Structured Light Projection Wavefront Aberration Artifact Suppression

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Solution Overview

Problem

Triangulation devices using structured light projection suffer from visual artifacts due to circuitry or micromirror artifacts, which can lead to incorrect 3D information calculation, especially in areas with strong pixel intensity gradients.

Innovation Solution

A triangulation device with a projector lens system that introduces wavefront aberration, specifically a primary spherical aberration coefficient Z9 larger than one-fourth of the wavelength, to separate and suppress artifact patterns from structured light patterns, ensuring accurate 3D information capture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a lens system with high resolution is used to project structured light patterns, then the projected image quality is improved, but visual artifacts from circuitry or micromirror regions become more prominent and interfere with measurement accuracy

Engineering Contradiction:

Improveprojected image qualityVSAvoidvisual artifacts

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by deliberately introducing wavefront aberration (specifically spherical aberration with coefficient Z9 > λ/4) into the lens system. This optical parameter modification transforms the lens behavior to suppress high-frequency artifact patterns while preserving the structured light pattern, thereby reducing visual artifacts without sacrificing projection quality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of the lens system's inherent aberrations into a beneficial filtering mechanism. By ensuring the lens exhibits spherical aberration greater than λ/4, the system automatically dampens artifact patterns (which have high spatial frequencies) while maintaining the integrity of the projected structured light pattern, thus turning a potential defect into a useful artifact suppression mechanism

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Ease of manufacture

If circuitry or micromirror artifacts are present between neighboring pixel elements, then the projector can be manufactured with standard processes, but the local intensity centroid is displaced leading to incorrect 3D information calculation

Engineering Contradiction:

Improveprojector manufacturingVSAvoid3D information accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent introduces wavefront aberration as an intermediary optical mechanism that acts as a spatial filter. This intermediary suppresses the harmful artifact patterns generated by circuitry or micromirror regions before they reach the measurement object and camera, thereby protecting measurement precision without affecting the manufacturing process

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

By changing the optical parameter (wavefront aberration coefficient Z9) to be greater than λ/4, the system creates a selective filtering effect that dampens high-frequency artifact patterns while preserving the structured light pattern, thus maintaining both ease of manufacture and measurement precision

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

The solution effectively reduces visual artifacts, allowing for precise 3D measurement by maintaining high Modulation Transfer Function (MTF) contrast at structured light pattern frequencies while damping artifact patterns, thereby improving the accuracy of distance information extraction.

Implementation Method 1

the lens system is arranged so that the projection light passing through the lens system defines a wavefront with a wavefront aberration from a spherical reference wavefront

Methodology Applied

Scientific EffectWavefront aberration:

Implementation Method 2

the wavefront aberration is defined, in particularly dominated, by a primary spherical aberration coefficient Z9 of a Zernike decomposition, wherein the primary spherical aberration coefficient Z9 is larger than one fourth of the wavelength λ

Methodology Applied

Scientific EffectSpherical aberration:

Data Source

PatentUS12025470B2Structured light projection through the minimization of visual artifacts by way of deliberately introduced optical aberrations

Publication Date: 2024.07.02 HEXAGON INNOVATION HUB GMBH

AI summary

A triangulation device for measuring a measurement object by a projection of a structured light pattern onto the measurement object. The triangulation device includes a projector projecting the structured light pattern decomposable into different spatial frequencies onto the measurement object. The projector comprises a matrix of pixel elements and a lens system which determines a wavefront with a wavefront aberration from a reference wavefront, and a camera including a lens system and an imaging sensor, the camera being configured to receive the structured light pattern projected by the projector onto the measurement object, and a processing unit configured to provide distance information by evaluating imaging information provided by the camera. The wavefront aberration comprises a primary spherical aberration coefficient Z9, wherein the primary spherical aberration coefficient Z9 is larger than 0.5λ, wherein λ is a wavelength of the projected structured light pattern.