Böhlerstern
The Böhlerstern is a transfer of the Siemens star into the third dimension in order to determine the resolution of three-dimensional measuring laser scanners .
The Böhlerstern is named after Wolfgang Böhler , who invented it and made it from cardboard for the first time.
The first Böhlerstern ever built consists of a 30 × 30 cm front and background plate. The front and background panels are 5 cm apart and run strictly parallel to each other. The front panel has cutouts in a star shape from its center. The 24 recesses alternate with just as many bars of the same shape and size. As the distance from the center increases , the gap between the webs increases or the width of the webs increases.
If the Böhlerstern is scanned vertically from the front with a laser scanner, it should ideally be possible to determine as many measuring points on the front plate as on the background plate. Two planes can be approximated from the measurement points on the front or background plate, which ideally have a distance that coincides with the real distance between the plates. However, since a laser beam is not infinitely thin, but has a finite thickness due to the beam divergence , the gap, which becomes smaller towards the center, increasingly acts as an obstacle for the laser beam and it no longer reaches the background plate.
With a Böhlerstern, in analogy to the Siemens star in photography, the three-dimensional resolving power of different laser scanners can be assessed and compared. The different distribution of the measuring points on the plates and the effect that measuring points are also determined between the plates provides information about the performance of the laser scanner used.
literature
- W. Böhler, M. Bordas Vicent, A. Marbs: Investigating Laser Scanner Accuracy - The International Archives of Photogrammetry . In: Remote Sensing and Spatial Information Sciences . Vol. XXXIV, Part 5 / C15. Antalya 2003, p. 696-701 .
- U. Huxhagen, F. Kern, B. Siegrist: Proposal for a TLS test guideline . In: T. Luhmann, Ch. Müller (Ed.): Photogrammetry, laser scanning, optical 3D measurement technology . Wichmann, Heidelberg 2009, p. 3-12 .