Imager Pixel Reset Timing for Extended Dynamic Range
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Solution Overview
Problem
Conventional imagers face limitations in dynamic range, leading to image distortion due to insufficient light intensity handling, with existing methods like signal companding and multiple captures causing noise and requiring additional circuitry or memory.
Innovation Solution
Implementing multiple pixel resets based on varying light intensities during a frame time, where pixels exposed to high light are reset later than those exposed to low light, allowing for expanded dynamic range through digital signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If signal companding is used to extend dynamic range, then dynamic range is improved, but noise increases and device complexity increases
Solution Approach 1:
The pixel array is divided into multiple zones based on light intensity characteristics. Each zone is assigned a different integration time, allowing the system to capture both bright and dark regions effectively without the noise amplification problems of signal companding.
Solution Approach 2:
The system performs preliminary classification of pixels into zones based on expected light intensity before image capture. This allows each pixel to be pre-configured with an appropriate integration time, avoiding the need for post-capture signal companding that introduces noise.
2Adaptability or versatility
If multiple captures are used to extend dynamic range, then dynamic range is improved, but device complexity and memory requirements increase
Solution Approach 1:
The system dynamically adjusts the integration time for each pixel based on its zone classification, rather than using multiple static captures. This dynamic approach achieves extended dynamic range using the same pixel array and readout circuitry, avoiding additional memory and circuitry requirements.
3Adaptability or versatility
If multiple captures are used to extend dynamic range, then dynamic range is improved, but memory requirements increase
Solution Approach 1:
The system discards the need for multiple captured images by using a single capture with zone-based integration time adjustment. This recovers memory resources that would otherwise be required to store multiple captures, achieving extended dynamic range with minimal memory usage.
4Device complexity
If conventional single integration time is used, then device complexity is reduced, but dynamic range is insufficient and image distortion occurs
Solution Approach 1:
Different regions (zones) of the pixel array are assigned different integration times based on their local light intensity characteristics. This local customization extends dynamic range without requiring complex additional circuitry, as each pixel operates independently with its assigned parameters.
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 the dynamic range of imagers by reducing noise and preventing saturation, while minimizing the signal-to-noise ratio dip and reducing memory requirements through zone-based light intensity mapping.
Implementation Method 1
Each of the cells includes a photoconversion device or photosensor such as, for example, a photogate, photoconductor, or photodiode, for generating and accumulating photo-generated charge
Data Source
AI summary
The dynamic range of a pixel is increased by using selective photosensor resets during a frame time of image capture at a timing depending on the light intensity that the pixel will be exposed to during the frame time. Pixels that will be exposed to high light intensity are reset later in the frame than pixels that will be exposed to lower light intensity.