Structured-light 3D scanner
A structured-light 3D scanner is a device used to capture the three-dimensional shape of an object by projecting light patterns—such as grids or stripes, onto its surface.
Structured-light 3D scanning is widely employed in fields such as industrial design, quality control, cultural heritage preservation, augmented reality gaming, and medical imaging.
Compared to laser-based 3D scanning, structured-light scanners use non-coherent light sources, such as LEDs or projectors, which enable faster data acquisition and eliminate potential safety concerns associated with lasers.
Projecting a narrow band of light onto a three-dimensional surface creates a line of illumination that appears distorted when viewed from perspectives other than that of the projector.
A more efficient and versatile approach involves projecting patterns composed of multiple stripes or arbitrary fringes simultaneously.
This method enables the acquisition of numerous data points at once, significantly improving scanning speed.
[citation needed] By analyzing the displacement of these stripes, the three-dimensional coordinates of surface details can be accurately determined.
Example methods include the use of infrared light or of extremely high framerates alternating between two exact opposite patterns.
The parameters of the camera as well as its orientation in space can be determined by a series of calibration measurements, using photogrammetric bundle adjustment.
In many practical implementations, series of measurements combining pattern recognition, Gray codes and Fourier transform are obtained for a complete and unambiguous reconstruction of shapes.
[5] Double reflections and inter-reflections can cause the stripe pattern to be overlaid with unwanted light, entirely eliminating the chance for proper detection.
It is also hard to handle translucent materials, such as skin, marble, wax, plants and human tissue because of the phenomenon of sub-surface scattering.
Recently, there has been an effort in the computer vision community to handle such optically complex scenes by re-designing the illumination patterns.
[6] These methods have shown promising 3D scanning results for traditionally difficult objects, such as highly specular metal concavities and translucent wax candles.
