3D Coordinate Measurement Using Segmented Reference Backdrops
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Solution Overview
Problem
Current methods for determining 3D coordinates of objects, such as those using white-light stripe projection, require complex and costly setup with reference marks and backdrops that need to be adapted for each object, leading to high preparation effort and cost, especially for large objects, and are cumbersome to reconfigure for different measurement types.
Innovation Solution
The method employs multiple, flexible reference backdrops with encoded or non-encoded marks that can be placed around the object, allowing for simpler and cost-effective measurement setup, where the positions of the marks are recorded and stored for reuse across multiple measurements, enabling accurate 3D coordinate determination without the need for extensive recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reference marks and backdrops are adapted for each object using photogrammetry methods, then measurement precision is improved, but device complexity and preparation cost increase
Solution Approach 1:
The reference system is segmented into multiple independent backdrops (at least two) that can be separately positioned and measured. Each backdrop contains reference marks that can be independently detected, allowing the complex measurement task to be divided into simpler sub-tasks while maintaining overall precision
Solution Approach 2:
The positions of reference marks on backdrops are pre-measured and stored in a database before actual object measurement. This preliminary calibration eliminates the need for complex real-time photogrammetry during measurement, reducing preparation effort while maintaining accuracy
2Reliability
If reference backdrops are attached to the object, then measurement reliability is improved, but ease of operation deteriorates due to reconfiguration requirements
Solution Approach 1:
The reference backdrops are designed as universal components that can be used with multiple different objects without attachment. The same set of backdrops can measure various objects by simply changing their positions in space, eliminating reconfiguration effort while maintaining measurement reliability through consistent reference mark geometry
Solution Approach 2:
The reference backdrops act as intermediary elements between the 3D sensor and the object being measured. They provide a stable, pre-calibrated reference frame that mediates the measurement process, allowing accurate coordinate determination without direct attachment to the object
3Area of stationary object
If multiple images are taken to cover large objects, then measurement coverage is improved, but loss of time increases due to image linking requirements
Solution Approach 1:
The system uses feedback from detecting reference marks on backdrops in each image to automatically determine sensor position and orientation. This feedback mechanism enables rapid, automated linking of multiple images covering large areas without manual intervention, reducing processing time while maintaining comprehensive coverage
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 simplifies the measurement process, reduces costs, and allows for efficient measurement of large objects by using pre-calibrated reference backdrops that can be reused, providing high accuracy and flexibility in measuring various objects with minimal setup changes.
Implementation Method 1
Several images are produced of the object, which is surrounded by several reference backdrops with coded reference marks. These images are produced such that each contains a part of the object and a part of a reference backdrop.
Implementation Method 2
EP 0 553 266 B1 discloses a method for determining the 3D coordinates of an object, comprising a scanner with which the object can be scanned. The scanner determines the 3D coordinates in its reference frame. Furthermore, a tracking system is provided that can determine the position and direction of the scanner.
Data Source
Figure 1~2
Figure 3~4
AI summary
The method involves surrounding an object (1) by a set of reference probes (2-6) that include coded reference marks (7, 8). A set of shots (10-14) are produced by the object in such a manner that a part of the object and a part of one probe are enclosed. The probes are formed longer than a measurement field of a three dimensional sensor (9), where the probes are designed in bar shape. The reference marks are automatically decoded. The shots are linked to one another by a three dimensional matching process. The reference marks are provided on rear sides of the probes.