Non-Contact Roughness Measurement in Sub-Micron Range by Considering Depolarization Effects

Abstract

The characteristics of a surface, particularly the roughness, play an important role in different fields of the industry and have to be considered to ensure quality standards. Currently, there are numerous sophisticated methods for measuring surface roughness but plenty of them cause long-term damage because they are in contact with the sample. This article presents a non-contact method to accurately determine small surface roughnesses resulting from the consideration of the depolarization effects caused by the rough surface. This technique can be applied as an extension in various roughness measurements and improves the approach of Chandley’s technique, which does not take into account the depolarization of the light scattered by the sample. The experimental setup and the measurements are easy to perform. The essential component is a quarter wave plate, which is incorporated into a Michelson interferometer. With the resulting two different contrasts and the recorded intensities of the sample and the reference mirror, the surface roughness can be estimated straightforwardly. This article details the theoretical approach, followed by the experimental results and the corresponding uncertainties. The experimental results are compared with Chandley’s method. In order to have reference roughness values of the samples, measurements with a stylus profilometer and with a confocal microscope are performed and compared.

Distinguishing Drones from Birds in a UAV Searching Laser Scanner Based on Echo Depolarization Measurement

“…Identification of surface type, its microscopic or macroscopic parameters, based on reflected light polarization state measurements have been reported many times [30][31][32][33][34][35][36][37][38][39][40][41]. Most of the research in this field however deals with laboratory methods based on full Stokes vector and Mueller matrix analysis.…”

Extension and Limits of Depolarization-Fringe Contrast Roughness Method in Sub-Micron Domain

“…Thus, the consideration of polarization in approaching the problem becomes important, sometimes even essential, to obtain a limited (or bounded) value of roughness. Bearing this fact in mind, in the context of roughness, an interferometric procedure to improve roughness measurements in intervals of tens of nanometers is proposed [ 21 ]. In order to succinctly explain the basis of the method, we can describe it as follows.…”

“…Considering the polarization variation of the reflected light from the sample, different contrasts and of the respective interference patterns on both sides A and B will be obtained. By measuring these contrasts of the interference fringes of both parts, the roughness of the sample may be more accurately calculated using the following formula [ 21 ]: where represents the sum of the intensities x and y , is the intensity from the mirror, and is the wavelength of the radiation used. This formula corresponds to the root mean square (RMS) roughness [ 30 ]: …”

“…In a previous paper [ 21 ], we demonstrated an improvement of the roughness measurement up to approximately , by considering the depolarization of the scattered light from a rough surface when employing the fringe contrast method [ 22 ]. In this context, this article aimed to extend the applicability of the technique to samples with higher roughness but in the submicrometer range by changing the wavelength of the radiation used.…”

Intensity Simulation of a Fourier Transform Infrared Spectrometer

“…Comparing the corrected spectrum with the input spectrum, we can see that the brightness temperature errors have a magnitude of 10 −3 K, and this fully proves the reliability and rationality of the whole simulation process. flux and multi-channels, has been developed in many fields, such as military reconnaissance [15,16], astrophysics research [17], geological resource exploration [18], and atmospheric monitoring [19][20][21][22][23][24][25].Interferogram is not only the direct result of the Michelson interferometer, but it is also the basis for obtaining the spectrum of the light source.FY-4A GIIRS is the first space-borne interferometer in geostationary orbit, and it measures the three-dimensional atmospheric structure through the interference of split light beams. Based on the FY-4A's success, the FY-4B satellite will be launched in 2020.…”