TEC-Stabilized Laser Diode Module for Compact Interferometric Tracking
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Solution Overview
Problem
Laser trackers face challenges with the size, power consumption, and high-voltage requirements of HeNe gas lasers, which limit miniaturization and increase complexity, while laser diodes offer compactness and low power consumption but require complex stabilization and control to maintain coherence and alignment.
Innovation Solution
A laser tracker with a thermo-electrically temperature-stabilized cell housing a laser diode, collimation optics, and polarization-maintaining fiber coupling, which stabilizes the emission wavelength and ensures efficient coupling into optical fibers, reducing the need for active beam direction control and minimizing space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HeNe gas lasers are used as light sources, then long coherence length and measurement range are achieved, but device size and power consumption increase significantly
Solution Approach 1:
The patent changes the fundamental parameters of the laser source by transitioning from HeNe gas laser to laser diode technology, operating at different wavelengths (780nm, 850nm, or 905nm) with different physical characteristics. This parameter change enables achieving sufficient coherence length for interferometric measurements while dramatically reducing device volume and power consumption.
Solution Approach 2:
The patent replaces the mechanical/optical system of HeNe gas lasers with a semiconductor-based laser diode system. This substitution eliminates the need for bulky gas discharge tubes, high-voltage power supplies, and complex optical alignment mechanisms, achieving compactness while maintaining measurement capability through integrated stabilization systems.
2Measurement precision
If HeNe gas lasers are used as light sources, then long coherence length is achieved, but device complexity and power consumption increase
Solution Approach 1:
The patent merges multiple functions into the laser diode system: the laser diode itself provides the light source, integrated collimation optics shape the beam, TEC modules provide temperature stabilization, and fiber optic coupling directs the beam. This consolidation eliminates separate high-voltage power supplies, gas discharge mechanisms, and complex alignment systems required by HeNe lasers, reducing overall device complexity.
Solution Approach 2:
The laser diode system incorporates self-stabilization through integrated TEC temperature control and collimation optics that automatically maintain beam quality. The system requires minimal external adjustment or complex control mechanisms, operating autonomously with simple current and temperature regulation compared to the complex high-voltage and optical alignment requirements of HeNe lasers.
3Volume of moving object
If laser diodes are used as light sources, then device size and power consumption are reduced, but wavelength stability and beam alignment become more challenging
Solution Approach 1:
The patent implements active feedback control through TEC (thermo-electric cooler) modules that continuously monitor and adjust the laser diode temperature to maintain stable emission wavelength. This closed-loop temperature stabilization compensates for thermal drift and ensures consistent interferometric measurement performance, addressing the wavelength stability challenge of compact laser diode systems.
Solution Approach 2:
The patent carefully controls the operating parameters of the laser diode, including injection current and temperature, to maintain single-mode operation and stable wavelength emission. By optimizing these parameters, the system achieves sufficient coherence length for interferometric measurements despite the inherently shorter coherence of laser diodes compared to HeNe lasers.
4Volume of moving object
If laser diodes are used as light sources, then device size and power consumption are reduced, but beam coupling and alignment complexity increase
Solution Approach 1:
The patent integrates collimation optics directly with the laser diode chip, creating a compact module that emits well-collimated beams without requiring separate alignment components. The integrated design combines the laser diode, collimation lens, and fiber optic coupling in a single compact assembly, eliminating the need for complex external alignment mechanisms while maintaining efficient beam coupling.
Solution Approach 2:
The patent replaces complex mechanical alignment systems with fiber optic coupling technology. The laser diode beam is directly coupled into optical fibers through integrated gratings or lens systems, which automatically maintain alignment through the flexibility and positioning capabilities of fiber optics, eliminating the need for precision mechanical mounts and adjustment mechanisms.
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 provides a compact, low-power laser tracker with stable wavelength and efficient measurement capabilities, enabling precise distance determination over a range of at least 10 meters with reduced mechanical and electronic complexity.
Implementation Method 1
a laser beam source designed as a laser diode in a thermo-electrically temperature-stabilized cell, hereinafter referred to as a TEC cell
Implementation Method 2
a laser beam source designed as a laser diode for generating a measurement beam for the interferometer
Implementation Method 3
collimation optics, an optical mini-isolator unit, and at least one polarization-preserving fiber coupling for the measurement radiation
Implementation Method 4
at least one polarization-preserving fiber coupling for the measurement radiation for the interferometer
Data Source
Figure 1~2
Figure 3a~3b
Figure 4a~4b
AI summary
The invention relates to a laser tracker (1) for continuously tracking a reflecting target and for determining the distance to the target, with a distance measuring unit designed as an interferometer (21) for determining a change in distance to the target by means of interferometry, a laser beam source (20) for generating measuring radiation for the interferometer (21), a base (40) defining a vertical axis, a beam steering unit (43) for emitting the measurement radiation (22) and for receiving at least part of the measurement radiation (22) reflected at the target, the beam steering unit (43) rotating around the vertical axis and an inclination axis that is essentially orthogonal to the standing axis can be pivoted relative to the base in a motorized manner, and an angle measurement functionality for determining an alignment of the beam steering unit (43) relative to the base, the laser tracker (1) being characterized in that the laser diode (3) is embodied Laser beam source (20) in a thermoe electrically temperature-stabilized cell (2), hereinafter referred to as TEC cell, wherein at least the following components are arranged within the TEC cell (2): • a laser diode (3), • collimation optics (4), • an optical mini isolator unit (5), and • at least one polarization-maintaining fiber coupling (7) for the measuring radiation (22) for the interferometer (21).