Optical Cell Concentration Calibration Across Different Cell Counters
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Solution Overview
Problem
Conventional optical detection assemblies for fluid analysis suffer from inconsistent measurements due to varying light transport in plastic tubing and the use of single photodiodes, leading to inconsistent cell concentration readings across differently configured cell counters.
Innovation Solution
An optical detection assembly with a light source, light detector array, and controller that applies an adjustment equation to correct for configuration differences between cell counters, using a correlation curve derived from a first cell counter to determine an adjusted cell concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single photodiode is used to detect light exiting the vessel, then the device complexity is reduced, but the measurement precision deteriorates due to inability to capture dispersed light from turbid media
Solution Approach 1:
The single photodiode detector is segmented into multiple photodiodes arranged in an array, allowing different regions of the dispersed light to be detected simultaneously. This segmentation enables capture of light at multiple positions, improving measurement precision while maintaining reasonable device complexity through modular architecture.
Solution Approach 2:
The detection approach transitions from a single-point detection (zero-dimensional) to multi-point detection along the light path (one-dimensional spatial distribution). By arranging photodiodes in an array along the expected light dispersion path, the system captures the spatial profile of dispersed light, significantly improving measurement precision for turbid media.
2Ease of manufacture
If conventional plastic tubing is used for fluid flow, then the ease of manufacture is improved, but the measurement precision deteriorates due to varying light transport caused by refractive index differences and surface formation variations
Solution Approach 1:
A index-matching gel is introduced as an intermediary substance between the plastic tubing and the light path. This gel has a refractive index that bridges the gap between air (n≈1.0) and plastic (n≈1.3-1.5), reducing the refractive index mismatch and minimizing light scattering at the tubing interface, thereby improving measurement precision while allowing continued use of flexible plastic tubing.
Solution Approach 2:
The refractive index parameter of the medium between the tubing and light path is changed from air to index-matching gel. This parameter change optimizes light transport through the plastic tubing by reducing refraction and internal reflection, leading to more consistent and accurate measurements.
3Measurement precision
If an empirically derived correlation curve from one cell counter configuration is used, then the adaptability to different cell counter configurations is reduced, but the measurement precision for that specific configuration is maintained
Solution Approach 1:
The correlation curve parameters are dynamically adjusted based on the specific cell counter configuration being used. By detecting configuration parameters (such as detector sensitivity, light source characteristics, or processing parameters) and modifying the correlation curve accordingly, the system maintains high measurement precision across different cell counter configurations without requiring separate calibration curves for each.
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
Provides consistent cell concentration measurements by accounting for configuration variations, ensuring accurate readings across different cell counters.
Implementation Method 1
A typical optical detection assembly includes a light source (e.g., a laser or a light-emitting diode) configured to emit light into a fluid-containing vessel of the fluid flow circuit, with a light detector (e.g., a photodiode) configured to receive light exiting the vessel
Implementation Method 2
The light detector transmits a signal to a controller based upon the light it has received, with the controller using the signal to determine one or more properties of the fluid
Implementation Method 3
When light is incident upon plastic tubing, the transport of light into the tubing lumen may vary according to Snell's Law depending on the refractive indices of the materials and incident light angles formed by the tubing surface. The refractive index of air (which is approximately 1) and the refractive index of plastic (which may typically be approximately 1.3 to 1.5) are quite different
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method of determining a cell concentration of a subject fluid includes first determining an unadjusted cell concentration of each of a plurality of fluids based on an intensity of light emitted through the fluid and a correlation curve derived using a first cell counter. A measured cell concentration obtained for each fluid from a second cell counter is then plotted against the unadjusted cell concentration to create a curve represented by an equation that is selected to be used as an adjustment equation. Light is then emitted through the subject fluid, with at least a portion of the light exiting the subject fluid being received. An unadjusted cell concentration of the subject fluid is determined based on the correlation curve and the intensity of the received light. The adjustment equation is then applied to the unadjusted concentration to determine an adjusted cell concentration of the subject fluid.