Split Pixel HDR Sensor Sub-pixel Integration
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Solution Overview
Problem
Standard image sensors have a limited dynamic range, which cannot capture the full luminance range of natural scenes, leading to a decrease in overall image resolution when using HDR technologies that merge multiple exposures.
Innovation Solution
Each pixel in the image sensor is composed of multiple sub-pixels with shared floating diffusion nodes, allowing for single integration time or exposure to generate multiple output signals for bright and low light conditions, thereby increasing dynamic range without the resolution loss associated with traditional HDR methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple exposures are merged into a single HDR image sensor, then dynamic range is increased, but overall image resolution is decreased
Solution Approach 1:
Each pixel is divided into multiple sub-pixels (first sub-pixel, second sub-pixel, third sub-pixel, fourth sub-pixel) with different exposure integration times. This segmentation allows each sub-pixel to capture different luminance ranges independently, achieving HDR while maintaining full resolution by selecting the appropriate sub-pixel output for each spatial location.
Solution Approach 2:
The patent introduces a temporal dimension by using different exposure integration times for different sub-pixels within the same spatial location. This allows the sensor to capture multiple exposure levels simultaneously in a single shot, resolving the contradiction between dynamic range and resolution by adding the time dimension rather than sacrificing spatial resolution.
2Illumination intensity
If multiple exposures are captured with different integration times, then dynamic range is increased, but ghosting and light flickering issues occur
Solution Approach 1:
All sub-pixels within a pixel capture their respective exposures simultaneously during a single integration period. The different exposure levels are prepared in advance within the same temporal window, eliminating the temporal separation that causes ghosting and flickering artifacts when scenes contain moving elements.
Solution Approach 2:
Multiple exposure levels are merged at the sub-pixel level within each pixel, where first sub-pixels and third sub-pixels use a first integration time while second sub-pixels and fourth sub-pixels use a second integration time. This simultaneous capture and merging approach maintains temporal coherence across all exposure levels, preventing ghosting artifacts.
3Illumination intensity
If neutral density filters are inserted to create different sensitivities, then dynamic range is increased, but device complexity is increased
Solution Approach 1:
Instead of inserting physical neutral density filters that would increase device complexity, the patent changes the exposure integration time parameter for different sub-pixels. This parameter-based approach achieves different effective sensitivities through temporal control rather than optical filtering, simplifying the overall device structure while maintaining HDR capability.
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 high dynamic range imaging without ghosting or light flickering issues, maintaining image resolution by using the same single integration time or exposure, effectively capturing a broader range of luminance levels.
Implementation Method 1
Each pixel includes a plurality of sub-pixels... photodetector of each sub-pixel
Data Source
AI summary
A method of reading out a pixel includes photogenerating charge carriers during a single integration time in photodetectors of each one of a plurality of sub-pixels included in the pixel. Each one of the plurality of sub-pixels of the pixel has a same color filter. A floating diffusion node of the pixel is reset. The floating diffusion node is sampled to generate a reset output sample signal. Charge carriers that were photogenerated in a first portion of the plurality of sub-pixels are transferred to the floating diffusion node. The floating diffusion node is sampled to generate a first output sample signal. Charge carriers that were photogenerated in a second portion of the plurality of sub-pixels are transferred to the floating diffusion node. The floating diffusion node is sampled to generate a second output sample signal.