Switchable Aperture Array for Adaptive Laser Distance Measurement

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Solution Overview

Problem

Existing optical distance measurement devices face challenges with stability, accuracy, and extraneous light interference when measuring distances to reflective target objects, particularly due to the need for multiple beam paths and diverging optics, which increase space requirements and measurement errors.

Innovation Solution

A device with a laser beam shaping element featuring a transmission aperture arrangement of switchable transmission pixels, allowing for adaptive beam shaping and attenuation to suit individual retroreflectors and surface retroreflectors, and a receiving beam shaping element for reducing radiation power and attenuating extraneous light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple beam paths and beam-shaping optics are used to generate different beam divergences, then adaptability to different target objects is improved, but device complexity and space requirements increase

Engineering Contradiction:
Improveadaptability to different target objectsVSAvoiddevice complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent uses a dynamically adjustable beam-shaping element (such as a deformable mirror or liquid crystal variable focus lens) that can change its optical properties in real-time to adapt to different target objects. This single dynamic element replaces multiple static beam paths and optics, achieving adaptability while reducing device complexity and space requirements.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The invention employs a universal beam-shaping system that can perform multiple functions (adjusting beam divergence, focusing, and shaping) through a single integrated optical element or element array. This multi-functional approach eliminates the need for separate beam paths and multiple specialized optics, thereby reducing overall device complexity while maintaining versatility.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If diverging optics are used to expand the laser beam, then adaptability to different distance ranges is improved, but measurement precision deteriorates due to increased sensitivity to target object orientation

Engineering Contradiction:
Improveadaptability to different distance rangesVSAvoidmeasurement precision
Core Design Contradiction:
Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent employs dynamically adjustable beam-shaping elements that can adapt their divergence characteristics in real-time based on the measured or estimated distance to the target. This dynamic adjustment allows the system to maintain optimal beam characteristics for each distance range while minimizing sensitivity to target orientation, thereby preserving measurement precision across all ranges.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The invention changes the optical parameters (beam divergence, focal length) of the beam-shaping elements based on the operating conditions (distance to target). By adjusting these parameters dynamically or selecting from multiple preset configurations, the system achieves adaptability to different distance ranges while maintaining measurement precision through optimized beam characteristics for each range.

Inventive Principle:
Principle #35Parameter changes

3Adaptability or versatility

If the laser beam diameter is increased to cover larger target areas, then adaptability to surface retroreflectors is improved, but alignment precision requirements worsen

Engineering Contradiction:
Improveadaptability to surface retroreflectorsVSAvoidalignment precision
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent uses dynamically controllable beam-shaping elements that can adjust the beam diameter and spatial distribution adaptively. For surface retroreflectors, the system increases the effective beam coverage area while maintaining precise alignment through real-time adjustment of the beam profile, thereby achieving both adaptability and alignment precision.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The invention applies local quality variations within the beam profile by using spatially selective beam-shaping elements (such as spatial light modulators or segmented aperture arrays). This allows different regions of the beam to have different characteristics (e.g., higher intensity at the center for precision, extended wings for coverage), achieving both adaptability to larger targets and maintained alignment precision through localized optimization.

Inventive Principle:
Principle #3Local quality

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

The solution enhances measurement accuracy and stability by reducing the precision required for aligning the laser beam and effectively managing extraneous light, while minimizing equipment complexity and space requirements.

Implementation Method 1

a laser beam shaping element (35) with a transmission aperture arrangement (83-96)

Methodology Applied
Scientific EffectDiffraction: Diffraction

Implementation Method 2

measuring distances to individual retroreflectors (51, 61) and to surface retroreflectors

Methodology Applied
Scientific EffectRetroreflection: Retroreflector

Implementation Method 3

a detector (15) that receives a received beam (28) reflected at the target object (28)

Methodology Applied
Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentEP3298428B1Device for optically measuring the distance to a reflective target object
Publication Date: 2024.05.08 HILTI AG
  • EP3298428B1 patent drawingFigure 1
  • EP3298428B1 patent drawingFigure 2A~3
  • EP3298428B1 patent drawingFigure 4

AI summary

The invention relates to a device for optically measuring the distance from a reflective target object, comprising a beam source, a detector, a beam-shaping system having an optical transmission system and an optical receiving system, and a laser beam-shaping element which can be arranged in the optical path of the laser beam. The laser beam-shaping element is in the form of a transmission aperture arrangement having a first array (71) of transmission pixels (72ij), said transmission pixels (72ij) being switchable, by means of a first control unit (73), between a transmission state (TSij< 10%) that is impenetrable to the laser beam, and a transmission state (10%<TSij <100%) which is at least partially penetrable to said laser beam.