High Dynamic Range Image Sensor Attenuation Layer Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High dynamic range (HDR) image sensors with big-small pixel schemes face issues of increased cross talk and non-uniform angular response due to thick attenuation layers, which degrade optical performance.
Innovation Solution
Implementing a thin attenuation layer with materials like TiN, Al2O3, AlCu, Cu, Ti, Ta, Ag, W, TiO2, ZrO2, TaO, SiO2, SiN, SiNO, or HfOx, with a thickness in the order of nanometers, and a coating layer with a lower refractive index to reduce cross talk and improve angular performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a thick attenuation layer is used to improve small pixel performance, then light blocking capability is improved, but cross talk between adjacent pixels increases and angular response uniformity deteriorates
Solution Approach 1:
The patent divides the attenuation structure into multiple segments: a thin attenuation layer (first thickness) and an extended isolation structure (second thickness greater than first thickness). This segmentation allows the thin layer to provide sufficient light blocking for small pixels while the extended isolation structure specifically targets cross-talk reduction between adjacent pixels without compromising angular response uniformity.
Solution Approach 2:
The patent applies different attenuation characteristics to different regions: the thin attenuation layer provides uniform light blocking across the pixel array, while the extended isolation structure is specifically positioned between adjacent pixels to provide localized cross-talk reduction. This local differentiation resolves the contradiction by addressing each issue with a tailored solution.
2Object-affected harmful factors
If a thick attenuation layer is used to improve small pixel performance, then light blocking capability is improved, but angular response uniformity deteriorates
Solution Approach 1:
The patent segments the attenuation function into a thin uniform attenuation layer and an extended isolation structure. The thin layer maintains uniform angular response across all pixels, while the extended isolation structure is configured to not interfere with the angular response characteristics, thus preserving uniformity while providing sufficient light blocking.
Solution Approach 2:
The patent changes the thickness parameter from a single thick layer to a dual-layer configuration with different thicknesses (first thickness for attenuation, second thickness greater than first for isolation). This parameter differentiation allows the system to achieve adequate light blocking without the angular response degradation caused by uniformly thick layers.
3Object-generated harmful factors
If a thin attenuation layer is used to reduce cross talk and improve angular response, then cross talk is reduced and angular response uniformity is improved, but light blocking capability may be insufficient
Solution Approach 1:
The patent segments the attenuation function into two parts: the thin attenuation layer (first thickness) provides cross-talk reduction and maintains angular response uniformity, while the extended isolation structure (second thickness greater than first thickness) compensates for light blocking capability. This segmentation allows each component to optimize for its specific function.
Solution Approach 2:
The extended isolation structure serves multiple functions: it provides additional light blocking to compensate for the reduced thickness, maintains cross-talk isolation between adjacent pixels, and preserves angular response uniformity. This multi-functionality resolves the contradiction by making the isolation structure responsible for both attenuation and isolation.
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 optical cross talk between adjacent pixels and enhances uniformity in angular performance, thereby improving the overall optical performance of HDR cameras.
Implementation Method 1
an extra attenuation layer is usually disposed over the small pixels to block a portion of the light from reaching the small pixels
Implementation Method 2
a coating layer with a lower refractive index to reduce cross talk and improve angular performance
Data Source
AI summary
An image sensor comprises a first photodiode and a second photodiode having a smaller full-well capacitance than the first photodiode, wherein the second photodiode is adjacent to the first photodiode; a first micro-lens is disposed above the first photodiode and on an illuminated side of the image sensor; a second micro-lens is disposed above the second photodiode and on the illuminated side of the image sensor; and a coating layer disposed on both the first and second micro-lens, wherein the coating layer forms a flat top surface on the second micro-lens and a conformal coating layer on the first micro-lens.