Moiré-based distance measurement using grating interference

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Solution Overview

Problem

Current methods for measuring virtual object distances in Extended Reality (XR) applications, such as Augmented Reality (AR) and Virtual Reality (VR), are limited by small optical apertures and lack precision, leading to inaccuracies in distance perception and immersion, especially with conventional optical imaging methods and time-of-flight techniques.

Innovation Solution

A method utilizing a system with a first lens, an optical pinhole, a second lens, and a pair of gratings to form a Moiré pattern, which is then analyzed to determine object distance, allowing for precise measurement of both real and virtual distances using the properties of the gratings, including fringe shift, gap, and relative angle, independent of light source wavelength or coherence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional optical imaging methods are used with small apertures, then the device complexity is reduced, but the measurement precision deteriorates

Engineering Contradiction:

Improvedevice complexityVSAvoidmeasurement precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces a pair of gratings as an intermediary element between the optical system and the detector. These gratings create Moiré patterns that amplify the optical information, enabling precise distance measurements even with small aperture sizes. The gratings act as a mediator that transforms the limited optical input into enhanced measurement signals.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If time-of-flight techniques are used, then the measurement speed is improved, but the measurement precision deteriorates

Engineering Contradiction:

Improvemeasurement speedVSAvoidmeasurement precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent replaces the temporal measurement approach (time-of-flight) with a spatial measurement approach using Moiré patterns. Instead of measuring the time for light to travel to and from the object, the system uses the spatial frequency and orientation of Moiré fringes to determine distance, achieving both speed and precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If structured light methods are used, then the measurement precision is improved, but the device complexity increases

Engineering Contradiction:

Improvemeasurement precisionVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent changes the parameter being measured from the intensity or timing of light to the spatial frequency and orientation of Moiré patterns. By measuring the fringe spacing and angle rather than light intensity variations, the system achieves high precision with a simpler optical setup that doesn't require complex structured light projection systems.

Inventive Principle:

Principle #35Parameter changes

4Measurement precision

If laser methods are used, then the measurement precision is improved, but the use of energy increases

Engineering Contradiction:

Improvemeasurement precisionVSAvoiduse of energy

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces expensive, high-energy laser systems with inexpensive, low-energy LED or other standard light sources. The Moiré grating method is so sensitive that it can achieve high precision measurements using very weak light sources, eliminating the need for high-power lasers and their associated energy consumption and safety requirements.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 provides highly accurate and sensitive distance measurements, capable of handling small apertures and long distances, enhancing user immersion by ensuring precise virtual distance calculations in XR applications, and is insensitive to light source properties, offering a compact and vibration-resistant solution.

Implementation Method 1

A detector is configured for receiving a Moiré pattern formed as a result of light from the DUT being disposed through the first lens, the optical pinhole, the second lens and the pair of gratings

Methodology Applied

Scientific EffectMoiré effect: Moiré Effect

Implementation Method 2

an optical pinhole disposed between the first lens and the second lens

Methodology Applied

Scientific EffectPinhole camera principle: Spatial Filter

Data Source

PatentUS11821755B1Moiré-based distance measurement method

Publication Date: 2023.11.21 ML OPTIC CORP

AI summary

A method for providing an object distance of a device under test (DUT) using a system including a first lens, a second lens, an optical pinhole disposed between the first lens and the second lens, a detector, a pair of gratings disposed between the second lens and the detector, the detector configured for receiving a Moiré pattern formed as a result of light from of the DUT being disposed through the first lens, the optical pinhole, the second lens and the pair of gratings, the method including obtaining the Moiré pattern using the detector and determining the object distance based on the Moiré pattern and one or more properties of the pair of gratings.