2x2 Sub-pixel Array with 1x2 On-Chip Lenses for PDAF
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Solution Overview
Problem
Current image capture devices with phase detection auto-focus (PDAF) pixels face limitations in PDAF performance, particularly in low light conditions and images with few vertical edges, due to the limited density of metal shield or adjacent microlens configurations, which degrades auto-focus performance and increases signal correction burdens.
Innovation Solution
The implementation of an image capture device with a 2×2 array of sub-pixels under a pair of adjacent 1×2 on-chip lenses (OCLs), allowing for improved light distribution and signal-to-noise ratio, and enabling focus detection on both vertical and horizontal edges, thereby enhancing PDAF performance and reducing the need for signal correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal shield or adjacent microlens configurations are used for PDAF pixels, then phase detection auto-focus capability is enabled, but PDAF performance degrades in low light conditions and images with few vertical edges
Solution Approach 1:
Each pixel is divided into a 2×2 array of sub-pixels, with each sub-pixel having its own dedicated 1×2 on-chip lens. This segmentation allows independent optimization of light collection for each sub-pixel, improving phase detection signal strength in challenging conditions while maintaining full image capture capability across all sub-pixels.
Solution Approach 2:
The patent implements different lens configurations tailored to specific sub-pixel functions: 1×2 on-chip lenses are specifically designed for PDAF sub-pixels to optimize phase detection, while other sub-pixels maintain standard configurations for image capture. This local optimization ensures each region performs its designated function with maximum efficiency.
2Device complexity
If limited density of metal shield or adjacent microlens configurations is used, then device complexity is reduced, but signal-to-noise ratio decreases and manufacturing variance corrections become more difficult
Solution Approach 1:
The patent merges the PDAF detection function with the standard pixel structure by integrating 1×2 on-chip lenses directly into the pixel array. This integration allows PDAF functionality to be achieved without adding separate detection hardware, maintaining device simplicity while improving focus detection precision through optimized light distribution across the 2×2 sub-pixel array.
Solution Approach 2:
The patent changes the lens configuration parameter from traditional metal shield or adjacent microlens designs to 1×2 on-chip lenses positioned over specific sub-pixel pairs. This parameter change optimizes the light collection geometry, improving the phase detection signal-to-noise ratio and reducing sensitivity to manufacturing variances while maintaining a relatively simple device structure.
3Measurement precision
If 2×2 array of sub-pixels with 1×2 on-chip lenses is implemented, then light distribution and signal-to-noise ratio are improved, but device structure becomes more complex
Solution Approach 1:
The 2×2 sub-pixel array with 1×2 on-chip lenses serves multiple functions simultaneously: image capture through all sub-pixels and phase detection through the configured lens-sub-pixel pairs. This multi-functionality eliminates the need for separate PDAF pixel regions, achieving improved focus detection accuracy without proportionally increasing overall device complexity.
Solution Approach 2:
The patent implements a nested structure where 1×2 on-chip lenses are positioned directly over pairs of sub-pixels within each pixel unit. This nesting allows the PDAF optical components to be integrated within the existing pixel footprint, improving focus detection capability while minimizing the increase in overall device structure complexity.
4Ease of manufacture
If traditional PDAF pixel configurations are used, then manufacturing is simpler, but re-mosaicing challenges increase and image quality deteriorates
Solution Approach 1:
The patent performs preliminary organization of sub-pixels into 2×2 arrays with dedicated 1×2 on-chip lenses during the manufacturing process. This preliminary structuring of PDAF-capable sub-pixels within each pixel unit simplifies subsequent re-mosaicing operations by pre-establishing the correct spatial relationships and optical alignments, thereby improving manufacturing precision and reducing post-processing complexity.
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 simplifies corrections for manufacturing variances, improves focus accuracy, reduces re-mosaicing challenges, and enhances image quality by allowing more light into each sub-pixel, leading to better PDAF performance and image resolution, especially in low light conditions.
Implementation Method 1
Each pixel may include a 2×2 array of photodetectors. For each pixel in the array of pixels, a respective pair of adjacent 1×2 on-chip lenses (OCLs) may be disposed over a pixel.
Data Source
AI summary
An image capture device is described. The image capture device includes an array of pixels. Each pixel includes a 2×2 array of photodetectors. The image capture device also includes an array of 1×2 on chip lenses (OCLs) disposed over the array of pixels. For each pixel in the array of pixels, a respective pair of adjacent 1×2 OCLs is disposed over a pixel, with each respective pair of adjacent 1×2 OCLs including a respective first 1×2 OCL disposed over a first photodetector and a respective second photodetector in the 2×2 array of photodetectors for the pixel, and a second 1×2 OCL disposed over a third photodetector and a fourth photodetector in the 2×2 array of photodetectors for the pixel.