Tilted Multimode Fiber Bundle for Spectrometer Vignetting
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Solution Overview
Problem
Spectrally encoded endoscopy probes face issues with nonuniform far field patterns at the spectrometer input, leading to poor image quality and reduced coupling efficiency for large view angles due to vignetting, as high-angle incident light is not effectively detected by the multi-mode optical fibers.
Innovation Solution
The optical fibers are tilted or angle-polished at the spectrometer entrance to shift the far field pattern relative to the spectrometer's optical axis, optimizing throughput for large view angles while maintaining detection efficiency for small view angles, thereby reducing nonuniformity and vignetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If high numerical aperture multi-mode optical fibers are used to detect large view angles, then the field of view is increased, but nonuniformity and vignetting occur at the spectrometer input
Solution Approach 1:
The optical fiber bundle is tilted at an angle of 5-15 degrees relative to the spectrometer optical axis, creating an asymmetric configuration. This asymmetry shifts the far field pattern to be nonparallel to the optical axis, which compensates for the vignetting effect and normalizes the signal levels across different view angles, thereby resolving the nonuniformity problem while maintaining the large field of view capability
2Area of moving object
If detection optical fibers are angle-polished to increase field of view, then large view angles are detected, but nonuniform far field pattern and ghost images are generated
Solution Approach 1:
The angle of the optical fiber bundle relative to the spectrometer optical axis is optimized to a specific range of 5-15 degrees. This parameter change shifts the far field pattern appropriately, which increases the field of view while simultaneously minimizing the formation of ghost images by controlling the angular distribution of light reaching the spectrometer sensor
3Productivity
If optical fibers are tilted to shift far field pattern, then throughput for large view angles is increased, but alignment complexity increases
Solution Approach 1:
The optical fiber bundle is pre-oriented at a specific angle (5-15 degrees) relative to the spectrometer optical axis during assembly. This preliminary action ensures that the far field pattern is correctly positioned before operation, maximizing optical throughput for large view angles while simplifying the alignment process during system setup, as the correct angle is built into the structure rather than requiring complex real-time adjustment
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 enhances image quality by normalizing signal levels across the field of view, increasing optical throughput for large view angles, and reducing ghost images, while maintaining focus and alignment with the sensor plane.
Implementation Method 1
a bundle of multi-mode optical fibers that transmits light received from an imaging target to a spectrometer
Implementation Method 2
A far field pattern of light transmitted through a fundamental mode of at least one of the multi-mode optical fibers is nonparallel to an optical axis of the spectrometer for reducing nonuniformity of the far field pattern at an input sensor of the spectrometer
Data Source
AI summary
A spectrally encoded endoscopy optical device includes a bundle of multi-mode optical fibers that transmits light received from an imaging target to a spectrometer. A far field pattern of light transmitted through a fundamental mode of at least one of the multi-mode optical fibers is nonparallel to an optical axis of the spectrometer for reducing nonuniformity of the far field pattern at an input sensor of the spectrometer. For still further reduction of such nonuniformity, a far field pattern of light transmitted through a fundamental mode of the bundle of multi-mode optical fibers is nonparallel to an optical axis of the spectrometer.