Virtual High-Low Sensitivity Pixels for Image Sensor Dynamic Range
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High dynamic range image sensors with dual pixels having large and small photodiodes face complexity in semiconductor process requirements, leading to asymmetric blooming, crosstalk, and noise, as well as limited full well capacity, which restricts their dynamic range and imaging performance.
Innovation Solution
The implementation of virtual high and low sensitivity photodetectors, where both photodetectors are identically sized and fabricated using the same semiconductor processing conditions, with the virtual low sensitivity photodetector having an attenuator in the optical path and the virtual high sensitivity photodetector without, simplifying fabrication and improving symmetry and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
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 and manufacturing precision deteriorates due to asymmetric blooming, crosstalk, and noise
Solution Approach 1:
The patent uses identical photodiodes for both high and low sensitivity pixels, ensuring uniform fabrication process conditions and eliminating the complexity of manufacturing different sized photodiodes. This homogeneity in photodiode structure resolves the process complexity issue while maintaining high dynamic range capability through the attenuator mechanism
Solution Approach 2:
The patent introduces an attenuator as an intermediary element in front of the low sensitivity pixel photodiode. This attenuator mediates the light intensity to create virtual low sensitivity capability without requiring physically different photodiodes, thereby avoiding the manufacturing complexity and asymmetry problems associated with dual-sized photodiode designs
2Adaptability or versatility
If dual pixels with large and small photodiodes are used to achieve high dynamic range imaging, then the dynamic range is improved, but manufacturing precision deteriorates due to asymmetric blooming, crosstalk, and noise
Solution Approach 1:
By using identical photodiodes for both high and low sensitivity pixels, the patent ensures symmetric structural properties that eliminate asymmetric blooming and crosstalk. The uniform photodiode design across all pixels guarantees consistent electrical and optical characteristics, resolving the manufacturing precision issues related to asymmetry
Solution Approach 2:
The patent creates a virtual low sensitivity pixel by placing an attenuator in front of an identical photodiode, rather than using a physically different small photodiode. This copying approach ensures that both pixel types have identical underlying structures, eliminating the crosstalk and noise asymmetry problems that arise from physically different photodiode sizes
3Adaptability or versatility
If small photodiodes are used for low sensitivity pixels, then the dynamic range is extended, but the full well capacity is limited
Solution Approach 1:
The attenuator serves as an intermediary that reduces light intensity reaching the photodiode in low sensitivity pixels. This allows the use of full-sized photodiodes with adequate full well capacity while still achieving low sensitivity operation for bright light conditions, thereby extending the high light dynamic range without sacrificing full well capacity
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 enhances imaging performance by reducing blooming, crosstalk, and photoresponse nonuniformity, while maintaining identical full well capacities for both photodetectors, thereby extending the high light dynamic range and simplifying the fabrication process.
Implementation Method 1
The virtual low sensitivity photodetector is provided by having an attenuator disposed along an optical path of incident light to the photodetector
Implementation Method 2
Both of the first and second photodetectors of each virtual high-low sensitivity grouping are disposed in semiconductor material
Data Source
AI summary
An image sensor includes a plurality of photodetectors that are identically sized and fabricated in semiconductor material with identical semiconductor processing conditions. The photodetectors are organized into virtual high-low sensitivity groupings, each including a first photodetector and a second photodetector. A plurality of attenuators is disposed over the semiconductor material. Each one of the plurality of attenuators is disposed along an optical path between a microlens and the first photodetector of each virtual high-low sensitivity grouping such that all incident light directed into the first photodetector is directed through a respective one of the plurality of attenuators. There is no attenuator along a second optical path between a microlens and the second photodetector of each virtual high-low sensitivity grouping such that all the incident light directed into the second photodetector is not directed through one of the plurality of attenuators.