Solid-State Imaging Device Pixel Bank Architecture for Sensitivity and Shading
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Solid-state imaging devices face challenges in achieving high sensitivity while preventing color shading and afterimages, especially in low-luminance conditions, due to increased pixel size and vignetting effects, which deteriorate image quality.
Innovation Solution
The device incorporates a configuration with multiple photoelectric conversion portions, transfer gates, and a floating diffusion structure, where the transfer gates are strategically positioned between the photoelectric conversion portions and the floating diffusion to ensure uniform light reception and efficient charge transfer, preventing color shading and improving sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is increased to improve sensitivity, then light-receiving area is increased, but vignetting effect increases causing color shading
Solution Approach 1:
The imaging device divides the pixel array into multiple banks (e.g., first bank and second bank), where each bank has its own readout circuitry. This segmentation allows independent optimization of each bank's light-receiving area without the vignetting effects affecting the entire array, thus maintaining high sensitivity while reducing color shading.
Solution Approach 2:
The patent introduces a bank dimension in addition to the row and column dimensions of the pixel array. By organizing pixels into multiple banks that can be read out through different pathways, the system effectively adds a dimensional degree of freedom that decouples the relationship between pixel size and vignetting effects.
2Measurement precision
If pixel size is increased to improve sensitivity, then light-receiving area is increased, but afterimages occur
Solution Approach 1:
By dividing the pixel array into multiple banks with separate readout circuits, the patent enables faster charge transfer and readout times for each individual bank. This reduced charge storage time in each bank minimizes the persistence of residual charges that cause afterimages, while the large pixel size in each bank maintains high sensitivity.
3Volume of moving object
If pixel size is decreased to reduce device size, then device compactness is improved, but sensitivity decreases
Solution Approach 1:
The patent merges multiple small pixels within each bank to function as a larger effective pixel for light collection, while maintaining the physical compactness of individual pixels. This allows the device to achieve high sensitivity equivalent to larger pixels while keeping the overall device size small through efficient spatial arrangement.
Solution Approach 2:
By introducing the bank organization dimension, the patent allows small pixels to achieve the sensitivity of large pixels through temporal and organizational multiplexing. Multiple small pixels in each bank can be combined computationally or through charge summation to achieve large-pixel sensitivity while maintaining compact physical dimensions.
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 enhances image quality by preventing color shading and afterimages, while maintaining high sensitivity, particularly in low-luminance conditions, and is suitable for small-sized electronic devices like capsule endoscopes.
Implementation Method 1
The photoelectric conversion portion is, for example, a photodiode and generates signal charges by receiving incident light incident through an externally attached optical system by a light-receiving plane and photoelectrically converting the light.
Data Source
AI summary
A solid-state imaging device including an imaging area where a plurality of unit pixels are disposed to capture a color image, wherein each of the unit pixels includes: a plurality of photoelectric conversion portions; a plurality of transfer gates, each of which is disposed in each of the photoelectric conversion portions to transfer signal charges from the photoelectric conversion portion; and a floating diffusion to which the signal charges are transferred from the plurality of the photoelectric conversion portions by the plurality of the transfer gates, wherein the plurality of the photoelectric conversion portions receive light of the same color to generate the signal charges, and wherein the signal charges transferred from the plurality of the photoelectric conversion portions to the floating diffusion are added to be output as an electrical signal.