Configurable Shared Floating Diffusion for Image Sensor Pixel Binning
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Solution Overview
Problem
Existing image sensors face challenges in achieving high sensitivity and power efficiency, particularly in low-light conditions, due to the limitations of floating diffusion regions in CMOS image sensors with photo-sensitive layers like OPF or QDF, where reducing resolution through pixel binning can compromise image quality and sensitivity.
Innovation Solution
The implementation of pixel-binning with configurable shared floating diffusion, where disabled floating diffusion regions are electrically coupled via bridges to a common active region, allowing electrons to converge and increase the capacity of the active region, thereby enhancing sensitivity and operational range while maintaining reduced resolution only when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixel binning is implemented by having transistors connect several floating diffusions of different pixels, then sensitivity is improved, but device complexity increases
Solution Approach 1:
Multiple floating diffusion regions are merged into a single shared floating diffusion region that serves multiple pixels. This consolidation eliminates the need for separate transistors and readout circuits for each pixel in the binned group, reducing device complexity while maintaining sensitivity improvement through charge accumulation from multiple pixels.
Solution Approach 2:
The shared floating diffusion region performs multiple functions: it acts as the charge accumulation node for multiple pixels simultaneously, serves as the readout node for binned pixel groups, and replaces multiple individual floating diffusion regions. This multi-functionality reduces the overall number of components needed in the pixel array.
2Reliability
If resolution is reduced through pixel binning, then sensitivity in low-light conditions is improved, but image quality deteriorates
Solution Approach 1:
The image sensor implements dynamic pixel binning capability where the binning configuration can be changed based on lighting conditions. In low-light conditions, pixels are binned to improve sensitivity. In well-lit conditions, the sensor can switch to unbinned mode to maintain full resolution and image quality. This dynamic reconfiguration allows the system to optimize between sensitivity and image quality depending on environmental conditions.
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 configuration enhances image sensor sensitivity in low-light conditions by increasing the charge accumulation capacity of active floating diffusion regions, maintaining full sensitivity and power efficiency, and dynamically adapting to changing light conditions by enabling/disabling bridges.
Implementation Method 1
Some image sensors use materials that generate electrons in response to incident photons
Implementation Method 2
The generated charge can be accumulated (with or without a multiplication step), and then a signal indicative of the amount of accumulated charge can be read
Data Source
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AI summary
Methods, systems, computer-readable media, and apparatuses for image sensors with pixel binning with configurable shared floating diffusion are presented. In one example, an image sensor system includes a plurality of sensor elements; a photosensitive layer coupled to the plurality of sensor elements; a plurality of floating diffusion regions in communication with the photo-sensitive layer, each floating diffusion region of the plurality of floating diffusion regions configured to be selectively enabled; and at least one bridge coupled to two floating diffusion regions of the plurality of floating diffusion regions, the bridge configured to be selectively enabled and, when enabled, to allow a transfer of charge between the two floating diffusion regions.