# The Influence of Filtration on the Results of Measurements Made with Optical Coordinate Systems
## 2 Materials and Methods  
The Werth Scope Check multisensor machine was used for these measurements (Werth Messtechnik GmbH, Giessen, Germany). Multisensory machines use different sensors, which actually increases the range of their measurement capabilities. They combine the advantages of tactile and contactless measuring systems. The principle of operation and the benefits resulting from the use of such a solution are described in [11; 12; 13]. Examples of the use of multisensory coordinate measuring machines in industrial practice are described in [14]. In systems of this type, contact measurements can be used to determine reference points or to measure dimensions with narrow tolerance zones, while optical methods are used to inspect small products and to accelerate measurement processes [15]. A sensor based on image analysis was used in this study of the influence of filtration. The machine  
Figure 2: Actuator—the detail under analysis (hinge thickness) is marked with a red circle. used for the measurements uses variable-focal-length optics (Werth Zoom) with an optical magnification range from 0.68 to 6.8 and a variable working distance. A diagram of the variable working distance is shown in Figure 3, while a view of the Werth Zoom optical sensor used is shown in Figure 4 [16]. For this sensor, the manufacturer specifies the permissible sampling errors according to VDI/VDE 2617 part 6.2, as follows:  
* For measurement without the participation of drives, i.e., measurement in the image (on static):
* PS/PF 2D xy (OS): 1.1 \(\upmu\)m.
* For measurement with travel, i.e., with the participation of the machine drives (on transmission):
* PS/PF 1 Dxy (OT): 1.1 \(\upmu\)m;
* PS/PF 2 Dxy (OT): 1.5 \(\upmu\)m;
* PS/PF 1 Dz (OT): 2.5 \(\upmu\)m.  
Error studies were performed for measurements using the standard window and the highest magnification without an additional lens. In the above notation, PS denotes the error in the measurement of a dimension (Probing Size), for example, the diameter of a reference circle, and PF (Probing Form) denotes the deviation in the shape of the same circle. Figure 3: Views of the image acquisition sensor design: (**A**) standard zoom with a fixed working distance; lighting types: (**a**)—transmitted light, (**b**)—bright field incident light integrated into the lens, (**c**)—dark field incident light ring, adjustable height for lenses with a fixed working distance, (**d**)—dark field incident light ring in combination with Werth Zoom; (**B**) Werth Zoom with a variable working distance. A1 and A5 represent different working distances. The aim of this research using filtration is to assess the effect of the filter size on the measurement result. The use of an appropriate filter, correct interpretation, and the final result depend on the person measuring, who determines the size of the filter used in the measurements. In order to address the emerging measurement problems on the part of both the supplier and the customer, research for various filtration applications was started. For the conducted research, different filter sizes were used with the values 0, 5, 10, and 20. The filters used in the measurements are called \"Dust\" in the program. A filter with a value of \"0\" does not affect the measurement result, because the edge of the measured element is outlined in accordance with the actual state. With filters greater than zero, this outline is increasingly deeper into the material. Increasing the filter means that visible flashes and spouts are not taken into account during the measurement. A view of the change in the edge of the measured object using appropriate filter sizes is shown in Figure 5. As can be seen in the figure, filters with values of \"10\" and \"20\" already have a visible effect, but how this effect translates into the measured value is analyzed in this article. What filters should be used so as not to distort reality? This question also appears in the discussion and analysis of this problem.