Rigid Bar Global Calibration for Multi-Sensor Vision Systems
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Solution Overview
Problem
Current global calibration methods for Multi-Sensor Vision Measurement Systems (MSVMS) rely heavily on high-accuracy equipment and suffer from decreased calibration accuracy due to 'blind calibration areas' and numerous coordinate transformations, making them unsuitable for large working spaces.
Innovation Solution
A global calibration method using a rigid bar with adjustable length and targets, where the transformation matrix between vision sensors is computed based on the fixed position relationship between targets, allowing for higher accuracy and flexibility in large working spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional global calibration methods (homonymic coordinates unity, intermediary coordinates unity, or unique global coordinate unity) are used, then calibration can be performed, but calibration accuracy decreases due to blind calibration areas and multiple coordinate transformations
Solution Approach 1:
The patent introduces a rigid bar as an intermediary object that connects multiple vision sensors. The rigid bar carries feature points that can be observed by multiple sensors, serving as a mediator to establish direct spatial relationships between sensors without requiring multiple coordinate transformations. This intermediary approach eliminates blind calibration areas and reduces computational complexity while improving calibration accuracy.
2Measurement precision
If planar targets of huge size are used for calibration (Zhang's method), then calibration accuracy improves and coordinate transformations are reduced, but the method becomes difficult to machine and apply in large working spaces
Solution Approach 1:
The patent segments the calibration target into a rigid bar with multiple feature points distributed along its length. Instead of using a single huge planar target, the calibration object is divided into smaller, manageable components (feature points on the rigid bar) that can be easily manufactured and positioned. This segmentation maintains calibration accuracy while significantly improving ease of manufacture and applicability to large working spaces.
3Area of stationary object
If sensors are placed far away from one another in MSVMS, then each sensor's limited field of view is compensated, but global calibration becomes more difficult due to lack of common field of view
Solution Approach 1:
The rigid bar serves as a universal calibration object that can be observed by multiple vision sensors simultaneously, even when sensors are placed far apart. The feature points on the rigid bar provide common reference information that enables all sensors to be calibrated in a unified coordinate system. This multi-functional calibration approach allows sensors with non-overlapping fields of view to be accurately calibrated together.
Data Source
AI summary
The present disclosure provides a global calibration method based on a rigid bar for a multi-sensor vision measurement system, comprising: step 1, executing the following procedure for at least nine times: placing, in front of two vision sensors to be calibrated, a rigid bar fasten with two targets respectively corresponding to the vision sensors; capturing images of the respective targets by their corresponding vision sensors; extracting coordinates of feature points of the respective targets in their corresponding images; and computing 3D coordinates of each feature points of the respective targets under their corresponding vision sensor coordinate frames; and Step 2, computing the transformation matrix between the two vision sensors, with the constraint of the fixed position relationship between the two targets. The present disclosure also provides a global calibration apparatus based on a rigid bar for a multi-sensor vision measurement system. Putting the present disclosure to use can increase the accuracy of the global calibration, and also be suitable for the calibration of the multi-sensor vision system in the extremely large working space, which enlarges the application range of the present disclosure.