Fluorescence Surface Inspection with Dynamic Intensity Control
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Solution Overview
Problem
Existing fluorescence laser scanners face limitations when testing highly inhomogeneous surfaces, as detectors have limited dynamic range, leading to detector saturation or damage, and resulting in an increased lower limit of the measurement interval for fluorescence radiation.
Innovation Solution
A method involving two object detections: the first detection identifies object points that may saturate the detector, and a second detection with adjusted excitation intensity and detection sensitivity focuses on these object points to enhance the intensity signal without risking detector saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the excitation radiation intensity is increased to improve the intensity signal for detecting features on highly inhomogeneous surfaces, then the measurement precision is improved, but the detector saturation or damage occurs
Solution Approach 1:
The system dynamically adapts the excitation radiation intensity based on the detected signal characteristics. During a first object detection with initial excitation intensity, the system identifies object points with low signal intensity. For a second object detection, the system selectively increases excitation intensity only for those specific object points, thereby optimizing the intensity signal for weak features while preventing detector saturation at other locations.
Solution Approach 2:
The patent applies different excitation intensities to different spatial locations on the test object surface. Instead of using uniform excitation intensity across the entire surface, the system identifies specific object points that require enhanced illumination and applies higher intensity locally to those regions, while maintaining lower intensity elsewhere to avoid detector saturation.
2Measurement precision
If the excitation radiation intensity is increased to improve the intensity signal, then the measurement precision is improved, but the dynamic range of the detector is exceeded
Solution Approach 1:
The system performs multiple object detections with dynamically adjusted excitation intensities. The first detection uses a conservative intensity to establish baseline measurements without exceeding detector capabilities. Based on the results, the system identifies regions requiring enhanced sensitivity and performs a second detection with selectively increased intensity, thereby effectively utilizing the detector's dynamic range across different spatial regions.
3Measurement precision
If the detection sensitivity is increased to detect weak fluorescence signals, then the measurement precision is improved, but the detector becomes saturated by strong signals from inhomogeneous regions
Solution Approach 1:
The patent segments the detection process into multiple stages and spatial regions. The first object detection segment identifies object points with insufficient signal intensity using initial detection parameters. The second object detection segment focuses specifically on those identified regions with adjusted parameters, thereby segmenting the problem of weak signal detection from the risk of saturation in other regions.
Solution Approach 2:
The system dynamically adjusts detection sensitivity based on spatial location and signal characteristics. Instead of using a fixed high detection sensitivity that would cause saturation, the system increases sensitivity selectively for object points identified as having weak signals, while maintaining lower sensitivity for regions that already produce strong signals.
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 allows for the detection of features on the surface with higher intensity signals, overcoming the limitations of detector saturation and improving the measurement interval for fluorescence radiation.
Implementation Method 1
the laser radiation excites the surface of the test object or a substance on the surface, particularly a contaminant or coating, to fluoresce
Implementation Method 2
an illumination device (4), wherein the illumination device is arranged and configured such that the excitation radiation can be deflected onto a plurality of object points on the surface of the test object
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a method for testing a surface (2) of a test object, comprising the steps of: during a first object detection, illuminating a plurality of object points on the surface (2) of the test object (3) with electromagnetic excitation radiation (7, 7') having an excitation wavelength and a first excitation intensity, detecting an intensity of electromagnetic luminescence radiation for a plurality of pixels with a first detection sensitivity, wherein the luminescence radiation of a pixel is emitted by an object point from the plurality of object points, and outputting an intensity signal for each of the plurality of pixels, wherein the intensity signal represents the intensity of the luminescence radiation of the respective object point and wherein the luminescence radiation has a luminescence wavelength different from the excitation wavelength. According to the invention,that the method further comprises the steps of: determining a first selection, wherein at least for each object point from the first selection, the intensity signal of the first object detection is smaller than an intensity signal threshold value or for each object point from the first selection, an intensity signal to be expected for the first object detection is smaller than the intensity signal threshold value, and during a second object detection, illuminating the first selection of object points on the surface of the test object with the excitation radiation having a second excitation intensity, detecting the intensity of the luminescence radiation for at least one pixel with a second detection sensitivity, wherein the luminescence radiation of each pixel is emitted by one of the first selection of object points, and outputting an intensity signal for the first selection of object points,and generating a first image of the surface of the object with the intensity signals from the second object detection of the first selection of object points, wherein the second object detection occurs at least partially after the first object detection and wherein for each object point from the first selection at least the second intensity of the luminescence radiation is greater than the first intensity of the luminescence radiation or the second intensity of the luminescence radiation is greater than the first intensity of the luminescence radiation expected for the respective object point in the first object detection or the second detection sensitivity is greater than the first detection sensitivity.