Laser Distance Sensor with Variable Coincidence Time

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Solution Overview

Problem

Existing laser measuring systems using the time-of-flight method face challenges in distinguishing the reflected laser pulse from background light, especially at larger distances, leading to decreased measurement quality due to increased background light interference.

Innovation Solution

The implementation of a laser measuring system that includes a pulse laser, an optical sensor with a detection unit capable of detecting individual photons, a coincidence recognition stage, and a coincidence time presetting stage that monotonically increases during the measuring cycle, allowing for improved detection of the reflected laser pulse by varying the coincidence time based on background light conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the measurement distance increases or background light intensity increases, then the reflected laser pulse becomes increasingly difficult to distinguish from background light, but the measurement quality decreases

Engineering Contradiction:

Improvedistance measurement qualityVSAvoidbackground light interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The coincidence time window is made variable rather than fixed, dynamically adapting its width based on the specific measurement conditions and distance being measured. This allows the system to optimize signal detection for each measurement scenario, improving the ability to distinguish reflected laser pulses from background light at varying distances.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the parameter of coincidence time window width to optimize detection. By adjusting this parameter according to measurement distance and background conditions, the system maintains high measurement quality across different operating conditions, effectively counteracting background light interference.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a fixed coincidence time window is used for detecting reflected laser pulses, then the detection process is simple, but the measurement accuracy decreases at larger distances

Engineering Contradiction:

Improvedistance measurement accuracyVSAvoidsignal evaluation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses feedback from the measurement process itself to adjust the coincidence time window. By monitoring detection results and measurement conditions, the system automatically optimizes the time window parameter, maintaining high accuracy without requiring complex manual intervention.

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 enhances measurement accuracy at larger distances and in bright background light conditions by adapting signal evaluation sensitivity, reducing the impact of background interference and maintaining precision in close-range measurements.

Implementation Method 1

an optical sensor including at least one detection unit for generating detection signals, the detection unit including at least one detector for detecting individual photons

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

the time of flight (travel time) of a laser pulse emitted from an active radiation source and reflected by the object to be measured is measured

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Data Source

PatentUS11536835B2Laser measuring means for measuring a distance from an object, and method of operating same

Publication Date: 2022.12.27 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

A laser measuring set for measuring a distance from an object includes a pulse laser for emitting a laser pulse at the beginning of a measuring cycle; an optical sensor having at least one detection unit for generating detection signals; a coincidence recognition stage for generating coincidence signals, wherein during the measuring cycle, one of the coincidence signals is generated each time the detection signals generated by the detection unit reach at least a preset coincidence depth within a coincidence time; a coincidence time presetting stage for presetting the coincidence time for the coincidence recognition stage, the coincidence time presetting stage being configured such that the coincidence time monotonically increases during the measuring cycle; and travel-time measuring set for determining the distance on the basis of a travel-time measurement of the coincidence signals.