Buse H.,Fachhochschule Oldenburg Ostfriesland Wilhelmshaven |
Ernst S.,Fachhochschule Oldenburg Ostfriesland Wilhelmshaven |
Parkin R.M.,Loughborough University |
Kreitlow H.,Fachhochschule Oldenburg Ostfriesland Wilhelmshaven
Lasers in Engineering | Year: 2011
It is especially necessary in the field of laser direct writing lithography to gain exact knowledge about the shape and characteristics of the utilized laser beam, whilst a homogeneous power distribution is an essential parameter for sufficient and reproducible results in surface structuring. A novel method is presented to characterize the power distribution of a focussed laser beam by scanning its cross-sectional plane with an optical fibre tip that is commonly used for scanning near field optical microscopy (SNOM). This novel method is capable of characterizing laser beams diverging from very small focal apertures with a high resolution. This method can improve the research and development (R&D) of either an academic institute or a player in the optical industry regarding such things as the development of the next generation of optical storage. In contrast to the established profiling techniques and commercial products, the field of application includes the characterization of beams diverging from the lenses of DVD or BluRay© devices with numerical apertures (NA) in the range of 0.6 up to 0.85. Laser beams emerging from modified optical pickup units (OPU) have been successfully characterized using this novel method. © 2011 Old City Publishing, Inc.
Menzel R.,Free University of Berlin |
Kirbach A.,Free University of Berlin |
Haass W.-D.,Fachhochschule Oldenburg Ostfriesland Wilhelmshaven |
Fischer B.,Fachhochschule Oldenburg Ostfriesland Wilhelmshaven |
And 9 more authors.
Current Biology | Year: 2011
Humans draw maps when communicating about places or verbally describe routes between locations. Honeybees communicate places by encoding distance and direction in their waggle dances . Controversy exists not only about the structure of spatial memory but also about the efficiency of dance communication [2-5]. Some of these uncertainties were resolved by studies in which recruits' flights were monitored using harmonic radar [6, 7]. We asked whether the two sources of vector information - the previously learned flight vector to a food source and the communicated vector - are represented in a common frame of spatial reference. We found that recruits redirect their outbound flights and perform novel shortcut flights between the communicated and learned locations in both directions. Guidance by beacons at the respective locations or by the panorama of the horizon was excluded. These findings indicate a spatial reference based on either large-scale vector integration or a common geocentric map-like spatial memory. Both models predict a memory structure that stores the spatial layout in such a way that decisions are made according to estimated distances and directions. The models differ with respect to the role of landmarks and the time of learning of spatial relations. © 2011 Elsevier Ltd.