Abstract. The problem of measuring the thickness of transparent low-scattering and low-absorbing layers of inorganic coatings and films in the range from 0.1 mm to 0.6 mm in real time with a relative measurement error of less than 10% is considered. The measurements are performed using a combination of two methods – laser interferometry and modified triangulation. The subject of the study is to determine the set of parameters necessary for measuring the thickness by the specified optical methods; the purpose of the study is to develop a way to measure the thickness by the combined method so that the refractive index of the sample under study is absent in the set of necessary parameters. The principle of operation when using the combined method is presented and the search for optimal parameters of the measuring installation is carried out, which allows to reduce the measurement error to 5% while reducing the information content of the measurement by 3 times only. The main advantage of the proposed approach is that information on the numerical value of the refractive index of the measured layer is not required to determine the thickness by the combined method.

Keywords: interferometry, modified laser triangulation, thickness measurement, refractive index, combination of measurement methods

References:

1. Sorkio A., Koch L., Koivusalo L., Deiwick A., Miettinen S., Chichkov B., Skottman H. Biomaterials, 2018, vol. 171, рр. 57–71.
2. Green D.G., Frueh B.R., Shapiro J.M. Journal of the Optical Society of America, 1975, no. 2(65), pp. 119–123.
3. Priezzhev A.V., Tuchin V.V., Shubochkin L.P. Lazernaya diagnostika v biologii i meditsine (Laser Diagnostics in Biology and Medicine), Moscow, 1989, 240 р. (in Russ.)
4. Adamov A.A., Baranov M.S., Khramov V.N. Proc. SPIE 11066, Saratov Fall Meeting, 2018: Laser Physics, Photonic Technologies, and Molecular Modeling, 3 June 2019, article ID 1106608, DOI: 10.1117/12.2521424.
5. Adamov A.A., Khramov V.N. Mathematical Physics and Computer Simulation, 2017, no. 4(20), pp. 83–94. (in Russ.)
6. Adamov A.A., Khramov V.N. Proc. SPIE 10717, Saratov Fall Meeting 2017: Laser Physics and Photonics XVIII; Computational Biophysics and Analysis of Biomedical Data IV, 26 April 2018, article ID 1071703, DOI: 10.1117/12.2314820
7. Adamov A.A., Baranov M.S., Khramov V.N., Abdrakhmanov V.L., Golubev A.V., Chechetkin I.A. International Conference PhysicA.SPb/2018, IOP Conf. Series: Journal of Physics, Conf. Series, 2018, vol. 1135, article ID 012049, DOI:10.1088/1742-6596/1135/1/012049.
8. Adamov A.A., Baranov M.S., Khramov V.N. Proc. SPIE 11066, Saratov Fall Meeting 2018, Laser Physics, Photonic Technologies, and Molecular Modeling, 3 June 2019, article ID 1106607, DOI:10.1117/12.2521419.
9. Adamov A.A., Khramov V.N. Journal of Physics: Conf. Series, 2019, no. 2(1368), article ID 022001, DOI:10.1088/1742-6596/1368/2/022001.
10. Patent RU 2018620590, Baza dannykh Izmeriteli tolshchin tonkikh prozrachnykh tkaney i plenok (Database Gauges of thicknesses of thin transparent fabrics and films), A.A. Adamov, M.S. Baranov, V.N. Khramov, V.L. Abdrakhmanov, A.V. Golubev, I.A. Chechetkin, Priority 21.03.2018, Published 20.04.2018, Bulletin 4. (in Russ.)
11. Lun-Kai Cheng, Toet P.M. Opto-Mechanical Fiber Optic Sensors, Butterworth-Heinemann, 2018, рр. 175–209, DOI.org/10.1016/B978-0-12-803131-5.00007-6.
12. Coelho J.M.P., Nespereira M.C., Abreu M., and Rebordão J.M. Photonic Sensors, 2013, no. 1(3), pp. 67–73.
13. Adamov A.A., Baranov M.S., Khramov V.N. Scientific and Technical Journal of Information Technologies, Mechanics and Optics, 2018, no. 3(18), pp. 356–362, DOI: 10.17586/2226-1494-2018-18-3-356-362. (in Russ.)
14. Patent RU RU179826U1, Lazernyy triangulyatsionnyy izmeritel' tolshchiny rogovitsy i ostatochnykh rogovichnykh sloyev glaza (Laser Triangulation Measurer for Thickness of the Corneal and Residual Corneral Eye Layers), A.A. Adamov, M.S. Baranov, V.N. Khramov, V.L. Abdrakhmanov, A.V. Golubev, I.A. Chechetkin, Priority 2017-11-07, Published 2018-05-24, Bulletin (in Russ.)
15. https://stormoff.ru/mediacenter/articles/article_66. (in Russ.)
16. Patent RU2017664237, Programmnoye sredstvo obrabotki izobrazheniy eksperimental'nykh dannykh dlya otsenki rasstoyaniya mezhdu svetovymi metkami (Experimental Data Image Processing Software for Estimating the Distance between Light Marks), A.A. Adamov, V.L. Abdrakhmanov, A.V. Golubev, I.A. Chechetkin, Priority 21.11.2017, Published 20.12.2017, Bulletin 12. (in Russ.)
17. Patent RU2018666945, Programma obrabotki fotoizobrazheniy eksperimental'nykh interferogramm dlya opredeleniya znacheniya shiriny i ugla naklona interferentsionnykh polos (Program for Processing Photographic Images of Experimental Interferograms to Determine the Value of the Width and Angle of Inclination of Interference Fringes), A.A. Adamov, Priority 21.12.2018, Published 20.01.2019. (in Russ.)
18. Adamov A.A., Khramov V.N. Physics, Engineering and Technologies for Biomedicine, The 4th International Symposium and International School for Young Scientists, October 26–30, 2019, Moscow, 2019, рр. 90–91.
19. Kirillovsky V.K., Tochilina T.V. Opticheskiye izmereniya. Chast' 1. Vvedeniye i obshchiye voprosy. Tochnost' opticheskikh izmereniy (Optical Measurements. Part 1. Introduction and General Questions. Accuracy of Optical Measurements), St. Petersburg, 2017, 49 р. (in Russ.)