X-ray Inspection Calibration Using Air Reference Subtraction
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Solution Overview
Problem
X-ray inspection systems for electronic assemblies, such as circuit cards and printed circuit boards, face challenges in reducing false call rates due to systematic errors and random noise, which affect the stability, reproducibility, and consistency of imaging results.
Innovation Solution
A calibration system that uses air reference values to calibrate image data, specifically by subtracting air image grayscale values from inspection images to eliminate systematic errors, and employs a software-based approach to correct for pixel sensitivity variations and flux changes, thereby improving image homogeneity and reducing the 1/r2 effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used, then systematic errors are reduced, but false call rate remains high due to random noise and stability issues
Solution Approach 1:
The patent performs preliminary calibration actions by capturing reference images of known good joints before actual inspection begins. These reference images are stored and used for comparison during inspection, allowing the system to pre-establish baseline measurements and reduce false calls caused by drift over time
Solution Approach 2:
The system implements feedback mechanisms by continuously comparing inspection results against stored reference images and adjusting calibration parameters accordingly. This feedback loop enables the system to compensate for random noise and maintain reliable measurements even as system conditions change during operation
2Productivity
If inspection systems operate over extended periods, then productivity increases, but systematic errors accumulate causing results to drift
Solution Approach 1:
The patent implements periodic recalibration by automatically capturing new reference images at scheduled intervals or after a certain number of inspections. This periodic action resets systematic errors before they can accumulate to problematic levels, maintaining measurement stability over extended operational periods
Solution Approach 2:
The system performs preliminary checks by comparing current measurements against stored references before final inspection decisions are made. This preliminary comparison allows early detection of drift and triggers recalibration before stability is significantly compromised
3Productivity
If multiple inspection systems are deployed, then productivity increases, but consistency across systems decreases due to systematic errors
Solution Approach 1:
The patent creates a universal calibration reference that can be used across multiple inspection systems. By establishing common reference images and calibration procedures that all systems follow, the patent enables consistent measurements across different devices, allowing productivity to scale without sacrificing precision
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
The calibration system effectively reduces systematic errors, improves image quality, and extends the useful life of the X-ray source by compensating for tube output fluctuations, resulting in lower false call rates and increased machine-to-machine stability.
Implementation Method 1
The inspection devices may use X-ray energy to generate the images
Implementation Method 2
specifically by subtracting air image grayscale values from inspection images to eliminate systematic errors
Data Source
AI summary
According to one embodiment, a calibration system for calibrating image data produced by an imaging system is provided. The calibration system includes a processor configured for: receiving the image data from the imaging system; receiving a plurality of reference values from the imaging system; and calibrating the image data using the reference values. The reference values correspond to air image data produced by the imaging system.