Optical Positioning Device Asymmetric Grating Wavelength Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical position measuring devices are sensitive to wavelength changes and require complex and expensive light source stabilization to maintain accuracy, especially when the sensitivity vector is oriented obliquely to the material measure, limiting their efficiency and increasing costs.
Innovation Solution
An optical position measuring device with a measuring graduation optimized for high diffraction efficiency, featuring a superstructure grating with asymmetric grating discontinuities and a tilted plane of symmetry, allowing for mirror-symmetric propagation of partial beams and interference, which reduces sensitivity to wavelength changes and enhances scanning efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sensitivity vector is oriented obliquely to the material measure surface, then position information along two translational degrees of freedom can be detected, but the device becomes sensitive to wavelength changes requiring complex and expensive light source stabilization
Solution Approach 1:
The patent applies asymmetry by using an asymmetrical measuring graduation design where the grating discontinuities are positioned asymmetrically within the graduation period. This asymmetrical structure, combined with the tilted plane of symmetry, enables the generation of non-symmetrical diffraction orders that interfere to produce position signals. The asymmetrical design fundamentally changes the optical path characteristics, making the measurement insensitive to wavelength variations while maintaining the ability to detect position changes along two translational degrees of freedom, thus eliminating the need for complex light source stabilization
2Adaptability or versatility
If the sensitivity vector is oriented obliquely to the material measure surface, then position information along two translational degrees of freedom can be detected, but the cost increases due to expensive light source stabilization requirements
Solution Approach 1:
The asymmetrical measuring graduation with asymmetrically positioned grating discontinuities creates an optical interference pattern that is inherently insensitive to wavelength changes. This design eliminates the need for expensive active light source stabilization systems, thereby reducing manufacturing costs while maintaining the capability to detect position along two translational degrees of freedom
Solution Approach 2:
The patent changes the fundamental parameter of the measuring graduation structure by introducing a superstructure with asymmetric grating discontinuities and a tilted plane of symmetry. This parameter change transforms the optical measurement principle, making it insensitive to wavelength variations and eliminating the need for costly stabilization equipment
3Measurement precision
If a complex light source stabilization is implemented, then measurement accuracy is maintained, but the device complexity and cost increase
Solution Approach 1:
The asymmetrical measuring graduation design fundamentally changes the measurement principle to one that is insensitive to wavelength changes. By using non-symmetrical diffraction orders from the asymmetrically structured grating, the interference pattern remains stable without requiring active light source stabilization, thus maintaining measurement precision while eliminating device complexity
4Productivity
If the measuring graduation is optimized for high diffraction efficiency, then scanning efficiency is enhanced, but the grating structure becomes more complex
Solution Approach 1:
The asymmetrical grating structure with specifically positioned discontinuities is designed to maximize diffraction efficiency into the required non-symmetrical diffraction orders. The asymmetric design concentrates diffracted energy into the useful orders, enhancing scanning efficiency while the grating structure itself remains a static, manufacturable component without moving parts or complex actuation mechanisms
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 device achieves high signal strength and tolerance in tilting angles, enabling proper function with greater flexibility in mounting orientations and eliminating the need for costly light source stabilization, making it more efficient and cost-effective.
Implementation Method 1
partial beams of rays are caused to interfere in this position measuring device, resulting from non-symmetrical diffraction orders at the measuring graduation
Implementation Method 2
an incident beam of rays is split into at least two partial beams of rays, which are finally brought to an interfering superimposition
Data Source
Figure 1a~1c
Figure 2a~2c
Figure 3
AI summary
The present invention relates to an optical position-measuring device for detecting the position of two relatively movable objects. It comprises a measuring graduation, which is connected to one of the two objects and comprising a measuring graduation with a periodic arrangement of division regions along at least a pitch direction. Further, the position measuring device comprises a scanning unit connected to the other object with a plurality of optical elements that is movably disposed relative to the material measure. resulting in a scanning beam, propagating in the reaching to the interference sub-beams with respect to a plane of symmetry mirror-symmetrical and either V-shaped incident on the measuring scale and / or undergo a V-shaped back-reflection from the scale on the arrangement and configuration of the optical elements of the scanning unit. The plane of symmetry is tilted by a defined tilt angle about an axis of rotation which is oriented parallel to the surface of the material measure and extending perpendicular to the splitting direction.