TOF Pixel Sensor Layout for High Modulation Contrast

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional time-of-flight (TOF) pixel sensors suffer from high temporal noise, high power consumption, low charge modulation frequency, and high modulation latency, leading to low modulation contrast and reduced sensor precision.

Innovation Solution

Implementing structures that increase vertical electric field strength, reduce charge transfer barriers, and utilize storage diodes adjacent to a silicon photoconversion structure for low latency charge storage, along with continuous phase modulation and light retention structures to enhance modulation contrast.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional TOF pixel sensors use standard charge transfer mechanisms, then device complexity is maintained at acceptable levels, but modulation contrast remains low due to high temporal noise and slow charge transfer

Engineering Contradiction:

Improvemodulation contrastVSAvoidsensor structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The sensor is divided into multiple independent pixel elements, each with its own photoconversion structure and storage diode. This segmentation allows each pixel to independently perform high-contrast modulation while maintaining overall system manageability and avoiding excessive complexity at the system level.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Storage diodes are introduced as intermediary structures between the photoconversion structure and readout circuitry. These diodes act as charge storage intermediaries that enable low-latency charge accumulation and facilitate high-frequency modulation without requiring complex direct readout mechanisms from each photodetector.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If charge transfer barriers are reduced to enable faster charge transfer, then modulation frequency increases, but vertical electric field strength decreases leading to lower modulation contrast

Engineering Contradiction:

Improvemodulation frequencyVSAvoidmodulation contrast

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The electric field distribution is optimized locally within each pixel structure. Storage diodes are positioned adjacent to photoconversion structures to create localized regions of high electric field strength that enhance charge transfer efficiency and modulation contrast without requiring uniformly high fields across the entire sensor, thus maintaining high modulation frequency.

Inventive Principle:

Principle #3Local quality

3Productivity

If storage diodes are positioned away from photoconversion structures, then device layout is simpler, but charge transfer latency increases reducing modulation frequency

Engineering Contradiction:

Improvemodulation frequencyVSAvoidpixel structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The storage diode and photoconversion structure are merged into a tightly integrated adjacent configuration within each pixel element. This merging minimizes the physical distance for charge transfer, enabling low-latency charge storage and high-frequency modulation while maintaining a compact pixel structure that does not significantly increase overall device complexity.

Inventive Principle:

Principle #5Merging (Combining)

4Reliability

If continuous current flow is used for modulation, then modulation response is continuous, but power consumption increases significantly

Engineering Contradiction:

Improvemodulation response continuityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The modulation system uses periodic phase modulation signals applied to modulation gates rather than continuous current flow. This periodic action achieves continuous modulation response through alternating charge transfer between storage diodes while consuming significantly less power, as current flows only during discrete modulation cycles rather than continuously.

Inventive Principle:

Principle #19Periodic action

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

Achieves significantly higher modulation contrast, reducing temporal noise and enabling high-frequency, high-precision depth/distance resolution in TOF sensors.

Implementation Method 1

a silicon photoconversion structure to enable low latency charge storage

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

structures that increase vertical electric field strength

Methodology Applied

Scientific EffectElectric field: Electric Field

Data Source

PatentUS12439732B1Time-of-flight pixel sensor with high modulation contrast

Publication Date: 2025.10.07 GIGAJOT TECHNOLOGY INC

AI summary

First and second modulation gates disposed adjacent a silicon photoconversion structure generate, throughout the exposure interval, alternating first and second electrostatic fields that compel photocharge generated within the silicon photoconversion structure to the first and second storage diodes, respectively. Upon conclusion of the exposure interval, accumulated photocharge within the first and second storage diodes is transferred to first and second floating diffusion nodes, respectively, as part of a correlated-double-sampling readout with respect to each of the floating diffusion nodes.