Neutral Density Filter Stack for Wider Fluorescence Range
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Solution Overview
Problem
Existing fluorescence measurement systems face limitations in dynamic range due to inner-filter effects, particularly at higher fluorophore concentrations, leading to unreliable and inaccurate measurements, and require multiple samples to cover the desired range.
Innovation Solution
A system utilizing a stack of neutral density filters positioned between the excitation light source and the sample to modulate light intensity, combined with absorbance measurements, to extend the dynamic range and maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If higher concentrations of fluorophores are used to extend the measurement range, then the measurable concentration range is extended, but inner-filter effects increase causing measurement inaccuracy
Solution Approach 1:
The system dynamically adjusts the excitation light intensity using a neutral density filter wheel that can be rotated to select different filter positions. This allows the excitation intensity to be adapted to different fluorophore concentrations, maintaining measurement accuracy across a wide concentration range by preventing inner-filter effects at high concentrations while providing sufficient excitation at low concentrations.
Solution Approach 2:
The system changes the optical density parameter of the neutral density filters to control the amount of excitation light reaching the sample. By selecting filters with appropriate optical densities, the system can reduce excitation intensity when measuring high concentration samples to eliminate inner-filter effects, thereby extending the measurable concentration range while maintaining accuracy.
2Adaptability or versatility
If multiple samples with different concentrations are prepared to cover the full dynamic range, then the measurement coverage is extended, but the number of samples and measurement time increase
Solution Approach 1:
The neutral density filter wheel enables a single fluorescence measurement system to function across multiple concentration ranges by providing adjustable excitation intensities. Instead of requiring separate measurement systems or multiple prepared samples for different concentration ranges, this universal approach allows one system to accurately measure samples across the entire dynamic range by selecting appropriate filter settings.
Solution Approach 2:
The system performs preliminary selection of the appropriate neutral density filter based on the expected or measured fluorophore concentration before taking the fluorescence measurement. This preliminary action optimizes the excitation intensity for the specific sample, allowing accurate measurement in a single step without requiring serial dilutions or multiple measurements of different sample preparations.
3Measurement precision
If the excitation light intensity is increased to improve detection sensitivity, then the limit of detection is lowered, but inner-filter effects worsen at higher fluorophore concentrations
Solution Approach 1:
The system dynamically adjusts excitation light intensity through the neutral density filter wheel to match the fluorophore concentration being measured. For low concentration samples, higher intensity excitation (with lower optical density filters) provides the sensitivity needed for detection. For high concentration samples, lower intensity excitation (with higher optical density filters) prevents inner-filter effects, thus optimizing detection conditions across all concentration ranges.
Solution Approach 2:
The neutral density filters act as an intermediary between the light source and the sample, controlling the amount of excitation light that reaches the fluorophores. This intermediary element allows the system to decouple the light source intensity from the actual excitation intensity at the sample, enabling precise control to avoid inner-filter effects while maintaining detection sensitivity.
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 accurate and reliable fluorescence measurements over a broader range by minimizing inner-filter effects and reducing the need for multiple samples, while allowing integration with absorbance techniques for a comprehensive measurement solution.
Implementation Method 1
A Neutral Density Filter Stack (NDFS) that diminishes inner-filter effects of fluorescence that occur at higher concentrations of fluorophores
Implementation Method 2
Fluorescence spectroscopy has been used to carry out an array of measurements to characterize features of liquid samples
Data Source
AI summary
A system and method to extend a dynamic range of fluorescence measurements. The system includes a neutral density filter stack apparatus including a plurality of neutral density filters. The neutral density filter stack modulates the intensity of light from a source. This modulation improves the ability to detect emissions from a wider-range of fluorophore concentrations, specifically addressing inner-filter effects at higher concentrations that would normally require sample dilution. It can be used in a system in which absorbance and fluorescence measurements are carried out, wherein the intensity of the light source is modulated with the apparatus for the fluorescence measurements. In this hybrid system, the stack modulates the intensity of the excitation light source for fluorescence measurements to be made at very low concentrations of analyte. The hybrid system also includes optics for absorbance measurements to be made at concentrations of analyte that are higher than those detected by fluorescence.