# The Influence of Filtration on the Results of Measurements Made with Optical Coordinate Systems
## 1 Introduction  
In optical measurements, filtration is used. It allows the measurement to be optimized in a sense by bypassing the edge areas that were created as a result of material flow during the manufacturing process. Filtration is one of the methods that allows for obtaining results by cutting off this so-called noise. Many authors have discussed the topic of filtration in measurements using coordinate machines, as well as in 3D scanning measurements. They note that there is no single method suitable for all measurement tasks; therefore, in practice, several filtration methods are combined in order to solve problems [1, 2, 3]. The influence of filtration in optical measurements is rarely addressed in the literature, because the issues of contour filtration and contour analysis in optical measurements in general are relatively new. [PERSON], in [4], draws attention to the importance of removing noise and outliers from a point cloud while preserving its features, especially its fine details. Although there are several existing studies on point cloud filtering, it is believed that filtering the raw point cloud, which is a key step in the point cloud processing process, remains a difficult task. In another publication, [PERSON] [5] describes a method for filtering a point cloud, which is used to estimate the shape deviation of the object under study. This type of calculation on the original noisy laser scanning data gives large overestimations of these parameters. Filtering is a process widely used in signal and image processing that aims to reduce the influence of noise in the data and, in other cases, to sharpen edges [6]. Filtration isa tool that can affect the results obtained. It depends on the user of the optical system, who defines the filtration value during measurement. Other factors, such as errors from the systems used, also affect the results. These errors can come from the device design itself and from the optical systems used. Some optical defects, such as aberrations, cause image distortions. These include astigmatism, distortion, field curvature, and chromatic and spherical aberration [7; 8; 9; 10]. Some of them depend largely on the properties of the material from which they were made, and some depend on the manufacturing process. No lens--and, therefore, no optical machine--is perfect. Their manufacturing processes are accompanied by variability; this has an impact on the quality of the manufactured products and indirectly on the size of errors from the optics. Considering the fact that filtration is a very important aspect and its selection should not be made ad hoc, the authors decided to conduct test studies on a selected part used in production at Lear Corporation. These studies aimed to help determine the validity of using filtration in optical measurements, as well as its appropriate selection. The selection of the \"Dust\" filter is a relatively new subject. After consulting the machine supplier, the authors obtained information that the issue of filtration had not been studied in sufficient detail. Users of machines equipped with the Werth Zoom sensor receive information about the possibility of using filtration during training. However, they do not receive a clear declaration of what filter values are safe for the user. If we use a filter of 50 or greater, when we measure a regular hexagon, we will obtain a circle, which is not true. Safety in this context means a filter value that will not significantly affect the measurement result. Customer requirements for cars and their equipment are constantly increasing. In addition to safety, special attention is paid to travel comfort. To this end, car manufacturers are trying to implement newer and newer solutions that allow them to present their products as more attractive compared to the competition. Lear Corporation is a supplier of seat comfort systems for premium-class cars. One of the elements of seat comfort is the seat adjustment system. There are several elements in this system, but one of the most important is the valve.