Time-of-Flight Pixel Tap Segmentation for Depth Accuracy

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Time-of-Flight (ToF) systems face challenges in measuring non-biased distances due to the limited number of taps per pixel, leading to inconsistent depth calculations, increased system size, and high bandwidth requirements, as well as motion-induced corruption of depth data.

Innovation Solution

A method and system where each pixel comprises at least two pairs of taps, operated at a 50% duty cycle during a predetermined number of modulated signal cycles, allowing for simultaneous detection of correlation measurements and reducing the need for memory storage, thereby minimizing system size and bandwidth requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If only one or two taps per pixel are used, then device complexity is reduced, but measurement precision and reliability of depth calculation deteriorate due to time-sequential measurement and motion-induced corruption

Engineering Contradiction:

Improvenumber of taps per pixelVSAvoiddepth calculation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The pixel is divided into multiple taps (at least two pairs of taps), where each tap independently measures the modulated signal during specific time intervals. This segmentation allows simultaneous measurement of multiple signal samples within a single modulation period, enabling accurate depth calculation without requiring multiple sequential exposures, thereby eliminating motion-induced corruption while maintaining manageable device complexity.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If multiple distinct signals are measured sequentially with several exposures, then measurement precision improves, but loss of time increases and motion corruption occurs

Engineering Contradiction:

Improvedepth measurement accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Multiple taps operate simultaneously and continuously within a single modulation period, each capturing signal samples during their designated time intervals. This continuous parallel measurement eliminates the need for multiple sequential exposures, reducing measurement time and preventing motion-induced depth corruption while maintaining high measurement precision through correlated analysis of all tap signals.

Inventive Principle:

Principle #20Continuity of useful action

3Measurement precision

If several taps per pixel are used, then measurement precision improves, but device complexity and system size increase due to memory requirements

Engineering Contradiction:

Improvedepth calculation consistencyVSAvoidmemory storage requirements

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Multiple taps are integrated within a single pixel structure, sharing common circuitry and processing resources. The signals from all taps are correlated together in real-time to calculate depth, eliminating the need for separate memory storage for each tap's signal. This merging approach maintains high measurement precision through consistent depth calculation while minimizing device complexity and memory requirements.

Inventive Principle:

Principle #5Merging (Combining)

4Measurement precision

If multiple taps operate with high bandwidth requirements, then measurement precision improves, but use of energy and system complexity increase

Engineering Contradiction:

Improvedistance measurement accuracyVSAvoidbandwidth energy consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

Each tap is activated during specific time intervals corresponding to different phases of the modulation period, creating a periodic measurement pattern. This time-division multiplexing approach allows multiple taps to operate with reduced individual bandwidth requirements while maintaining overall high measurement precision through the combined correlation analysis of all periodic tap signals within each modulation cycle.

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

This approach enhances motion robustness and accuracy of distance measurements while reducing the size and bandwidth needs of ToF systems, enabling more precise and efficient operation.

Implementation Method 1

a lens collects the reflected light 17 and forms an image of objects in the scene on an imaging sensor 35

Methodology Applied

Scientific EffectPhotodetection: Photoelectric Effect

Implementation Method 2

Time-Of-Flight (ToF) systems, including a camera and data processing means, appeared recently and are capable of capturing 3-D images of a scene by analysing the time of flight of light from a light source to an object

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS10509126B2Method for driving a time-of-flight system

Publication Date: 2019.12.17 SONY DEPTHSENSING SOLUTIONS SA NV

AI summary

The present invention relates to a method for driving a Time-of-Flight system for use with an illumination system being adapted to illuminate a scene with a modulated signal, the ToF system having an imaging sensor comprising at least one pixel, said pixel comprising taps driven by driving signals for detecting the modulated signal reflected from the scene, the method comprising, for each pixel, the steps of determining at least a first and a second pair of taps and driving each pair of taps to detect the reflected modulated signal during a predetermined number N of cycles of the modulated signal.