Surface Plasmon Microscope Optics for Faster Refractive Index Sensing
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Solution Overview
Problem
Existing surface plasmon microscopes face challenges in achieving a simplified configuration and reduced measurement time while accurately obtaining refractive index information, with some requiring complex optical systems and others having lengthy measurement times.
Innovation Solution
A surface plasmon microscope design that includes a light source, illumination and detection optical systems, a photodetector, and an operation unit to simplify configuration and reduce measurement time by using radial polarization and a low frequency cut filter to enhance sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an imaging sensor is used to image the reflected light intensity distribution on the exit pupil plane, then the refractive index information can be accurately obtained, but the measurement time becomes long and analysis complexity increases
Solution Approach 1:
The patent extracts only the essential information (refractive index) from the reflected light intensity distribution by using a photodetector to measure intensity at specific positions corresponding to the resonance angle, rather than capturing the entire intensity distribution image. This extraction approach maintains measurement accuracy while significantly reducing measurement time and analysis complexity.
Solution Approach 2:
The patent uses a photodetector to create a simplified copy of the essential information from the complex reflected light intensity distribution. By measuring the intensity at the resonance angle position, the system creates a reduced representation that contains the necessary refractive index information without requiring full image capture and analysis.
2Measurement precision
If a ring-shaped light illumination system is used to illuminate the entrance pupil plane, then the resonance angle can be obtained from reflected light intensity, but the optical system becomes complicated
Solution Approach 1:
The patent makes the objective lens perform multiple functions: it serves as both the illumination lens and the detection lens. By using the same lens for both illuminating the metal thin film and detecting the reflected light, the system eliminates the need for separate ring-shaped illumination optics, thereby reducing overall system complexity while maintaining measurement precision.
Solution Approach 2:
The patent merges the illumination path and detection path by using a single objective lens for both functions. The light source illuminates the metal thin film through the objective lens, and the reflected light is detected through the same lens, combining what would traditionally be separate optical components into a unified system.
3Measurement precision
If the reflected light intensity distribution is imaged on the exit pupil plane, then refractive index information can be obtained, but the configuration becomes complex and analysis is required
Solution Approach 1:
The patent extracts only the necessary intensity information at the resonance angle position from the reflected light, using a photodetector to measure intensity at a specific location in the exit pupil plane. This extraction approach eliminates the need for complex image processing while maintaining accurate refractive index measurement.
Solution Approach 2:
The patent introduces a photodetector as an intermediary device that converts the optical information (reflected light intensity at resonance angle) into electrical signals for processing. This intermediary simplifies the system by directly measuring the essential information without requiring complex optical imaging and analysis systems.
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
The design achieves a simplified configuration and reduced measurement time while maintaining high sensitivity and accuracy in refractive index measurements, improving upon existing systems by enhancing sensitivity and reducing noise interference.
Implementation Method 1
a phenomenon in which the reflectance rapidly decreases as described above is caused by the fact that, when a wavenumber of a surface plasmon, which is an oscillation of free electron gas localized on the surface of the metal thin film, and a wavenumber of an evanescent wave of the incident light coincide with each other, a resonance phenomenon between the two occurs, and the energy of the light moves to the metal surface
Implementation Method 2
an illumination optical system for focusing the light output from the light source on the metal thin film through an objective lens to generate a surface plasmon resonance
Implementation Method 3
a detection optical system for guiding reflected light generated by focused illumination on the metal thin film by the illumination optical system through the objective lens
Implementation Method 4
a photodetector for receiving the reflected light arriving through the detection optical system, and detecting an intensity of the reflected light
Data Source
AI summary
An surface plasmon microscope includes a light source, a polarization element, a beam splitter, an objective lens, a photodetector, an operation unit, and the like. An illumination optical system including lenses, the polarization element, the beam splitter, and the objective lens guides light output from the light source to converge the light by the objective lens, and illuminates a metal thin film with the light from a lower surface side of a transparent substrate and focuses the light on the metal thin film to generate a surface plasmon resonance. A detection optical system including the objective lens, the beam splitter, and a lens guides reflected light generated by the focused illumination on the metal thin film to the photodetector. The operation unit acquires refractive index information of a sample disposed in contact with the metal thin film based on the reflected light intensity detected by the photodetector.