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Journal ArticleDOI

Improvement of sensor accuracy in the case of a variable surface reflectance gradient for active laser range finders

TL;DR: This paper presents two heuristic models to improve the sensor accuracy in the case of a variable surface reflectance gradient and simulation results are presented to show the quality of the correction and the resulting accuracy.
Abstract: In active laser range finders, the computation of the (x, y, z) coordinates of each point of a scene can be performed using the detected centroid p~ of the image spot on the sensor. When the reflectance of the scene under analysis is uniform, the intensity profile of the image spot is a Gaussian and its centroid is correctly detected assuming an accurate peak position detector. However, when a change of reflectance occurs on the scene, the intensity profile of the image spot is no longer Gaussian. This change introduces a deviation /spl Delta/p on the detected centroid p~, which will lead to erroneous (x, y, z) coordinates. This paper presents two heuristic models to improve the sensor accuracy in the case of a variable surface reflectance gradient. Simulation results are presented to show the quality of the correction and the resulting accuracy.
Citations
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Journal ArticleDOI
TL;DR: A broad survey of developments in active vision in robotic applications over the last 15 years is provided, e.g. object recognition and modeling, site reconstruction and inspection, surveillance, tracking and search, as well as robotic manipulation and assembly, localization and mapping, navigation and exploration.
Abstract: In this paper we provide a broad survey of developments in active vision in robotic applications over the last 15 years. With increasing demand for robotic automation, research in this area has received much attention. Among the many factors that can be attributed to a high-performance robotic system, the planned sensing or acquisition of perceptions on the operating environment is a crucial component. The aim of sensor planning is to determine the pose and settings of vision sensors for undertaking a vision-based task that usually requires obtaining multiple views of the object to be manipulated. Planning for robot vision is a complex problem for an active system due to its sensing uncertainty and environmental uncertainty. This paper describes such problems arising from many applications, e.g. object recognition and modeling, site reconstruction and inspection, surveillance, tracking and search, as well as robotic manipulation and assembly, localization and mapping, navigation and exploration. A bundle of solutions and methods have been proposed to solve these problems in the past. They are summarized in this review while enabling readers to easily refer solution methods for practical applications. Representative contributions, their evaluations, analyses, and future research trends are also addressed in an abstract level.

398 citations


Cites background or methods from "Improvement of sensor accuracy in t..."

  • ...Khali et al. present two heuristic models to improve the sensor accuracy in the case of a variable surface reflectance (Khali et al. 2003)....

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  • ...present two heuristic models to improve the sensor accuracy in the case of a variable surface reflectance (Khali et al. 2003)....

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Journal ArticleDOI
TL;DR: This article deals with the design, the control, and the measurement results of a scanning triangulation sensor, in which the illumination and reflection paths of the sensor are scanned by a fast steering mirror (FSM).
Abstract: In scan-based 3-D systems, the achievable measurement time is strongly restrained by the moving mass. This limitation can be relaxed, by scanning the optical path instead of moving the entire sensor, such that a higher measurement speed can be achieved. This article deals with the design, the control, and the measurement results of a scanning triangulation sensor, in which the illumination and reflection paths of the sensor are scanned by a fast steering mirror (FSM). The system architecture is determined using ray-tracing simulations, such that the performance of the scanning system can be determined in advance. To scan the area of interest with the FSM, conventional raster trajectories and Lissajous trajectories are employed, which provide an early overview of the scan area. For tracking these trajectories, PID and dual-tone controllers are used, respectively. The experimental results demonstrate that for both scan trajectories, the sample can be captured correctly, with a frame rate of 1 frame/s, a maximum spatial resolution of 130 $\mu \text{m}$ , and a field of view of $11.5\,\,\times 18.5\,\,{\mathrm{ mm}}^{2}$ .

26 citations

Journal ArticleDOI
TL;DR: The sensor design integrates principles of laser triangulation and objective laser speckle measurement into a single device and provides an in-plane and out-of-plane resolution of 3 µm and 1 µm, respectively.
Abstract: This paper presents the development of a compensation-based laser sensor system, capable of sensing in-plane as well as out-of-plane displacements of a target. The sensor design integrates principles of laser triangulation and objective laser speckle measurement into a single device and provides an in-plane and out-of-plane resolution of 3 µm and 1 µm, respectively. The compensation-based operation keeps the variation of distance and lateral position relative to the target close to zero by actively following the target motion using feedback control. This enables a large operation range of the resulting sensing and tracking system, limited only by the range of the actuation system. Accurate tracking of target motions is demonstrated in an area of 1×1mm2 with a small remaining spatial rms tracking error between 8.75 µm and 13.25 µm.

4 citations

Journal ArticleDOI
TL;DR: A new practical calibration method of a stripe laser imaging system for the 3-D shape measurement of an object has an integrated mathematical approach for the camera imaging parameters and the stripe laser light plane.
Abstract: This article presents a new practical calibration method of a stripe laser imaging system for the 3-D shape measurement of an object. The proposed calibration method has an integrated mathematical approach for the camera imaging parameters and the stripe laser light plane. A simple calibration block with a checkerboard pattern attached is used that has different inclination angle at each face. Because the same scene with the laser light ON and OFF is used for the integrated calibration of the camera and the laser light plane, the calibration process is fast and efficient and the resultant calibration parameters are consistent. The experimental results demonstrated the performance of the proposed calibration method.

