Convex Sample Cell and Aspheric Lens for Particle Characterization
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Solution Overview
Problem
Existing particle characterization systems face challenges in achieving a high signal-to-noise ratio due to optical noise from sources like bubbles, detritus, and chemical leaching, particularly in water-based dispersants, which affects the detection of scattered light at various angles, leading to inaccurate particle size distribution measurements.
Innovation Solution
A particle characterization apparatus with a sample cell featuring a convex external surface on one or both walls allows light scattered at high angles to escape without total internal reflection, using a collecting lens with an aspheric surface to correct field curvature and improve light collection, and a processor to distinguish between particle and bubble scattering by analyzing the ratio of forward to backscattered light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sample cell uses flat parallel walls, then the structure is simple and easy to manufacture, but light scattered at high angles undergoes total internal reflection causing optical noise and reduced signal-to-noise ratio
Solution Approach 1:
The sample cell walls are designed with curved surfaces instead of flat surfaces. Specifically, at least one wall has a curved external surface that allows light scattered at angles greater than the critical angle to escape without total internal reflection, thereby reducing optical noise and improving the signal-to-noise ratio while maintaining manufacturing feasibility
Solution Approach 2:
The invention changes the geometric parameter of the sample cell walls from flat to curved. This parameter change modifies the light path and escape angles, enabling high-angle scattered light to exit the cell without undergoing total internal reflection, thus improving measurement precision
2Measurement precision
If the sample cell is inclined at 45 degrees to the light beam, then high angle scattered light can escape without total internal reflection, but low angle scattered light experiences increased reflections and optical noise
Solution Approach 1:
Instead of inclining the entire sample cell at 45 degrees, the invention applies curvature only to the external surface of at least one wall. This localized curvature allows high-angle scattered light to escape without total internal reflection while keeping the overall cell orientation aligned with the light beam, thereby avoiding increased reflections of low-angle scattered light
Solution Approach 2:
The curved surface is applied locally to specific walls or regions of the sample cell rather than inclining the entire cell structure. This local application of curvature targets only the escape path of high-angle scattered light, leaving the optical path for low-angle scattered light unaffected and minimizing optical noise
3Measurement precision
If a curved surface is used on the sample cell wall, then high angle scattered light can escape without total internal reflection, but the manufacturing complexity increases
Solution Approach 1:
The invention uses a curved external surface on the sample cell walls, which can be implemented as a simple cylindrical or spherical section that is relatively easy to manufacture using standard glassblowing or molding techniques. This approach achieves the optical benefit of enabling high-angle light escape while keeping the structural complexity manageable
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 configuration enhances the signal-to-noise ratio, enables detection of a broader range of scattering angles, and effectively differentiates between particle and bubble scattering, leading to more accurate particle size distribution analysis.
Implementation Method 1
light scattered at relatively high angles (above the critical angle for a water/air interface) can escape from the sample cell without total internal reflection at the exit interface of the cell
Implementation Method 2
a collecting lens with an aspheric surface to correct field curvature and improve light collection
Implementation Method 3
the light source is operable to illuminate a sample comprising dispersed particles within the sample cell with a light beam along a light beam axis, so as to produce scattered light by interactions with the sample
Implementation Method 4
the detector is configured to detect scattered light leaving the sample cell
Data Source
AI summary
A particle characterization apparatus is disclosed comprising: a light source; a sample cell; a collecting lens and a detector. The light source is operable to illuminate a sample comprising dispersed particles within the sample cell with a light beam along a light beam axis. The light beam axis passes through a first wall of the sample cell, through the sample, and through a second wall of the sample cell, so as to produce scattered light by interactions with the sample. The detector is configured to detect light scattered from the sample. The second wall of the sample cell comprises a lens with a convex external surface through which the light beam axis passes. The collecting lens is arranged to collect and focus scattered light leaving the sample cell onto the detector, and comprises an aspheric surface.