Absolute Position Measurement Scale Using Overlapping Binary Codes
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Solution Overview
Problem
Existing absolute position measurement technologies face challenges in providing accurate and efficient absolute position measurements due to resolution limitations and complex configurations, particularly in precision systems where incremental position measurements require initialization and have alignment issues.
Innovation Solution
A novel absolute position measurement method using a scale pattern formed by pseudo-random-codes with overlapping symbols, where the pattern is read to extract coarse and fine absolute position information through summing signals and phase analysis, allowing for accurate absolute position calculation without additional initialization or complex configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-track code scale is used to provide absolute position, then absolute position information can be obtained, but device complexity and alignment issues increase
Solution Approach 1:
The patent combines multiple track codes into a single-track binary code structure. The absolute position information that previously required multiple parallel tracks is now encoded in a sequential binary pattern along a single track, reducing structural complexity while maintaining the ability to determine absolute position through binary decoding of the pattern sequence
Solution Approach 2:
The single-track code is divided into multiple segments or zones along the measurement direction, with each segment containing binary patterns that encode position information. This segmentation allows the system to determine absolute position by identifying which segment is currently being read and decoding the binary pattern within that segment
2Measurement precision
If incremental position measurement is used, then relative position can be measured accurately, but initialization is required and absolute position cannot be provided
Solution Approach 1:
The system pre-encodes absolute position information directly into the single-track binary code pattern structure. Unlike incremental encoders that start from an unknown position, this system has predetermined binary patterns that represent specific absolute positions, allowing the reader to immediately determine absolute position without requiring initialization or reference to a home position
3Manufacturing precision
If higher resolution is achieved through multi-track configuration, then position accuracy improves, but alignment precision requirements increase
Solution Approach 1:
The patent merges the functionality of multiple aligned tracks into a single track with sequential binary patterns. This eliminates the need for precise alignment between multiple tracks while maintaining high resolution through the binary encoding scheme, where resolution is determined by the length of the binary sequence rather than the number of parallel tracks
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 method enables precise absolute position measurement with high resolution and simplicity, reducing alignment complexities and eliminating the need for additional initialization, thus improving the efficiency and robustness of precision systems.
Implementation Method 1
The optical encoder uses a scale. The scale has uniform and periodical patterns, which has uniform periodic patterns with several or tens of micrometer pitch, and obtains position readouts by processing an interference fringe or an intensity profile.
Data Source
AI summary
Provided are an absolute position measurement method, an absolute position measurement apparatus, and a scale. The scale includes a scale pattern formed by replacing repeatedly arranged pseudo-random-codes with a sequence of a linear feedback shift register of N stages using a first symbol with first width representing a first state and a second symbol with second width representing a second state. The first is divided into two or more first symbol areas of different structures, and the second symbol is divided into two or more second symbol areas of different structures. There is at least one overlap area in which the first symbol and the second symbol overlap each other to have the same structure.