2 citations


Cites background from "Improvement of sensor accuracy in t..."

  • ...The laser imaging system is a type of noncontact and active 3-D measurement system that projects a collimated laser light of distinct frequency on a target object and measures the deformation of the laser light according to the shape of the object through a camera [4]–[6]....

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Journal ArticleDOI
TL;DR: This article presents a sensor correction model that relies on clustered WSN that employs autonomous selection mechanism to elect cluster heads by applying a stochastic competition between cluster members while maintaining the underlying physical properties as the bases to locate competition winner.
Abstract: Wireless Sensor Networks (WSN) are growing in popularity and penetrating newer fields of applications more than ever. Gradually, we are relying on WSNs to perform more complex tasks with increasing cognitive abilities. At the core of the WSN research transpires, the need is to achieve accurate sensing at real-time. Unfortunately, confidence in sensors’ readings decreases in harsh environments and as a result of normal reading errors, message loss, or even low battery operations. The complex problem of dealing with corrections and in some cases shredding the outcome of entire deployments leads to loss of effort, time, and money. Classic approaches for correcting laboratory experiments like curve fitting and least square are well known and have been established for decades. But little research attempts have been made to correct and recalibrate sensors observations in real-time. Furthermore, classic approaches for correcting sensor observations require higher interaction between sensors to a level we...

1 citations

References
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Journal ArticleDOI
TL;DR: A new geometrical arrangement is proposed to improve performances of optical triangulation, which allows considerable reduction of the optical head size compared with usual geometries, so the shadow effects are reduced proportionally.
Abstract: A new geometrical arrangement is proposed to improve performances of optical triangulation Two scanners in synchronization allow a linear position sensor to be used for surface topography measurement Besides a large increase in speed of measurement (approximately megahertz), the new geometry allows considerable reduction of the optical head size compared with usual geometries, so the shadow effects are reduced proportionally It also provides a means to obtain a very large field of view without compromising on resolution Geometrical analysis and experimental results are presented

450 citations


"Improvement of sensor accuracy in t..." refers background in this paper

  • ...The considered system is based on synchronized scanners for which several geometries can be found in [2]....

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  • ...Because of practical considerations, we will focus our attention, without loss of generality, on an autosynchronized system [2]....

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Journal ArticleDOI
TL;DR: Speckle noise is shown to constitute a fundamental limit to laser range finders based on triangulation and a model is derived that relates the magnitude of this noise to the optical geometry used.
Abstract: Speckle noise is shown to constitute a fundamental limit to laser range finders based on triangulation. A model is derived that relates the magnitude of this noise to the optical geometry used. Synchronized laser scanners are shown to have inherent speckle noise reduction properties. Experimental results are presented.

142 citations

Journal ArticleDOI
TL;DR: In this paper, a simple and effective peak detector is proposed, which gives in real-time the position and amplitude of a peak in a digital signal to a precision better than one pixel.

111 citations


"Improvement of sensor accuracy in t..." refers background in this paper

  • ...The importance of in system design appears when using a sub-pixel resolution peak detector [4], where it is important to have an image of the beam that is much wider than a pixel on the detector....

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Proceedings ArticleDOI
14 Nov 1988
TL;DR: In this article, the authors describe some practical considerations for the design and implementation of triangulation-based 3D range sensors with emphasis on the latter triangulations technique, and some applications and results are presented.
Abstract: The Laboratory for Intelligent Systems of the Division of Electrical Engineering of the National Research Council of Canada is intensively involved in the development of laser-based three-dimensional vision systems and their applications. Two basic systems have been invented. One, based on a double aperture mask in front of a CCD camera, has been developed for robotic applications and control. The other technique is based on an auto-synchronized scanning principle to provide accurate, fast, and reliable 3-D coordinates. Using the latter method, several prototypes have been developed for the acquisition of 3-D data of objects and for inspection. This paper will describe some practical considerations for the design and implementation of triangulation-based 3-D range sensors with emphasis on the latter triangulation technique. Some applications and results will be presented.

79 citations

Proceedings ArticleDOI
22 Oct 1993
TL;DR: In this article, a calibration procedure adapted to a range camera intended for space applications is presented. But the accuracy of the range camera is limited by the fact that the field of view is 30 degree(s) X 30 degree (s).
Abstract: This paper presents a calibration procedure adapted to a range camera intended for space applications. The range camera, which is based upon an auto-synchronized triangulation scheme, can measure objects from about 0.5 m to 100 m. The field of view is 30 degree(s) X 30 degree(s). Objects situated at distances beyond 10 m can be measured with the help of cooperative targets. Such a large volume of measurement presents significant challenges to a precise calibration. A two-step methodology is proposed. In the first step, the close-range volume (from 0.5 m to 1.5 m) is calibrated using an array of targets positioned at known locations in the field of view of the range camera. A large number of targets are evenly spaced in that field of view because this is the region of highest precision. In the second step, several targets are positioned at distances greater than 1.5 m with the help of an accurate theodolite and electronic distance measuring device. This second step will not be discussed fully here. The internal and external parameters of a model of the range camera are extracted with an iterative nonlinear simultaneous least-squares adjustment method. Experimental results obtained for a close-range calibration suggest a precision along the x, y and z axes of 200 micrometers , 200 micrometers , and 250 micrometers , respectively, and a bias of less than 100 micrometers in all directions.

46 citations