Optical Attenuation Unit for Laser Distance Measuring Modules

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Solution Overview

Problem

Conventional distance measuring devices face challenges in achieving rapid signal amplitude setting with high dynamic range and precision, particularly when measuring objects with varying reflectivity and distance, leading to inaccurate measurements due to slow attenuation or amplification times and limited signal dynamic range.

Innovation Solution

The implementation of an optical attenuation unit in the transmitting channel of a laser distance measuring module, utilizing optically active crystals for rapid and continuous adjustment of attenuation factors, enabling signal amplitude control within nanosecond timescales and a dynamic range of at least 1000, using electro-optical, acousto-optical, or magneto-optical effects to ensure accurate distance measurements across a wide range of amplitudes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional mechanical attenuators (gray filter wheel) are used, then signal amplitude can be regulated, but the setting time is typically 1 ms or longer, which is too slow for high-speed scanning measurements

Engineering Contradiction:

Improvesignal setting speedVSAvoidmeasurement time

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The patent replaces mechanical attenuators (gray filter wheel) with electro-optical attenuators that use electro-optical effects (Pockels effect, Kerr effect) or acousto-optical effects to control signal amplitude. This substitution eliminates mechanical moving parts and achieves attenuation setting times in the nanosecond range (300-1000 ns), enabling high-speed scanning measurements at rates up to several megahertz.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If the distance measuring device covers a large distance range (less than 1 m to multiple kilometers), then it must handle varying signal amplitudes, but conventional attenuators cannot provide both high dynamic range (at least 5.0 optical density) and rapid setting

Engineering Contradiction:

Improvesignal dynamic rangeVSAvoidattenuation setting speed

Core Design Contradiction:

Adaptability or versatilityVSSpeed

Solution Approach 1:

The patent employs electro-optical or acousto-optical attenuators that can rapidly change their optical properties (transmission/attenuation) by applying different electrical or acoustic signals. This enables continuous adjustment of attenuation factors across a dynamic range of at least 5.0 optical density (100,000:1) with setting times of 300-1000 ns, simultaneously achieving both high adaptability and high speed.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If objects with glossy surfaces are measured, then signal amplitude varies greatly depending on angle of incidence, but conventional attenuators cannot regulate signal amplitude fast enough to prevent receiver overload or noise interference

Engineering Contradiction:

Improvedistance measurement accuracyVSAvoidsignal regulation speed

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The patent implements a feedback control system where the electro-optical or acousto-optical attenuator is dynamically adjusted based on the received signal amplitude. This feedback mechanism ensures that the signal amplitude entering the receiver is optimized for each measurement, preventing both noise interference (for weak signals) and receiver overload (for strong signals), thereby maintaining high measurement precision across varying surface reflectivities.

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 solution enables distance measurements with improved accuracy and robustness, supporting scan rates of up to several megahertz and operation across a large temperature range, while minimizing transit time errors and maintaining signal quality.

Implementation Method 1

The attenuation unit is designed such that the attenuation is performed by means of an optically active crystal, based on an effect from at least one of the groups of electro-optical effects, acousto-optical effects, and magneto-optical effects

Methodology Applied

Scientific EffectElectro-optical effect: Electro-Optic Effects

Implementation Method 2

Methodology Applied

Scientific EffectAcousto-optical effect: Acousto-optic Effect

Implementation Method 3

Methodology Applied

Scientific EffectMagneto-optical effect: Magneto-Optic Effects

Data Source

PatentUS10921449B2Dynamic expansion of a distance measuring device having a variable optical attenuation element in the transmitting channel

Publication Date: 2021.02.16 HEXAGON INNOVATION HUB GMBH

AI summary

A measuring device, in particular a tachymeter, laser scanner, profiler, or laser tracker, having an electronic laser distance measuring module, which comprises an optical transmitting channel having a transmitting unit and an optical receiving channel having a receiving unit for laser measuring radiation, wherein the beam guiding in the electronic laser distance measuring module is implemented by means of fiber optics, and wherein a settable attenuation unit based on an optically active crystal for attenuating the laser measuring radiation generated by the transmitting unit is provided in the optical transmitting channel.