Single-Track Position Encoder for Nanoscale Absolute Measurement
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Solution Overview
Problem
Current one-dimension position encoders face challenges in achieving nanoscale resolution due to the size and cost of double-track rulers, alignment issues between absolute and regular tracks, noise sensitivity, and thermal expansion effects, which compromise precision and compactness.
Innovation Solution
A one-dimension position measurement system using a single one-dimension binary code on a first ruler, a second parallel ruler with different thermal expansion coefficients, and a camera to acquire code portions, with processing to compute absolute position and compensate for temperature and tilt effects, allowing for precise measurement without the need for multiple cameras or large field views.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a double-track ruler with absolute track and regular track is used to achieve nanoscale resolution, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The patent combines the absolute track and regular track into a single integrated ruler structure. The code is applied directly on the object surface with both absolute position identification and interpolation capabilities in one unified track, eliminating the need for separate dual-track structures while maintaining nanoscale measurement precision.
Solution Approach 2:
The single ruler track serves multiple functions simultaneously: it provides absolute position identification through unique code patterns and enables precise interpolation measurement through the same track structure. This multi-functional design replaces the need for separate absolute and regular tracks.
2Measurement precision
If a double-track ruler is used to achieve precise absolute position, then measurement precision is improved, but manufacturing alignment difficulty increases
Solution Approach 1:
By merging the absolute and regular tracks into a single integrated track structure, the patent eliminates the alignment issues between separate tracks. The code is applied as one unified pattern on the ruler surface, ensuring that absolute position and interpolation data are inherently aligned without requiring separate alignment procedures.
3Measurement precision
If multiple cameras or larger field of view is used to read both tracks independently, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the reading function into a single camera system that captures the entire code pattern on the ruler in one field of view. The image processing algorithm then extracts both absolute position and interpolation data from the same captured image, eliminating the need for multiple cameras or complex multi-camera coordination systems.
4Device complexity
If a single CCD line is used per code track to reduce device complexity, then device complexity is reduced, but measurement precision decreases due to noise
Solution Approach 1:
The patent uses a single camera with a two-dimensional sensor array that captures the entire code pattern simultaneously. The image processing algorithm processes the captured image to extract code information, effectively combining the reading function of multiple CCD lines into one sensor system while maintaining precision through digital image processing and error correction algorithms.
Data Source
AI summary
A one-dimension position measurement system includes: a first ruler having a first one-dimension binary code si applied thereon, a camera for acquiring a picture of a portion of the code si, the portion having a length of I bits, and some processing elements. Each codeword of length I of the one-dimension code si is unique within the whole code si. A codeword ai is read from the acquired picture, and the processing elements are implemented for computing an absolute position p of the codeword ai of the code si from: (I). An ad-hoc interpolation method is used to obtain a precision way below the distance between two bits of the codewords. The code si may be applied on the ruler by using some geometric primitives, a geometric primitive for encoding a “1” being different from a geometric primitive for encoding a “0”, both having the same horizontal projection. The horizontal projection is then used for fine interpolation, achieving nanometer-scale resolution.