Flare-Suppressing Image Sensor Refractive Element Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Camera image sensors suffer from petal flare due to the periodicity of their pixel and microlens arrays, which causes diffracted light to be reflected back and produce image artifacts.
Innovation Solution
Incorporating a refractive element with a height profile featuring multiple local maxima above each pixel, effectively creating multiple microlenses to manage light transmission and reduce petal flare, along with the use of annular lenses and opaque extensions to block diffracted illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a microlens array with periodic surface height is used above the pixel array, then light focusing capability is improved, but petal flare artifacts are generated due to diffraction and reflection
Solution Approach 1:
The microlens array is segmented into multiple sub-microlenses arranged in a specific pattern. Each sub-microlens has a smaller aperture and focuses light to a smaller spot, reducing the diffraction effects that cause petal flare while maintaining overall light gathering capability. The segmentation breaks the periodic structure that causes constructive interference at specific angles.
Solution Approach 2:
The sub-microlenses are arranged in an asymmetric pattern rather than a simple periodic grid. This asymmetric arrangement disrupts the regular diffraction pattern that produces petal flare, while still providing sufficient light focusing capability for image formation.
2Ease of manufacture
If the pixel array and microlens array both have periodic structures, then manufacturing alignment is simplified, but the image sensor acts as a diffraction grating causing flare
Solution Approach 1:
The periodic microlens array is segmented into multiple sub-microlenses with smaller individual periods. While each sub-microlens maintains manufacturability, the collective arrangement creates a more complex overall pattern that reduces diffraction grating effects. The segmentation allows standard fabrication techniques to be used while achieving the desired optical performance.
Solution Approach 2:
The sub-microlenses are arranged in a two-dimensional pattern with different spacing in orthogonal directions, breaking the one-dimensional periodicity that strongly causes diffraction. This dimensional complexity reduces the diffraction grating effect while maintaining manufacturability through standard photolithography processes.
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
Significantly reduces petal flare by effectively managing light transmission and blocking diffracted light, while maintaining comparable quantum efficiencies and spectral responses.
Implementation Method 1
The periodicity of the image sensor's pixel array and microlens array thereon result in the image sensor resembling a reflective two-dimensional diffraction grating. Part of light incident on the image sensor is diffracted toward the camera's imaging lens.
Implementation Method 2
a refractive element located above the first pixel. The refractive element has, with respect to a top surface of the substrate, a height profile having at least two one-dimensional local maxima
Data Source
AI summary
A flare-suppressing image sensor includes a first pixel formed in a substrate and a refractive element located above the first pixel. The refractive element has, with respect to a top surface of the substrate, a height profile having at least two one-dimensional local maxima in each of a first cross-sectional plane and a second cross-sectional plane perpendicular to the first cross-sectional plane. Each of the first and second cross-sectional planes is perpendicular to the top surface and intersects the first pixel.