Image Sensor Pixel Unit Potential Barrier Segmentation

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Solution Overview

Problem

Conventional image sensor devices face challenges in providing high dynamic signal range and accurate correlated double sampling (CDS) operations, especially in bright and dark conditions, due to limitations in circuit design.

Innovation Solution

The image sensor device incorporates a pixel unit structure with specific transistors and potential barriers, allowing for true CDS operation and high dynamic range imaging by controlling potential wells to capture and reset signals effectively, suitable for both global and rolling shutter modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional image sensor circuit design is used, then device complexity is reduced, but signal discrimination in dark condition deteriorates and signal saturation in bright condition occurs

Engineering Contradiction:

Improvesignal discriminationVSAvoidcircuit design

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The pixel unit is segmented into multiple functional regions with different potential barriers: a first potential barrier region for capturing signal charges and a second potential barrier region for resetting. This segmentation allows independent optimization of signal discrimination and saturation prevention without requiring complex external circuitry.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions within the pixel unit are assigned different local properties through controlled potential barriers. The first region maintains a higher potential barrier for dark condition sensitivity, while the second region provides a lower potential barrier to prevent bright condition saturation, enabling localized optimization of imaging performance.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If conventional circuit design is used, then manufacturing is simpler, but high dynamic range imaging capability is lost

Engineering Contradiction:

Improvehigh dynamic range capabilityVSAvoidcircuit design

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

Multiple functions (signal capture, reset, potential barrier control) are merged into a single pixel unit structure. The reset control transistor integrates reset functionality with potential barrier management, eliminating the need for separate complex circuit blocks while achieving HDR capability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The pixel unit structure serves multiple functions simultaneously: it captures signals in dark conditions, prevents saturation in bright conditions, and enables true CDS operation. This multi-functionality is achieved through the universal pixel unit design that incorporates both potential barrier regions and the reset control transistor.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If conventional sampling operation is used, then operation speed is maintained, but true CDS operation cannot be achieved

Engineering Contradiction:

ImproveCDS operation accuracyVSAvoidsampling operation

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The reset operation is performed preliminarily before signal transfer, establishing a known baseline state in the first floating diffusion node. This preliminary reset action enables accurate correlated double sampling by ensuring consistent initial conditions for subsequent signal measurements.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The first floating diffusion node serves as an intermediary between the photodiode and the output amplifier. It temporarily holds signal charges after transfer and provides a stable intermediate state that facilitates precise CDS operation by decoupling the signal transfer timing from the readout timing.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enables accurate sampling of pixel image signals and pixel reset signals with improved signal discrimination in various lighting conditions, avoiding signal saturation and achieving high dynamic range imaging with a single exposure operation.

Implementation Method 1

Each pixel unit comprises a photodiode... The photodiode is coupled to a ground level

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS11457163B1Image sensor device capable of improving signal discrimination in dark condition and avoiding signal saturation in bright condition

Publication Date: 2022.09.27 PIXART IMAGING INC

AI summary

An image sensor device is provided to effectively improve the signal discrimination of sensed/sampled pixel values/signals in the image sensor device operating in a dark condition as well as effectively avoiding signal saturation when such image sensor device operates in a light/bright condition. Such image sensor device, when operating in dark/light conditions, can perform the exposure operation to get/sample accurate pixel image signal and pixel reset signal for only one time without estimating the pixel image signal and pixel reset signal by performing the exposure operation twice.