TOF Assisted Structured Light Phase Unwrapping

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Solution Overview

Problem

Time-of-flight (TOF) depth sensors and triangulation-based depth techniques face challenges in achieving real-time high-precision depth mapping due to inherent structural noise and quadratic error increase with depth, respectively, limiting their effectiveness in dynamic scenes.

Innovation Solution

Combining a TOF sensor with a projector and camera in a structured light imaging system to capture high-frequency phase-shifted structured light images and generate concurrent TOF depth images for phase unwrapping, thereby enhancing depth map accuracy and reducing errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If TOF depth sensors are used for real-time depth imaging, then real-time performance is achieved, but measurement precision deteriorates due to inherent structural noise

Engineering Contradiction:

Improvereal-time depth imaging speedVSAvoiddepth measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent combines TOF depth sensing with structured light imaging systems, merging the real-time capability of TOF sensors with the high precision of triangulation-based structured light methods. The system integrates both sensing modalities to produce depth maps that benefit from both real-time performance and high measurement precision.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses the TOF depth image as an intermediary to assist phase unwrapping in structured light imaging. The TOF depth information serves as a guide to resolve phase ambiguities in the structured light system, improving overall measurement precision while maintaining real-time performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If phase shifting structured light imaging is used to achieve high accuracy depth calculations, then measurement precision is improved, but productivity deteriorates due to multiple image capture requirements

Engineering Contradiction:

Improvedepth calculation accuracyVSAvoidreal-time depth imaging speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent performs preliminary phase shifting measurements to obtain wrapped phase information, then uses TOF depth images to guide the phase unwrapping process. This preliminary action captures essential depth information that can be rapidly processed using the TOF guidance, avoiding the need for multiple sequential image captures while maintaining high accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The TOF depth image acts as an intermediary that bridges the gap between phase-shifted structured light measurements and final depth reconstruction. It provides continuous depth information that guides the interpretation of discrete phase-shifted images, enabling high-precision depth calculation without requiring multiple sequential captures.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If triangulation-based depth techniques are used, then measurement precision is improved in static scenes, but reliability deteriorates due to quadratic error increase with depth

Engineering Contradiction:

Improvedepth measurement accuracyVSAvoiderror consistency across depth ranges

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the operational parameters of the depth sensing system by combining triangulation-based structured light imaging with TOF sensing. This hybrid approach allows the system to maintain high measurement precision for nearby objects while using TOF guidance to ensure reliability for distant objects where triangulation errors would otherwise increase quadratically.

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

Enables real-time high-precision depth mapping with reduced errors, as the TOF sensor's bounded error and complementary advantages with triangulation-based systems improve the accuracy and reliability of phase unwrapping in dynamic scenes.

Implementation Method 1

generating, concurrently with the capturing of the plurality of high frequency phase-shifted structured light images, a time-of-flight (TOF) depth image of the scene using the TOF sensor

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Implementation Method 2

capturing a plurality of high frequency phase-shifted structured light images of the scene

Methodology Applied

Scientific EffectLight modulation: Phase Modulation

Data Source

PatentUS11867500B2Time-of-flight (TOF) assisted structured light imaging

Publication Date: 2024.01.09 TEXAS INSTRUMENTS INC

AI summary

A method for computing a depth map of a scene in a structured light imaging system including a time-of-flight (TOF) sensor and a projector is provided that includes capturing a plurality of high frequency phase-shifted structured light images of the scene using a camera in the structured light imaging system, generating, concurrently with the capturing of the plurality of high frequency phase-shifted structured light images, a time-of-flight (TOF) depth image of the scene using the TOF sensor, and computing the depth map from the plurality of high frequency phase-shifted structured light images wherein the TOF depth image is used for phase unwrapping.