Oblique Illumination Microscope Using Multi-Mode Fiber
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Solution Overview
Problem
Single-mode optical fibers in TIR microscopy are difficult to align, suffer from wavelength and power limitations, and produce non-uniform, interference-prone illumination profiles, degrading image quality.
Innovation Solution
A microscope system utilizing a multi-mode optical fiber with a homogenized laser beam, where the fiber's egress is conjugate to the sample plane and laterally displaced from the objective lens's principal axis, providing oblique illumination and facilitating total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-mode optical fibre is used to deliver laser light through a high numerical aperture objective lens at an oblique angle, then TIR microscopy can be achieved, but the system suffers from difficult alignment, wavelength and power limitations, and non-uniform Gaussian illumination profiles that produce interference fringes
Solution Approach 1:
The patent changes the fiber mode parameter from single-mode to multi-mode operation. This allows the system to maintain TIR microscopy capability while eliminating the alignment difficulties and interference fringe problems associated with single-mode fibers. The multi-mode fiber's larger core diameter and different light propagation characteristics fundamentally alter the illumination properties.
Solution Approach 2:
The patent uses a beam scanning approach that sequentially illuminates different regions of the sample plane. By copying the illumination pattern across multiple positions and times, the system achieves uniform overall illumination while using a multi-mode fiber source, effectively replacing the problematic single-mode fiber's direct illumination approach.
2Reliability
If a single-mode optical fibre is used as the light source, then TIRF illumination can be provided, but the illumination profile is non-uniform (Gaussian) and coherent, leading to interference fringes that degrade image quality
Solution Approach 1:
The patent changes the coherence parameter of the light source by using multi-mode fiber instead of single-mode fiber. This parameter change transforms the highly coherent Gaussian beam into a less coherent, more uniform illumination profile, thereby eliminating the interference fringes that degrade image quality while preserving TIRF illumination capability.
Solution Approach 2:
The patent converts the potentially harmful coherent Gaussian profile into a beneficial uniform illumination pattern. By using multi-mode fiber, the system transforms what would be a problematic coherent source into an ideal incoherent-like source for TIRF microscopy, where the lack of coherence eliminates interference artifacts.
3Illumination intensity
If a single-mode optical fibre is used for laser delivery, then oblique illumination can be achieved, but the system has wavelength and power limitations
Solution Approach 1:
The patent changes the fiber's light-guiding parameters by switching from single-mode to multi-mode operation. This allows the system to accept a broader range of wavelengths and higher power levels, as multi-mode fibers have larger core diameters and different numerical aperture characteristics that are less restrictive regarding source compatibility.
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 system offers easier alignment, wider wavelength compatibility, higher laser power delivery, and interference-free, uniform illumination, enhancing image quality and enabling applications like super-resolution imaging.
Implementation Method 1
the objective lens delivers said light beam to the sample plane at an angle that is oblique to the principal optical axis... configured such that said light beam is incident at said objective lens laterally displaced from the principal optical axis
Data Source
Figure 1~2B
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AI summary
A microscope system has an illumination optical system comprising a multi-mode optical fibre having an egress for emitting a laser beam. The egress is located in a plane that is conjugate to the microscope sample plane. The illumination optical system is configured such that the laser beam is incident at the objective lens laterally displaced from the principal optical axis of the objective lens in order that the objective lens delivers the laser beam to the sample plane at an angle that is oblique to the principal optical axis. Utilization of a multi-mode optical fibre for laser delivery in oblique illumination microscopy, such as TIRF microscopy, solves problems associated with using single-mode optical fibres such as alignment and uniformity of illumination.