Sphere Bar Probe for Hidden Point Laser Measurement
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Solution Overview
Problem
Current methods for measuring hidden points using laser trackers are either limited by the geometry of retroprobes or are expensive due to the need for six degrees of freedom, which increases the cost and complexity of the measurement process.
Innovation Solution
A sphere bar probe apparatus is introduced, featuring a spherically mounted retroreflector and a holder with a member having a radius of curvature, allowing the laser tracker to measure hidden points by providing a virtual sphere that maintains the constant distance from the center to the end point, enabling accurate measurements even when the point is out of direct line of sight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a retroprobe is used to measure hidden points, then the measurement can be performed, but the geometry orientation is restricted and cannot be adjusted
Solution Approach 1:
The probe incorporates a spherical end surface with a retroreflector mounted on it. This spherical geometry allows the probe to contact hidden points from multiple orientations while maintaining a constant distance relationship, eliminating the geometric orientation restrictions of traditional retroprobes. The sphere's curvature enables the probe to adapt to various hidden point locations without requiring complex repositioning.
2Measurement precision
If a six-DOF laser tracker is used to measure hidden points, then accurate measurements are achieved, but the cost and complexity increase significantly
Solution Approach 1:
The spherical probe acts as an intermediary between the laser tracker and the hidden point. By mounting the retroreflector on the spherical end surface, the probe creates a virtual sphere that maintains a constant distance relationship with the hidden point. This allows a standard 3-DOF laser tracker to achieve hidden point measurements through the probe's geometric relationship, eliminating the need for expensive 6-DOF trackers.
Solution Approach 2:
The spherical probe creates a virtual image or representation of the hidden point through the retroreflector's reflection. The retroreflector on the spherical surface generates a virtual sphere that copies the geometric relationship of the hidden point, allowing the laser tracker to measure the virtual sphere's position and infer the hidden point's coordinates without directly contacting it.
3Adaptability or versatility
If a standard SMR is used, then the laser tracker can measure surface coordinates, but hidden points out of direct line of sight cannot be measured
Solution Approach 1:
The spherical probe adds a dimensional relationship between the retroreflector and the hidden point. By positioning the retroreflector on the spherical surface at a known offset distance, the system creates a geometric relationship that allows measurement of hidden points through trigonometric calculations. This dimensional addition enables the laser tracker to indirectly measure points that would otherwise be out of direct line of sight.
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
The sphere bar probe apparatus allows for cost-effective measurement of hidden points by using a spherically mounted retroreflector and a holder with a radius of curvature, providing a virtual sphere that maintains the constant distance, thus enabling accurate measurements without the need for expensive six-DOF trackers.
Implementation Method 1
The laser tracker sends a laser beam to a retroreflector target. A common type of retroreflector target is the spherically mounted retroreflector (SMR), which comprises a cube-corner retroreflector embedded within a metal sphere.
Implementation Method 2
The cube-corner retroreflector comprises three mutually perpendicular mirrors. The vertex, which is the common point of intersection of the three mirrors, is located at the center of the sphere.
Data Source
AI summary
Exemplary embodiments include a sphere bar probe apparatus, including a holder, a retroreflector disposed in the holder, a member having a first end and a second end, wherein the first end is attached to the holder and an end plate attached to the second end of the member.