Imaging Device Charge Storage Node Dynamic Range Expansion
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Solution Overview
Problem
Imaging devices face challenges in achieving high definition and dynamic range expansion while suppressing dark-current noise, particularly due to the accumulation of noise in capacitive elements connected to floating diffusion via transistors.
Innovation Solution
The imaging device incorporates a configuration with a photoelectric converter, a charge storage node, and a capacitive element connected via a transistor, allowing switching between modes to control the amount of saturated charge, and utilizes a voltage supply circuit to selectively apply voltages that enable high-speed signal readout and dynamic range expansion without accumulating dark-current noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pixels is increased to achieve higher definition, then the imaging resolution is improved, but the area of each pixel and the light receiver area are reduced, leading to decreased sensitivity
Solution Approach 1:
The imaging device is divided into multiple pixels arranged in an array, with each pixel further segmented into photoelectric conversion units and charge storage nodes. This segmentation allows efficient use of limited pixel area while maintaining overall high resolution
Solution Approach 2:
The patent transitions from planar pixel structure to a three-dimensional stacked structure with photoelectric conversion layers and charge storage nodes at different vertical levels, effectively increasing the light receiver area without expanding the horizontal pixel footprint
2Measurement precision
If the area of each pixel is reduced to increase pixel count, then the imaging resolution is improved, but the amount of saturated charge in each pixel is reduced
Solution Approach 1:
By stacking photoelectric conversion units and charge storage nodes vertically at different levels, the patent increases the total charge storage capacity within each pixel without increasing the horizontal pixel area, thus maintaining high resolution while increasing saturated charge amount
Solution Approach 2:
Multiple charge storage nodes are nested within each pixel structure at different vertical levels, allowing cumulative charge storage capacity to exceed what would be possible in a single-planar configuration
3Adaptability or versatility
If a capacitive element is connected to floating diffusion via transistor to expand dynamic range, then the amount of saturated charge is increased, but dark-current noise accumulates in the capacitive element
Solution Approach 1:
The patent extracts the capacitive element from direct connection to the floating diffusion node, instead connecting it to charge storage nodes at different potentials. This separation prevents dark-current noise generated at the transistor from being directly accumulated in the capacitive element, while still enabling dynamic range expansion through controlled charge transfer
Solution Approach 2:
The patent introduces intermediate charge storage nodes as mediators between the transistor and capacitive element. These intermediate nodes allow controlled charge transfer to expand dynamic range while isolating the capacitive element from direct dark-current noise paths
4Reliability
If the area of light receiver in each pixel is increased to improve sensitivity, then the sensitivity is improved, but the number of pixels that can be packed is reduced, decreasing imaging resolution
Solution Approach 1:
The patent utilizes vertical stacking to increase light receiver area in the z-dimension while maintaining compact horizontal footprint, allowing larger effective photoelectric conversion area per pixel without reducing pixel density and thus maintaining high imaging resolution
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 effectively expands the dynamic range and suppresses dark-current noise, enabling higher definition and faster signal readout by switching between modes based on the voltage applied to the transistor, thereby optimizing pixel performance.
Implementation Method 1
a photoelectric converter that generates signal charge
Data Source
AI summary
An imaging device includes a photoelectric converter that generates signal charge; a charge storage node that stores the signal charge; a capacitive element connected to the charge storage node; and a first transistor connected to the charge storage node via the capacitive element, wherein switching between on-state and off-state of the first transistor causes an amount of saturated charge in the charge storage node to change.