Symmetric Polarization Filter Layout for PDAF Quantum Efficiency
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Solution Overview
Problem
Conventional polarization filters in image sensors face challenges such as increased complexity in fabrication, reduced quantum efficiency, and impaired performance due to blocking incident light in central regions, which affects phase detection auto focus (PDAF) and depth mapping.
Innovation Solution
The implementation of a symmetric polarization filter configuration with consistent linear polarizer patterns for multi-directional phase detection auto focus, which reduces fabrication complexity and enhances quantum efficiency by providing improved phase information for depth mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional asymmetric polarization filters are used, then phase detection auto focus can be implemented, but fabrication complexity increases and quantum efficiency is reduced
Solution Approach 1:
The patent applies asymmetry in reverse by using symmetric polarization filter configurations. Instead of the conventional asymmetric design with different polarizer orientations in different quadrants, this patent uses symmetric patterns where identical polarizer patterns are repeated across all quadrants. This symmetry simplifies fabrication while maintaining the phase detection capability through the consistent geometric relationship between apertures and photodiodes.
Solution Approach 2:
The polarization filter is segmented into multiple identical patterns, each comprising apertures positioned at specific locations relative to photodiodes. By dividing the filter into repeating modular units with consistent aperture-photodiode relationships, the design achieves both fabrication simplicity and functional performance for phase detection.
2Reliability
If conventional polarization filters block central regions of photodiodes, then polarizer functionality is achieved, but quantum efficiency is reduced
Solution Approach 1:
The patent applies local quality by positioning apertures at specific local regions around the photodiodes rather than blocking the central region. The apertures are strategically placed at locations that provide necessary polarization functionality while allowing maximum light transmission to the photodiode active area, thus maintaining quantum efficiency.
Solution Approach 2:
The design extracts only the essential polarization-functioning elements (apertures at specific peripheral locations) rather than using conventional designs that block central regions. This extraction approach maintains the necessary polarizer functionality while minimizing light loss and preserving quantum efficiency.
3Reliability
If conventional asymmetric polarizer patterns are used, then polarization functionality is achieved, but manufacturing precision and consistency are reduced
Solution Approach 1:
The patent uses homogeneous patterns where identical polarizer configurations are repeated across all quadrants of the filter. This homogeneity ensures that each region of the sensor receives consistent polarization treatment, improving manufacturing precision and ensuring uniform extinction ratio performance across the entire sensor array.
Solution Approach 2:
The universal pattern design allows the same aperture configuration to serve multiple functions across different quadrants, providing consistent polarization performance throughout the sensor. This multi-functional approach simplifies manufacturing while maintaining uniform polarization characteristics.
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 symmetric polarization filter configuration improves quantum efficiency, consistency of extinction ratio, and manufacturing performance, leading to enhanced phase detection auto focus and depth mapping capabilities.
Implementation Method 1
a first polarization filter (107-1) disposed between the first photodiode (105-1) and the first unshared micro-lens (117-1), the first polarization filter (107-1) including a first linear polarizer patterned to effect a polarization of light incident upon the first polarization filter (107-1)
Data Source
AI summary
Image sensors and devices for phase-detection auto focus processes are provided. A symmetric polarization filter includes a first polarizer defining a first plurality of apertures and a second polarizer adjacent with the first polarizer defining a second plurality of apertures. The first plurality of apertures can be mirror symmetrical with the second plurality of apertures about a lateral axis of the symmetric polarization filter between the first polarizer and the second polarizer. The lateral axis can be defined as an axis of symmetry of the symmetric polarization filter in plane with the first polarizer and the second polarizer.