Six-DOF Measurement via Integrated Laser and Camera
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Solution Overview
Problem
Current measurement systems for determining the six degrees of freedom of an object, especially moving objects, face challenges in achieving high accuracy, particularly in depth measurement, and are complex to implement, especially when dealing with moving objects that require multiple cameras or devices.
Innovation Solution
The system incorporates an angle and distance measuring device with a laser beam and a reflector, along with an optically detectable additional element that allows for the determination of the roll angle, enabling the calculation of six degrees of freedom using a single camera and known algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photogrammetric methods with multiple cameras are used to determine six degrees of freedom of moving objects, then measurement accuracy is improved, but device complexity and data management complexity increase
Solution Approach 1:
The patent combines multiple measurement functions (direction measurement, distance measurement, and roll angle measurement) into a single integrated measuring device. The device integrates a direction measuring device (theodolite), a distance measuring device (laser rangefinder), and a camera system with image processing capabilities, allowing all six degrees of freedom to be measured by one device rather than multiple separate systems
Solution Approach 2:
The measuring device performs multiple functions simultaneously: it measures horizontal and vertical angles, distance to the reflector, and roll angle through image processing. The single device serves as both a theodolite, laser rangefinder, and camera system, eliminating the need for multiple specialized devices and simplifying the overall measurement system
2Device complexity
If a single camera is used to determine six degrees of freedom, then device complexity is reduced, but measurement accuracy in depth determination deteriorates
Solution Approach 1:
The patent merges the camera system with a laser distance measuring device and a theodolite in a single integrated unit. The direction measuring device provides accurate angular measurements, the distance measuring device provides precise range data, and the camera with image processing provides roll angle information, collectively compensating for the limitations of using a single camera alone
Solution Approach 2:
The patent introduces an additional optically detectable element (such as a patterned marker or reflective feature) on the reflector that serves as an intermediary for roll angle measurement. This element provides optical features that the camera can detect and process to determine the roll angle, while the laser distance measuring device and theodolite provide the remaining spatial information, collectively achieving six degrees of freedom measurement
3Measurement precision
If laser trackers with distance measuring devices are used to determine five degrees of freedom, then measurement accuracy is improved, but the ability to determine roll angle deteriorates
Solution Approach 1:
The patent combines the traditional laser tracker functionality (direction and distance measurement for five degrees of freedom) with an integrated camera system and image processing capabilities. The camera captures images of the additional optically detectable element on the reflector, and the image processing determines the roll angle from these images, adding the sixth degree of freedom to the existing five-degree-of-freedom measurement capability
Solution Approach 2:
The patent changes the measurement parameters by adding optical parameter detection through the camera system. While the laser tracker measures spatial coordinates and angles, the camera system detects optical parameters (image coordinates, pattern orientation) of the additional element on the reflector, transforming these optical parameters into roll angle information to complete the six degrees of freedom measurement
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 measurement accuracy to match or exceed existing systems while simplifying the setup by using known devices and allowing for precise determination of an object's position and orientation, including roll angle, suitable for both stationary and moving objects.
Implementation Method 1
The reflector is a retroreflector (corner cube reflector or cube corner prism) whose apical tip is replaced by an apical opening (corner cube reflector) or apical face (corner cube prism)
Implementation Method 2
another part of the measuring beam passes through the reflector, exits through the apical opening or surface and hits a light-sensitive surface arranged behind the reflector, for example a CCD (charge coupled device, as is customary in a digital camera) or PSD (position sensitive device)
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
The system has an optically detectable addition unit (10) which is stationary relative to the angle and distance measurement apparatus and is detected from an object (3). A computer is equipped for computing five degrees of freedom of the reflector or the object, from the measurement data produced by the angle and distance measurement apparatus and by the light-sensitive surface (7). The computer computes the sixth degree of freedom of the reflector or the object from measurement data obtained by the detection of the addition unit.