Single-Source Laser Tracker for Synchronous Distance and Displacement
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Solution Overview
Problem
Existing laser tracker systems require multiple light sources for absolute distance, relative displacement, and position change measurements, leading to differences in measured reference wavelengths and difficulties in traceback, particularly in China, where the lack of a single-station-type absolute rangefinder and high complexity of femtosecond laser frequency comb technology pose challenges.
Innovation Solution
A multi-frequency hybrid heterodyne laser tracker system based on a single dual-longitudinal-mode He—Ne laser unit, utilizing a half-wave plate, quarter-wave plates, and acousto-optic frequency shifters to generate multiple polarized light beams with different frequencies, allowing for synchronous measurement of absolute distance, relative displacement, and position change without the need for multiple light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple light sources are used to measure absolute distance and relative displacement, then measurement functionality is improved, but system complexity and volume increase
Solution Approach 1:
The patent segments the measurement functions by frequency rather than by light source. A single laser source generates multiple frequency components through acousto-optic frequency shifting, allowing the system to perform both absolute distance measurement (using beat frequency) and relative displacement measurement (using phase difference) simultaneously. This resolves the contradiction by maintaining measurement versatility while reducing the number of physical light sources from multiple to one.
Solution Approach 2:
The single laser source is designed to serve multiple measurement functions universally. By generating multiple frequency components and using them in different measurement modes (absolute ranging via beat frequency, relative displacement via phase difference), the same light source performs both absolute and relative measurements, eliminating the need for separate light sources for different measurement types.
2Adaptability or versatility
If multiple light sources with different reference wavelengths are used, then measurement coverage is improved, but traceback difficulty increases
Solution Approach 1:
The patent changes the frequency parameter of a single laser source to generate multiple frequency components. All frequency components originate from the same laser source with known reference wavelength, ensuring consistent traceback. The frequency modulation allows different measurement functions while maintaining a unified reference frame, resolving the contradiction between measurement coverage and traceback capability.
3Measurement precision
If dual-frequency interferometer is used for relative displacement measurement, then measurement precision is improved, but system volume and complexity increase
Solution Approach 1:
The patent merges the absolute distance measurement system and relative displacement measurement system into a single integrated system. Both measurements use the same laser source and optical path, with frequency modulation enabling dual functionality. This consolidation reduces system volume and complexity while maintaining the measurement precision of dual-frequency interferometry for relative displacement.
4Volume of stationary object
If single light source is used, then system volume is reduced, but measurement synchronization may be compromised
Solution Approach 1:
The patent uses periodic frequency modulation of the laser source to ensure measurement synchronization. The acousto-optic modulator introduces periodic frequency shifts that create beat signals with stable phase relationships. This periodic action maintains synchronization between absolute and relative measurement channels while using a single compact light source.
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 simplifies the system by using a single light source, reducing system volume, improving measurement synchronization, and enabling precise absolute distance and relative displacement measurements while reducing the complexity and cost associated with dual-frequency interferometers.
Implementation Method 1
a first acousto-optic frequency shifter 6, a second acousto-optic frequency shifter 8, a third acousto-optic frequency shifter 14 and a fourth acousto-optic frequency shifter 17 to form polarized light with four different frequencies
Implementation Method 2
the horizontally polarized light beam and vertically polarized light beam which is obtained upon reflection by a third reflector 11 are transformed into circularly polarized light after passing through a first quarter-wave plate 4 and a second quarter-wave plate 12 respectively
Implementation Method 3
a light beam passes through a half-wave plate 2 and afterwards enters a first polarization beamsplitter 3, through which it is split into a horizontally polarized light beam and a vertically polarized light beam
Implementation Method 4
a dual-longitudinal-mode He—Ne laser unit 1
Data Source
AI summary
The present disclosure provides a multi-frequency hybrid heterodyne laser tracker system based on a single light source. According to the laser tracking system proposed in the present disclosure, multi-frequency laser is obtained by conducting multi-acousto-optic frequency shift on a dual-longitudinal-mode laser unit, and an absolute ranging precision gauge is constructed by using a dual-longitudinal-mode interval of a light source. With the frequency shift difference of a multi-acousto-optic frequency shifter, an absolute ranging roughness gauge is constructed, and the relative displacement measurement of dual-frequency light interference is achieved. Meanwhile, by utilizing the reflection of multiple reflectors and light splitting and combining of polarization prisms, synchronous measurement of multi-wavelength absolute distance, relative displacement and PSD position is achieved, resolving the problem that an existing laser tracker uses multiple light sources, which leads to difference in measurement datum, and consequently to the difficultly in traceback.