Passive Optical Correction of Polarization Leakages
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Solution Overview
Problem
Optical heterodyne interferometers face periodic error due to impure polarization states of optical reference sources, which cannot be effectively corrected by existing waveplate solutions, especially for non-orthogonal polarization states.
Innovation Solution
A passive optical system incorporating quarter wave plates and polarization elements, configured to provide diattenuation and retardance, with tunable rotational and incident angles, is used to correct polarization errors in optical reference beams, reducing periodic errors to a non-measurable level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If waveplates are used to correct polarization state, then polarization ellipticity can be corrected, but non-orthogonality of polarization states cannot be corrected and periodic error remains
Solution Approach 1:
The patent changes the fundamental parameters of polarization correction by introducing diattenuation (polarization-dependent absorption) in addition to retardance. This allows correction of non-orthogonal polarization states that waveplates alone cannot correct, thereby eliminating periodic error while maintaining measurement precision.
Solution Approach 2:
The patent employs composite optical elements that combine multiple functions (diattenuation and retardance) into single polarization elements. These composite elements can simultaneously correct both polarization ellipticity and non-orthogonality, achieving complete polarization correction without residual periodic error.
2Measurement precision
If waveplates are used to correct polarization, then polarization state is improved, but the solution is insufficient for non-orthogonal polarization states
Solution Approach 1:
The patent extends polarization correction capability by introducing diattenuation as a new correctable parameter. This enables the system to handle non-orthogonal polarization states that were previously uncorrectable, significantly improving adaptability while maintaining high measurement precision for various polarization states.
3Device complexity
If traditional polarization correction is used, then simple waveplate configuration is maintained, but periodic error cannot be reduced to non-measurable level
Solution Approach 1:
The patent uses composite polarization elements that integrate multiple correction functions (diattenuation and retardance) into single components. This approach achieves ultra-precise periodic error reduction to non-measurable levels while avoiding the complexity of multiple separate waveplates and correction elements.
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 system significantly reduces periodic errors in optical reference sources, improving the precision of position and distance measurements in optical interferometry systems.
Implementation Method 1
The first and second polarization elements are each configured to provide both diattenuation and retardance of the optical reference beam
Implementation Method 2
The first and second polarization elements are each configured to provide both diattenuation and retardance of the optical reference beam
Data Source
AI summary
Passive optical systems and methods for improving polarization of an optical reference beam are disclosed. For example, an optical system includes first and second quarter wavelength plates (QWPs) positioned in a beam path of the optical system. The second QWP is positioned in the beam path such that a fast axis of the second QWP is substantially orthogonal to a fast axis of the first QWP. First and second polarization elements are also positioned in the beam path. The first and second polarization elements are each configured to provide both diattenuation and retardance of the optical reference beam.