WDR Pixel Array Dynamic Mode Switching for High Sensitivity
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Solution Overview
Problem
Current image sensors suffer from a narrow dynamic range, leading to poor expression of image colors under varying illumination conditions, particularly at high intensity, where overflow charges are often discarded, limiting sensitivity and image quality.
Innovation Solution
A 4T pixel structure with a method that includes a photo-electro conversion unit, transfer switching unit, storage region, and control circuit to read and manage overflow charges, allowing for high sensitivity under middle and high intensity illumination without additional transistors or photodiodes, utilizing a hybrid 3T and 4T pixel operation to expand the dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a 4T pixel structure is used to achieve high sensitivity under low intensity of illumination, then sensitivity under low intensity illumination is improved, but sensitivity under middle and high intensity illumination deteriorates due to overflow charges being discarded or partially stored
Solution Approach 1:
The patent implements dynamic switching between 4T and 3T pixel operations based on light intensity conditions. The control circuit determines the operational mode (4T or 3T) according to the illumination level, allowing the system to adapt its behavior dynamically. This enables the pixel array to maintain high sensitivity under low intensity illumination through 4T operation while achieving high sensitivity under middle and high intensity illumination through 3T operation, thus resolving the contradiction between sensitivity at different light intensities
Solution Approach 2:
The patent changes the operational parameter of the pixel array by switching between two distinct operational modes (4T and 3T pixel operations). By adjusting the operational mode parameter based on light intensity conditions, the system optimizes performance for different illumination scenarios. The control circuit monitors light intensity and switches the operational mode accordingly, transforming the fixed-parameter system into a variable-parameter system that adapts to different lighting conditions
2Measurement precision
If additional transistors or photodiodes are provided for high intensity of illumination, then sensitivity under high intensity illumination is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing 4T pixel structure multi-functional by enabling it to operate in two different modes (4T and 3T operations) depending on light intensity conditions. The same physical pixel array serves dual purposes: it operates as a 4T pixel for low intensity illumination and as a 3T pixel for middle and high intensity illumination. This eliminates the need for separate dedicated structures for different light intensity conditions, achieving high sensitivity under high intensity illumination without increasing device complexity
Solution Approach 2:
The patent enables the 4T pixel structure to serve itself for high intensity illumination by switching to 3T operation mode. The system uses its own existing components (transistors and photodiodes) in a different operational configuration rather than requiring external additional components. The control circuit manages the self-switching between operational modes, allowing the pixel array to self-adapt to different illumination conditions without requiring additional dedicated structures
3Reliability
If irradiation time is adjusted to achieve WDR operation, then dynamic range is improved, but timing adjustment flexibility is limited during pixel operation
Solution Approach 1:
The patent segments the pixel operation into two distinct operational modes (4T and 3T operations) that can be independently controlled based on light intensity conditions. Instead of using a single unified approach with limited timing adjustments, the system divides the operational space into two segments with different characteristics. The control circuit can selectively activate either mode, providing flexible timing adjustments for each segment. This segmentation allows the system to achieve wide dynamic range while maintaining timing adjustment flexibility by choosing the appropriate operational segment for each lighting scenario
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 enables a wide dynamic range imaging array with high sensitivity across illumination levels, maintaining linearity and ensuring image quality under low and high intensity conditions, without the need for additional components, thereby enhancing image expression and operational speed.
Implementation Method 1
a photo-electro conversion unit on a substrate
Data Source
AI summary
Disclosed is a WDR pixel array having high sensitivity under the middle intensity of illumination and high intensity of illumination by using the 4T pixel structure representing high sensitivity under the low intensity of illumination. According to the embodiment, the overflow charges generated under the very high intensity of illumination are not discarded or partially stored, but read through the 3T pixel operation, so that the WDR pixel array having high sensitivity under the middle intensity of illumination and high intensity of illumination can be obtained based on the 4T pixel structure without additionally providing a transistor or a photodiode for the high intensity of illumination in the WDR pixel array.