Optical Time-of-Flight Sensor Phase Sequence Randomization

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Solution Overview

Problem

Optical time-of-flight sensors used in safety-critical applications require high reliability in determining distance values, but existing methods may fail to detect malfunctions promptly, affecting the accuracy and safety of the data supplied.

Innovation Solution

The method involves emitting modulated illumination light and acquiring reflected light to determine phase shifts, with a variable sequence of modulation phases and frequencies in micro-frames within each frame, allowing for continuous verification and rapid detection of malfunctions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fixed sequence of modulation phases is used in time-of-flight measurements, then the measurement process is simple and deterministic, but malfunction detection is delayed and reliability is reduced

Engineering Contradiction:

Improvereliability of distance value determinationVSAvoidcomplexity of measurement sequence control

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies the dynamics principle by making the sequence of modulation phases variable rather than fixed. The control unit randomly selects the sequence of modulation phases for different micro-frames, allowing the measurement system to adapt its behavior dynamically. This randomness enables malfunction detection because any deviation from the expected random sequence immediately indicates a system fault, thereby improving reliability without requiring complex additional hardware.

Inventive Principle:

Principle #15Dynamics

2Reliability

If multiple measurement repetitions are performed to improve reliability, then the accuracy and reliability of distance values increase, but the measurement time and processing complexity increase

Engineering Contradiction:

Improvereliability of distance value determinationVSAvoidmeasurement time for distance determination

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements feedback by using the sequence of modulation phases itself as a verification mechanism. The received signals are evaluated not only for distance information but also for consistency with the transmitted modulation phase sequence. This feedback loop allows the system to verify proper functioning in real-time during the measurement process, enabling reliable operation with fewer measurement repetitions and thus reducing measurement time while maintaining high reliability.

Inventive Principle:

Principle #23Feedback

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 significantly enhances the reliability of distance value determination by enabling quick detection of signal deviations, ensuring the proper functioning of optical time-of-flight sensors in safety-critical applications.

Implementation Method 1

These cameras are based on the known ToF (time-of-flight) measuring principle, with which not only an image with the reflected intensity and/or color of the pixels is determined for a number of pixels, but also distance values using the time-of-flight method

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Implementation Method 2

the received signal is evaluated by determination of a phase shift between the illumination light and the reflected light, so that an output signal with at least one distance value is generated

Methodology Applied

Scientific EffectPhase shift:

Data Source

PatentUS20250052899A1Reliable optical transit time method for determining distance values

Publication Date: 2025.02.13 K A SCHMERSAL HLDG

AI summary

In a method and an optical time-of-flight sensor for determining distance values d, di by an optical time-of-flight method, an illumination light 40 is emitted which is modulated with a modulation frequency f and a modulation phase q. Reflected light 42 is acquired as an output signal Rx and evaluated by acquisition of a phase shift δ between the illumination light 40 and the reflected light 42, so that an output signal d, di with at least one distance value d is generated. Distance values d, di are determined for a sequence of successive frames, with a plurality of acquisitions being made in each frame in the form of micro-frames μF1-μF8 with different modulation phases φ. A sequence of modulation phases φ1-φ4 of the micro-frames μF1-μF8 is specified for each frame. In order to achieve a particularly high reliability of the data supplied, the order of the modulation phases φ1-φ4 changes. A self-calibration and self-verification take place in an initialization step (60). The subsequent data acquisition takes place in frame acquisition steps 62 with acquisition of signals and calculation and output of the distance values for each pixel for subsequent processing (68). Each step (62) in the acquisition of a frame is divided into a setup step (64) and a subsequent acquisition of signals in micro-frames μF1-μF8. In setup step (64), the central processing unit MCU calculates (pseudo-)random numbers and uses these to determine the order of the micro-frames μF1-μF8, i.e. the respective modulation frequencies f and phase angles φ. Optical time-of-flight methods, in which the acquisition and signal evaluation are carried out with a variable order of modulation phases, are thus particularly suitable for safety-related applications, e.g. as optical area monitoring systems for industrial production facilities.