Range Finding Device Using Polarization Multiplexing for Simultaneous Distance Measurement

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Solution Overview

Problem

Existing range finding apparatuses using light waves often require longer measurement times and are inefficient when using multiple range finding signals, especially when the positional relationship between the apparatus and the object changes, as they cannot simultaneously perform distance measurements using multiple signals at the same time.

Innovation Solution

A range finding apparatus that generates and transmits multiple range finding signals using different methods and settings, such as quadrature modulation and polarization multiplexing, allowing for simultaneous distance computation with high accuracy and efficiency, even when the positional relationship changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If multiple range finding signals are transmitted sequentially using traditional methods, then distance measurement can be performed using different methods, but the measurement time increases and efficiency decreases

Engineering Contradiction:
Improvedistance measurement accuracyVSAvoidmeasurement time
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent combines multiple range finding signals (different frequencies and polarization states) into a single transmitted light beam. The transmission light includes both first and second range finding signals with different polarization directions, allowing simultaneous transmission of multiple signals rather than sequential transmission, thereby reducing measurement time while maintaining measurement accuracy

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces polarization dimension to multiplex multiple range finding signals. By assigning different polarization directions (first polarization direction and second polarization direction perpendicular to the first) to different signals, the system can transmit multiple signals simultaneously in the same spatial channel, effectively adding a dimension for signal differentiation and enabling parallel measurement

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Productivity

If multiple range finding signals are transmitted simultaneously using different polarization directions, then measurement time is reduced, but the device complexity increases

Engineering Contradiction:
Improvemeasurement efficiencyVSAvoidsignal processing complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent segments the received light into different polarization components using a polarization beam splitter. The received light is separated into first received light with the first polarization direction and second received light with the second polarization direction, allowing independent processing of each signal component and simplifying the overall processing architecture

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces a polarization beam splitter as an intermediary device to separate the mixed polarization components of the received light. This intermediary component facilitates the separation of first and second received light, making it easier to extract and process individual range finding signals without requiring complex direct separation methods

Inventive Principle:
Principle #24Intermediary (Mediator)

3Measurement precision

If the positional relationship between the apparatus and object changes during measurement, then measurement accuracy may deteriorate, but traditional methods cannot perform simultaneous measurements

Engineering Contradiction:
Improvedistance measurement accuracyVSAvoidadaptability to positional changes
Core Design Contradiction:
Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent enables continuous and simultaneous transmission of multiple range finding signals with different frequencies and polarization states. This continuous multi-signal transmission allows the system to capture distance information at the same moment from multiple measurement perspectives, making the measurement process robust against rapid positional changes between the apparatus and object

Inventive Principle:
Principle #20Continuity of useful 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

Enables high-accuracy distance measurement in a shorter time compared to traditional methods, and maintains accuracy even when the positional relationship between the apparatus and the object changes, by embedding multiple range finding signals in a single transmission light.

Implementation Method 1

a modulation unit that generates transmission light acquired by performing at least one of quadrature modulation and polarization modulation on an optical carrier wave

Methodology Applied
Scientific EffectQuadrature modulation: Phase Modulation

Implementation Method 2

a modulation unit that generates transmission light acquired by performing at least one of quadrature modulation and polarization modulation on an optical carrier wave

Methodology Applied
Scientific EffectPolarization modulation: Polarisation

Implementation Method 3

a transmission unit that transmits the generated transmission light

Methodology Applied
Scientific EffectLight transmission: Light

Implementation Method 4

a reception unit that receives reflection light which is light acquired in such a way that the transmission light is reflected in an object to be measured

Methodology Applied
Scientific EffectReflection: Reflection

Implementation Method 5

an extraction unit that extracts reception signals corresponding to the respective range finding signals by demodulating the reflection light

Methodology Applied
Scientific EffectDemodulation: Phase Modulation

Implementation Method 6

a computation unit that computes distances to the object to be measured using any one or more of the extracted reception signals

Methodology Applied
Scientific EffectTime-of-Flight: Time of Flight

Implementation Method 7

a frequency difference detection method (for example, a Frequency Modulated Continuous Wave (FMCW) method) for computing the distance based on a frequency difference between the transmitted light and the reflection light

Methodology Applied
Scientific EffectFrequency difference detection: Doppler Effect

Implementation Method 8

a phase difference detection method

Methodology Applied
Scientific EffectPhase difference detection: Interference

Data Source

PatentEP3726249B1Range finding device and control method
Publication Date: 2024.05.15 NEC CORP
  • EP3726249B1 patent drawingFigure 1
  • EP3726249B1 patent drawingFigure 2
  • EP3726249B1 patent drawingFigure 3

AI summary

A range finding apparatus (2000) generates a plurality of range finding signals. The range finding apparatus (2000) generates transmission light acquired by performing at least one of quadrature modulation and polarization modulation on an optical carrier wave by using each of the generated range finding signals. The range finding apparatus (2000) transmits the generated transmission light. The range finding apparatus (2000) receives reflection light which is the transmission light reflected by an object to be measured. The range finding apparatus (2000) extracts a reception signal corresponding to each of the range finding signals by demodulating the reflection light. The range finding apparatus (2000) computes a distance to the object to be measured by using any one or more of the extracted reception signals