Dark-field Confocal Microscopy Using Frequency Mismatch Demodulation
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Solution Overview
Problem
Traditional dark-field confocal microscopic measurement technologies for subsurface defects in optical components rely on complex beam shaping mechanisms, which affect lateral and axial resolutions and reduce system stability.
Innovation Solution
A dark-field confocal microscopic measurement apparatus and method based on frequency mismatch demodulation, utilizing a dual-channel waveform generator, modulated illumination, optical scanning, mismatch demodulation, and an axial displacement table, to achieve dark-field imaging without illumination light shaping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a complex beam shaping mechanism is used for subsurface defect detection, then the detection capability is improved, but the lateral and axial resolutions are affected and system stability is reduced
Solution Approach 1:
The patent extracts and removes the complex beam shaping mechanism from the optical path, replacing it with a simple circular aperture stop. This eliminates the problematic components while preserving the dark-field imaging capability through a fundamentally different approach using frequency mismatch demodulation
Solution Approach 2:
The patent changes the operating parameters by using frequency modulated continuous wave (FMCW) illumination with a frequency sweep rate of 10-100 MHz/μs and detecting backscattered light at a frequency offset of 10-50 MHz. This parameter transformation enables subsurface defect detection without requiring complex beam shaping
2Difficulty of detecting and measuring
If a complex beam shaping mechanism is used for subsurface defect detection, then the detection capability is improved, but the system stability is reduced
Solution Approach 1:
The patent removes the complex beam shaping mechanism including any adaptive optics, spatial light modulators, or complex aperture systems, replacing them with a simple circular aperture stop that has no moving parts or complex alignment requirements, thereby dramatically improving system stability
Solution Approach 2:
The patent replaces any mechanical beam shaping components with an electrical frequency modulation system. The illumination source is modulated in frequency rather than in spatial pattern, eliminating mechanical complexity while achieving the same detection objective
3Manufacturing precision
If frequency mismatch demodulation is used instead of beam shaping, then system resolution is improved, but the device complexity changes
Solution Approach 1:
The patent replaces complex optical beam shaping mechanisms with an electrical frequency modulation and demodulation system. The complexity is shifted from the optical path to the signal processing domain, where frequency mismatch demodulation extracts subsurface defect information from the backscattered light signal
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 enhances system resolution, achieves more uniform field of view, and improves defect detection sensitivity through lock-in amplification demodulation technology.
Implementation Method 1
mismatch demodulation module comprises a focusing lens, a pinhole, a PMT (Photomultiplier tube) detector, and a lock-in amplifier
Implementation Method 2
dark-field confocal microscopic measurement apparatus and method based on frequency mismatch demodulation
Implementation Method 3
The returned light of the sample is focused to the pinhole by the focusing lens and collected by the PMT detector
Implementation Method 4
The returned light of the sample is focused to the pinhole by the focusing lens
Data Source
AI summary
Provided are a dark-field confocal microscopic measurement apparatus and method based on frequency mismatch demodulation, relating to a dark-field confocal microscopic measurement apparatus and method. The problems that lateral and axial resolutions are affected and the stability of a microscopic system is reduced because the traditional nondestructive testing technology of subsurface defects in dark-field confocal microscopic measurement relies on a complex beam shaping mechanism are solved. The apparatus includes a dual-channel waveform generator, a modulated illumination module, an optical scanning module, a mismatch demodulation module, and an axial displacement table. A sample is placed on the axial displacement table, and one channel of the dual-channel waveform generator is connected to the modulated illumination module. Laser emitted by the modulated illumination module irradiates the sample through the optical scanning module, and returned light of the sample is collected by the mismatch demodulation module.