A technique for intrinsic and extrinsic calibration of a laser triangulation sensor (LTS) integrated in an articulated arm coordinate measuring machine (AACMM) is presented in this paper. After applying a novel approach to the AACMM kinematic parameter identification problem, by means of a single calibration gauge object, a one-step calibration method to obtain both intrinsic―laser plane, CCD sensor and camera geometry―and extrinsic parameters related to the AACMM main frame has been developed. This allows the integration of LTS and AACMM mathematical models without the need of additional optimization methods after the prior sensor calibration, usually done in a coordinate measuring machine (CMM) before the assembly of the sensor in the arm. The experimental tests results for accuracy and repeatability show the suitable performance of this technique, resulting in a reliable, quick and friendly calibration method for the AACMM final user. The presented method is also valid for sensor integration in robot arms and CMMs.

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Modelling and Calibration Technique of Laser Triangulation Sensors for Integration in Robot Arms and Articulated Arm Coordinate Measuring Machines

Recent developments in optical communication systems have presented an emerging need for scanning and tracking dynamic targets with high accuracy. Unfortunately, conventional scanners have difficulty supplying either sufficient vision information or high scanning resolution because of the fixed optical parameters and optomechanical structure. This paper introduces a novel cascaded double-prism scanner that combines the two scanning modes of rotating and titling motions into a nested device. The analysis results show that both the vertical field angle range and the horizontal field range of the coarse scanning are no less than ±10°, with the scanning accuracy superior to 50 μrad, while the vertical field angle range and the horizontal field range of the fine scanning are, respectively, no less than 2500 μrad and 1200 μrad, with the scanning accuracy superior to 1 μrad. The scanning method not only meets the requirements of collaboratively steering the beam deviation in a large range with high accuracy but also can obtain a variety of scanning modes and trajectories, which has important engineering significance for the solution of steering a fine beam to track and position a dynamical target.

Laser coarse–fine coupling scanning method by steering double prisms

This Extended Technical Note shows that the final accuracy level of reverse engineered surfaces depends on scanning distance and scanning angle of the laser beam, hence it also depends on the morphology of the scanned objects. On scanning strongly curved objects, such as the ones with free form surfaces, the distance and impact angle of the laser beam are changing continuously during the scanning process. On the basis of these, two critical parameters are specified for the design model, which make it possible to predict these two factors in advance, depending on the morphology of the scanned object. First, a mathematical-statistical design model of the scanning process is generated, which relies on ANOVA (analysis of variance) and DOE (design of experiments). In the next step, a fitness function is optimized by the genetic algorithm (GA) program. This optimization improves the accuracy of the final scanned surfaces, in terms of the minimum standard deviation values of reverse engineered 3D surface model. The proposed approach was confirmed in a case study, which is presented at the end of this Technical Note.

Identification and optimization of key process parameters in noncontact laser scanning for reverse engineering

We report the design of a novel laser line-triangulation laryngoscope for the quantitative visualization of the three- dimensional movements of human vocal folds during phonation. This is the first successful in vivo recording of the three-dimensional move- ments of human vocal folds in absolute values. Triangulation images of the vocal folds are recorded at the rate of 4000 fps with a reso- lution of 256256 pixels. A special image-processing algorithm is developed to precisely follow the subpixel movements of the laser line image. Vibration profiles in both horizontal and vertical direc- tions are calibrated and measured in absolute SI units with a reso- lution of ±50 m. We also present a movie showing the vocal folds dynamics in vertical cross section. © 2008 Society of Photo-Optical Instrumenta-

/pdf/new-laryngoscope-for-quantitative-high-speed-imaging-of-3kyslkbomw.pdf

New laryngoscope for quantitative high-speed imaging of human vocal folds vibration in the horizontal and vertical direction

In presented paper a design model is developed which is used to find an optimal design space in order to improve precision and accuracy of reversed 3D models. Significant parameters and their mutual effects in scanning process are recognized with the help of Design of Experiments (DOE) principles, and in second step recognized significant parameters are also optimized using the RSM (Response Surface Methodology). Back propagated neural network is used for prediction of response factors whose input variables are not possible to set during experimentation due to the nature of the scan device. With neural network (NN) predicted response-design data, the Analysis of Variance (ANOVA) test was performed. On a basis of significant parameters the analytical model is established, which enables prediction and optimization of critical scan parameters, according to the prescribed standard deviation (abberation) of analysed 3D CAD models. After getting knowledge about the relationships between significant parameters it is possible to predict and optimize them using a model established in the RSM on a basis of D-optimal Design of Experiment test (DOE). At the end also the precision assessment of predicted response factors by DOE approach and by neural network approach is done and results are beeing compared.

http://www.wseas.us/e-library/conferences/2007athensel/papers/564-312.pdf

M.Y Nie

Papers

A study of the precision factors of large-scale object surface profile laser scanning measurement