Optical Fiber Holder for Variable Path Length Absorbance
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Solution Overview
Problem
Conventional spectrophotometric methods are impractical for measuring small sample volumes due to difficulties in creating and cleaning small sample cells, and achieving optimal signal-to-noise characteristics for absorbance measurements.
Innovation Solution
An optical apparatus with a motor-driven linear actuator and eddy current sensor system that adjusts the distance between optical fibers to vary the light path length, allowing precise control of optical elements for accurate absorbance measurements in a surface-tension-held sample environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional cuvettes with 1 cm path length are used, then accurate absorbance measurements can be obtained, but small sample volumes (1-2 microliters) cannot be accommodated and cleaning between samples is difficult
Solution Approach 1:
The patent employs a motor-driven linear actuator that dynamically adjusts the distance between two optical fibers, enabling the path length to be varied from 0.1 mm to 10 mm. This dynamic adjustment allows the system to accommodate different sample volumes while maintaining measurement accuracy, resolving the contradiction between fixed path length requirements and variable sample volume needs
Solution Approach 2:
The system changes the critical parameter of path length from a fixed 1 cm value to a variable parameter ranging from 0.1 mm to 10 mm. By using a linear actuator to precisely control fiber separation distance, the system can optimize path length for each specific sample volume, enabling accurate measurements with minimal sample quantities
2Measurement precision
If path length is increased to improve signal-to-noise ratio, then absorbance measurement precision improves, but sample volume requirements increase
Solution Approach 1:
The motor-driven linear actuator provides dynamic control of fiber separation distance, allowing the path length to be optimized for each measurement. This enables the system to achieve the optimal path length for maximum signal-to-noise ratio while using minimal sample volume, as the path length can be precisely adjusted rather than requiring a fixed large volume
3Measurement precision
If optical fiber distance is precisely controlled to minimize circular error, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent replaces manual positioning and mechanical alignment systems with a motor-driven linear actuator coupled to an eddy current sensor. This substitution provides precise, automated control of fiber separation distance, minimizing circular error through electronic control rather than manual mechanical adjustment, thereby achieving high precision while maintaining reasonable device complexity
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 absorbance measurements with optimal signal-to-noise characteristics for small sample volumes (0.005 to 2.0 Absorbance Units) using path lengths down to 10 microns, minimizing circular error and facilitating precise concentration calculations.
Implementation Method 1
a motor mechanically coupled to the optical fiber holder and operable so as to move the optical fiber holder so as to adjust the distance, P
Implementation Method 2
a motor-driven linear actuator and eddy current sensor system that adjusts the distance between optical fibers
Implementation Method 3
provide and transmit light through the droplet for measurement, and to collect light for measurement, at least one of the surfaces may have a portion of optical measurement quality. This may be accomplished by providing at least a portion of at least one of the surfaces as a polished end of an optical fiber
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A
AI summary
An apparatus is described in which an optical fiber is mounted within a fiber optic holder which includes the non-rotating shaft of a linear actuator. The fiber holder may be held captive in order to restrain the fiber holder and, consequently, the fiber mounted therein, from rotating during operation of the linear actuator, thereby resulting in linear travel with minimal rotational effects and minimal change in optical alignment of the fiber during travel. In addition, an optical path length sensor in conjunction with an optimize dabsorbance method of operation is utilized herein to provide micron precision of the displacement between respective receiving and transmission fibers so as to enable precise absorbance measurements from about 0.005 up to about 2.0 Absorbance Units for any given path length.