Shared-Pixel Micro-Lens Layout for Stronger AF Signal Sensitivity
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Solution Overview
Problem
Current image sensors face challenges in enhancing auto focusing (AF) characteristics, particularly in accurately capturing images due to limitations in the design of micro-lenses and photodiode arrangements, which affect light transmission and signal sensitivity.
Innovation Solution
The proposed solution involves a micro-lens structure where the highest points of micro-lenses are disposed closer to the center of a shared pixel, with a color filter positioned between the micro-lenses and subpixels, optimizing light transmission and signal sensitivity by ensuring that light is focused on the appropriate photodiodes, thereby improving AF characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If micro-lenses are disposed at upper portions of subpixels with highest points over photodiodes, then light transmission is improved, but auto focusing signal sensitivity and contrast deteriorate
Solution Approach 1:
The patent applies local quality by differentiating the positioning of micro-lenses based on their location within the pixel array. Specifically, micro-lenses corresponding to pixels used for auto focusing have their highest points positioned closer to the center of the pixel, while other micro-lenses follow the conventional positioning over photodiodes. This localized differentiation optimizes light transmission for imaging while enhancing auto focusing signal sensitivity and contrast for specific pixels.
2Illumination intensity
If micro-lenses are disposed at upper portions of subpixels with highest points over photodiodes, then light transmission is improved, but image capture accuracy deteriorates
Solution Approach 1:
The patent implements local quality by applying different micro-lens positioning strategies to different functional regions of the pixel array. Imaging pixels use conventional photodiode-aligned positioning for optimal light transmission, while auto focusing pixels use center-aligned positioning to improve focus detection accuracy. This localized approach ensures both light transmission and image capture accuracy are optimized for their respective functions.
3Measurement precision
If highest points of micro-lenses are disposed closer to center of shared pixel, then auto focusing signal sensitivity is improved, but light transmission to subpixels deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the pixel array into distinct functional groups: imaging pixels and auto focusing pixels. Each group has its micro-lenses positioned according to its specific functional requirements. This segmentation allows the system to optimize light transmission for imaging pixels while simultaneously optimizing auto focusing signal sensitivity for dedicated auto focusing pixels, without compromising either function.
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 sensitivity and contrast of auto focusing signals, leading to improved image capture and processing efficiency, particularly in applications requiring precise focus detection.
Implementation Method 1
Each of the plurality of subpixels includes two or more photodiodes. Highest points of each of the plurality of micro-lenses from an upper surface of the color filter are respectively disposed over one of the two or more photodiodes of the plurality of subpixels that are closer to a center of the shared pixel
Data Source
AI summary
An image sensor includes a shared pixel including a plurality of subpixels and a plurality of micro-lenses respectively disposed at upper portions of the plurality of subpixels. The shared pixel shares one color pattern, and a highest point of each of the plurality of micro-lenses is close to a center of the shared pixel.