PDAF Pixel Deflection Element Layout for Small-Pixel Autofocus
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Solution Overview
Problem
As pixel sizes shrink in imaging devices, the sensing sensitivity drops, leading to challenges in accurately determining phase differences for autofocus and requiring different light compensation for improved sensing quality.
Innovation Solution
An imaging device design featuring a substrate with an array of pixels, including PDAF pixels with four photoelectric conversion elements and a deflection element with a higher refractive index than the color filter layer, which redirects light to improve sensitivity and mismatch correction between PDAF and sensing pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to improve resolution, then resolution is improved, but sensing sensitivity drops
Solution Approach 1:
The patent introduces a deflection element with specific refractive index properties localized at the PDAF pixel level to compensate for the reduced sensing area. This local optical modification allows each PDAF pixel to receive adequate light intensity despite the overall pixel size reduction, thereby maintaining sensing sensitivity while achieving higher resolution through smaller pixels.
Solution Approach 2:
The deflection element acts as an intermediary optical component that redirects incoming light to the photoelectric conversion elements in PDAF pixels. This intermediary structure compensates for the reduced light-capturing area caused by smaller pixel sizes, ensuring sufficient light intensity reaches the sensing elements to maintain measurement reliability.
2Reliability
If PDAF pixels use different light compensation than regular sensing pixels, then sensing quality is improved, but device complexity increases
Solution Approach 1:
The deflection element is selectively positioned only in PDAF pixels rather than uniformly across all pixels, providing localized optical compensation where needed. This approach improves sensing quality for phase detection while avoiding the complexity of modifying the entire pixel array structure.
Solution Approach 2:
The patent modifies the refractive index parameter by introducing the deflection element with a higher refractive index than the color filter layer. This parameter change enables effective light redirection and compensation in PDAF pixels, improving sensing quality through optical property modification rather than complex structural changes.
3Reliability
If deflection element with higher refractive index is used to correct light angle, then sensing sensitivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a refractive index range (1.5 to 2.0) for the deflection element material, providing a practical parameter window that balances optical effectiveness with manufacturing feasibility. This parameter specification enables manufacturers to select materials that provide sufficient light redirection while remaining achievable with current fabrication capabilities.
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
Enhances sensitivity and quality of autofocusing by correcting light angle mismatches, improving sensing intensity and avoiding shading and color mismatch.
Implementation Method 1
a deflection element inside the color filter layer and partially over the isolation region of the substrate, in which a refractive index of the deflection element is larger than a refractive index of the color filter layer
Data Source
AI summary
The present disclosure provides an imaging device. The imaging device includes a substrate and an array of pixels. The substrate has an isolation region. The array of pixels includes a plurality of sensing pixels and a plurality of phase detection auto focus (PDAF) pixels, in which each of the PDAF pixels includes four photoelectric conversion elements, a color filter layer, and a deflection element. The four photoelectric conversion elements are in the substrate and separated by the isolation region of the substrate. The color filter layer is on the four photoelectric conversion elements. The deflection element is inside the color filter layer and partially over the isolation region of the substrate, in which a refractive index of the deflection element is larger than a refractive index of the color filter layer.