## 3 Results and Discussion  
The non-contact method (LPM) for measuring surface roughness used laser light to capture and analyze the surface profiles, unlike the contact method (SJ-400), which required physical contact. Our experiment analyzed how the color (wavelength) of the laser light in laser profilometry affected the accuracy and reliability of measuring the roughness parameters (Ra, Rz) on glossy surfaces created using laser cutting to aid in selecting the most suitable measurement method for specific finishes. Data from experimental measurements were processed into graphical dependencies enabling a visual analysis and a comparison of the results between reference measurement data and the individual colors of laser light in individual measured sections. A graphic comparison of the measured values of the parameter Ra on individual measuring lines (1, 2, and 3) and sections (A, B, and C) by the non-contact method (LPM) using laser light with different wavelengths versus the reference contact method (SJ-400) is shown in Figure 7.  
When using light with a wavelength of \(\lambda\) = 445 nm, we found that the values of the Ra parameter measured by the non-contact method were 7.5 to 9.6 times higher on Measuring Line 1, 5.7 to 7.8 times higher on Measuring Line 2, and 3.9 to 4.3 times higher on Measuring Line 3 compared with the reference values from the contact roughness gauge. We also observed similar trends for lights with a wavelength of \(\lambda\) = 520 nm and \(\lambda\) = 635 nm, where the values of the parameter Ra were also significantly higher compared with the reference values. These differences in the character of the individual areas of the cross-section of the cutting surface were a consequence of the laser cutting technology itself. Laser cutting can have different effects on the material's surface depending on the cutting parameters, the material's properties, and other factors. Based on the comparison of the Ra parameter values, a significant negative difference between non-contact laser profilometry and the reference contact method was shown. Figure 7: Percentage comparison of the values of the Ra parameter measured by the non-contact method (LPM) using different laser lights versus the reference contact method (100%). From the findings above, we can conclude that the high negative difference in the measured Ra values was caused by the fact that the non-contact laser profilometer evaluated the reflections of laser light from the surface of the sample, which were captured by the CMOS camera and subsequently evaluated by the LPM software ([[http://testsite.kvant.sk/solutions/lpm/](http://testsite.kvant.sk/solutions/lpm/)]([http://testsite.kvant.sk/solutions/lpm/](http://testsite.kvant.sk/solutions/lpm/)), accessed on 11 March 2024) as increased surface roughness, i.e., a measurement error that can be explained as the unwanted glare in the camera sensor. These findings indicate that the non-contact method of measuring the roughness of glossy surfaces is inappropriate and not reliable for measuring the Ra parameter. The contact method using the SJ-400 roughness meter is more objective and provides more realistic results for the Ra parameter. Studies by [PERSON] et al. [30] and [PERSON] et al. [6] reported that a non-contact laser profilometer can evaluate reflections as increased surface roughness. On the basis of our measurements, we found that the value of the Ra parameter was, however, several times higher than the reference value. Therefore, we do not agree with the statement that it is only an increased value of Ra. It is important to emphasize that our research was conducted on a different material sample and therefore may have led to possible different results.