Spherical Target Retroreflector Centering Error Correction
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Solution Overview
Problem
Current methods for measuring the center of spherical targets containing retroreflectors, such as SMRs, face inaccuracies due to miscentering of cube corner retroreflectors within the sphere, especially with glass cube corners, which affect the accuracy of distance and angle measurements in laser tracking systems.
Innovation Solution
A method involving a transmitter emitting an electromagnetic signal and a temperature sensor to correct for the centering error by determining the three-dimensional coordinates of the sphere center, accounting for the bending of light in glass cube corners, and using locator cameras and light sources to establish the coarse orientation of the retroreflector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a glass cube corner retroreflector is used in a spherical target, then the target can be manufactured with certain precision, but the bending of light in the glass causes inaccuracies in distance and angle measurements
Solution Approach 1:
The patent introduces an intermediary computational correction process that accounts for the known bending of light in glass cube corners. By calculating the expected deviation based on glass refractive properties and applying corrective transformations to the measured coordinates, the system compensates for the optical distortion without changing the physical target structure or measurement methodology.
2Stability of the object's composition
If the cube corner retroreflector is embedded within the sphere, then the target structure is stabilized, but centering errors occur affecting measurement accuracy
Solution Approach 1:
The patent makes the spherical target multi-functional by incorporating both the retroreflector for distance/angle measurement and a detectable center indicator (such as a reflective marker or geometric feature) for center location determination. This allows the same target structure to serve multiple measurement purposes simultaneously, enabling the system to capture both the structural stability benefit and the centering accuracy requirement.
Solution Approach 2:
The patent implements a feedback mechanism where the measured position of the retroreflector relative to the sphere center is used to calculate and apply centering error corrections. By continuously monitoring the offset between the retroreflector vertex and the sphere center, the system dynamically adjusts coordinate measurements to compensate for misalignment, thereby maintaining measurement precision despite structural constraints.
3Loss of information
If six-DOF measurement capability is implemented, then more comprehensive data is obtained, but the complexity of the system increases
Solution Approach 1:
The patent segments the six-DOF measurement capability into two independent functional components: a retroreflector for capturing distance and angular information (three degrees of freedom), and a center indicator or marker system for determining orientation (three additional degrees of freedom). This segmentation allows the system to achieve comprehensive six-DOF measurement capability while maintaining simpler individual components that can be processed separately, reducing overall system complexity.
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 measuring the center of spherical targets, improving the precision of laser tracking systems by correcting for the miscentering errors and the refractive effects in glass cube corner retroreflectors, allowing for more reliable and precise coordinate measurements.
Implementation Method 1
A retroreflector is provided. The retroreflector and at least one surface define a space therebetween.
Implementation Method 2
A transmitter is provided affixed to the body. The transmitter is configured to emit an electromagnetic signal.
Implementation Method 3
A temperature sensor is provided affixed to the body. The temperature sensor is configured to measure a temperature
Implementation Method 4
accounting for the bending of light in glass cube corners
Data Source
AI summary
A target is provided having a retroreflector. A body is provided having a spherical exterior portion, the body containing a cavity. The cavity is sized to hold the retroreflector, the cavity open to the exterior of the body and having at least one surface opposite the opening, the retroreflector at least partially disposed in the cavity, wherein the retroreflector and at least one surface define a space therebetween. A transmitter is configured to emit an electromagnetic signal. A first actuator is configured to initiate emission of the electromagnetic signal, wherein the transmitter and the first actuator are affixed to the body.