Dynamic Pixel Management for CMOS Image Sensor Mode Switching

Solution Overview

Problem

Current CMOS image sensors face challenges in efficiently managing pixel operations between high definition (HD) and ultra-high definition (UHD) modes, particularly in reducing interconnection complexity and maintaining performance while reading out individual photodiodes in shared pixel arrays.

Innovation Solution

The implementation of a dynamic pixel management system that includes a shared pixel array with multiple photodiodes and a floating diffusion, along with vertical and horizontal charge circuitry, allows for switching between HD and UHD modes by sequentially or concurrently transferring charges, enabling individual or collective sampling of photodiode outputs, and using storage capacitors to store sampled values for image generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If individual photodiodes in shared pixel units are read out sequentially in UHD mode, then measurement precision and image quality are improved, but device complexity and interconnection overhead increase

Engineering Contradiction:

Improveimage qualityVSAvoidinterconnection overhead

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Multiple photodiodes within a shared pixel unit are merged to share common circuitry including the floating diffusion, readout circuitry, and interconnections. This combining approach allows individual photodiode readout for high-quality UHD imaging while reducing the total number of separate interconnections needed compared to having fully independent pixels for each photodiode.

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If pixel array density is increased for UHD mode, then productivity and resolution are improved, but device complexity and wiring complexity increase

Engineering Contradiction:

ImproveresolutionVSAvoidwiring complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The shared pixel unit structure implements multi-functionality where a single pixel unit can operate in multiple modes: UHD mode where individual photodiodes are read out sequentially, and HD mode where photodiodes are binned concurrently. The same physical structure and interconnections serve both high-resolution and high-speed modes, eliminating the need for separate wiring systems for each mode.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system dynamically switches between different operational modes (UHD and HD) by controlling the timing and sequence of transfer gate activation. This dynamic operation allows the same hardware to adapt its functionality based on the desired output, optimizing the balance between resolution and speed without requiring physical reconfiguration of interconnections.

Inventive Principle:

Principle #15Dynamics

3Productivity

If photodiodes are binned concurrently in HD mode, then productivity and readout speed are improved, but measurement precision decreases

Engineering Contradiction:

Improvereadout speedVSAvoidimage quality

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system dynamically switches between different operational modes (UHD and HD) by controlling the timing and sequence of transfer gate activation. This dynamic operation allows the same hardware to adapt its functionality based on the desired output, optimizing the balance between resolution and speed without requiring physical reconfiguration of interconnections.

Inventive Principle:

Principle #15Dynamics

4Adaptability or versatility

If cross pixel interconnection is implemented, then adaptability and mode switching capability are improved, but device complexity increases

Engineering Contradiction:

Improvemode switching capabilityVSAvoidcircuit complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple photodiodes within a shared pixel unit are merged to share common circuitry including the floating diffusion, readout circuitry, and interconnections. This combining approach allows individual photodiode readout for high-quality UHD imaging while reducing the total number of separate interconnections needed compared to having fully independent pixels for each photodiode.

Inventive Principle:

Principle #5Merging (Combining)

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 approach reduces the required output bandwidth, minimizes noise, and improves pixel performance by reducing wiring complexity, enabling efficient readout of pixel values and supporting both HD and UHD modes with reduced interconnection overhead.

Implementation Method 1

The photodiode generates electric charges using absorbed light

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS10270987B2System and methods for dynamic pixel management of a cross pixel interconnected CMOS image sensor

Publication Date: 2019.04.23 GRASS VALLEY CANADA

AI summary

A camera using a CMOS image sensor based on a shared pixel array technology avails both high definition (HD) and ultra-high definition (UHD) resolution mode formats. Dynamic pixel management allows for both sequential and binned timing formats of pixel signals using switched capacitor noise reduction techniques. When UHD resolution mode is selected, noise can be reduced using both digital double sampling (DDS) or differential digital double sampling (dDDS), and when HD resolution mode is selected noise can be reduced using DDS. Additionally, both rolling shutter and global shutter modes can be selected when HD resolution mode is selected.