Dual Pinned Diode Pixel Shutter for Motion Artifact Reduction
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Solution Overview
Problem
Conventional rolling shutter imagers are unsuitable for capturing images with moving objects and lack precise control over exposure time, especially in scenes with varying light intensities, and existing electronic shutters using capacitors suffer from decreased efficiency and increased noise susceptibility.
Innovation Solution
A pixel architecture incorporating an electronic shutter circuit with a shutter transistor and a pinned diode, where the pinned diode acts as a charge storage device and the shutter transistor controls charge transfer from the photodiode to the source region of the source follower transistor, enabling simultaneous imaging and precise exposure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional rolling shutter architecture is used, then device complexity is reduced, but imaging precision deteriorates due to sequential row imaging causing motion artifacts
Solution Approach 1:
The pixel array is segmented into multiple rows that can be independently controlled. Each row has its own transfer transistor and source follower circuit, allowing sequential activation of rows while maintaining simultaneous charge accumulation across all pixels. This segmentation enables rolling shutter operation that reduces motion artifacts without requiring complex global shutter hardware.
Solution Approach 2:
The patent implements dynamic control of charge transfer timing for each row. The transfer transistor is activated at different times for different rows, creating a dynamic rolling shutter effect. This dynamic timing control allows the system to adapt to motion in the scene by controlling when each row's charge is read out, reducing motion artifacts while maintaining relatively simple hardware architecture.
2Measurement precision
If a capacitor-based electronic shutter is used, then exposure control precision is improved, but pixel fill factor decreases and noise susceptibility increases
Solution Approach 1:
The capacitor-based shutter circuit is extracted and replaced with a pinned diode-based charge storage mechanism. The pinned diode is integrated directly into the pixel's charge accumulation region, eliminating the need for separate capacitor structures that would reduce fill factor. This extraction of the shutter function into a different physical implementation maintains exposure control while preserving pixel area.
Solution Approach 2:
The patent changes the physical state and properties of the charge storage element from a capacitor to a pinned diode. The pinned diode utilizes the photoconductive properties of semiconductor material, changing the fundamental parameter of charge storage from electrical capacitance to semiconductor-based charge accumulation. This parameter change enables better integration with the photodiode structure, maintaining fill factor while providing precise exposure control.
3Measurement precision
If a capacitor-based electronic shutter is used, then exposure control is improved, but reliability deteriorates due to increased noise susceptibility
Solution Approach 1:
The patent replaces the capacitor-based electronic shutter system with a pinned diode-based charge storage and control system. This substitution involves replacing the electrical capacitance mechanism with a semiconductor-based pinned diode structure that provides charge storage and shutter control functions. The pinned diode structure inherently provides better noise performance and reliability while maintaining exposure control 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 solution allows for accurate and efficient exposure control in full frame mode, reducing noise susceptibility and maintaining high pixel fill factor, suitable for capturing images with moving objects and varying light conditions.
Implementation Method 1
a pinned diode 302... the pinned diode acts as a charge storage device
Implementation Method 2
The photodiode 101 is exposed to light during a charge integration period... The photodiode 101 produces a current related to the amount of incident light. Charge accumulates at node P
Data Source
AI summary
A pixel having an electronic shutter suitable for use in a pixel array of an imaging device includes a pinned diode and a shutter transistor. The pinned diode is utilized as a storage device while the shutter transistor controls charge transfer from the electronic shutter. The use of a pinned diode as a charge storage device for the electronic shutter permits greater charge transfer efficiency, has lower leakage (or “dark” current), and permits the resulting pixel to have a greater fill factor than pixels utilizing conventional electronic shutter circuits.