TIR Microscope Coupling Device for Automatic Evanescent Field Control
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Solution Overview
Problem
Current microscopes for total internal reflection microscopy lack the ability to automatically set evanescent illumination when the beam is directed rotation-symmetrically, making it difficult to determine and control the penetration depth of the evanescent field due to unknown refractive indices of specimens.
Innovation Solution
A microscope with a coupling device featuring a mirror with a hole in the illumination beam path to redirect and detect reflection light, allowing for the determination of quantifiable parameters of the evanescent illumination and field, enabling automatic adjustment of the evanescent illumination based on the specimen's refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a mirror with a hole is used to couple out reflection light for detection, then the ability to automatically set evanescent illumination is improved, but the device complexity increases
Solution Approach 1:
The system uses a detection device to detect the reflection light intensity and feeds this information back to automatically adjust the illumination settings. The control unit processes the detected signal and adjusts the light source or optical components to achieve the desired evanescent field penetration depth, creating a closed-loop feedback system that enables automatic setting.
Solution Approach 2:
The mirror with a hole acts as an intermediary element that selectively couples out the reflection light from the main illumination beam path while allowing the evanescent illumination to continue. This intermediary component enables the detection function without significantly disrupting the primary illumination function, resolving the contradiction by adding a dedicated mediation element.
2Stability of the object's composition
If the beam is directed rotation-symmetrically for evanescent illumination, then the illumination uniformity is improved, but the ability to determine penetration depth is worsened due to unknown refractive indices
Solution Approach 1:
The system replaces direct mechanical measurement of penetration depth with an optical measurement approach. By detecting the reflection light intensity and using the relationship between reflection intensity, angle of incidence, and refractive index, the system calculates penetration depth optically rather than through direct physical measurement, enabling precise determination even with rotation-symmetrical beam direction.
Solution Approach 2:
The system changes the measurement parameter from direct penetration depth measurement to reflection light intensity detection. By monitoring how the reflection light intensity varies with the angle of incidence and comparing it to theoretical models, the system indirectly determines the penetration depth and refractive index, maintaining illumination uniformity while enabling precise measurement.
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 precise and automatic setting of evanescent illumination, allowing for reproducible and targeted penetration depth control of the evanescent field, even with specimens of unknown refractive indices, by calculating the angle of total reflection and refractive index.
Implementation Method 1
the refractive behavior of light as it makes the transition from an optically denser medium to an optically thinner medium is utilized. Thus, for example, the transition from cover glass (n1=1.518) to water (n2=1.33) yields a critical angle of 61°, the angle of total reflection. Under the conditions of total reflection (angle ≧61°), a standing evanescent wave is formed in the medium with the lower refractive index.
Implementation Method 2
a standing evanescent wave is formed in the medium with the lower refractive index. The intensity of this wave drops exponentially relative to the distance from the interface.
Implementation Method 3
both the illumination light and the detection light are directed via the illuminating beam path through the objective, and whereby, for example, totally reflected illumination light (reflection light) at the interface to a specimen or specimen cover returns to the illuminating beam path.
Data Source
AI summary
A microscope for total internal reflection microscopy. The microscope includes at least one light source configured to provide an illumination light to an illumination beam path for an evanescent illumination of a specimen so as to reflect the illumination light at an interface to the specimen or a specimen cover so as to return reflection light into the illumination beam path, an objective through which the illumination light and detection light are directable, a detection device, and a coupling device. The coupling device includes a mirror disposed in the illumination beam path. The mirror has a reflecting surface and a hole, the hole being configured to pass the illumination light there through so as to couple the illumination light into the illumination beam path. The reflecting surface is configured to couple out at least a part of the reflection light and to direct the coupled-out reflection light to the detection devices so as to enable determination from a beam path of the coupled-out reflection light, at least one of a quantifiable parameter and a qualifiable parameter of at least one of the evanescent illumination and an evanescent field created in the specimen.