Image Sensor Pixel Array With Variable Microlenses for Sensitivity Uniformity
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Solution Overview
Problem
CMOS image sensors face increased deviations in sensing sensitivity due to crosstalk between pixels as pixel sizes decrease, affecting image quality.
Innovation Solution
A pixel array with microlenses of varying sizes is used to focus incident light on photoelectric conversion elements, with each microlens size adjusted based on the specific sensitivity of adjacent unit pixels to compensate for sensitivity deviations, and a method for manufacturing this array by measuring sensing sensitivities and determining corresponding microlens sizes is implemented.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is decreased to achieve high-resolution images, then image resolution is improved, but sensing sensitivity deviation increases due to crosstalk
Solution Approach 1:
The patent applies local quality by assigning different microlens sizes to different pixel groups based on their specific sensitivity characteristics. Each pixel group receives a customized microlens size that compensates for its individual sensitivity deviation, rather than using a uniform microlens size across all pixels. This localized optimization resolves the contradiction by maintaining high resolution through small pixel size while correcting sensitivity deviations through customized microlens dimensions for each local region.
Solution Approach 2:
The patent changes the microlens size parameter to compensate for sensitivity deviations. By measuring the sensitivity of each pixel group and adjusting the corresponding microlens size accordingly, the system dynamically optimizes the microlens parameter to counteract the adverse effects of reduced pixel size. This parameter adjustment allows small pixels to maintain uniform sensitivity performance despite the increased crosstalk that would normally occur at smaller dimensions.
2Ease of manufacture
If uniform microlens size is used for all pixels, then manufacturing process is simplified, but sensing sensitivity uniformity deteriorates
Solution Approach 1:
The patent implements local quality by dividing pixels into multiple groups and assigning different microlens sizes to each group based on measured sensitivity characteristics. This approach maintains manufacturing feasibility through standardized group-based fabrication while achieving sensitivity uniformity across the entire sensor array. The manufacturing process remains relatively simple compared to fully individualized microlens fabrication, as pixels within each group share the same microlens size.
Solution Approach 2:
The patent applies segmentation by dividing the pixel array into multiple pixel groups, where each group is assigned a specific microlens size. This segmentation strategy balances manufacturing simplicity with sensitivity uniformity by creating discrete categories of pixels that can be processed in batches rather than requiring completely individualized fabrication for each pixel. The segmented approach maintains ease of manufacture through group-based standardization while achieving the sensitivity uniformity that would be lost with purely uniform microlens sizes.
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 approach reduces deviations in sensing sensitivity among pixels, enhancing the quality of images captured by the image sensor by optimizing light focus and distribution.
Implementation Method 1
a plurality of microlenses disposed on the color filter and having sizes different from each other such that the plurality of microlenses respectively focus an incident light to the photoelectric conversion elements
Implementation Method 2
photoelectric conversion elements disposed in a semiconductor substrate, a color filter shared by the plurality of unit pixels
Data Source
AI summary
A pixel array of an image sensor includes a plurality of pixel groups. Each pixel group includes a plurality of unit pixels adjacent to each other and respectively including photoelectric conversion elements disposed in a semiconductor substrate, a color filter shared by the plurality of unit pixels, and a plurality of microlenses disposed on the color filter and having sizes different from each other such that the plurality of microlenses respectively focus an incident light to the photoelectric conversion elements included in the plurality of unit pixels. Deviations of sensing sensitivity of unit pixels are reduced and quality of images captured by the image sensor is enhanced by adjusting sizes of microlenses.