Imaging Pixel Inversion Region Dynamic Range Extension
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Solution Overview
Problem
Classic image sensors have limitations in capturing a high dynamic range of light intensities, typically achieving a dynamic range of 10000:1, which is insufficient for many imaging applications, and existing solutions often require complex switch arrangements and control infrastructure to achieve multiple sensitivity ranges.
Innovation Solution
A pixel element for image sensors that includes a semiconductor substrate with a radiation-sensitive element, a charge accumulation region, and an electrode forming an inversion region, allowing for the extension of charge storage capacity by applying voltage, enabling multiple sensitivity ranges with equal integration times and a high dynamic range without complex switch arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple piece-wise linear slopes or logarithmic responses are used to increase dynamic range, then the dynamic range is improved, but the device complexity increases due to multiple capacitors and storage gates
Solution Approach 1:
The patent merges multiple sensitivity ranges into a single pixel element by combining a photodiode with multiple capacitors (first capacitor C1 and second capacitor C2) that can be selectively connected through transfer gates. This integration allows the pixel to capture both bright and dark regions within the same integration period, achieving extended dynamic range without requiring multiple separate pixels or complex mechanical structures.
Solution Approach 2:
The patent implements dynamic switching between different capacitor configurations using transfer gates (TG1, TG2, TG3) that can redirect charge packets between capacitors based on the brightness level. This dynamic charge redistribution allows the system to adapt to varying light intensities during the integration period, effectively capturing a wide dynamic range through electronic control rather than fixed structural arrangements.
2Illumination intensity
If non-destructive readout or charge coupled devices with two wells are used, then the dynamic range is improved, but the device complexity and control infrastructure requirements increase
Solution Approach 1:
The patent segments the charge storage function into multiple distinct capacitors (C1 for bright regions, C2 for dark regions) within a single pixel element. Each capacitor is optimized for specific brightness ranges, and transfer gates selectively route charge packets to the appropriate capacitor based on the local brightness level. This segmentation allows independent optimization of each storage region while maintaining a unified control structure.
Solution Approach 2:
The transfer gates (TG1, TG2, TG3) act as intermediary elements that mediate the flow of charge packets between the photodiode and the different capacitors. These intermediary components enable flexible charge redistribution without requiring complex mechanical switches or multiple readout paths, simplifying the overall control infrastructure while achieving extended dynamic range.
3Illumination intensity
If multiple shorter integration periods are used, then the dynamic range is improved, but the measurement precision and integration time control become more difficult
Solution Approach 1:
The patent maintains continuous charge accumulation during a single integration period by using multiple capacitors that can be simultaneously charged from the photodiode. The first capacitor C1 accumulates charge for bright regions while the second capacitor C2 accumulates charge for dark regions, both operating continuously throughout the integration period. This continuous action eliminates the need for multiple discrete integration periods and their associated timing complexities.
Solution Approach 2:
The patent changes the effective capacitance parameter dynamically by selecting which capacitor to use based on the brightness level. The transfer gates enable switching between different capacitance values (C1 for bright, C2 for dark) without changing the integration time or exposure duration. This parameter change approach allows extended dynamic range while maintaining precise integration time control through a single, well-defined integration period.
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
The solution allows for high dynamic range imaging with a combined sensitivity range of up to 100000:1, enabling efficient simultaneous measurements in multiple sensitivity ranges while maintaining equal integration times, thus overcoming the limitations of classic image sensors.
Implementation Method 1
a radiation-sensitive element configured to generate electric charges in response to incident radiation
Implementation Method 2
an electrode arranged on the semiconductor substrate adjacent to the charge accumulation region, the electrode being electrically insulated from the semiconductor substrate such as to form an inversion region in the semiconductor substrate that connects to the charge accumulation region when a voltage is applied to said electrode
Data Source
AI summary
A pixel element for an imaging sensor comprises a semiconductor substrate, a radiation-sensitive element configured to generate electric charges in response to incident radiation, a charge accumulation region provided in the semiconductor substrate configured to accumulate at least a portion of the electric charges, and an electrode arranged on the semiconductor substrate adjacent to the charge accumulation region. The electrode is electrically insulated from the semiconductor substrate such as to form an inversion region in the semiconductor substrate that connects to the charge accumulation region when a voltage is applied to said electrode.