Vera Tyrsa

Surface recognition improvement in 3D medical laser scanner using Levenberg-Marquardt method

The 3D measurements of the human body surface or anatomical areas have gained importance in many medical applications. Three dimensional laser scanning systems can provide these measurements; however usually these scanners have non-linear variations in their measurement, and typically these variations depend on the position of the scanner with respect to the person. In this paper, the Levenberg-Marquardt method is used as a digital rectifier to adjust this non-linear variation and increases the measurement accuracy of our 3D Rotational Body Scanner. A comparative analysis with other methods such as Polak-Ribire and quasi-Newton method, and the overall system functioning is presented. Finally, computational experiments are conducted to verify the performance of the proposed system and its method uncertainty.

Spatial data acquisition by laser scanning for robot or SHM task

This paper presents through of the principle of laser triangulation a technique to acquisition data from an environment. The prototype can discover obstacles or objects in a unknown environment. Using a light source (laser) and very simple but efficient scanning unit is possible determinate distances and angles of any point on object in environment based in data acquisition by these elements. The most important parameters are: accuracy, functioning speed, range of action, and power requirements; the main characteristics is based in simplicity, versatility and economical accessibility. Fully automatic navigation and monitoring system is able to implement this prototype.

Machine Vision: Approaches and Limitations

Machine vision in its common definition is a possibility of a machine (by sensing means and computer mathematic processing consecutively) to obtain an information about surrounding environment for further analytical treatment. According to this common definition we can unite in a general classification various, sometimes quite different by its principle, technical systems. These classification tables can be represented on the base of two different approaches: 1) practical causes (Soini, 2001) for necessity to “see surrounding environment”, and 2) technical principle and means using for this task solution. According to the common definition any complete Machine vision system combines two components: technical means (or hardware) and information processing mathematics and algorithm (or software). However, the various software analyses is not expedient in view of variety of mathematical methods and their object focused applications in each case (Mordohai & Medioni, 2006); and finally can’t give clearer problem understanding. We are now observing a rapid growth of 3D software and hardware capabilities for mainstream PCs, and 3D graphics accelerator boards with processing capabilities of roughly millions polygons per second are becoming commonplace (Petrov et al., 1998). At the same time, dynamic level-of-detail algorithms—built into standard 3D software packages— offer considerable acceleration of model viewing and progressive loading and transmission of 3D models. Despite the fast growth of computer 3D visualization capabilities, until recently data input technology has remained unchanged. So, in our research for better understanding what is Machine vision, what is its modern state, which practical and technical tasks it decide, and which objective limitations and open problems recently it have, we’ll based on the two mentioned above approaches. In a part of practical reasons, which caused for necessity to develop Machine (or computer) vision concept, can be mentioned: security problems in static/dynamic image analysis in perimeter/volume protection (motion/dangerous object detection); (Chellappa et al., 2005), (Itti & Baldi, 2005) analysis of short/long term deformation of important engineering structures (more commonly known as ‘structural health monitoring’ or SHM); (Athavale et al., 1990), (Allen et al., 2005), (Mallet et al., 2004), (Tyrsa et al., 2004), (Ohno et al., 2002), (Benedetti et al., 2004), (Slob & Hack, 2004), (Stewart & Tsakiri, 2002), (Liwen Dai et al., 2002) O pe n A cc es s D at ab as e w w w .ite ch on lin e. co m

3D laser scanning vision system for autonomous robot navigation

The presented Technical Vision System realizes the principle of dynamic triangulation. This technique is able to resolve in real time a triple task: to detect a presence of significant obstacle in a robots neighborhood; locate its position in a robots field-of-view; obtain in a short time a digital map of the obstacle visible surface with metrological accuracy of coordinates and adjustable step of discretization. Some aspects of theoretical backgrounds, technical design, optical principle, mathematical framework, signal processing, prototype design and experimentation are presented in this paper.

Mobile robot vision system using continuous laser scanning for industrial application

