Scanning Confocal Polarisation Microscope Sub-Diffraction Imaging
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Solution Overview
Problem
Conventional polarisation microscopy techniques face limitations in achieving high-speed super-resolution imaging of polarisation contrast, particularly in distinguishing subtle differences in polarisation anisotropy, birefringence, luminescence, and diattenuation, especially in opaque materials and living cells with low contrast.
Innovation Solution
A scanning confocal polarisation microscope is developed, incorporating a light source, sample stage, polarisation controller, spatial light modulator, and pin hole to generate a focused light beam with a central peak and sideband peaks, allowing for high-speed acquisition of super-resolution polarisation contrast images by spatially modulating the light beam in amplitude and phase, and using a polarisation controller to set specific polarisation states, with a pin hole to reject scattered light from sidebands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional polarisation microscopy techniques are used, then the imaging capability is provided, but the resolution and contrast for super-resolution polarisation contrast images cannot be achieved
Solution Approach 1:
The illumination beam is segmented into multiple beams using a beam splitting element, where each beam is directed to a different focal point in the sample. This segmentation enables simultaneous multi-point illumination and detection, achieving super-resolution polarisation contrast imaging by combining signals from multiple focal points while maintaining polarisation state information
Solution Approach 2:
A spatial light modulator is introduced as an intermediary element to control and modulate the polarisation state of each individual beam independently. This intermediary device enables precise manipulation of polarisation states for different beams, allowing accurate measurement of polarisation anisotropy, birefringence, luminescence, and diattenuation with enhanced resolution
2Productivity
If high-speed acquisition is implemented, then imaging speed is improved, but the ability to distinguish subtle polarisation anisotropy differences deteriorates
Solution Approach 1:
The polarisation states of multiple beams are pre-configured and set before illumination using the spatial light modulator. By establishing the appropriate polarisation states in advance for each beam, the system can rapidly acquire images without needing to adjust polarisation settings during imaging, thus maintaining both high speed and the ability to distinguish subtle polarisation differences
Solution Approach 2:
The system employs periodic modulation of polarisation states through the spatial light modulator, cycling through different polarisation configurations at high speed. This periodic action allows rapid sampling of different polarisation states, enabling both fast acquisition and precise discrimination of polarisation anisotropy through temporal multiplexing
3Measurement precision
If focused light beam with central peak and sideband peaks is generated, then super-resolution is achieved, but scattered light from sidebands deteriorates image quality
Solution Approach 1:
The system extracts and separates the central peak signal from the sideband peaks using spatial filtering and confocal detection geometry. By taking out only the centrally focused light that passes through the pinhole aperture and rejecting the sideband light, the system achieves super-resolution while eliminating scattered light interference from sidebands
Solution Approach 2:
The confocal detection arrangement provides feedback by detecting only light that passes through the pinhole aperture at the conjugate focal plane. This feedback mechanism selectively accepts light from the central peak while rejecting scattered light from sidebands, maintaining both super-resolution and image quality through iterative signal refinement
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 high-speed acquisition of super-resolution polarisation contrast images with improved resolution and contrast, suitable for imaging opaque materials and living cells, enhancing the ability to distinguish birefringence, luminescence, and diattenuation, and applicable in various modalities including reflection and transmission modes.
Implementation Method 1
a spatial light modulator arranged to receive the light beam from the light source before the sample position, the spatial light modulator being configured to spatially modulate the light beam in amplitude and/or phase so that it focuses the light beam at the sample position in a focal plane with an intensity profile having a central peak with a full width half maximum of less than half the wavelength and sideband peaks
Implementation Method 2
a pin hole arranged to permit only that portion of the light beam to be detected by the detector which has comes from the central peak, while rejecting portions of the light beam that have been scattered by the sample from the sideband peaks
Implementation Method 3
a polarisation controller arranged in the light beam either before or after the sample position and operable to set the polarisation state of the light beam to any one of a defined set of different polarisation states
Data Source
AI summary
A super-resolution scanning confocal polarization contrast microscope is provided. The microscope has a laser light source (1), sample stage (10) for mounting a sample 6 and detector (8). A polarization controller (3) is used to set the polarization state of the light beam to any one of a defined set of different polarization states. A spatial light modulator (5) modulates the light beam in amplitude and/or phase to focus a sub-diffraction-limit central spot on the sample together with unwanted sidebands. A scanning confocal scheme is used with a pin hole 9 in front of the detector (8) so that only that portion of the light is detected which has comes from the central spot, while rejecting light that has been scattered by the sample from the sidebands. Polarization contrast images with sub-diffraction limit resolution can thus be acquired.