Immersion Meta-lens for Diffraction-Limited Imaging
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Solution Overview
Problem
Current immersion objectives face challenges in miniaturization and design complexity due to the need for spherical front lenses, which require additional lenses to correct spherical aberration, increasing device volume and cost, especially when using hand-polishing techniques.
Innovation Solution
The development of liquid immersion meta-lenses using metasurfaces that reduce or eliminate spherical aberration across various design wavelengths, enabling high numerical apertures up to 1.1 and achieving diffraction-limited focal spots with Strehl ratios of approximately 0.9 at 532 nm, integrated into scanning confocal microscopes for enhanced spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hand-polishing techniques are used to manufacture the front lens, then the lens can be produced with traditional methods, but the lens design is constrained to spherical shape requiring additional lenses to correct spherical aberration
Solution Approach 1:
The patent changes the fundamental parameter of lens surface geometry from spherical to freeform aspheric surfaces. This enables single-lens design that eliminates spherical aberration without requiring multiple lenses, while still being manufacturable through advanced polishing techniques that can achieve the required surface precision.
Solution Approach 2:
The invention extracts and removes the spherical aberration correction function from separate additional lenses and integrates it into the primary lens itself through aspheric surface design. This eliminates the need for cascaded lenses while maintaining correction performance.
2Reliability
If additional lenses are cascaded to correct spherical aberration, then optical performance is improved, but device volume increases and miniaturization becomes difficult
Solution Approach 1:
The patent merges multiple lens functions (focusing and spherical aberration correction) into a single aspheric lens element. This consolidation reduces the overall device volume while maintaining the optical performance that would otherwise require multiple separate lenses.
Solution Approach 2:
By changing the lens surface parameter from spherical to aspheric, the patent achieves both aberration correction and compact design in a single element, eliminating the volume penalty associated with cascaded lens systems.
3Ease of manufacture
If spherical front lens is used, then manufacturing is simpler with traditional techniques, but design flexibility for different immersion liquids is reduced
Solution Approach 1:
The patent employs freeform aspheric surface parameters that can be precisely tailored for different immersion liquids (water, oil, etc.). These customizable surface equations allow optimization for various refractive indices while maintaining manufacturability through modern precision polishing and computer-controlled fabrication techniques.
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 meta-lenses provide a spatial resolution of about 200 nm, are adaptable for different refractive indices, and can be mass-produced using modern manufacturing techniques, overcoming the limitations of traditional lens-polishing methods while maintaining high optical performance.
Implementation Method 1
The plurality of nano-structures are arranged to define a phase profile resulting in an incident collimated circularly polarized beam to be focused to a diffraction-limited spot
Implementation Method 2
the meta-lens can provide a resolution of about half the wavelength of the incident light
Implementation Method 3
The substrate is configured to contact an immersion fluid at the second side. The plurality of nano-structures are disposed on the first side of the substrate
Data Source
AI summary
The optical imaging apparatus includes a metasurface lens including a substrate and a plurality of nano-structures patterned on a first side of the substrate. The optical imaging apparatus further includes imaging optics disposed in a spaced apart relationship with a second side of the substrate. The second side is opposite the first side on which the nano-structures are patterned. A surface of the imaging optics and the second side of the substrate define a space for accommodating an immersion fluid. The metasurface lens is configured to direct light incident on the plurality of nano-structures towards the imaging optics through the space accommodating the immersion fluid.