Strategy for Determining the Stochastic Distance Characteristics of the 2D Laser Scanner Z + F Profiler 9012A with Special Focus on the Close Range.

Kinematic laser scanning with moving platforms has been used for the acquisition of 3D point clouds of our environment for many years. A main application of these mobile systems is the acquisition of the infrastructure, e.g., the road surface and buildings. Regarding this, the distance between laser scanner and object is often notably shorter than 20 m. In the close range, however, divergent incident laser light can lead to a deterioration of the precision of laser scanner distance measurements. In the light of this, we analyze the distance precision of the 2D laser scanner Z + F Profiler 9012A, purpose-built for kinematic applications, in the range of up to 20 m. In accordance with previous studies, a clear dependency between scan rate, intensity of the backscattered laser light and distance precision is evident, which is used to derive intensity-based stochastic models for the sensor. For this purpose, a new approach for 2D laser scanners is proposed that is based on the static scanning of surfaces with different backscatter. The approach is beneficial because the 2D laser scanner is operated in its normal measurement mode, no sophisticated equipment is required and no model assumptions for the scanned surface are made. The analysis reveals a lower precision in the range below 5 m caused by a decreased intensity. However, the Z + F Profiler 9012A is equipped with a special hardware-based close range optimization partially compensating for this. Our investigations show that this optimization works best at a distance of about 2 m. Although increased noise remains a critical factor in the close range, the derived stochastic models are also valid below 5 m.

Design, realization, and characteristics of a transition edge bolometer for sub-millimeter wave astronomy.

The large array bolometer camera is scheduled to succeed its semiconducting predecessor at the Atacama pathfinder experiment. It shall be an array of 300 transition edge sensors operated at a temperature of about 0.25 K, provided by a (3)He evaporation cooler and a pulse tube refrigerator. The instrument will be read out by a superconducting quantum interference device time domain multiplexer. The design and realization of a suitable detector for this instrument is described. Based on sensitivity demands derived from the background limit, the thermal and electrical designs for a spider-web bolometer are deduced. The theoretical predictions are compared to experimental results. The pixel design yields a background-limited performance for background loads corresponding to blackbody sources between 77 K and 300 K and a partially effective anti-aliasing filter for the intended multiplexed readout.