Solid-State Image Sensor Switch Layout for Dynamic Range and SN Ratio
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Solution Overview
Problem
Solid-state image sensors have limitations in expanding their dynamic range and signal-to-noise (SN) ratio, especially for high-sensitivity reads, due to the constraints in charge/voltage conversion capacitance and linking switch configurations.
Innovation Solution
The implementation of a solid-state image sensor design that includes a connection unit with multiple switches and a connection region, allowing for various operational modes to control the switches' states, thereby optimizing the charge accumulating units' connections across pixels to enhance capacitance and SN ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the linking switch is turned on to connect charge/voltage conversion capacitances, then the dynamic range is expanded, but the capacitance of the charge/voltage conversion region increases which reduces the charge/voltage conversion coefficient and lowers the SN ratio
Solution Approach 1:
The pixel array is divided into multiple independently controllable pixel groups, where each group can have its linking switches controlled separately. This segmentation allows selective connection of capacitances in different groups, enabling dynamic range expansion in some groups while maintaining high SN ratio in others, thus resolving the contradiction between these two parameters.
Solution Approach 2:
The patent implements dynamic control of linking switches that can be turned on or off based on imaging conditions. By dynamically adjusting the connection state of charge/voltage conversion capacitances, the system can adaptively expand dynamic range when needed while preserving high SN ratio when low light conditions require maximum sensitivity, making both parameters optimizable under different operating conditions.
2Measurement precision
If the linking switch is turned off to separate charge/voltage conversion regions, then the capacitance is reduced and charge/voltage conversion coefficient increases, but the dynamic range is limited
Solution Approach 1:
By segmenting the pixel array into multiple independently controllable groups with separate linking switch control, the system can maintain low capacitance (high conversion coefficient) in most groups while selectively expanding dynamic range in specific groups where higher capacitance is beneficial, thus resolving the contradiction between conversion coefficient and dynamic range.
Solution Approach 2:
The patent enables dynamic changing of the capacitance parameter by controlling the state of linking switches. This allows the system to adjust the charge/voltage conversion capacitance value based on imaging requirements, achieving high conversion coefficient when needed while also providing the option to expand dynamic range when conditions permit, thus resolving the fixed-parameter contradiction.
3Adaptability or versatility
If multiple switches are added to control connections between pixels, then operational flexibility and dynamic range control are improved, but device complexity increases
Solution Approach 1:
The pixel array is segmented into multiple independently controllable groups, each with its own set of linking switches. This segmentation provides operational flexibility as different groups can be controlled independently based on imaging conditions, while the modular structure prevents overall system complexity from becoming unmanageable, as each segment follows the same control pattern.
Solution Approach 2:
The linking switches are designed to serve multiple functions: they can connect adjacent pixels within a pixel group, connect pixels across different pixel groups, and be controlled independently or collectively. This multi-functionality increases operational flexibility without proportionally increasing complexity, as the same hardware structure supports multiple operational modes.
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 design effectively increases the dynamic range and SN ratio by adjusting the charge accumulation and capacitance values, enabling better signal handling and sensitivity in image capture.
Implementation Method 1
a photoelectric conversion unit and a charge accumulating unit that accumulates an electric charge from the photoelectric conversion unit
Data Source
AI summary
An image sensor includes a plurality of pixel blocks and a connection unit. The plurality of pixel blocks includes: a diffusion unit to which an electric charge resulting from photoelectric conversion is transferred; and a transistor containing a source electrically connected with the diffusion unit. The connection unit is electrically connected with a drain of the transistor included in each of the plurality of pixel blocks.