Dual Microlens AF Pixel for Phase Detection Accuracy
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Solution Overview
Problem
Existing image sensors with phase detection auto focus (PDAF) pixels face challenges in small light receiving areas due to light loss and crosstalk caused by metal shields, which deteriorate phase signal accuracy, especially in high-resolution camera modules.
Innovation Solution
The image sensor incorporates AF pixels with a color filter layer and dual microlenses of varying heights, widths, and curvatures, arranged in a specific configuration to optimize light reception based on incident angles, reducing optical loss and crosstalk through a grid structure and dielectric layer for improved phase detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal shield is used to block light in PDAF pixels, then phase detection function is achieved, but light loss and crosstalk occur deteriorating pixel performance
Solution Approach 1:
The patent removes the metal shield structure from the PDAF pixel design. Instead of using a metal shield to block light for phase detection, the invention extracts this function by using a different mechanism - specifically, by utilizing the natural light blocking properties of the pixel structure itself or alternative materials that do not cause crosstalk or significant light loss, thereby eliminating the harmful effects while maintaining the phase detection capability
Solution Approach 2:
The patent introduces an intermediary structure or material to replace the metal shield. This intermediary element performs the light blocking function necessary for phase detection but is designed to minimize crosstalk and light loss. The intermediary could be a specifically designed dielectric structure or a modified pixel configuration that achieves the same functional goal without the adverse effects of metal shields
2Measurement precision
If pixel size is reduced for high-resolution camera modules, then resolution is improved, but light receiving area decreases causing more light loss
Solution Approach 1:
The patent changes the parameters of the pixel structure, specifically the size, shape, or configuration of light-receiving regions and internal structures. By optimizing these parameters, the design achieves high resolution with smaller pixels while compensating for reduced light gathering area through improved light utilization efficiency, such as enhanced microlens design or optimized photodiode geometry
Solution Approach 2:
The patent employs composite material structures in the pixel design, combining multiple materials with different optical properties to maximize light reception in small pixels. This could include composite photodiode structures, multi-layer dielectric materials, or hybrid material configurations that improve light sensitivity and efficiency in compact high-resolution pixel designs
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
This configuration enhances the reliability of phase detection and increases the auto-focus success rate, even in high-resolution camera modules with small light receiving areas by minimizing optical loss and crosstalk.
Implementation Method 1
first and second microlenses arranged over the color filter layer, and formed in a region of the at least one AF pixel in a widthwise direction of the color filter layer
Implementation Method 2
a color filter layer
Implementation Method 3
an image sensor converts incident light into an electrical signal
Data Source
AI summary
An image sensor includes a pixel array in which auto-focus (AF) pixels and image capture pixels are arranged. Wherein at least one of the AF pixels comprises: a color filter layer; and first and second microlenses arranged over the color filter layer, and formed in a region of the at least one AF pixel in a widthwise direction of the color filter layer.