Optical Position Measuring Device with Integrated Polarization Grating
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Solution Overview
Problem
Conventional optical position measuring devices with polarization coding have fixed polarization states of superimposed partial beams, leading to stationary great circles in Poincare representation, limiting the generation of phase-shifted scanning signals and requiring additional polarization-optical components in the beam path.
Innovation Solution
An optical position measuring device with a scanning optics design where the polarization states of partial beams can be orthogonally oriented along degrees of freedom of movement, using high-frequency gratings as polarization means with a polarization period greater than the graduation period of the grating, eliminating the need for additional polarization-optical components and allowing for variable polarization effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate polarization-optical components are arranged in the beam path of partial beams, then the polarization states of partial beams can be fixedly predetermined, but the device complexity increases and the beam path becomes more complicated
Solution Approach 1:
The patent combines the polarization-optical functionality into the scanning grating itself, which simultaneously performs beam splitting and polarization encoding. The scanning grating is designed with alternating regions having different polarization properties (e.g., different groove orientations or materials) that directly impart orthogonal polarization states to the diffracted partial beams, eliminating the need for separate polarization components in the beam path.
Solution Approach 2:
The scanning grating is designed to perform multiple functions: it acts as both the diffraction element for beam splitting and the polarization encoding element. By integrating polarization-optical properties (such as anisotropic groove structures or birefringent materials) into the grating, it simultaneously controls the spatial distribution and polarization state of the diffracted beams, reducing the overall component count.
2Device complexity
If fixed polarization states are used for partial beams, then the polarization coding is simplified, but the adaptability to different measurement configurations is limited
Solution Approach 1:
The patent enables dynamic control of polarization states by making the scanning grating's polarization properties可调 (adjustable). This can be achieved through mechanically adjustable grating orientations, switchable birefringent materials, or programmable spatial light modulators that can change the polarization encoding in real-time, allowing adaptation to different measurement configurations while maintaining systematic polarization coding.
3Measurement precision
If additional polarization-optical components are arranged in the beam path, then the polarization control is enhanced, but the thermal influence increases and measurement stability decreases
Solution Approach 1:
By integrating the polarization-optical functionality directly into the scanning grating structure, the patent eliminates or minimizes the number of separate polarization components (such as polarizers, wave plates, or polarizing beam splitters) that would be susceptible to thermal effects. The grating itself, being a rigid optical element, can be designed with thermal compensation or made from low thermal expansion materials to maintain stable polarization encoding across temperature variations.
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 design generates phase-shifted scanning signals with high modulation and stability, ensuring accurate position detection without additional polarization components, reducing thermal influence and simplifying the beam path, while maintaining high resolution and resistance to temperature fluctuations.
Implementation Method 1
A beam of rays emitted by a light source is split by a first grating into at least two partial beams of rays
Implementation Method 2
polarization means whose polarization effects on the partial beams of rays incident thereon along degrees of freedom of movement of the scale can be changed periodically
Implementation Method 3
The split partial beams of rays are finally reunited to form a resulting beam of rays
Data Source
Figure 1a~1b
Figure 2
Figure 3a~3b
AI summary
The device has a light source for emitting a radiation beam that is divided into two partial radiation beams by a dividing grid (41). The partial beams are reintegrated into a resulting radiation beam. A detection unit (40) produces displacement-dependent scanning signals from the resulting beam. A reflector is arranged in optical paths of the partial beams, where polarization effects of the reflector are changed periodically with polarization periods along movement degree of freedom of a measuring rod (20). The polarization periods are larger than dividing periods of the grid.