# Stationary 3D Scanning System for IoT Applications
## 3 The Measurement Model  
The described measurement system works on the basis of an analog distance sensor, which measures by means of the emission of an infrared light beam with a wavelength equal to approx. 870 \(\pm\) 70 nm. The frequency of taking single measurements through the sensor, referring to the manufacturer's description in the catalog note, is equal to an estimated value of 50 Hz. The sampling frequency of the analog-to-digital converter should be at least twice as high [14]. The target clock frequency of the 12-bit converter was selected as a value of 54 MHz, which is clearly sufficient for an accurate analysis of the read signal. This frequency directly sets us a conversion time of 0.3 \(\upmu\)s. With the help of the known, constant distance of the geometric center of the convex emitter lens from the geometric center of the rotating table on which the object is placed, a single measurement of the actual distance between the point of emission and the place of reflected light by the object scanned using optical triangulation is made, as shown in Figure 1, which was chosen due to the high speed of digitization [15]. The number 3 shows the point located on the axis of rotation of the scanned object, which should intersect with the axis running through the geometric center of the emitter, which is marked with the number 1, located at point B. The reflected beam is recorded by the receiver, which is marked with the number 2, and then converted into an analog signal in the form of an output voltage in the range of 0.4-3.2 V. Given the angle of incidence of the reflected beam \(\alpha\) and the nominal distance between the emitter and the receiver \(x\) the actual distance \(d\) is calculated. It should be noted that the marked angle is also the angle of incidence of the generated infrared beam, which results from the geometric relationship in \begin{table}
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4 & Application in Industry 4.0 and reverse engineering \\ \hline
5 & Comparable scanning accuracy, but using laser light \\ \hline
6 & Combination of accuracy and reduction in manufacturing costs \\ \hline
7 & Comparison to an issue that has not been further studied \\ \hline
8 & Ability to scan objects of different sizes \\ \hline
11 & A system based on optical triangulation, but with a lower cost of implementation, due to the lack of a digital camera \\ \hline
12 & The similarity of the technology used, as well as the method of acquiring the point cloud \\ \hline
13 & Influence of ambient conditions (lighting), object material and other external disturbances \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison table with the main articles and their contributions. Figure 1: Single-point distance measurement using optical triangulation. the figure above, because a given measurement can be carried out in a setting in which the axis passing through the geometric center of the receiver coincides with the point scanned on the object's profile. In addition, number 4 is the band of possible deviations from the covered part of the surface scanned by infrared light. This area is limited from above and separated by the rangefinder housing. To simplify the calculations and to avoid the lack of additional information relating to a given sensor, the incidence point of the beam with an infinitesimal diameter has been taken from the catalog note. As an average value, the position of the source of the incident infrared beam was taken during the calculations as the geometric center of the sensor lens. Other steps were not taken in this direction, due to the lack of more accurate parameters and data from the manufacturer. During the experimental tests, it was observed that there was no negative effect of the zero position of the sensor head and the placement of the base on which the scanned object is placed. The results shown in the following part of the article illustrate the correctness of the above thesis. The measurement data were additionally filtered using a low-pass filter.