TOF Distance Measurement Using Randomized Pulses in Multi-User Sensing

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Solution Overview

Problem

Time-of-flight (TOF) systems in multi-user environments experience interference from other systems, leading to inaccurate distance measurements, which can be dangerous in applications like automated guided vehicles, and existing solutions like time-multiplexing, frequency-multiplexing, and pseudo-noise modulation are inefficient or vulnerable to malicious participants.

Innovation Solution

A method using single photon avalanche detectors (SPADs) with varied pulse repetition rates and random delays, combined with statistical analysis of time-of-arrival (TOA) distributions, allows TOF systems to distinguish their own pulses from noise and interference, without relying on central coordination or cooperation with other systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple TOF systems operate in the same environment, then the coverage and functionality of the system are improved, but interference between systems occurs leading to corrupted TOF detection

Engineering Contradiction:

Improvemulti-user environment capabilityVSAvoidTOF detection accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies periodic action by using pulse position modulation where each TOF system transmits pulses at specific periodic intervals determined by a unique code. The transmission occurs in periodic frames with each pulse positioned at predetermined time slots according to the system's assigned code, allowing multiple systems to coexist without interference while maintaining reliable TOF detection

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the temporal parameter of pulse transmission by assigning different pulse position codes to different TOF systems. Each system transmits pulses at different positions within the periodic frame, effectively using parameter variation (time position) to distinguish between multiple systems and eliminate mutual interference

Inventive Principle:

Principle #35Parameter changes

2Reliability

If time-multiplexing or frequency-multiplexing is used to reduce interference, then system coordination is improved, but a central control unit is required increasing device complexity

Engineering Contradiction:

Improveinterference reductionVSAvoidcentral coordination unit

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements self-service by having each TOF system independently determine its pulse transmission positions based on a pre-assigned unique code. Each system autonomously generates its pulse sequence without requiring real-time coordination with a central unit, eliminating the need for complex central control infrastructure while maintaining reliable interference-free operation

Inventive Principle:

Principle #25Self-service

3Object-affected harmful factors

If pseudo-noise modulation is used to handle multi-user interference, then interference resistance is improved, but the system becomes vulnerable to malicious participants

Engineering Contradiction:

Improveinterference resistanceVSAvoidvulnerability to malicious interference

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies asymmetry by assigning unique asymmetric pulse position codes to different TOF systems. Each system's code creates a distinct asymmetric pattern of pulse positions within the periodic frame, making it impossible for malicious participants to easily replicate or jam the system without detection, thereby providing both interference resistance and security against malicious actors

Inventive Principle:

Principle #4Asymmetry

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 accurate distance measurements in uncontrolled multi-user environments, immune to both unintentional and malicious interference, by ensuring non-interference through randomization and statistical processing, enhancing system robustness and efficiency.

Implementation Method 1

collecting pulses that are reflected or scattered from the environment to at least one single photon avalanche detector (SPAD)

Methodology Applied

Scientific EffectAvalanche breakdown: Avalanche Breakdown

Implementation Method 2

provides a reliable time-basis and a timestamp for a pulse detection

Methodology Applied

Scientific EffectTime-of-flight measurement: Time of Flight

Data Source

PatentEP3497477B1Method and device for measuring a distance to a target in a multi-user environment by means of at least one detector

Publication Date: 2026.03.11 FASTREE3D

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AI summary

The invention relates to a method for measuring a distance to a target in a multi-user environment by means of at least one sensor, comprising: • irradiating the environment by means of a series of radiation pulses, wherein series of radiation pulses are emitted at a determined repetition rate and with a determined random delay; • collecting pulses that are reflected or scattered from the environment to at least a detector connected to at least one chronometer; • assigning a timestamp at every detected pulse on the detector; • subtracting the added delay from every registered timestamp coming from the chronometer, the result corresponding to the time of arrival; • determining the statistical distribution of said time of arrival; • determining the distance to the target from said statistical distribution.