Diffractive Lens Corrects Chromatic Aberration in OCT Capsule
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Solution Overview
Problem
Miniature OCT endoscopes face challenges in achieving ultrahigh-resolution imaging due to chromatic aberration, which degrades axial and lateral resolution, and existing solutions like multi-element achromatic lenses are costly and impractical for miniature probes.
Innovation Solution
Incorporating a diffractive lens at the distal end of the OCT capsule probe to mitigate wavelength-dependent aberration, using diffraction optics to focus different colors to a small spot and minimize distortion, thereby improving axial and lateral resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-element achromatic lenses are used to correct chromatic aberration, then axial and lateral resolution are improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces complex mechanical multi-element achromatic lenses with a diffractive optical element that uses diffraction physics to correct chromatic aberration. This substitution reduces the number of optical components while achieving the same resolution improvement, directly addressing the contradiction between measurement precision and device complexity
Solution Approach 2:
The diffractive optical element changes the optical parameters by introducing wavelength-dependent phase shifts that compensate for chromatic aberration. By manipulating the phase and amplitude characteristics of the optical wavefront, the system achieves corrected imaging without requiring complex multi-element lens assemblies
2Measurement precision
If multi-element achromatic lenses are used to correct chromatic aberration, then axial and lateral resolution are improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive multi-element achromatic lenses with a single diffractive optical element that can be manufactured using standard photolithography and deposition techniques. This substitution significantly reduces manufacturing complexity and cost while maintaining the resolution improvement
Solution Approach 2:
The diffractive optical element is designed as a simple, cost-effective component that can be mass-manufactured using semiconductor fabrication processes. This approach treats the optical correction as a disposable, low-cost element rather than a high-value precision component, directly reducing manufacturing cost
3Measurement precision
If broadband light sources are used to achieve ultrahigh-resolution imaging, then axial resolution is improved, but chromatic aberration degrades imaging quality
Solution Approach 1:
The patent converts the harmful chromatic aberration effect into a beneficial correction mechanism. The diffractive optical element is specifically designed to introduce opposite phase errors that compensate for the broadband light source's chromatic aberration, turning the harmful wavelength-dependent focusing into a useful correction tool
Solution Approach 2:
The diffractive optical element changes the optical parameters by introducing wavelength-dependent phase shifts that are specifically tailored to compensate for chromatic aberration. This parameter modification allows the system to maintain ultrahigh-resolution imaging across the entire broadband spectrum without degradation from chromatic effects
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 effectively reduces chromatic aberration, achieving a 50-fold decrease in longitudinal focal shift and providing ultrahigh-resolution imaging with improved axial and lateral resolution, making it cost-effective and practical for miniature OCT endoscopes.
Implementation Method 1
a diffractive lens positioned at a distal end of a compound lens within the OCT capsule probe
Implementation Method 2
Chromatic aberration in the OCT imaging optics will alter the backreflected spectrum from the target
Implementation Method 3
The diffractive lens can have a high diffraction efficiency over a broad spectral range
Implementation Method 4
The wavelength dependent aberration takes the form of a chromatic aberration
Data Source
AI summary
The present invention is directed to an achromatic capsule endoscope with diffractive optics. A micromotor (or a broadband rotary joint) and a custom 800 nm SD-OCT system make ultrahigh-resolution 3D volumetric imaging over a large area possible. The diffractive microlens is used directly with other miniature lens including but not limited to a GRIN lens, making the capsule endoscope design simpler and cost effective. Preliminary ex vivo 3D intraluminal imaging was performed with the distal-scanning capsule endoscope in conjunction with a home-built broadband spectral-domain OCT system, demonstrating the performance of the diffractive capsule. Considering the miniature OCT capsule imaging probe is an attractive component for using the OCT technology for esophagus imaging (or other internal organs), the proposed approach will have a broad impact on endoscopic OCT imaging by improving OCT resolution in any applications that involve a capsule OCT probe, such as gastrointestinal (GI) tract imaging, airway imaging etc.