Confocal Dark-Field Microscopy With Vortex Beam Optical Sectioning
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Solution Overview
Problem
Traditional dark field microscopes suffer from high background noise and limited tomography ability, which hampers their effectiveness in imaging unstained transparent samples.
Innovation Solution
A confocal scanning dark field microscopy method and device that utilizes a modulated laser beam with a 0-2n π vortex phase to create a hollow focusing spot, conjugated with the objective lens, enabling low background noise and enhanced tomography through a confocal design with a pore to block defocusing signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional wide field dark field microscope is used, then imaging contrast is enhanced, but background noise is high and tomography ability is limited
Solution Approach 1:
The patent segments the illumination into multiple vortex beams with different orders (n=1,2,3...) and spatial locations. Each vortex beam is generated by a separate liquid crystal spatial light modulator, allowing independent control and optimization of each beam's properties. This segmentation enables the system to achieve high contrast imaging while reducing background noise through selective illumination and detection.
Solution Approach 2:
The patent introduces a new dimension by using vortex beams with azimuthal phase dependence (0-2nπφ) instead of conventional plane waves. The vortex phase structure creates a hollow spot focal pattern that provides optical sectioning capability, enabling tomography ability while maintaining high contrast. The higher-order vortex beams (n>3) specifically provide the necessary phase variation for depth discrimination.
2Measurement precision
If confocal design with vortex beam illumination is used, then signal-to-noise ratio and tomography ability are improved, but device complexity increases
Solution Approach 1:
The liquid crystal spatial light modulator serves multiple functions: it generates vortex beams with different orders, controls the phase structure (0-2nπφ), and enables confocal optical sectioning. This multi-functional component replaces what would traditionally require separate optical elements, reducing overall device complexity while maintaining high signal-to-noise ratio and tomography ability.
Solution Approach 2:
The patent changes the phase parameter of the illumination beam from conventional plane wave (0 phase) to vortex beam phase (0-2nπφ). By adjusting the vortex order n and the phase distribution, the system achieves different focal patterns and optical sectioning capabilities. This parameter change enables the confocal design to improve signal-to-noise ratio without requiring complex mechanical adjustments.
3Ease of manufacture
If higher order vortex light (n>3) is used, then inner ring radius of hollow spot increases achieving dark field condition, but imaging resolution may be affected
Solution Approach 1:
The patent uses dynamically controllable liquid crystal spatial light modulators to generate vortex beams with adjustable orders (n=1,2,3...). The system can switch between different vortex orders and adjust the phase distribution in real-time. This dynamic control allows the system to optimize the balance between achieving dark field conditions (requiring higher n) and maintaining imaging resolution (requiring lower n), adapting to different sampling requirements.
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 confocal design improves signal-to-noise ratio and resolution, providing excellent tomography ability for dark field microscopy imaging.
Implementation Method 1
when an applied electric field exceeds a threshold, a liquid crystal molecule exhibit an electrically controlled birefringence effect, therefore, the liquid crystal spatial light modulator only modulates a linear polarized light in one direction
Implementation Method 2
conjugating the modulated laser beam with an entrance pupil of an objective lens of a confocal scanning microscope so that a focusing spot of the objective lens is a hollow spot
Implementation Method 3
only small angle scattered light is collected by the objective lens
Data Source
AI summary
A confocal scanning dark field microscopy imaging method and device, comprising: modulating a phase of a laser beam emitted by a laser into a 0-2ππ vortex phase, where n>3; conjugating the modulated laser beam with an entrance pupil of an objective lens of a confocal scanning microscope, so that a focusing spot of the objective lens is a hollow spot, and an inner ring radius of the hollow spot is greater than a radius of a solid spot without phase modulation; and enabling the confocal scanning microscope to work, thereby achieving dark field microscopy imaging. The present disclosure adopts a confocal design with a pore placed in front of the detector. The plane of the pore is conjugated with the object plane, blocking a defocusing signal from entering the detector.