Nested Image Sensor Pixels Reducing Optical Cross-Talk
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Solution Overview
Problem
Modern imaging sensors face issues with optical cross-talk between adjacent pixels of different colors, which degrades the output image quality due to undesired exposure of photosensitive regions to light of different colors, leading to suboptimal image capture and dynamic range.
Innovation Solution
The implementation of image sensors with pixels that contain multiple photosensitive regions, specifically an inner and outer region, where the outer region is more sensitive and has a larger light collecting area, and the use of microlenses and hybrid color filters to direct light effectively, reducing cross-talk and enhancing dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single photosensitive region per pixel is used, then the device structure is simple, but optical cross-talk between adjacent pixels of different colors degrades image quality
Solution Approach 1:
Each pixel is divided into multiple photosensitive regions (first, second, third, and fourth regions), with each region having different sensitivity characteristics. This segmentation allows selective capture of light signals while reducing cross-talk between adjacent pixels of different colors, thereby improving image quality without significantly complicating the overall device structure.
Solution Approach 2:
Different photosensitive regions within the same pixel are assigned different sensitivities (e.g., first and second regions have higher sensitivity, third and fourth regions have lower sensitivity). This local differentiation enables optimized light capture for specific wavelength ranges while minimizing interference from other colors, thus enhancing image quality through localized functional specialization.
2Adaptability or versatility
If multiple photosensitive regions with different sensitivities are implemented, then dynamic range and sensitivity are improved, but device complexity increases
Solution Approach 1:
The pixel is segmented into four distinct photosensitive regions, each with tailored sensitivity characteristics. This segmentation enables the pixel to capture a broader dynamic range by simultaneously detecting both bright and dim light signals across different regions, while the segmented structure itself provides a systematic approach to managing complexity.
Solution Approach 2:
The multiple photosensitive regions are arranged in a nested or compact configuration within the pixel structure, allowing efficient use of space. This nesting approach enables high adaptability and dynamic range while minimizing the increase in device complexity through space-efficient design.
3Measurement precision
If higher sensitivity photosensitive regions are used, then light capture is improved, but cross-talk between adjacent pixels increases
Solution Approach 1:
By segmenting the pixel into multiple photosensitive regions with different sensitivities, the patent enables high-sensitivity regions to capture light effectively while low-sensitivity regions act as buffers that reduce cross-talk. This segmentation strategy allows the system to achieve high measurement precision without proportionally increasing harmful cross-talk effects.
Solution Approach 2:
Different regions are assigned different sensitivity qualities locally within the pixel. The high-sensitivity regions (first and second regions) are strategically positioned and configured to maximize light capture, while low-sensitivity regions (third and fourth regions) are positioned to minimize cross-talk, creating a local quality distribution that balances sensitivity and cross-talk reduction.
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 improves image quality by minimizing cross-talk, allowing for higher sensitivity and dynamic range, particularly in bright and low-light conditions, and reduces motion artifacts and image aberrations.
Implementation Method 1
Each pixel includes a photosensor such as a photodiode that receives incident photons (light) and converts the photons into electrical charges
Implementation Method 2
The pixel may include a microlens that may direct incident light to the outer photosensitive region
Data Source
AI summary
An image sensor may include pixel having nested photosensitive regions. A pixel with nested photosensitive regions may include an inner photosensitive region that has a rectangular light collecting area. The inner photosensitive region may be formed in a substrate and may be surrounded by an outer photosensitive region. The pixel with nested photosensitive regions may include trunk circuitry and transistor circuitry. Trunk circuitry may include a voltage supply source, a charge storage node, and readout transistors. Trunk circuitry may be located in close proximity to both the inner and outer photosensitive regions. Transistor circuitry may couple the inner photosensitive region, the outer photosensitive region, and trunk circuitry to one another. Microlenses may be formed over the nested photosensitive groups. Hybrid color filters having a single color filter region over the inner photosensitive region and a portion of the outer photosensitive region may also be used.