Underfilled Fiber Optic Spectrometer for Drift Correction
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Solution Overview
Problem
Optical spectrometers face challenges in maintaining accurate intensity measurements due to LED light source drift and variations caused by contamination, misplacement of samples, and small path lengths for microliter samples, leading to significant errors in absorbance measurements.
Innovation Solution
The optical device includes a converging lens system to focus light onto an optical fiber, ensuring an underfilled launch condition for the receiving fiber, and uses a reference detector to correct for light source fluctuations, along with a sample holder for precise path length control, enabling accurate absorbance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LED light source is used for spectroscopy, then device complexity is reduced and ease of manufacture is improved, but light source drift occurs leading to measurement precision degradation
Solution Approach 1:
The patent employs a feedback mechanism by using a reference detector to continuously monitor the light source intensity and automatically correct for drift. The system measures the reference wavelength intensity, compares it to expected values, and applies correction factors to compensate for LED intensity variations, thereby maintaining measurement precision while using the simpler LED light source
Solution Approach 2:
The patent changes the operational parameters by selecting specific reference wavelengths where the sample does not absorb light, allowing the system to monitor light source drift independently of sample absorption. This parameter selection enables separation of light source variations from sample characteristics, maintaining measurement accuracy
2Device complexity
If optical fiber is used to transmit light through microliter samples, then device complexity is reduced, but path length control precision deteriorates leading to measurement errors
Solution Approach 1:
The patent introduces an intermediary substance (refractive index matching fluid) between the optical fiber and sample to improve light coupling and enable more precise path length control. This intermediary medium facilitates better optical contact and reduces refraction losses, allowing accurate spectroscopic measurements with simplified fiber-based geometry
Solution Approach 2:
The patent changes the refractive index parameter by using index-matching fluids to optimize light transmission through the sample. By matching the refractive indices at interfaces, the system minimizes reflection and scattering losses, improving measurement precision while maintaining simple fiber-based sample handling
3Measurement precision
If underfilled launch condition is used, then measurement precision is improved by stabilizing intensity measurements, but light source utilization efficiency decreases
Solution Approach 1:
The patent extracts only the necessary portion of light from the LED source by using an underfilled launch condition. By limiting the launch spot size to a fraction of the optical fiber core area, the system achieves stable intensity measurements with reduced sensitivity to alignment variations, while the reference detector compensates for overall intensity variations to maintain measurement accuracy
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 stabilizes intensity measurements by minimizing the impact of LED drift and sample-related variations, providing reliable absorbance data for microliter samples with reduced error correction needs.
Implementation Method 1
a converging lens device mounted to receive light that is substantially collimated and to focus the received light onto an entrance face of a transmitting optical fiber
Implementation Method 2
The light is kept in the core by total internal reflection causing the fiber to act as a waveguide
Implementation Method 3
Optical spectrometers measure the intensity of light at one or more wavelengths to determine certain characteristics of samples... UV-Vis spectroscopy generally measures the absorption or reflectance of a sample in the ultraviolet-visible spectral region
Data Source
AI summary
An optical device is provided that includes a converging lens device, a transmitting optical fiber, a sample holder, and a receiving optical fiber. The converging lens device focuses light onto the transmitting optical fiber, which receives the focused light through an entrance face and transmits the light from an exit face, through a sample, and onto the receiving optical fiber. The sample holder holds the sample for analysis. The receiving optical fiber receives the light through an entrance face of the receiving optical fiber after transmission through the sample. The converging lens device is positioned to focus the light onto the entrance face of the transmitting optical fiber such that a half-angle of the angular distribution of the focused light that reaches the entrance face of the transmitting optical fiber is selected to underfill an entrance aperture of the entrance face of the receiving optical fiber in both a spatial dimension and an angular dimension.