Virtual Large-Small Pixel Image Sensor Using Light Masks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High dynamic range image sensors face challenges in processing complexity, asymmetric blooming, crosstalk, and limited full well capacity due to the use of dual pixels with large and small photodiodes, resulting in unbalanced imaging and limited dynamic range.
Innovation Solution
A virtual high dynamic range large-small pixel image sensor is developed, where photodiodes are arranged in symmetrical pairs and fabricated using identical semiconductor processing conditions, reducing complexity and improving symmetry for electrical and optical performance, and ensuring equal full well capacity for both large and small photodiodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dual pixels with large and small photodiodes are used to achieve high dynamic range imaging, then the dynamic range is improved, but the process complexity increases due to different semiconductor process conditions needed for fabricating large and small photodiodes
Solution Approach 1:
The patent applies asymmetry in reverse by creating symmetrical photodiodes that are identical in size and fabrication process, yet achieve different effective light sensitivity through asymmetric light blocking structures. This resolves the contradiction by eliminating the need for different process conditions while maintaining the large-small pixel functionality for high dynamic range imaging.
Solution Approach 2:
The patent introduces light blocking structures as intermediary elements between the incident light and the photodiodes. These intermediaries control the amount of light reaching each photodiode, enabling one photodiode to effectively function as a 'large' pixel and another as a 'small' pixel without actually having different photodiode sizes or requiring different fabrication processes.
2Illumination intensity
If dual pixels with large and small photodiodes are used, then high dynamic range is achieved, but asymmetric blooming and crosstalk occur resulting in unbalanced imaging
Solution Approach 1:
The patent uses asymmetry in the light blocking structures rather than in the photodiodes themselves. The symmetrical photodiodes ensure identical electrical and optical characteristics, eliminating asymmetric blooming and crosstalk, while the asymmetric light blocking achieves the desired large-small pixel effect for high dynamic range imaging.
Solution Approach 2:
The patent employs homogeneous photodiodes that are identical in size, shape, and fabrication process. This homogeneity ensures that both pixels have the same full well capacity and electrical characteristics, preventing unbalanced imaging, asymmetric blooming, and crosstalk while still achieving high dynamic range through the light blocking structures.
3Illumination intensity
If small photodiodes are used in dual pixel configuration, then high light dynamic range is limited due to limited full well capacity
Solution Approach 1:
The patent creates a virtual copy of the large pixel functionality using identical photodiodes. By blocking light from one photodiode and allowing full light access to the other, the system effectively creates a large pixel without requiring an actual larger photodiode structure, thus maintaining full well capacity while achieving high light dynamic range.
Solution Approach 2:
The patent changes the light transmission parameter rather than the photodiode physical parameters. By controlling the amount of light reaching each identical photodiode through light blocking structures, the system achieves different effective pixel sizes without changing the actual photodiode dimensions or full well capacity, thereby extending high light dynamic range performance.
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 simplifies the fabrication process, reduces blooming and crosstalk, and enhances high light dynamic range performance by maintaining symmetry and equalizing full well capacity between large and small photodiodes, leading to improved imaging capabilities.
Implementation Method 1
a plurality of photodiodes arranged into virtual large-small pixel groupings
Data Source
AI summary
An image sensor includes photodiodes arranged in semiconductor material. Each of the photodiodes is identically sized and is fabricated in the semiconductor material with identical semiconductor processing conditions. The photodiodes are organized into virtual large-small groupings including a first photodiode and a second photodiode. Microlenses are disposed over the semiconductor material with each of microlenses disposed over a respective photodiode. A first microlens is disposed over the first photodiode, and a second microlens is disposed over the second photodiode. A mask is disposed between the first microlens and the first photodiode. The mask includes an opening through which a first portion of incident light directed through the first microlens is directed to the first photodiode. A second portion of the incident light directed through the first microlens is blocked by the mask from reaching the first photodiode. There is no mask between the second microlens and the second photodiode.