Photoelectric Conversion Layer for Low-Complexity Global Shutter Imaging

Solution Overview

Problem

Conventional CMOS image sensors using the rolling shutter method face challenges with image distortion when capturing moving objects and inconsistent brightness, particularly when using flash, due to varying exposure start and end times across pixel array rows, necessitating the implementation of global shutter functions without increasing circuit complexity.

Innovation Solution

The imaging device employs a configuration with unit pixel cells featuring a photoelectric conversion layer between electrodes, a voltage supply circuit that applies different potential differences during exposure and non-exposure periods, and a reset transistor to manage charge accumulation, enabling global shutter operations without the need for additional transfer transistors, thus simplifying pixel circuitry.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If rolling shutter method is used, then circuit complexity is reduced, but image distortion and brightness inconsistency occur when capturing moving objects

Engineering Contradiction:

Improvecircuit complexityVSAvoidimage quality consistency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent merges the charge storage function into the photodiode structure itself by applying different potential differences to the first and second electrodes during exposure and non-exposure periods. This eliminates the need for separate transfer transistors and charge storage units in each pixel, achieving global shutter functionality while maintaining simple circuitry. The photodiode region serves dual purposes: photoelectric conversion and charge storage.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the electrical potential parameters of the photodiode by applying a first potential difference during exposure to accumulate charges and a second potential difference during non-exposure to hold or transfer charges. This parameter change approach enables global shutter operation without adding complex circuitry, as the potential control is applied to the entire pixel array simultaneously.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If transfer transistor and charge storage unit are added to each pixel for global shutter, then image distortion is eliminated, but circuit complexity increases

Engineering Contradiction:

Improveimage quality consistencyVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the charge storage function into the photodiode structure itself by applying different potential differences to the first and second electrodes during exposure and non-exposure periods. This eliminates the need for separate transfer transistors and charge storage units in each pixel, achieving global shutter functionality while maintaining simple circuitry. The photodiode region serves dual purposes: photoelectric conversion and charge storage.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent makes the photodiode structure multi-functional by enabling it to perform both photoelectric conversion and charge storage operations. By controlling the potential difference between electrodes, the same photodiode region functions as both the light-sensitive element and the charge storage element, eliminating the need for additional dedicated storage components in each pixel.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Use of energy by moving object

If rolling shutter method is used, then power consumption is low, but exposure timing varies across pixel rows causing brightness inconsistency

Engineering Contradiction:

Improvepower consumptionVSAvoidbrightness consistency

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent changes the electrical potential parameters of the photodiode by applying a first potential difference during exposure to accumulate charges and a second potential difference during non-exposure to hold or transfer charges. This parameter change approach enables global shutter operation without adding complex circuitry, as the potential control is applied to the entire pixel array simultaneously.

Inventive Principle:

Principle #35Parameter changes

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 allows for the realization of global shutter functions while maintaining low circuit complexity, reducing image distortion and brightness inconsistencies, especially when capturing moving objects and using flash, by synchronizing exposure start and end times across all pixels.

Implementation Method 1

a photoelectric converter including a first electrode, a second electrode, and a photoelectric conversion layer between the first electrode and the second electrode

Methodology Applied

Scientific EffectPhotoelectric conversion: Photovoltaic Effect

Data Source

PatentUS20240292121A1Imaging device including photoelectric conversion layer

Publication Date: 2024.08.29 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

An imaging device including pixels each including a photoelectric converter including a first electrode, a second electrode, and a photoelectric conversion layer between the first electrode and the second electrode. The imaging device further including voltage supply circuitry, where the voltage supply circuitry supplies a first potential difference between the first electrode and the second electrode in an exposure period and a second potential difference between the first electrode and the second electrode in a non-exposure period, and the first potential difference is different from the second potential difference.