Single-Beam Photothermal Detection for Absorptive Defects
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current defect detection methods for optical elements in high-power laser systems, such as microscopic scattering dark field imaging and photothermal scanning imaging, are inadequate for detecting absorptive defects like metal and nonmetal impurities, as they lack sensitivity or are prone to measurement anomalies due to environmental vibrations and sample tilt.
Innovation Solution
A single-beam photothermal measurement apparatus and method that uses a common-path or non-common-path configuration to detect absorptive defects by measuring power changes on the edge of a beam spot, featuring a laser, beam splitter, chopper, polarization beam splitter, galvanometer scanner, and photoelectric detector, which stabilizes measurements and enhances sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional photothermal scanning imaging technology is used to detect absorptive defects, then measurement sensitivity is improved, but device complexity increases and measurement stability deteriorates due to environmental vibration and sample tilt
Solution Approach 1:
The patent merges the pump beam and probe beam into a single beam path, eliminating the need for separate beam alignment systems. This single-beam configuration integrates both the heating function (pump) and detection function (probe) into one optical path, significantly simplifying the optical structure while maintaining high detection sensitivity for absorptive defects
Solution Approach 2:
The single beam serves multiple functions simultaneously: it acts as both the pump beam (heating the defect) and the probe beam (detecting the thermal deformation). This multi-functional design eliminates the complexity of aligning and maintaining two separate beam paths, while still achieving high sensitivity detection of absorptive defects
2Measurement precision
If traditional photothermal scanning imaging technology is used, then absorptive defects can be detected, but measurement stability deteriorates due to environmental vibration and sample tilt affecting beam spot overlapping
Solution Approach 1:
By merging the pump and probe functions into a single beam, the patent eliminates the relative alignment requirements between two beams. The single beam inherently maintains perfect overlap with itself, making the measurement immune to environmental vibrations and sample tilt that would otherwise cause misalignment between separate pump and probe beam spots
Solution Approach 2:
The patent uses the reflected light from the same beam path as the probe signal, effectively copying the pump beam's path for detection purposes. This self-referential approach ensures that any environmental disturbances affect both the heating and detection paths equally, maintaining measurement stability
3Measurement precision
If two-beam photothermal scanning is used, then absorptive defects can be detected with high sensitivity, but ease of operation deteriorates due to difficult light path adjustment and alignment
Solution Approach 1:
The patent combines the pump beam and probe beam into a single optical path, eliminating the complex alignment procedures required for two separate beams. This single-beam configuration is much easier to set up and adjust, as it requires only one beam path alignment instead of coordinating two independent beam paths
Solution Approach 2:
The single beam automatically serves both pumping and probing functions without requiring external alignment adjustments. The system is self-aligning in the sense that the beam naturally overlaps with itself, eliminating the need for operators to perform complex light path coordination
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 solution provides a stable and sensitive detection of absorptive defects, avoiding anomalies caused by environmental vibrations and sample tilt, and improves measurement sensitivity by using a simple optical structure that is easy to align and adjust.
Implementation Method 1
The traditional photothermal scanning imaging technology is based on the photothermal effect, where the surface of the element is irradiated by pump laser to generate thermal deformation
Implementation Method 2
the chopper, the polarization beam splitter, the quarter-wave plate, the mirror, the galvanometer scanner, and the scanning lens are sequentially arranged along a direction of the strongly transmitted light; the strongly transmitted beam is modulated by the chopper
Implementation Method 3
the chopper, the polarization beam splitter, the quarter-wave plate, the mirror, the galvanometer scanner, and the scanning lens are sequentially arranged along a direction of the strongly transmitted light; the strongly transmitted beam is modulated by the chopper; a modulated incident light passes through the polarization beam splitter to output p-polarized light
Implementation Method 4
a modulated incident light passes through the polarization beam splitter to output p-polarized light and passes through the quarter-wave plate to output circularly polarized light
Implementation Method 5
after the focused beam passes through the obstruction aperture, the beam on the edge of the beam spot is received by the photoelectric detector
Implementation Method 6
The modulation frequency of the chopper is taken as a reference signal and is input into a second input end of the lock-in amplifier via a cable; a signal collected by the photoelectric detector is taken as a measurement signal and is input into a first input end of the lock-in amplifier
Implementation Method 7
the beam splitter divides an incident beam into weakly reflected light and strongly transmitted light with different intensities
Implementation Method 8
the circularly polarized light passes through the galvanometer scanner and the scanning lens, and then is focused on the surface of the sample
Data Source
AI summary
A single-beam photothermal measurement apparatus and a measurement method for absorptive defects. The apparatus comprises a common-path-type structure and a non-common-path-type structure. The present invention is simple in optical structure and convenient to align and adjustment. The measurement result is stable, and measurement signal anomalies caused by environmental vibration and sample tilt are avoided. By detecting a power change on the edge of a beam spot, the measurement sensitivity of a system is remarkably improved.