Laser Diode Interferometer Source for Compact Laser Tracker

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Solution Overview

Problem

Current laser trackers face challenges with the size and energy consumption of HeNe gas lasers, which hinder miniaturization and increase costs due to high-voltage requirements and sensitivity to magnetic fields, while also limiting the service life of these light sources.

Innovation Solution

The use of a laser diode with a large coherence length, integrated with an interferometer, which eliminates the need for high-voltage supplies and reduces energy consumption, allowing for a more compact design with a longitudinally monomode measurement radiation source capable of achieving the required precision for industrial surveying over long ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If HeNe gas lasers are used in laser trackers, then large coherence length and measurement range are achieved, but device size increases and miniaturization is hindered

Engineering Contradiction:
Improvecoherence lengthVSAvoiddevice size
Core Design Contradiction:
Measurement precisionVSVolume of moving object

Solution Approach 1:

The patent changes the fundamental parameter of the light source from HeNe gas laser to laser diode. By adjusting the coherence length parameter of the laser diode (achieving at least 10 meters), the system maintains the required measurement precision while dramatically reducing device size and enabling miniaturization.

Inventive Principle:
Principle #35Parameter changes

2Measurement precision

If HeNe gas lasers are used in laser trackers, then measurement range is achieved, but energy consumption increases and high-voltage supplies are required

Engineering Contradiction:
Improvemeasurement rangeVSAvoidenergy consumption
Core Design Contradiction:
Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent changes the power supply parameter from high-voltage supply (requiring thousands of volts) to low-voltage supply (standard electrical voltages). The laser diode operates with conventional electrical voltages, dramatically reducing energy consumption and eliminating the need for complex high-voltage power supply systems while maintaining the required measurement range.

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If HeNe gas lasers are used in laser trackers, then measurement capability is achieved, but reliability decreases due to sensitivity to magnetic fields and limited service life

Engineering Contradiction:
Improvemeasurement capabilityVSAvoidservice life
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent changes the physical and operational parameters of the light source from HeNe gas laser to laser diode. The laser diode exhibits superior reliability by being insensitive to magnetic fields and having a significantly extended service life, while maintaining the required measurement capability through appropriate coherence length selection.

Inventive Principle:
Principle #35Parameter changes

4Measurement precision

If HeNe gas lasers are used in laser trackers, then measurement function is achieved, but device complexity increases due to high-voltage supply requirements

Engineering Contradiction:
Improvemeasurement functionVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent changes the electrical operating parameters from high-voltage requirement to low-voltage operation. This simplifies the power supply system, reduces the number of high-voltage components, and lowers device complexity while maintaining the essential measurement function through the laser diode's appropriate coherence length.

Inventive Principle:
Principle #35Parameter changes

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 provides a compact, energy-efficient laser tracker with a coherence length of at least 10 meters, enabling precise distance measurement over large ranges with reduced space and energy requirements, and eliminates the need for high-voltage supplies, enhancing the overall performance and reliability of the device.

Implementation Method 1

an interferometer laser beam source (20) designed as a laser diode, with the laser diode also designed in such a way that the measurement radiation can be generated longitudinally monomode with a defined emission wavelength and with a coherence length of at least 10 m

Methodology Applied
Scientific EffectLaser: Laser

Implementation Method 2

a distance measuring unit designed as an interferometer (10) for determining a change in distance to the target by means of interferometry

Methodology Applied
Scientific EffectInterference: Interference

Data Source

PatentEP2773980B1Laser diode as interferometer laserbeam source in a laser tracker
Publication Date: 2019.06.26 LEICA GEOSYSTEMS AG
  • EP2773980B1 patent drawingFigure 1~2
  • EP2773980B1 patent drawingFigure 3~4
  • EP2773980B1 patent drawingFigure 5~6

AI summary

Laser tracker (70) for continuous tracking of a reflecting target and for determining the distance to the target, said laser tracker having a base defining a standing axis, a beam steering unit for emission of a measuring radiation and for receiving at least a part of the measuring radiation reflected by the target, wherein the beam steering unit is motorized to be pivotable relative to the base around the standing axis and a tilt axis extending substantially orthogonal to the standing axis. Furthermore, the tracker has a distance measuring unit (10) configured as an interferometer (10) for determining a change in distance to the target by means of interferometry, an interferometer laser beam source (20) for generating the measuring radiation for the interferometer (10) and an angle measurement functionality for determining an alignment of the beam steering unit relative to the base. The interferometer laser beam source (20) is configured as a laser diode (20), and the laser diode (20) is further so configured that the measuring radiation can be generated monomodally in the longitudinal direction and has a defined emission wavelength and a coherence length of at least 10 m.