Diffractive Microlens Array for Light Concentration
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Solution Overview
Problem
Conventional microlens designs for digital imaging and solar cells are inefficient at concentrating light onto small detector elements due to classical optics principles that fail at micron scales, leading to suboptimal light focusing and increased cross-talk, as they do not account for diffraction effects and chromatic dependence.
Innovation Solution
The development of diffractive optical elements, such as rectangular prisms and cylindrical disks, that are engineered to concentrate light efficiently onto light-sensitive detector elements, minimizing cross-talk by optimizing the longitudinal position and shape of the microlenses, which are fabricated using standard microfabrication techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional spherical microlens designs are used, then light concentration is achieved according to classical optics, but light focusing efficiency deteriorates at micron scales due to diffraction effects
Solution Approach 1:
The patent changes the fundamental parameter of lens geometry from spherical to diffractive structures (such as Fresnel zones, concentric rings, or binary optics patterns). This parameter change allows the optical system to operate according to diffraction physics rather than classical ray optics, achieving accurate focusing at micron scales where traditional spherical lenses fail.
Solution Approach 2:
The patent replaces the mechanical/optical system based on continuous refraction (spherical lenses) with a diffractive optical system using discrete phase modulation structures. This substitution enables precise light concentration by controlling wavefront phase through diffractive patterns, achieving superior focusing at small dimensions where classical optics breaks down.
2Area of stationary object
If spherical microlens designs are used, then light collection area is maximized, but cross-talk between adjacent detector elements increases
Solution Approach 1:
The patent applies local quality by designing diffractive microlens patterns with specific phase distributions that concentrate light precisely onto individual detector elements. The diffractive structures create localized intensity maxima at detector positions while maintaining minimal intensity in adjacent regions, thus reducing cross-talk while preserving light collection area.
Solution Approach 2:
The patent converts the harmful diffraction effects that cause cross-talk in traditional lenses into a beneficial mechanism. By deliberately designing diffractive optical elements with controlled phase patterns, the patent uses diffraction to create sharp focal spots and minimize lateral light spread, thereby reducing cross-talk between adjacent detectors.
3Ease of manufacture
If conventional plano-convex microlenses are used, then manufacturing is simplified, but light focusing performance deteriorates at small dimensions
Solution Approach 1:
The patent segments the continuous spherical lens profile into discrete diffractive zones or step-like structures. These segmented diffractive patterns can be manufactured using standard photolithography and etching processes, maintaining fabrication simplicity while achieving superior light concentration through controlled diffraction from the segmented structures.
Solution Approach 2:
The patent uses photolithographic copying to transfer diffractive patterns onto the microlens substrate. This copying process replicates the precise diffractive zone patterns across large arrays of microlenses, maintaining both manufacturing ease through standard semiconductor fabrication and superior optical performance at micron scales.
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
These designs achieve higher light power density and reduced cross-talk, concentrating light up to 12 times the incident intensity at shallower depths compared to traditional spherical microlenses, enhancing the performance of digital imaging and solar cell technologies.
Implementation Method 1
At this small size, the physics of light propagation is dominated by diffraction. The development of diffractive optical elements, such as rectangular prisms and cylindrical disks, that focus light efficiently onto light-sensitive detector elements by accommodating diffraction effects
Implementation Method 2
where the index of refraction of the transparent material is n (>1)... incident light from a faraway bright object is focused inside the thickness of the lens material
Data Source
AI summary
A novel micron-scale lens, a microlens, is engineered to concentrate light efficiently onto an area of interest, such as a small, light-sensitive detector element in an integrated electronic device. Existing microlens designs imitate the form of large-scale lenses and are less effective at small sizes. The microlenses described herein have been designed to accommodate diffraction effects, which dominate the behavior of light at small length scales. Thus a new class of light-concentrating optical elements with much higher relative performance has been created. Furthermore, the new designs are much easier to fabricate than previous designs.