Bidirectional Littrow Grating Interferometer Eliminates Polarization Errors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing grating interferometer two-degree-of-freedom measurement systems using polarization optical elements introduce periodic nonlinear errors and complicate the system structure, limiting accuracy and miniaturization.
Innovation Solution
A bidirectional Littrow two-degree-of-freedom grating interference measurement device based on double gratings is developed, eliminating the use of polarization beam splitting prisms or wave plates and integrating the system with only two diffraction gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polarization optical elements (prisms or wave plates) are used to construct the optical path, then the system can achieve two-degree-of-freedom measurement, but periodic nonlinear errors are introduced and the system structure becomes complicated
Solution Approach 1:
The patent removes polarization optical elements (prisms and wave plates) from the optical path, extracting the source of periodic nonlinear errors. Instead of using these traditional components to achieve beam splitting and polarization control, the invention uses a different optical configuration that eliminates these error-introducing elements while maintaining two-degree-of-freedom measurement capability
Solution Approach 2:
The patent replaces the mechanical/optical system using polarization elements with a system based on direct grating interference. The optical path is reconfigured to use grating diffraction and interference patterns instead of polarization beam splitting, substituting the measurement mechanism to eliminate periodic nonlinear errors
2Ease of operation
If polarization beam splitting prisms or wave plates are used, then the system can separate and process orthogonal polarization components, but the system structure becomes very complicated and miniaturization is restricted
Solution Approach 1:
The patent merges the functions of multiple polarization optical elements into a simplified optical path using only two diffraction gratings. The beam splitting, polarization control, and interference measurement functions are combined into a more integrated configuration that reduces the number of discrete components and simplifies the overall system structure
Solution Approach 2:
The diffraction gratings in the patent serve multiple functions simultaneously: they act as beam splitters, create interference patterns, and enable both X and Y direction measurements. This multi-functionality reduces the need for separate polarization elements and simplifies the system architecture
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 eliminates periodic nonlinear errors, simplifies the system structure, and achieves integration, thereby enhancing measurement accuracy and reducing environmental sensitivity, while also allowing for flexibility in replacing optical elements.
Implementation Method 1
the light source is a dual-frequency laser configured to generate an X-direction measurement laser beam and a Y-direction measurement laser beam
Implementation Method 2
X-direction measurement laser beam into the transmission two-dimensional grating to obtain +1st order diffracted light and -1st order diffracted light
Implementation Method 3
the +1st order diffracted light passes through the X-direction quarter-wave plate
Implementation Method 4
is incident on the reflection two-dimensional grating at a Littrow angle to obtain new +1st order diffracted light
Implementation Method 5
is incident on the reflection two-dimensional grating at a Littrow angle
Implementation Method 6
The first optical system is configured to filter out a stable interference signal of a horizontal component in the -2nd order diffracted light
Data Source
AI summary
A bidirectional Littrow two-degree-of-freedom grating interference measurement device based on double gratings includes a transmission two-dimensional grating and a reflection two-dimensional grating. A dual-frequency laser emitted by a light source passes through the transmission two-dimensional grating with a specific grating pitch to form four beams in X direction and Y direction, the four beams are incident on the reflection two-dimensional grating at a Littrow angle, and the four beams diffracted by the reflection two-dimensional grating return to the transmission two-dimensional grating in an incidence direction along the same path; different orders of transmission light of the four beams of light in different directions may form stable interference signals carrying displacement information, and the stable interference signals are received by a detector.