Type Of Rangefinder Research Articles

Comparison of Time-of-Flight and Phase-Shift TLS Intensity Data for the Diagnostics Measurements of Buildings.

In recent years, the terrestrial laser scanning system (TLS) has become one of the most popular remote and nondestructive testing (NDT) methods for diagnostic measurements of buildings and structures as well as for the assessment of architectural heritage. Apart from 3D coordinates, the power of a laser beam backscattered from the scanned object can be captured by TLS. The radiometric information of the point cloud, called “intensity”, can provide information about changes in the physio–chemical properties of the scanned surface. This intensity can be effectively used to detect defects in the surfaces of walls, such as cracks and cavities, moisture, biodeterioration (mosses and lichens) or weathered parts of the wall. Manufacturers of TLS mainly use two different principles for distance measurement, time-of-flight (TOF) and phase-shift (PS). The power of energy in both types of rangefinders might be absorbed or reflected in a slightly different way and provide more or less detailed radiometric point cloud information. The main aim of this investigation is to compare TOF and PS scanners in the context of using TLS intensity data for the diagnostics of buildings and other structures. The potential of TLS intensity data for detecting defects in building walls has been tested on multiple samples by two TOF (Riegl VZ400i, Leica ScanStation C10) and two PS (Z + F 5016 IMAGER, Faro Focus3D) scanners.

An advanced rangefinder equipped with a new image sensor with the ability to detect the incident angle of a light stripe

This paper describes an advanced rangefinder equipped with a new image sensor capable of detecting the incident angle of a light stripe. The triangulation-based rangefinding approach is the one that is most widely used. However, ordinary triangulation-based rangefinders have hitherto been limited to measuring Lambertian objects because triangulation-based approaches are particularly susceptible to the object's surface reflectivity. We previously proposed a new type of rangefinder that relaxed the above-mentioned restrictions on ordinary rangefinders. However, the previous rangefinder had two unsolved problems: the image sensor used for the rangefinder was one-dimensional, and the experimental verification of the applied object was limited to specular objects and Lambertian objects. We here propose a rangefinder with an area image sensor, extending the capabilities of our previous sensor, which is capable of detecting the two-dimensional incident position and angle of incident light. We have made a prototype rangefinder, and experimentally compared it to our previous rangefinder and to a conventional rangefinder. The experimental results of the proposed rangefinder demonstrate that it measures three-dimensional (3D) shapes objects faster than the previous rangefinder and produces the same high level of accuracy in measuring 3D shapes regardless of the surface reflectance of the given objects.

Detection of Edges Using Range Information

Range data provide an important source of 3-D shape information. This information can be used to extract jump boundaries which correspond to occluding boundaries of objects in a scene and ``edges'' which correspond to points lying between significantly different regions on the surface of objects. We are mainly interested in range data obtained from sensors such as lasers. The main problem with this type of range finder is the fact that the accuracy of the measurements depends on the power of the signal that reaches the receiver. This study describes how a range edge detection procedure can be designed that has low sensitivity to noise and imbeds all the knowledge available on the range measurement accuracy.

A Wide-field Scanning Triangulation Rangefinder for Machine Vision

This paper describes the design, construction, and measured performance of an experimental scanning laser rangefinder. The instrument uses active triangulation and employs an optical bandpass filter to minimize the effects of ambient illumination. Its use of a single photodetecting element, a photomultiplier, is a unique feature among scanning triangulation rangefinders. A novel scanning configuration based on spherical coordinates is employed, resulting in an extremely large field of view. Nearly 75% of the surrounding solid angle is accessible. Reasonably high speed and accuracy are obtained. The typical error in range at a range of 50 in. is .12 in. The typical error in either of the two angular coordinates is .03°. The maximum instantaneous rate of acquisition of range samples is 500 Hz. Much higher speed and accuracy appear achievable with various modifications and improvements. This type of rangefinder appears most useful in automatic surveillance and robot navigation applications, because of its large field of view.