Markus Mettenleiter

Active laser radar for high-performance measurements

Laser scanners, or laser radars (ladar), have been used for a number of years for mobile robot navigation and inspection tasks. Although previous scanners were sufficient for low speed applications, they often did not have the range or angular resolution necessary for mapping at the long distances. Many also did not provide an ample field of view with high accuracy and high precision. In this paper we will present the development of state-of-the-art, high speed, high accuracy, 3D laser radar technology. This work has been a joint effort between CMU and K2T and Z+F. The scanner mechanism provides an unobstructed 360/spl deg/ horizontal field of view, and a 70/spl deg/ vertical field of view. Resolution of the scanner is variable with a maximum resolution of approximately 0.06 degrees per pixel in both azimuth and elevation. The laser is amplitude-modulated, continuous-wave with an ambiguity interval of 52 m, a range resolution of 1.6 mm, and a maximum pixel rate of 625 kHz. This paper will focus on the design and performance of the laser radar and will discuss several potential applications for the technology. It reports on performance data of the system including noise, drift over time, precision, and accuracy with measurements. Influences of ambient light, surface material of the target and ambient temperature for range accuracy are discussed. Example data of applications will be shown and improvements will also be discussed.

Imaging Ladar for 3-D Surveying and CAD Modeling of Real-World Environments:

To establish mobile robot operations and to realize survey and inspection tasks, robust and precise measurements of the geometry of the 3-D environment is a required basic sensor technology. For visual inspection, surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by the described active ladar, developed by Zoller and Fröhlich (Z+F). In contrast to other range-sensing devices, the Z+F system is designed for high-speed and high-performance operation in real indoor and outdoor environments, emitting a minimum of near-infrared laser energy. It integrates a single-point laser measurement system and a mechanical deflection system for 3-D environmental measurements. Experimental results are reported from surface inspections in tunnels, the generation of 3-D CAD models of a work cell in an automotive manufacturing plant, the modeling of free-form surfaces such as historic sculptures, and applications in mobile robot navigation.

Imaging laser radar for high-speed monitoring of the environment

In order to establish mobile robot operations and to realize survey and inspection tasks, robust and precise measurements of the geometry of the 3D environment is the basis sensor technology. For visual inspection, surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent range and reflectance images. The laser radar developed at Zoller + Froehlich (ZF) is an optical-wavelength system measuring the range between sensor and target surface as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to other range sensing devices, the ZF system is designed for high-speed and high- performance operation in real indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a single-point laser measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports details of the laser radar which is designed to cover requirements with medium range applications. It outlines the performance requirements and introduces the two-frequency phase-shift measurement principle. The hardware design of the single-point laser measurement system, including the main modulates, such as the laser head, the high frequency unit and the signal processing unit are discussed in detail. The paper focuses on performance data of the laser radar, including noise, drift over time, precision, and accuracy with measurements. It discusses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of tunnels, buildings, monuments and industrial environments are presented. The paper concludes by summarizing results and gives a short outlook to future work.

Imaging laser scanners for 3-D modeling and surveying applications

In order to establish mobile robot operations and to realize survey and inspection tasks, robust and precise measurements of the geometry of the 3-D environment is a required basic sensor technology. For visual inspection, surface classification, and documentation purposes, however additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by the described active laser radar developed at Zoller+Frohlich (Z+F). In contrast to other range sensing devices, the Z+F system is designed for high-speed and high-performance operation in real indoor and outdoor environments, emitting a minimum of near-infrared laser energy. It integrates a single-point laser measurement system and a mechanical deflection system for 3D environmental measurements. Experimental results are reported from surface inspections in tunnels, the generation of 3D CAD models of a work cell in an automotive manufacturing plant and the modeling of free form surfaces such as historic sculptures.

Active laser radar (LIDAR) for measurement of corresponding height- and reflectance images

For the survey and inspection of environmental objects, a non-tactile, robust and precise imaging of height and depth is the basis sensor technology. For visual inspection,surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent 3D height and 2D reflectance images. The laser radar is an optical-wavelength system, and is comparable to devices built by ERIM, Odetics, and Perceptron, measuring the range between sensor and target surfaces as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to these range sensing devices, the laser radar under consideration is designed for high speed and precise operation in both indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a laser range measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports on design details of the laser radar for surface inspection tasks. It outlines the performance requirements and introduces the measurement principle. The hardware design, including the main modules, such as the laser head, the high frequency unit, the laser beam deflection system, and the digital signal processing unit are discussed.the signal processing unit consists of dedicated signal processors for real-time sensor data preprocessing as well as a sensor computer for high-level image analysis and feature extraction. The paper focuses on performance data of the system, including noise, drift over time, precision, and accuracy with measurements. It discuses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of buildings, monuments and industrial environments are presented. The paper concludes by summarizing results achieved in industrial environments and gives a short outlook to future work.

Umgebungsvermessung anhand von 3D Geometrie mit HDR Farbe und Wärmebilddaten

Zusammenfassung Der Markt von Sensoren zur 3D Vermessung wächst. Präzise Geometrieerfassung ist Grundlage, komplementäre Informationen gewinnen an Bedeutung. Zur Minimierung von Stillständen am Messobjekt muss die Sensorik viele Primärinformationen erfassen. Die an der TU München (LSR) entwickelte Laserkamera erzeugte räumliche Tiefen- und Reflektivitätsbilder. Detailliertere Informationen benötigen jedoch weitere physikalische Messgrößen. Z+F entwickelt Messtechnologie und registriert außerdem HDR- und Wärmebilddaten präzise zu den 3D Daten. Die Geometrie wird Träger komplementärer Informationsebenen.