SMR Home Reference Distance Correction
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Solution Overview
Problem
Current methods for measuring spherically mounted retroreflectors (SMRs) face inaccuracies due to errors in centering and depth measurements, particularly with open-air cube corner retroreflectors, which affect the accuracy of three-dimensional coordinate measurements.
Innovation Solution
A method involving a spherically mounted retroreflector with a cavity containing an air-filled region and a processor-based system to determine the home reference distance by measuring target distances and error vectors, correcting for SMR depth and runout errors using multiple nests and angle measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a spherically mounted retroreflector (SMR) with open-air cube corner retroreflector is used for coordinate measurement, then the measurement capability is enhanced, but measurement precision deteriorates due to centering and depth errors
Solution Approach 1:
The patent replaces mechanical centering methods with an optical-based error detection and correction system. By using the laser tracker to measure the SMR position and applying computational correction for depth and centering errors, the system achieves high precision without requiring perfect mechanical alignment of the retroreflector within the sphere.
Solution Approach 2:
The patent changes the approach from attempting to eliminate physical errors to measuring and compensating for them. By introducing error parameters (depth error, centering error) that can be quantified and corrected through calculation, the system transforms uncorrectable mechanical tolerances into correctable measurement parameters.
2Ease of operation
If traditional laser tracking method is used without error correction, then the measurement process is simple, but measurement precision is reduced due to uncorrected SMR errors
Solution Approach 1:
The patent implements a feedback mechanism where the laser tracker measures the SMR position, the system calculates the depth and centering errors based on these measurements, and then applies corrections to the final coordinates. This closed-loop feedback process automatically compensates for errors without requiring manual intervention or complex setup procedures.
3Measurement precision
If multiple nests and error correction measurements are implemented, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the laser tracker perform multiple functions: it serves as both the primary measurement instrument for capturing SMR positions and as the reference instrument for determining error corrections. This multi-functionality eliminates the need for separate calibration devices or additional measurement equipment, reducing overall system complexity while maintaining high precision.
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 enhances the accuracy of three-dimensional coordinate measurements by correcting for SMR errors, improving the precision of distance and angle measurements, and compensating for SMR depth and runout errors.
Implementation Method 1
the retroreflector returning a portion of the emitted beam as a reflected beam
Data Source
AI summary
A method of finding a home reference distance of a 3D coordinate measurement device in which a mathematical adjustment is made to move the vertex point to the sphere center of a spherically mounted retroreflector (SMR).