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Technical Section Phone: 516-328-3970 www.technocnc.com  17 machine positioning the scanner usually supplies the travel to collect the X and Y coordinates. Another subcategory of noncontact type of scanner is structured light types. These scanners work with a specific varying intensity of light and multiple  images  of  the  object  from  known  positions.  A mathematical algorithm is then used to create a surface with  the  measured  amount  of  reflectivity.  This  basically recreates the 3D visible surface of the object. The speed and accuracy of the scanner varies greatly depending on the model and drive system of the CNC machine. In addition, the  scanners  share  the  same  attributes  from  one manufacturer to another. Types of Laser Scanners There  are  a  number  of  different  types  of  laser displacement scanners, each offering advantages in certain applications. Interferometry is probably the most accurate but requires the greatest precision in the equipment and the surfaces to be measured. Triangulation looks at the angle of reflection off the target surface and is generally very inexpensive but is limited by the inclination angle of the surface to  be  measured.  Steeper  angles  produce  very erratic results. Dynamic focusing uses a system to adjust the focus of a camera to determine the distance. This method requires moving parts and is thus limited by its speed and cost of equipment. The  Conoscope  method,  used  by  the  Techno laser scanner, uses polarized light and holographic methods to determine the distance to the reflecting surface. Because only a single beam is used, the angle of the surface does not affect the results and even measurements in “deep holes” can be taken. What to Scan and What to Scan with The different types of scanners are typically suited for different  types  of  applications.  The  contact  process  is usually more time consuming but can also be more efficient for smooth engineered types of surfaces such as the fender of a car. Because of the contact, specific points can be digitized to get the features of the surface, such as an edge or cusp or hole. This allows for the features to be quickly and accurately recognized and digitized. Another advantage of contact scanner arms is that the surface generation is a more  simple  process.  In  most  cases,  the  points  being collected are directly used for creating splines or features in  the  software.  There  is  generally  little  filtering  that  is required. The noncontact types of scanners are usually faster at collecting large numbers of data points but they typically are designed to gather points over a grid surface with a specific  spacing  along  the  X  and  Y  axes.  This  process collects what is called a “point cloud” with a greater number of XYZ coordinate pairs. This approach is better suited for collecting data off very detailed surfaces which might be found on hand-carved objects such as furniture or coins. The drawback to this approach is that the features such as the cusps, edges and sharp corners might not be captured completely in the grid being used to collect the data unless the grid is relatively fine and then a great number of points have to be collected. Collecting vast amounts of data often creates processing problems. Remember that the number of data points increases geometrically as the grid gets finer.