Schnelle Entfernungsmessung für Laserscanner

This contribution describes the principle of distance measurement by means of a modulated laser beam and phase detection. The most critical impacts on accuracy and reliability like noise, modal structure of the laser, and crosstalk are qualified and quantified. Counteractive measures to reduce their influence are shown. The realized distance measuring module enables to measure distances in a some ten meter range with frequencies up to 1 MHz. Some results of a laser scanner for clearance measurement of railway lines are shown

Novel geometry for a high speed outdoor laser scanning system

Today, the phase shifting technique is still the fastest and most accurate measurement method for laser scanners in the meter and some 10 meters range. A major handicap for outdoor applications such as railway measurement systems is the influence of optical cross talk caused by pollution of the optical surfaces. This effect is closely linked to the multi target response of phase shifting systems which is analyzed quantitatively. It is shown that optical cross talk is a major cause for nonlinearities when dark objects are measured. To overcome this disadvantage a sealed cover with light traps was designed for a 350 degree scanner to protect the most critical surface of the scan mirror and to absorb the stray light from the polluted outer surfaces. The sampling rate of this system can be doubled without loss of measurement accuracy by using a new scan geometry with two fibre coupled measurement heads on each end of a hollow scan axis with a double sided scan mirror

Challenges of radiotherapy: Report on the 4D treatment planning workshop 2013

This report, compiled by experts on the treatment of mobile targets with advanced radiotherapy, summarizes the main conclusions and innovations achieved during the 4D treatment planning workshop 2013. This annual workshop focuses on research aiming to advance 4D radiotherapy treatments, including all critical aspects of time resolved delivery, such as in-room imaging, motion detection, motion managing, beam application, and quality assurance techniques. The report aims to revise achievements in the field and to discuss remaining challenges and potential solutions. As main achievements advances in the development of a standardized 4D phantom and in the area of 4D-treatment plan optimization were identified. Furthermore, it was noticed that MR imaging gains importance and high interest for sequential 4DCT/MR data sets was expressed, which represents a general trend of the field towards data covering a longer time period of motion. A new point of attention was work related to dose reconstructions, which may play a major role in verification of 4D treatment deliveries. The experimental validation of results achieved by 4D treatment planning and the systematic evaluation of different deformable image registration methods especially for inter-modality fusions were identified as major remaining challenges. A challenge that was also suggested as focus for future 4D workshops was the adaptation of image guidance approaches from conventional radiotherapy into particle therapy. Besides summarizing the last workshop, the authors also want to point out new evolving demands and give an outlook on the focus of the next workshop