Adaptive Focus Camera Array for Warped Substrate Inspection
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Solution Overview
Problem
Automated optical inspection systems for printed circuit boards face challenges in achieving fast and accurate inspection across a wide variety of components and substrates, with issues such as component placement inaccuracies, electrical connection problems, and warpage leading to defects and increased costs.
Innovation Solution
An optical inspection system with a camera array and adaptive focusing capabilities, utilizing multiple illumination types and a range calculator to ensure high-speed imaging and precise focus, even on warped substrates, without the need for sophisticated motion control hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional optical inspection systems are used, then inspection can be performed, but inspection speed is too slow for high-speed manufacturing requirements
Solution Approach 1:
The inspection system divides the substrate inspection into multiple zones using an array of cameras, with each camera inspecting a specific region simultaneously. This parallel inspection approach enables the system to process the entire substrate at high speed without sacrificing inspection thoroughness, directly resolving the contradiction between inspection speed and manufacturing time requirements.
2Measurement precision
If conventional fixed-focus cameras are used, then system complexity is reduced, but inspection accuracy on warped substrates deteriorates
Solution Approach 1:
The system employs focus actuators that dynamically adjust the focus of each camera in real-time based on the local topography of the substrate. This dynamic focusing capability allows the system to maintain high inspection accuracy on warped substrates without requiring overly complex mechanical positioning systems, as the focus adjustment is performed independently at each camera location.
Solution Approach 2:
The system uses the inspection images themselves to automatically determine the required focus adjustments for each camera. The image processing system analyzes the captured images, identifies focus quality metrics, and feeds this information back to the focus actuators, creating a self-regulating system that maintains optimal focus without external intervention or complex control hardware.
3Reliability
If multiple illumination types are used, then inspection quality improves, but system complexity and cost increase
Solution Approach 1:
The illumination system is designed with multi-functional illumination sources that can operate in multiple modes (e.g., different wavelengths, polarization states, or illumination patterns) using a single physical hardware platform. This universal illumination approach enables the system to perform various inspection tasks with high reliability while avoiding the complexity and cost of implementing separate dedicated illumination systems for each inspection type.
Data Source
AI summary
An optical inspection system for inspecting a substrate is provided. The system includes an array of cameras configured to acquire a plurality of sets of images as the substrate and the array undergo relative motion with respect to each other. At least one focus actuator is operably coupled to each camera of the array of cameras to cause displacement of at least a portion of each camera that affects focus. A substrate range calculator is configured to receive at least portions of images from the array and to calculate range between the array of cameras and the substrate. A controller is coupled to the array of cameras and to the range calculator. The controller is configured to provide a control signal to each of the at least one focus actuator to adaptively focus each camera of the array during the relative motion.