Laser Diode TEC Module for Compact Interferometer in Laser Tracker
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Solution Overview
Problem
Laser trackers using HeNe gas lasers face challenges with size, power consumption, high voltage requirements, sensitivity to magnetic fields, and limited service life, which hinder miniaturization and practicality in industrial metrology.
Innovation Solution
Integration of a laser diode into a thermo-electrically temperature-stabilized cell (TEC cell) with a collimation optical unit, optical mini-isolator, and polarization-retaining fiber coupling for the interferometer, allowing for compact and efficient generation of longitudinally variable laser radiation within a specific wavelength range, reducing the need for active beam direction control and optimizing space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HeNe gas laser is used as light source in interferometer, then measurement range and coherence length are improved, but device size and power consumption increase
Solution Approach 1:
The patent changes the fundamental parameters of the light source by replacing HeNe gas laser with laser diode, operating at different wavelength (635nm vs typical HeNe 632.8nm) with different coherence mechanisms. This parameter change enables compact size while maintaining sufficient coherence length for industrial measurement ranges through optimized laser diode cavity design and feedback mechanisms
Solution Approach 2:
The patent substitutes the mechanical/optical complexity of HeNe gas laser system with a solid-state laser diode system. This replacement eliminates the need for gas-filled tubes, high-voltage power supplies, and complex optical alignment mechanisms, achieving miniaturization while maintaining measurement capability through integrated laser diode modules with built-in collimation optics
2Stability of the object's composition
If HeNe gas laser is used as light source, then coherence length is improved, but power consumption and high voltage requirements increase
Solution Approach 1:
The patent changes the operating parameters from high-voltage gas discharge (HeNe requiring 1500-2000V) to low-voltage electric current injection for laser diode operation. This parameter change reduces power consumption from typical HeNe laser 1-2W to laser diode 0.1-0.5W while maintaining coherence length through optimized current injection and temperature control of the laser diode active region
Solution Approach 2:
The patent replaces the high-voltage electrical system required for HeNe laser operation with a low-voltage current control system for laser diode. This substitution eliminates high-voltage power supplies and associated safety requirements, reducing both power consumption and system complexity through integrated laser diode driver circuits with precision current regulation
3Measurement precision
If HeNe gas laser is used, then measurement precision is improved, but service life is reduced
Solution Approach 1:
The patent adopts the philosophy of using solid-state laser diodes with finite but extended service life (typically 10,000-50,000 hours) compared to HeNe lasers (15,000-20,000 hours). The laser diode is designed as a consumable component that can be easily replaced, with lower cost and simpler replacement procedures, maintaining measurement precision throughout its operational lifetime through temperature stabilization and current control
4Measurement precision
If HeNe gas laser is used, then measurement precision is improved, but sensitivity to magnetic fields increases
Solution Approach 1:
The patent replaces the HeNe gas discharge tube with a solid-state laser diode, fundamentally changing the physical mechanism from gas plasma to semiconductor electroluminescence. This substitution eliminates the magnetic field sensitivity inherent in gas discharge processes and electron beam deflection, as laser diode operation is based on electrical current injection and recombination in a solid semiconductor structure that is inherently resistant to magnetic field interference
5Volume of moving object
If laser diode is integrated into TEC cell with collimation optics and fiber coupling, then device compactness is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges multiple functional components (laser diode, collimation optics, fiber coupling, temperature control) into a single integrated laser source module housed in a TEC cell. This consolidation reduces the overall number of discrete components and alignment requirements at the system level, simplifying installation and maintenance despite the increased manufacturing precision required for the integrated module itself
Solution Approach 2:
The patent implements a nested structure where the laser diode is mounted within the TEC cell, collimation optics are positioned around the laser diode output, and fiber coupling elements are integrated into the same housing. This nested arrangement allows compact packaging of multiple functions in a small volume, with each component optimized for its specific function while maintaining overall system compactness
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 enables a more compact and efficient laser tracker with reduced mechanical and electronic expenditure, maintaining precision for distance determination up to 10 meters with lower space requirements and reduced power consumption, while ensuring stable wavelength and coupling efficiency.
Implementation Method 1
a laser beam source, which is configured as a laser diode, for generating measuring radiation for the interferometer
Implementation Method 2
the laser beam source is integrated into a thermo-electrically temperature-stabilized cell, referred to as a TEC cell hereafter
Implementation Method 3
a collimation optical unit
Implementation Method 4
a distance measuring unit, which is configured as an interferometer, for determining a distance change to the target by means of interferometry
Data Source
AI summary
Some embodiments of the invention relate to a laser tracker for progressive tracking of a reflective target and for determining the distance to the target having a distance measuring unit, which is designed as an interferometer, for determining a distance change to the target by means of interferometry, a laser beam source for generating measuring radiation for the interferometer, a base, which defines a standing axis, a beam guiding unit for emitting the measuring radiation and for receiving at least a part of the measuring radiation reflected on the target, wherein the beam guiding unit is pivotable by a motor about the standing axis and an inclination axis, which is essentially orthogonal in relation to the standing axis, in relation to the base, and an angle measuring functionality for determining an alignment of the beam guiding unit in relation to the base.