3D Coordinate Measurement with TOF Camera and Motorized Axes
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Solution Overview
Problem
Existing 3D coordinate measurement devices face challenges in efficiently acquiring and processing large volumes of data, often requiring manual operator input to characterize the environment and may lose distance information due to beam breaks, necessitating the need for improved accuracy and automation in measuring six degrees of freedom.
Innovation Solution
A coordinate measurement device incorporating a 3D time-of-flight (TOF) camera and motorized axes with angle measuring devices to determine 3D coordinates based on camera images, angle rotations, and distance measurements, enabling automated and accurate acquisition of 3D data with a wide field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a laser tracker uses a retroreflector target with cube-corner mirrors, then the target can reflect laser beams back to the tracker, but the perpendicular distance from the apex to the object surface remains constant despite rotation, limiting 6DOF measurement capability
Solution Approach 1:
The retroreflector target is divided into multiple cube-corner retroreflectors positioned at different locations on the spherical surface. Each cube-corner measures distance along its own normal vector, and the processor combines measurements from multiple cube-corners to calculate 6DOF pose, enabling both versatile measurement and maintaining precision through redundant measurements.
Solution Approach 2:
The system transitions from measuring only 3D coordinates to measuring 6DOF by adding rotational information. Multiple cube-corner retroreflectors are arranged in specific spatial configurations (e.g., tetrahedral, octahedral) to capture distance information from multiple dimensions, allowing the system to derive both position and orientation simultaneously.
2Productivity
If an interferometer is used to measure distance, then incremental measurements can be made, but beam breaks cause loss of distance information
Solution Approach 1:
The system uses multiple cube-corner retroreflectors providing redundant distance measurements. If one measurement path experiences a beam break, the processor can detect the loss and rely on alternative measurement paths from other cube-corners to maintain continuous tracking of the target's 6DOF pose.
Solution Approach 2:
The system switches from incremental distance measurement (interferometer) to absolute distance measurement (ADM) for the retroreflector target. ADM provides absolute distance information that does not depend on continuous beam presence, eliminating the beam break vulnerability while maintaining measurement capability.
3Ease of operation
If manual operator input is required to characterize the environment, then flexibility in measurement setup is achieved, but measurement time and complexity increase
Solution Approach 1:
The measurement system automatically characterizes the environment by using the 3D camera to capture images of the retroreflector target and surrounding features. The processor automatically identifies target features, calculates 6DOF pose, and establishes measurement references without requiring manual operator input for environmental characterization, reducing setup time while maintaining flexibility.
Solution Approach 2:
The system performs preliminary environmental characterization using the 3D camera to capture and analyze the measurement scene before actual coordinate measurement begins. This preliminary action includes identifying retroreflector positions, establishing coordinate systems, and detecting environmental features, which prepares the system for rapid subsequent measurements.
4Adaptability or versatility
If a 3D camera is added to provide wide field of view, then environmental characterization is improved, but device complexity increases
Solution Approach 1:
The 3D camera serves multiple functions: it characterizes the environment, locates retroreflector targets, provides wide-field visualization for operator guidance, and assists in establishing measurement references. By making the camera multi-functional, the system gains enhanced adaptability without proportionally increasing complexity, as a single component performs multiple critical tasks.
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 solution allows for rapid and accurate acquisition of 3D coordinates, reducing manual input and minimizing data loss, while enabling the device to operate with six degrees of freedom and provide detailed environmental characterization.
Implementation Method 1
A 3D time-of-flight (TOF) camera is arranged within the housing, the TOF camera being arranged coaxially with the first axis, the 3D TOF camera oriented to acquire an image of an object reflected from the mirror
Implementation Method 2
A mirror is coupled to the first motor and rotates about the first axis, the first motor and second motor being positioned such that the intersection of the first axis and second axis lies on the mirror
Data Source
AI summary
A device is provided that includes a housing and a first motor. The first motor rotates about a first axis. A second motor is coupled to rotate the housing, the second motor rotating about a second axis. A device frame of reference is defined by the first and second axis. A mirror is rotated about the first axis by the first motor. A first and second angle measuring devices measure a first and second angle of rotation. A 3D time-of-flight camera is arranged within the housing coaxially with the first axis. The camera acquires an image of an object reflected from the mirror. A processor determines at least one first 3D coordinate of at least one point on the object, the first 3D coordinate based at least in part on the image acquired by the camera, the first angle of rotation, and the second angle of rotation.