Sub-Pixel Image Sensor Layout for Low-Light Charge Summation

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Solution Overview

Problem

Current image sensing devices face challenges in achieving high signal-to-noise ratio (SNR) and image quality, particularly at night, due to limitations in light reception area uniformity and charge summation across sub-pixels.

Innovation Solution

The image sensing device incorporates a pixel group arrangement with multiple sub-pixels connected to floating diffusion regions, where an odd number of photoelectric conversion units are electrically connected in common, and even number of floating diffusion regions are electrically connected, allowing for uniform light reception and charge summation using a binning mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple sub-pixels are arranged in a pixel group with common floating diffusion regions, then charge summation capability is improved, but light reception area uniformity deteriorates

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidlight reception area uniformity

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The pixel array is divided into multiple pixel groups, where each pixel group contains multiple sub-pixels (e.g., 3x3 arrangement) that share common floating diffusion regions. This segmentation allows independent charge summation control for each pixel group while maintaining overall array functionality, resolving the contradiction between charge summation capability and light reception uniformity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple photoelectric conversion units (sub-pixels) within each pixel group are merged to share common floating diffusion regions for charge collection. This merging enables charge summation across multiple sub-pixels, improving signal-to-noise ratio by combining signals from adjacent pixels while the segmented pixel group structure maintains light reception uniformity.

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If an odd number of photoelectric conversion units are connected to a common floating diffusion region, then charge summation efficiency is improved, but circuit complexity increases

Engineering Contradiction:

Improvecharge summation efficiencyVSAvoidcircuit complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent implements different connection configurations for different pixel groups based on their local requirements. Some pixel groups use odd-numbered sub-pixel arrangements (e.g., 3x3=9 sub-pixels) connected to common floating diffusion regions, while others use even-numbered arrangements. This local quality approach allows charge summation efficiency to be optimized in specific regions without increasing overall circuit complexity across the entire array.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The floating diffusion regions are designed to serve multiple functions: they act as charge collection nodes for multiple sub-pixels within a pixel group, enable charge summation, and maintain electrical connectivity across the pixel array. This multi-functionality reduces the need for additional dedicated circuits, thereby improving charge summation efficiency without proportionally increasing circuit complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Quantity of substance

If even number of floating diffusion regions are electrically connected, then charge collection capability is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvecharge collection capabilityVSAvoidfloating diffusion region alignment

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent employs asymmetric arrangements of floating diffusion regions within pixel groups, where the number and positioning of floating diffusion regions are deliberately designed to be uneven rather than symmetric. For example, a pixel group may have 3 sub-pixels connected to 2 floating diffusion regions in an asymmetric configuration. This asymmetry allows flexible charge collection from multiple sub-pixels while reducing the stringency of alignment requirements compared to symmetric configurations, thereby improving charge collection capability without excessively increasing manufacturing precision demands.

Inventive Principle:

Principle #4Asymmetry

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 the signal-to-noise ratio (SNR) and improves image quality, especially in low-light conditions by ensuring uniform light reception and efficient charge summation across the pixel group.

Implementation Method 1

one or more groups of an odd number photoelectric conversion units structured to convert incident light to generate electrical charge

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS12200382B2Image sensing device having pixel group including a plurality of sub pixels

Publication Date: 2025.01.14 SK HYNIX INC

AI summary

An image sensing device may include one or more pixel groups arranged in rows and columns in an array, each pixel group being arranged at an intersection between a row and a column of the array, wherein each pixel group comprises one or more floating diffusion regions, and one or more groups of an odd number photoelectric conversion units structured to convert incident light to generate electrical charge, each group of the odd number of photoelectric conversion units electrically connected in common to one of the floating diffusion regions for receiving the generated electrical charge.