Integrated Dual Polarization Beam-Splitting Assembly for Heterodyne Interferometry
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Solution Overview
Problem
Existing spatially separated heterodyne laser interferometers fail to simultaneously meet the requirements of small sensor head volume, easy integration, good thermal stability, and sub-nanometer level periodic nonlinear errors.
Innovation Solution
A heterodyne laser interferometer based on an integrated dual polarization beam-splitting assembly, which includes a laser light source providing two spatially separated beams with different frequencies, and an integrated dual polarization beam-splitting assembly with specific polarization elements to reduce periodic nonlinear errors and enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spatially separated heterodyne laser interferometer is used, then periodic nonlinear errors are reduced, but sensor head volume becomes large and integration becomes difficult
Solution Approach 1:
The patent combines multiple optical components (beam splitter, mirrors, wave plates) into a highly integrated compact sensor head with volume less than 10cm³. The sensor head integrates the function of spatial separation for reducing periodic nonlinear errors while maintaining a compact form factor suitable for narrow displacement measurement spaces.
Solution Approach 2:
The patent uses orthogonal polarization dimensions to separate measurement and reference beams spatially within a compact volume. By utilizing polarization states (horizontal and vertical) as an additional dimension, the system achieves beam separation without increasing physical volume, resolving the contradiction between error reduction and compact size.
2Measurement precision
If spatially separated heterodyne laser interferometer is used, then periodic nonlinear errors are reduced, but thermal stability deteriorates
Solution Approach 1:
The patent integrates all optical components into a single compact sensor head that is pre-aligned and thermally stabilized together. This integration ensures that thermal expansion or contraction affects all components uniformly, maintaining relative alignment and reducing thermal drift, thus improving thermal stability while keeping the sensor head compact.
3Stability of the object's composition
If integrated dual polarization beam-splitting assembly is used, then thermal stability is improved, but device complexity increases
Solution Approach 1:
The dual polarization beam-splitting assembly serves multiple functions simultaneously: it separates measurement and reference beams, controls polarization states, and maintains thermal stability. By making the beam splitter assembly multi-functional, the patent reduces the need for separate components, thereby managing complexity while achieving thermal stability.
4Volume of moving object
If compact sensor head is designed, then volume is reduced, but integration difficulty increases
Solution Approach 1:
The patent integrates all optical components (beam splitter, mirrors, wave plates, detectors) into a single pre-aligned module with volume less than 10cm³. This integrated design is manufactured as a complete assembly, eliminating the need for field alignment and simplifying installation, thus resolving the contradiction between compact size and ease of integration.
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 integrated dual polarization beam-splitting assembly reduces periodic nonlinear errors to within 0.1 nanometers, achieves zero theoretical thermal drift, and provides good structural thermal stability, making it suitable for applications with narrow displacement measurement space.
Implementation Method 1
a laser light source, used to provide two spatially separated beams with different frequencies
Implementation Method 2
an integrated dual polarization beam-splitting assembly includes a first polarization beam splitter and a second polarization beam splitter arranged in parallel
Implementation Method 3
a first quarter-wave plate QWP1, a second quarter-wave plate QWP2, a third quarter-wave plate QWP3, and a fourth quarter-wave plate QWP4
Implementation Method 4
a first target mirror M1 and a second target mirror M2; an output optical path of the first quarter-wave plate QWP1 is provided with a first target mirror M1
Implementation Method 5
an output optical path of the third quarter-wave plate QWP3 is provided with a first photodetector PDm; an output optical path of the fourth quarter-wave plate QWP4 is provided with a second photodetector PDm
Implementation Method 6
Heterodyne interferometers have advantages such as large dynamic range, high-precision, high signal-to-noise ratio, and strong anti-interference ability
Data Source
AI summary
A heterodyne laser interferometer and a measurement method based on an integrated dual polarization beam-splitting assembly is provided. Technical points: The first polarization beam splitter and the second polarization beam splitter of the integrated dual polarization beam-splitting assembly are arranged in parallel. The first polarization beam splitter is attached with a first polarizer, a third polarizer, and a first quarter-wave plate; The second polarization beam splitter is attached with a second polarizer, a fourth polarizer, and a second quarter-wave plate; The output optical path of the first quarter-wave plate and the second quarter-wave plate is equipped with target mirrors, while the output optical path of the third quarter-wave plate and the fourth quarter-wave plate is equipped with photodetectors. The assembly and adjustment of the present invention is more flexible and reduce the processing difficulty and processing error.