3D Coordinate Determination Using TOF and Structured Light
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Solution Overview
Problem
Existing methods for determining 3D coordinates of objects are slow, expensive, and prone to ambiguity due to ambient light interference, especially in outdoor and varying weather conditions, making them unsuitable for applications like earthwork operations where quick and reliable measurements are needed.
Innovation Solution
Incorporating a time-of-flight (TOF) range camera with a structured-light measurement system to capture range images that provide distance information, which helps resolve ambiguities and improve the accuracy of 3D coordinate determination by combining with 2D image data from photo sensor array cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If structured-light measurement with multiple pattern sequences is used, then measurement precision is improved, but measurement time increases significantly
Solution Approach 1:
The patent combines TOF range image data with structured-light measurement data into a unified 3D coordinate determination system. The TOF camera captures distance information for all points simultaneously, while the structured-light system provides high-precision measurements for visible points, creating a hybrid system that achieves both speed and accuracy.
Solution Approach 2:
The system performs preliminary measurement with the faster TOF range camera to obtain initial 3D coordinates for all points. Then, only the subset of points visible to both cameras undergoes the more time-consuming structured-light measurement process, significantly reducing total measurement time while maintaining precision.
2Reliability
If structured-light measurement is used in outdoor conditions, then measurement precision deteriorates due to ambient light, but the system remains expensive and slow
Solution Approach 1:
The TOF camera acts as an intermediary system that operates independently of ambient visible light conditions. It captures distance information using time-of-flight measurement, which is not affected by ambient light. This data serves as a reliable foundation that complements the structured-light measurements, enabling operation in outdoor environments.
Solution Approach 2:
The system changes the measurement parameter from purely optical reflection-based measurement (structured light) to include time-based distance measurement (TOF). This parameter change allows the system to operate reliably under varying ambient light conditions, as TOF measurement is insensitive to light intensity and color.
3Measurement precision
If multiple PSA cameras with high resolution are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the measurement task into two parts: the TOF camera captures the entire scene at once providing coarse 3D information for all points, while the structured-light system with PSA cameras focuses only on specific regions or points of interest requiring high precision. This segmentation reduces the burden on each individual camera system.
Solution Approach 2:
The system adds the time dimension to the traditional optical measurement by incorporating TOF measurement. This temporal dimension provides depth information that complements the spatial resolution of the PSA cameras, allowing the system to achieve complete 3D coverage without requiring multiple high-resolution cameras from different angles.
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 enables faster, cost-effective, and reliable determination of 3D coordinates, reducing the need for multiple pattern sequences and enhancing measurement precision under various environmental conditions.
Implementation Method 1
Incorporating a time-of-flight (TOF) range camera with a structured-light measurement system to capture range images that provide distance information
Implementation Method 2
the knowledge of the device distance and the illumination angle permits a triangulation of the 3D coordinate of the correlated object point
Data Source
Figure 1a~2
Figure 3a~3d
Figure 4a~4b
AI summary
The invention relates to an optical measuring device (1) for determining 3D coordinates of an object (2), comprising a projector device (11) for illuminating the object (2) with at least one predefined pattern (10); at least one PSA camera (12, 12') for capturing a 2D image (120) of the pattern (10) as reflected from the object (2); computing means (18) for measuring a sequence of brightness values (180, 180', 180'') of at least one 2D image point (121, 121') from the 2D images (120, 120'); and calculating a 3D coordinate (21) of an object point (20) which is correlated with the measured sequence of brightness values (180, 180', 180'') of the 2D image point (121, 121'), characterized by a TOF camera (13) for capturing at least one range image (133) of the object (2), the range image (133) including distance information (133') of the object (2) for the dissolution of ambiguity in calculating the 3D coordinate. The invention also relates to a method for determining 3D coordinates of an object (2) by said optical measuring device (1), the method comprising a structured-light measurement and capturing with a TOF camera (13) at least one range image (133) of the object (2), the range image (133) including distance information (133') of a plurality of points of the object (2).