates. This allows different cameras to use the same reference image data without requiring manual adjustment of multiple positioning parameters, thus reducing installation time while maintaining image quality.
2Measurement precision
If different cameras are adjusted by different operators with slightly different parameters, then individual camera optimization is achieved, but consistency across multiple systems deteriorates
Solution Approach 1:
The patent creates a universal coordinate system (world coordinate system) that can be used across multiple substrate inspection systems. By transforming camera-specific coordinate systems to this universal system, the same reference image data can be applied to all systems, ensuring consistency while allowing each camera to maintain its individual optimization through the transformation process.
3Measurement precision
If reference image data is prepared for each substrate inspection system, then inspection accuracy improves, but work preparation time increases
Solution Approach 1:
The patent creates a standardized world coordinate system that serves as a common reference framework for all substrate inspection systems. Instead of preparing separate reference image data for each system, the same reference data can be copied and used across all systems after coordinate transformation, significantly reducing preparation time while maintaining inspection accuracy through the standardized coordinate framework.
4Loss of time
If common reference image data is used across different substrate inspection systems, then preparation work is reduced, but detection sensitivity decreases due to positioning errors
Solution Approach 1:
The patent replaces the mechanical adjustment system (manual positioning of cameras) with a mathematical coordinate transformation system. By substituting physical alignment with computational transformation, the system can use common reference image data across different systems without losing detection sensitivity, as the coordinate transformation compensates for positioning differences.
Data Source
AI summary
A substrate inspection method capable of accurately inspecting a substrate is provided. A jig having reference points represented by known coordinates in a three-dimensional world coordinate system is photographed by a camera and coordinates of the reference points in a pixel image coordinate system defined by pixels of an image forming device is determined. The coordinates in the pixel image coordinate system are transformed into those in a camera coordinate system set on the camera, and world-camera coordinate system transformation parameters are calculated. Image data in the pixel image coordinate system obtained by photographing a substrate to be inspected is transformed into image data in a world coordinate system for inspection. The accurate inspection of the substrate to be inspected can be achieved because distortion in the image of the substrate to be inspected in the world coordinate system attributable to the position and attitude of the camera is reduced.