Purpose The purpose of this paper is the presentation and research of a novel robot vision system, which uses laser dynamic triangulation, to determine three-dimensional (3D) coordinates of an observed object. The previously used physical operation principle of discontinuous scanning method is substituted by continuous method. Thereby applications become possible that were previously limited by this discretization. Design/methodology/approach The previously used prototype No. 2, which uses stepping motors to realize a discontinuous laser scan, was substituted by the new developed prototype No. 3, which contains servomotors, to achieve a continuous laser scan. The new prototype possesses only half the width and turns out to be significantly smaller and therefore lighter than the old one. Furthermore, no transmissions are used, which reduce the systematic error of laser positioning and increase the system reliability. Findings By using a continuous laser scan method instead of discontinuous laser scan method, dead zones in the laser scanner field can be eliminated. Thereby, also by changing the physical operation principle, the implementation of applications is allowed, which previously was limited by the fixed step size or by the object distance under observation. By using servomotors instead of stepping motors, also a significant reduced positioning time can be accomplished maintaining the relative positioning error less than 1 per cent. Originality/value The originality is based on the substitution of the physical operation principle of discontinuous by continuous laser scan. The previously used stepping motors discretized the laser scanner field and thereby produced dead zones, where 3D coordinates cannot be detected. These stepping motors were substituted by servomotors to revoke these disadvantages and provide a continuous laser scan, where dead zones in the field of view get eliminated and the step response of the laser scanner accelerated.

Continuous 3D scanning mode using servomotors instead of stepping motors in dynamic laser triangulation

A novel principle of dynamic triangulation with a laser scanner was developed at the institute of engineering UABC. This coordinate measurement method uses stepping motors for positioning a laser in a defined field of view. The present paper describes the substitution of these stepping motors with robust controlled servomotors in open- and closed-loop configuration. This approach converts the discontinuous (i.e. discrete steps) scanning method into a continuous one, to eliminate dead zones in the field of view and to accelerate the step response of the laser scanner.

An approach for dynamic triangulation using servomotors

A novel principle of dynamic triangulation was developed at the institute of engineering UABC. This method of coordinate measurement uses stepping motors for laser positioning and an open loop controlled DC motor for signal detection. The present paper describes an approach for use of servomotors in cascade control loop, optimized with the amplitude optimum in the frequency domain. These approach results in a short rising time of the step response without overshoot. Simulations of the complete system approves the theoretically values.

Frequency measurement method for Mechatronic and Telecommunication applications

A fast frequency measurement method based on the pulse coincidence of two regular independent pulse trains and rational approximations in the number theory is presented. A numeric condition derived from number theory to stop the measurement process is deduced. This measurement method has application in many practical tasks of Mechatronics and Telecommunications where is possible to convert a parameter to frequency, and is necessary to measure fast changes in the parameter. Results of numeric simulation of the frequency measurement process are presented.

Electromechanical 3D Optoelectronic Scanners: Resolution Constraints and Possible Ways of Improvement

Non-Contact optoelectronic 3D measurement is a rapidly growing field. Three-Dimensional Non-Contact Measurement Technologies are very common for research due to multiple practical applications expecting for its benefits. Many fields are using in any way 3D measurements or shape recognition, some of them there are vision assisted assembly in various branches of industry, autonomous mobile robots navigation, structural health monitoring, micro surfaces inspections, precise automated surgery, etc. In this chapter it is expedient to mention and briefly cross-compare the following emerging technologies for 3D measurements: laser scanners, lasers based on conoscopy holography technology and 3D cameras. Laser scanners: Most contemporary non-contact 3D measurement devices are based on laser range scanning. The simplest devices (Fischer, 2007) are based on the laser triangulation technique. This is an active stereoscopic technique in which the distance of the object is computed by means of a directional light source and a video camera. The CCD camera’s 2D array captures the image of surface profile and digitizes all data points along the laser disadvantage of this method is that a single camera collects only a small percentage of the reflected energy. The amount of the collected energy can be drastically increased by trapping the entire reflection cone, thus significantly increasing the precision and reliability of the measurements. Lasers based on Conoscopic Holography technology: Conoscopic Holography is a simple implementation of a particular type of polarized light interference process based on crystal optics. In the basic interference set-up, a point of light is projected onto a diffuse object. This point creates a light point, which diffuses light in every direction. In a conoscopic system, a complete solid angle of the diffused light is analyzed by the system. The measurement

3D Body & Medical Scanners’ Technologies: Methodology and Spatial Discriminations

Medical practitioners have traditionally measured the body’s size and shape by hand to assess health status and guide treatment. Now, 3D body-surface scanners are transforming the ability to accurately measure a person’s body size, shape, and skin-surface area (Treleaven & Wells, 2007) (Boehnen & Flynn, 2005). In recent years, technological advances have enabled diagnostic studies to expose more detailed information about the body’s internal constitution. MRI, CT, ultrasound and X-rays have revolutionized the capability to study physiology and anatomy in vivo and to assist in the diagnosis and monitoring of a multitude of disease states. External measurements of the body are more than necessary. Medical professionals commonly use size and shape to production of prostheses, assess nutritional condition, developmental normality, to analyze the requirements of drug, radiotherapy, and chemotherapy dosages. With the capability to visualize significant structures in great detail, 3D image methods are a valuable resource for the analysis and surgical treatment of many pathologies.