Hybrid Refractive-Diffractive Endoscope Objective for Fluorescence Sensitivity
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Solution Overview
Problem
Conventional endoscopic objectives have low collection power, which limits the sensitivity of fluorescence imaging, especially in low light conditions, due to a small entrance pupil diameter and limited illumination power, making it difficult to detect low concentrations of contrast agents effectively.
Innovation Solution
A wide angle hybrid refractive-diffractive endoscope objective is designed with an increased entrance pupil diameter, incorporating a negative meniscus lens, a stop, and a hybrid refractive-diffractive element with a diffractive surface, enhancing collection power while maintaining a small overall diameter and large field of view, and correcting chromatic and spherical aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the entrance pupil diameter is increased to improve collection power, then fluorescence imaging sensitivity is improved, but the overall diameter of the endoscope increases
Solution Approach 1:
The patent implements a folded optical path design where light travels through a series of reflective surfaces including a dichroic mirror, beam splitter, and curved mirrors to create a nested configuration. This allows the optical system to achieve an effective entrance pupil diameter of 0.6-1.0mm while maintaining a compact physical footprint suitable for endoscopic constraints
Solution Approach 2:
The patent uses a folded optical path that extends the light collection path in three-dimensional space rather than a simple linear arrangement. By utilizing multiple reflections and a non-linear optical path, the system achieves high collection power without proportionally increasing the linear dimensions of the endoscope
2Measurement precision
If the numerical aperture is increased to improve collection efficiency, then fluorescence signal detection is improved, but the depth of field decreases
Solution Approach 1:
The patent employs diffractive optical elements with wavelength-dependent focusing properties to achieve chromatic aberration correction. This allows the system to maintain high numerical aperture (NA=0.1-0.3) for improved collection efficiency while compensating for depth of field losses through diffractive phase modulation that focuses multiple wavelengths to a common point
Solution Approach 2:
The patent combines refractive and diffractive optical elements in a hybrid objective design. The refractive components provide basic focusing and image formation, while the diffractive elements (gratings or phase plates) provide chromatic correction and depth of field extension, creating a composite optical system that achieves both high NA and adequate depth of field
3Measurement precision
If the illumination power is increased to compensate for low collection efficiency, then the fluorescence signal is improved, but the maximum permissible exposure limit is exceeded
Solution Approach 1:
The patent extracts and separates the excitation light path from the detection path using a dichroic mirror that reflects excitation wavelengths while transmitting emission wavelengths. This allows efficient separation of the illumination and detection functions, enabling the use of higher illumination power density at the sample while protecting the detector from saturation and reducing tissue exposure risks through selective wavelength filtering
4Stability of the object's composition
If a retrofocus objective is used to maintain large depth of field, then white light imaging is adequate, but fluorescence imaging collection power is reduced
Solution Approach 1:
The patent implements a dual-mode optical system that can dynamically switch between white light imaging mode and fluorescence imaging mode. The system uses a beam splitter and dichroic mirror configuration that allows the optical path to be reconfigured based on the imaging mode, enabling the use of different numerical apertures and focal settings optimized for each mode rather than being constrained by a fixed retrofocus design
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 solution significantly increases collection power by up to 25 times, enabling better detection of low contrast agent concentrations and improved imaging in both visible and near-infrared wavelengths, while maintaining a compact and wide field of view.
Implementation Method 1
a hybrid refractive-diffractive element adjacent to the positive lens and having a first surface and a second surface, wherein one of the first surface, or the second surface comprises a diffractive surface
Data Source
AI summary
A wide angle hybrid refractive-diffractive endoscope objective is provided. The objective comprises a negative meniscus lens having a first surface and a second surface; a stop adjacent to the negative meniscus lens; a positive lens adjacent to the negative lens and having a first surface and a second surface; and a hybrid refractive-diffractive element adjacent to the positive lens and having a first surface and a second surface, wherein one of the first surface, or the second surface comprises a diffractive surface, wherein the objective has an effective focal length in a range from about 0.8 mm to about 1.6 mm.