Image Pickup Device Input Node Capacitance Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing image pickup devices face issues with uneven stabilization of potential at the input node of amplifying transistors due to varying coupling capacitance among pixels, leading to uneven signal output and incorrect image formation.
Innovation Solution
An image pickup device with a potential supply unit that provides a first, second, and third potential to a switch connected to the input node, allowing for controlled switching of capacitance values, thereby stabilizing the potential across all pixels uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a switch is used to switch capacitance values at the input node by changing potential from first potential to second potential, then the dynamic range of signal output is expanded, but the potential stabilization time becomes uneven among pixels due to varying coupling capacitance
Solution Approach 1:
The patent introduces a third potential (intermediate potential) between the first potential (high potential) and second potential (low potential) as an intermediary state. When switching capacitance values, the potential changes through this intermediate third potential, which reduces the potential difference applied to pixels with large coupling capacitance. This mediator potential stabilizes the potential change rate across all pixels, preventing uneven stabilization while maintaining the dynamic range expansion capability.
Solution Approach 2:
The patent changes the potential parameter from a binary state (first potential/second potential) to a three-state system (first potential/third potential/second potential). By introducing the third potential as an intermediate step, the potential transition is controlled to occur at a uniform rate across all pixels regardless of their coupling capacitance variations, thereby achieving consistent potential stabilization while preserving the ability to switch capacitance values for dynamic range expansion.
2Quantity of substance
If capacitance value is increased by connecting capacitance to input node, then amount of electric charge that can be processed increases, but gain of amplifying transistor decreases
Solution Approach 1:
The patent implements dynamic switching of capacitance values by controlling a switch that connects or disconnects the capacitance to the input node based on illumination levels. Under high illumination, the capacitance is connected to increase the amount of electric charge that can be processed, preventing saturation. Under low illumination, the capacitance is disconnected to maintain high gain for weak signals. This dynamic adjustment allows the system to adapt to varying light conditions and optimize both charge processing capacity and signal gain.
Solution Approach 2:
The patent applies partial action by selectively connecting the capacitance only when necessary (under high illumination conditions) rather than continuously. The switch controls the capacitance connection based on the actual signal level, connecting the capacitance to process excess charge when illumination is strong, and disconnecting it when illumination is weak to preserve gain. This selective application optimizes the trade-off between charge processing capacity and signal gain.
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
Ensures consistent potential stabilization across pixels, reducing noise and improving signal quality by adjusting capacitance values based on illumination levels, resulting in a correct image even under varying light conditions.
Implementation Method 1
a photoelectric conversion unit; an amplifying transistor provided with an input node in which a charge generated in the photoelectric conversion unit is input
Data Source
AI summary
The capacitance value of the input node is set to a first capacitance value when a first potential is supplied to the switch. The capacitance value of the input node is set to a second capacitance value which is smaller than the first capacitance value when a second potential is supplied to the switch. The potential supplied to the switch is kept at a third potential which is a potential between the first potential and the second potential in a part of at least one of a period until the potential is set to the first potential from the second potential and a period until the potential is set to the second potential from the first potential.