Looking at owls from two angles; A study of wing anatomy of the barn owl Tyto alba with two different multi camera systems

Abstract

Barn owls have undergone many adaptations to optimize flight behaviour for catching small rodents in environments where visibility is impaired. These birds have, for example, developed structures that reduce noise production during flight and they have adapted wing form to slow flight. For such reasons, the wing of the barn owl serves – in a biomimetic sense - as a role model for the construction of airplane wings. The biological part of such a project is to exactly measure wing form. Measuring under life conditions has turned out to be a difficult problem, because wing form in bird flight is not constant. The DLR Göttingen and the RWTH Aachen have developed two different systems which allow high precision measurements of the owl wings during free flight. Both systems rely on multiple cameras that record the barn owl during flight. The first system uses a fine random pattern of light points which is projected onto the wing surfaces. Each surface is being recorded by two synchronised high speed cameras. By correlating the dot patterns recorded by the two cameras a 3D model can be generated. The second approach uses a number of laser sheets, to create cross sections of the wing. Line lasers are affixed to a frame so that unbroken laser lines are projected onto the wing surface perpendicular to the flight path. The shape of the laser lines on the wing surface is recorded with single-lense reflex cameras, and three-dimensional shape of the upper and lower side of the wing is reconstructed. The weaknesses and the strengths of both approaches will be discussed and compared.