Particle Characterisation Instrument Zero-Angle Detection
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Solution Overview
Problem
Conventional light scattering instruments struggle to accurately measure zero-angle and back-scattered light due to the challenge of separating scattered light from incident light, especially at low angles, which limits the accuracy of particle characterization.
Innovation Solution
The instrument modifies the light beam to create a dark region along the illumination axis, allowing zero-angle and π-angle scattered light to be detected without interference from the incident light, using techniques such as diffraction, refraction, or obscuration to form an effective beam that diverges and creates a dark region for detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional light scattering instrument uses a light source to illuminate a sample along an illumination axis, then the sample can be effectively illuminated for scattering measurements, but the incident light obscures the detection of zero-angle and low-angle scattered light
Solution Approach 1:
The optical system is segmented into distinct functional zones: an illumination path that delivers light to the sample, and a detection path that collects scattered light at specific angles. The detection optics are positioned and configured to selectively receive scattered light while excluding the direct illumination beam, creating spatial separation between illumination and detection functions.
Solution Approach 2:
The detection system is designed with angularly selective detection capabilities, where detectors are positioned to receive light at specific scattering angles (including zero-angle and low-angle scattered light) while the illumination maintains full intensity along the illumination axis. This creates different optical qualities in different spatial regions.
2Measurement precision
If the detector is positioned to detect scattered light at low angles near the illumination axis, then zero-angle and low-angle scattered light can be measured, but the incident light interferes with the detection
Solution Approach 1:
The harmful incident light is extracted or removed from the detection path through careful optical design. The detection system is configured to collect scattered light at specific angles while the incident beam is directed along a different path, effectively separating the useful scattered light signal from the harmful incident light background.
Solution Approach 2:
Optical elements such as lenses, mirrors, and apertures act as intermediaries to guide scattered light from the sample to the detector while blocking or excluding the direct incident beam. These intermediary components enable the detector to receive only the desired scattered light signal.
3Illumination intensity
If the incident light beam is used to illuminate the sample, then the sample is effectively illuminated, but back-scattered light at 180° cannot be detected because it is coincident with the incoming incident light
Solution Approach 1:
Instead of trying to detect back-scattered light in the traditional forward illumination geometry where the detector would be obscured by the incident beam, the system inverts the approach by using dual-sided illumination or positioning detectors on both sides of the sample cell, allowing back-scattered light to be collected from the illumination side where the optical path is clear.
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 enables precise measurement of zero-angle and π-angle scattered light, improving the accuracy of particle characterization by reducing interference and allowing for the detection of light that would otherwise be obscured by the incident beam.
Implementation Method 1
modifying the light to produce a modified beam... using techniques such as diffraction, refraction, or obscuration to form an effective beam
Implementation Method 2
modifying the light to produce a modified beam... using techniques such as diffraction, refraction, or obscuration to form an effective beam
Data Source
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AI summary
A particle characterisation instrument (200), comprising a light source (201), a sample cell (202), an optical element (204) between the light source (201) and sample cell (202) and a detector (203). The optical element (204) is configured to modify light from the light source (201) to create a modified beam (207), the modified beam (207): a) interfering with itself to create an effective beam (208) in the sample cell (202) along an illumination axis (206) and b) diverging in the far field to produce a dark region (209) along the illumination axis (206) that is substantially not illuminated at a distance from the sample cell (202). The detector (203) is at the distance from the sample cell (202), and is configured to detect light scattered from the effective beam (208) by a sample in the sample cell (202), the detector (203) positioned to detect forward or back scattered light along a scattering axis (306) that is at an angle of 0° to 10° from the illumination axis (206).