Optical Rotation Angle Measuring System Using Segmented Grating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical systems for measuring the rotation angle of rotatable objects are limited by high sensitivity to transverse displacements of the rotation shaft, large moment of inertia, and lack of compactness, which affects measurement accuracy and dynamics.
Innovation Solution
An optical system featuring a reflective diffraction element mounted on the rotation shaft, with a radiation source emitting nearly monochromatic radiation, and a radiation-sensitive detection structure comprising an annular grating structure, where the diffraction element projects diffraction order images onto small sections of the grating, reducing the inertial load and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large-radius ring-shaped grating is used to achieve high measurement resolution, then measurement precision is improved, but the moment of inertia increases significantly
Solution Approach 1:
The patent divides the grating structure into two separate components: a small rotating diffraction grating element mounted on the shaft and a large stationary annular grating structure. This segmentation allows the moving part to have minimal moment of inertia while the stationary part provides the large radius needed for high measurement precision.
Solution Approach 2:
The patent transitions from a conventional single-plane grating arrangement to a multi-dimensional optical path configuration where the rotating diffraction element projects images onto the stationary annular grating at a distance, effectively utilizing the third dimension (axial distance) to achieve large measurement radius without increasing moving mass.
2Measurement precision
If a conventional grating system is used to achieve high resolution, then measurement accuracy is improved, but sensitivity to transverse shaft displacements increases
Solution Approach 1:
By projecting the diffraction pattern axially onto the stationary annular grating at a distance, the system creates a virtual measurement plane that is decoupled from transverse displacements of the rotating shaft, reducing sensitivity to this harmful factor while maintaining high measurement accuracy.
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 provides more accurate and compact rotation angle measurements with reduced sensitivity to transverse displacements, enabling higher resolution and faster scanning capabilities while minimizing the inertial load on the angular decoder.
Implementation Method 1
a reflective diffraction element (6) mounted on, and rotating with, the shaft (2)... the diffraction element is configured to project diffraction order images (18) of its pattern onto associated sections (50(1)-54(2)) of an annular grating structure
Implementation Method 2
a radiation-sensitive detection structure (14,16)... converting illumination beam radiation reflected by the diffraction element into electrical signals suitable for electronic processing
Data Source
AI summary
The present invention is directed to an optical system for measuring the rotation angle of rotatable object having a rotation shaft (2), which system comprises a reflective diffraction element (6) mounted on said shaft and a module that includes a radiation source (8) emitting a monochromatic beam (bo) towards this element and a radiation-sensitive detection structure (14, 16), the diffraction element is configured to project diffraction order images (18) of its pattern onto associated sections (50(1)-54(2)) of an annular grating structure forming part of the detection structure and the surface size of the diffraction element is smaller than 20% of the surface size of the annular grating structure.