Scanner Technologies

Unstructured objects like reliefs or sculptures are recorded today as point clouds. The geometry represents a polygonal surface and is named mesh. The surface of an object is approximated by small triangles. Radiometric information (color) can be store by RGB color values. The following technologies exist:

Laser Scanning
Structured Light
PhotogrammetrY
Time-of-Flight Cameras
Depth Cameras

Criteria for selecting the appropriate methode are the shape of the object, measurement volume, accessibility, light and surface properties, required accuracy and finally an efficient handling under budget consideration.

Laser scanning covers a measurement volume of about 1-1000 m within an accuracy between millimtre and centimetre. Combination between laserlight and RGB cameras cover distances from near zero up to a few metres and can achieve extreme high accuracy within a few micrometres. Time-of-Flight cameras are cioming with high frame rates but a poor resolution. Designed as human natural interfaces, depth cameras from Primesene with modifications as Kinect or ASUS Xtion are an oppurtunity. Using those devices as 3D scanner providing a frame rate of 30fps with a distance from 0.4 up to 10m. The accuracy shows about 1cm. The most customizable method is Photogrammetry. In Computer Vision the method is known as Structure from Motion or Structure from Stereo. Distance and Accuracy depend on camera parameter and exposure arrangement.

Pictures:
Top left: CamCube Time-of-Flight Kamera
Top right: Structured Light Scanner Breukmann
Right top: Faro Laserscanner