Laser Tracking Interferometer Inspection Accuracy
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Solution Overview
Problem
The existing method for inspecting positioning machines using a laser tracking interferometer lacks accuracy when measurement points are not precisely placed on a straight line, leading to errors in pitch measurement along that line.
Innovation Solution
The method involves determining the position vector of the rotation center of the laser tracking interferometer, positioning the retroreflector at multiple points near a straight line, measuring distances, performing coordinate transformations, and computing distance differences through orthogonal projection to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If measurement points are positioned exactly on a straight line during inspection, then measurement accuracy is improved, but positioning difficulty and operation complexity increase
Solution Approach 1:
The patent introduces a straight line model as an intermediary computational element. Instead of requiring precise physical positioning of measurement points on a straight line, the system establishes a mathematical straight line model through coordinate transformation and uses this model to calculate pitch measurements. This mediator allows flexible measurement point selection while maintaining measurement accuracy through computational projection onto the straight line model.
Solution Approach 2:
The patent transforms the measurement approach by changing from direct physical positioning parameters to coordinate transformation parameters. By establishing a coordinate system where the straight line becomes an axis and performing coordinate transformations, the system converts the problem of precise physical positioning into a mathematical coordinate calculation problem, allowing measurement points to be selected more freely while maintaining accuracy through computational methods.
2Ease of operation
If measurement points are positioned near a straight line rather than exactly on it, then operation ease is improved, but measurement accuracy deteriorates
Solution Approach 1:
The straight line model serves as a mathematical intermediary that connects flexible measurement point selection with accurate pitch measurement. The system projects measurement data onto this intermediary model through coordinate transformation, allowing measurement points to be positioned nearby rather than exactly on the line while recovering accurate pitch values through the mathematical model.
Solution Approach 2:
The patent solves the positioning accuracy problem by adding a computational dimension through coordinate transformation. Instead of relying solely on physical positioning accuracy in three-dimensional space, the system introduces a mathematical dimension where points are projected onto a two-dimensional coordinate system defined by the straight line model, effectively separating positioning flexibility from measurement accuracy.
3Measurement precision
If complex coordinate transformation and orthogonal projection calculations are performed, then measurement accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent performs preliminary coordinate transformation to establish a simplified coordinate system where the straight line becomes an axis before performing measurements. This preliminary action pre-processes the coordinate data, so that subsequent pitch calculations only require simple projections onto the established axis rather than complex three-dimensional geometric calculations, reducing computational complexity while maintaining 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
This approach allows for high-accuracy geometric inspection along a straight line even when measurement points are not exactly on the line, reducing errors and enhancing the precision of positioning machine inspection.
Implementation Method 1
a laser interferometer on which an optical axis shift detection sensor for detecting the amount of shift in the optical axis of return light is mounted
Implementation Method 2
a retroreflector that is secured to an object to be measured... an optical element for collimating incident and reflected beams of light
Data Source
AI summary
To inspect a positioning machine by a laser tracking interferometer that tracks a retroreflector using a laser beam, the positioning accuracy of the positioning machine is evaluated by comparing a distance Δdij,C with a distance Δdij,L measured by the laser tracking interferometer, the distance Δdij,C being acquired by orthogonal projection of the position vectors of measurement points pi and pj measured by the positioning machine to the straight line gk passing through the rotation center M of the laser tracking interferometer.