Antireflective Microlens Array for High-NA Optical Lenses
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Solution Overview
Problem
High-NA optical lenses face challenges in achieving uniform light transmittance and reducing beam spot diameter due to high curvature and thickness errors in antireflective coatings, leading to low overall transmittance and non-uniform light distribution.
Innovation Solution
An optical lens with a convex surface and an antireflective structure featuring structural elements arranged in an array with a pitch smaller than the shortest wavelength of incident light, providing a maximum inclination angle of 35 to 90 degrees, which suppresses light reflection and improves transmittance by forming a continuous apparent refractive index change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an antireflective coating is applied to high-NA optical lenses, then light reflection is reduced, but the coating thickness becomes non-uniform due to high surface curvature, leading to large thickness errors and poor transmittance
Solution Approach 1:
The patent segments the continuous antireflective coating into discrete microlens elements arranged in an array. Each microlens element is a separate structural unit with controlled dimensions, eliminating the thickness uniformity problems associated with continuous coatings on high-curvature surfaces. The segmentation allows each element to be independently formed with precise dimensional control.
Solution Approach 2:
The patent implements local quality by creating microlens elements with specific dimensional characteristics (diameter 0.1-10 μm, height 0.1-10 μm) that are optimized for antireflective performance. Each microlens element has a predetermined shape and size that provides the desired optical function, with the array pitch controlled to be less than the wavelength of incident light. This local structuring ensures consistent optical properties across the lens surface despite the high curvature.
2Length of moving object
If the numerical aperture (NA) of the optical lens is increased to reduce beam spot diameter, then beam spot size is reduced, but light transmittance in the peripheral area decreases due to large incident angles and high curvature
Solution Approach 1:
The microlens array is specifically designed for the peripheral areas of the optical lens where incident angles are large and curvature is high. Each microlens element is positioned and dimensioned to handle the local optical conditions, providing effective antireflective performance tailored to the specific incident angle and curvature at each location. This local optimization ensures uniform light transmission across the entire lens surface.
Solution Approach 2:
The patent changes the optical parameters by introducing a periodic microlens structure with pitch less than the wavelength of incident light. This parameter change creates an effective medium that modifies the refractive index profile, enabling effective antireflection even at large incident angles. The dimensional parameters of the microlens elements (diameter, height, pitch) are specifically controlled to achieve the desired optical effect.
3Ease of manufacture
If conventional antireflective coating methods are used on high-NA lenses, then coating application is simplified, but the thickness error from design thickness increases, making it difficult to achieve uniform light quantity distribution
Solution Approach 1:
The continuous coating process is replaced by a segmented microlens array structure that can be formed using standard injection molding techniques. This segmentation approach maintains manufacturing simplicity while achieving precise dimensional control of each microlens element, with the array pitch and element dimensions controlled to be less than the wavelength of incident light.
Solution Approach 2:
The patent replaces the mechanical coating process (which suffers from thickness control issues on high-curvature surfaces) with a molded structural solution. The microlens array is formed directly into the lens substrate through injection molding, eliminating the need for separate coating processes and the associated thickness uniformity problems. This substitution of the mechanical coating system with a structural integration approach resolves the manufacturing precision issue.
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 light reflection and enhances transmittance across the lens surface, particularly in high-NA optical lenses, ensuring uniform light distribution and improved beam spot formation, suitable for optical pickup devices and other optical systems.
Implementation Method 1
an antireflective structure provided on the lens surface and including structural elements that have a predetermined shape and are arranged in an array form with a pitch smaller than a shortest wavelength of incident light
Implementation Method 2
providing a maximum inclination angle of 35 to 90 degrees, which suppresses light reflection and improves transmittance by forming a continuous apparent refractive index change
Data Source
AI summary
An optical lens in which reflection is suppressed is provided by providing the optical lens with: a convex lens surface having, when the angle between a plane in contact with the lens surface and a direction perpendicular to the optical axis is an inclination angle, a maximum inclination angle of not less than 35 degrees and less than 90 degrees; and an antireflective structure provided on the lens surface and including structural elements that have a predetermined shape and are periodically arranged in an array form with a pitch smaller than the shortest wavelength of the incident light.