The principle of the structured light method
The structured light method is an optical measurement technique for the three-dimensional detection of object surfaces. A known light pattern, often in the form of stripes or grids, is projected onto the surface of the object to be measured. The physical principles of the structured light method are therefore based on the interaction between light and matter. When a light pattern hits a surface, it is modulated according to the topography of this surface. This modulation leads to specific changes in the amplitude, phase and polarization of the reflected light, which can be detected and analysed by sensors.
In the case of the Revopoint MetroX, it is a device that uses structured light in conjunction with precise triangulation. It projects a pattern of 62 blue lines onto the object surface and captures the resulting point clouds at high speed without the need for markers on the object. This method makes it possible to create detailed 3D models of objects by analyzing the distortions of the projected pattern. The system is calibrated so that the spatial direction is known for each pixel on the camera sensor. When a projected strip of light hits a surface, it is deformed by height differences. The camera recognizes this deformation and the system can determine the exact spatial position of the reflected point using geometric calculations – usually by means of triangulation.
In order to reliably determine the spatial depth, several patterns are usually projected one after the other. The temporal sequence allows each pixel to be clearly assigned in space, which reduces blurring and ambiguity. In the specific case of the Metrox, high-resolution optics and calibrated sensors are also used to generate the resulting point cloud as accurately and with as little noise as possible.
Another part of the process is the exact calibration of the entire system. Both the position of the projector and the cameras must be known exactly in relation to each other. This calibration ensures that the pixels registered by the sensor can be precisely correlated with the projected patterns. This is the only way to calculate correct 3D coordinates from the 2D image data. The accuracy of the structured light method depends heavily on external conditions. High contrast of the pattern, low ambient lighting and a matt, non-reflective surface of the object improve detection. Shiny, transparent or very dark materials, on the other hand, can lead to reflection losses, scattered light or shadows, which limits the measurement accuracy.
The Revopoint MetroX uses this method to generate dense point clouds with high surface accuracy, which makes it ideal for applications in quality control, reverse engineering or 3D documentation. The generated point cloud is then further processed in a software environment, where smoothing, noise suppression and, if necessary, conversion into a polygon mesh take place. This shows that despite high theoretical precision, certain details can be lost due to optical and physical effects, as we will see in a moment.
- 1 - Introduction, unboxing and features
- 2 - The principle of the structured light method
- 3 - The functional principle of point clouds
- 4 - Triangulation of the point clouds in a mesh
- 5 - 3D for Dummies: One-Click-Solution
- 6 - Limits of the system and the effective accuracy
- 7 - Summary and conclusion
- 8 - Appendix: Datasheet
- 9 - Appendix: Quick Start Quide
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