Optical Positioning Device Chirped Reference Marking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical position measuring devices face challenges in generating a reference signal using chirped reference markings due to small deflection angles, which require large scanning distances and complex collimation, making them unsuitable for certain scanning principles.
Innovation Solution
Selecting a mean graduation period for the chirped reference marking in the range of the incremental graduation period, ensuring larger deflection angles for beam separation, and using phase-shifted partial reference signals processed by signal electronics to generate a defined reference signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the graduation periods of the reference marking are selected to be significantly larger than the incremental graduation period (1.5*TP INC to 5*TP INC), then the reference signal can be generated with the interferential scanning principle, but the deflection angles become too small, requiring very large scanning distances and complex collimation
Solution Approach 1:
The patent changes the parameter of mean graduation period from the conventional range (1.5*TP INC to 5*TP INC) to a range close to the incremental graduation period (0.8*TP INC to 1.2*TP INC). This parameter change increases the deflection angle of partial beams, enabling smaller scanning distances while maintaining reference signal generation capability
Solution Approach 2:
The patent uses a chirped (locally variable) graduation period structure that dynamically adjusts the graduation period across different regions. By having the graduation period vary locally, the system can optimize the deflection angle for reference signal generation while maintaining compatibility with the incremental graduation, thus resolving the contradiction between signal generation and scanning distance
2Measurement precision
If the graduation periods of the reference marking are selected to be significantly larger than the incremental graduation period, then the reference signal can be generated, but the mounting tolerances become more difficult to ensure and collimation becomes more complex
Solution Approach 1:
The patent changes the mean graduation period parameter to be close to the incremental graduation period, which increases the deflection angle. This parameter change reduces the required scanning distance and relaxes the collimation requirements, thereby reducing device complexity while maintaining reference signal generation
Solution Approach 2:
The chirped graduation period structure dynamically adapts the graduation period to optimize optical performance. This dynamic structure allows the system to achieve proper beam separation and signal generation without requiring complex collimation arrangements, thus reducing device complexity
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
Enables the use of chirped reference markings with smaller scanning distances, improving mounting tolerances and simplifying light source collimation, while maintaining high-resolution position information.
Implementation Method 1
the resulting angle of diffraction or deflection of the bundle of rays for reference signal generation
Implementation Method 2
The displacement-dependent scanning signals in the form of the incremental and reference signals are obtained from the constructive and destructive superimposition of several partial beams of rays
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The unit (10) has a measuring scale and a scanning unit (20) respectively connected with two objects, where the scale exhibits incremental partitions (11) and reference markings (12.1, 12.2) at a reference position (xREF), where the partitions extend in a measuring direction. The scanning unit produces a reference signal at the reference position. The reference marking (12.2) possesses a middle partition period within a region of a division period of the incremental partitions.