Defect Inspection Device Nonlinearity Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing defect inspection devices face challenges in detecting both minute and relatively large defects due to saturation issues with photoelectron-multiplier tubes, which affect the accuracy of defect size estimation and positional measurement.
Innovation Solution
A defect inspection device incorporating a pulse oscillated light source, illumination unit, scanning unit, light converging unit, photoelectric conversion unit, AD conversion unit, linear restoration unit, defect detection unit, and processing unit to correct nonlinearity and enhance detection sensitivity, allowing for simultaneous detection of both minute and large defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor gain of the detector and the power density of the illumination are improved, then the sensitivity for detecting minute defects is improved, but saturation of the detection signal from relatively large defects is caused
Solution Approach 1:
The patent applies dynamic adjustment of sensor gain based on the detected signal strength. The gain is set to a first gain level when the reflected light amount is below a threshold, and switched to a second gain level when the reflected light amount exceeds the threshold, preventing saturation while maintaining sensitivity for minute defects
Solution Approach 2:
The patent changes the operating parameters of the detector dynamically. By adjusting the sensor gain parameter based on the illumination power density and detected signal levels, the system adapts to different defect sizes and maintains optimal performance across the entire detection range
2Measurement precision
If the sensor gain and illumination power density are increased to detect fine defects, then the detection sensitivity is improved, but the relative positional relationship between laser irradiation position and large defect cannot be grasped
Solution Approach 1:
The patent dynamically adjusts the sensor gain based on the detected signal characteristics. When large defects are detected with high reflected light amounts, the system switches to a lower gain level that preserves the spatial information and positional relationship, while maintaining high gain for minute defect detection when needed
3Measurement precision
If a photoelectron-multiplier tube with high current amplification is used to detect minute defects, then the detection sensitivity is improved, but the light-receiving area becomes large and parallel detection is prevented
Solution Approach 1:
The patent segments the detection function by using multiple detectors with different characteristics. One detector is optimized for high current amplification to detect minute defects, while another detector with smaller light-receiving area handles the positioning and characterization of larger defects, enabling parallel processing of different defect types
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
Enables accurate detection and measurement of both minute and large defects by correcting nonlinearity and enhancing sensitivity, improving the precision of defect size and position estimation.
Implementation Method 1
a pulse oscillated light source, an illumination unit that guides light output from the light source to a sample
Implementation Method 2
a light converging unit that converges light reflected from the sample
Implementation Method 3
a light converging unit that converges light reflected from the sample
Implementation Method 4
a first photoelectric conversion unit that outputs an electric signal corresponding to the light converged by the light converging unit
Data Source
AI summary
The invention includes a pulse oscillated light source, an illumination unit that guides light output from the light source to a sample, a scanning unit that controls a position at which the sample is scanned by the illumination unit, a light converging unit that converges light reflected from the sample, a first photoelectric conversion unit that outputs an electric signal corresponding to the light converged by the light converging unit, an AD conversion unit that converts the electric signal output from the first photoelectric conversion unit into a digital signal in synchronization with pulse oscillation of the light source, a linear restoration unit that processes a digital signal converted by the AD conversion unit in synchronization with a pulse oscillation output by the AD conversion unit and corrects nonlinearity of the first photoelectric conversion unit, a defect detection unit that detects a defect of the sample based on an output of the linear restoration unit, and a processing unit that obtains and outputs a position and a size of the defect detected by the defect detection unit.