Optical inspection system for simultaneously measuring thicknesses and refractive indexes of multilayered transparent substrates

Chien-Sheng Liu; Chang-Yu Jen

doi:10.1117/12.2620056

20 May 2022 Optical inspection system for simultaneously measuring thicknesses and refractive indexes of multilayered transparent substrates

Chien-Sheng Liu, Chang-Yu Jen

Author Affiliations +

Proceedings Volume 12137, Optics and Photonics for Advanced Dimensional Metrology II; 121370O (2022) https://doi.org/10.1117/12.2620056
Event: SPIE Photonics Europe, 2022, Strasbourg, France

Conference Poster

Abstract

In this study, an inspection system that can simultaneously measure the thicknesses and refractive index of transparent substrates has been proposed. The proposed inspection system consists of two sub-systems: the transmitted system and the confocal system. When measuring the samples, the transmitted system will compare the spot position before and after placing the samples into the system. To reduce the image processing difficulty and deviation that caused by the transmitted system, we use a slit to transform the shape of spot into rectangle. On the other hand, the confocal system will scan the samples from the top to bottom by moving an objective lens with a precision slider that can change the focus position. We can therefore plot the chart of confocal intensity signal curve to estimate the distance between the peaks that caused by laser focus on the surface of samples. By substituting the measured data of the two sub-systems into the proposed mathematical model, the thicknesses and refractive index of the samples can measured simultaneously. By measuring the thicknesses and refractive index of transparent substrates beyond and below the biological sample, it provides the basis for a possible biological auto-focusing microscope in the future. To prove the system feasibility, we simulated the whole system by optical simulation software Zemax to measure different samples with different thicknesses and materials. The simulation results show that the system deviations of thicknesses and refractive indexes are about 0.005%~3.128% and 1.643%~5.116%, respectively.

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Chien-Sheng Liu and Chang-Yu Jen "Optical inspection system for simultaneously measuring thicknesses and refractive indexes of multilayered transparent substrates", Proc. SPIE 12137, Optics and Photonics for Advanced Dimensional Metrology II, 121370O (20 May 2022); https://doi.org/10.1117/12.2620056

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