Imaging Device Pixel Logic Transistor Dynamic Range
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Solution Overview
Problem
Conventional imaging devices face limitations in achieving high dynamic range and reducing pixel readout noise, particularly due to long intervals between refresh operations for reset and transfer gate voltages, which affect image quality and response to incident light.
Innovation Solution
Incorporating a logic transistor in each pixel to enable selective reset and integration initiation on a pixel-by-pixel basis, with reduced gate threshold voltage and level shifting circuits to optimize dynamic range and reduce noise, along with periodic refresh of reset transistor gate voltage to minimize leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional imaging devices are used without pixel-by-pixel selective reset, then device complexity is reduced, but the maximum interval between refresh operations increases leading to increased leakage currents and reduced dynamic range
Solution Approach 1:
The patent divides the imaging device into individual pixel units, each with its own logic transistor capable of independent operation. This segmentation allows each pixel to be reset and integrated independently, enabling precise control of refresh operations at the pixel level rather than requiring global refresh operations, thus reducing the maximum interval between refresh operations and minimizing leakage currents.
Solution Approach 2:
The patent introduces dynamic control capabilities through logic transistors that enable selective reset and integration initiation on a pixel-by-pixel basis. This dynamic approach allows the system to adapt refresh timing to actual pixel needs rather than using fixed refresh intervals, optimizing the balance between leakage current minimization and operational flexibility.
2Manufacturing precision
If logic transistors with reduced gate threshold voltage are incorporated, then pixel output voltage range increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent deliberately changes the gate threshold voltage parameter of the logic transistor to a reduced value, which directly increases the pixel output voltage range and improves dynamic range performance. This parameter modification is achieved through standard CMOS fabrication processes with adjusted doping profiles or transistor geometry, balancing the need for enhanced performance with manufacturability constraints.
3Object-generated harmful factors
If periodic refresh of reset transistor gate voltage is implemented, then leakage currents are minimized, but use of energy increases
Solution Approach 1:
The patent implements periodic refresh operations for the reset transistor gate voltage, where each pixel is refreshed at intervals optimized to minimize leakage current accumulation. The periodic nature of this operation allows the system to balance leakage mitigation with energy conservation, as refresh operations are performed only when necessary rather than continuously, thus reducing overall power consumption while maintaining signal integrity.
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 significantly reduces the maximum interval between refresh operations, enhancing pixel output voltage range and image quality by minimizing noise and maintaining optimal operating voltages, thereby improving the dynamic range and performance of imaging devices.
Implementation Method 1
pixel light sensing photodiode 205
Data Source
AI summary
The present invention relates to improved imaging devices having high dynamic range and to monitoring and automatic control systems incorporating the improved imaging devices.